Col6a1-/- Mouse Lung

Collagen 6 (COL6) is known for its role in a spectrum of congenital muscular dystrophies, which are often accompanied by respiratory dysfunction. However, little is known regarding the function of COL6 in the lung. We confirmed the presence of COL6 throughout the basement membrane region of mouse lung tissue. We studied lung structure and organization in a previously described Col6a1-/- mouse, which do not produce detectable COL6 in the lung. The Col6a1-/- mouse displayed multiple histopathological alveolar and airway abnormalities. The airspaces of Col6a1-/- lungs appeared simplified, with larger (29%, p<0.01) and fewer (31%, p<0.001) alveoli. These airspace abnormalities included a reduction in IsolectinB4+ alveolar capillaries and Sftpc+ ATII cells. Alterations in lung function consistent with these histopathological changes were evident. Col6a1-/- mice also displayed multiple airway changes including increased branching (59%, p<0.001), increased mucosal thickness (34%, p<0.001) and increased epithelial cell density (13%, p<0.001). Comprehensive transcriptome analysis revealed loss of COL6 is associated with reductions in integrin-paxillin-PI3K signaling in vivo. In vitro, COL6 promoted steady-state phospho-paxillin levels and reduced cell density (16-28%, p<0.05) at confluence. Inhibition of PI3K, or its downstream effectors, resulted in increased cell density to a level similar to that seen on matrices lacking COL6. Col6a1-/- and wildtype mouse lung第六型胶原蛋白（Collagen 6, COL6）因在一系列先天性肌营养不良症中发挥作用而为人所知，此类病症常伴随呼吸功能障碍。然而，目前对于COL6在肺部的功能尚不清楚。本研究证实了COL6广泛存在于小鼠肺组织的基底膜区域。我们对此前已报道的Col6a1基因敲除（Col6a1-/-）小鼠的肺部结构与组织形态进行了研究，该模型小鼠肺部无法产生可检测水平的COL6。Col6a1-/-小鼠表现出多处肺泡与气道的组织病理学异常。Col6a1-/-小鼠的肺气囊腔结构趋于简化，肺泡体积增大29%（p<0.01），数量减少31%（p<0.001）。此类气囊腔异常包括IsolectinB4阳性的肺泡毛细血管以及Sftpc阳性的II型肺泡上皮细胞（ATII cells）数量减少。与上述组织病理学变化相符的肺功能改变也十分显著。Col6a1-/-小鼠还出现多处气道改变：气道分支增加59%（p<0.001），黏膜厚度增加34%（p<0.001），上皮细胞密度升高13%（p<0.001）。全面的转录组分析显示，COL6缺失与体内整合素-桩蛋白-PI3K信号通路活性降低相关。体外实验中，COL6可提高稳态下磷酸化桩蛋白的表达水平，并使汇合状态下的细胞密度降低16%~28%（p<0.05）。抑制PI3K或其下游效应分子可使细胞密度升高至与在不含COL6的基质上培养时相近的水平。Col6a1-/-小鼠与野生型小鼠的肺组织