SOX9-regulated matrix proteins predict poor outcomes in patients with COVID-19 and pulmonary fibrosis

Pulmonary fibrosis is an increasing and major cause of death worldwide. Understanding the cellular and molecular mechanisms underlying the pathophysiology of lung fibrosis may lead to urgently needed diagnostic and prognostic strategies for the disease. SOX9 is a core transcription factor that has been associated with fibrotic disease, however its role and regulation in acute lung injury and/or fibrosis have not been fully defined. In this study we apply a hypothesis based approach to uncover unique SOX9-protein signatures associated with both acute lung injury and fibrotic progression. Using in vivo models of lung injury in the presence or absence of SOX9, our study shows SOX9 is essential to the damage associated response of alveolar epithelial cells from an early time-point in lung injury. In parallel, as disease progresses, SOX9 is responsible for regulating tissue damaging ECM production from pro-fibrotic fibroblasts. In determining the in vivo role of SOX9 we identified secreted ECM components downstream of SOX9 as markers of acute lung injury and fibrosis. To underscore the translational potential of our SOX9-regulated markers, we analysed serum samples from acute COVID19, post COVID19 and idiopathic pulmonary fibrosis (IPF) patient cohorts. Our hypothesis driven SOX9-panels showed significant capability in all cohorts at identifying patients who had poor disease outcomes. This study shows that SOX9 is functionally critical to disease in acute lung injury and pulmonary fibrosis and its regulated pathways have diagnostic, prognostic and therapeutic potential in both COVID19 and IPF disease. ### Competing Interest Statement The authors have declared no competing interest.