Distinct TET Isoform Expression and Functional Responses in Rat Pulmonary Vascular Cells with Implications for PAH Pathogenesis and Therapy

Ten-eleven translocation proteins (TET1-3) are dioxygenases that oxidize 5-methylcytosine, enabling both passive and active DNA demethylation. Hypoxia-induced decrease of TET2 in the lungs and the loss-of-function mutations in TET2 have been identified in patients with pulmonary arterial hypertension (PAH), suggesting that TET-dependent epigenetic mechanisms may contribute to vascular remodeling. However, the relative expression and functional roles of TET1, TET2, and TET3 in pulmonary arterial smooth muscle cells (PASMCs) and endothelial cells (PAECs) remain unclear. Defining these isoform-specific and cell-type differences may help identify new therapeutic angles in PAH. Primary rat PASMCs and PAECs were treated with Bobcat339 (73 μM), which inhibits TET1 and TET2 activity, and incubated for 72 hours at 370C. Levels of Tet1, Tet2, Tet3, Il1b, Myocd, and Myh11 mRNA were measured by qPCR, and TET protein abundance was quantified by ELISA. Proliferation and migration assays were performed to assess functional outcomes. At baseline, both PASMCs and PAECs isolated from rats expressed the highest levels of Tet3, followed by Tet2 and Tet1. ELISA confirmed the same protein hierarchy. Bobcat339 increased Tet3 expression in PASMCs, but not PAECs, suggesting a smooth-muscle–specific compensatory response. Bobcat339 also reduced proliferation and migration in both cell types. In PASMCs, treatment increased Myocd and Myh11 and decreased Il1b, indicating reduced inflammatory signaling and a shift toward a more contractile, less remodeling-prone phenotype. As expected, expression of these smooth-muscle markers remained low in Bobcat-treated PAECs. These findings show that rat pulmonary vascular cells have distinct TET isoform profiles, with TET3 unexpectedly dominant at both the transcript and protein levels. Modulating TET activity produces clear cell-type differences, particularly in PASMCs, and is associated with molecular and functional changes relevant to vascular remodeling. Together, these results support further exploration of TET-based mechanisms as potential contributors to PAH pathogenesis and possible routes for therapeutic modulation. Supported by National Heart, Lung, and Blood Institute grants R01HL132574 (S.A.G. and J.M.M.) and R01HL166546 (S.A.G. and J.M.M.) This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.