The making of indigenous vascular prosthesis.

BACKGROUND & OBJECTIVES: Vascular illnesses are on the rise in India, due to increase in lifestyle diseases and demographic transition, requiring intervention to save life, organ or limbs using vascular prosthesis. The aim of this study was to develop indigenous large diameter vascular graft for treatment of patients with vascular pathologies. METHODS: The South India Textile Research Association, at Coimbatore, Tamil Nadu, India, developed seamless woven polyester (Polyethylene terephthalate) graft at its research wing. Further characterization and testing followed by clinical trials were conducted at Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, India. Fifteen in vivo experiments were carried out in 1992-1994 in pigs as animal model. Controlled (phase I) clinical trial in ten patients was performed along with control graft. Thereafter, phase II trial involved 22 patients who underwent multi-centre clinical trial in four centres across India. RESULTS: Laboratory testing showed that polyester graft was non-toxic, non-leeching and non-haemolytic with preserved long-term quality, further confirming in pigs by implanting in thoracic aorta, comparable to control Dacron grafts. Perigraft incorporation and smooth neointima formation which are prime features of excellent healing characteristics, were noted at explantation at planned intervals. Subsequently in the phase I and II clinical trials, all patients had excellent recovery without mortality or device-related adverse events. Patients receiving the test graft were followed up for 10 and 5 years, respectively. Serial clinical, duplex scans and CT angiograms performed periodically confirmed excellent graft performance. INTERPRETATION & CONCLUSIONS: Indigenously developed Chitra vascular graft was comparable to commercially available Dacron graft, ready for clinical use at affordable cost to patients as against costly imported grafts.

Preclinical and early clinical experience with a biodegradable polymer-based, rapamycin-eluting, Indian drug-eluting coronary stent: the BIO-RAPID study.

OBJECTIVE: To evaluate the performance of a biodegradable polymer based rapamycin-eluting coronary stent in a porcine model and demonstrate its safety and efficacy in the treatment of patients with de novo coronary stenosis. BACKGROUND: The indefinite presence of the polymer after the implantation of drug-eluting stents may initiate and sustain inflammation and contribute to the occurrence of late complications. METHODS: Seven study stents and 5 polymer-coated (control) stents were implanted in porcine carotid arteries. Histomorphometric analysis was performed 8 weeks after stent implantation. After establishing the safety of the stent in the animal model, a single-center, non-randomized study in patients with de novo coronary artery lesions was performed. Forty-nine stents were implanted in 43 patients. The 6-month clinical follow-up was 91% (39/43) and angiographic follow-up was 67% (29/43). The primary safety endpoint was the occurrence of 30-day major adverse cardiovascular events (MACE) and the principal efficacy endpoint was the 6-month angiographic late loss and binary restenosis rate. RESULTS: In the porcine model, the study stent showed acceptably low injury, inflammation and fibrin scores. There was a quantitative reduction in neointimal hyperplasia which was not statistically different from the control stent. However, in the first-in-man evaluation, there was significant suppression of intimal growth as evidenced by an angiographic late loss of 0.28 +/- 0.45 mm at 6 months. The restenosis rate was 10.3% (3/297). There was no death, stent thrombosis or myocardial infarction at 30 days or at 6 months. The 6-month target lesion revascularization rate was 3.47 percent; (1/29). CONCLUSION: This preclinical and early clinical experience demonstrates the safety and efficacy of a novel biodegradable polymer-based rapamycin-eluting coronary stent.

Endocardial endothelial cells stimulate proliferation and collagen synthesis of cardiac fibroblasts.

Given that vascular endothelial cells play an important role in the modulation of vascular structure and function, we hypothesized that endocardial endothelial cells (EECs) may have a modulator role in regulating the cardiac interstitial cells. Endocardial endothelial cells were isolated from freshly collected pig hearts and cardiac fibroblasts were isolated from 3- to 4-d-old Wistar rats. Fibroblasts were cultured in the presence or absence of conditioned medium from EECs. Proliferation of cardiac fibroblasts was measured by the incorporation of [3H]- Thymidine and collagen synthesis was assayed by the incorporation of [3H]-Proline. To determine the involvement of signaling mediators, in separate experiments, cardiac fibroblasts were incubated with BQ123 (selective ETA receptor antagonist), PD142893 (nonselective ETA/ETB receptor antagonist), Bis-indolylmaleimide (PKC inhibitor), PD 098059 (MEK inhibitor), or neutralizing anti-transforming growth factor (TGF)-beta-antibody. Endocardial endothelium-derived factors endothelin (ET)-1, TGF-beta, and Angiotensin (Ang)-II in the conditioned medium were assayed by enzyme-linked immunosorbent assay using commercially available kits. We report here evidence that suggest that endocardial endothelial cells stimulate both proliferation and collagen synthesis of cardiac fibroblasts. The response seems to be mediated by endothelin through its ETA receptor. Our results also indicate that protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) pathways are essential for the EEC-induced proliferation of cardiac fibroblasts.

Comparative evaluation of absorbable hemostats: advantages of fibrin-based sheets.

Bioactive hemostats and wound dressings consist of either inherently active materials or act as delivery vehicles which contain such materials. Fibrin is a natural hemostat and scaffold, guiding the direction of wound contraction and closure. In order to improve the ease of application of liquid fibrin glue, we have made a freeze-dried form of polymerized fibrin that supports hemostasis and wound healing. The bleeding from the middle ear artery of rabbits was found to be arrested instantaneously on application of fibrin sheets, even when the animal was heparinized systemically. As the fibrin sheet was found to be fragile, gelatin was incorporated to the sheet and thus the mechanical stability was improved without compromising the hemostatic effect. The efficacy of the fabricated fibrin and fibrin-gelatin sheets to seal traumatized rat liver was compared with commercially available hemostats, Abgel (cross-linked gelatin) and Surgicel (cross-linked cellulose). Tissue compatibility of all the hemostats was studied by analyzing the liver tissue 15 days after application. While the hemostatic effect was best with fibrin and fibrin-gelatin sheets, both Surgicel and Abgel were not capable of arresting the bleeding quickly. Gross analysis of tissue on the 15th day of application, visibly, Abgel was not only degraded but resulted in severe adhesions of internal organs and histologically capsule formation around the implant was evident. Though Surgicel was also seen as cream soft material on the site of application that joined two pieces of liver, there was no adhesion of other internal organs and histologically, immune reaction and foreign-body-type giant cells were present in large amounts. Fibrin was not found grossly on application site whereas fibrin-gelatin was seen as a small white spot. Granulation tissue formation and cell migration into the fibrin-based sheets were evident, and therefore, fibrin-based sheets are not only efficient hemostats but showed optimum degradation and wound healing.

An improved method for isolation of anti-viper venom antibodies from chicken egg yolk.

The production of antibodies and its purification from mammalian blood has been found low yielding and laborious. Therefore, anti snake venom antibodies for therapeutic use is obtained mostly as polyvalent whole serum or partially purified polyvalent immunoglobulin. The side effects of anti snake venom (ASV) therapy are mainly serum sickness and renal failure, which may be reduced by using sufficiently pure antibodies. Therefore, we have standardized a simple method for production of purified antivenom. Here, we present the development of polyclonal antibodies against viper venom in hens and its isolation from the egg yolk of immunized birds. We have modified the reported methods of purification of immunoglobulin from egg yolk, and thus yielded 90% purity of the protein. The modified method involves only two steps, such as removal of lipids from the diluted egg yolk by a freeze-thaw cycle and centrifugation, followed by gel filtration on Biogel P-150. The advantages are that the process is very simple, and from one egg, 100+/-20 mg of pure immunoglobulin is obtained. The antibodies are present in the egg for up to 100 days after the immunization. Thus, using small amounts of venom, a large quantity of the immunoglobulin is obtained in a sufficiently pure form. The antigen binding ability of the pure antibody is found good by the Ouchterlony's double diffusion experiment.