Vascular Calcification in Chronic Kidney Disease and Hemodialysis: Pathophysiological Mechanisms and Emerging Biomarkers

<i>Background and Objectives</i>: Vascular calcification (VC) is a major contributor to cardiovascular morbidity and mortality in patients with chronic kidney disease (CKD), particularly those on hemodialysis. Once considered a passive process, VC is now recognized as an active, cell-mediated pathology influenced by mineral dysregulation, chronic inflammation, and oxidative stress. This review aims to synthesize current evidence on the underlying mechanisms of VC in CKD and hemodialysis, with particular focus on emerging biomarkers and therapeutic implications. <i>Materials and Methods</i>: A structured narrative review was conducted by searching PubMed, Web of Science, ScienceDirect, and Google Scholar. The final search was completed on 29 August 2025. A total of 1326 articles were initially retrieved, of which 65 met the inclusion criteria and were analyzed. Studies addressing VC mechanisms, the bone-vascular axis, mineral metabolism, vitamin K-dependent proteins, and biomarkers such as matrix Gla protein (MGP), osteocalcin (OC), and intact parathyroid hormone (iPTH) were included. <i>Results</i>: VC in CKD arises from phenotypic transformation of vascular smooth muscle cells, vesicle-mediated calcification, oxidative stress, and impaired activity of endogenous calcification inhibitors. Disruption of the fibroblast growth factor 23 (FGF23)-Klotho axis and secondary hyperparathyroidism further exacerbate vascular pathology. Among emerging biomarkers, dp-ucMGP reflects vitamin K deficiency and correlates with calcification burden, while OC and iPTH provide insight into bone-vascular crosstalk and mineral turnover. However, biomarker interpretation is limited by assay variability, renal clearance, and clinical heterogeneity. <i>Conclusions</i>: VC in CKD represents a complex process driven by systemic and cellular dysregulation. While biomarkers such as dp-ucMGP, OC, and iPTH offer mechanistic insights and prognostic potential, further validation is required for clinical application. A multimarker approach, combined with individualized management of mineral metabolism, may improve risk stratification and therapeutic targeting in this high-risk population.