Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
PLoS One. 2011 Jan 26;6(1):e16337. doi: 10.1371/journal.pone.0016337.
The ability of tendons to glide smoothly during muscle contraction is impaired after injury by fibrous adhesions that form between the damaged tendon surface and surrounding tissues. To understand how adhesions form we incubated excised tendons in fibrin gels (to mimic the homeostatic environment at the injury site) and assessed cell migration. We noticed cells exiting the tendon from only the cut ends. Furthermore, treatment of the tendon with trypsin resulted in cell extravagation from the shaft of the tendons. Electron microscopy and immunolocalisation studies showed that the tendons are covered by a novel cell layer in which a collagen type IV/laminin basement membrane (BM) overlies a keratinised epithelium. PCR and western blot analyses confirmed the expression of laminin β1 in surface cells, only. To evaluate the cell retentive properties of the BM in vivo we examined the tendons of the Col4a1(+/Svc) mouse that is heterozygous for a G-to-A transition in the Col4a1 gene that produces a G1064D substitution in the α1(IV) chain of collagen IV. The flexor tendons had a discontinuous BM, developed fibrous adhesions with overlying tissues, and were acellular at sites of adhesion formation. In further experiments, tenotomy of wild-type mice resulted in expression of laminin throughout the adhesion. In conclusion, we show the existence of a novel tendon BM-epithelium that is required to prevent adhesion formation. The Col4a1(+/Svc) mouse is an effective animal model for studying adhesion formation because of the presence of a structurally-defective collagen type IV-containing BM.
在损伤后，肌腱在肌肉收缩时顺畅滑动的能力会受损，这是由于受损的肌腱表面和周围组织之间形成了纤维粘连。为了了解粘连是如何形成的，我们将切除的肌腱在纤维蛋白凝胶中孵育（模拟损伤部位的动态平衡环境），并评估细胞迁移。我们注意到细胞仅从切口端离开肌腱。此外，用胰蛋白酶处理肌腱会导致肌腱轴突细胞外溢。电子显微镜和免疫定位研究表明，肌腱表面覆盖着一层新型细胞层，其中Ⅳ型胶原/层粘连蛋白基膜（BM）覆盖在角化上皮上。PCR 和 Western blot 分析证实仅在表面细胞中表达层粘连蛋白β1。为了评估体内 BM 的细胞保留特性，我们检查了 Col4a1(+/Svc) 小鼠的肌腱，该小鼠在 Col4a1 基因中存在 G 到 A 的转换，导致 IV 型胶原α1 链中的 G1064D 取代。屈肌腱的 BM 不连续，与覆盖的组织形成纤维粘连，并且在粘连形成部位无细胞。在进一步的实验中，野生型小鼠的肌腱切开术导致整个粘连部位表达层粘连蛋白。总之，我们展示了一种新型的肌腱 BM-上皮的存在，它是防止粘连形成所必需的。由于存在结构缺陷的含有 IV 型胶原的 BM，Col4a1(+/Svc) 小鼠是研究粘连形成的有效动物模型。
