Low-dose IL-34 has no effect on osteoclastogenesis but promotes osteogenesis of hBMSCs partly via activation of the PI3K/AKT and ERK signaling pathways

• Published in: Stem cell research & therapy Vol. 12; no. 1; p. 268
• Main Authors: Xu, Jianxiang, Fu, Lifeng, Bai, Jinwu, Zhong, Huiming, Kuang, Zhihui, Zhou, Chengwei, Hu, Bin, Ni, Licheng, Ying, Li, Chen, Erman, Zhang, Wei, Wu, Jiaqi, Xue, Deting, Li, Weixu, Pan, Zhijun
• Format: Journal Article
• Language: English
• Published: England BioMed Central 04-05-2021; BMC
• Subjects: 1-Phosphatidylinositol 3-kinase; Adipocytes; AKT protein; Antibodies; Bone healing; Bone marrow; Cholecystokinin; Cytokines; Dosage; Extracellular signal-regulated kinase; Fractures; Gene expression; Growth factors; hBMSCs; Inflammation; Kinases; Ligands; Low-dose IL-34; mBMMs; Mesenchyme; Microenvironments; Osteoblastogenesis; Osteoclastogenesis; Osteogenesis; Osteoporosis; Osteotomy; Ovariectomy; Phosphatase; Signal transduction; Stem cell transplantation; Stem cells; Western blotting; United States > US; China; Japan; Osteoclastogenesis; mBMMs; Osteoblastogenesis; Low-dose IL-34; hBMSCs
• ISSN: 1757-6512; 1757-6512
• DOI: 10.1186/s13287-021-02263-3

Inflammatory microenvironment is significant to the differentiation and function of mesenchymal stem cells (MSCs). It evidentially influences the osteoblastogenesis of MSCs. IL-34, a newly discovered cytokine, playing a key role in metabolism. However, the research on its functional role in the osteogenesis of MSCs was rarely reported. Here, we described the regulatory effects of low-dose IL-34 on both osteoblastogenesis and osteoclastogenesis.
We performed the osteogenic effects of hBMSCs by exogenous and overexpressed IL-34 in vitro, so were the osteoclastogenesis effects of mBMMs by extracellular IL-34. CCK-8 was used to assess the effect of IL-34 on the viability of hBMSCs and mBMMs. ALP, ARS, and TRAP staining was used to evaluate ALP activity, mineral deposition, and osteoclastogenesis, respectively. qRT-PCR and Western blotting analysis were performed to detect the expression of target genes and proteins. ELISA was used to evaluate the concentrations of IL-34. In vivo, a rat tibial osteotomy model and an OVX model were established. Radiographic analysis and histological evaluation were performed to confirm the therapeutic effects of IL-34 in fracture healing and osteoporosis. Statistical differences were evaluated by two-tailed Student's t test, one-way ANOVA with Bonferroni's post hoc test, and two-way ANOVA with Bonferroni multiple comparisons post hoc test in the comparison of 2 groups, more than 2 groups, and different time points of treated groups, respectively.
Promoted osteoblastogenesis of hBMSCs was observed after treated by exogenous or overexpressed IL-34 in vitro, confirmed by increased mineral deposits and ALP activity. Furthermore, exogenous or overexpressed IL-34 enhanced the expression of p-AKT and p-ERK. The specific AKT and ERK signaling pathway inhibitors suppressed the enhancement of osteoblastogenesis induced by IL-34. In a rat tibial osteotomy model, imaging and histological analyses testified the local injection of exogenous IL-34 improved bone healing. However, the additional IL-34 has no influence on both osteoclastogenesis of mBMMs in vitro and osteoporosis of OVX model of rat in vivo.
Collectively, our study demonstrate that low-dose IL-34 regulates osteogenesis of hBMSCs partly via the PIK/AKT and ERK signaling pathway and enhances fracture healing, with neither promoting nor preventing osteoclastogenesis in vitro and osteoporosis in vivo.