Tissue Regeneration in the Pores of Poly(lactide-co-glycolide)-Impregnated Wall of Expanded Polytetrafluoroethylene (ePTFE) Hybrid Grafts

Abstract

Understanding of relationship between pore properties and tissue regeneration of expanded polytetrafluoroethylene (ePTFE) is important in design of vascular tissue engineering. Tissue regeneration into a micron scale pore of the ePTFE wall was investigated by employing techniques of superficial surface modification of ePTFE, fabrication of the hybrid scaffold composed of biodegradable poly (lactide-co-glycolide) (PLGA) and ePTFE, and seeding of vascular cells on its lumen surface. The ePTFE was in advance transformed into a hybrid scaffold by sequential four steps of treatments such as chemical modification of ePTFE surfaces, impregnation of biodegradable PLGA polymer into its wall pores, and coatings of both PLGA polymer on the ePTFE lumen surface and collagens on the PLGA-coated lumen surface. The hybrid scaffold was in advance in vitro tissue-cultured with vascular smooth muscle for 12 weeks and stem cells for another 2 weeks on its collagen-coated lumen surface, thus obtaining an in vitro tissue-cultured scaffold. This in vitro tissue-cultured hybrid scaffold was implanted in a carotid artery of mongrel dog for 4 weeks. The morphologies of the hybrid grafts explanted from the artery were analyzed by light microscopy, scanning electron microscopy and transmission electron microscopy (TEM), focusing on tissue regeneration in the modified pores of ePTFE wall. They demonstrated migration of smooth muscle cells into the PLGA-impregnated/surface-modified pores of ePTFE wall along biodegradation of impregnated PLGA polymer, leading to tissue regeneration in its surface-modified pores. TEM results of the patent hybrid grafts showed both cell organelles and extracellular matrix of the regenerated media tissues in the pore channels of ePTFE wall with 20-30 mu m inter-nodal distances.