title: Rat rotator cuff muscle responds differently from hindlimb muscle to a combined tendon-nerve injury.
abstract: Rotator cuff tears (RCTs) are among the most common musculoskeletal injuries seen by orthopaedic surgeons. Clinically, massive cuff tears lead to unique pathophysiological changes in rotator cuff muscle, including atrophy, and massive fatty infiltration, which are rarely seen in other skeletal muscles. Studies in a rodent model for RCT have demonstrated that these histologic findings are accompanied by activation of the Akt/mammalian target of rapamycin (mTOR) and transforming growth factor-β (TGF-β) pathways following combined tendon-nerve injury. The purpose of this study was to compare the histologic and molecular features of rotator cuff muscle and gastrocnemius muscle--a major hindlimb muscle, following combined tendon-nerve injury. Six weeks after injury, the rat gastrocnemius did not exhibit notable fatty infiltration compared to the rotator cuff. Likewise, the adipogenic markers SREBP-1 and PPARγ as well as the TGF-β canonical pathway were upregulated in the rotator cuff, but not the gastrocnemius. Our study suggests that the rat rotator cuff and hindlimb muscles differ significantly in their response to a combined tendon-nerve injury. Clinically, these findings highlight the unique response of the rotator cuff to injury, and may begin to explain the poor outcomes of massive RCTs compared to other muscle-tendon injuries.
authors.affiliation: Department of Orthopaedic Surgery, University of California, 1500 Owens Street, 94158, San Francisco, California.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Davies
authors.affiliation: Department of Orthopaedic Surgery, University of California, 1500 Owens Street, 94158, San Francisco, California.|Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Bharat
authors.initials: B
authors.lastname: Ravishankar
authors.affiliation: Department of Orthopaedic Surgery, University of California, 1500 Owens Street, 94158, San Francisco, California.
authors.forename: Dominique
authors.initials: D
authors.lastname: Laron
authors.affiliation: Department of Orthopaedic Surgery, University of California, 1500 Owens Street, 94158, San Francisco, California.|Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Hubert T
authors.initials: HT
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, University of California, 1500 Owens Street, 94158, San Francisco, California.|Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, California.
authors.forename: Xuhui
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Orthopaedic Surgery, University of California, 1500 Owens Street, 94158, San Francisco, California.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Feeley
mesh_terms: D050156:Adipogenesis; D000818:Animals; D003714:Denervation; D005260:Female; D018482:Muscle, Skeletal / Q000293:injuries* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009133:Muscular Atrophy / Q000209:etiology; D017207:Rats, Sprague-Dawley; D017006:Rotator Cuff / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: C508962:Tgfb1 protein, rat; D053773:Transforming Growth Factor beta1
keywords: Akt/mTOR signaling; TGF-β signaling; fatty infiltration; rotator cuff tear; sciatic nerve denervation