Pericytes express markers of cellular proliferation without expansion of the pool in response to exercise-induced skeletal muscle damage

Muscle-resident stromal cells, known as pericytes, have been shown to support muscle repair and/or regeneration. However, the extent to which pericytes respond during skeletal muscle repair in humans remains relatively unknown. The purpose of this study was to evaluate the pericyte response following damage-inducing eccentric muscle contractions. Healthy, young men (21.5 ± 0.5 years, n = 22), performed maximal muscle lengthening contractions via an isokinetic dynamometer. Muscle biopsies from the vastus lateralis were taken at baseline (Pre) and, 6 h-, 24 h-, 72 h-, 96 h following exercise-induced damage. Muscle-resident NG2+ pericyte content remained unchanged over time (p > 0.05), but the number of pericytes actively proliferating (Ki67+/NG2+) was significantly (p < 0.05) elevated 24 h following damage. NG2 protein and associated mRNA expression of CSPG4 were significantly (p < 0.05) increased 24 h post-exercise. mRNA expression of signaling factors, related to pericyte mobility and activation including TNFa, CD248 and CXCR4 were significantly upregulated at 24 h post-exercise (p < 0.05). Taken together, muscle injury promotes the upregulation of nuclear proteins associated with proliferation of NG2+ pericytes and increases pericyte associated mRNA expression.