Study of the effect of luteinizing hormone (LH) in modulating anti-Müllerian hormone (AMH) pathway in human granulosa cells

Anti-Müllerian hormone (AMH) was initially described for its role in fetal sexual differentiation, but over the past two decades, its importance in adult reproductive physiology has also become increasingly evident. Alongside luteinizing hormone (LH), AMH plays a central role in female gonadal function and reproductive capacity. Secreted by granulosa cells, AMH acts during the initial phases of follicular development by modulating follicular sensitivity to gonadotropins. In contrast, LH primarily exerts its effects during the later stages of follicular maturation, promoting ovulation and luteinization through receptor-mediated signaling in both granulosa and theca cells. Clinical evidence from reproductive disorders such as polycystic ovary syndrome (PCOS) and premature ovarian failure suggests a possible functional interaction between the LH and AMH pathways. Yet, the molecular mechanisms driving this crosstalk are still not fully understood. Given this background, the study aimed to investigate the regulatory effect of LH on AMH signaling in primary human granulosa lutein cells (hGLCs) isolated from patients undergoing in vitro fertilization (IVF) treatments. The analysis focused on AMH expression, its type II receptor (AMHRII), SMAD1/5 phosphorylation, and the transcription of AMH-responsive genes: osterix (OSX) and matrix metallopeptidase 2 (MMP2). Quantitative real-time PCR (qPCR) analysis revealed that LH treatment led to a marked downregulation of AMHRII mRNA expression. This reduction was confirmed at the protein level through western blot (WB) and ELISA. In line with these results, AMH-induced SMAD1/5 phosphorylation, also evaluated by WB, was reduced. To investigate the downstream impact of LH on AMH activity, expression levels of OSX and MMP2 transcripts, typically upregulated by AMH, were examined and showed a reduction following LH exposure. Interestingly, this study demonstrated that LH treatment did not affect the amount of endogenously secreted AMH, suggesting that LH exerts its modulatory effect not by altering AMH production, but rather by reducing receptor availability and impairing signal transduction. Taken together, these findings reveal a functional interaction between LH and AMH in hGLCs, with LH appearing to negatively regulate AMH signaling. This crosstalk could be crucial for advancing research and developing new treatments for ovarian disorders commonly seen in reproductive medicine.