Airway epithelial cell reprogramming mechanisms leading to chronic lung allograft dysfunction

About This Grant

PROJECT SUMMARY Chronic lung allograft dysfunction (CLAD) limits survival after lung transplantation and there are no approved therapies to prevent inexorable declines in lung function. Transplant pulmonologists have been using mTOR inhibitors off label, and there are some promising data to support this practice. However, we lack key knowledge to guide their use. We have developed airway brush gene scores to assess inflammation that is undetectable on transbronchial biopsies but associated with risk of CLAD and death. Specifically, we found that mTOR signaling is an early hallmark of CLAD. Our single cell sequencing studies have linked mTOR gene expression in basal and club cells to the transition from acute lung allograft dysfunction (ALAD) to CLAD. In airway cell culture models, mTOR-associated gene expression was linked to epithelial to mesenchymal transition (EMT), which is a hallmark of CLAD. We also observe mTOR signaling in mouse models of acute and chronic lung transplant rejection. Paradoxically, we found that recipients who failed to respond to mTOR inhibitors had higher mTOR signaling in their airways, suggesting that the lack of response may result from dose-limiting toxicities. To address this issue, our center is conducting a trial of inhaled mTOR inhibitors, the INSPO trial, that could deliver more potent suppression of mTOR in the airways. Building on these data, this proposal will test the hypothesis that mTOR signaling drives CLAD through airway epithelial cell reprogramming. Aim 1 will test whether mTOR signaling during ALAD is a predictive biomarker of ALAD and CLAD progression. Using bio-banked samples from UCSF lung transplant recipients, we will analyze mTOR gene scores across airway brushes, BAL, and transbronchial biopsies and determine their links to ALAD progression and CLAD pathology. Aim 2 will examine mTOR inhibition in a mouse lung transplant model. We will quantify airway fibrosis and EMT pathology with and without mTOR inhibition. Using a transgenic model lacking mTOR in airway epithelial cells, we will examine airway-specific EMT-associated reprogramming. Aim 3 will determine how mTOR inhibition impacts human airway epithelial reprogramming. We will culture human airway cells to see if mTOR inhibitors can blunt EMT phenotypes. We will also leverage BAL and airway brush single cell data from the INSPO study, a randomized controlled trial of inhaled mTOR inhibitors, to quantify the effects of mTOR suppression in airway epithelial and immune cells. This highly feasible study leverages an extensive biorepository, an innovative clinical trial, and proven state of the art approaches. By understanding the cell-specific mechanisms of mTOR signaling in CLAD, this proposal will enable appropriate mTOR targeting to improve survival and lung function following lung transplantation.