mTOR REGULATES THE PROLIFERATION AND DIFFERENTIATION OF TENDON STEM CELLS: AN IN VITRO STUDY

Abstract

Objectives: The mechanistic target of rapamycin (mTOR) controls cell growth and proliferation via translation regulation in eukaryotes. The present study investigated the effects of mTOR on the proliferation and differentiation of tendon stem cells (TSCs). Methods: The proliferation and differentiation ability of TSCs was tested in response to antagonist (MHY1485), and a depressor of mTOR (Rapamycin and KU0063794). CCK test was performed to test cell proliferation; quantitative real-time PCR (RT-PCR) and Western blot test were performed to evaluate the differentiation of TSCs. Results: Blocking of mTOR1 inhibited the proliferation of TSCs and blocking of mTOR2 enhanced the proliferation of TSCs; however, the effects of mTOR1 surpassed the effects of mTOR2. Blocking of mTOR1 or activation of mTOR2 induced the expression of TNC, and blocking of mTOR2 inhibited the expression of TNC. Blocking of mTOR1 by rapamycin decreased the expression of ap2. Both blocking of mTOR1 or mTOR2 had little effects on the expression of Runx2 and Sox9; however, activation of mTOR2 induced the expression of Runx2 and Sox9. Moreover, the Western blot test showed that blocking of mTOR1 by Rapamycin or the blocking of both mTOR1 and mTOR2 by KU-0062794 enhanced the expression of TNC; in addition, blocking of mTOR1 by Rapamycin enhanced the expression of c-EBPα and Sox9. However, activation of mTOR1 and mTOR2 by MHY1485 increased the expression of Runx2. Conclusions: mTOR played important roles in the proliferation and differentiation of TSCs. Furthermore, mTOR1 and mTOR2 played different roles on the proliferation and differentiation of TSCs. Blocking mTOR1 inhibited the proliferation of TSCs and played a dominant function.Blocking of mTOR1 enhanced the expression of tenocyte related genes; however, blocking of mTOR2 inhibited the expression of TNC. Blocking of mTOR1 by rapamycin decreased the expression of ap2 and activation of mTOR2 induced the expression of Runx2.