RT Journal Article SR Electronic T1 Characterization of Optimal Strain, Frequency and Duration of Mechanical Loading on Skeletal Myotubes' Biological Responses JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 1779 OP 1788 DO 10.21873/invivo.11972 VO 34 IS 4 A1 ATHANASIOS MOUSTOGIANNIS A1 ANASTASSIOS PHILIPPOU A1 EVANGELOS ZEVOLIS A1 ORJONA TASO A1 ANTONIOS CHATZIGEORGIOU A1 MICHAEL KOUTSILIERIS YR 2020 UL http://iv.iiarjournals.org/content/34/4/1779.abstract AB Background/Aim: Mechanical loading of differentiated myoblasts in vitro may mimic loading patterns of skeletal muscle in vivo. However, it is still uncharacterized the loading conditions that can produce the most effective muscle cells' biological responses, in vitro. This study investigated the effects of different loading protocols on the expression of myogenic regulatory factors, anabolic, atrophy and pro-apoptotic factors in skeletal myotubes. Materials and Methods: C2C12 myoblasts were differentiated and underwent various stretching protocols by altering their elongation, frequency and duration, utilizing an in vitro cell tension system. The loading-induced expression changes of MyoD, Myogenin, MRF4, IGF-1 isoforms, Murf1, Atrogin, Myostatin, Foxo and Fuca were measured by Real Time-PCR. Results: Stretching by 2% elongation at 0.25 Hz for 12 h was overall the most effective in inducing beneficial responses. Conclusion: A low strain, low frequency intermediate duration stretching can most effectively up-regulate myogenic/anabolic factors and down-regulate pro-apoptotic and atrophy genes in myotubes.