G Protein-Coupled Estrogen Receptor Mediates Cell Proliferation through the cAMP/PKA/CREB Pathway in Murine Bone Marrow Mesenchymal Stem Cells.

Shu-Chun Chuang,Ya-Shuan Chou,Mei-Ling Ho,Chung-Hwan Chen,Je-Ken Chang

doi:10.3390/ijms21186490

Abstract

Estrogen is an important hormone to regulate skeletal physiology via estrogen receptors. The traditional estrogen receptors are ascribed to two nuclear estrogen receptors (ERs), ERα and ERβ. Moreover, G protein-coupled estrogen receptor-1 (GPER-1) was reported as a membrane receptor for estrogen in recent years. However, whether GPER-1 regulated osteogenic cell biology on skeletal system is still unclear. GPER-1 is expressed in growth plate abundantly before puberty but decreased abruptly since the very late stage of puberty in humans. It indicates GPER-1 might play an important role in skeletal growth regulation. GPER-1 expression has been confirmed in osteoblasts, osteocytes and chondrocytes, but its expression in mesenchymal stem cells (MSCs) has not been confirmed. In this study, we hypothesized that GPER-1 is expressed in bone MSCs (BMSC) and enhances BMSC proliferation. The cultured tibiae of neonatal rat and murine BMSCs were tested in our study. GPER-1-specific agonist (G-1) and antagonist (G-15), and GPER-1 siRNA (siGPER-1) were used to evaluate the downstream signaling pathway and cell proliferation. Our results revealed BrdU-positive cell counts were higher in cultured tibiae in the G-1 group. The G-1 also enhanced the cell viability and proliferation, whereas G-15 and siGPER-1 reduced these activities. The cAMP and phosphorylation of CREB were enhanced by G-1 but inhibited by G-15. We further demonstrated that GPER-1 mediates BMSC proliferation via the cAMP/PKA/p-CREB pathway and subsequently upregulates cell cycle regulators, cyclin D1/cyclin-dependent kinase (CDK) 6 and cyclin E1/CDK2 complex. The present study is the first to report that GPER-1 mediates BMSC proliferation. This finding indicates that GPER-1 mediated signaling positively regulates BMSC proliferation and may provide novel insights into addressing estrogen-mediated bone development.

Highlights

Estrogens play important physiological roles in skeletal systems
We examined whether G protein-coupled estrogen receptor-1 (GPER-1) promotes osteogenic cell proliferation in cultured tibias
In this study, we investigated whether GPER-1 mediates cell proliferation and studied the related molecular mechanism by using cultured tibia of neonatal rat and murine bone MSCs (BMSC)

Summary

Introduction

Estrogens play important physiological roles in skeletal systems. Bone is a dynamically remodeling organ and estrogen plays an important role in regulating bone remodeling [1,2,3,4,5]. Recent reports indicate that estrogen receptor mediation is required for osteogenesis in osteogenic lineage cells [4,6]. Recent studies have reported that G protein-coupled ER (GPER-1), known as G protein-coupled receptor 30, is a membrane receptor for estrogen that promotes estrogen-dependent activation via extranuclear signaling pathways [9,10]. GPER-1 expression has been reported in osteocytes, osteoclasts and osteoblasts [14,15] These findings suggest that non-genomic estrogen signaling via GPER-1 may exist in bone. BMSCs are known to be important for osteogenesis and bone formation [17]; it has not been reported whether GPER-1 plays a role in BMSCs. This study intends to investigate whether GPER-1 mediates BMSC proliferation and its molecular mechanism

Methods

Results

Conclusion