Cell-substratum and cell-cell interactions promote testicular peritubular myoid cell histotypic expression in vitro

Peritubular cells, prepared from seminiferous tubules from testes of 20-day-old-rats, were seeded onto different substrata and cultured under varying conditions. When plated onto polystyrene or glass surfaces, peritubular cells assumed a typical fibroblast-like cell shape and cell association pattern, together with a fibroblast-like migration behavior. They maintained high rates of proliferation even after achieving confluency. In contrast, when peritubular cells were plated onto a seminiferous tubule biomatrix (ST-biomatrix) surface, they spread to form a continuous cell layer having a myoepithelioid histotype similar to that of peritubular myoid cells in the intact seminiferous tubule. The characteristics of the myoepithelioid histotype described include a squamous, polyhedral cell shape; a cobblestone-like cell association pattern, with closely apposing or slightly overlapping cell borders, and a very low mitotic index. When peritubular cells were plated onto laminin, collagen, fibronectin, heparin, or a liver biomatrix, a fibroblast-like pattern resulted, indicating that ECM components listed and liver biomatrix are unable to substitute for ST-biomatrix in maintaining normal myoepithelioid characteristics in vitro. In cocultures of Sertoli cells plated on top of peritubular cells, the peritubular cells directly in contact with Sertoli cell aggregates developed a myoepithelioid histotype, whereas peritubular cells in regions not in direct contact had a fibroblast-like histotype. The data are discussed in relation to the possible role of cell-cell interactions, and cell-substratum interactions, in the acquisition and stabilization of the histotype of peritubular cells in the seminiferous tubule during development.