Differentiation of Vascular Stem Cells Contributes to Ectopic Calcification of Atherosclerotic Plaque

Abstract

The cellular and molecular basis of vascular calcification (VC) in atherosclerosis is not fully understood. Here, we investigate role of resident/circulating progenitor cells in VC and contribution of inflammatory plaque environment to this process. Vessel-derived stem/progenitor cells (VSCs) and mesenchymal stem cells (MSCs) isolated from atherosclerotic ApoE 2/2 mice showed significantly more in vitro osteogenesis and chondrogenesis than cells generated from control C57BL/6 mice. To assess their ability to form bone in vivo, cells were primed chondrogenically or cultured in control medium on collagen glycosaminoglycan scaffolds in vitro prior to subcutaneous implantation in ApoE 2/2 and C57BL/6 mice using a crossover study design. Atherosclerotic ApoE 2/2 MSCs and VSCs formed bone when implanted in C57BL/6 mice. In ApoE 2/2 mice, these cells generated more mature bone than C57BL/6 cells. The atherosclerotic in vivo environment alone promoted bone formation by implanted C57BL/6 cells. Un-primed C57BL/6 VSCs were unable to form bone in either mouse strain. Treatment of ApoE 2/2 VSC chondrogenic cultures with interleukin (IL)-6 resulted in significantly increased glycosaminoglycan deposition and expression of characteristic chondrogenic genes at 21 days. In conclusion, resident vascular cells from atherosclerotic environment respond to the inflammatory milieu and undergo calcification. IL-6 may have a role in aberrant differentiation of VSCs contributing to vascular calcification in atherosclerosis. STEM CELLS 2016;34:913-923 SIGNIFICANCE STATEMENTAlthough chronic heart disease affects over 15 million patients in the United States alone, the pathophysiology of atherosclerosis and vascular calcification is not fully understood. Cues from this study hold promise to unfold the possible mechanisms underlying vascular calcification observed in atherosclerotic plaque. Our data indicates that the atherosclerotic environment has a fundamental effect on resident blood vessel stem/progenitor cells priming them to respond to the local inflammatory milieu to differentiate and calcify. Additionally, we have identified IL-6 as a potential inflammatory mediator. The role of IL-6 presented in this study provides implications for therapeutic applications to prevent vascular calcification.

The crosstalk between vascular MSCs and inflammatory mediators determines the pro-calcific remodelling of human atherosclerotic aneurysm

“…Further confirmation comes from the differentiation assays, showing higher mineralization activity under AAA-PBMC influence. These data support the role of vascular MSCs in the development of arterial calcification, in accordance with the literature on MSCs obtained from animal models [29, 30]. …”

“…A Recent work on a murine model of atherosclerosis demonstrates the involvement of vascular progenitor cells in aortic atherosclerosis as well as in ectopic calcification, under inflammatory conditions [29]. Even the genetic ablation of adventitial Gli1 + MSC-like cells in atherosclerotic mice affected by chronic kidney disease drastically decreases the level of vascular calcification [30].…”

Estrogen Receptor Control of Atherosclerotic Calcification and Smooth Muscle Cell Osteogenic Differentiation

“…There is growing evidence that calcifying medial cells derive from various sources, such as adventitial mesenchymal stem-cell-like cells, myofibroblasts, or subintimal pericytes; proportions of these osteoprogenitors may differ between vascular beds and may also contribute to site-specificity. 17,[58][59][60] Further studies are required to examine these hypotheses or whether other genetic or environmental factors may influence local plaque mineralization. 52 Our findings in female apolipoprotein E-deficient mice, that E2 does not cause regression of lesions once established and no longer growing, is in keeping with past clinical HRT trials, which suggest that short-term HRT may not consistently prevent progression or destabilization of established atherosclerotic lesions in the coronary arteries of postmenopausal women.…”

“…There is growing evidence that calcifying medial cells derive from various sources, such as adventitial mesenchymal stem-cell-like cells, myofibroblasts, or subintimal pericytes; proportions of these osteoprogenitors may differ between vascular beds and may also contribute to site-specificity. 17,[58][59][60] Further studies are required to examine these hypotheses or whether other genetic or environmental factors may influence local plaque mineralization. …”

Human Cord Blood‐Derived CD133+/C‐Kit+/Lin− Cells Have Bipotential Ability to Differentiate into Mesenchymal Stem Cells and Outgrowth Endothelial Cells

“…Various cues within the microenvironment such as cell-cell contact, mechanical forces, soluble factors, and extracellular interactions are involved in the fate-determination steps of stem cells [27–30]. To date, however, soluble factors that contribute to lineage-specific differentiation of CKL− cells are not well studied.…”