All-Trans Retinoic Acid as a Predictor and Therapeutic Agent for Vascular Calcification.

All-trans retinoic acid (ATRA), a bioactive metabolite of vitamin A, is vital for cell development and gene transcription. Coronary artery calcium (CAC) is a risk factor for cardiovascular events but lacks predictive biomarkers and effective treatments. We investigated the correlation between serum ATRA levels and CAC scores in patients, and the potential of ATRA supplementation to alleviate vascular calcification. Proteomic analysis was conducted on rat primary vascular smooth muscle cells (VSMCs) cultured under calcifying conditions. Serum samples from 88 patients with/without CAC were analyzed for ATRA levels and CAC scores. In vivo, vascular classification was established in mice fed a high-fat and high-purine diet with vitamin D3 injection. In vitro, VSMCs were cultured with medium containing 10 mM phosphorus and 3 mM calcium with/without TGF-β (20 and 5 μg/mL) to induce calcification. Single-cell RNA sequencing was performed on mouse aortas. Proteomics showed synchronous downregulation in enzymes involved in ATRA synthesis under calcifying conditions. Serum ATRA levels were negatively correlated with CAC scores in patients. ROC curve analysis revealed an AUC of 0.9135 for ATRA (sensitivity: 73.9%, specificity: 93.3%, and optimal cutoff value: 96.64 pg/mL). In vivo, ATRA alleviated aortic calcification and downregulated RUNX2 and BMP2. In vitro, ATRA reduced calcium deposition and TNF-α and IL-6 in VSMCs. Single-cell RNA sequencing revealed that ATRA downregulated the TNF-α signaling pathways in VSMCs. Our results suggest that low serum ATRA levels may serve as an indicator of vascular calcification, and ATRA supplementation could be an effective therapy.