Comparison of methods for local delivery of tissue factor pathway inhibitor to balloon-injured arteries in rabbits

Association study to evaluate TFPI gene in CAD in Han Chinese

Background

Tissue factor pathway inhibitor (TFPI) is the main physiological inhibitor of TF-induced blood coagulation process, and may play essential roles in the pathogenesis of major adverse cardiac events. This study was designed to determine whether the variation of TFPI was related with coronary artery disease (CAD) in the Han Chinese populations.

Methods

A total of 1271 patients with coronary atherosclerosis and 1287 normal individuals from northern China were enrolled in the present study. Four tagging single-nucleotide polymorphisms (SNPs) (rs7586970, rs6434222, rs10153820 and rs8176528) from TFPI were selected and genotyped by direct sequencing. And the genotypes of the above SNPs were determined in all these participants.

Results

In the populations from Beijing and Harbin, no significant case-control differences in the frequencies of TFPI polymorphism (rs10153820 and rs8176528) were observed between CAD patients and controls. Meanwhile, two SNPs of TFPI (rs7586970 and rs6434222) were found to be associated with CAD in both groups. In stratified analyses based on gender, smoking, hypertension, diabetes mellitus and hyperlipidemia, we further determined that the investigated genetic variations of the TFPI genes seemed to be related with diabetes mellitus in CAD patients.

Conclusions

Genetic variations of the TFPI genes seem to be related with CAD, which likely cooperate with metabolic risk factor (diabetes mellitus) and play critical roles in the pathogenesis of coronary artery disease.

Regulation of functions of vascular wall cells by tissue factor pathway inhibitor: basic and clinical aspects

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that inhibits the initial reactions of blood coagulation. A major pool of TFPI is the form associated with the surface of endothelial cells, which is speculated to play an important role in regulating the functions of vascular wall cells. TFPI consists of 3 tandem Kunitz inhibitor domains, the first and second of which inhibit the tissue factor-factor VIIa complex and factor Xa, respectively. Recent findings indicate that TFPI has another function, ie, the modulation of cell proliferation. This function is based on the interaction of the C-terminal region of TFPI with these cells. In addition to endothelial cells, it has been shown that many other vascular wall cells can synthesize TFPI, eg, mesangial cells, smooth muscle cells, monocytes, fibroblasts, and cardiomyocytes. TFPI is associated with these cells mainly through heparan sulfate proteoglycans on their surface. However, recent findings suggest that there are several other candidates for TFPI-binding proteins on these cells. On the other hand, studies on plasma levels of TFPI in patients with various diseases suggest that TFPI may be a marker of endothelial cell dysfunction. An increasing number of reports suggest that recombinant TFPI may attenuate thrombosis and prevent restenosis. Clinical trials are needed to explore these possibilities. Recent reports also indicate that the application of recombinant TFPI or TFPI gene transfer prevents restenosis in addition to thrombosis after arterial injury in the animal model; corroboration of these reports awaits clinical investigation.

Polylysine as a vehicle for extracellular matrix-targeted local drug delivery, providing high accumulation and long-term retention within the vascular wall

We present the first steps in the elaboration of an approach of extracellular matrix-targeted local drug delivery (ECM-LDD), designed to provide a high concentration, ubiquitous distribution, and long-term retention of a drug within the vessel wall after local intravascular delivery. The approach is based on the concept of a bifunctional drug comprising a "therapeutic effector" and an "affinity vehicle," which should bind to an abundant component of the vessel wall. The aim of the present study was to select molecules suitable for the role of affinity vehicles for ECM-LDD and to study their intravascular delivery and retention ex vivo and in an animal model. By use of fluorescence microscopy, the following molecules were selected on the basis of strong binding to cross sections of human vessels: protamine, polylysine, polyarginine, a glycosaminoglycan-binding peptide from vitronectin, and a synthetic dendrimer. With polylysine as a prototypic affinity vehicle, we showed that after intravascular delivery, polylysine was concentrated throughout a luminal layer of the vascular wall to an extremely high concentration of 20 g/L and was retained therein for at least 72 hours of perfusion without noticeable losses. Low molecular weight (fluorescein) and high molecular weight (hirudin) compounds could be chemically conjugated to polylysine and were retained in the vessel wall after intravascular delivery of the conjugates. In conclusion, by use of the ECM-LDD method, an extremely high concentration and long-term retention of locally delivered drug can be reached. Polycationic molecules can be considered as potential affinity vehicles for ECM-LDD.

Delivery of endothelial cells to balloon-dilated rabbit arteries with use of a local delivery catheter

PURPOSE

Experiments were performed to determine if a local delivery catheter could deliver endothelial cells that would be retained on the luminal surface of balloon-dilated arteries.

MATERIALS AND METHODS

Six New Zealand White rabbits underwent carotid catheterization, arteriography, and balloon angioplasty of an external iliac artery. A local delivery catheter (Dispatch) was then positioned at the site of angioplasty and the 3-mm balloon was inflated. Cultured rabbit endothelial cells (1.26 +/- 0.3 x 10(6) ), previously stained with fluorescent dye PKH26, were delivered to the artery in three infusions separated by 10 minutes. The delivery balloon was deflated and removed 25 minutes after the last delivery. The arteries were then perfusion-fixed in situ at physiologic pressure, removed, and divided into four segments, and the segments were rapidly frozen and cryosectioned. Eight sections from each arterial segment were examined by means of epifluorescence microscopy. The luminal surface of each artery was visually divided into eight sectors of equal length and each sector was assigned a score based on the degree of endothelial coverage (0 = no coverage, 1 = <50% coverage, 2 = >50% coverage).

RESULTS

The endothelial coverage score for the six arteries averaged 0.40 +/- 0.46 (SD; range, 0.04-1.24). Areas of each artery receiving scores of 0, 1, and 2 averaged 68%, 25%, and 7%, respectively. Average coverage scores were 0.42, 0.38, 0.51, and 0.28 for individual segments along the length of the artery.

CONCLUSIONS

The Dispatch local delivery catheter is able to deliver endothelial cells that adhere to balloon-dilated arteries. Although the magnitude of cellular retention was modest and varied among arteries, the retention along the length of each artery was constant.

Local delivery of 17-beta-estradiol decreases neointimal hyperplasia after coronary angioplasty in a porcine model

BACKGROUND

Neointimal hyperplasia is an important mechanism of restenosis after percutaneous transluminal coronary angioplasty (PTCA). Systemically administered estrogen is known to inhibit neointimal formation after arterial injury.

OBJECTIVES

We sought to assess the efficacy of locally delivered 17-beta-estradiol (BE) in inhibiting neointimal hyperplasia after PTCA.

METHODS

Eighteen juvenile farm pigs were studied. Coronary angioplasty was performed in all three coronary arteries of each animal. After PTCA, each coronary artery in each pig was randomized to receive either local delivery of 600 microg BE, vehicle alone or PTCA only. Twelve animals were euthanized at 28 days for morphometric analysis, and four animals were euthanized at seven days for immunohistochemical analysis of vascular smooth muscle cell (SMC) proliferative activity. Two animals died a few days after PTCA and were excluded.

RESULTS

On morphometric study, the arterial segments treated with BE demonstrated significantly less neointimal proliferation. Arteries treated with BE had reductions in several indexes of restenosis compared with arteries treated with vehicle alone or PTCA only: neointimal area (0.4+/-0.09 mm2 for BE vs. 1.14+/-0.33 mm2 for vehicle alone vs. 0.88+/-0.2 mm2 for PTCA only, p<0.05), percent neointima (12.16+/-2.57% vs. 25.46+/-4.73% vs. 23.02+/-3.97%, p<0.025), neointima/media area (0.59+/-0.14 vs. 1.75+/-0.41 vs. 1.67+/-0.43, p<0.01) and restenotic index (1.3+/-0.14 vs. 2.42+/-0.22 vs. 2.4+/-0.23, p<0.005). Immunohistochemistry showed decreased SMC proliferative activity in BE-treated arteries compared with the other two treatment groups (p<0.05).

CONCLUSIONS

Local delivery of BE significantly decreases neointimal hyperplasia after PTCA in pigs, probably by the inhibition of SMC proliferation.