U.S. patent application number 11/562931 was filed with the patent office on 2007-07-05 for medical device with coating that promotes endothelial cell adherence.
This patent application is currently assigned to OrbusNeich Medical, Inc.. Invention is credited to Robert John JR. Cottone, Michael John Bradley Kutryk, Stephen Maxwell Rowland.
Application Number | 20070156232 11/562931 |
Document ID | / |
Family ID | 26885401 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070156232 |
Kind Code |
A1 |
Kutryk; Michael John Bradley ;
et al. |
July 5, 2007 |
Medical Device with Coating that Promotes Endothelial Cell
Adherence
Abstract
This invention provides compositions and methods for producing a
medical device coated with a matrix and an antibody which reacts
with an endothelial cell antigen. The matrix coating the medical
device may be composed of synthetic material, such as polyurethane,
poly-L-lactic acid, cellulose ester or polyethylene glycol. In
another embodiment, the matrix is composed of naturally occurring
materials, such as collagen, fibrin, elastin, amorphous carbon. In
a third embodiment, the matrix may be composed of fillerenes. The
fullerenes range from about C60 to about C100. The medical device
may be a stent or a synthetic graft. The antibodies promote
adherence of eadothelial cells on the medical device. The
antibodies may be mixed with the matrix or covalently tethered
through a linker molecule to the matrix. Following adherence to the
medical device, the endothelial cells differentiate and proliferate
on the medical device. The antibodies may be different types of
monoclonal antibodies. Methods of preparing such composition and
methods of treating a mammal with atherosclerosis or other types of
vessel obstruction are disclosed. By facilitating adherence of
endothelial cells to the surface of the medical device, the methods
and compositions of this invention will decrease the incidence of
restenosis as well as other thromboembolic complications resulting
from implantation of medical devices.
Inventors: |
Kutryk; Michael John Bradley;
(Toronto, CA) ; Cottone; Robert John JR.; (Davie,
FL) ; Rowland; Stephen Maxwell; (Miami, FL) |
Correspondence
Address: |
KELLEY DRYE & WARREN LLP
400 ATLANTIC STREET
13TH FLOOR
STAMFORD
CT
06901
US
|
Assignee: |
OrbusNeich Medical, Inc.
Fort Lauderdale
FL
|
Family ID: |
26885401 |
Appl. No.: |
11/562931 |
Filed: |
November 22, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10832106 |
Apr 26, 2004 |
|
|
|
11562931 |
Nov 22, 2006 |
|
|
|
09808867 |
Mar 15, 2001 |
7037332 |
|
|
10832106 |
Apr 26, 2004 |
|
|
|
60189674 |
Mar 15, 2000 |
|
|
|
60201789 |
May 4, 2000 |
|
|
|
Current U.S.
Class: |
623/1.41 ;
435/402; 623/1.46 |
Current CPC
Class: |
A61L 27/08 20130101;
A61P 9/10 20180101; C12N 2510/00 20130101; A61K 38/39 20130101;
A61F 2/07 20130101; A61L 31/148 20130101; A61K 38/363 20130101;
C07K 16/2896 20130101; A61L 27/54 20130101; A61L 31/022 20130101;
A61K 39/39558 20130101; A61K 2300/00 20130101; A61L 31/16 20130101;
A61K 2300/00 20130101; A61K 2300/00 20130101; A61F 2/2412 20130101;
A61F 2/82 20130101; A61L 31/047 20130101; A61L 27/227 20130101;
A61L 2300/422 20130101; A61L 31/125 20130101; A61K 38/363 20130101;
C12N 5/0692 20130101; A61L 31/10 20130101; A61L 2300/256 20130101;
B82Y 30/00 20130101; A61L 2300/606 20130101; C07K 2317/55 20130101;
A61L 27/44 20130101; A61K 39/39558 20130101; A61L 31/084 20130101;
A61L 2300/432 20130101; A61L 29/16 20130101; A61L 2420/04 20130101;
A61L 27/303 20130101; A61L 29/103 20130101; A61K 38/39 20130101;
A61L 29/126 20130101; A61L 2300/416 20130101 |
Class at
Publication: |
623/001.41 ;
623/001.46; 435/402 |
International
Class: |
A61F 2/06 20060101
A61F002/06; C12N 5/08 20060101 C12N005/08 |
Claims
1-51. (canceled)
52. A method for forming an endothelial cell layer in vivo,
comprising administering to a patient at a site in need thereof a
ligand for stem cells or progenitor cells, wherein circulating stem
cells or progenitor cells are captured by the ligand.
53. The method of claim 52, wherein the ligand is immobilized to a
matrix material at the site of implantation.
54. The method of claim 52, wherein the ligand is incorporated into
a matrix material or at the site of implantation.
55. The method of claim 52, wherein the ligand is released from
genetically engineered cells at the site of implantantion.
56. The method of claim 52, wherein the ligand specifically binds
to stem cells or progenitor cells.
57. The method of claim 52, further comprising providing molecules
inducing proliferation or differentiation of stem cells or
progenitor cells.
58. The method of claim 52, wherein the matrix is formed of a
natural or synthetic polymer.
59. The method of claim 53, wherein the matrix is a fibrous
mesh.
60. The method of claim 53, wherein the ligands are tethered to the
matrix.
61. The method of claim 52, wherein the ligand is an antibody,
antibody fragment or combination thereof.
62. The method of claim 61, wherein the antibody, antibody fragment
or combination thereof is selected from the group consisting of
antibodies against CD45, CD34, CD31, Flk-1, Tie-2, and
E-selectin.
63. The method of claim 60, wherein the ligand and the matrix are
part of a coating on a medical device.
64. The method of claim 63, wherein the medical device comprises a
stent or synthetic graft.
65. The method of claim 52, wherein the circulating stem or
progenitor cells are endothelial cells transfected with a mammalian
expression vector.
66. The method of claim 65, wherein the expression vector comprises
one or more cloned genes encoding a protein selected from the group
consisting of platelet derived growth factor (PDGF), fibroblast
growth factor (FGF), and nitric oxide synthase.
Description
[0001] This application claims the benefit of U.S. Provisional
Application Nos. 60/189,674 filed Mar. 15, 2000 and 60/201,789
filed May 4, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of medical
devices implanted in vessels within the body. More particularly,
the present invention relates to stents or synthetic grafts
implanted in blood vessels that incorporate a matrix which promotes
adherence of endothelial cells to the stent or synthetic graft.
BACKGROUND OF THE INVENTION
[0003] Atherosclerosis is one of the leading causes of death and
disability in the world. Atherosclerosis involves the deposition of
fatty plaques on the lumenal surface of arteries. The deposition of
fatty plaques on the lumenal surface of the artery causes narrowing
of the cross-sectional area of the artery. Ultimately, this
deposition blocks blood flow distal to the lesion causing ischemic
damage to the tissues supplied by the artery.
[0004] Coronary arteries supply the heart with blood. Coronary
artery atherosclerosis disease (CAD) is the most common, serious,
chronic, life-threatening illness in the United States, affecting
more than 11 million persons. The social and economic costs of
coronary atherosclerosis vastly exceed that of most other diseases.
Narrowing of the coronary artery lumen causes destruction of heart
muscle resulting first in angina, followed by myocardial infarction
and finally death. There are over 1.5 million myocardial
infarctions in the United States each year. Six hundred thousand
(or 40%) of those patients suffer an acute myocardial infarction
and more than three hundred thousand of those patients die before
reaching the hospital. (Harrison's Principles of Internal Medicine,
14.sup.th Edition, 1998).
[0005] CAD can be treated using percutaneous translumenal coronary
balloon angioplasty (PTCA). More than 400,000 PTCA procedures are
performed each year in the United States. In PTCA, a balloon
catheter is inserted into a peripheral artery and threaded through
the arterial system into the blocked coronary artery. The balloon
is then inflated, the artery stretched, and the obstructing fatty
plaque flattened, thereby increasing the cross-sectional flow of
blood through the affected artery. The therapy, however, does not
usually result in a permanent opening of the affected coronary
artery. As many as 50% of the patients who are treated by PTCA
require a repeat procedure within six months to correct a
re-narrowing of the coronary artery. Medically, this re-narrowing
of the artery after treatment by PTCA is called restenosis.
Acutely, restenosis involves recoil and shrinkage of the vessel.
Subsequently, recoil and shrinkage of the vessel are followed by
proliferation of medial smooth muscle cells in response to injury
of the artery from PTCA. In part, proliferation of smooth muscle
cells is mediated by release of various inflammatory factors from
the injured area including thromboxane A.sub.2, platelet derived
growth factor (PDGF) and fibroblast growth factor FGF). A number of
different techniques have been used to overcome the problem of
restenosis, including treatment of patients with various
pharmacological agents or mechanically holding the artery open with
a stent. (Harrison's Principles of Internal Medicine, 14.sup.th
Edition, 1998).
[0006] Of the various procedures used to overcome restenosis,
stents have proven to be the most effective. Stents are metal
scaffolds that are positioned in the diseased vessel segment to
create a normal vessel lumen. Placement of the stent in the
affected arterial segment prevents recoil and subsequent closing of
the artery. Stents can also prevent local dissection of the artery
along the medial layer of the artery. By maintaining a larger lumen
than that created using PTCA alone, stents reduce restenosis by as
much as 30%. Despite their success, stents have not eliminated
restenosis entirely. (Suryapranata et al. 1998. Randomized
comparison of coronary stenting with balloon angioplasty in
selected patients with acute myocardial infarction. Circulation
97:2502-2502).
[0007] Narrowing of the arteries can occur in vessels other than
the coronary arteries, including the aortoiliac, infrainguinal,
distal profinda femoris, distal popliteal, tibial, subclavian and
mesenteric arteries. The prevalence of peripheral artery
atherosclerosis disease (PAD) depends on the particular anatomic
site affected as well as the criteria used for diagnosis of the
occlusion. Traditionally, physicians have used the test of
intermittent claudication to determine whether PAD is present.
However, this measure may vastly underestimate the actual incidence
of the disease in the population. Rates of PAD appear to vary with
age, with an increasing incidence of PAD in older individuals. Data
from the National Hospital Discharge Survey estimate that every
year, 55,000 men and 44,000 women had a first-listed diagnosis of
chronic PAD and 60,000 men and 50,000 women had a first-listed
diagnosis of acute PAD. Ninety-one percent of the acute PAD cases
involved the lower extremity. The prevalence of comorbid CAD in
patients with PAD can exceed 50%. In addition, there is an
increased prevalence of cerebrovascular disease among patients with
PAD.
[0008] PAD can be treated using percutaneous translumenal balloon
angioplasty (PTA). The use of stents in conjunction with PTA
decreases the incidence of restenosis. However, the post-operative
results obtained with medical devices such as stents do not match
the results obtained using standard operative revascularization
procedures, i.e., those using a venous or prosthetic bypass
material. (Principles of Surgery, Schwartz et al. eds., Chapter 20,
Arterial Disease, 7.sup.th Edition, McGraw-Hill Health Professions
Division, New York 1999).
[0009] Preferably, PAD is treated using bypass procedures where the
blocked section of the artery is bypassed using a graft.
(Principles of Surgery, Schwartz et al. eds., Chapter 20, Arteral
Disease, 7.sup.th Edition, McGraw-Hill Health Professions Division,
New York 1999). The graft can consist of an autologous venous
segment such as the saphenous vein or a synthetic graft such as one
made of polyester, polytetrafluoroethylene (PTFE), or expanded
polytetrafluoroethylene (ePTFE). The post-operative patency rates
depend on a number of different factors, including the lumenal
dimensions of the bypass graft, the type of synthetic material used
for the graft and the site of outflow. Restenosis and thrombosis,
however, remain significant problems even with the use of bypass
grafts. For example, the patency of infrainguinal bypass procedures
at 3 years using an ePTFE bypass graft is 54% for a
femoral-popliteal bypass and only 12% for a femoral-tibial
bypass.
[0010] Consequently, there is a significant need to improve the
performance of both stents and synthetic bypass grafts in order to
further reduce the morbidity and mortality of CAD and PAD.
[0011] With stents, the approach has been to coat the stents with
various anti-thrombotic or anti-restenotic agents in order to
reduce thrombosis and restenosis. For example, impregnating stents
with radioactive material appears to inhibit restenosis by
inhibiting migration and proliferation of myofibroblasts. (U.S.
Pat. Nos. 5,059,166, 5,199,939 and 5,302,168). Irradiation of the
treated vessel can pose safety problems for the physician and the
patient. In addition, irradiation does not permit uniform treatment
of the affected vessel.
[0012] Alternatively, stents have also been coated with chemical
agents such as heparin or phosphorylcholine, both of which appear
to decrease thrombosis and restenosis. Although heparin and
phosphbrylcholine appear to markedly reduce restenosis in animal
models in the short term, treatment with these agents appears to
have no long-term effect on preventing restenosis. Additionally,
heparin can induce thrombocytopenia, leading to severe
thromboembolic complications such as stroke. Nonetheless, it is not
feasible to load stents with sufficient therapeutically effective
quantities of either heparin or phosphorylcholine to make treatment
of restenosis in this manner practical.
[0013] Synthetic grafts have been treated in a variety of ways to
reduce postoperative restenosis and thrombosis. (Bos et al. 1998.
Small-Diameter Vascular Graft Prostheses:Current Status Achives
Physio. Biochem. 106:100-115). For example, composites of
polyurethane such as meshed polycabonate urethane have been
reported to reduce restenosis as compared with ePTFE grafts. The
surface of the graft has also been modified using radiofrequency
glow discharge to add polyterephalate to the ePTFE graft. Synthetic
grafts have also been impregnated with biomolecules such as
collagen. However, none of these approaches has significantly
reduced the incidence of thrombosis or restenosis over an extended
period of time.
[0014] Because endothelial cells possess certain intrinsic
characteristics such as cell regulatory molecules that decrease the
incidence of thrombosis or restenosis, stimulating the development
of an endothelial cell monolayer on the surface of stents or
synthetic grafts may prevent both restenosis and thrombosis. (Belle
et al. 1997. Stent Endothelialization. Circulation 95:438-448; Bos
et al. 1998. Small-Diameter Vascular Graft Prostheses:Current
Status Archives Physio. Biochem. 106:100-115).
[0015] Endothelial cells have been deposited on the surface of
stents by local delivery of vascular endothelial growth factor
(VEGF), an endothelial cell mitogen, after implantation of the
stent. (Belle et al. 1997. Stent Endothelialization. Circulation
95:438-448.). Because the application of VEGF can have systemic as
well as local effects, this form of treatment may be
unreliable.
[0016] Synthetic grafts have also been seeded with endothelial
cells, but the clinical results with endothelial seeding have been
generally poor, i.e., low post-operative patency rates (Lio et al.
1998. New concepts and Materials in Microvascular Grafting:
Prosthetic Graft Endothelial Cell Seeding and Gene Therapy.
Microsurgery 18:263-256).
[0017] Accordingly, there is a need for development of new methods
and compositions for coating medical devices, including stents and
synthetic grafts, with endothelial cells. This type of coating will
not only prevent restenosis, but also thromboembolic complications
resulting from stent implantation. Methods and compositions that
provide such improvement will eliminate the drawbacks of previous
technology and have a significant positive impact on the morbidity
and mortality associated with CAD and PAD. It is the object of this
invention to prepare stents and synthetic grafts coated in such a
manner as to stimulate adherence of endothelial cells to a medical
device such as a stent or synthetic graft.
SUMMARY OF THE INVENTION
[0018] The invention provides methods and compositions for coating
medical devices with a matrix that promotes adherence of
endothelial cells to a medical device. The matrix incorporates
antibodies that stimulate adherence of endothelial cells to the
surface of the medical device.
[0019] As used herein, "medical device" refers to a device that is
introduced temporarily or permanently into a mammal for the
prophylaxis or therapy of a medical condition. These devices
include any that are introduced subcutaneously, percutaneously or
surgically to rest within an organ, tissue or lumen. Medical
devices may include stents, covered stents such as those covered
with polytetrafluoroethylene (PTFE), or expanded
polytetrafluoroethylene (ePTFE), synthetic grafts, artificial heart
valves, artificial hearts and fixtures to connect the prosthetic
organ to the vascular circulation, venous valves, abdominal aortic
aneurysm (AAA) grafts, inferior venal caval filters, permanent drug
infision catheters, embolic coils, embolic materials used in
vascular embolization (e.g., PVA foams), and vascular sutures.
[0020] Coating of the medical device with the compositions and
methods of this invention may stimulate the development of an
endothelial cell layer on the surface of the medical device,
thereby preventing restenosis as well as other thromboembolic
complications that result from implantation of the medical
device.
[0021] Synthetic grafts and stents can be used for treating CAD or
PAD. A stent or synthetic graft may be coated with a matrix
incorporating antibodies that stimulate adherence of circulating
progenitor endothelial cells to the medical device. The antibodies
may comprise monoclonal antibodies reactive with endothelial cell
surface antigens such as CD34, an antigen expressed on the surface
of progenitor endothelial cells. Fab fragments of the monoclonal
antibody may be used. In another embodiment, monoclonal antibodies
directed against other endothelial surface antigens such as KDP, or
Tie-2, may also be used. In one embodiment, a single type of
antibody that reacts with one antigen may be used. Alternatively, a
plurality of different antibodies directed against different
endothelial cell surface antigens may be mixed together and added
to the matrix.
[0022] The matrix coating the medical device may be composed of
synthetic material, such as polyurethane, poly-L-lactic acid,
cellulose ester or polyethylene glycol. In another embodiment, the
matrix is composed of naturally occurring materials, such as
collagen, fibrin, elastin or amorphous carbon. The matrix may
comprise several layers with a first layer being composed of
synthetic or naturally occurring materials and a second layer
composed of antibodies. The layers may be ordered sequentially,
with the first layer directly in contact with the stent or
synthetic graft surface and the second layer having one surface in
contact with the first layer and the opposite surface in contact
with the vessel lumen.
[0023] In a third embodiment, the matrix may comprise fullerenes,
where the fullerenes range from about C60 to about C100. The
fullerenes may also be arranged as nanotubes, that incorporate
molecules or proteins. The fullerenes matrix may also be mixed with
PTFE or ePTFE, or antibodies. Alternatively, the PTFE or ePTFE may
be layered first on the medical device followed by a second layer
of fullerenes.
[0024] The matrix may be noncovalently or covalently attached to
the medical device. Antibodies may be covalently attached to the
matrix using hetero- or homobifunctional cross-linking
reagents.
[0025] Methods of treatment of atherosclerosis are also provided.
The artery may be the either a coronary artery or a peripheral
artery such as the femoral artery.
BRIEF DESCRIPTION OF THE FIGURES
[0026] FIG. 1 shows an antibody tethered covalently to the matrix
by a cross-linking molecule.
[0027] FIG. 2 shows a diagram of the C60O molecule anchoring the
matrix.
DETAILED DESCRIPTION OF THE INVENTION
Overview
[0028] The present invention provides methods and compositions that
involve coating a medical device such as a stent or synthetic graft
with a matrix which is then used to coat the medical device. In one
embodiment, the matrix incorporates a therapeutically effective
amount of at least one type of antibody that promotes adherence of
endothelial cells to the medical device. Following adherence, the
endothelial cells differentiate and proliferate on the surface of
the matrix. The presence of endothelial cells on the medical device
reduces the occurrence of restenosis and thrombosis after medical
device implantation into a vessel.
[0029] As used herein, the term "antibody" refers to one type of
monoclonal or polyclonal antibody, where the monoclonal or
polydonal antibody binds to one antigen or a functional equivalent
of that antigen. The term antibody encompasses any fragment of an
antibody such as Fab, F(ab').sub.2 or Fc fragments. (An antibody
encompasses a plurality of individual antibody molecules equal to
6.022.times.10.sup.23 molecules per mole of antibody).
[0030] As used herein, a "therapeutically effective amount of the
antibody" means the amount of an antibody that promotes adherence
of endothelial cells to the medical device. The amount of an
antibody needed to practice the claimed invention varies with the
nature of the antibody used. For example, the amount of an antibody
used will depend on the binding constant between the antibody and
the antigen against which it reacts. It is well known to those of
ordinary skill in the art how to determine therapeutically
effective amounts of an antibody to use with a particular
antigen.
[0031] As used herein, "medical device" refers to a device that is
introduced temporarily or permanently into a mammal for the
prophylaxis or therapy of a medical condition. These devices
include any that are introduced subcutaneously, percutaneously or
surgically to rest within an organ, tissue or lumen. Medical
devices may include, stents, covered stents such as those covered
with PTFE, or ePTFE, synthetic grafts, artificial heart valves,
artificial hearts and fixtures to connect the prosthetic organ to
the vascular circulation, venous valves, abdominal aortic aneurysm
(AAA) grafts, inferior venal caval filters, permanent drug infusion
catheters, embolic coils, embolic materials used in vascular
embolization (e.g., PVA foams), and vascular sutures,
[0032] As used herein, "restenosis" refers to the accumulation of a
layer of smooth muscle cells and matrix protein in the intima of an
arterial wall. Vessels may become obstructed because of restenosis.
After PTCA or PTA, smooth muscle cells from the media and
adventitia, which are not normally present in the intima,
proliferate and migrate to the intima and secrete proteins, forming
an accumulation of smooth muscle cells and matrix protein within
the intima. This accumulation causes a narrowing of the lumen of
the artery, reducing blood flow distal to the narrowing. As used
herein, "inhibition of restenosis" refers to the inhibition of
migration and proliferation of smooth muscle cells accompanied by
prevention of protein secretion so as to prevent restenosis and the
complications arising therefrom.
[0033] The subjects that can be treated using the methods and
compositions of this invention may be a mammal, or more
specifically, a human, dog cat, pig, rodent or monkey.
[0034] The methods of the present invention may be practiced in
vivo or in vitro.
[0035] The term "endothelial cell" refers to endothelial cells at
any developmental stage, from progenitor to mature. Fully
differentiated endothelial cells may be isolated from an artery or
vein such as a human umbilical vein, while progenitor endothelial
cells are isolated from peripheral blood or bone marrow. The
endothelial cells are bound to the medical devices by incubation of
the endothelial cells with a medical device coated with the matrix
that incorporates an antibody or other agent that adheres to
endothelial cells.
[0036] The methods of this invention may be practiced on any artery
or vein. Included within the scope of this invention is
atherosclerosis of any artery including coronary, infrainguinal,
aortoiliac, subclavian, mesenteric and renal arteries. Other types
of vessel obstructions, such as those resulting from a dissecting
aneurysm are also encompassed by the invention.
[0037] The medical device may be coated with endothelial cells
after insertion into a vessel. Alternatively, the medical device is
coated with the endothelial cells before insertion of the medical
device. In either case, the presence of endothelial cells on the
lumenal surface of the medical device inhibits or prevents
restenosis and thrombosis.
Endothelial Cells
[0038] Human umbilical vein endothelial cells (HUVEC) are obtained
from umbilical cords according to the methods of Jaffe, et al., J.
Clin. Invest., 52:2745-2757, 1973, incorporated herein by
reference. Briefly, cells are stripped from the blood vessel walls
by treatment with collagenase and cultured in gelatin-coated tissue
culture flasks in M199 medium containing 10% low endotoxin fetal
calf serum, 90 ug/ml preservative-free porcine heparin, 20 ug/ml
endothelial cell growth supplement ECGS), glutamine and
antibodies.
[0039] Progenitor endothelial cells are isolated from human
peripheral blood according to the methods of Asahara et al.
(Isolation of putative progenitor endothelial cells for
angiogenesis. Science 275:964-967, 1997, incorporated herein by
reference). Magnetic beads coated with antibody to CD34 are
incubated with human peripheral blood. After incubation, bound
cells are eluted and can be cultured in M-199 containing 20% fetal
bovine serum and bovine brain extract. (Clonetics, San Diego,
Calif.). Cells are characterized by fluorescent antibodies to CD45,
CD34, CD31, Flk-1, Tie-2, and E-selectin.
[0040] Endothelial cells are transfected with any mammalian
expression vectors that contains any cloned genes encoding proteins
such as platelet derived growth factor (PDGF), fibroblast growth
factor (FGF), or nitric oxide synthase (NOS) using conventional
methods. (See, for example, mammalian expression vectors and
transfection kits commercially available from Stratagene, San
Diego, Calif.). For example, purified porcine progenitor
endothelial cells are transfected with vascular endothelial growth
factor (VEGF) using an adenoviral expression vector expressing the
VEGF cDNA according to the methods of Rosengart et al. (Six-month
assessment of a phase I trial of angiogenic gene therapy for the
treatment of coronary artery disease using direct intramyocardial
administration of an adenovirus vector expressing the VEGF121 cDNA
Ann. Sur. 230(4):466-470 (1999), incorporated herein by
reference).
Antibodies
[0041] Monoclonal antibodies useful in the method of the invention
may be produced according to the standard techniques of Kobler and
Milstein (Continuous cultures of fused cells secreting antibody of
predefined specificity. Nature 265:495-497, 1975, incorporated
herein by reference). Endothelial cells can be used as the
immunogen to produce monoclonal antibodies directed against
endothelial cell surface antigens.
[0042] Monoclonal antibodies directed against endothelial cells are
prepared by injecting HUVEC or purified progenitor endothelial
cells into a mouse or rat. After a sufficient time, the mouse is
sacrificed and spleen cells are obtained. The spleen cells are
immortalized by fusing them with myeloma cells or with lymphoma
cells, generally in the presence of a non-ionic detergent, for
example, polyethylene glycol. The resulting cells, which include
the fused hybridomas, are allowed to grow in a selective medium,
such as HAT-medium, and the surviving cells are grown in such
medium using limiting dilution conditions. The cells are grown in a
suitable container, e.g., microtiter wells, and the supernatant is
screened for monoclonal antibodies having the desired specificity,
ie., reactivity with endothelial cell antigens.
[0043] Various techniques exist for enhancing yields of monoclonal
antibodies such as injection of the hybridoma cells into the
peritoneal cavity of a mammalian host which accepts the cells and
then harvesting the ascites fluid. Where an insufficient amount of
monoclonal antibody collects in the ascites fluid, the antibody is
harvested from the blood of the host. Various conventional ways
exist for isolation and purification of monoclonal antibodies so as
to free the monoclonal antibodies from other proteins and other
contaminants.
[0044] Also included within the scope of the invention are useful
binding fragments of anti-endothelial cell monoclonal antibodies
such as the Fab, F(ab').sub.2, or Fc fragments of these monoclonal
antibodies. The antibody fragments are obtained by conventional
techniques. For example, useful binding fragments may be prepared
by peptidase digestion of the antibody using papain or pepsin.
[0045] Antibodies of the invention are directed to an antibody of
the IgG class from a murine source; however, this is not meant to
be a limitation. The above antibody and those antibodies having
functional equivalency with the above antibody, whether from a
murine source, mammalian source including human, or other sources,
or combinations thereof are included within the scope of this
invention, as well as other classes such as IgM, IgA, IgE, and the
like, including isotypes within such classes. In the case of
antibodies, the term "functional equivalency" means that two
different antibodies each bind to the same antigenic site on an
antigen, in other words, the antibodies compete for binding to the
same antigen. The antigen may be on the same or different
molecule.
[0046] In one embodiment, monoclonal antibodies reacting with the
endothelial cell surface antigen CD34 are used. Anti-CD34
monoclonal antibodies attached to a solid support have been shown
to capture progenitor endothelial cells from human peripheral
blood. After capture, these progenitor cells are capable of
differentiating into endothelial cells. (Asahara et al. 1997.
Isolation of putative progenitor endothelial cells for
angiogenesis. Science 275: 964-967.) Hybridomas producing
monoclonal antibodies directed against CD34 can be obtained from
the American Type Tissue Collection. (Rockville, Md). In another
embodiment, monoclonal antibodies reactive with endothelial cell
surface antigens Flk-1 or Tie-2 are used.
[0047] Polyclonal antibodies reactive against endothelial cells
isolated from the same species as the one receiving the medical
device implant may also be used.
Stent
[0048] The term "stent" herein means any medical device which when
inserted into the lumen of a vessel expands the cross-sectional
lumen of a vessel. The term "stent" includes covered stents such as
those covered with PTFE or ePTFE. In one embodiment, this includes
stents delivered percutaneously to treat coronary artery occlusions
or to seal dissections or aneurysms of the splenic, carotid, iliac
and popliteal vessels. In another embodiment, the stent is
delivered into a venous vessel. The stent can be composed of
polymeric or metallic structural elements onto which the matrix is
applied or the stent can be a composite of the matrix intermixed
with a polymer. For example, a deformable metal wire stent can be
used, such as that disclosed in U.S. Pat. No. 4,886,062 to Wiktor,
incorporated herein by reference. A self-expanding stent of
resilient polymeric material such as that disclosed in published
international patent application WO91/12779 "Intraluminal Drug
Eluting Prosthesis", incorporated herein by reference, can also be
used. Stents may also be manufactured using stainless steel,
polymers, nickel-titanium, tantalum, gold, platinum-irdium, or
Elgiloy and MP35N and other ferrous materials. Stents are delivered
through the body lumen on a catheter to the treatment site where
the stent is released from the catheter, allowing the stent to
expand into direct contact with the lumenal wall of the vessel. It
will be apparent to those skilled in the art that other
self-expanding stent designs (such as resilient metal stent
designs) could be used with the antibodies and matrices of this
invention.
Synthetic Graft
[0049] The term "synthetic graft" means any artificial prosthesis
having biocompatible characteristics. In one embodiment this
includes synthetic grafts made of Dacron (polyethylene
terephthalate, PET) or Teflon (ePTFE). In another embodiment,
synthetic grafts are composed of polyurethane. In yet a third
embodiment, a synthetic graft is composed of an inner layer of
meshed polycarbonate urethane and an outer layer of meshed Dacron.
It will be apparent to those skilled in the art that any
biocompatible synthetic graft can be used with the antibodies and
matrices of this invention. (Bos et al. 1998. Small-Diameter
Vascular Prostheses: Current Status. Archives Physio Biochem.
106:100-115, incorporated herein by reference). Synthetic grafts
can be used for end-to-end anastomosis of vessels or for bypass of
a diseased vessel segment.
Matrix
(A) Synthetic Materials--The matrix that is used to coat the stent
or synthetic graft may be selected from synthetic materials such as
polyurethane, segmented polyurethane-urea/heparin, poly-L-lactic
acid, cellulose ester or polyethylene glycol.
[0050] (B) Naturally Occurring Material--The matrix may be selected
from naturally occurring substances such as collagen, laminin,
heparin, fibrin, cellulose or carbon. A primary requirement for the
matrix is that it be sufficiently elastic and flexible to remain
unruptured on the exposed surfaces of the stent or synthetic
graft.
[0051] (C) Fullerenes--The matrix may also comprise a fullerenes
(the term "fullerenes" encompasses a plurality of fullerenes
molecules). Fullerenes are carbon-cage molecules. The number of
carbon (C) molecules in a fullerenes species varies from about C60
to about C100. Fullerenes are produced by high temperature
reactions of elemental carbon or of carbon-containing species by
processes well known to those skilled in the art; for example, by
laser vaporization of carbon, heating carbon in an electric arc or
burning of hydrocarbons in sooting flames. (U.S. Pat. No.
5,292,813, to Patel et al., incorporated herein by reference; U.S.
Pat. No. 5,558,903 to Bhushan et al., incorporated herein by
reference). In each case, a carbonaceous deposit or soot is
produced. From this soot, various fullerenes are obtained by
extraction with appropriate solvents, such as toluene. The
fillerenes are separated by known methods, in particular by high
performance liquid chromatography (HPLC). Fullerenes may be
synthesized or obtained commercially from Dynamic Enterprises,
Ltd., Berkshire, England or Southern Chemical Group, LLC, Tucker,
Ga.
[0052] Fullerenes may be deposited on surfaces in a variety of
different ways, including, sublimation, laser vaporization,
sputtering, ion beam, spray coating, dip coating, roll-on or brush
coating as disclosed in U.S. Pat. No. 5,558,903.
[0053] An important feature of fullerenes is their ability to form
"activated carbon." The fullerene electronic structure is a system
of overlapping pi-orbitals, such that a multitude of bonding
electrons are cooperatively presented around the surface of the
molecule. (Chemical and Engineering News. Apr. 8, 1991, page 59,
incorporated herein by reference). As forms of activated carbon,
fullerenes exhibit substantial van der Waals forces for weak
interactions. The adsorptive nature of the fullerenes surface may
lend itself to additional modifications for the purpose of
directing specific cell membrane interactions. For example,
specific molecules that possess chemical properties that
selectively bind to cell membranes of particular cell types or to
particular components of cell membranes, e.g., lectins or
antibodies, can be adsorbed to the fullerene surface. The fullerene
surface may also be chemically modified to present specifically
reactive groups to the cell membrane, e.g., oxidants or reductants.
Attachment of different molecules to the fullerene surface may be
manipulated to create surfaces that selectively bind various cell
types, e.g., epithelial cells, fibroblasts, primary explants, or
T-cell subpopulations. U.S. Pat. No. 5,310,669 to Richmond et al.,
incorporated herein by reference; Stephen R. Wilson, Biological
Aspects of Fullerenes, Fullerenes:Chemistry, Physics and
Technology, Kadish et al. eds., John Wiley & Sons, NY 2000,
incorporated herein by reference.
[0054] Fullerenes may also form nanotubes that incorporate other
atoms or molecules. (Liu et al. Science 280:1253-1256 (1998),
incorporated herein by reference). The synthesis and preparation of
carbon nanotubes is well known in the art. (U.S. Pat. No. 5,753,088
to Olk et al., and U.S. Pat. No. 5,641,466 to Ebbsen et al., both
incorporated herein by reference). Molecules such as proteins may
also be incorporated inside carbon nanotubes. For example,
nanotubes may be filled with the enzymes, e.g.,
Zn.sub.2Cd.sub.2-metallothionein, cytochromes C and C3, and
beta-lactamase after cutting the ends of the nanotube. (Davis et
al. Inorianica Chim. Acta 272:261 (1998); Cook et al. Full Sci.
Tech. 5(4):695 (1997), both incorporated herein by reference).
[0055] Three dimensional fullerene structures may also be used.
U.S. Pat. No. 5,338,571 to Mirkin et al., incorporated herein by
reference, discloses three-dimensional, multilayer fullerene
structures that are formed on a substrate surface by (i) chemically
modifying fillerenes to provide a bond-forming species; (ii)
chemically treating a surface of the substrate to provide a
bond-forming species effective to covalently bond with the
bond-forming species of the fillerenes in solution; and, (iii)
contacting a solution of modified fullerenes with the treated
substrate surface to form a fullerene layer covalently bonded to
the treated substrate surface.
(D) Application of the Matrix to the Medical Device
[0056] The matrix should adhere tightly to the surface of the stent
or synthetic graft. Preferably, this is accomplished by applying
the matrix in successive thin layers. Each layer of matrix may
incorporate the antibodies. Alternatively, antibodies may be
applied only to the layer in direct contact with the vessel lumen.
Different types of matrices may be applied successively in
succeeding layers. The antibodies may be covalently or
noncovalently coated on the matrix after application of the matrix
to the stent.
[0057] In order to coat a medical device such as a stent, the stent
is dipped or sprayed with a liquid solution of the matrix of
moderate viscosity. After each layer is applied, the stent is dried
before application of the next layer. In one embodiment, a thin,
paint-like matrix coating does not exceed an overall thickness of
100 microns.
[0058] For example, a suitable matrix coating solution is prepared
by dissolving 480 milligrams (mg) of a drug carrier, such as
poly-D, L-lactid (available as R203 of Boehringer Inc., Ingetheim,
Germany) in 3 milliliters (ml) of chloroform under aseptic
conditions. In principle, however, any biodegradable (or
non-biodegradable) matrix that is blood-and tissue-compatible
(biocompatible) and can be dissolved, dispersed or emulsified may
be used as the matrix if, after application, it undergoes
relatively rapid drying to a self-adhesive lacquer- or paint-like
coating on the medical device.
[0059] For example, coating a stent with fibrin is well known to
one of ordinary skill in the art. In U.S. Pat. No. 4,548,736 issued
to Muller et al., incorporated herein by reference, fibrin is
clotted by contacting fibrinogen with thrombin. Preferably, the
fibrin in the fibrin-containing stent of the present invention has
Factor XIII and calcium present during clotting, as described in
U.S. Pat. No. 3,523,807 issued to Gerendas, incorporated herein by
reference, or as described in published European Patent Application
0366564, incorporated herein by reference, in order to improve the
mechanical properties and biostability of the implanted device.
Preferably, the fibrinogen and thrombin used to make fibrin in the
present invention are from the same animal or human species as that
in which the stent will be implanted in order to avoid any
inter-species immune reactions, e.g., human anti-cow. The fibrin
product can be in the form of a fine, fibrin film produced by
casting the combined fibrinogen and thrombin in a film and then
removing moisture from the film osmotically through a semipermeable
membrane. In the European Patent Application 0366564, a substrate
(preferably having high porosity or high affinity for either
thrombin or fibrinogen) is contacted with a fibrinogen solution and
with a thrombin solution. The result is a fibrin layer formed by
polymerization of fibrinogen on the surface of the medical device.
Multiple layers of fibrin applied by this method could provide a
fibrin layer of any desired thickness. Alternatively, the fibrin
can first be clotted and then ground into a powder which is mixed
with water and stamped into a desired shape in a heated mold (U.S.
Pat. No. 3,523,807). Increased stability can also be achieved in
the shaped fibrin by contacting the fibrin with a fixing agent such
as glutaraldehyde or formaldehyde. These and other methods known by
those skilled in the art for making and forming fibrin may be used
in the present invention.
[0060] If a synthetic graft is coated with collagen, the methods
for preparing collagen and forming it on synthetic graft devices
are well known as set forth in U,S. Patent No. 5,851,230 to Weadock
et al., incorporated herein by reference. This patent describes
methods for coating a synthetic graft with collagen. Methods for
adhering collagen to a porous graft substrate typically include
applying a collagen dispersion to the substrate, allowing it to dry
and repeating the process. Collagen dispersions are typically made
by blending insoluble collagen (approximately 1-2% by weight) in a
dispersion at acidic pH (a pH in a range of 2 to 4). The dispersion
is typically injected via syringe into the lumen of a graft and
massaged manually to cover the entire inner surface area with the
collagen slurry. Excess collagen slurry is removed through one of
the open ends of the graft. Coating and drying steps are repeated
several times to provide sufficient treatment.
[0061] In yet another embodiment the stent or synthetic graft is
coated with amorphous carbon. In U.S. Pat. No. 5,198,263,
incorporated herein by reference, a method for producing a
high-rate, low-temperature deposition of amorphous carbon films in
the presence of a fluorinated or other halide gas is described.
Deposition according to the methods of this invention can be
performed at less than 100.degree. C., including ambient room
temperature, with a radio-frequency, plasma-assisted,
chemical-vapor deposition process. The amorphous carbon film
produced using the methods of this invention adheres well to many
types of substrates, including for example glasses, metals,
semiconductors, and plastics.
[0062] Attachment of a fullerene moiety to reactive amino group
sites of an amine-containing polymer to form the fullerene-graft,
amine-containing polymers may be performed as described in U.S.
Pat. No. 5,292,813. Chemical modification in this manner allows for
direct incorporation of the fullerenes into the stent. In another
embodiment, the fullerenes may be deposited on the surface of the
stent or synthetic grafts as described above. (see, WO 99/32184 to
Leone et al., incorporated by reference). Fullerenes may also be
attached through an aldehyde bond (Yamago et al., Chemical
Derivatization of Organofullerenes through Oxidation, Reduction and
C-O and C-C Bond Forming Reactions. J. Org. Chem., 58 4796-4798
(1998), incorporated herein by reference). C60O may also be
attached directly through an epoxide group on the fullerene to a
stent. The attachment is through a covalent linkage to the oxygen.
This compound and the protocols for coupling are commercially
available from BuckyUSA. (BuckyUSA, Houston, Tex.).
[0063] (E) Addition of Antibodies to the Matrix--Antibodies that
promote adherence of progenitor endothelial cells can be
incorporated into the matrix, either covalently or noncovalently.
Antibodies may be incorporated into each layer of matrix by nixing
the antibodies with the matrix coating solution. Alternatively, the
antibodies may be covalently or noncovalently coated on to last
layer of matrix that is applied to the medical device.
[0064] In one embodiment, the antibodies are added to a solution
containing the matrix. For example, Fab fragments on anti-CD34
monoclonal antibody are incubated with a solution containing human
fibrinogen at a concentration of between 500 and 800 mg/dl. It will
be appreciated that the concentration of anti-CD34 Fab fragment
will vary and that one of ordinary skill in the art could determine
the optimal concentration without undue experimentation. The stent
is added to the Fab/fibrin mixture and the fibrin activated by
addition of concentrated thrombin (at a concentration of at least
1000 U/ml). The resulting polymerized fibrin mixture containing the
Fab fragments incorporated directly into the matrix is pressed into
a thin film (less than 0.12 cm) on the surface of the stent or
synthetic graft. Virtually any type of antibody or antibody
fragment can be incorporated in this manner into a matrix solution
prior to coating of a stent or synthetic graft.
[0065] In another embodiment, antibodies are covalently coupled to
the matrix. In one embodiment, the antibodies are tethered
covalently to the matrix through the use of hetero- or
homobifunctional linker molecules. As used herein the term
"tethered" refers to a covalent coupling of the antibody to the
matrix by a linker molecule. The use of linker molecules in
connection with the present invention typically involves covalently
coupling the linker molecules to the matrix after it is adhered to
the stent. After covalent coupling to the matrix, the linker
molecules provide the matrix with a number of functionally active
groups that can be used to covatently couple one or more types of
antibody. FIG. 1 provides an illustration of coupling via a
cross-linking molecule. An endothelial cell, 1.01, binds to an
antibody, 1.03, by a cell surface antigen, 1.02. The antibody is
tethered to the matrix, 1.05-1.06, by a cross-linking molecule,
1.04. The matrix, 1.05-1.06, adheres to the stent, 1.07. The linker
molecules may be coupled to the matrix directly (i.e., through the
carboxyl groups), or through well-known coupling chemistries, such
as, esterification, amidation, and acylation. The linker molecule
may be a di- or tri-amine functional compound that is coupled to
the matrix through the direct formation of amide bonds, and
provides amine-functional groups that are available for reaction
with the antibodies. For example, the linker molecule could be a
polyamine functional polymer such as polyethyleneimine (PEI),
polyallylamine (PALLA) or polyethyleneglycol (PEG). A variety of
PEG derivatives, e.g., mPEG-succinimidyl propionate or
mPEG-N-hydroxysuccinimide, together with protocols for covalent
coupling, are commercially available from Shearwater Corporation,
Birmingham, Ala. (See also, Weiner et al., Influence of a
poly-ethyleneglycol spacer on antigen capture by immobilized
antibodies. J. Biochem. Biophys. Methods 45:211-219 (2000),
incorporated herein by reference). It will be appreciated that the
selection of the particular coupling agent may depend on the type
of antibody used and that such selection may be made without undue
experimentation. Mixtures of these polymers can also be used. These
molecules contain a plurality of pendant amine-functional groups
that can be used to surface-immobilize one or more antibodies.
[0066] Antibodies may be attached to C60O fullerene layers that
have been deposited directly on the surface of the stent. Cross
linking agents may be covalently attached to the fullerenes. The
antibodies are then attached to the cross-linking agent, which in
turn is attached to the stent. FIG. 2 provides an illustration of
coupling by C60O. The endothelial cell, 2.01, is bound via a cell
surface antigen, 2.02, to an antibody, 2.03, which in turn is
bound, covalently or non-covalently to the matrix, 2.04. The
matrix, 2.04, is coupled covalently via C60O, 2.05, to the stent,
2.06.
EXPERIMENTAL EXAMPLES
[0067] This invention is illustrated in the experimental details
section which follows. These sections set forth below the
understanding of the invention, but are not intended to, and should
not be construed to, limit in any way the invention as set forth in
the claims which follow thereafter.
Example 1
Adherence of Human Endothelial Cells to CD34 Fab-Coated Stents
Materials and Methods
1. Cells
[0068] HUVEC will be prepared from human umbilical cords by the
method of Jaffe (Jaffe, E. A. In "Biology of Endothelial Cells", E.
A. Jaffe, ed., Martinus-Nijhoff, The Hague (1984), incorporated
herein by reference) and cultured in Medium 199 supplemented with
20% fetal calf serum (FCS), L-glutamine, antibiotics, 130 ug/ml
heparin and 1.2 mg/ml endothelial cell growth supplement
(Sigma-Aldrich, St. Louis, Mo.).
[0069] Progenitor endothelial cells will be isolated from human
peripheral blood by the method of Asahara et al. (Isolation of
Putative progenitor endothelial cells for angiogenesis. Science
275:964-967). Monoclonal anti-CD34 antibodies will be coupled to
magnetic beads and incubated with the leukocyte fraction of human
whole blood. After incubation, bound cells will be eluted and
cultured in M-199 containing 20% fetal bovine serum and bovine
brain extract. (Clonetics, San Diego, Calif.). Cells will be
characterized by fluorescent antibodies to CD45, CD34, CD31, Flk-1,
Tie-2, and E- selectin.
2. Coating of Stents
[0070] A. R stents produced by Orbus International B.V. (Leusden,
The Netherlands) will be incubated with human fibrinogen (Sigma,
St. Louis, Mo.) 500-800 mg/ml together with Fab fragments of
anti-CD34 monoclonal antibody and the fibrinogen will be
polymerized by the addition of 1000 units/ml of thrombin. After
incubation of the stent with the polymerized fibrin mixture
containing the anti-CD34 monoclonal Fab fragments, the fibrin will
be compressed into a thin film less than 0.012 cm) against the R
Stent. The R-Stent having the thin, fibrin film containing the Fab
fragments will be washed three times with phosphate-buffered saline
(PBS) containing 0.5% bovine serum albumin (BSA) at room
temperature.
[0071] B. Alternatively, R stents will be coated with
mPEG-succinimidyl propionate (Shearwater Corporation, Birmingham,
Ala.). The succinimidyl group will be reacted with the anti-CD34
monoclonal Fab fragments (Fab-PEG coated R stents) according to the
manufacturer's instructions to form a stable amide linkage between
the PEG derivative and the Fab fragment.
3. Endothelial Cell Binding Assay
[0072] The fibrin-anti-CD34 Fab coated R-stents or Fab-PEG coated R
stents will be incubated with isolated HUEC or isolated progenitor
endothelial cells at cellular concentrations of between 100,000 and
1,000,000 cells/ml in M199 containing 0.5% BSA at 37.degree. C. in
a 5% CO.sub.2 humidified atmosphere. Prior to incubation with the
stent, the HUVEC or progenitor endothelial cells will be labeled
with [.sup.3H]-thymidine for 24 hours. After incubation of the
labeled endothelial cells with the stents coated with fibrin and
Fab anti-CD34 for between 4 and 72 hours, the stents will be
removed from the solution and washed 5 times with M199 containing
0.5% BSA. Bound endothelial cells will be removed by trypsinization
and binding of labeled endotheltal cells to the stents will be
assessed by scintillation counting of [.sup.3H]-thynidine. As
negative control, stents coated with fibrin alone or uncoated
stents will be incubated with [.sup.3H]-thymidine-labeled
endothelial cells. Results will be evaluated statistically using a
t-test to determine differential binding. Stents coated with fibrin
which incorporate monoclonal anti-CD34 Fab fragments will show
significantly increased binding of endothelial cells as compared
with uncoated stents.
Example 2
Proliferation of Human Endothelial Cells on CD34 Fab-Coated
Stents
Endothelial Cell Proliferation Assay
[0073] R stents coated with fibrin that incorporates anti-CD34 Fab
fragments will be incubated with HUVEC or progenitor endothelial
cells for between 4 and 72 hours in M199 containing 0.5% BSA. After
incubation of the stents with the HUVEC or progenitor endothelial
cells, the stents will be washed 5 times with M199 containing 0.5%
BSA and then incubated with [.sup.3H]-thymidine.
[.sup.3H]-thymidine incorporation will be assessed in washed and
harvested HUVEC or progenitor endothelial cells (cells will be
harvested with trypsin). Proliferation of HUVEC or progenitor
endothelial cells on fibrin-coated stents will be compared with
endothelial cell proliferation in standard microtiter dishes.
Proliferation of HUVEC or progenitor endothelial cells on
fibrin-coated stents will be equal to or greater than proliferation
of endothelial cells in microtiter dishes
Example 3
Production of Monoclonal Antibodies Reactive With Huvec and
Progenitor Endothelial Cells
[0074] BALB/c mice will be immunized, intraperitoneally 3-4 times
at 2-4 weekly intervals, with 1.5.times.10.sup.6 HUVEC in PBS or
1.5.times.10.sup.5 progenitor endothelial cells and challenged 3
days prior to spleen-cell removal with 1.5.times.10.sup.6 HUVEC or
1.5.times.10.sup.6 progenitor endothelial cells. A spleen-cell
suspension will be prepared, fused with the myeloma NS1/1 AG4.1 and
hybridomas grown up and cloned. To improve hybridoma growth and
cloning efficiencies, 10% endothelial-cell conditioned medium
(HVEC) will be included in culture media. Initially, hybridoma
culture supernatants will be tested for reactivity with HUVEC or
progenitor endothelial cells by immunofluorescence flow cytometry
(FACS). Briefly, HUVAC (1.5.times.10.sup.4) or progenitor
endothelial cells (1.5.times.10.sup.4) will be incubated (30 min.,
4.degree. C.) with undiluted hybridoma supernatant, washed and
incubated with fluorescein-isothiocyanate (FITC)-sheep F(ab').sub.2
anti-mouse Ig(100 ug/mi). Following final washing, the endothelial
cells will be examined for monoclonal antibody binding by FACS
analysis. Positive hybridoma supernatants will be screened on the
human melanoma cell line MM-170 to eliminate non-endothelial
specific mAbs. Endothelial specificity will be further confirmed by
screening of monoclonal antibodies on a panel of human tumor cell
lines as well as human lymphocytes, monocytes, neutrophils, red
cells and platelets.
Example 4
Porcine Balloon Injury Studies
[0075] Implantation of antibody-covered stents will be performed in
juvenile Yorkshire pigs weighing between 25 and 30 kg. Animal care
will comply with the "Guide for the Care and Use of Laboratory
Animals" (NIH publication No. 80-23, revised 1985). After an
overnight fast, animals will be sedated with ketamine hydrochloride
(20 mg/kg). Following the induction of anesthesia with thiopental
(12 mg/kg) the animals will be intubated and connected to a
ventilator that will administer a mixture of oxygen and nitrous
oxide (1:2 [vol/vol]). Anesthesia will be maintained with 0.5-2.5
vol % isoflurane, Antibiotic prophylaxis will be provided by an
intramuscular injection of 1,000 mg of a mixture of procaine
penicillin-G and benzathine penicillin-G (streptomycin).
[0076] Under sterile conditions, an arteriotomy of the left carotid
artery will be performed and a 9F-introducer sheath will be placed
in the left carotid artery. All animals will be given 7,500 IU of
heparin sodium and 100 mg of acetylsalicylic acid intravenously.
Additional 2,500 IU boluses of heparin will be administered
periodically throughout the procedure in order to maintain an
activated clotting time above 300 seconds. An 8F guiding catheter
will be introduced through the carotid sheath and passed to the
origin of the iliac artery. Angiography will be performed after the
administration of 1 mg of isosorbide dinitrate and images will be
analyzed using a quantitative coronary angiography system. A
3F-embolectomy catheter will be inserted into the common femoral
artery, and passed distal to the segment selected for stent
implantation. The embolectomy balloon will be inflated to a size
0.5 mm larger than the arterial segment and withdrawn twice to
denude the vessel. Immediately after denudation, a fibrin-coated
stent incorporating an Fab fragment of a monoclonal antibody will
be inserted through the guiding catheter and deployed in the
denuded segment of the femoral artery. Animals will be sacrificed
both at 3 days and at eight weeks after stent implantation. The
animal will first be sedated and anesthetized as described above.
The stented femoral segments will be explanted and then placed in
4% paraformaldehyde in 0.1 M phosphate buffer pH 7.2 at 4.degree.
C. for 48 h. A rectangular section of the vessel wall will be
removed for further processing for electron microscopic evaluation
of surface coverage of endothelial cells. This portion of the
stented vessel will be placed in 0.15 cacodylate buffer and further
fixed with 2.5% glutaraldehyde in 0.15 M cacodylate. The tissue
will then be post-fixed with 0.1 M cacodylate buffer containing 1%
OsO.sub.4 and 50 mM ferricyanide (K.sub.3[Fe(CN).sub.6]), and
further processed. (Reduction in thrombotic events with
heparin-coated Palmaz-Schatz stents in normal porcine coronary
arteries, Circulation 93:423-430, incorporated herein by
reference).
[0077] The remaining sections of the stented arterial segments will
be impregnated with three changes of methy methacrylate as
described by van Beusekom et al. (Cardiovasc Pathol 5:69-76 (1996)
incorporated herein by reference). Embedded arterial segments with
the stent in place will be cut into sections 3 to 5 .mu.m thick on
a motor-driven rotary microtome (H-350, Microm GmbH, Munich,
Germany) using stainless steel disposable knives. On chrome
aluminum coated slides, sections will be stretched on a hot plate
at 40.degree. C. using a mixture of 60% 2-butoxyethanol and 10%
ethanol in water. Sections will be covered by a plastic film,
excess butoxyethanol-ethanol mixture removed and the slides will be
left overnight to dry in a 40.degree. C. oven. Sections will then
be deplasticized in a solution of equal volumes of
xylene-chloroform for 30 to 60 minutes. Standard staining
procedures for light microscopy will then be performed on the
prepared sections. Statistics: Data will be presented as the
mean.+-.standard error of the mean (SD) of the independent
experiments. Statistical significance will be determined by one way
analysis of variance (ANOVA) and Fisher's PLSD test (StatView 4.01;
Brain Power, Inc., Calabasas, Calif.) For data of treated and
untreated segments of femoral arteries, a paired t test (StatView
4.01) will be used. A p value of <0.05 will be considered a
statistically significant difference between the means. Animals
treated with a stent incorporating an anti-porcine endothelial cell
monoclonal Fab fragment will show increased endothelial cell
coverage and significantly reduced restenosis as compared with
controls having an uncoated stent implanted.
Example 5
Transfection of Porcine Progenitor Endothelial Cells
[0078] Porcine progenitor endothelial cells will be isolated from
pig peripheral blood by the method of Asahara et al. (Isolation of
Putative progenitor endothelial cells for angiogenesis. Science
275:964-967). Monoclonal anti-CD34 antibodies will be coupled to
magnetic beads and incubated with the leukocyte fraction of pig
whole blood. After incubation, bound cells will be eluted and
cultured in M-199 containing 20% fetal bovine serum and bovine
brain extract. (Clonetics, San Diego, Calif.). Cells will be
characterized by fluorescent antibodies to CD45, CD34, CD31, Flk-1,
Tie-2, and E- selectin.
[0079] For example, purified porcine progenitor endothelial cells
will be transfected with vascular endothelial growth factor (VEGF)
using an adenovirus vector expressing the VEGF cDNA according to
the methods of Rosenaart et al. (Six-month assessment of a phase I
trial of angiogenic gene therapy for the treatment of coronary
artery disease using direct intramyocardial administration of an
adenovirus vector expressing the VEGF121 cDNA. Ann. Surg.
230(4):466-470 (1999), incorporated herein by reference).
[0080] The transfected purified porcine progenitor cells expressing
VEGF will be infused into the porcine femoral artery model after
balloon injury and stent implantation as described in Example 4
using a double-balloon chamber infusion catheter (Cordis Corp)
which isolates the stented portion of the femoral artery.
Restenosis will be compared in balloon angioplasty stent-treated
pigs infused with VEGF-transfected porcine progenitor cells as
compared with pigs infused with un-transfected porcine progenitor
endothelial cells. Expression of VEGF in the re-infused porcine
progenitor endothelial cells will result in a decreased incidence
and severity of restenosis in the anti-CD34 coated stents.
Example 6
Preparation of Aminosilane Peo Tethered Antibodies
[0081] Stent Preparation--stents will be made from 316 L stainless
steel and will be cleaned and passivated by first washing in an
anionic detergent in an ultrasonic cleaner and then soaked in hot
nitric acid with agitation, followed by a final deionized water
rinse.
[0082] Derivatized stents will be prepared as follows--stents will
be dipped into a 2% mixture of N-(2-aminoethyl-3-aminopropyl)
trimethoxysilane in 95% ethanol for three minutes, removed, air
dried at room temperature and then cured for 10 minutes at
110.degree. C.
[0083] Polyethylene glycol (PEG) Spacer Coupling--Derivatized
stents will be placed in 100ml of 0.1 M MES buffer containing 10 mM
Dicarboxymethyl-PEG and 500 mg of EDC added and incubated at
25.degree. C. with constant stirring for two hours.
[0084] Tethered Antibody--Antibodies to endothelial cells will be
immobilized to the PEG functionalized stents in a one-step
carbodiimide coupling reaction by immersing the stents into 150 ml
of 0.1 M MES buffer (pH 4.5) into which 1.0 mg of murine anti-CD34
IgG.sub.1 antibody is dissolved and incubated at 25.degree. C. for
two hours. Stents will be removed from the solution and rinsed five
times with 50 ml of phosphate buffered saline (pH 7.2) with 0.02%
Tween 20.
[0085] Reagents include:
N-(2-aminoethyl-3-aminopropyl)trimethoxysilane (Degussa-Huls); MES
buffer--morpholine ethane sulfonic acid buffer (Sigma, St. Louis,
Mo.); EDC--1-ethyl-3-(3-dimethylaminopropyl) carbodiinde (Sigma,
St. Louis, Mo.); Dicarboxymethyl-PEG -Dicarboxymethyl-poly(ethylene
glycol) [MW 3400] (Shearwater, Huntsville, Ala).
[0086] Having described several different embodiments of the
invention, it is not intended that the invention is limited to
these embodiments it is intended that modifications and variations
may be made by one skilled in the art without departing from the
spirit and scope of the invention as defined in the claims.
* * * * *