TGFB1 and melanoma: We have also investigated the mode of action of the layered chondrocyte sheets, and we have suggested that chondrocyte sheets exert their ongoing regeneration effects in articular cartilage through the continuous secretion of humoral factors such as melanoma inhibitory activity (MIA), transforming growth factor β (TGF-β), and prostaglandin E2, which are important in cartilage regeneration21,22.