RESUMEN
<p><b>Objective</b>To explore the feasibility of inducing human umbilical cord mesenchymal stem cells (HUMSCs) to differentiate into Leydig cells in the interstitial tissue of the rat testis.</p><p><b>METHODS</b>HUMSCs were obtained by tissue blocks culture attachment and their purity and multi-lineage differentiation ability were verified by flow cytometry and chondrogenic/adipogenic/osteogenic differentiation. Then the HUMSCs were marked by CM-Dil and transplanted into the interstitial tissue of the rat testis. At 4 and 8 weeks after transplantation, the survival and differentiation status of the HUMSCs were observed by immunofluorescence staining and flow cytometry. The suspension of the rat Leydig cells was obtained at 8 weeks for determining the expression of the Leydig cell marker 3β-HSD in the HUMSCs, the cells labeled with CM-Dil were sorted and cultured, and the medium collected after 3 days of culture for measurement of the testosterone level.</p><p><b>RESULTS</b>The expression of the Leydig cell marker CYPllal was not observed in the HUMSCs at 4 weeks but found at 8 weeks after transplantation and the differentiation rate of 3β-HSD was about 14.5% at 8 weeks. CM-Dil labeled cells survived after sorting and testosterone was detected in the medium.</p><p><b>CONCLUSIONS</b>HUMSCs are likely to differentiate into Leydig cells in the interstitium of the rat testis.</p>