Germ cell‐sertoli cell interactions: Regulation by germ cells of the stage‐specific expression of CP‐2/cathepsin LmRNA by sertoli cells

CP‐2/cathepsin LmRNA is expressed primarily by rat Sertoli cells within stage VI–VIII seminiferous tubules. To test whether germ cells regulated this expression, we examined if separating Sertoli cells from specific germ cells affected expression of this transcript in Sertoli cells. First, Sertoli cells were isolated from adult (90‐day‐old) and immature (25‐day‐old) rats and levels of this transcript measured immediately or after 1, 3 and 5 days in culture. Results demonstrated that immediately upon isolation, CP‐2/cathepsin LmRNA levels were significantly higher in mature cells. However, after 1 day in culture, the levels of this transcript increased in immature cells and remained high in mature cells. We therefore conclude that in vivo, a subset of germ cells inhibit the expression of CP‐2/cathepsin LmRNA by immature Sertoli cells. Second, to examine the effect of specific germ cells on CP‐2/cathepsin LmRNA expression, we exposed the testes of mature rats to 3 Gy of γ‐radiation and analyzed stage‐specific expression of this transcript at varying times during maturation depletion and subsequent germ cell restoration. Loss of spermatogonia or spermatocytes was without effect. However, when pachytene spermatocytes through step 14 spermatids were depleted, expression at stages VI–VIII was reduced by half and expression at stages IX‐I was increased 14‐fold. These changes resulted in the loss of stage‐specific expression of CP‐2/cathepsin LmRNA by Sertoli cells. Finally, stage VI–VIII tubules, depleted primarily in step 15–19 spermatids, had levels of CP‐2/cathepsin LmRNA that were 60% of control. However, stage‐specific expression of this transcriot was detected in these tubules. In contrast to whai we noted with CP‐2/cathepsin LmRNA, loss and restoration of germ cells had no effect on Sertoli cell levels of SGP‐2 mRNA, indicating that testicular irradiation had no Overall effect on Sertoli cell function Taken togetherr these data suggest that the stage‐specific expression of the CP‐2/ cathepsin L gene results from the sequential stimulation and inhibition of Sertoli cells by germ cells, that pachytene spermatocytes through step 14 spermatids are required for this stage‐specific expression and that step 18 and 19 spermatids amplify this expression at stages VI–VIII. © 1995 Wiley‐Liss, Inc.