Muscle-Derived Stem Cell-Enriched Scaffolds Are Capable of Enhanced Healing of a Murine Volumetric Muscle Loss Defect.

ABSTRACT

BACKGROUND: Volumetric muscle loss secondary to traumatic or surgical causes can lead to functional and aesthetic impairments. The authors hypothesize that an implantable muscle-derived stem cell-enriched collagen scaffold could significantly augment muscle regeneration in a murine model of volumetric muscle loss. METHODS: Murine muscle-derived stem cells were isolated using a modified preplating technique and seeded onto type 1 collagen scaffolds to create the muscle-derived stem cell-enriched collagen scaffolds. Murine rectus femoris defects of 5 mm were created and randomized to one of three conditions (n = 6 per group) untreated controls, collagen scaffold only, and muscle-derived stem cell-enriched collagen scaffolds. In vivo muscle healing was quantified using micro-computed tomography. Muscle explants were analyzed using standard histology and whole-mount immunofluorescence at 8 weeks. RESULTS: In vivo experiments demonstrated significantly greater quadriceps cross-sectional area in the muscle-derived stem cell-enriched collagen scaffold group compared with controls on micro-computed tomography (0.74 ± 0.21 versus 0.55 ± 0.06 versus 0.49 ± 0.04 ratio of experimental to naive quadriceps cross-sectional area; p < 0.05). Muscle explants of the muscle-derived stem cell-enriched collagen scaffold group demonstrated significantly higher cellular density compared with controls (1185 ± 360 versus 359 ± 62 versus 197 ± 68 nuclei/high-power field; p < 0.01). Immunofluorescence for laminin and myosin heavy chain confirmed formation of organized muscle fibers within the defect of the muscle-derived stem cell-enriched collagen scaffold group only. However, appreciable confocal colocalization of myosin heavy chain with green fluorescent protein expression was low. CONCLUSIONS: The results of this study indicate that muscle-derived stem cell-enriched scaffolds significantly improved skeletal muscle regeneration in a murine muscle defect model. Based on the low fluorescent colocalization, host progenitor cells appear to contribute significantly to intradefect myogenesis, suggesting that deployment of a viable muscle-derived stem cell-enriched scaffold stimulates a regenerative mitogen response in native tissues.