SPP1 and chronic kidney disease: IS induces the expression of runt-related transcription factor 2 (Runx2) and osteopontin (OPN) and activates the PI3K/Akt/NF-κB pathway, all of them participating in the differentiation of vascular smooth muscle cells (VSMCs) from a contractile to osteogenic phenotype thereby promoting vascular calcification in CKD (61–63).