Distinct Airway Epithelial Stem Cells Hide among Club Cells but Mobilize to Promote Alveolar Regeneration.
- 作者列表："Kathiriya JJ","Brumwell AN","Jackson JR","Tang X","Chapman HA
:Lung injury activates specialized adult epithelial progenitors to regenerate the epithelium. Depending on the extent of injury, both remaining alveolar type II cells (AEC2s) and distal airway stem/progenitors mobilize to cover denuded alveoli and restore normal barriers. The major source of airway stem/progenitors other than basal-like cells remains uncertain. Here, we define a distinct subpopulation (∼5%) of club-like lineage-negative epithelial progenitors (LNEPs) marked by high H2-K1 expression critical for alveolar repair. Quiescent H2-K1high cells account for virtually all in vitro regenerative activity of airway lineages. After bleomycin injury, H2-K1 cells expand and differentiate in vivo to alveolar lineages. However, injured H2-K1 cells eventually develop impaired self-renewal with features of senescence, limiting complete repair. Normal H2-K1high cells transplanted into injured lungs differentiate into alveolar cells and rescue lung function. These findings indicate that small subpopulations of specialized stem/progenitors are required for effective lung regeneration and are a potential therapeutic adjunct after major lung injury.
: 肺损伤激活专门的成人上皮祖细胞再生上皮。根据损伤程度，剩余的肺泡 ⅱ 型细胞 (AEC2s) 和远端气道干细胞/祖细胞均动员覆盖剥脱的肺泡并恢复正常屏障。除基底样细胞外，气道干细胞/祖细胞的主要来源仍不确定。在这里，我们定义了一个独特的棒状样谱系阴性上皮祖细胞 (LNEPs) 亚群 (∼ 5%)，其标志是肺泡修复关键的高 H2-K1 表达。静止的 H2-K1high 细胞几乎占了气道谱系的所有体外再生活性。博莱霉素损伤后，H2-K1 细胞在体内向肺泡谱系扩增分化。然而，受损的 H2-K1 细胞最终发展为衰老特征的自我更新受损，限制了完全修复。移植到损伤肺的正常 H2-K1high 细胞分化为肺泡细胞，挽救肺功能。这些发现表明，特殊的干细胞/祖细胞的小亚群是有效肺再生所必需的，并且是主要肺损伤后的潜在治疗辅助手段。
METHODS:BACKGROUND AND PURPOSE:A critical role for sphingosine kinase/sphingosine-1-phosphate (S1P) pathway in the control of airway function has been demonstrated in respiratory diseases. Here, we address S1P contribution in a mouse model of mild chronic obstructive pulmonary disease (COPD). EXPERIMENTAL APPROACH:C57BL/6J mice have been exposed to room air or cigarette smoke up to 11 months and killed at different time points. Functional and molecular studies have been performed. KEY RESULTS:Cigarette smoke caused emphysematous changes throughout the lung parenchyma coupled to a progressive collagen deposition in both peribronchiolar and peribronchial areas. The high and low airways showed an increased reactivity to cholinergic stimulation and α-smooth muscle actin overexpression. Similarly, an increase in airway reactivity and lung resistances following S1P challenge occurred in smoking mice. A high expression of S1P, Sph-K2 , and S1P receptors (S1P2 and S1P3 ) has been detected in the lung of smoking mice. Sphingosine kinases inhibition reversed the increased cholinergic response in airways of smoking mice. CONCLUSIONS AND IMPLICATIONS:S1P signalling up-regulation follows the disease progression in smoking mice and is involved in the development of airway hyperresponsiveness. Our study defines a therapeutic potential for S1P inhibitors in management of airways hyperresponsiveness associated to emphysema in smokers with both asthma and COPD.
METHODS::The interim results from this 90-day multi-dose, inhalation toxicology study with life-time post-exposure observation has shown an important fundamental difference in persistence and pathological response in the lung between brake dust derived from brake-pads manufactured with chrysotile, TiO2 or chrysotile alone in comparison to the amphiboles, crocidolite and amosite asbestos. In the brake dust exposure groups no significant pathological response was observed at any time. Slight macrophage accumulation of particles was noted. Wagner-scores, were from 1 to 2 (1 = air-control group) and were similar to the TiO2 group. Chrysotile being biodegradable, shows a weakening of its matrix and breaking into short fibers & particles that can be cleared by alveolar macrophages and continued dissolution. In the chrysotile exposure groups, particle laden macrophage accumulation was noted leading to a slight interstitial inflammatory response (Wagner-score 1-3). There was no peribronchiolar inflammation and occasional very slight interstitial fibrosis. The histopathology and the confocal analyses clearly differentiate the pathological response from amphibole asbestos, crocidolite and amosite, compared to that from the brake dust and chrysotile. Both crocidolite and amosite induced persistent inflammation, microgranulomas, and fibrosis (Wagner-scores 4), which persisted through the post exposure period. The confocal microscopy of the lung and snap-frozen chestwalls quantified the extensive inflammatory response and collagen development in the lung and on the visceral and parietal surfaces. The interim results reported here, provide a clear basis for differentiating the effects from brake dust exposure from those following amphibole asbestos exposure. The subsequent results through life-time post-exposure will follow.
METHODS::The respiratory tract is lined by a pseudo-stratified epithelium from the nose to terminal bronchioles. This first line of defense of the lung against external stress includes five main cell types: basal, suprabasal, club, goblet and multiciliated cells, as well as rare cells such as ionocytes, neuroendocrine and tuft/brush cells. At homeostasis, this epithelium self-renews at low rate but is able of fast regeneration upon damage. Airway epithelial cell lineages during regeneration have been investigated in the mouse by genetic labeling, mainly after injuring the epithelium with noxious agents. From these approaches, basal cells have been identified as progenitors of club, goblet and multiciliated cells, but also of ionocytes and neuroendocrine cells. Single-cell RNA sequencing, coupled to lineage inference algorithms, has independently allowed the establishment of comprehensive pictures of cell lineage relationships in both mouse and human. In line with genetic tracing experiments in mouse trachea, studies using single-cell RNA sequencing (RNAseq) have shown that basal cells first differentiate into club cells, which in turn mature into goblet cells or differentiate into multiciliated cells. In the human airway epithelium, single-cell RNAseq has identified novel intermediate populations such as deuterosomal cells, 'hybrid' mucous-multiciliated cells and progenitors of rare cells. Novel differentiation dynamics, such as a transition from goblet to multiciliated cells have also been discovered. The future of cell lineage relationships in the respiratory tract now resides in the combination of genetic labeling approaches with single-cell RNAseq to establish, in a definitive manner, the hallmarks of cellular lineages in normal and pathological situations.