Hung Shih-Chieh, Kuo Pei-Yin, Chang Ching-Fang, Chen Tain-Hsiung, Ho Larry Low-Tone
Department of Orthopaedics and Traumatology, Veterans General Hospital-Taipei, 201 Sec. 2, Shih-Pai Road, 11217 Taipei, Taiwan, Republic of China.
Cell Tissue Res. 2006 Jun;324(3):457-66. doi: 10.1007/s00441-006-0156-x. Epub 2006 Feb 28.
The expression of alpha-smooth muscle actin (SMA) by human mesenchymal stem cells (hMSCs) during chondrogenesis was investigated by the use of pellet culture. Undifferentiated hMSCs expressed low but detectable amounts of SMA and the addition of transforming growth factor beta1 (TGF-beta1) to the culture medium increased SMA expression in a dose-dependent manner. Differentiation in pellet culture was rapidly induced in the presence of TGF-beta1 and was accompanied by the development of annular layers at the surface of the pellet. These peripheral layers lacked expression of glycosaminoglycan and type II collagen during early differentiation. Progress in differentiation increased the synthesis of glycosaminoglycan and type II collagen and the expression of SMA in these layers. Double-staining for type II collagen and SMA by immunofluorescence demonstrated the differentiation of hMSCs into cells positive for these two proteins. The addition of cytochalasin D, a potent inhibitor of the polymerization of actin microfilaments, caused damage to the structural integrity and surface smoothness of the chondrogenic pellets. The SMA-positive cells in the peripheral layers of the chondrogenic pellets mimic those within the superficial layer of articular cartilage and are speculated to play a major role in cartilage development and maintenance.
通过使用微团培养法研究了人间充质干细胞（hMSCs）在软骨形成过程中α-平滑肌肌动蛋白（SMA）的表达。未分化的hMSCs表达低水平但可检测到的SMA，向培养基中添加转化生长因子β1（TGF-β1）可使SMA表达呈剂量依赖性增加。在TGF-β1存在下，微团培养中的分化迅速诱导，并伴随着微团表面环形层的形成。在早期分化过程中，这些外周层缺乏糖胺聚糖和II型胶原的表达。分化进程增加了这些层中糖胺聚糖和II型胶原的合成以及SMA的表达。通过免疫荧光对II型胶原和SMA进行双重染色证明hMSCs分化为这两种蛋白阳性的细胞。添加细胞松弛素D（一种肌动蛋白微丝聚合的有效抑制剂）会损害软骨形成微团的结构完整性和表面光滑度。软骨形成微团外周层中的SMA阳性细胞类似于关节软骨表层内的细胞，推测其在软骨发育和维持中起主要作用。
