Department of Orthopaedic Surgery, Washington University, St. Louis, MO, USA.
J Shoulder Elbow Surg. 2012 Jul;21(7):847-58. doi: 10.1016/j.jse.2011.05.004. Epub 2011 Aug 10.
Irreversible muscle changes after rotator cuff tears is a well-known negative prognostic factor after shoulder surgery. Currently, little is known about the pathomechanism of fatty degeneration of the rotator cuff muscles after chronic cuff tears. The purposes of this study were to (1) develop a rodent animal model of chronic rotator cuff tears that can reproduce fatty degeneration of the cuff muscles seen clinically, (2) describe the effects of tear size and concomitant nerve injury on muscle degeneration, and (3) evaluate the changes in gene expression of relevant myogenic and adipogenic factors after rotator cuff tears using the animal model.
Rotator cuff tears were created in rodents with and without transection of the suprascapular nerve. The supraspinatus and infraspinatus muscles were examined at 2, 8, and 16 weeks after injury for histologic evidence of fatty degeneration and expression of myogenic and adipogenic genes.
Histologic analysis revealed adipocytes, intramuscular fat globules, and intramyocellular fat droplets in the tenotomized and neurotomized supraspinatus and infraspinatus muscles. Changes increased with time and were most severe in the muscles with combined tenotomy and neurotomy. Adipogenic and myogenic transcription factors and markers were upregulated in muscles treated with tenotomy or tenotomy combined with neurotomy compared with normal muscles.
The rodent animal model described in this study produces fatty degeneration of the rotator cuff muscles similar to human muscles after chronic cuff tears. The severity of changes was associated with tear size and concomitant nerve injury.
肩袖撕裂后肌肉不可逆转的变化是肩部手术后的一个已知的负面预后因素。目前，对于慢性肩袖撕裂后肩袖肌肉脂肪变性的病理机制知之甚少。本研究的目的是：(1)建立一种慢性肩袖撕裂的啮齿动物模型，该模型可复制临床上所见的肩袖肌肉脂肪变性；(2)描述撕裂大小和伴随的神经损伤对肌肉变性的影响；(3)使用该动物模型评估肩袖撕裂后相关成肌和成脂因子的基因表达变化。
通过切断肩胛上神经在啮齿动物中建立肩袖撕裂模型。在损伤后 2、8 和 16 周时，检查冈上肌和冈下肌，以观察组织学上的脂肪变性证据和成肌和成脂基因的表达。
组织学分析显示，在切断神经的冈上肌和冈下肌中存在脂肪细胞、肌内脂肪球和肌内脂肪滴。随着时间的推移，这些变化会增加，并且在同时进行切断术和神经切断术的肌肉中最为严重。与正常肌肉相比，切断术或切断术联合神经切断术处理的肌肉中，成脂和成肌转录因子和标志物上调。
本研究中描述的啮齿动物模型可产生类似于人类慢性肩袖撕裂后肩袖肌肉的脂肪变性。变化的严重程度与撕裂大小和伴随的神经损伤有关。
