Transcription Factor p63 Regulates Key Genes and Wound Repair in Human Airway Epithelial Basal Cells

The airway epithelium in asthma displays altered repair and incomplete barrier formation. Basal cells are the progenitor cells of the airway epithelium, and can repopulate other cell types after injury. We previously reported increased numbers of basal cells expressing the transcription factor p63 in the airway epithelium of patients with asthma. Here we sought to determine the molecular consequences of p63 expression in basal human airway epithelial cells during wound repair. Because at least six isoforms of p63 exist (N-terminally truncated [Delta N] versus transcriptional activation promoter variants and alpha, beta, or gamma 3' splice variants), the expression of all isoforms was investigated in primary human airway epithelial cells (pHAECs). We modulated p63 expression, using small interfering RNA (siRNA) and adenoviral constructs to determine the effects of p63 on 21 candidate target genes by RT-PCR, and on repair using a scratch wound assay. We found that basal pHAECs from asthmatic and nonasthmatic donors predominantly expressed the N-terminally truncated p63 alpha variant (Delta Np63 alpha) isoform, with no disease-specific differences in expression. The knockdown of Delta Np63, using specific siRNA, decreased the expression of 11 out of 21 genes associated with epithelial repair and differentiation, including beta-catenin, epidermal growth factor receptor, and Jagged1. The loss of Delta Np63 significantly inhibited wound closure (which was associated with the decreased expression of beta-catenin and Jagged1), reduced epithelial proliferation as measured by Ki-67 staining, and increased E-cadherin expression, potentially preventing cytokinesis. In conclusion, Delta Np63 alpha is the major isoform expressed in basal pHAECs, and is essential for epithelial wound repair. The role of Delta Np63 alpha in epithelial barrier integrity requires further study to understand its role in health and disease.