Sertoli cells contain a mitogenic polypeptide.

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Abstract
The seminiferous epithelium of the mouse testis contains a potent mitogen that induces DNA synthesis and cell division in cultures of confluent, quiescent mouse fibroblast BALB/c 3T3 cells. Homogenates of adult mouse seminiferous tubules, when added to 3T3 cells for 48 h, produce a dose-dependent increase in DNA synthesis with half-maximal activity at 400 .mu.g of protein/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 5 times greater than that in tubules of adult mice. 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 .mu.g of protein/ml. The mitogenic factor is sensitive to proteases and to heating at 100.degree. C for 2 min but not to dithiothreitol. Gel-filtration chromatography reveals that the factor is a polypeptide with a MW of 15,500. These observations provide evidence for the presence of a growth factor in the mammalian testis.