TRANSFORMING GROWTH-FACTOR-BETA-1 INDUCES MORPHOLOGICAL-CHANGES ACCOMPANIED BY EXTRACELLULAR-MATRIX RECONSTITUTION IN CULTURES OF AVIAN RETINAL PIGMENTED EPITHELIAL-CELLS

The mechanisms of cell differentiation have been extensively studied w ith an avian retinal pigmented epithelial cell (PEC) culture system. T ransforming growth factor-beta (TGF-Rho) has been reported to have sti mulatory or inhibitory effects on differentiation depending on tissue type. Although the mechanism by which TGF-beta exerts diverse effects is unknown, changes in the extracellular matrix (ECM) are believed to be related to the effects of TGF-beta. Therefore, the effects of TGF-b eta 1 on the cellular morphology and the distribution of ECM component s such as laminin, tenascin, fibronectin, and types I and IV collagens were investigated in confluent cultures of differentiated PECs during a period of 6 days. We found that differentiated PECs with polygonal morphology and pigmented granules changed to pleomorphic and less pigm ented cells 4 days after the addition of TGF-beta 1. These changes wer e preceded by changes in the distribution of ECM components, particula rly laminin and tenascin after 2 days. The effects of TGF-beta on the differentiation of PECs are discussed.