Pierre Lesimple

Basal cells of the human adult airway surface epithelium retain transit-amplifying cell properties.

In numerous airway diseases, such as cystic fibrosis, the epithelium is severely damaged and must regenerate to restore its defense functions. Although the human airway epithelial stem cells have not been identified yet, we have suggested recently that epithelial stem/progenitor cells exist among both human fetal basal and suprabasal cell subsets in the tracheal epithelium. In this study, we analyzed the capacity of human adult basal cells isolated from human adult airway tissues to restore a well‐differentiated and functional airway epithelium. To this end, we used the human‐specific basal cell markers tetraspanin CD151 and tissue factor (TF) to separate positive basal cells from negative columnar cells with a FACSAria cell sorter. Sorted epithelial cells were seeded into epithelium‐denuded rat tracheae that were grafted subcutaneously in nude mice and on collagen‐coated porous membranes, where they were grown at the air‐liquid interface. Sorted basal and columnar populations were also analyzed for their telomerase activity, a specific transit‐amplifying cell marker, by the telomeric repeat amplification protocol assay. After cell sorting, the pure and viable CD151/TF‐positive basal cell population proliferated on plastic and adhered on epithelium‐denuded rat tracheae, as well as on collagen‐coated porous membranes, where it was able to restore a fully differentiated mucociliary and functional airway epithelium, whereas viable columnar negative cells did not. Telomerase activity was detected in the CD151/TF‐positive basal cell population, but not in CD151/TF‐negative columnar cells. These results demonstrate that human adult basal cells are at least airway surface transit‐amplifying epithelial cells.

Human airway surface epithelial regeneration is delayed and abnormal in cystic fibrosis.

Cystic fibrosis (CF) at an advanced stage of the disease is characterized by airway epithelial injury and remodelling. Whether CF remodelling is related to infection and inflammation or due to an abnormal regenerative process is still undecided. We have recently established the expression and secretion profiles of interleukin (IL)‐8, matrix metalloproteinase (MMP)‐7, MMP‐9, and tissue inhibitor of metalloproteinase (TIMP)‐1 during non‐CF airway epithelial regeneration in a humanized nude mouse xenograft model. To enhance our understanding of CF remodelling, we compared the regeneration process of non‐infected human CF and non‐CF nasal epithelia. In both CF and non‐CF situations, epithelial regeneration was characterized by successive steps of cell adhesion and migration, proliferation, pseudostratification, and terminal differentiation. However, histological examination of the grafts showed a delay in differentiation of the CF airway epithelium. Cell proliferation was higher in the regenerating CF epithelium, and the differentiated CF epithelium exhibited a pronounced height increase and basal cell hyperplasia in comparison with non‐CF epithelium. In addition, while the number of goblet cells expressing MUC5AC was similar in CF and non‐CF regenerated epithelia, the number of MUC5B‐immunopositive goblet cells was lower in CF grafts. The expression of human IL‐8, MMP‐7, MMP‐9, and TIMP‐1 was enhanced in CF epithelium, especially early in the regenerative process. Together, our data strongly suggest that the regeneration of human CF airway surface epithelium is characterized by remodelling, delayed differentiation, and altered pro‐inflammatory and MMP responses. Copyright

Human iPSC-Derived Neural Progenitors Are an Effective Drug Discovery Model for Neurological mtDNA Disorders

Mitochondrial DNA (mtDNA) mutations frequently cause neurological diseases. Modeling of these defects has been difficult because of the challenges associated with engineering mtDNA. We show here that neural progenitor cells (NPCs) derived from human induced pluripotent stem cells (iPSCs) retain the parental mtDNA profile and exhibit a metabolic switch toward oxidative phosphorylation. NPCs derived in this way from patients carrying a deleterious homoplasmic mutation in the mitochondrial gene MT-ATP6 (m.9185T>C) showed defective ATP production and abnormally high mitochondrial membrane potential (MMP), plus altered calcium homeostasis, which represents a potential cause of neural impairment. High-content screening of FDA-approved drugs using the MMP phenotype highlighted avanafil, which we found was able to partially rescue the calcium defect in patient NPCs and differentiated neurons. Overall, our results show that iPSC-derived NPCs provide an effective model for drug screening to target mtDNA disorders that affect the nervous system.

008 La régénération de l’épithélium de surface respiratoire est anormale dans la mucoviscidose☆

Introduction La mucoviscidose (CF) se traduit par des lesions et des remaniements de l’epithelium respiratoire : hyperplasie des cellules basales et secretoires, metaplasie malpighienne. Cependant, l’association de ces remaniements a l’infection et/ou a l’inflammation ou a un processus anormal de regeneration reste mal definie. Methodes Dans le but de mimer la dynamique de regeneration, les cellules epitheliales respiratoires non-infectees CF (ΔF508/ΔF508 n = 4; ΔF508/G542X n = 2; ΔF508/E92K n = 1; ΔF508/574delA n = 1) et non-CF (n = 7) ont ete ensemencees dans des trachees de rats denudees et greffees dans des souris nude. Resultats L’histologie des greffons montre que les cellules CF et non-CF adherent et migrent (stade I), proliferent (stade II), puis l’epithelium se pseudostratifie (stade III) et se differencie (stade IV). Cependant, apres 25 jours de greffe, l’epithelium CF est moins differencie (α La proliferation cellulaire analysee par immunohistochimie avec le Ki-67, ainsi que le nombre de cellules basales identifiees par la cyto-keratine 13, sont accrus dans les greffons differencies CF (p Le profil d’expression de l’IL-8, ainsi que celui des metalloproteina-ses (MMP) — 7 et — 9 et de leur inhibiteur tissulaire TIMP-1 a ete analyse. Nous avons recemment montre une expression et une secretion decroissantes de l’IL-8 au cours de la regeneration non-CF avec un niveau de TIMP-1 invariable, et une expression croissante de MMP — 7 et — 9 regulant la differenciation cellulaire (J Pathol 2005; 206: 160-9). Dans les greffons CF, l’expression et la secretion d’IL-8 decroissent avec un niveau d’ARNm et de proteines plus eleve (p Conclusions Nos resultats montrent que dans la mucoviscidose, la regeneration de l’epithelium respiratoire de surface est retardee et qu’elle est associee a une hyperplasie des cellules basales et a un desequilibre de l’expression des MMPs et de leur inhibiteur TIMP-1.