Following injury stem cells restore normal tissue architecture by producing the proper number and proportions of differentiated cells. with either secretory or ciliated cell fate commitment. One basal cell population displays intracellular Notch2 activation and directly generates secretory cells; the other expresses c-myb and directly yields ciliated cells. Furthermore disrupting Notch ligand activity within the Calcifediol basal cell population at large disrupts the normal pattern of lineage segregation. These non-cell autonomous effects demonstrate that effective airway epithelial regeneration requires intercellular communication within the broader basal stem/progenitor cell population. These findings have broad implications for understanding epithelial regeneration and stem cell heterogeneity. Introduction The murine tracheal epithelium and much of the human airway epithelium is composed of two cellular compartments: the basal cell compartment where basal stem/progenitor cells reside and the luminal cell compartment which contains mature secretory cells and ciliated cells (Rock and Hogan 2011 Rock et al. 2010 Murine lineage tracing experiments have exhibited that basal cells as a population are stem cells since they self-renew and differentiate into ciliated Rabbit Polyclonal to SFRS7. and secretory luminal cells over an extended period of time (Rock et al. 2009 Hogan et al. 2014 However prior reports also present evidence for heterogeneity within the airway basal cell compartment with regard to both basal cell proliferative and differentiation capacity (Ghosh et al. 2011 2011 2013 2013 Hong et al. 2004 In order to further investigate the heterogeneity of basal stem/progenitor cells we sought to define the expression patterns of early markers of differentiation in the airway epithelium. Current models of the airway epithelial cell lineage hierarchy suggest that basal stem cells characterized by p63 NGFR and Podoplanin (Pdpn) expression give rise to uncommitted suprabasal CK8+ p63? progenitor cells that subsequently segregate into ciliated and secretory cells (Rock et al. 2011 Pan et al. 2014 To our surprise we have identified mutually exclusive populations of basal cells that express low levels of c-myb and N2ICD (the active Notch2 intracellular domain name). After injury the numbers of these c-myb+ and N2ICD+ basal cells increases dramatically and very rapidly. As epithelial regeneration ensues we show that basal cells that express N2ICD will produce mature secretory cells while the other subset of basal cells that express c-myb will directly give rise to ciliated cells. Thus basal cells can directly produce either ciliated or secretory cell progeny. In aggregate our findings show that basal cells are comprised of a heterogeneous population of stem/progenitor cells. Whether these subpopulations are fixed or occur stochastically and whether they exist within an explicit lineage Calcifediol hierarchy of stem and progenitor cells with different potencies remains to be seen. In general our results point to the notion that seemingly homogeneous stem/progenitor cell populations in many epithelia are likely much more complex than previously thought. Results Expression of Cell Calcifediol Fate Associated Markers in the Airway Basal Cell Compartment Lineage commitment to either secretory or ciliated cell fates following airway injury is currently thought to involve Notch signaling and to occur at an early stage of epithelial regeneration in a set of CK8+ partially differentiated luminal progenitor cells that are derived from basal stem cells (Rock and Hogan 2011 Rock et al. 2011 To our surprise in the homeostatic airway epithelium when we utilized tyramide signal amplification protocols for the immunohistochemical detection of Notch signaling pathway components that had previously been associated with secretory or ciliated cell fate choices (Morimoto 2010; Morimoto 2012) we found expression Calcifediol of these Notch-related proteins in basal cells. This suggested that lineage commitment might be occurring within the basal cell population itself. Specifically we observed cells expressing basal cell markers (p63 CK5 and Pdpn) and c-myb a transcription factor acting downstream of Notch signaling that has been demonstrated to have a conserved role in multiciliogenesis (Tan et al. 2013 and which is required for ciliated.