Hansen Mette, Kongsgaard Mads, Holm Lars, Skovgaard Dorthe, Magnusson S Peter, Qvortrup Klaus, Larsen Jytte O, Aagaard Per, Dahl Morten, Serup Annette, Frystyk Jan, Flyvbjerg Allan, Langberg Henning, Kjaer Michael
Institute of Sports Medicine, Bispebjerg Hospital, and Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
J Appl Physiol (1985). 2009 Apr;106(4):1385-93. doi: 10.1152/japplphysiol.90935.2008. Epub 2008 Oct 16.
The knowledge about the effect of estradiol on tendon connective tissue is limited. Therefore, we studied the influence of estradiol on tendon synthesis, structure, and biomechanical properties in postmenopausal women. Nonusers (control, n = 10) or habitual users of oral estradiol replacement therapy (ERT, n = 10) were studied at rest and in response to one-legged resistance exercise. Synthesis of tendon collagen was determined by stable isotope incorporation [fractional synthesis rate (FSR)] and microdialysis technique (NH(2)-terminal propeptide of type I collagen synthesis). Tendon area and fibril characteristics were determined by MRI and transmission electron microscopy, whereas tendon biomechanical properties were measured during isometric maximal voluntary contraction by ultrasound recording. Tendon FSR was markedly higher in ERT users (P < 0.001), whereas no group difference was seen in tendon NH(2)-terminal propeptide of type I collagen synthesis (P = 0.32). In ERT users, positive correlations between serum estradiol (s-estradiol) and tendon synthesis were observed, whereas change in tendon synthesis from rest to exercise was negatively correlated to s-estradiol. Tendon area, fibril density, fibril volume fraction, and fibril mean area did not differ between groups. However, the percentage of medium-sized fibrils was higher in ERT users (P < 0.05), whereas the percentage of large fibrils tended to be greater in control (P = 0.10). A lower Young's modulus (GPa/%) was found in ERT users (P < 0.05). In conclusion, estradiol administration was associated with higher tendon FSR and a higher relative number of smaller fibrils. Whereas this indicates stimulated collagen turnover in the resting state, collagen responses to exercise were negatively associated with s-estradiol. These results indicate a pivotal role for estradiol in maintaining homeostasis of female connective tissue.
关于雌二醇对肌腱结缔组织影响的知识有限。因此，我们研究了雌二醇对绝经后女性肌腱合成、结构和生物力学特性的影响。对非使用者（对照组，n = 10）或口服雌二醇替代疗法的习惯性使用者（ERT组，n = 10）在静息状态下以及对单腿阻力运动的反应进行了研究。通过稳定同位素掺入[分数合成率（FSR）]和微透析技术（I型胶原合成的NH(2)-末端前肽）测定肌腱胶原的合成。通过MRI和透射电子显微镜确定肌腱面积和纤维特征，而在等长最大自主收缩期间通过超声记录测量肌腱生物力学特性。ERT使用者的肌腱FSR明显更高（P < 0.001），而I型胶原合成的肌腱NH(2)-末端前肽在两组之间未观察到差异（P = 0.32）。在ERT使用者中，观察到血清雌二醇（s-雌二醇）与肌腱合成之间呈正相关，而从静息到运动时肌腱合成的变化与s-雌二醇呈负相关。两组之间的肌腱面积、纤维密度、纤维体积分数和纤维平均面积没有差异。然而，ERT使用者中中等大小纤维的百分比更高（P < 0.05），而对照组中较大纤维的百分比倾向于更高（P = 0.10）。ERT使用者的杨氏模量较低（GPa/%）（P < 0.05）。总之，给予雌二醇与较高的肌腱FSR和相对较多的较小纤维数量有关。虽然这表明在静息状态下胶原周转受到刺激，但胶原对运动的反应与s-雌二醇呈负相关。这些结果表明雌二醇在维持女性结缔组织稳态中起关键作用。
