Abstract
The myotendinous junction (MTJ) is an interface that different stimuli alter their morphology. One of the main stimuli to promote alterations in the MTJ morphology is physical exercise. The present study aimed to investigate the morphology and molecular MTJ adaptations of biceps brachii muscle in adult Wistar rats submitted to different ladder-based protocols. Forty Wistar rats (90 days old) were divided into four groups: Sedentary (S), Climbing (C), Overload Climbing (OC), Climbing, and Overload Climbing (COC). The results of light microscopy demonstrated the cell and collagen tissue reorganization in the experimental groups. The sarcomeres lengths of different regions showed a particular development according to the specific protocols. The sarcoplasmic invaginations and evaginations demonstrated positive increases that promoted the myotendinous interface development. In the extracellular matrix, the structures presented an increase principally in the COC group. Finally, the immunofluorescence analysis showed the telocytes disposition adjacent to the MTJ region in all experimental groups, revealing their network organization. Thus, we concluded that the different protocols contributed to the morphological adaptations with beneficial effects in distinct ways of tissue and cellular development and can be used as a model for MTJ remodeling to future proteomic and genetic analysis.
Highlights
The C group had a higher FD value compared to the experimental groups, besides the Overload Climbing (OC) group was higher than the S and Climbing and Overload Climbing (COC) groups and lower than the C group
We concluded that the adaptations are wide in the face of different vertical-based protocols, the present results demonstrated the morphological benefits to muscle and tendon tissue in different aspects, at the myotendinous interface
The remodeling of myotendinous junction (MTJ) is presented by an increase in its ultrastructure that supports and stabilizes the transmission of force through the region necessary for the different exercises
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The myotendinous junction (MTJ) consists of a highly specialized interface where the connection between the sarcoplasmic membranes and the extracellular matrix collagen fibers occurs [1,2]. Its main function is the force transmission generated through the muscle intracellular contractile proteins to the connective tissue proteins, which results in the articular joint movement and determines the MTJ as a higher transmission force area of the locomotor apparatus [3,4]. The MTJ ultrastructure is characterized by long and thin projections, originating from the extracellular matrix, known as sarcoplasmic invaginations (finger-like processes) that penetrate and bind to the muscle belly, through the sarcoplasmic evaginations. The myofibrillar bundles at its distal end are involved by these “interdigitations” [1,5]
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