Inserm, UMR S-938, F-75012 Paris, France; UPMC Univ Paris 06, F-75005 Paris, France.
Int J Biochem Cell Biol. 2013 Nov;45(11):2568-73. doi: 10.1016/j.biocel.2013.08.009. Epub 2013 Aug 27.
The lung interfaces with the environment across a continuous epithelium composed of various cell types along the proximal and distal airways. At the alveolar structure level, the epithelium, which is composed of type I and type II alveolar epithelial cells, represents a critical component of lung homeostasis. Indeed, its fundamental role is to provide an extensive surface for gas exchange. Additional functions that act to preserve the capacity for such unique gas transfer have been progressively identified. The alveolar epithelium represents a physical barrier that protects from environmental insults by segregating inhaled foreign agents and regulating water and ions transport, thereby contributing to the maintenance of alveolar surface fluid balance. The homeostatic role of alveolar epithelium relies on the regulated/controlled production of the pulmonary surfactant, which is not only a key determinant of alveolar mechanical stability but also a complex structure that participates in the cross-talk between local cells and the lung immune and inflammatory response. In regard to these critical functions, a major point is the maintenance of alveolar surface integrity, which relies on the renewal capacity of type II alveolar epithelial cells, and the contribution of progenitor populations within the lung.
肺通过由近端和远端气道中各种细胞类型组成的连续上皮与环境相互作用。在肺泡结构水平，由 I 型和 II 型肺泡上皮细胞组成的上皮是肺稳态的关键组成部分。事实上，其基本功能是提供广泛的气体交换表面。此外，已经逐步确定了具有这种独特气体转移能力的保留的附加功能。肺泡上皮作为物理屏障，通过隔离吸入的外来物质并调节水和离子转运，从而有助于维持肺泡表面液体平衡，来保护身体免受环境侵害。肺泡上皮的稳态作用依赖于肺表面活性物质的调节/控制产生，肺表面活性物质不仅是肺泡机械稳定性的关键决定因素，而且是一种复杂的结构，参与局部细胞与肺免疫和炎症反应之间的串扰。关于这些关键功能，一个关键点是维持肺泡表面完整性，这依赖于 II 型肺泡上皮细胞的更新能力以及肺内祖细胞群体的贡献。
