Bone morphogenetic protein 2 inhibits growth differentiation factor 8-induced cell signaling via upregulation of gremlin2 expression in human granulosa-lutein cells

Xiaoyan Luo,Peter C K Leung,Hsun-Ming Chang,Yuyin Yi,Yingpu Sun

doi:10.1186/s12958-021-00854-6

Abstract

BackgroundBone morphogenetic protein 2 (BMP2), growth differentiation factor 8 (GDF8) and their functional receptors are expressed in human ovarian follicles, and these two intrafollicular factors play essential roles in regulating follicle development and luteal function. As BMP antagonists, gremlin1 (GREM1) and gremlin2 (GREM2) suppress BMP signaling through blockage of ligand-receptor binding. However, whether BMP2 regulates the expression of GREM1 and GREM2 in follicular development remains to be determined.MethodsIn the present study, we investigated the effect of BMP2 on the expression of GREM1 and GREM2 and the underlying mechanisms in human granulosa-lutein (hGL) cells. An established immortalized human granulosa cell line (SVOG) and primary hGL cells were used as study models. The expression of GREM1 and GREM2 were examined following cell incubation with BMP2 at different concentrations and time courses. The TGF-β type I inhibitors (dorsomorphin, DMH-1 and SB431542) and small interfering RNAs targeting ALK2, ALK3, SMAD2/3, SMAD1/5/8 and SMAD4 were used to investigate the involvement of the SMAD-dependent pathway.ResultsOur results showed that BMP2 significantly increased the expression of GREM2 (but not GREM1) in a dose- and time-dependent manner. Using a dual inhibition approach combining kinase inhibitors and siRNA-mediated knockdown, we found that the BMP2-induced upregulation of GREM2 expression was mediated by the ALK2/3-SMAD1/5-SMAD4 signaling pathway. Moreover, we demonstrated that BMP2 pretreatment significantly attenuated the GDF8-induced phosphorylation of SMAD2 and SMAD3, and this suppressive effect was reversed by knocking down GREM2 expression.ConclusionsOur findings provide new insight into the molecular mechanisms by which BMP2 modulates the cellular activity induced by GDF8 through the upregulated expression of their antagonist (GREM2).

Highlights

Identified due to its pivotal role in bone formation and development, bone morphogenetic protein 2 (BMP2) was the first member of the Bone morphogenetic protein (BMP) subfamily to be discovered [1]
Bone morphogenetic protein 2 (BMP2) significantly increased the mRNA levels of GREM2 starting at 3 h, and the effect persisted until 24 h after treatment (Fig. 1D)
GREM2 mediates the suppressive effects of BMP2 on the growth differentiation factor 8 (GDF8)‐induced increases in phosphorylated SMAD2 and SMAD3 in SVOG cells Given that BMP2 upregulates the expression of GREM2, we aimed to investigate the functional role of this effect in human granulosalutein (hGL) cells

Summary

Introduction

Identified due to its pivotal role in bone formation and development, bone morphogenetic protein 2 (BMP2) was the first member of the BMP subfamily to be discovered [1]. BMP2 and its functional receptors are expressed in human ovarian follicles and the corpus luteum, and this intrafollicular factor plays an essential role in regulating follicle development and luteal function [2]. GREM1 and GREM2 are expressed in the ovaries of mice [11] and humans [24], and these two factors play functional roles in regulating embryological ovarian and follicular development, and several reproductive disorders, such as polycystic ovary syndrome [25], diminished ovarian reserve [26], endometriosis [27], and endometrial cancer [28]. Bone morphogenetic protein 2 (BMP2), growth differentiation factor 8 (GDF8) and their functional receptors are expressed in human ovarian follicles, and these two intrafollicular factors play essential roles in regulat‐ ing follicle development and luteal function. Whether BMP2 regulates the expression of GREM1 and GREM2 in follicular development remains to be determined

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