The role of myosin II in tendon repair under glucose control

Tendon injury and disorders provide a severe negative impact on the economic cost and the ability to meet the patients' occupational, recreational, and health activities. Despite continuous efforts to improve the therapeutic modalities for tendon repair, truly effective and efficient therapies have not been established yet. Our long-term

goal is to understand the mechanisms underlying the limited regenerative potential of tendons and develop new methods for stimulating tendon repair. Unlike embryonic and neonatal tendons, neo-formed tendons after injury do not possess native tendon structure and mechanical properties. Healing tendons from scar with abnormal

mechanical properties. One of the key challenges for recovery of structure and function of injured tendons is how to potentiate the reparative capacity of the tendon progenitor cells involved in tendon healing, including how to stimulate their tenogenic differentiation and how to make them rebuild tendon matrix structure. The results from

clinical and translational studies indicate a close link between glucose metabolism and tendon healing capacity. We have found that 2-deoxy glucose (2DG), an inhibitor of glucose, stimulated recovery of collagen fiber alignment in injured tendons. Proteomics studies on the actions of 2DG on tendon healing demonstrated that

2DG stimulated the actin cytoskeletal signaling in injured tendons. Unexpectedly, we found that the mid- substance of tendons expressed muscle type myosin II components but a strongly down-regulated expression of these molecules when injured, whereas 2DG restored these changes. Furthermore, injured tendon-derived progenitor cells responded to 2DG, up-regulated expression of muscle type

myosin light chains, and rearranged actin cytoskeletons. Previous studies have demonstrated that actin cytoskeletal organization and myosin II activity are required for collagen fiber alignment. Taken together, we hypothesize that upregulation of muscle type myosin II molecules in injured tendons may stimulate collagen fiber

alignment. Furthermore, that glucose controls the expression of muscle type myosin II molecules and the actin cytoskeletal organization. To test these hypotheses, we propose two aims. In Aim 1, we will determine alterations of myosin II molecules in tendons during injury, healing, and regeneration. Spatiotemporal changes in the myosin

II components (myosin heavy and light chains) will be defined in injured tendons using four mouse Achilles tendon injury models. In Aim 2, we will determine the roles of muscle type of myosin II in injured tendon-derived cells (inTPCs). InTPCs will be treated with 2DG in mono- or 3D-culture, and changes in the expression of myosin

II molecules, RhoA/Rac activity, collagen fiber alignment, and mechanical properties will be examined. In addition, in the same model, the effects of gain- and loss-of-function of muscle myosin II molecules will be determined. Best of our knowledge, it has not been known whether muscle and non-muscle myosin II molecules have an

exclusive function in tendons. Thus, this project fits into the scope of R21, and the outcome provides the first clues to answer this question.