NTRK2 and hydrops fetalis: To explore the biological pathways and functions of these cell subtypes in HF development, enrichment analysis revealed that pericytes and smooth muscle cells were significantly associated with ATP-sensitive potassium channels and BDNF activation of NTRK2 (TRKB) signaling, while NK&T cells and B cells were predominantly enriched for activation of Na-permeable kainate receptors and hydroxycarboxylic acid-binding receptors (Figure 8c).