Abstract
Basement membranes are thin extracellular matrices which contact epithelial cells and promote their adhesion, migration, differentiation, and morphogenesis. These matrices are composed of collagen IV, heparan sulfate proteoglycan, laminin, and entactin as well as other minor components. Sertoli cells, like most epithelial cells, are in contact at their basal surface with a basement membrane. When cultured within three-dimensional basement membrane gels (Matrigel), Sertoli cells reorganize into cords that resemble testicular seminiferous cords found in the in vivo differentiating testis. Anti-laminin and anti-entactin antisera inhibit this cord morphogenesis by Sertoli cells whereas antisera against type IV and type I collagen, heparan sulfate proteoglycan, fibronectin, and preimmune sera had no effect. The RGD (RGDS-NH2) sequence, found in the cell binding domain of the integrin family of cell adhesion molecules as well as in the A chain of laminin and in entactin, effectively inhibited Sertoli cell cord formation at a concentration of 1.0 mg/ml but was unable to prevent Sertoli cell attachment at concentrations as high as 2.0 mg/ml. A synthetic pentapeptide from a cell-binding domain of the B1 chain of laminin, YIGSR-NH2, inhibited cord formation at a concentration of 0.25 mg/ml, but Sertoli cells were still adherent to the basement membrane matrix. At concentrations greater than 0.50 mg/ml, Sertoli cells detached. Antiserum against the YIGSR-NH2-containing sequence was also effective in inhibiting cord formation by Sertoli cells. Ligand (YIGSR-NH2 peptide) blot analysis of Sertoli cell lysates revealed an interaction with a major band at 60 kDa and with minor bands at 39 and 127 kDa. Furthermore, in Western blot analysis the anti-67-kDa laminin-binding protein antibody recognized a 59- to 60-kDa protein in Sertoli cells. The data indicate that laminin is involved in both Sertoli cell attachment and migration during formation of histotypic cord structures by these cells in culture. Two separate laminin cell-binding domains appear to be involved in Sertoli cell cord morphogenesis in vitro and are likely to participate in the formation of seminiferous cords in vivo.