佐藤 滋

Cardiac fibroblasts (CFs) are the predominant non-myocyte cell type in the heart and play central roles in extracellular matrix remodeling and intercellular signaling during cardiac physiology and pathology. However, the bioenergetic basis underlying CF functions remains poorly understood, mainly due to the lack of tools for visualizing intracellular adenosine triphosphate (ATP) dynamics with high spatiotemporal resolution. Here, we established immortalized murine cardiac fibroblasts stably expressing the genetically encoded ATP indicator GO-ATeam2 based on Förster Resonance Energy Transfer (FRET). The resulting CF7/GO-ATeam2 cell line allows real-time and quantitative monitoring of cytosolic ATP levels in living cells. CF7/GO-ATeam2 cells exhibited robust proliferation and quick responses to change of cytosolic ATP level. We demonstrated dynamic cytosolic ATP imaging upon pharmacological perturbations of oxidative phosphorylation and glycolysis, as well as under growth factor stimulation. Our work provides the CF7/GO-ATeam2 platform, a versatile cellular resource for dissecting the metabolic regulation of cardiac fibroblasts, offering new opportunities to explore energy dynamics in cardiac physiology and disease.

AIMS: Hypoxia-inducible factor (HIF) signalling influences cardiomyocyte differentiation, maturation, and metabolic adaptation under pathological conditions. HIF-Prolyl hydroxylase domain (HIF-PH) inhibitors, which target this pathway, have been introduced for the treatment of renal anaemia. Their precise effect or safety on cardiac function remains unclear because their pharmacokinetics and distribution are not well-understood. This study aimed to examine HIF signalling activation in adult cardiomyocytes (CMs). METHODS AND RESULTS: We used tamoxifen (TAM)-inducible, CM-specific von Hippel-Lindau (VHL) knockout (VHL-MCM) mice to activate CM HIF signalling. Then we subjected the mice to normal ageing or high-fat diet (HFD) and L-NAME feeding, a murine model of heart failure with preserved ejection fraction (HFpEF). In normal ageing group, there was no difference in the echocardiographic parameters or tissue fibrosis between VHL-MCM and control mice. VHL-MCM mice exhibited significantly increased capillary density and higher expression levels of HIF-target genes (P = 0.0248, two-way ANOVA). Under HFD + L-NAME treatment, VHL-MCM mice showed transient but significantly preserved global longitudinal strain (GLS) at 12 weeks post-TAM injection compared to controls (P = 0.0284, two-way ANOVA). Sirius red staining indicated a trend towards reduced whole-heart and interstitial fibrosis with significant increase in capillary density in VHL-MCM mice. CONCLUSION: Sustained HIF signalling activation in adult CM does not impair the cardiac structure and function in normal ageing process and shows transient yet beneficial effect in murine HFpEF model.