High Phosphate-Induced JAK-STAT Signalling Sustains Vascular Smooth Muscle Cell Inflammation and Limits Calcification

Vascular calcification (VC) is an age-related complication characterised by calcium-phosphate deposition in the arterial wall driven by the osteogenic transformation of vascular smooth muscle cells (VSMCs). The JAK-STAT pathway is an emerging target in inflammation. Considering the relationship between VC and inflammation, we investigated the role of JAK-STAT signalling during VSMC calcification. Human aortic smooth muscle cells (HASMCs) were cultured in high-inorganic phosphate (Pi) medium for up to 7 days; calcium deposition was determined via Alizarin staining and colorimetric assay. Inflammatory factor secretion was evaluated via ELISA and JAK-STAT members' activation using Western blot or immunohistochemistry on HASMCs or calcified aortas of Vitamin D-treated C57BL6/J mice, respectively. The JAK-STAT pathway was blocked by JAK Inhibitor I and Von Kossa staining was used for calcium deposits in murine aortic rings. During Pi-induced calcification, HASMCs released IL-6, IL-8, and MCP-1 and activated JAK1-JAK3 proteins and STAT1. Phospho-STAT1 was detected in murine calcified aortas. Blocking of the JAK-STAT cascade reduced HASMC proliferation and pro-inflammatory factor expression and release while increasing calcium deposition and osteogenic transcription factor RUNX2 expression. Consistently, JAK-STAT pathway inhibition exacerbates mouse aortic ring calcification ex vivo. Intriguingly, our results suggest an alternative link between VSMC inflammation and VC.