P-628 The role of Anti-Müllerian Hormone (AMH) on human osteoblast differentiation

Abstract Study question May AMH, an ovarian hormone belonging to the Transforming Growth Factor β superfamily (TGF-β), represent a possible candidate for use as a bone anabolic factor? Summary answer Our findings provided interesting clues on the stimulatory effects of AMH on mature osteoblasts expressing its specific receptor, the Anti-Müllerian Hormone Type-2 receptor (AMHRII). What is known already Impaired bone formation is a principal pathogenetic mechanism mediating bone fragility in osteoporosis. Several growth factors capable of inducing bone matrix apposition by increasing the number of osteoblast precursor cells or promoting the function of mature osteoblasts have been identified, including members of the TGF-β superfamily such as BMPs. However, their clinical use is limited due to their pleiotropic extraskeletal effects. Anti-Müllerian Hormone (AMH) is a member of the TGF-β superfamily whose role in bone tissues has never been investigated. To date, AMH functions and the expression of its specific receptor are mainly limited to the reproductive organs. Study design, size, duration We performed in vitro studies on Human Osteoblasts (HOb) to evaluate the expression and the functionality of AMH receptor type-2 and investigate the effects of recombinant AMH (rhAMH) exposure on osteogenic gene expression and osteoblast functions. Participants/materials, setting, methods RT-PCR, real-time PCR and Western blotting analyses were performed in Hob cells cultured both in the presence and in the absence of 100 ng/mL rhAMH to evaluate the effect of AMH exposure on osteoblast differentiation. Alizarin red staining was performed after 14 days of treatment with 100 ng/mL rhAMH to assess the mineralized nodule formation. Main results and the role of chance Our study revealed the presence of a strong mRNA and protein expression of AMHRII in HOb cells, thus indicating that osteoblasts may represent a specific target for exogenous AMH treatment. We also observed that rhAMH exposure increased SMAD 1/5 protein levels, demonstrating that the binding of AMHRII by AMH was able to activate the SMAD-mediated AMH signalling pathway. Interestingly, we also observed that AMH treatment upregulates mRNA levels of crucial osteoblastic transcription factors such as RUNX2 and OSX and extracellular matrix proteins including OPN and OC. Consistently, the prolonged exposure to AMH also promoted matrix mineralization in HOb cells, as demonstrated by both increased ALP gene expression and the greater amount of mineralized nodules observed in AMH-treated osteoblasts compared to untreated controls. Limitations, reasons for caution The study was conducted only in HOb cells. Additional functional studies are needed to investigate the action mechanism of AMH in the other bone cells to understand the mechanisms by which AMH may influence bone homeostasis and pave the way for subsequent in vivo studies. Wider implications of the findings This study may have translation value in opening the perspective that AMH may be an effective candidate to counteract bone loss in osteoporotic patients by developing a new therapy selectively targeting osteoblast with minimal off-target effect. Trial registration number Not Applicable