LIMB BUD MESENCHYME PERMITS SEMINIFEROUS CORD FORMATION IN THE MOUSE FETAL TESTIS BUT SUBSEQUENT TESTOSTERONE OUTPUT IS MARKEDLY AFFECTED BY THE SEX OF THE DONOR STROMAL TISSUE

Mesonephric stromal cells have previously been shown to migrate into t he genital ridge and to be necessary for seminiferous cord formation i n organ culture. Here, we asked whether there is a specific requiremen t for mesonephric stromal cells or whether another source of mesonephr ic stromal cells can be substituted. Hindlimb buds were immersed in a vital stain and then grafted to male gonad primordia and cultured for 96 hr. Immunocytochemical staining of laminin was used to identify sem iniferous cord formation. For Sertoli and Leydig cell differentiation, Mullerian inhibiting substance and Delta 5-3 beta-hydroxysteroid dehy drogenase were used, respectively. Testosterone secreted into the cult ure medium was assessed by radioimmunoanalysis. It was found that hind limb stromal cells, like mesonephric stromal cells, migrate into the g enital ridge and allow seminiferous cord formation. These results indi cate that mesonephric stromal cells are not specifically required for seminiferous cord formation in the mouse fetal gonad. Furthermore, alt hough Sertoli and Leydig cells differentiate in the gonads grafted to hindlimbs from either male or female embryos, testosterone production was considerably higher with hindlimbs from males. A similar stromal s ex effect on subsequent testosterone output was also seen with mesonep hric stromal cells. (C) 1995 Academic Press, Inc.