ABSTRACT
Objective To investigate whether the low-frequency pulsed electromagnetic fields (LF-PEMFs) can enhance the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) induced by bone morphogenetic protein 9 (BMP9). Methods We isolated CD146＋/STRO-1＋ cells (namely PDLSC) from periodontal ligament cells of healthy human premolars, transfected the PDLSC with BMP9-overexpressing recombinant adenoviruses (Ad-GFP-BMP9), exposed the cells to the different intensities of PEMF stimulation (15 Hz, 0.6，1.2，1.8，2.4，3.0 mT, 1 h/12 h), and then detected the expression of runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), osteopontin (OPN) and osteocalcin (OCN) by qRT-PCR and Western blotting. Results Overexpression of BMP9 significantly promoted the expression of osteogenic markers (Runx2, ALP, OCN and OPN) in PDLSC (P0.05). After the intervention with 1.2, 1.8, 2.4 and 3.0 mT PEMF, the expression levels of osteogenic markers in PDLSC were significantly higher than those exposed to BMP9 alone (P0.05), and reached the peak at 2.4 mT (P0.05), indicating that LF-PEMFs enhanced BMP9-induced osteogenic differentiation of PDLSC, and there was a “window effect”. Conclusion LF-PEMFs stimulation (15 Hz, 1.8 to 3.0 mT) can enhance BMP9-induced osteogenesis of hPDLSCs in vitro.
ABSTRACT
Objective To study the mechanical properties of PVP/PVA composite hydrogel and its interaction principle based on the molecular dynamics (MD) theory. Methods MD simulation was applied to investigate mechanical properties and radial distribution functions of PVP, PVA and their mixed system PVP/PVA. Results Compared with the pure PVP, mechanical properties of PVP/PVA were significantly improved, and not affected by temperature. The interaction between PVA and PVP was expected to occur through the interchain hydrogen bonding between the oxygen atom of PVP and the hydroxyl group of PVA. Conclusions MD method revealed the interaction mechanism of PVP/PVA hydrogel at molecular microscopic level and proved it better than pure PVP. Meanwhile, its mechanical properties were stable at different environment temperatures. These results provide a reliable theoretical research method for studying the fabrication process of hydrogel prosthesis in clinic and its mechanical properties.