ABSTRACT
BACKGROUND:The adaptive reconstruction of maxil ofacial muscles would happen when functional orthopedic treatment is done to cure micromaxil ary deformity. The myoblast is the main responder in the process of adaptive reconstruction, and cyclic stretch can induce apoptosis of myoblasts. Caspase-9 is an important factor in the mitochondrial apoptosis pathway. OBJECTIVE:To investigate the expression of Caspase-9 in different cyclic stretch. METHODS:Based on myoblasts cultured in vitro-mechanical stimulation model, the rat L6 myoblasts were loaded stretch for 1, 6, 12 and 24 hours through multi-channel cellstress loading system, while the control group received no stretch. The morphological change and growth of myoblasts were observed under inverted phase contrast microscope;the expression of the mRNA and protein of Caspase-9 were detected by RT-PCR and western blot analysis, respectively. RESULTS AND CONCLUSION:Under inverted phase contrast microscope, the rat L6 myoblasts at cyclic stretch maintained a good growth state and biological characteristics;there was no celldegeneration;and the loss rate was extremely low, which could demonstrate that myoblast in vitro-mechanical stimulation model was established successful y. The results of RT-PCR and western blot analysis showed that, the expression of Caspase-9 mRNA and Cleaved Caspase-9 protein was significantly increased as the loading time prolonged, and the expression of Procaspase-9 protein was significantly decreased as the time. We can conclude that Caspase-9 is involved in the mechanical signal transduction of cyclic stretch.