Matrix Vesicles from Osteoblasts Promote Atherosclerotic Calcification

Abstract Backgrounds Vascular calcification often occurs with osteoporosis, a contradictory association known as “the calcification paradox”. Osteoblast-derived matrix vesicles (Ost-MVs) have been implicated in bone mineralization, and also have a potential role in ectopic vascular calcification. Herein, we aim to investigate the contributions that Ost-MVs make to the bone–vascular calcification paradox and the underlying mechanisms. Methods and Results Hyperlipidemia-induced atherosclerotic calcification in mice was accompanied with bone mineral loss, as evidenced by reduced deposition of Ost-MVs in the bone matrix and increased release of Ost-MVs into the circulation. Intravenous injection of fluorescent DiІ-labeled Ost-MVs revealed a marked fluorescence accumulation in the aorta of atherogenic mice, whereas no fluorescence signals were observed in normal controls. Using proteomics to analyze proteins in non-matrix bound Ost-MVs and mineralized SMC-derived MVs (SMC-MVs), we found Lamp1 was specifically expressed in SMC-MVs, and Nid2 was exclusively expressed in Ost-MVs. We further demonstrated that both Lamp1 and Nid2 were co-localized with Collagen І within calcific plaques, indicating the involvement of both Ost-MVs and SMC-MVs in atherosclerotic calcification. Mechanistically, LPS-induced vascular injury facilitated the transendothelial transport of Ost-MVs. The recruitment of circulating Ost-MVs was regulated by remodeled Collagen І during calcification progression. Furthermore, the phenotypic transition of SMCs determined the endocytosis of Ost-MVs. Finally, we demonstrated that either recruited Ost-MVs or resident SMC-MVs accelerated atherosclerotic calcification, depending on the Ras-Raf-ERK signaling. Conclusion Atherosclerotic calcification-induced Ost-MVs are released into circulation, facilitating the transport from bone to plaque lesions and exacerbating artery calcification progression. The mechanisms of Ost-MVs recruitment include vascular injury allowing transendothelial transport of Ost-MVs, collagen І remodeling promoting Ost-MVs aggregation, and SMC phenotypic switch to facilitate Ost-MVs uptake. Our results further revealed that both recruited Ost-MVs and calcifying SMC-MVs aggravate calcification through the Ras-Raf-ERK pathway.