Novel Models to Define the Role of Aberrant T Cell Subsets in Scleroderma Pulmonary Fibrosis

About This Grant

ABSTRACT Scleroderma or Systemic Sclerosis (SSc) is a rare autoimmune connective tissue disease with high morbidity and mortality. There are currently no effective treatments to cure SSc underscoring the need to better understand the interplay of immune cells, vascular damage and fibrosis that underlies disease progression. SSc often leads to severe lung pathology, including pulmonary fibrosis, which is the main cause of death in SSc patients. Although a role for T cells in pulmonary fibrosis is increasingly recognized, the underlying mechanisms remain poorly understood. Here we will develop improved and advanced murine and human models to study the role of T cells in SSc pulmonary fibrosis. In the first Aim we will adapt the sclerodermatous Graft vs Host Disease (scGvHD) murine model of SSc, which exhibits T cell-driven fibrosis but with rather limited lung involvement. We will increase SSc lung disease in this model by chemical treatment of the lungs and identify T cell subsets that drive the fibrogenic response, as well as T cell subsets that attempt to control or repair dysfunctional fibroblasts. Central to our approach will be the use of precision-cut lung slices (PCLS) to test the functional role of T cell subsets present in the lungs of scGvHD mice. PCLS are sensitive to fibrosis induction while maintaining all cell types and tissue architecture intact. Co-culture of healthy PCLS with T cell subsets from fibrotic lungs will reveal their potency to promote fibrosis. PCLS with pulmonary fibrosis will be used to test the ability of anti-fibrotic T cell subsets to repair the damage. In the second Aim, we will establish co-cultures of PCLS from human lung explants and T cells from SSc patients or healthy individuals. We predict that the T cell pool from SSc patients will have increased capacity to induce and sustain pulmonary fibrosis in PCLS, compared to the T cell pool from healthy donors. Next, we will analyze the function of a specific T cell subset that we found to be expanded in SSc peripheral blood and can also be found in SSc lungs. This subset expresses high levels of the co-inhibitory receptors PD-1 and TIGIT and shows features of exacerbated exhaustion in SSc patients compared to the equivalent population in healthy subjects. Notably, PD-1+TIGIT+ T cells from SSc patients were deficient in the production of the anti-fibrotic cytokines IFN-γ and TNF-α. We will test the hypothesis that this expanded PD-1+TIGIT+ T cell subset has lost its anti-fibrotic potential in co- cultures with PCLS that exhibit induced fibrosis. Thus, this experiment will reveal how defective anti-fibrotic T cells play a role in enabling the fibrogenic response to proceed during pulmonary fibrosis. Moreover, this PCLS/T cell co-culture model will allow to test interventions that restore the function of anti-fibrotic T cells or target pro-fibrotic mediators to resolve pulmonary fibrosis, providing a preclinical testing model to develop novel anti-fibrotic strategies for SSc patients.