Lovering Richard M, Russ David W
Department of Physiology, University of Maryalnd School of Medicine, Baltimore, MD 21201, USA.
J Orthop Sports Phys Ther. 2008 Nov;38(11):674-80. doi: 10.2519/jospt.2008.2878.
Descriptive cadaveric laboratory study.
To identify the fiber type composition of the rotator cuff and teres major muscles in human subjects.
The rotator cuff is commonly injured in athletics and is a major focus of sports medicine. Although the anatomy and architecture of each muscle have been described in great detail, these muscles have never been fiber typed using immunohistochemistry or gel electrophoresis. Fiber typing is important in modeling function, exercise training, and rehabilitation.
We harvested tissue samples for all 4 rotator cuff muscles, as well as the teres major muscle from cadavers. Tissues were frozen in liquid nitrogen and sectioned. Cryosections were labeled with commercially available antibodies against fast and slow isoforms of myosin heavy chain (MHC). We also harvested fresh (unembalmed) tissue from deceased subjects and labeled tissue sections with antibodies against fast or slow MHC and wheat germ agglutinin. Gel electrophoresis followed by silver staining was also used to identify and quantify MHC isoforms in fresh tissue samples.
All of the muscles were of mixed fiber type composition. As a whole, 44% of rotator cuff fibers labeled positively for slow MHC, with slow MHC content of 54% in supraspinatus, 41% in infraspinatus, 49% in teres minor, 38% in subscapularis, and 40% in teres major. Mixed MHC isoform distribution was confirmed by SDS-PAGE, which also indicated that the IIa and IIx isoforms were roughly equally present across the muscles.
Human rotator cuff muscles, at least in older subjects, have a mixed fiber type. Because we only examined older subjects, we must limit our interpretation to this population.
描述性尸体实验室研究。
确定人体肩袖肌群和大圆肌的纤维类型组成。
肩袖肌群在体育运动中常受损伤，是运动医学的主要关注焦点。尽管对每块肌肉的解剖结构已进行了详细描述，但这些肌肉从未通过免疫组织化学或凝胶电泳进行纤维分型。纤维分型在功能建模、运动训练和康复中很重要。
我们从尸体上获取了所有四块肩袖肌群以及大圆肌的组织样本。将组织在液氮中冷冻并切片。冰冻切片用针对肌球蛋白重链（MHC）快、慢同工型的市售抗体进行标记。我们还从已故受试者身上获取了新鲜（未防腐）组织，并用针对快或慢MHC以及麦胚凝集素的抗体对组织切片进行标记。还使用凝胶电泳后银染法来鉴定和定量新鲜组织样本中的MHC同工型。
所有肌肉均为混合纤维类型组成。总体而言，44%的肩袖肌纤维慢MHC标记呈阳性，其中冈上肌慢MHC含量为54%，冈下肌为41%，小圆肌为49%，肩胛下肌为38%，大圆肌为40%。SDS-PAGE证实了混合MHC同工型分布，这也表明IIa和IIx同工型在各肌肉中大致等量存在。
人类肩袖肌群，至少在老年受试者中，具有混合纤维类型。由于我们仅检查了老年受试者，因此我们的解释必须局限于该人群。
