McNeilly C M, Banes A J, Benjamin M, Ralphs J R
Anatomy Unit, School of Molecular and Medical Biosciences, University of Wales College of Cardiff, UK.
J Anat. 1996 Dec;189 ( Pt 3)(Pt 3):593-600.
Tendons respond to mechanical load by modifying their extracellular matrix. The cells therefore sense mechanical load and coordinate an appropriate response to it. We show that tendon cells have the potential to communicate with one another via cell processes and gap junctions and thus could use direct cell/cell communication to detect and/or coordinate their load responses. Unfixed cryosections of adult rat digital flexor tendons were stained with the fluorescent membrane dye DiI to demonstrate cell shape. Similar sections were immunolabelled with monoclonal antibodies to rat connexin 32 or connexin 43 to demonstrate gap junctions and counterstained with propidium iodide to show nuclei, or the membrane stain DiOC7 to show cell membranes. Sections were examined with a laser scanning confocal microscope and 3-dimensional reconstructions were prepared from optical section series to demonstrate cell shape and the position of connexin immunolabel. Cells had a complex interconnected morphology with gap junctions at points of contact with other cells. Cell bodies contained the nucleus and extended broad flat lateral cell processes that enclosed collagen bundles and interacted with similar processes from adjacent cells. They also had long thin longitudinal processes interacting with the cell process network further along the tendon. Connexin 43 occurred where cell processes met and between cell bodies, whereas connexin 32 was only found between cell bodies. The results indicate the presence of a 3-dimensional communicating network of cell processes within tendons. The intimate relationship between cell processes and collagen fibril bundles suggests that the cell process network could be involved in load sensing and coordination of response to load. The presence of 2 different types of connexins suggests that there could be at least 2 distinct communicating networks.
肌腱通过改变其细胞外基质来响应机械负荷。因此，细胞能够感知机械负荷并协调相应的反应。我们发现，肌腱细胞有潜力通过细胞突起和缝隙连接相互通讯，从而可以利用直接的细胞间通讯来检测和/或协调它们对负荷的反应。用荧光膜染料DiI对成年大鼠指屈肌腱的未固定冰冻切片进行染色，以显示细胞形态。用抗大鼠连接蛋白32或连接蛋白43的单克隆抗体对类似切片进行免疫标记，以显示缝隙连接，并用碘化丙啶复染以显示细胞核，或用膜染料DiOC7显示细胞膜。用激光扫描共聚焦显微镜检查切片，并从光学切片系列制备三维重建图像，以显示细胞形态和连接蛋白免疫标记的位置。细胞具有复杂的相互连接的形态，在与其他细胞接触的部位有缝隙连接。细胞体包含细胞核，并伸出宽阔扁平的侧向细胞突起，这些突起包裹着胶原束，并与相邻细胞的类似突起相互作用。它们还有细长的纵向突起，与沿肌腱更远端的细胞突起网络相互作用。连接蛋白43出现在细胞突起相遇处和细胞体之间，而连接蛋白32仅在细胞体之间发现。结果表明肌腱内存在细胞突起的三维通讯网络。细胞突起与胶原纤维束之间的密切关系表明，细胞突起网络可能参与负荷感知和对负荷反应的协调。两种不同类型连接蛋白的存在表明可能至少有两个不同的通讯网络。
