Differentiated and functional human airway epithelium regeneration in tracheal xenografts

Abstract

To investigate the regeneration process of a well-differentiated and functional human airway epithelium, we adapted an in vivo xenograft model in which adult human nasal epithelial cells adhere and progressively repopulate denuded rat tracheae grafted in nude mice. The proliferating activity, the degree of differentiation, and the barrier integrity of the repopulated epithelium were studied during the regeneration process at optical and ultrastructural levels with immunocytochemistry and a permeability tracer. Three days after implantation in nude mice, tracheal xenografts were partially repopulated with a flattened nonciliated and poorly differentiated leaky epithelium. By the end of the first week after the graft, cell proliferation produced on the entire surface of the rat trachea an epithelium that was stratified into multiple layers and tightly sealed. During successive weeks, cell proliferation dramatically decreased. Moreover, the epithelium became progressively columnar, secretory, ciliated, and transiently leaky. At 4-5 wk, a fully differentiated pseudostratified functional epithelial barrier impermeable to a low-molecular-weight tracer was reconstituted. The regeneration of a well-differentiated and functional human airway epithelium in rat tracheae grafted in nude mice includes several steps that mimic the regeneration dynamics of airway epithelium after injury.

Human Tracheobronchial Basal Cells. Normal versus Remodeling/Repairing PhenotypesIn VivoandIn Vitro

“…To overcome this issue, several groups identified cell-surface markers that can be used to separate BCs into subsets, using a fluorescence-activated cell sorter (FACS) (2,3,(8)(9)(10). One of these markers, tissue factor (TF), is a component of the extrinsic coagulation cascade (11), and was originally developed for the isolation of nasal polyp BCs (12). We showed that all Passage 1 TBE BCs that were cultured in bronchial epithelial cell growth medium (BEGM) were TF 1 , and that TF activity was necessary for BC survival in vitro (13).…”

“…We showed that all Passage 1 TBE BCs that were cultured in bronchial epithelial cell growth medium (BEGM) were TF 1 , and that TF activity was necessary for BC survival in vitro (13). Other TBE BC markers include nerve growth factor receptor (2), podoplanin (14), CD49f (a6 integrin) (8), the tetraspanin CD151 1 (12), and Trp63 (p63) (15). Our secondary aim involved determining whether TF and CD151 were (1) expressed by TBE BCs, and (2) could be used to identify TBE BC subsets.…”

Epithelial stem cells of the lung: privileged few or opportunities for many?

“…However, two ex vivo systems have been used to examine the regenerative potential of isolated lung epithelial cells: the rat tracheal xenograft model and cell culture. These systems are particularly useful because they can be applied to the study of human adult and fetal airway epithelial cells, including tracheal cells and nasal polyps, as discussed below (Dupuit et al, 2000).…”

A Single Cell Functions as a Tissue-Specific Stem Cell and theIn VitroNiche-Forming Cell

“…Analysis of human nasal polyp or bronchial cells (16)(17)(18), rat tracheal cells (19), and mouse tracheal cells (20) in air-liquid interface (ALI) cultures demonstrated that these cultures support basal cell self-renewal as well as ciliated and secretory differentiation. The ALI method was used to demonstrate that a population of basal cells defined by their cell surface phenotype generated a differentiated epithelium (18). Similar results were reported using tracheal xenografts, indicating equivalence of the in vitro and ex vivo methods.…”