Epithelial repair in asthma: Defect or exaggerated?

Early humoral defense under the radar: microvascular-epithelial cooperation at airways infection in asthma and health

“…Contrary to the firmly rooted research front idea of defect barrier ( 7 , 23 ), well-controlled in vivo studies in asthma and allergic rhinitis demonstrate that the human airway mucosal barrier against environmental challenges is maintained in these diseases, or even operationally tighter compared with healthy airways ( 5 , 7 ). Failed expectations may explain why some of the best-controlled studies, actually demonstrating reduced absorption permeability in asthma, are now available only as abstract ( 5 ).…”

“…Taken together, experimental in vivo data on pathogenic effects of epithelial regeneration alone and human bedside observations on maintained barrier despite occurrence of epithelial loss ( 5 ) suggest the possibility that exaggerated epithelial regeneration, rather than currently established notions of defect epithelial repair and defect epithelial barrier ( 7 , 23 ), is involved in pathogenesis of asthma. If increased epithelial regeneration associates with SARS-CoV-2 infection, this would be a factor that worsens asthma.…”

“…Epithelial shedding is a feature of asthma. Add to this the established notion of “defect epithelial repair” in this disease ( 5 , 7 , 23 ) and one would expect a dramatic loss of the mucosal barrier. However, this has not happened.…”

“…Acknowledged leaders in the fields of airway epithelial barrier and repair in asthma seem to either overlook and refuse to discuss the dichotomy between their bench data-based notions and physiological in vivo demonstrations in patients, or may not fully appreciate the scientific impact of well-controlled human in vivo data in the area of interest ( 7 , 23 ).…”

“…Perhaps this is, especially likely in asthmatic bronchi with an already fragile epithelium. Importantly, epithelial loss in asthma seems exceedingly patchy ( 5 , 6 , 23 ). This feature, together with plasma-derived both provisional barrier and milieu, the latter designed for optimal speed of epithelial regeneration as well as for biological defense capacity, may in part explain why asthmatic bronchi have exhibited neither increased absorption of inhaled molecules ( 5 , 7 ) nor a consistently increased risk for severe COVID-19 ( 1 ).…”