Mechanical stretch promotes mesenchymal stem cell-osteoblast lineage migration through activation of mammalian target of rapamycin/matrix metalloproteinases signaling pathway / 中国组织工程研究

ABSTRACT

BACKGROUND:Distraction osteogenesis is one of the most important tissue engineering technologies. However, the exact signaling pathway controling mesenchymal stem cel-osteoblast lineage (MSC-OB) migration during distraction osteogenesis has not yet been elucidated. More efforts should be paid to make a ful understanding of the mechanism on MSC-OB lineage migration, which can improve the clinical efficacy of distraction osteogenesis. OBJECTIVE:To evaluate the effects of mechanical stretch on the ability of MSC-OB mobility and expression of mammalian target of rapamycin (mTOR) signaling pathway as wel as matrix metaloproteinases (MMPs) in MSC-OB, and to make clear the mechanism by which controls MSC-OB migration during distraction osteogenesis. METHODS:Twelve Sprague-Dawley rats were randomized into two groups experimental group (n=6), anin vivo rat mandibular distraction osteogenesis model was established on the right side of rats; non-stretch group (n=6), only the mandibular resection was done but with no distraction osteogenesis. Immunohistochemical staining was used to detect phosphorylated mTOR expression in new osteotylus at 15 days after operation. In addition, an in vitro cel stretch model was made in the mandibular mesenchymal stem cels from healthy Sprague-Dawley rats under resting tension force (6%, 4 hours); no distraction was done in control group. The ability of MSC-OB mobility, the expression of mTOR, Raptor, p70S6K and MMPs were evaluated using experiment methods including immunohistochemistry staining, real-time PCR and scratch assay. RESULTS AND CONCLUSION: The expression of phosphorylated mTOR in MSC-OB was upregulated in the mandibular bone calus of the stretch group than the non-stretch group (P < 0.05). In thein vitro experiments, MSC-OB applied with mechanical stretch (6%, 4 hours) showed elevated gene expression levels of mTOR, Raptor, p70S6K, MMP-2, MMP-9 and MMP-13 compared with the control group (0%, 4 hours). Meanwhile, MSC-OB in the experiment group (6%, 4 hours) showed a greater ability of mobility, as demonstrated by a farther distance after 48 hours of observation (P < 0.05). The present study suggests that the enhancement of MSC-OB mobility correlates with increase of the gene expression of MMPs and mTOR signaling pathway. Mechanical stretch may promote MSC-OB migration through activation of mTOR/MMPs signaling pathway.