THE CONTRIBUTION OF HIGH-PHOSPHORUS IN EXTRACELLULAR MATRIX ACCUMULATION OF VALVULAR CALCIFICATION IN CHRONIC KIDNEY DISEASE

Abstract Background and Aims The characteristics of valvular calcification (VC) in early stage are extracellular matrix (ECM) accumulation and muti-cells activation. In our previous work, we found high-phosphorus (HP) diet aggravated ECM accumulation in both aortic valve and mitral valve in rats with chronic kidney disease (CKD). However, the underlying mechanism of HP contribution in ECM accumulation of CKD-induced VC is still unknown. Method canine valvular interstitial cells (VICs), valvular endothelial cells (VECs) and human umbilical vein endothelial cells (HUVECs) were used in this study. CKD mice (C57b and Tek-EGFP-PolyA) was build by 0.2% adenine-diet for 6 weeks and HP diet/NP diet for 10 weeks. Results As for VICs, HP induced qVICs transfer into aVICs, not oVICs, which was characterized with upregulated level of smoothelin and viemitin. There was no calcium accumulation was observed, suggesting that VICs do not have the ability to synthesize calcium crystals under pure HP intervention. As for VECs, aVICs activated by HP induced VECs EndMT in a transwell-assay, which was characterized with decreasing protein levels of endothelial markers (CD31, vWF, VE-cadherin) and increasing protein levels of mesenchymal makers (α-SMA, FSP1, N-cadherin). Then, IL-8 was found as the main factor releasing from VICs to induce VECs EndMT. In vitro, the concentration of IL-8 in the lower chamber could reach 2-4ng/ml. Reparixin was used to inhibit IL-8 receptor of VECs, which could relive aVICs-induced EndMT. In vivo, the expression of valve CXCL-2 (the mouse IL8 functional homolog) was increased in HP-diet compared with NP-diet, though the serum level of CXCL-2 was similar between two groups. AAV9-sm22a-CXCL-2 and Reparixin could inhibit VECs EndMT by inhibiting VICs relasing CXCL-2 and inhibiting VECs IL-8 receptor in CKD mice of Tek-EGFP-PolyA respectively. Then, IL-8 was found to induced VECs EndMT by miR-214-3p/PTEN/Akt pathway. Inhibiting EndMT by blocking IL-8/miR-214-3p could alleviate ECM accumulation. Conclusion HP could induce qVICs transfer into aVICs, and aVICs could cause VECs EndMT via IL-8/miR-214-3p/PTEN/Akt pathway. Both take part in ECM accumulation in CKD-induced VC.