Importance of the Renin-Angiotensin-System in human granulosa lutein cells – RAS in granulosa cells

The Renin-Angiotensin system (RAS) has been suspected not only to influence the vascular tone but also to regulate angiogenesis. It was shown that Angiotensin II influences angiogenic factors such as vascular endothelial growth factor (VEGF). The most intense physiologic angiogenesis in adults occurs in luteal formation, which is further increased under human chorion gonadotropin (hCG). Recently, the presence of the RAS has been reported in the human corpus luteum. Since VEGF is regulated by hCG in the corpus luteum and since VEGF has also been shown to be regulated by Angiotensin II, we hypothesised that Angiotensin II actions as a physiological co-regulator to hCG. Therefore, performing RT-PCR and immunocytochemistry, we investigated whether human granulosa cells express RAS components. Furthermore, Angiotensin II dependent expression of VEGF as well as the influence of hCG on the RAS was examined using TaqMan-RealTime-PCR, ELISA, and Western blot analysis. We showed expression of hCG-receptor (LHR), VEGF, Angiotensinogen, ACE, AT1R, and AT2R in human granulosa lutein cells. Administration of Angiotensin II as well as hCG led to an significant increase of VEGF on both, transcript as well as protein level. However, stimulation with hCG decreased the Angiotensinogen/Angiotensin II level significantly, whereas expression of ACE and At1R was not affected. These findings show, that the RAS participates in the regulation of angiogenic gene regulation in human granulosa lutein cells, opening the intriguing possibility to explain the VEGF upregulation in human granulosa lutein cells via the hCG-dependent as well as the Angiotensin II-dependent pathway.