The basic research on functionalization of the natural polysaccharide and application to biomedical materials.

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In this investigation, we have examined the control of cell specific functions (proliferation and differentiation) of the hard tissue cells (bone and chondrocyte) by polyelectrolyte complex (PEC), which are composed of polysaccharides.Osteoblasts cultured on PEC containing sulfated polysaccharide (SPEC) were proliferated similar to tissue culture dish (TCD) and exhibited spreading form. On the other hand, the proliferation of cell cultured on PEG containing carboxymethylated polysaccharide (OPEC) coated dishes was slower than those on TCD and exhibited aggregate form. Expression of ALPase activity and deposition of calcium, which were initial differentiation markers of calcification, were observed mainly at the part of cell aggregate. Further, expression of mRNA of osteoblastic differentiation markers (osteocalcin and osteopontin) were observed on OPEC earlier than on SPEC and TCD. N-cadherin, cell-cell adhesion protein, expression was strong and localized at the cell-cell interfaces in the cell aggregates.Chondrocyte (ATDC5) cultured on SPEC grew well in the similar manner to TCD with spreading form. On the other hand, the growth of ATDC5 on OPEC was remarkably suppressed and exhibited cell aggregate form. The sizes of these aggregates were made bigger with time. These phenomena are well coincident with the culture of osteoblasts on these PECs. Secretion of chondrocyte matrix and expression of mRNA of typeII collagen were promoted on the OPEC.These results suggested that the cell functions, proliferation and differentiation, are mainly controlled by the chemical structures of anionic polysaccharides ; the existence of carboxylic acid residues induces the differentiation and sulfonic acid residues promotes the proliferation of cells.In conclusion, polysaccharides-type PEC are excellent biomaterials for hard tissue cell culture.