Scube2 Modulates Coronary Vessel Formation During Cardiac Growth and Regeneration in Zebrafish

BACKGROUND: Coronary vessel formation is essential for cardiac growth and regeneration, yet the extracellular mechanisms coordinating coronary vascular remodeling remain incompletely understood. Scube2 (signal peptide-CUB [complement C1r/C1s, Uegf, Bmp1]-EGF domain-containing protein 2) has been implicated in developmental vascular signaling, but its role in coronary vessel formation and cardiac regeneration has not been established. METHODS: We investigated Scube2 function using zebrafish genetic loss-of-function mutants, inducible global and epicardial-specific dominant-negative models, cryoinjury-induced cardiac regeneration, confocal and ultrastructural imaging, bulk RNA sequencing, and biochemical analyses to examine signaling mechanisms. RESULTS: Scube2 was expressed in the epicardium under homeostatic conditions and was rapidly induced in epicardial-derived cells following cardiac injury. Loss of Scube2 impaired developmental coronary vessel formation and caused myocardial ultrastructural abnormalities. Following injury, Scube2 deficiency resulted in defective revascularization, reduced mural cell association, decreased endothelial and cardiomyocyte proliferation, persistent fibrosis, and impaired cardiac regeneration. Temporal and epicardial-specific inhibition of Scube2 recapitulated these regenerative defects. Transcriptomic analyses identified dysregulation of VEGF (vascular endothelial growth factor) and PDGF (platelet-derived growth factor) signaling pathways, accompanied by reduced endothelial proliferation and prolonged inflammatory responses. Mechanistically, SCUBE2 interacted with PDGF-B (PDGF subunit B) and PDGFRβ (PDGF receptor β) and enhanced PDGFRβ activation, supporting a role in endothelial-mural cell communication during vascular remodeling. CONCLUSIONS: Scube2 is a critical regulator of coronary vessel formation and regenerative revascularization in zebrafish. By promoting PDGF-dependent endothelial-mural cell interactions, Scube2 coordinates vascular remodeling that supports myocardial regeneration. These findings identify Scube2 as a previously unrecognized regulator of coronary vascularization and suggest extracellular modulation of PDGF signaling as a potential therapeutic strategy to enhance cardiac repair after ischemic injury.