ATP purinergic receptor signalling promotes Sca-1+ cell proliferation and migration for vascular remodelling.

AIMS: Vascular resident stem cells expressing stem cell antigen-1 (Sca-1+ cells) promote vascular regeneration and remodelling following injury through migration, proliferation and differentiation. The aim of this study was to examine the contributions of ATP signalling through purinergic receptor type 2 (P2R) isoforms in promoting Sca-1+ cell migration and proliferation after vascular injury and to elucidate the main downstream signalling pathways. METHODS AND RESULTS: ATP-evoked changes in isolated Sca-1+ cell migration were examined by transwell assays, proliferation by viable cell counting assays and intracellular Ca2+ signalling by fluorometry, while receptor subtype contributions and downstream signals were examined by pharmacological or genetic inhibition, immunofluorescence, Western blotting and quantitative RT-PCR. These mechanisms were further examined in mice harbouring TdTomato-labelled Sca-1+ cells with and without Sca-1+-targeted P2R knockout following femoral artery guidewire injury. Stimulation with ATP promoted cultured Sca-1+ cell migration, induced intracellular free calcium elevations primarily via P2Y2R stimulation and accelerated proliferation mainly via P2Y6R stimulation. Enhanced migration was inhibited by the ERK blocker PD98059 or P2Y2R-shRNA, while enhanced proliferation was inhibited by the P38 inhibitor SB203580. Femoral artery guidewire injury of the neointima increased the number of TdTomato-labelled Sca-1+ cells, neointimal area and the ratio of neointimal area to media area at 3 weeks post-injury, and all of these responses were reduced by P2Y2R knockdown. CONCLUSIONS: ATP induces Sca-1+ cell migration through the P2Y2R-Ca2+-ERK signalling pathway, and enhances proliferation through the P2Y6R-P38-MAPK signalling pathway. Both pathways are essential for vascular remodelling following injury. Video Abstract.