Meyer GA, Farris AL, Sato E, Gibbons M, Lane JG, Ward SR, Engler AJ.
Chronic rotator cuff (RC) tears affect a large portion of the population and
result in substantial upper extremity impairment, shoulder weakness, pain, and
limited range of motion. Regardless of surgical or conservative treatment,
persistent atrophic muscle changes limit functional restoration and may
contribute to surgical failure. We hypothesized that deficits in the skeletal
muscle progenitor (SMP) cell pool could contribute to poor muscle recovery
following tendon repair. Biopsies were obtained from patients undergoing
arthroscopic RC surgery. The SMP population was quantified, isolated, and assayed
in culture for its ability to proliferate and fuse in vitro and in vivo. The SMP
population was larger in muscles from cuffs with partial tears compared with no
tears or full thickness tears. However, SMPs from muscles in the partial tear
group also exhibited reduced proliferative ability. Cells from all cuff states
were able to fuse robustly in culture and engraft when injected into injured
mouse muscle, suggesting that when given the correct signals, SMPs are capable of
contributing to muscle hypertrophy and regeneration regardless of tear severity.
The fact that this does not appear to happen in vivo helps focus future
therapeutic targets for promoting muscle recovery following rotator cuff repairs
and may help improve clinical outcomes.
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