Sertoli cells contain a mitogenic polypeptide.

The seminiferous epithelium of the mouse testis contains a potent mitogen that induces DNA synthesis and cell division in cutures of confluent, quiescent BALB/c 3T3 cells. Homogenates of adult mouse seminiferous tubules, when added to 3T3 cells for 48 hr, produce a dose-dependent increase in DNA synthesis with half-maximal activity at 400 micrograms of protein per ml. Maximal stimulation causes a 70- to 100-fold increase in [methyl-3H]thymidine incorporation into DNA, a labeling of > 99% of 3T3 cell nuclei, and a doubling in cell number. The level of mitogenic activity in seminiferous tubules isolated from newborn mice is five times greater than that in tubules of adult mice. Furthermore, prepuberal Sertoli cells contain substantially greater levels of mitogenic activity than any other cell type purified from the seminiferous epithelium. A homogenate of prepuberal Sertoli cells induces half-maximal DNA synthesis at 20 micrograms of protein per ml. The mitogenic factor is sensitive to proteases and to heating at 100 degrees C for 2 min but not to dithiothreitol. Gel-filtration chromatography reveals that the factor is a polypeptide with a Mr of approximately 15,500. These observations provide evidence for the presence of a growth factor in the mammalian testis.