Lund, Andrew

Mentor: Dr. Brigitte Gomperts

Research project:

Cystic fibrosis (CF) is an autosomal recessive disorder caused by mutation of the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR), an ion channel that transports chloride and bicarbonate ions across the apical surface of epithelial cells. While the pathological consequences of CFTR dysfunction are manifold and systemic, CF-related lung disease is the leading cause of mortality in those afflicted. Within the proximal airway, two dedicated stem cell populations have been recognized: the basal cells of the luminal epithelium and their glandular counterparts, the “basal-like” duct stem cells. Our group, in collaboration with a multi-institute consortium, observed a reduction in the luminal basal cell subpopulation with a proliferative signature in bronchial tissue from patients with end-stage CF-related lung disease compared to healthy donor tissue by single-cell RNA sequencing (scRNA-seq.) However, submucosal gland (SMG) duct cells, which are capable of begetting basal cells upon airway injury, may be tapped to act in a compensatory capacity, potentially accounting for adverse architectural differences observed in the CF airway. In particular, CF is associated with hypertrophied SMGs and their expansion into distal airways, presumably driven by modifications of the SMG niche.

A critical determinant of niche dynamics is the surrounding mesenchyme; epithelial-mesenchymal crosstalk regulates homeostasis and directs the repair response upon insult. Moreover, airway regeneration is generally mediated by the reactivation of developmental programs. Specifically, canonical WNT/β-catenin signaling has been implicated as a critical determinant of airway morphogenesis. Dysregulation of the reciprocal interactions between epithelial and mesenchymal cells could drive the aberrant activation of SMG duct cells to produce the expanded SMG phenotype; accordingly, CFTR deficiency potentiates glandular secretions, which correlates with depletion of slow-cycling label-retaining cells from the SMG and their collateral redistribution within the surface airway epithelium. Therefore, further investigation of the local microenvironment is warranted to gain a more comprehensive understanding of niche components and the changes underlying CF pathophysiology.

Our research aims to determine cell-cell and cell-matrix interactions within the SMG microenvironment that modulate WNT signaling and duct cell behavior by leveraging advancements in high throughput sequencing and proteomics techniques with spatial resolution. Specifically, we will perform scRNA-seq to capture the transcriptome of airway submucosal epithelial and mesenchymal cells, which we will integrate with our luminal epithelial single-cell data to conduct “connectomics” analysis of cell-cell interaction networks. Further, we will implement imaging mass spectrometry techniques to interrogate changes in the distribution of extracellular matrix composite biomaterials and associated morphogens between CF and healthy tissue. We anticipate this systems-level approach will achieve unprecedented profiling of the SMG niche and delineation of the interactions amongst constituent cells and biomaterials, which will further promote translational research and development of improved models of human airways.