TRANSPORT PHENOMENA IN ENGINEERED CARTILAGE WITH TISSUE DEVELOPMENT IN AGAROSE GEL

摘要

The primary function of articular cartilage is to absorb impact in life cycle, however once cartilage is damaged, it has poor ability to recover. And then transplant of engineered cartilage tissue is considered as the promising measure for the therapeutic approach, since it is free from immune reaction. Articular cartilage consists of 2% chondrocyte and 98% extra-cellar-matrix (ECM), which is made by chondrocyte's metabolic action. ECM shows high osmotic pressure, mainly due to highly negative charged proteoglycan, and hence retain large amount of water. The most characteristic nature of cartilage tissue is avascularity, hence materials, such as nutrition and wastes, are transported from connective tissue or periosteum by mainly diffusion. One of the most significant key factors to control the development of the engineered cartilage is this transport phenomenon, which is, on the other hand, strongly affected by the tissue development. Therefore we study transport processes as ECM development. In this study, we selected ultra-low gelling temperature agarose gel, of different types and weight percent, as the scaffold, and chondrocytes were isolated from the bovine metacarpal-phalangeal joint. Engineered cartilage was obtained by incubating cell-agarose compounds for ECM to be produced. Engineered cartilage tissue specimens were soaked with fluorescent labeled dextran of prescribed molecular weight to observe the diffusion transport process. We evaluated diffusion coefficients by two different methods, namely, global observation in specimen by using flow chamber and local observation diffusion using FRAP method. We compare coefficients of dextran molecules both in engineered cartilage and cell-free agarose gel. First we investigate the effects of tissue development on diffusion coefficients. We observe the effects of incubation periods on the diffusion coefficients of engineered cartilage. And then we investigate the charge effects on the transport phenomena, by comparing the transport processes of charged and uncharged dextran. We also investigate the effects of scaffold type on tissue development.