Glycolytic disorder has been demonstrated to be a major cause of osteoarthritis (OA) and chondrocyte dysfunction. The present work aimed to investigate the expression and role of the glycolytic regulator 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) in OA cartilage. It was found that PFKFB3 expression was down-regulated in human OA cartilage tissues and in tumour necrosis factor (TNF)-α- or interleukin (IL)-1β-stimulated human chondrocytes. The glycolytic metabolism appeared as glucose utilization and adenosine triphosphate (ATP) generation, and lactate production was stunted in OA cartilage. However, the impaired glycolytic process in OA cartilage was improved by PFKFB3 overexpression, which was confirmed in TNF-α- or IL-1β-treated chondrocytes. Furthermore, the expressions of endoplasmic reticulum (ER) stress-associated genes including PERK, ATF3, IRE1, phosphorylated eIF2α (p-eIF2α) and MMP13 were enhanced in OA cartilage explants, while they were decreased by AdPFKFB3 transfection. PFKFB3 also modulated the expressions of PERK, ATF3, IRE1, p-eIF2α and MMP13 in tunicamycin-exposed chondrocytes. Additionally, PFKFB3 improved the cell viability of OA cartilage explants and chondrocytes through the PI3K/Akt/C/EBP homologous protein (CHOP) signalling pathway. The transfection of AdPFKFB3 also significantly reduced caspase 3 activation and promoted aggrecan and type II collagen expressions in OA cartilage explants and chondrocytes. In all, this study characterizes a novel role of PFKFB3 in glycolytic metabolism and ER stress of OA cartilage explants and chondrocytes. The study might provide a potential target for OA prevention or therapy.
MiR-9 has been found to be involved in the repair of spinal cord injury and regulates the proliferation and differentiation of mesenchymal stem cells. However, the role of miR-9 in repair of bone defects has not been well studied. The current study was designed to investigate its role and potential underlying mechanism in regulating osteoblast differentiation and angiogenesis. After treating the murine pre-osteoblast cell line MC3T3-E1 with BMP2, miR-9 expression was obviously down-regulated. Following transfection with miR-9 mimics, its overexpression enhanced the differentiation of MC3T3-E1 cells into osteoblasts as evidence that miR-9 up-regulated the mRNA levels of osteoblast differentiation-related protein, as well as increased differentiation and mineralization of osteoblasts. Further functional analysis has shown that miR-9 overexpression effectively increased human umbilical vein endothelial cell proliferation. Moreover, miR-9 up-regulation promoted cell migration, VEGF, and VE-cadherin concentrations, as well as tube formation in vitro. The mechanistic assay demonstrated that overexpression of miR-9-induced activation of the AMPK signaling pathway. Taken together, our findings suggested that miR-9 overexpression promoted osteoblast differentiation and angiogenesis via the AMPK signaling pathway, representing a novel and potential therapeutic target for the treatment of bone injury-related diseases.
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