Division of Medical Biochemistry, Department of Biomolecular Sciences, Saga Medical School, 5-1-1 Nabeshima, Saga, 849-8501, Japan.
Department of Environmental Immuno-Dermatology, Yokohama City University Graduate School of Medicine, Yokohama, 236-0004, Japan.
Respir Res. 2020 Jan 30;21(1):38. doi: 10.1186/s12931-020-1299-0.
Idiopathic pulmonary fibrosis (IPF) is a devastating disease with a median survival of only three to 5 years. Fibroblast proliferation is a hallmark of IPF as is secretion of extracellular matrix proteins from fibroblasts. However, it is still uncertain how IPF fibroblasts acquire the ability to progressively proliferate. Periostin is a matricellular protein highly expressed in the lung tissues of IPF patients, playing a critical role in the pathogenesis of pulmonary fibrosis. However, it remains undetermined whether periostin affects lung fibroblast proliferation.
In this study, we first aimed at identifying periostin-dependently expressed genes in lung fibroblasts using DNA microarrays. We then examined whether expression of cyclins and CDKs controlling cell cycle progression occur in a periostin-dependent manner. We next examined whether downregulation of cell proliferation-promoting genes by knockdown of periostin or integrin, a periostin receptor, using siRNA, is reflected in the cell proliferation of lung fibroblasts. We then looked at whether lung fibroblasts derived from IPF patients also require periostin for maximum proliferation. We finally investigated whether CP4715, a potent inhibitor against integrin αβ (a periostin receptor), which we have recently found blocks TGF-β signaling, followed by reduced BLM-induced pulmonary fibrosis in mice, can block proliferation of lung fibroblasts derived from IPF patients.
Many cell-cycle-related genes are involved in the upregulated or downregulated genes by periostin knockdown. We confirmed that in lung fibroblasts, periostin silencing downregulates expression of several cell-cycle-related molecules, including the cyclin, CDK, and, E2F families, as well as transcription factors such as B-MYB and FOXM1. Periostin or integrin silencing slowed proliferation of lung fibroblasts and periostin silencing increased the distribution of the G0/G1 phase, whereas the distribution of the G2/M phase was decreased. Lung fibroblasts derived from IPF patients also required periostin for maximum proliferation. Moreover, CP4715 downregulated proliferation along with expression of cell-cycle-related genes in IPF lung fibroblasts as well as in normal lung fibroblasts.
Periostin plays a critical role in the proliferation of lung fibroblasts and the present results provide us a solid basis for considering inhibitors of the periostin/integrin αβ interaction for the treatment of IPF patients.
特发性肺纤维化（IPF）是一种毁灭性疾病，中位生存期仅为 3 至 5 年。成纤维细胞增殖是 IPF 的标志，成纤维细胞分泌细胞外基质蛋白也是如此。然而，IPF 成纤维细胞如何获得逐渐增殖的能力仍不确定。骨粘连蛋白是一种细胞外基质蛋白，在 IPF 患者的肺组织中高度表达，在肺纤维化的发病机制中起关键作用。然而，骨粘连蛋白是否影响肺成纤维细胞增殖仍不确定。
在这项研究中，我们首先使用 DNA 微阵列旨在鉴定成纤维细胞中依赖骨粘连蛋白表达的基因。然后，我们检查了细胞周期进展中控制细胞周期的细胞周期蛋白和细胞周期蛋白依赖性激酶的表达是否依赖于骨粘连蛋白。接下来，我们使用 siRNA 检查了骨粘连蛋白或整合素（骨粘连蛋白受体）下调对促进细胞增殖基因的表达是否反映在肺成纤维细胞的细胞增殖中。然后，我们观察了来自 IPF 患者的肺成纤维细胞是否也需要骨粘连蛋白以达到最大增殖。最后，我们研究了我们最近发现的一种针对整合素 αβ（骨粘连蛋白受体）的有效抑制剂 CP4715 是否可以阻断来自 IPF 患者的肺成纤维细胞的增殖，CP4715 阻断 TGF-β 信号传导，随后减少 BLM 诱导的小鼠肺纤维化。
许多细胞周期相关基因参与了骨粘连蛋白敲低引起的上调或下调基因。我们证实，在肺成纤维细胞中，骨粘连蛋白沉默下调了几种细胞周期相关分子的表达，包括细胞周期蛋白、细胞周期蛋白依赖性激酶和 E2F 家族，以及转录因子如 B-MYB 和 FOXM1。骨粘连蛋白或整合素沉默会减缓肺成纤维细胞的增殖，骨粘连蛋白沉默会增加 G0/G1 期的分布，而 G2/M 期的分布则减少。来自 IPF 患者的肺成纤维细胞也需要骨粘连蛋白才能达到最大增殖。此外，CP4715 下调了 IPF 肺成纤维细胞和正常肺成纤维细胞的增殖以及细胞周期相关基因的表达。
骨粘连蛋白在肺成纤维细胞的增殖中起关键作用，本研究结果为我们考虑骨粘连蛋白/整合素 αβ 相互作用抑制剂治疗 IPF 患者提供了坚实的基础。
