Effect of human apo A-I transfer on endothelial regeneration and EPC incorporation in chimeric C57BL/6 SR-BI^+/+ mice and chimeric C57BL/6 SR-BI^−/− mice. The effect of AdA-I transfer on endothelial cell regeneration in allografts is dependent on SR-BI expression in bone marrow–derived cells. (A) Bar graph showing the number of CD31⁺ endothelial cells at day 21 after artery transplantation in control and AdA-I–treated C57BL/6 mice with SR-BI^+/+ or SR-BI^−/− bone marrow. (B) Bar graph showing the number of CD31 Y-chromosome–positive endothelial cells at day 21 after artery transplantation in control and AdA-I–treated C57BL/6 mice with SR-BI^+/+ or SR-BI^−/− bone marrow. Data are mean plus or minus SEM.