No abstract

The incidence of thrombogenesis and occlusion of cardiovascular implants is likely to be reduced by endothelial cell (EC) growth promotion on biomaterials used for device fabrication. However, proper signaling between the matrix proteins deposited on the device surface and the cells grown on it is a prime requirement for growth and function. It was demonstrated earlier that a composition of matrix proteins that include fibrin, fibronectin, gelatin, and growth factors maintain a steady proliferation potential and prolong the survival of endothelial cells in vitro. In this study, assessment of the same matrix to prevent EC from dedifferentiation during in vitro culture and to promote endothelialization of biomaterials used for fabrication of cardiovascular implants is carried out. Up/down regulation of m-RNA expression for a prothrombotic molecule-plasminogen activator inhibitor (PAI), and two antithrombotic molecules- nitric oxide synthetase (eNOS) and tissue plasminogen activator (t-PA) are chosen as the indicators of cell dedifferentiation during cell culture and passaging. Immunostaining for vinculin and actin demonstrated that composite coating on biomaterials improves focal adhesion and cytoskeletal organization that increases the quality of EC grown on it. EC proliferation, measured by (3)H-thymidine uptake, on all bare materials was poor and high incidence of cell apoptosis was noticed within 72 h in culture, whereas once coated with composite all materials showed good proliferation and survival. The results suggest that the designed composition of biomimetic adhesive proteins and growth factors is suitable for EC growth, survival, and functional integrity, thus making it suitable for cardiovascular tissue engineering that requires in vitro EC culture.

Coronary stents that are developed for use with balloon angioplasty are known to cause acute occlusion and long-term stenosis. It is likely that a controlled release of drugs at the site of stent implantation might inhibit the proliferation of vascular smooth muscle cells (VSMC) and reduce restenosis. However, if the drug is necrotic and affects cell survival near the implant, it may interrupt the local tissue regeneration. Different methods have been used for the immobilization of drugs with stents to get an effective concentration that inhibits cell proliferation. The objective of this study is to assess the effectiveness of Paclitaxel-loaded stents by immobilization with a biodegradable polymer, to inhibit cell proliferation. The cells used for the evaluation are human umbilical vein endothelial cells (HUVEC) and the proliferation rate of these cells on the drug-coated stent is compared against an uncoated stent for a 72-h period. Evaluations were also made to differentiate between cell apoptosis and necrosis to prove that the drug released is not deleterious to the surrounding tissue. While a similar initial cell adhesion is observed in bare and coated stents, the proliferation of HUVEC is negligible when grown on a drug-coated stent (p < 0.001). By specific staining techniques, the cells on the drug-coated stents are found to be apoptotic and not necrotic, throughout the evaluation period. In vitro leukocyte adhesion and platelet deposition on the drug-coated stents are found to be low when they are exposed to human blood and platelet-rich plasma (PRP), suggesting that the coated stents may not be thrombogenic in vivo. Therefore, drug coating of stents using the described technique may have a considerable promise for the prevention of neointimal proliferation, restenosis, and associated failure of angioplasty.

The highly organized histological architecture of the vascular wall and the specialized cellular phenotypes are perturbed in conditions such as atherosclerosis, restenosis, and hypertension. Alterations of endothelial cell (EC) phenotype in cardiovascular diseases (CVDs) as an effect of alteration of extracellular matrix (ECM) composition have not been well understood. In vitro study of EC phenotype is limited because they tend to dedifferentiate in subcultures. The objective of this study was to use in vitro cell culture on a biomimetic matrix model to characterize phenotype of human saphenous vein endothelial cells (HSVECs) harvested from CVD patients. Parameters studied were mRNA expression and synthesis of von Willebrand factor (vWF), plasminogen activation inhibitor (PAI), tissue plasminogen activator (t-PA), and endothelial nitric oxide synthetase (eNOS). Proliferation and apoptosis of HSVEC cultures obtained from eight different patients were compared on two matrices until passage 12. In early passages, both the prothombotic molecules vWF and PAI were overexpressed, whereas the antithrombotic molecules t-PA and eNOS were underexpressed. With increase in passage number, low expression of prothrombotic molecules and high expression of antithrombotic molecules were seen in cells on the model matrix. But when cells were grown on conventional gelatin-coated polystyrene, expression of prothrombotic molecules amplified further and antithrombotic molecules lessened with the progression of passages. On the model matrix HSVECs showed good proliferation rate and survival through several passages. It is demonstrated that matrix composition can influence switching of EC phenotypes into pro/antithrombotic states. This matrix model may be suitable to study the effect of exogenous factors on EC dysfunction with respect to CVD.