[Low-magnitude vibration promotes osteogenesis of osteoblasts in ovariectomized osteoporotic rats via the estrogen receptor α].

The purpose of this study was to investigate the effect of low-magnitude vibration on osteogenesis of osteoblasts in ovariectomized rats with osteoporosis via estrogen receptor α(ERα). The mRNA expression of osteogenic markers were examined with qRT-PCR, based on which the optimal vibration parameter for promoting osteogenesis was determined (45 Hz × 0.9 g, g = 9.8 m/s2). Then we loaded the optimal vibration parameter on the osteoblasts of ovariectomized rats with osteoporosis. The protein expression of osteogenic markers and ERα were detected with Western blot; the distribution of ERα was examined with immunofluorescence technique. Finally, through inhibiting the expression of ERα with estrogen receptor inhibitor ICI182780, the protein and mRNA expression of osteogenic markers were examined. First, the results showed that low-magnitude vibration could promote the expression of osteogenic markers and ERα in osteoblasts of ovariectomized rats with osteoporosis (P < 0.05), and make ERα transfer to the nucleus. On the other hand, the results also showed that after inhibiting the expression of ERα in osteoblasts of ovariectomized rats with osteoporosis, the protein and mRNA expression of osteogenic marker were decreased (P < 0.05). In our study, low-magnitude vibration played an important role in the osteogenesis of osteoblasts in ovariectomized rats with osteoporosis through increasing the expression and causing translocation of ERα. Furthermore, it provides a theoretical basis for the application of low-magnitude vibration in the prevention and treatment of postmenopausal osteoporosis.

Low-magnitude vibration induces osteogenic differentiation of bone marrow mesenchymal stem cells via miR-378a-3p/Grb2 pathway to promote bone formation in a rat model of age-related bone loss.

The dysfunction of bone marrow mesenchymal stem cells (BMSCs) in osteogenic differentiation is one of the main causes of age-related bone loss. Our previous studies have shown that low-magnitude vibration (LMV) induces the osteogenic differentiation of BMSCs derived from ovariectomized osteoporotic rats. To investigate whether LMV promotes osteogenic differentiation of BMSCs and its underlying mechanisms in aged rats, 20-month-old female Sprague-Dawley rats (n = 20) were randomly divided into LMV group (rats were vibrated at 0.3 g and 90 Hz for 30 minutes, once daily, 5 days a week until 12 weeks for subsequent analysis, n = 10), static group (rats were placed in the box on the vibration platform without vibration, n = 10); 6-month-old female Sprague-Dawley rats were used as control (young group, n = 10). The bone mineral density and bone strength of aged rats were significantly decreased compared with the young rats. Furthermore, the primary BMSCs isolated and cultured from the aged rats with the whole-bone marrow differential pasting method showed a decreased ability in osteogenic differentiation compared with that from the young rats. Then the differentially expressed miRNAs between the aged and young rat-derived BMSCs were screened by high-throughput sequencing and verified by qRT-PCR, and we found that miR-378a-3p was significantly downregulated in the aged rat-derived BMSCs compared with the young rat-derived BMSCs. By transfecting miRNA mimics and inhibitors, miR-378a-3p was confirmed to promote the expression levels of osteogenic genes (Runx2, ALP, Col I, and OCN) and ALP activity of the aged rat-derived BMSCs. Meanwhile, the expression levels of osteogenic genes and miR-378a-3p of aged rat-derived BMSCs were significantly upregulated by LMV (cells were vibrated at 0.3 g and 90 Hz for 30 minutes a day, until 5 days for subsequent analysis), while the LMV-induced osteogenic gene expression levels of aged rat-derived BMSCs were suppressed by miR-378a-3p inhibitors. Furthermore, the inhibition of growth factor receptor-bound protein 2 (Grb2) by miR-378a-3p and Grb2-siRNA promoted the LMV-induced osteogenic differentiation of aged rat-derived BMSCs. Additionally, LMV was found to promote bone mineral density and bone strength of aged rats in vivo, as well as upregulating the expression level of miR-378a-3p and downregulating the expression level of Grb2 of BMSCs from aged rats. These results suggest that LMV induces osteogenic differentiation of BMSCs through miR-378a-3p/Grb2 pathway to improve bone mineral density and mechanical properties in a rat model of age-related bone loss.

[Screening of the Optimum Medium for Rat Mesenchymal Stem Cells].

OBJECTIVE: To investigate the effect of three different cell culture mediums, DMEM-LG, α-MEM and DMEM/F12, on the growth of rat bone marrow mesenchymal stem cells (BMSCs) in vitro, and so that to screen out the most suitable medium for in vitro culturing the rat BMSCs. METHODS: BMSCS were isolated from the femur and tibia of SD rats by whole bone marrow differential adherence method. The isolated cells were then cultured with three culture mediums, DMEM-LG, α-MEM and DMEM/F12. The rat BMSCs morphology, adhesion, proliferation, the time of passage and the number the colony at day 14 in three mediums respectively were observed with inverted phase contrast microscopy and compared. Flow cytometry was used to identify and observe the effects of different mediums on the surface antigen expression of rats BMSCs. RESULTS: Compared with the other two groups of media, BMSCs cultured in DMEM-LG had shorter colony formation time, shorter first passage time, more clone formation (14±2) and showed uniform morphology and the highest attachment efficiency (47.0±2.8)%. Meanwhile, BMSCs cultured with DMEM-LG entered logarithmic growth phase after only 4 days of culturing and showed the highest average specific growth rate and the largest average number of propagations per unit time. The total number of cells reached about (2.2-2.7)×105 mL-1 within three days. The cells cultured with 3 mediums were all identified as rat BMSCs, and the expression of surface antigen in BMSCs was not significantly affected by different media. CONCLUSION: DMEM-LG is more suitable for proliferation of rat BMSCs in vitro.