Vascular remodeling and mobilization of bone marrow-derived cells in cuff-induced vascular injury in LDL receptor knockout mice

BACKGROUND: Vascular remodeling is an important pathologic process in vascular injury for various vascular disorders such as atherosclerosis, postangioplasty restenosis and transplant arteriopathy. Recently, pathologic change and the role of bone marrow derived cells were wildly studied in atherosclerosis and restenosis. But the manner of lesion formation in neointima and cell recruitment in vascular remodeling lesion in the present of hypercholesterolemia is not yet fully understood. METHODS: Double-transgenic mice knockout of LDL receptor gene (LDL -/-) and expressing ubiquitously green fluorescent protein (GFP) were obtained by cross-breeding LDL -/- mice with the GFP-expressing transgenic mice. LDL -/- mice (22 - 24 weeks of age) fed high fat diet containing 1.25% (w/w) cholesterol were subjected to 9Gy irradiation and received bone marrow (BM) cells from the double-transgenic mice. Four weeks later, a nonconstrictive cuff was placed around the right femoral artery. After another 2 weeks, both right and left femoral arteries were harvested and subjected to histochemical analysis. Apoptosis was analyzed in situ using TUNEL assay. RESULTS: Two weeks after cuff placement, atherosclerotic lesions developed in the intima consisting of a massive accumulation of foam cells. The tissue stained with anti-alpha smooth muscle actin (SMA) antibody, showed a number of SMA-positive cells in the intimal lesion area. They were also positive for GFP, indicating that BM-derived cells can differentiate to SMCs in the intima in cuff-induced vascular remodeling lesions. Numerous small vessels in the adventitia as well as the endothelial lining of the intima were positive both for CD31 and GFP. The intima and media showed a large number of TUNEL-positive signals after 2 weeks cuff injury, indicating the presence of apoptosis in vascular remodeling. CONCLUSIONS: Atherosclerotic lesions in mice can be developed in the intima after 2 weeks of cuff-induced vascular injury under the hypercholesterolemic conditions. Our data also clearly indicate that bone marrow-derived cells differentiated to smooth muscles and endothelial cells in the formation of these lesions in the presence of hypercholesterolemia.