GERM-CELL SERTOLI-CELL INTERACTIONS - REGULATION BY GERM-CELLS OF THESTAGE-SPECIFIC EXPRESSION OF CP-2 CATHEPSIN-L MESSENGER-RNA BY SERTOLI CELLS

CP-2/cathepsin L mRNA is expressed primarily by rat Sertoli cells with in stage VI-VIII seminiferous tubules. To test whether germ cells regu lated this expression, we examined if separating Sertoli cells from sp ecific germ cells affected expression of this transcript in Sertoli ce lls. First, Sertoli cells were isolated from adult (90-day-old) and im mature (25-day-old) rats and levels of this transcript measured immedi ately or after 1, 3 and 5 days in culture. Results demonstrated that i mmediately upon isolation, CP-2/cathepsin L mRNA levels were significa ntly higher in mature cells. However, after 1 day in culture, the leve ls of this transcript increased in immature cells and remained high in mature cells. We therefore conclude that in vivo, a subset of germ ce lls inhibit the expression of CP-2/cathepsin L mRNA by immature Sertol i cells. Second, to examine the effect of specific germ cells on CP-2/ cathepsin I mRNA expression, we exposed the testes of mature rats to 3 Gy of gamma-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 wit hout effect. However, when pachytene spermatocytes through step 14 spe rmatids were depleted, expression at stages VI-VIII was reduced by hal f and expression at stages IX-l was increased 14-fold. These changes r esulted in the loss of stage-specific expression of CP-2/cathepsin L m RNA by Sertoli cells. Finally, stage VI-VIII tubules, depleted primari ly in step 15-19 spermatids, had levels of CP-2/cathepsin L mRNA that were 60% of control. However, stage-specific expression of this transc ript was detected in these tubules. In contrast to what we noted with CP-2/cathepsin L mRNA, loss and restoration of germ cells had no effec t on Sertoli cell levels of SGP-2 mRNA, indicating that testicular irr adiation had no overall effect on Sertoli cell function. Taken togethe r, these data suggest that the stage-specific expression of the CP-2/c athepsin 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-V III. (C) 1995 Wiiey-Liss, Inc.