Department of Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
Tissue Cell. 2010 Apr;42(2):116-20. doi: 10.1016/j.tice.2010.02.002. Epub 2010 Mar 23.
The insertion site of the tendon to the skeletal element is hypovascular and is one of the most common sites of dysfunction in the musculoskeletal system. However, the resident cells have been poorly defined due to a lack of a specific marker for tenocytes. We previously reported that Tenomodulin (Tnmd) and Chondromodulin-1 (Chm1) are homologous angiogenesis inhibitors and predominantly expressed in the avascular region of tendons and cartilage, respectively. In this study, we analyzed the expression of Tnmd, Chm1, alpha 1 chain of the type I collagen (Col1a1) and alpha 1 chain of the type II collagen (Col2a1) at the insertion site of the Achilles, patellar, or rotator cuff tendons of 1-week-old rabbits by in situ hybridization analysis. Tnmd was co-expressed with Col1a1 in tenocytes of these tendons, while Chm1 and Col2a1 were detected in chondrocytes of the hyaline cartilage. Interestingly, the cell population between Tnmd/Col1a1 positive tenocytes and Chm1/Col2a1 positive chondrocytes expressed Col1a1 but none of the other markers (Tnmd, Chm1, and Col2a1). Red blood cells were exclusively present at the interface between the tendon substance and cartilage in the insertion site of the Achilles tendon. Lack of Tnmd and Chm1 in this newly characterized cell population may allow the transitional zone between the poorly vascularized tendon and cartilage to establish the unique vascular pattern for blood supply.
肌腱在骨骼上的附着点是血供较少的部位，也是肌肉骨骼系统中功能障碍最常见的部位之一。然而，由于缺乏肌腱细胞的特异性标志物，其固有细胞一直未能得到很好的定义。我们之前的研究报告称，腱调蛋白（Tenomodulin，Tnmd）和软骨调节素 1（Chondromodulin-1，Chm1）是同源的血管生成抑制剂，分别在肌腱和软骨的无血管区中优先表达。在这项研究中，我们通过原位杂交分析，检测了 1 周龄兔子跟腱、髌腱或肩袖肌腱附着点处 Tnmd、Chm1、I 型胶原α1 链（Col1a1）和 II 型胶原α1 链（Col2a1）的表达。Tnmd 与这些肌腱中的肌腱细胞 Col1a1 共表达，而 Chm1 和 Col2a1 则在透明软骨的软骨细胞中检测到。有趣的是，在 Tnmd/Col1a1 阳性肌腱细胞和 Chm1/Col2a1 阳性软骨细胞之间的细胞群体表达 Col1a1，但不表达其他标志物（Tnmd、Chm1 和 Col2a1）。在跟腱附着点，红细胞仅存在于肌腱组织和软骨之间的界面处。这个新特征的细胞群体缺乏 Tnmd 和 Chm1，可能允许血供不良的肌腱和软骨之间的过渡区建立独特的血管模式。
