BACKGROUND:Human and rat ovarian granulosa cels in dominant folicles have the phenomenon of expressing stem cel characteristics. OBJECTIVE:To investigate the expression of stem cel-related factors in rat ovarian granulosa cels. METHODS: After the paraffin sections of rat ovarian tissue, immunohistochemical method was used to detect CD34, CD133, ABCG2/Bcrp1, Pou5f1/Oct-4 expressions. Granulosa cels culturedin vitro were harvested by folicular puncture method, and then the immunohistochemical method was used to detect the expression of FSHR receptor in order to identify the purity of granule cels. In the cultured granulosa cels, CD44 and C-Kit expressions were detected immunohistochemicaly, RT-PCR was used to detect ABCG2/Bcrp1, Pou5f1/Oct-4, Nanog gene expressions in ovarian tissue and granulosa cels. RESULTS AND CONCLUSION:Immunohistochemistry detection on paraffin sections showed that a part of ovarian granulosa cels expressed CD34, CD133, ABCG2/Bcrp1 and Pou5f1/Oct-4, and the expression of Pou5f1/Oct-4 protein gradualy increased in the development of ovarian folicles, significantly enhanced during the luteal phase, and then disappeared after the formation of corpus albicans, displaying a periodic expression characteristics. FSHR receptor positive identification rate of primary cels harvested by the foliclar puncture method was more than 95%. Granulosa cels culturedin vitrowere mainly long spindle-shaped or diamond, and some cels presented with aggregation growth and expressed CD44 and C-Kit. RT-PCR test results showed that there were no Nanog in the ovarian tissue and cultured granulosa cels, low expression of Pou5f1/Oct-4 in the ovarian tissue, strong expression of ABCG2/Bcrp1 in the ovarian tissue, weak expression of Pou5f1/Oct-4 in the cultured granulosa cels, and strong expression of ABCG2/Bcrp1 in the cultured granulosa cels. These findings suggest that a part of granulosa cels in the rat ovarian have the characteristics of stem cels.