Phosphate dysregulation as a driver of age-related vascular disease

Ectopic calcification in the intimal and medial layers of blood vessels associate with increased risk of cardiovascular morbidity and mortality. Calcification in the medial layer is a hallmark of aging and occurs ubiquitously throughout the vascular tree. Medial calcification is present in >30% of individuals over 60, and causes systemic arterial stiffening leading to heart failure, and in severe disease, critical limb ischemia requiring amputation. This pathology is distinct from intimal calcification localized to atherosclerotic plaques. These vascular calcification subtypes have different risk factors and microenvironments: notably, medial calcification lacks the local inflammatory stimuli typically associated with intimal calcification. Compared to intimal atherosclerotic calcification, medial calcification is relatively understudied leaving gaps in knowledge regarding the mechanisms specifically governing medial calcification. Despite the prevalence, no intervention strategies currently exist to prevent or treat this condition. To address this gap in knowledge, we will systematically compare the mechanisms involved in these two subtypes of calcification using spatially resolved and histology-informed unbiased technologies. The deposition of calcium-phosphate crystal in the vascular wall is regulated by the release of specialized cell-derived extracellular vesicles (EVs). Using proteomics, we identified phosphate-regulating enzymes enriched in EVs derived from arteries with calcification. Abnormalities in phosphate regulation are central to aging and our preliminary findings in whole artery tissue suggest proteomic differences between intimal and calcific lesions may have phosphate metabolism as a distinguishing feature. This preliminary data provides a premise for the central hypothesis that medial and intimal calcification have distinct disease drivers, and medial calcification is distinctly regulated by EV phosphate-mediated mechanisms. In Aim 1, Dr. Turner will use spatial and EV multi-omics to map profiles of disease progression in both medial and intimal calcification lesions compared to non-calcified arterial tissue controls. In Aim 2, she will functionally assess EVs and predicted phosphate modulating disease drivers from each subtype. These studies will be the first interrogation of calcification sub-type resolved disease mechanism. In Aim 3, Dr. Turner will use the -omics and nanoparticle expertise she gained in Aim 1 and Aim 2 to interrogate the proteomic composition of circulating calciprotein particles as a novel biomarker of phosphate status and medial calcification. These findings will provide insight into interventional strategies to mitigate the contribution of phosphate in aging-related medial calcification and push forward the development of tools to identify populations that could benefit from phosphate-targeting interventions. These studies will be conducted under the mentorship of Dr. Elena Aikawa, a pioneer of EV-mediated cardiovascular calcification using systems biology, as well as a committee of professional and scientific advisors committed to Dr. Turner’s success and transition to independence.