Phenylephrine effects on the morphology of osteoblasts and expression of nicotinamide phosphoribosyltransferase under oxidative stress / 中国组织工程研究

BACKGROUND: Phenylephrine has been proved to exert a protective effect on radiant-induced salivary gland and epithelial cell injuries, but its effect on hydrogen peroxide (H2O2)-induced oxidative stress in osteoblasts are not fully understood. OBJECTIVE: To explore the effect of phenylephrine on H2O2-induced oxidative stress in osteoblasts, and to explore the mechanism underlying the regulation by the expression level of nicotinamide phosphoribosyltransferase (Nampt). METHODS: Primary osteoblasts were cultured and randomly divided into four groups: blank control group, H2O2group, phenylephrine group, and combination group (0.5 hour pretreatment of 1×10-5mol/L phenylephrine, and then given 300 μmol/L H2O2). The morphology of osteoblasts was observed at different time points. Osteoblasts were collected after 24-hour culture, and total RNA and protein were then extracted to detect the mRNA and protein expression levels of Nampt by RT-PCR and western blot assay, respectively. RESULTS AND CONCLUSION: Compared with the blank control group, reduced osteoblasts and evident cell shrinks were observed in the H2O2group, while the number of osteoblasts significantly increased in the combined group compared with the H2O2group at 12, 24 and 48 hours of culture. RT-PCR results showed that the mRNA level of Nampt in the H2O2group was reduced by 31.23% of that in the blank control group, while the mRNA level of Nampt in the combination group was dramatically increased by 206.20% of that in the H2O2group at 24 hours of culture (both P < 0.05). Furthermore, western blot assay findings revealed that the protein level of Nampt in the H2O2group was reduced by 67.98% of that in the blank control group, while the protein level of Nampt in the combination group was increased by 152.25% of that in the H2O2group at 24 hours of culture (both P < 0.05). Our results indicate that phenylephrine can alleviate the shrink and atrophy of osteoblasts caused by H2O2, thereby exerting protective effect by up-regulating the mRNA and protein levels of Nampt that may be a regulatory gene.

Expression of bone-related genes in bone marrow MSCs after cyclic mechanical strain: implications for distraction osteogenesis / 国际口腔科学杂志·英文版

<p><b>AIM</b>Understanding the response of mesenchymal stem cells (MSCs) to mechanical strain and their consequent gene expression patterns will broaden our knowledge of the mechanobiology of distraction osteogenesis.</p><p><b>METHODOLOGY</b>In this study, a single period of cyclic mechanical stretch (0.5 Hz, 2,000 microepsilon) was performed on rat bone marrow MSCs. Cellular proliferation and alkaline phosphatase (ALP) activity was examined. The mRNA expression of six bone-related genes (Ets-1, bFGF, IGF-II, TGF-beta, Cbfa1 and ALP) was detected using real-time quantitative RT-PCR.</p><p><b>RESULTS</b>The results showed that mechanical strain can promote MSCs proliferation, increase ALP activity, and up-regulate the expression of these genes. A significant increase in Ets-1 expression was detected immediately after mechanical stimulation, but Cbfa1 expression became elevated later. The temporal expression pattern of ALP coincided perfectly with Cbfa1.</p><p><b>CONCLUSION</b>The results of this study suggest that mechanical strain may act as a stimulator to induce differentiation of MSCs into osteoblasts, and that these bone-related genes may play different roles in the response of MSCs to mechanical stimulation.</p>

Response of bone marrow mesenchymal stem cells to mechanical stretch and gene expression of transforming growth factor-beta and insulin-like growth factor-II under mechanical strain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the response of rat bone marrow mesenchymal stem cells (MSCs) to a single period of mechanical strain and expression patterns of transforming growth factor-beta (TGF-beta) and insulin-like growth factor-II (IGF-II) after mechanical stretch.</p><p><b>METHODS</b>Bone marrow MSCs were isolated from SD rats and cultured in vitro. A four-point bending apparatus were used to perform a single period of mechanical strain (2000 microepsilon, 40 min) on MSCs. Cellular proliferation and alkaline phosphatase (ALP) activity of MSCs were examined and gene expression patterns of TGF-beta and IGF-II were detected by SYBR green quantitative real-time RT-PCR.</p><p><b>RESULTS</b>Cell proliferation, ALP activity and expression of TGF-beta and IGF-II were all significantly up-regulated in stretched MSCs when compared with their controls. The mRNA levels of TGF-beta and IGF-II got top increase immediately after mechanical loading and increased about 51.44 and 8.92 folds, respectively, when compared with control cells. Expression of TGF-beta and IGF-II decreased with time and returned to control level at 12 h after mechanical stimulus, despite of a small increase at 6 h.</p><p><b>CONCLUSION</b>The mechanical stretch can promote MSCs proliferation, up-regulate its ALP activity and induce a time-dependent expression increase of TGF-beta and IGF-II which in turn result in osteogenic differentiation of MSCs. Mechanical stimulus is a key stimulator for osteogenic differentiation of MSCs and vital for bone formation in distraction osteogenesis.</p>

Osteoblastic differentiation and gene expression profile change in rat bone marrow mesenchymal stem cells after a single period of mechanical strain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the osteoblastic differentiation and compare the difference in the gene expression of rat bone marrow mesenchymal stem cells (MSCs) affected by a single period of mechanical strain.</p><p><b>METHODS</b>Bone marrow MSCs were harvested from the femurs and tibiae of SD rats and cultured in vitro. A four-point bending apparatus were used to perform a single 40-minute period of 2,000 microepsilon mechanical strain on these MSCs. The proliferation of the MSCs was tested by MTT on scheduled date, and the osteoblastic differentiation of the MSCs was measured by testing the expression of osteocalcin and alkaline phosphate (ALP) activity of these cells. In addition, we have investigated the possible mechanisms underlying the action of the single 40-minute period of 2,000 microepsilon mechanical strain on these MSCs, after profile blotted and handled by bioinformation, the gene expressions of these two periods of MSCs were examined.</p><p><b>RESULTS</b>The MSCs have grown well in vitro. Our experiment showed that mechanical environment did not weaken the proliferation of the MSCs. However, the ALP activity and the expression of osteocalcin were significantly up-regulated by the 2,000 microepsilon mechanical strain. Using the 27 K Rat Genome Array, 416 different expressions were found. The rate of different genes was 2.8%, of which the expressions of 247 genes increased (61 genes remarkably increased) and 169 genes decreased (74 genes remarkably decreased) in these two periods of MSCs.</p><p><b>CONCLUSION</b>Mechanical strain induced the osteoblastic differentiation of the MSCs, which may be attributed to the different gene levels.</p>

The changes of cytoskeleton F-actin in rat bone marrow mesenchymal stem cells and calvarial osteoblasts under mechanical strain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To explore the response of rat bone marrow mesenchymal stem cells (MSCs and calvarial osteoblasts to mechanical strain and the consequent changes of cytoskeleton F-actin.</p><p><b>METHODS</b>Bone marrow MSCs and calvarial osteoblasts were isolated from SD rats and cultured in vitro. Mechanical stretch was performed on passage 3 cells at 2 000 microepsilon for 0, 2, 6 and 12 hours using four-point bending system. The response of cells and the distribution of F-actin were observed using fluorescent staining under laser scanning confocal microscope and the morphological parameters were quantified using image analysis software Laserpix.</p><p><b>RESULTS</b>Under mechanical stretch, the fluorescent staining decreased obviously at both MSCs and osteoblasts, and F-actin filaments were rearranged and became tenuous, thinner, and abnormally distributed. The outline of nucleus became unclear and apoptotic changes were observed at some of both cells. Cellular size decreased more significantly in MSCs than in osteoblasts. Quantity analysis showed that total area of cells, total fluorescent density and green fluorescent density (F-actin) were all significantly decreased in MSCs (P < 0.05 or P < 0.01), and total fluorescent density, green fluorescent density and red fluorescent density (nuclei) did also in osteoblasts (P < 0.05 or P < 0.01).</p><p><b>CONCLUSION</b>Mechanical stretch caused extensive response on both MSCs and osteoblasts which led to the rearrangement of F-actin filament and apoptosis in some of these cells. MSCs were more sensitive to mechanical strain than osteoblasts.</p>