Hydroxyapatite and calcified elastin induce osteoblast-like differentiation in rat aortic smooth muscle cells

Abstract

Vascular calcification can be categorized into two different types. Intimal calcification related to atherosclerosis and elastin-specific medial arterial calcification (MAC). Osteoblast-like differentiation of vascular smooth muscle cells (VSMCs) has been shown in both types; however, how this relates to initiation of vascular calcification is unclear. We hypothesize that the initial deposition of hydroxyapatite-like mineral in MAC occurs on degraded elastin first and that causes osteogenic transformation of VSMCs. To test this, rat aortic smooth muscle cells (RASMCs) were cultured on hydroxyapatite crystals and calcified aortic elastin. Using RT-PCR and specific protein assays, we demonstrate that RASMCs lose their smooth muscle lineage markers like alpha smooth muscle actin (SMA) and myosin heavy chain (MHC) and undergo chondrogenic/osteogenic transformation. This is indicated by an increase in the expression of typical chondrogenic proteins such as aggrecan, collagen type II alpha 1(Col2a1) and bone proteins such as runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP) and osteocalcin (OCN). Furthermore, when calcified conditions are removed, cells return to their original phenotype. Our data supports the hypothesis that elastin degradation and calcification precedes VSMCs' osteoblast-like differentiation.

Rat Aortic Smooth Muscle Cells Cultured on Hydroxyapatite Differentiate into Osteoblast-Like Cells via BMP-2–SMAD-5 Pathway

“…We have shown earlier that removal of mineral allows Vsmcs to revert back to their original phenotype [19]. Thus it is possible that demineralization strategies could reverse vascular pathology in MAC.…”

“…We have recently shown that osteogenic transdifferentiation of Vsmcs occurs during culture on HA surface and calcified vascular elastin [19]. The aim of the current study is to understand cellular signaling pathways involved in the differentiation of Vsmcs into osteoblast-like cells upon culture on HA surface.…”

Arteriosclerosis and vascular calcification: causes, clinical assessment and therapy

“…The induction of osteoblast-like cell transformation within vascular cells and the active release of nucleation complexes or apoptotic bodies that serve as nucleation site are discussed in both entities [3,5,6]. In addition, endothelial damage, increased level of oxygen species and matrix remodelling are also discussed to be involved [2,[6][7][8][9]. How far both types of calcification share similar pathophysiological mechanisms within the cells is still unclear and under investigation.…”

Development of a Tissue‐Engineered Artificial Ligament: Reconstruction of Injured Rabbit Medial Collateral Ligament With Elastin‐Collagen and Ligament Cell Composite Artificial Ligament

“…In addition, other previous studies have reported that elastin or elastin peptides are associated with cellular differentiation. Lei et al reported that calcified elastin could be used to differentiate rat aortic smooth muscle cells into osteoblast‐like cells , and Hu et al reported that a silk‐tropoelastin film induced the osteogenic differentiation of human bone marrow stem cells . Our histology results revealed that many cells were present at the insertion area of the ligament (Fig.…”