MicroRNA-99a is a novel regulator of KDM6B-mediated osteogenic differentiation of BMSCs.

Skeletal tissue originates from mesenchymal stem cells (MSCs) with differentiation potential into the osteoblast lineage regulated by essential transcriptional and post-transcriptional mechanisms. Recently, miRNAs and histone modifications have been identified as novel key regulators of osteogenic differentiation of MSCs. Here, we identified miR-99a and its target lysine (K)-specific demethylase 6B (KDM6B) gene as novel modulators of osteogenic differentiation of bone mesenchymal stem cells (BMSCs). Microarray profiling and further validation by quantitative real-time RT-PCR revealed that miR-99a was up-regulated during osteoblastic differentiation of BMSCs, and decreased in differentiated osteoblasts. Transfection of miR-99a mimics inhibited osteoblastic commitment and differentiation of BMSCs, whereas inhibition of miR-99a by inhibitors enhances these processes. KDM6B was determined as one of important targets of miR-99a, which was further confirmed by luciferase assay of 3'-UTR of KDM6B. Moreover, HOX gene level decreased after transfection of miR-99a mimics in BMSCs, which indicated that KDM6B is a bona fide target of miR-99a. Furthermore, in a model of in vivo bone regeneration, osteoblast-specific gain- and loss-of-function experiments performed using cranial bone defects revealed that miR-99a mimics-transfected BMSCs reduced bone formation, and conversely, miR-99a inhibitors-transfected BMSCs increased in vivo bone formation. Tissue-specific inhibition of miR-99a may be a potential novel therapeutic approach for enhancing BMSCs-based bone formation and regeneration.

Overexpression of MiR-335-5p Promotes Bone Formation and Regeneration in Mice.

MicroRNAs (miRNAs) and the Wnt signaling pathway play critical roles in regulating bone development and homeostasis. Our previous study revealed high expression of miR-335-5p in osteoblasts and hypertrophic chondrocytes in mouse embryos and the ability of miR-335-5p to promote osteogenic differentiation by downregulating Wnt antagonist Dickkopf-1 (DKK1). The purpose of this study was to investigate the effects of miR-335-5p constitutive overexpression on bone formation and regeneration in vivo. To that end, we generated a transgenic mouse line specifically overexpressing miR-335-5p in osteoblasts lineage by the osterix promoter and characterized its bone phenotype. Bone histomorphometry and µCT analysis revealed higher bone mass and increased parameters of bone formation in transgenic mice than in wild-type littermates. Increased bone mass in transgenic mice bones also correlated with enhanced expression of osteogenic differentiation markers. Upon osteogenic induction, bone marrow stromal cells (BMSCs) isolated from transgenic mice displayed higher mRNA expression of osteogenic markers than wild-type mice BMSCs cultures. Protein expression of Runx2 and Osx was also upregulated in BMSC cultures of transgenic mice upon osteogenic induction, whereas that of DKK1 was downregulated. Most important, BMSCs from transgenic mice were able to repair craniofacial bone defects as shown by µCT analysis, H&E staining, and osteocalcin (OCN) immunohistochemistry of newly formed bone in defects treated with BMSCs. Taken together, our results demonstrate constitutive overexpression of miR-335-5p driven by an osterix promoter in the osteoblast lineage induces osteogenic differentiation and bone formation in mice and support the potential application of miR-335-5p-modified BMSCs in craniofacial bone regeneration. © 2017 American Society for Bone and Mineral Research.

Epigenetic Modulation in Periodontitis: Interaction of Adiponectin and JMJD3-IRF4 Axis in Macrophages.

Emerging evidence suggests an important role for epigenetic mechanisms in modulating signals during macrophage polarization and inflammation. JMJD3, a JmjC family histone demethylase necessary for M2 polarization is also required for effective induction of multiple M1 genes by lipopolysaccharide (LPS). However, the effects of JMJD3 to inflammation in the context of obesity remains unknown. To address this deficiency, we firstly examined the expression of JMJD3 in macrophage isolated from bone marrow and adipose tissue of diet induced obesity (DIO) mice. The results indicated that JMJD3 was down-regulated in obesity. Adiponectin (APN), a factor secreted by adipose tissue which is down-regulated in obesity, functions to switch macrophage polarization from M1 to M2, thereby attenuating chronic inflammation. Intriguingly, our results indicated that APN contributed to JMJD3 up-regulation, reduced macrophage infiltration in obese adipose tissue, and abolished the up-regulation of JMJD3 in peritoneal macrophages isolated from DIO mice when challenged with Porphyromonas gingivalis LPS (pg.lps). To elucidate the interaction of APN and JMJD3 involved in macrophage transformation in the context of inflammation, we designed the loss and gain-function experiments of APN in vivo with APN(-/-) mice with experimental periodontitis and in vitro with macrophage isolated from APN(-/-) mice. For the first time, we found that APN can help to reduce periodontitis-related bone loss, modulate JMJD3 and IRF4 expression, and macrophage infiltration. Therefore, it can be inferred that APN may contribute to anti-inflammation macrophage polarization by regulating JMJD3 expression, which provides a basis for macrophage-centered epigenetic therapeutic strategies.