Germ cell binding to rat Sertoli cells in vitro.

The interaction between male germ cells and Sertoli cells was studied in vitro by co-incubation experiments using isolated rat germ cells and primary cultures of Sertoli cells made germ cell-free by the differential sensitivity of germ cells to hypotonic shock. The germ cell/Sertoli cell interaction was examined morphologically with phase-contrast and scanning electron microscopy and then quantified by measuring radioactivity bound to Sertoli cell cultures after co-incubation with added [3H]leucine-labeled germ cells. Germ cell binding to Sertoli cell cultures was the result of specific adhesion between these two cell types, and several features of this specific adhesion were observed. First, germ cells adhered to Sertoli cell cultures under conditions during which spleen cells and red blood cells did not. Second, germ cells had a greater affinity for Sertoli cell cultures than they had for cultures of testicular peritubular cells or cerebellar astrocytes. Third, germ cells fixed with paraformaldehyde adhered to live Sertoli cultures while similarly fixed spleen cells adhered less tightly. Neither live nor paraformaldehyde-fixed germ cells adhered to fixed Sertoli cell cultures. Fourth, germ cell binding to Sertoli cell cultures was not immediate but increased steadily and approached a maximum at 4 h of co-incubation. Saturation of germ cell binding to Sertoli cell cultures occurred when more than 4200 germ cells were added per mm2 of Sertoli cell culture surface. Finally, germ cell binding to Sertoli cell cultures was eliminated when co-incubation was performed on ice. Based on these observations, we concluded that germ cell adhesion to Sertoli cells was specific, temperature-dependent, and required a viable Sertoli cell but not necessarily a viable germ cell. These results have important implications for understanding the complex interaction between Sertoli cells and germ cells within the seminiferous tubule and in the design of future experiments probing details of this interaction.