Characterization of mesonephric cells that migrate into the XY gonad during testis differentiation

In mouse fetal gonads, sex differentiation begins at 10.5-11.5 days postcoi tum (dpc). With XY gonads: of 12.5 dpc, cord-like structures are visible an d stromal cells migrate from adjacent mesonephros, unlike in XX gonads. How ever, the migrated mesonephric cells, except for the endothelial cells, hav e not been specifically identified because they have not expressed differen tiation markers over the course of organ coculture in previous experiments. In this study, we have for the first time succeeded in isolating only the mesonephric cells that migrate into the XY gonad from the mesonephros with alive and then cultured these cells in vitro through the use of an organ co culture system using EGFP-transgenic mice and a FAGS Vantage. The migrated and isolated cells were used for morphological and molecular characterizati on. The migrated mesonephric cells contained three cell forms; a sharp cell form, a round cell form, and a cluster-forming cell. The sharp cells have the characters of peritubular myoid cells. The round cells and cluster-form ing cells have the potential to differentiate into Leydig cells, as some of them are 3 beta -HSD-positive. In in vitro culture of migrated mesonephric cells, the cluster-forming cells proliferated well and then differentiated into round cells, suggesting that the cluster-forming cells may be stem or precursor cells for the round cells. Thus, our findings provide important information related to the migration and differentiation of migrated mesone phric cells in the XY gonad. (C) 2001 Academic Press.