CK1ε drives osteogenic differentiation of bone marrow mesenchymal stem cells via activating Wnt/ß-catenin pathway.

The treatment of bone defects is a difficult problem in orthopedics. At present, the treatment mainly relies on autologous or allogeneic bone transplantation, which may lead to some complications such as foreign body rejection, local infection, pain, or numbness at the bone donor site. Local injection of conservative therapy to treat bone defects is one of the research hotspots at present. Bone marrow mesenchymal stem cells (BMSCs) can self-renew, significantly proliferate, and differentiate into various types of cells. Although it has been reported that CK1ε could mediate the Wnt/ß-catenin pathway, leading to the development of the diseases, whether CK1ε plays a role in bone regeneration through the Wnt/ß-catenin pathway has rarely been reported. The purpose of this study was to investigate whether CK1ε was involved in the osteogenic differentiation (OD) of BMSCs through the Wnt/ß-catenin pathway and explore the mechanism. We used quantitative reverse transcription-polymerase chain reaction (qRT-qPCR), Western blots, immunofluorescence, alkaline phosphatase, and alizarin red staining to detect the effect of CK1ε on the OD of BMSCs and the Wnt/ß-catenin signaling pathway. CK1ε was highly expressed in BMSCs with OD, and our study further demonstrated that CK1ε might promote the OD of BMSCs by activating DLV2 phosphorylation, initiating Wnt signaling downstream, and activating ß-catenin nuclear transfer. In addition, by locally injecting a CK1ε-carrying adeno-associated virus (AAV5- CK1ε) into a femoral condyle defect rat model, the overexpression of CK1ε significantly promoted bone repair. Our data show that CK1ε was involved in the regulation of OD by mediating Wnt/ß-catenin. This may provide a new strategy for the treatment of bone defects.

Resistin targets TAZ to promote osteogenic differentiation through PI3K/AKT/mTOR pathway.

Osteogenic differentiation (OD) of bone marrow mesenchymal stem cells (BMSCs) contributes significantly to the regeneration of bone defects. Resistin, an adipose tissue-specific secretory factor, has been shown to involve many different functions, including metabolism, inflammation, cancer, and bone remodeling. However, the effects and mechanisms of resistin on OD of BMSCs remain unclear. Herein, we demonstrated that resistin was highly expressed in BMSCs with OD. Upregulation of resistin contributed to the progression of OD of BMSCs by activating PI3K/AKT/mTOR signaling pathway. In addition, resistin facilitated OD by targeting transcriptional co-activator with PDZ-binding motif (TAZ). In a rat femoral condyle bone defect model, local injection of resistin significantly promoted bone repair and improved bone formation. This work contributes to better understanding the mechanism of resistin directly involved in the OD and might provide a new therapeutic strategy for bone defect regeneration.

KLF4, negatively regulated by miR-7, suppresses osteoarthritis development via activating TGF-ß1 signaling.

Osteoarthritis (OA) is a chronic degenerative disease which seriously affects the patients' daily activities and quality of life. In our previous findings, we demonstrated that overexpression of miR-7 was found in OA and promoted OA development. Its exact mechanism remains unclear. Herein, we confirmed that KLF4 was the target gene of miR-7 and KLF4 was down-regulated in human OA tissues and OA chondrocyte. KLF4 was negatively modulated by miR-7 via dual luciferase reporter assay. Cartilage-specific genes (SOX9, COL2A1, RUNX2, MMP13) are crucial regulators in cartilage degeneration. Through qRT-PCR and western blot, we observed that KLF4 overexpression could increase the expression of SOX9 and COL2A1, decrease RUNX2 and MMP13. In the meanwhile, miR-7 was proven to regulate the expression of the above cartilage-specific genes by targeting KLF4, which demonstrated KLF4 could prevent OA development. Subsequently, KLF4 also activated TGF-ß1 signaling pathway, thereby affecting OA progression. Excessive KLF4 could up-regulate TGF-ß1 and p-Smad2/3 level, and Smad4 level was prevented in OA chondrocytes, while adding TGF-ß1 inhibitor SB525334 could rescue this impact, along with reduced TGF-ß1 and p-Smad2/3 level, enriched Smad4 level. KLF4 could also reverse the effect of miR-7 on TGF-ß1 signaling. Besides, it was confirmed that KLF4 could improve OA in rat OA models by HE and Safranin O-Fast green staining, and immunohistochemistry. Collectively, our findings will give more detailed evidence about miR-7 and KLF4 in OA diagnosis and treatment.