STIMULATION OF FIBRONECTIN PRODUCTION AND DEPOSITION BY CHICKEN GRANULOSA-CELLS IN-VITRO BY EPIDERMAL GROWTH-FACTOR AND TRANSFORMING GROWTH-FACTOR-ALPHA

Experiments were conducted in vitro to examine the effect of epidermal growth factor (EGF) and transforming growth factor a (TGF-alpha) on t he production of fibronectin (deposited, secreted into medium and cell -associated) by hen granulosa cells isolated from the largest (F-1; ab out 35 mm in diameter, mature) and third largest (F-3; 15-20 mm in dia meter) preovulatory follicles, as well as from a pool of immature smal l yellow follicles (6-8 mm in diameter). The cells were incubated in c ulture wells coated with type IV collagen or in wells without collagen coating, and the amounts of fibronectin produced were measured using a specific ELISA. The total amount of fibronectin produced by unstimul ated cells was greatest in wells containing F-1 cells and increased wi th time. The amount of fibronectin deposited by unstimulated cells was greatest in wells containing F-1 cells and was much higher in collage n-coated wells than in uncoated wells. Both EGF and TGF-a increased th e quantity of fibronectin deposited by granulosa cells in collagen-coa ted and uncoated wells. Fibronectin secreted into the medium by unstim ulated cells also increased with the stage of follicular maturation an d was enhanced by EGF and TGF-alpha. The quantity of cell-associated f ibronectin in granulosa cells in collagen-coated and uncoated wells wa s also increased by these growth factors. Type IV collagen did not hav e any appreciable effect on the amount of fibronectin present in the i ncubation medium or on cell-associated fibronectin. Because of its mar ked effect on deposited fibronectin, there were greater total quantiti es of fibronectin in culture wells coated with type IV collagen. These results demonstrate that EGF and TGF-ol stimulate the production and deposition of fibronectin by chicken granulosa cells. The results also suggest that in combination with collagen IV, these growth factors ca n regulate the formation of the extracellular matrix (for example, bas al lamina) of the hen ovarian follicle.