Bonilla K A, Pardes A M, Freedman B R, Soslowsky L J
McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, PA 19104.
John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138.
J Biomech Eng. 2019 Jan 1;141(1):0110021-8. doi: 10.1115/1.4041321.
Sex differences in the mechanical properties of different musculoskeletal tissues and their impact on tendon function and disease are becoming increasingly recognized. Tendon mechanical properties are influenced by the presence or absence of sex hormones and these effects appear to be tendon- or ligament-specific. The objective of this study was to determine how sex and hormone differences in rats affect supraspinatus tendon and muscle properties. We hypothesized that male supraspinatus tendons would have increased cross-sectional area but no differences in tendon material properties or muscle composition when compared to supraspinatus tendons from female or ovariectomized (OVX) female rats. Uninjured supraspinatus tendons and muscles from male, female, and OVX female rats were collected and mechanical and histological properties were determined. Our analysis demonstrated decreased dynamic modulus and increased hysteresis and cross-sectional area in male tendons. We found that male tendons exhibited decreased dynamic modulus (during low strain frequency sweep and high strain fatigue loading), increased hysteresis, and increased cross-sectional area compared to female and OVX female tendons. Despite robust mechanical differences, tendon cell density and shape, and muscle composition remained unchanged between groups. Interestingly, these differences were unique compared to previously reported sex differences in rat Achilles tendons, which further supports the concept that the effect of sex on tendon varies anatomically. These differences may partially provide a mechanistic explanation for the increased rate of acute supraspinatus tendon ruptures seen in young males.
不同肌肉骨骼组织力学特性的性别差异及其对肌腱功能和疾病的影响正日益受到认可。肌腱的力学特性受性激素存在与否的影响，且这些影响似乎具有肌腱或韧带特异性。本研究的目的是确定大鼠的性别和激素差异如何影响冈上肌腱和肌肉特性。我们假设，与雌性或去卵巢（OVX）雌性大鼠的冈上肌腱相比，雄性冈上肌腱的横截面积会增加，但肌腱材料特性或肌肉组成无差异。收集雄性、雌性和OVX雌性大鼠未受伤的冈上肌腱和肌肉，并测定其力学和组织学特性。我们的分析表明，雄性肌腱的动态模量降低，滞后现象增加，横截面积增大。我们发现，与雌性和OVX雌性肌腱相比，雄性肌腱在低应变频率扫描和高应变疲劳加载期间的动态模量降低，滞后现象增加，横截面积增大。尽管存在明显的力学差异，但各组之间的肌腱细胞密度和形状以及肌肉组成保持不变。有趣的是，与先前报道的大鼠跟腱性别差异相比，这些差异是独特的，这进一步支持了性别对肌腱的影响在解剖学上存在差异的概念。这些差异可能部分为年轻男性中急性冈上肌腱断裂发生率增加提供了一个机制性解释。
