Effect of GGCX on the differentiation function of osteoporosis bone marrow mesenchymal stem cells through regulating TGFβ/smad signaling pathway

Q.-L. Wang, H.-F. Li, D.-P. Wang, Z.-Y. Liu, W.-W. Xiao, L.-L. Xu, S. Yu

Department of Endocrinology, The Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, Shandong, China. wameiwen81@yeah.net

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• Stem Cells

OBJECTIVE: Osteoporosis (OP) has a high incidence and can be found in multiple age groups. The bone marrow mesenchymal stem cells (BMSCs) have the potential for self-renewal and multi-directional differentiation, which are often used for investigating the differentiation function of osteoporosis bone marrow mesenchymal stem cells. γ-glutamyl carboxylase (GGCX) is a carboxylase-related carboxylase and was observed to be abnormally expressed in osteoarthritis. However, the role and related mechanisms of GGCX in OP have not been fully elucidated. This work aimed to evaluate the effect of GGCX on the differentiation function of BMSCs.

PATIENTS AND METHODS: Sprague-Dawley rats were randomly divided into the OP group prepared by ovariectomy and sham group. GGCX expression was tested by enzyme-linked immunosorbent assay (ELISA). BMSCs were isolated from OP rats and transfected with pcDNA-GGCX plasmids. BMSC proliferation was detected by tetrazolium salt colorimetry (MTT) assay. The osteogenic and adipogenic differentiation of BMSCs was analyzed by alizarin red staining and oil red O staining. The ALP activity was determined by alkaline phosphatase (ALP) activity colorimetric assay. Real time-PCR was used to test the expressions of osteogenesis-related genes RUNX2 and OPN mRNA. Western blot was adopted to assess the TGFβ/smad signaling pathway activity.

RESULTS: GGCX expression was significantly decreased in the serum of OP rats compared with the sham group (p < 0.05). The transfection of pcDNA-GGCX plasmid significantly promoted BMSC cell proliferation, increased calcified nodule formation, inhibited adipogenic differentiation, enhanced ALP activity, elevated RUNX2, and OPN mRNA expressions, and upregulated TGFβ1, Smad2, and Smad7 expressions (p < 0.05).

CONCLUSIONS: GGCX secretion is reduced in osteoporosis. GGCX can regulate osteoporosis via promoting the TGFβ/smad signaling pathway, facilitating BMSCs osteogenic differentiation, and inhibiting BMSCs adipogenic differentiation.

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