PURPOSE: We aimed to create a time line of disease progression correlating the presentation of EMT and pro-EMT cytokines with clinical events such as acute rejection, infection, and BOS related decline in lung function, highlighting the potential for inhibition of EMT as a therapeutic target.
METHODS: We analyzed 139 post-transplant transbronchial biopsy specimens from multiple patients at several time points between 3-60 months. Using immunohistochemical and immunofluorescence techniques we looked for the onset of co-staining of epithelial and mesenchymal markers such as E-cadherin, Vimentin, and Fibronectin. We then assessed bronchial-alveolar lavage fluid from the same subset of patients for the presence of pro-EMT cytokines including TGF-β-1, TNF-α, and IL-17. Finally, we cultured primary small airway cells with TGF-β-1, TNF-α, and N-acetylcysteine and assessed inhibition of EMT by immunoblot.
RESULTS: We found significantly increased expression of EMT markers in correlation with progressed stage of BOS compared to that of samples taken at stable time points, with the presentation of EMT typically preceding clinically assessed decline in lung function. Presentation of pro-EMT cytokines was associated with clinical episodes such as infection and acute rejection. NAC inhibition of EMT resulted in the preservation of E-cadherin expression and suppression of Vimentin and Fibronectin.
CONCLUSIONS: EMT seems to play a role in the development of BOS, presenting prior to declination of lung function. Myofibroblasts derived via EMT may be the primary source of excess scar tissue occluding the small airways as seen in BOS. Production of pro-EMT cytokines was aggravated by acute rejection and infection and may further instigate EMT and the progression of BOS. Co-therapies aimed at inhibiting EMT have the potential to slow the progression of BOS.
CLINICAL IMPLICATIONS: As presentation of EMT preceded a decline lung function, assessment of EMT may serve as diagnostic tool to detect the onset of BOS earlier than clinical lung function tests. Inhibition of EMT may serve as a therapeutic target in order to slow the progression of BOS. Using EMT inhibiting co-therapies along with current immunosuppressive drug regimens may delay onset of BOS and improve the quality of life for patients post-transplant.
DISCLOSURE: The following authors have nothing to disclose: Valerie Felton, Brenda Pierce, Tony Hodges, Rajat Walia, Ross Bremner, Michael Smith
We will be presenting in-vitro use of N-acetylcysteine to inhibit epithelial-mesenchymal transition and the implications this may have in preventing the development of bronchiolitis obliterans syndrome.