Objective—We used genetically engineered mouse hematopoietic progenitor cells (HPCs) to investigate the therapeutic effects of human apoAI on atherosclerosis in apoE^-/- mice.

Methods and Results—Lentiviral constructs expressing either human apoAI (LV-apoAI) or green fluorescent protein (LV-GFP) cDNA under a macrophage specific promoter (CD68) were generated and used for ex vivo transduction of mouse HPCs and macrophages. The transduction efficiency was >25% for HPCs and >70% for macrophages. ApoAI was found in the macrophage culture media, mostly associated with the HDL fraction. Interestingly, a significant increase in mRNA and protein levels for ATP binding cassette A1 (ABCA1) and ABCG1 were found in apoAI-expressing macrophages after acLDL loading. Expression of apoAI significantly increased cholesterol efflux in wild-type and apoE^-/- macrophages. HPCs transduced with LV-apoAI ex vivo and then transplanted into apoE^-/- mice caused a 50% reduction in atherosclerotic lesion area compared to GFP controls, without influencing plasma HDL-C levels.

Conclusions—Lentiviral transduction of apoAI into HPCs reduces atherosclerosis in apoE^-/- mice. Expression of apoAI in macrophages improves cholesterol trafficking in wild-type apoE-producing macrophages and causes upregulation of ABCA1 and ABCG1. These novel observations set the stage for a cell therapy approach to atherosclerosis regression, exploiting the cooperation between apoE and apoAI to maximize cholesterol exit from the plaque.