Role of microRNA-19b-3p on osteoporosis after experimental spinal cord injury in rats.

Osteoporosis is a common complication accompanied by spinal cord injury (SCI) occurrence. MicroRNAs (miRNAs) have been proved to play a crucial role in the progression of osteoporosis, but their regulating mechanism is unclear. The present study investigated miRNA-19b-3p level in SCI rats induced by modified Allen method, as well as the role of miRNA-19b-3p in osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). MiRNA-19b-3p expression and bone mineral density (BMD) of femurs were measured at day 21 and day 60 after SCI in rats. Obvious miRNA-19b-3p up-regulation and aggravated bone loss were observed. MiRNA-19b-3p overexpression suppressed BMSC-derived osteoblast differentiation, which was confirmed by the decrease in alkaline phosphatase (ALP) activity, EBF2 expression, osteoprotegrin (OPG) to receptor activator of nuclear factor kappa-B ligand (RANKL) ratio and cell mineralization degree. Besides, MiRNA-19b-3p knockdown could reverse this phenomenon. Dual-luciferase reporter assays verified the targeting relationship between miRNA-19b-3p and EBF2. The in vivo experiments confirmed miRNA-19b-3p down-regulation could significantly attenuate osteoporosis after SCI, which was verified by increased BMD, collagen content, femur mineralization degree, EBF2 protein, and OPG-to-RANKL ratio. The results show that miRNA-19b-3p plays an important role in the osteoporosis process after SCI through regulating EBF2 expression.