Diverse contribution of bone marrow-derived late-outgrowth endothelial progenitor cells to vascular repair under pulmonary arterial hypertension and arterial neointimal formation

Abstract Aims It is still controversial whether bone marrow (BM)-derived endothelial progenitor cells (EPCs) can contribute to vascular repair and prevent the progression of vascular diseases. We aimed to characterize BM-derived EPC subpopulations and to evaluate their therapeutic efficacies to repair injured vascular endothelium of systemic and pulmonary arteries. Methods and results BM mononuclear cells of Fisher-344 rats were cultured under endothelial cell-conditions. Early EPCs appeared on days 3–6. Late-outgrowth and very late-outgrowth EPCs (LOCs and VLOCs) were defined as cells forming cobblestone colonies on days 9–14 and 17–21, respectively. Among EPC subpopulations, LOCs showed the highest angiogenic capability with enhanced proliferation potential and secretion of proangiogenic proteins. To investigate the therapeutic effects of these EPCs, Fisher-344 rats underwent wire-mediated endovascular injury in femoral artery (FA) and were concurrently injected intraperitoneally with 60 mg/kg monocrotaline (MCT). Injured rats were then treated with six injections of one of three EPCs (1 × 106 per time). After 4 weeks, transplanted LOCs, but not early EPCs or VLOCs, significantly attenuated neointimal lesion formation in injured FAs. Some of CD31+ LOCs directly replaced the injured FA endothelium (replacement ratio: 11.7 ± 7.0%). In contrast, any EPC treatment could neither replace MCT-injured endothelium of pulmonary arterioles nor prevent the progression of pulmonary arterial hypertension (PAH). LOCs modified protectively the expression profile of angiogenic and inflammatory genes in injured FAs, but not in MCT-injured lungs. Conclusion BM-derived LOCs can contribute to vascular repair of injured systemic artery; however, even they cannot rescue injured pulmonary vasculature under MCT-induced PAH.