Figure 1.
Reconstitution of apoE–/– mice with BM lacking p27 accelerates diet-induced atherosclerosis. One month after transplantation, mice were challenged with a high-cholesterol diet for 2 months. Animals were then killed and aortic tissue was retrieved to quantify atherosclerosis (A, B) and for immunohistochemical analysis (C-E). Results in A and B are given as mean ± SE, and differences between groups were evaluated using 2-tailed, unpaired Student t test. (A) The aorta was removed from the heart to the renal artery and was stained with Oil Red O. The area of atheroma (red staining) was quantified by computerized planimetry. Results are represented relative to total aortic area. The photomicrographs show representative examples. (B) Cross-sections of the aortic arch region were analyzed to measure the area of atheroma (intimal lesion) and media to determine the intima-to-media ratio. The red horizontal bars show the average value in each group. The representative photomicrographs in B show specimens doubly immunostained with antibodies against the macrophage-specific Mac-3 protein (brown signal) and the smooth muscle–specific α isoform of actin (SMα-actin; red signal). The discontinuous lines mark the boundary between the tunica media and the atheroma. The bars represent 0.2 mm. (C-E) Immunohistochemistry of aortic arch cross-sections. Each pair of photomicrographs correspond to immediately adjacent cross-sections of the same mouse (bars represent 100 μm). Mac-3 and PCNA are shown in brown, and SMα-actin in red. Analysis included double immunohistochemistry using the indicated pairs of antibodies (C, D) and single immunostaining using anti–Mac-3 and anti-PCNA antibodies (E). For double immunhistochemistry, specimens were first stained for either PCNA or Mac-3, and then with the alkaline phosphatase– conjugated anti–SMα-actin antibody. In both groups of mice, abundant immunoreactivity for Mac-3 and SMα-actin is detected within the atheroma and the media, respectively, and PCNA expression predominates in macrophage-rich regions of atheromas.