Sources of cells that contribute to atherosclerotic intimal calcification: an in vivo genetic fate mapping study

Abstract

Our results are the first to definitively identify cell sources attributable to atherosclerotic intimal calcification. SMCs were found to be a major contributor that reprogrammed its lineage towards osteochondrogenesis. Marrow-derived cells from the circulation also contributed significantly to the early osteochondrogenic differentiation in atherosclerotic vessels.

Runx2 deletion in smooth muscle cells inhibits vascular osteochondrogenesis and calcification but not atherosclerotic lesion formation

“…HFD feeding induced atherosclerotic lesion formation ( Figure 1C Figure 1E), notably in deep intima and the inner layers of media underneath atherosclerotic lesions, areas where osteochondrogenic differentiation of vascular SMCs initiates. 12 Quantitation of percent Runx2 immunoactivity ( Figure 1G) and Runx2 mRNA levels ( Figure 1H) in aortic arches of these mice verified statistically lower levels of Runx2 in LDLr À/À :Runx2 DSM vessels in comparison to LDLr À/À :Runx2 f/f vessels. HFD feeding induced Runx2 mRNA levels in aortic arch by $2.8 fold compared to NC feeding.…”

“…BUN levels were slightly higher in LDLr À/À :Runx2 DSM mice in comparison to LDLr À/À :Runx2 f/f mice, but were well within the reported normal range. 12,25 These data suggest that removal of Runx2 in SMCs does not affect systematic lipid metabolism or mineral homeostasis in LDLr À/À mice.…”

“…These mice were fed a high fat diet (HFD; Research Diets Inc., 1.25% cholesterol, 39.9% kcal fat, 40% kcal carbohydrate) at 10 weeks of age to induce atherosclerosis, vascular cartilaginous metaplasia, and calcification as previously described. 12 Normal chow (NC) was used as a dietary control for each genotype. Body weight was recorded and fasting serum collected before the diet challenge and at termination.…”

“…8 Although initially considered a passive, uncontrollable process, recent evidence supports AIC as an actively regulated process with similarities to bone development, including the appearance of calcified cartilage-and bone-like structures within le-sions. [9][10][11] Lineage tracing studies in mouse models have shown that vascular smooth muscle cells (SMCs) can transdifferentiate into osteochondrogenic cells, 12,13 implicating these cells as important mediators of AIC. However, the mechanisms by which SMCs transdifferentiate and contribute to plaque mineralization are not well understood.…”

“…12,13 In humans, mutations in the Runx2 gene are associated with cleidocranial dysplasia, a disorder characterized by delayed ossification of midline structures, especially the collarbone and cranium. 18 In mice, the global deletion of Runx2 is perinatal lethal due to the lack of skeletal mineralization and respiratory failure.…”