Lehner C, Gehwolf R, Ek J C, Korntner S, Bauer H, Bauer H C, Traweger A, Tempfer H
Institute of Tendon and Bone Regeneration, Paracelsus Medical University - Spinal Cord Injury & Tissue Regeneration Center Salzburg, A-5020 Salzburg,
Eur Cell Mater. 2016 May 26;31:296-311. doi: 10.22203/ecm.v031a19.
Tissue barriers function as "gate keepers" between different compartments (usually blood and tissue) and are formed by specialised membrane-associated proteins, localising to the apicolateral plasma membrane domain of epithelial and endothelial cells. By sealing the paracellular space, the free diffusion of solutes and molecules across epithelia and endothelia is impeded. Thereby, tissue barriers contribute to the establishment and maintenance of a distinct internal and external environment, which is crucial during organ development and allows maintenance of an organ-specific homeostatic milieu. So far, various epithelial and endothelial tissue barriers have been described, including the blood-brain barrier, the blood-retina barrier, the blood-testis barrier, the blood-placenta barrier, and the cerebrospinal fluid (CSF)-brain barrier, which are vital for physiological function and any disturbance of these barriers can result in severe organ damage or even death. Here, we describe the identification of a novel barrier, located in the vascular bed of tendons, which we term the blood-tendon barrier (BTB). By using immunohistochemistry, transmission electron microscopy, and tracer studies we demonstrate the presence of a functional endothelial barrier within tendons restricting the passage of large blood-borne molecules into the surrounding tendon tissue. We further provide in vitro evidence that the BTB potentially contributes to the creation of a distinct internal tissue environment impacting upon the proliferation and differentiation of tendon-resident cells, effects which might be fundamental for the onset of tendon pathologies.
组织屏障在不同腔室（通常是血液和组织）之间起到“守门人”的作用，由特殊的膜相关蛋白形成，定位于上皮细胞和内皮细胞的顶端外侧质膜结构域。通过封闭细胞旁间隙，溶质和分子跨上皮和内皮的自由扩散受到阻碍。因此，组织屏障有助于建立和维持独特的内部和外部环境，这在器官发育过程中至关重要，并有助于维持器官特异性的稳态环境。到目前为止，已经描述了各种上皮和内皮组织屏障，包括血脑屏障、血视网膜屏障、血睾屏障、血胎盘屏障和脑脊液-脑屏障，这些屏障对生理功能至关重要，这些屏障的任何干扰都可能导致严重的器官损伤甚至死亡。在这里，我们描述了一种位于肌腱血管床中的新型屏障的鉴定，我们将其称为血腱屏障（BTB）。通过使用免疫组织化学、透射电子显微镜和示踪研究，我们证明了肌腱内存在功能性内皮屏障，限制了血液中大分子进入周围肌腱组织。我们进一步提供了体外证据，表明BTB可能有助于创造一个独特的内部组织环境，影响肌腱驻留细胞的增殖和分化，这些作用可能是肌腱病理发生的基础。
