Expression analysis of α-smooth muscle actin and tenascin-C in the periodontal ligament under orthodontic loading or in vitro culture / 国际口腔科学杂志·英文版

α-smooth muscle actin (α-SMA) and tenascin-C are stress-induced phenotypic features of myofibroblasts. The expression levels of these two proteins closely correlate with the extracellular mechanical microenvironment. We investigated how the expression of α-SMA and tenascin-C was altered in the periodontal ligament (PDL) under orthodontic loading to indirectly reveal the intrinsic mechanical microenvironment in the PDL. In this study, we demonstrated the synergistic effects of transforming growth factor-β1 (TGF-β1) and mechanical tensile or compressive stress on myofibroblast differentiation from human periodontal ligament cells (hPDLCs). The hPDLCs under higher tensile or compressive stress significantly increased their levels of α-SMA and tenascin-C compared with those under lower tensile or compressive stress. A similar trend was observed in the tension and compression areas of the PDL under continuous light or heavy orthodontic load in rats. During the time-course analysis of expression, we observed that an increase in α-SMA levels was matched by an increase in tenascin-C levels in the PDL under orthodontic load in vivo. The time-dependent variation of α-SMA and tenascin-C expression in the PDL may indicate the time-dependent variation of intrinsic stress under constant extrinsic loading.

Expression of alkaline phosphatase in immortalized murine cementoblasts in response to compression-force

To determine the effect of compression-force on the expression of alkaline phosphatase [ALP], and ALP activity in cementoblasts. We performed this study in the State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu, Sichuan, China from October to December 2010. We exposed murine immortalized cementoblasts [OCCM-30] to 2000-microstrain compression-force at a frequency of 0.5 Hz for 1, 3, 6, 12, and 24 hours. We assayed the cellular ALP activity after the treatments. We used real-time polymerase chain reaction [RT-PCR] and western blot to examine the gene and protein expression of ALP in the OCCM-30 cells at each time point. Two-thousand micro strain compressive force significantly up-regulated the mRNA expression of ALP in OCCM-30 cells, which reached a peak at 12 hours loading, and the protein expression change of ALP in response to compression-force was consistent with the variation of gene level. We also noted marked enhancement of ALP activity in OCCM-30 cells during the application of mechanical stress. The compression-force increased the expression of ALP in OCCM-30 cells, suggesting that mechanical stimulation may affect the cellular function of cementoblasts by regulating ALP expression, which may participate in cementum metabolism during orthodontic tooth movement