End stage renal disease‐induced hypercalcemia may promote aortic valve calcification via Annexin VI enrichment of valve interstitial cell derived‐matrix vesicles

Abstract

Patients with end‐stage renal disease (ESRD) have elevated circulating calcium (Ca) and phosphate (Pi), and exhibit accelerated progression of calcific aortic valve disease (CAVD). We hypothesized that matrix vesicles (MVs) initiate the calcification process in CAVD. Ca induced rat valve interstitial cells (VICs) calcification at 4.5 mM (16.4‐fold; p < 0.05) whereas Pi treatment alone had no effect. Ca (2.7 mM) and Pi (2.5 mM) synergistically induced calcium deposition (10.8‐fold; p < 0.001) in VICs. Ca treatment increased the mRNA of the osteogenic markers Msx2, Runx2, and Alpl (p < 0.01). MVs were harvested by ultracentrifugation from VICs cultured with control or calcification media (containing 2.7 mM Ca and 2.5 mM Pi) for 16 hr. Proteomics analysis revealed the marked enrichment of exosomal proteins, including CD9, CD63, LAMP‐1, and LAMP‐2 and a concomitant up‐regulation of the Annexin family of calcium‐binding proteins. Of particular note Annexin VI was shown to be enriched in calcifying VIC‐derived MVs (51.9‐fold; p < 0.05). Through bioinformatic analysis using Ingenuity Pathway Analysis (IPA), the up‐regulation of canonical signaling pathways relevant to cardiovascular function were identified in calcifying VIC‐derived MVs, including aldosterone, Rho kinase, and metal binding. Further studies using human calcified valve tissue revealed the co‐localization of Annexin VI with areas of MVs in the extracellular matrix by transmission electron microscopy (TEM). Together these findings highlight a critical role for VIC‐derived MVs in CAVD. Furthermore, we identify calcium as a key driver of aortic valve calcification, which may directly underpin the increased susceptibility of ESRD patients to accelerated development of CAVD.

Extracellular vesicles in cardiovascular homeostasis and disease

“…In valve interstitial cells, elevated extracellular calcium and phosphate induce release of EVs enriched with Annexin VI [21*]. Similar to its function in vascular SMCs, Annexin VI mediates calcium binding in EVs, promoting mineral formation.…”

Медикаментозная Коррекция Нарушений Фосфатно-Кальциевого Обмена У Пациентов С Хронической Болезнью Почек И Минерально-Костной Болезнью

“…Гиперкальциемия тесно связана с развитием и усугублением течения таких заболеваний, как ате-росклероз, микроангиопатии различного генеза, играет ключевую роль в патогенезе кальциноза аор-тального клапана [6].…”

How To Build a Bone: PHOSPHO1, Biomineralization, and Beyond

“…Their function continues to be remain controversial since their discovery in 1967 in growth plate cartilage, with some authors attributing these as specimen‐preparation artifacts . Nevertheless, many in vitro and in vivo studies have shown the first mineral crystals in diverse mineralized tissues such as bone, dentin, cartilage, and mineralized vasculature are associated with these structures in the extracellular matrix (ECM) …”

“…(56) Nevertheless, many in vitro and in vivo studies have shown the first mineral crystals in diverse mineralized tissues such as bone, dentin, cartilage, and mineralized vasculature are associated with these structures in the extracellular matrix (ECM). (55,(57)(58)(59)(60)(61)(62)(63) The structure and function of MVs in skeletal and vascular mineralization has recently been reviewed by several authors. (53,(64)(65)(66)(67) The biogenesis of these vesicles may occur through multiple proposed mechanisms; however, the most prevalent theories include polarized budding from the parental cell membrane, or from microvilli on the cell surface, as demonstrated in hypertrophic chondrocytes and SaOS-2 osteoblast-like cells.…”