Regulation of inflammatory lung injury and repair by transforming growth factors

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are inflammatory conditions with substantial rates of morbidity and mortality, but no effective treatments. The lack of effective treatments and unacceptably high mortality rates for ARDS are partly due to an incomplete understanding of the mechanisms that control ALI/ARDS and subsequent vascular repair. Transforming growth factors (TGFs) are a class of growth factors that regulate the vascular response to inflammation, including migration, proliferation, and differentiation of cells comprising the lung vasculature. Here we review studies that describe the impact of the TGF family on inflammatory lung injury and subsequent vascular repair and fibrosis. We highlight gaps in understanding TGF isoform-specific roles in ALI/ARDS and outline directions for future research in the field of TGF-dependent regulation of inflammatory lung injury and vascular repair. Functional roles of the TGFs have been investigated in ALI/ARDS pathogenesis and pulmonary fibrosis, with a predominance for studies showing a proinjurious and profibrotic impact of TGF-β1. Studies have also shown that TGF-α is positively associated with inflammatory lung injury and fibrosis. However, the contributions of TGF-β2 and TGF-β3 to ALI/ARDS are unclear, and the contributions of all the TGF isoforms to vascular repair after ALI/ARDS are not well characterized. Improved understanding of the regulation of inflammatory lung injury and repair by the TGFs could lead to the development of a safe and effective treatment strategy for patients with ALI/ARDS.