Ong C T, Khoo Y T, Mukhopadhyay A, Do D V, Lim I J, Aalami O, Phan T T
Department of Surgery, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
Exp Dermatol. 2007 May;16(5):394-404. doi: 10.1111/j.1600-0625.2007.00550.x.
Keloid is a dermal fibroproliferative disorder characterized by excessive deposition of extracellular matrix (ECM) components such as collagen, glycoproteins and fibronectin. The mammalian target of rapamycin (mTOR) is a serine/theronine kinase which plays an important role in the regulation of metabolic processes and translation rates. Published reports have shown mTOR as regulator of collagen expression and its inhibition induces a decrease in ECM deposition. Our aim was to investigate the role of mTOR in keloid pathogenesis and investigate the effect of rapamycin on proliferating cell nuclear antigen (PCNA), cyclin D1, collagen, fibronectin and alpha-smooth muscle actin (alpha-SMA) expression in normal fibroblasts (NF) and keloid fibroblasts (KF). Tissue extracts obtained from keloid scar demonstrated elevated expression of mTOR, p70KDa S6 kinase (p70S6K) and their activated forms, suggesting an activated state in keloid scars. Serum stimulation highlighted the heightened responsiveness of KF to mitogens and the importance of mTOR and p70S6K during early phase of wound healing. Application of rapamycin to monoculture NF and KF, dose- and time-dependently downregulates the expression of cytoplasmic PCNA, cyclin D1, fibronectin, collagen and alpha-SMA, demonstrating the anti-proliferative effect and therapeutic potential of rapamycin in the treatment of keloid scars. The inhibitory effect of rapamycin was found to be reversible following recovery in the expression of proteins following the removal of rapamycin from the culture media. These results demonstrate the important role of mTOR in the regulation of cell cycle and the expression of ECM proteins: fibronectin, collagen and alpha-SMA.
瘢痕疙瘩是一种皮肤纤维增生性疾病，其特征在于细胞外基质（ECM）成分如胶原蛋白、糖蛋白和纤连蛋白过度沉积。雷帕霉素的哺乳动物靶点（mTOR）是一种丝氨酸/苏氨酸激酶，在代谢过程和翻译速率的调节中起重要作用。已发表的报告表明mTOR是胶原蛋白表达的调节因子，其抑制会导致ECM沉积减少。我们的目的是研究mTOR在瘢痕疙瘩发病机制中的作用，并研究雷帕霉素对正常成纤维细胞（NF）和瘢痕疙瘩成纤维细胞（KF）中增殖细胞核抗原（PCNA）、细胞周期蛋白D1、胶原蛋白、纤连蛋白和α-平滑肌肌动蛋白（α-SMA）表达的影响。从瘢痕疙瘩瘢痕中获得的组织提取物显示mTOR、p70KDa S6激酶（p70S6K）及其活化形式的表达升高，表明瘢痕疙瘩瘢痕处于活化状态。血清刺激突出了KF对有丝分裂原的更高反应性以及mTOR和p70S6K在伤口愈合早期的重要性。将雷帕霉素应用于单一培养的NF和KF，剂量和时间依赖性地下调细胞质PCNA、细胞周期蛋白D1、纤连蛋白、胶原蛋白和α-SMA的表达，证明了雷帕霉素在治疗瘢痕疙瘩瘢痕中的抗增殖作用和治疗潜力。在从培养基中去除雷帕霉素后，蛋白质表达恢复后，发现雷帕霉素的抑制作用是可逆的。这些结果证明了mTOR在细胞周期调节以及ECM蛋白：纤连蛋白、胶原蛋白和α-SMA表达中的重要作用。
