Mechanical load stimulates expression of novel genesin vivoandin vitroin avian flexor tendon cells

AbstractObjective: Our experiments were designed to test the hypothesis that tendon cells might respond differently to applied strainin vitrothanin vivo.Design: We tested cells in whole tendons from exercised chickens and from isolated surface (TSC) and internal tendon (TIF)in vitrothat were subjected to mechanical strain. We hypothesized that tendon cells differentially express genes in response to mechanical loadingin vivoandin vitro.Methods: We utilized an in-vivo exercise model in which chickens were run on a treadmill in an acute loading regime for 1h 45min with the balance of time at rest to 6h total time. Gene expression was analyzed by a differential display technique. In addition, isolated avian flexor digitorum profundus TSC and TIF cells were subjected to cyclic stretching at 1Hz, 5% average elongation for 6h, ±PDGF-BB, IGF-I, TGF-β1, PTH, estrogen, PGE2, or no drug and/or no load. mRNA was then collected and samples were subjected to differential display analysis.Conclusions: Load with or without growth factor and hormone treatments induced expression of novel genes as well as some known genes that were novel to tendon cells. We conclude that the study of gene expression in mechanically loaded cellsin vivoandin vitrowill lead to the discovery of novel and important marker proteins that may yield clues to positive and negative cell strain responses that are protective under one set of conditions and destructive under another