RyR2 Gain-of-Function Increases Ca2+ Spark and Ca2+ Wave Activity in Vascular Smooth Muscle Cells

Ca2+ sparks in vascular smooth muscle cells (VSMCs) regulate vascular function, and their dysregulation with ageing may contribute to vascular disease. These localized Ca2+ signals originate from ryanodine receptors (RyRs) and can initiate propagating Ca2+ waves that modulate vascular tone. However, it is still unclear which RyR isoform (RyR1, RyR2, or RyR3) primarily drives these Ca2+ signals in arterial VSMCs, as all three are present. The RyR2 contribution to vascular Ca2+ signaling was analyzed using Ca2+ sparks and waves in arterial VSMCs isolated from mice carrying the RyR2R4496C mutation. Intracellular Ca2+ signals were recorded using a fluorescent Ca2+ indicator in VSMCs from both young and older mice. Caffeine-evoked Ca2+ responses and contractions were measured to assess RyR-mediated SR Ca2+ release and vascular reactivity. VSMCs from young RyR2R4496C mice exhibited a significantly higher frequency of Ca2+ sparks and a greater percentage of cells displaying Ca2+ sparks and propagating Ca2+ waves compared with controls. The RyR2R4496C mutation enhanced RyR2 sensitivity to caffeine, resulting in larger increases in intracellular [Ca2+]i and arterial contractions in older mice. These findings demonstrate that RyR2 gain-of-function increases Ca2+ spark and Ca2+ wave activity in VSMCs, supporting a role for RyR2 in the regulation of local and propagating Ca2+ signals. Dysregulated RyR2 activity may therefore contribute to altered vascular Ca2+ signaling and could represent a potential mechanistic link to vascular dysfunction associated with ageing and metabolic stress.