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Resveratrol (RES) is a natural polyphenolic compound with a broad range of physiological and pharmacological properties. Previous studies have shown that RES also plays an important role in protecting and promoting early bone metabolism and differentiation. The accumulation of cadmium (Cd), one of the world’s most poisonous substances, can inhibit skeletal growth and bone maturation, thus causing osteoporosis. However, whether RES can prevent the Cd-induced inhibition of osteogenic differentiation remains unknown. In this study, we found that RES promoted the early maturity of osteoblastic MC3T3-E1 cells, as demonstrated by the significantly increased mRNA and protein expression of a range of differentiation markers, including alkaline phosphatase (ALP), collagen 1 (COL1), bone morphogenetic protein-2 (BMP-2), and runt-related transcription factor 2 (RUNX2). In contrast, we found that cadmium chloride (CdCl2) inhibited the viability and osteogenic maturity of MC3T3-E1 cells. We also demonstrated that RES pretreatment for 30 min provided significant protection against Cd-induced apoptosis and attenuated the inhibition of osteogenic differentiation induced by Cd by modulating ERK1/2 and JNK signaling. In conclusion, our results indicate that RES is a potential femoral protectant that not only enhance the viability and early differentiation of osteoblasts, but also protect osteoblasts from cadmium damage.

Icaritin (ICT), a hydrolytic product of icariin from the genus Epimedium, has many indicated pharmacological and biological activities. Several studies have shown that ICT has potential osteoprotective effects, including stimulation of osteoblast differentiation and inhibition of osteoclast differentiation. However, the molecular mechanism for this anabolic action of ICT remains largely unknown. Here, we found that ICT could enhance MC3T3-E1 subclone 14 preosteoblastic cell differentiation associated with increased mRNA levels and protein expression of the differentiation markers alkaline phosphatase (ALP), type 1 collagen (COL1), osteocalcin (OC), osteoponin (OPN) and runt-related transcription factor 2 (RUNX2), and improved mineralization, confirmed by bone nodule formation and collagen synthesis. To characterize the underlying mechanisms, we examined the effect of ICT on estrogen receptor (ER) and mitogen-activated protein kinase (MAPK) signaling. ICT treatment induced p38 kinase and extracellular signal-regulated kinase 1/2 (ERK1/2) activation, but it demonstrated at the same time point no effect on activation of c-Jun N-terminal kinase (JNK). ER antagonist ICI182780, p38 antagonist SB203580 and ERK1/2 antagonist PD98059 markedly inhibited the ICT-induced the mRNA expression of ALP, COL1, OC and OPN. ICI182780 attenuated the ICT-induced phosphorylation of p38 and ERK1/2. These observations indicate a potential mechanism of osteogenic effects of ICT involving the ERK1/2 and p38 pathway activation through the ER.

Icariin (ICA) is a major active ingredient in Herba epimedii, which is commonly used as a Chinese herbal medicine for the treatment of osteoporosis. Previous studies have revealed that ICA exerted a protective effect against bone loss and increased bone regeneration; however, the association between ICA and estrogen receptor (ER) signaling remains unclear. The aim of the present study was to determine the effect of ICA on rat bone marrow stromal cells (rBMSCs). Cell Counting Kit‑8 assays were conducted to measure proliferation, alkaline phosphatase (ALP) activity was evaluated to assess osteoblast differentiation, and reverse transcription‑quantitative polymerase chain reaction as well as western blotting were performed to detect the expression of cellular and molecular markers of osteogenic or adipogenic differentiation. The results demonstrated that treatment of rBMSCs with 10‑6 M ICA stimulated rBMSC proliferation and ALP activity. Furthermore, ICA treatment increased the expression of the osteogenic markers runt‑related transcription factor 2, collagen type 1 and bone morphogenetic Protein 2; however, it also decreased the expression of the adipogenic differentiation markers peroxisome proliferator‑activated receptor gamma and CCAAT/enhancer‑binding protein α. Treatment of rBMSCs with ICI182780, an ER antagonist, blocked the effects of ICA. Taken together, these findings indicated that ICA may stimulate osteoblast differentiation and inhibit adipogenic differentiation via the activation of the ER signaling pathway. Therefore, ICA has the potential to serve as a therapeutic alternative for the prevention and treatment of osteoporosis.

Recently, several studies have indicated that circular RNAs (circRNAs) play significant roles in various disease; however, little is known about the chronology of estrogen receptor beta (ERβ) deficiency and altered circRNA expression, or their relationship with osteogenesis. Herein, we show through western-blot and quantitative real-time PCR assays, that when ERβ is silenced, the expression of osteogenesis-related proteins and mRNAs were down-regulated. We then performed RNA-Seq to analyze differential circRNA expression between the control and ERβ knockdown group. This analysis revealed that, 146 circRNAs were differentially expressed by fold-change≥2.0, p ≤ 0.05, and, among this group, 68 circRNAs were down-regulated, while 78 were up-regulated. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and PANTHER pathway analyses were performed to predict the function of these differentially expressed circRNAs. Finally, co-expressed targets gene, and circRNA-microRNA network were constructed for predicted miRNA sponges. This research suggested that ERβ may through 2:27713879|27755789/2:240822115|240867796-miR-328-5p-mRNA axis to regulate osteogenic differentiation.