Optimization of a pericyte therapy to improve muscle recovery after limb immobilization

Extended bed rest or limb immobilization can significantly reduce skeletal muscle mass and function. Recovery may be incomplete, particularly in older adults. Our laboratory recently reported that vascular mural cell (pericyte) quantity is compromised after immobilization and appropriate replacement immediately before remobilization can effectively recover myofiber size in mice. Identification of a single cell surface marker for isolation of the most therapeutic pericyte would streamline efforts to optimize muscle recovery. The purpose of this study was to compare the capacity for neural/glial antigen 2 (Cspg4/NG2⁺) and melanoma cell adhesion molecule (Mcam/CD146⁺) positive pericytes to uniquely recover skeletal muscle post-disuse. A single hindlimb from adult C57BL/6J mice was immobilized in full dorsiflexion via a surgical staple inserted through the center of the foot and body of the gastrocnemius. Fourteen days after immobilization, the staple was removed and pericytes, either NG2⁺CD45^-CD31^-[Lin^-], CD146⁺NG2^-Lin^-, or CD146⁺Lin^- pericytes, were injected into the atrophied tibialis anterior (TA) muscle. TA muscles were excised 14 days after transplantation and remobilization. Pericyte transplantation did not significantly improve muscle mass or myofiber cross-sectional area (CSA) after 14 days of remobilization. However, injection of CD146⁺ pericytes significantly increased Type IIa quantity, capillarization, and collagen remodeling compared with NG2⁺ pericytes (P < 0.05). Our results suggest that selection of pericytes based on CD146 rather than NG2 results in the isolation of therapeutic mural cells with high capacity to positively remodel skeletal muscle after a period of immobilization.NEW & NOTEWORTHY In this study, pericytes were isolated from mouse skeletal muscle based on cell surface marker expression of neural/glial antigen 2 (NG2) or melanoma cell adhesion molecule (Mcam/CD146) and then compared for the capacity to recover skeletal muscle after a period of immobilization in recipient mice. We report that CD146⁺Lin^- pericytes exhibit higher capacity than NG2⁺Lin^- pericytes to recover Type IIa fiber quantity, capillary content, and collagen turnover after disuse.