Influence of Pkm2-->1 isoform switching on the cardiac fibroblasts transcriptome

Cardiac fibroblasts (CFs) are essential for maintaining tissue integrity and the balance of the extracellular matrix (ECM), both of which are critical for normal heart function. Changes in metabolism can influence CF behavior, with activated fibroblasts often exhibiting distinct metabolic shifts. Pyruvate kinase, a key metabolic enzyme, has two isoforms—Pkm1 and Pkm2—produced through alternative splicing. CFs primarily express the Pkm2 variant rather than Pkm1. While Pkm2 is known to regulate gene transcription in various cell types, its role in CF gene expression is not well understood. In this study, we examined how pyruvate kinase splice variants influence CF gene transcription under baseline conditions and following activation by TGF-β or IL-1β. Our results indicate that switching from the Pkm2 to the Pkm1 variant had no significant effect on CF transcriptional regulation, regardless of ligand-induced activation. Isolated cardiac fibroblasts from Pkm2fl/fl mice were transduced with LacZ or iCre prior to stimulation with bFGF, IL-1b, or TGFb for 24 hours.