Study Of Mechanics-mechanism On Morphocytological Changes Of Myoblast Induced By Cyclic Strain

Malocclusion is one kind of developmental diseases influencing on patient's externality and functions and the 3rd high-frequency stomatological disease steped with dental caries and periodontitis. Herein, functional malocclusion is common, and its treatment method is functional orthopedics,namely a complicated biological reaction of maxillomandible to the mechanical forces brought from masticatory muscles by the aid of functional appliances. The morphological and functional remodeling of masticatory muscles happens initially in a new mechanical environment, which is the key of functional orthopedics and plays an important role in acquiring good orthodontic treatment results and retention. So it is necessary to orthodontics to study the remodeling reaction of muscle in a variety of mechanical environments and this will provide theoretic guidance to the clinical treatment of functional malocclusion.Masticatory muscles belong to skeletal muscle, its basic component derived from myoblast. The shape and function of masticatory muscles are tied up with shape and function of myoblast. So we can reveal or understand the remodeling mechanism of masticatory muscles under stress environment by cell biomechanic methods in vivo. The morphological and functional changes of myoblast is decided by the remodeling of its cytoskeleton. Cytoskeleton includes three structural elements:microfilament, microtube and mediate- filament. But in myoblast, microfilament(F-actin) plays the most important role in the constructingand forming of its cytoskeleton. Actin.combined proteins, mainly including talin, vinculin and a-actin, are necessary to assemble and form F-actin,.To elucidate shape and function remodeling of masticatory muscles under different force environment, in first part of this study, myoblast from maxillofacial skeletal muscle of neonated male Sprague-Dawley rat were cultured, purified and identified, and then using four-point bend device cyclic strain with 2000ustrain and 0.5Hz were loaded to myoblast cultured at different time. The morphological changes of myoblast was observed under optical microscope and scanning electronic microscope, and morphological parameter of myoblast were measured with computer aided image recognizing and processing system.The morphological changes of myoblast is based on F-actin, in second part of this study, F-actin and actin combined protein (vinculin, talin and a-actinin) of myoblast in different force environment was stained with fluorescent antibody and detected under laser scanning confocal microscope.The results show as following:(1) With loading time prolonged, the shape of myoblast became long and large; At the same time, the arrangement of myoblast exhibited strong conformability to the direction of stress. When loading time was over 8 hours, this trendency can be found markedly(2) The measurement values of acreage, perimeter and length of myoblast increased with loading time prolonged, and that of shape index decreased. This changes became prominent when loading time was or over 8 hours.(3)In the beginning of load, Cytoskeletal microfilament(F-actin) fibres was dissolved , but with loading time prolonging F-actin became longer and wider; At the same time, the direction of F-actin fibres exhibitedconformability to the direction of stress.(4) fluorescence intensity of vinculin, paxillin , a-actin decreased in the beginning of Cyclic Strain , but it increased gradually with loading time prolonging.The results showed that the shape of myoblast became long and large and exhibited strong conformability to the direction of stress. This changes is based on remodeling of microfilament; actin combined protein (vinculin, paxillin and a-actin) is the base of the forming and assemblying of cytoskeleton. This result is helpful to understand the mechanism of muscle remodeling.