α2 integrin expression in cyclosporin A-induced gingival overgrowth in rats

环孢素- a （CsA）被用作免疫抑制剂，其副作用是诱导纤维性牙龈过度生长。我们已经证明，大鼠实验性牙龈过度生长是由结缔组织中I型胶原降解减少引起的，主要是通过成纤维细胞对胶原的吞噬减少引起的。，第183卷，2000)。α2β1整合素被描述为成纤维细胞的I型胶原受体，α2亚基在胶原内化的吞噬调节中起关键作用。研究了csa诱导牙龈过度生长成纤维细胞中胶原吞噬活性与α2整合素表达的关系。分别饲喂含CsA或不含CsA的粉末状日粮8天和30天，从大鼠的下颌磨牙龈中分离出成纤维细胞。采用fitc标记的胶原包被乳胶珠，用流式细胞术检测培养成纤维细胞的吞噬能力。csa处理第8天和第30天分离的成纤维细胞的吞噬率分别为2.1±1.0%和13.0±3.5%，而对照成纤维细胞的吞噬率分别为13.7±2.7%和33.3±4.9%。fitc标记的抗大鼠α2整合素抗体免疫染色显示，csa处理大鼠分离的成纤维细胞染色弱于各对照组。流式细胞术定量分析α2整合素表达结果显示，csa处理大鼠成纤维细胞在第8天和第30天的荧光强度分别为25.1±6.1和51.1±2.5，而对照组为50.7±6.3和67.0±5.5。RT-PCR分析结果显示，CsA抑制α2整合素mRNA的表达。上述结果提示，csa处理大鼠牙龈中α2整合素表达降低导致的胶原吞噬减少与I型胶原的增加密切相关。

Cyclosporin-A (CsA) is used as an immunosuppressive agent and its side effect is the induction of fibrous gingival overgrowth. We have shown that experimental gingival overgrowth in rat is induced by a decrease of type I collagen degradation in the connective tissue, predominantly through a reduced collagen phagocytosis by fibroblasts (J.Cell.Physiol., vol.183, 2000). The α2β1 integrin have been described as type I collagen receptor on fibroblasts and the α2 subunit plays a critical role in the phagocytic regulation of collagen internalization. The relationship between collagen phagocytic activity and expression of α2 integrin on fibroblasts in CsA-induced gingival overgrowth was investigated. Fibroblasts were isolated from mandibular molar gingiva of rats fed with a powdered diet containing or lacking CsA for 8 or 30 days. In vitro analysis was performed to measure the phagocytosis of cultured fibroblasts with flow cytometry using FITC-labeled collagen coated latex beads. Fibroblasts isolated from CsA-treated rat on days 8 and 30 contained 2.1±1.0% and 13.0±3.5% phagocytic cells, whereas control fibroblasts contained 13.7±2.7% and 33.3±4.9% phagocytic cells, respectively. Immunostaining with FITC-labeled anti-rat α2 integrin antibody revealed that fibroblasts isolated from CsA-treated rat were weakly stained than those of each control. The quantitative analysis of α2 integrin expression using flow cytometry revealed that fluorescence intensity of fibroblasts isolated from CsA-treated rat on days 8 and 30 were 25.1±6.1 and 51.1±2.5, whereas 50.7±6.3 and 67.0±5.5 in the controls, respectively. RT-PCR analysis revealed that α2 integrin mRNA expressions were suppressed by CsA than those of each control. These findings suggest that the decrease of collagen phagocytosis due to the lower expression of α2 integrin on fibroblasts are closely associated with the increase of type I collagen in CsA-treated rat gingiva.