Pro–angiogenic Induction of Myeloid Cells for Therapeutic Angiogenesis Can Favor MAPK p38–dependent Foam Cell Formation

Clinical trials for therapeutic angiogenesis use blood- or marrow-derived transplants containing hematopoietic cells, endothelial progenitor cells (EPCs) and mesenchymal stem and progenitor cells (MSPCs) to support vascular regeneration. Recently concerns have emerged, as bone marrow-derived stem cell preparations also include these three cell types which probably may contribute to atherosclerosis. We therefore asked whether human myelomonocytic hematopoietic cells, EPCs or MSPCs after pro-angiogenic induction can accumulate lipid droplets (LDs) and develop into foam cells.

LD accumulation was quantified by flow cytometry, confocal microscopy and cholesterol measurement in each of the tested cell types. The impact of an initial three-day pro-angiogenic culture on subsequent foam cell formation was studied to mimic a relevant setting already being used in clinical trials. The phosphorylation state of intracellular signaling molecules in response to pro-angiogenic stimulation was determined to delineate the operative mechanisms and to establish a basis for interventional strategies.

Foam cells were formed by monocytes but neither by EPCs nor by MSPCs after pro-angiogenic induction. Mitogen-activated protein kinase (MAPK) p38 phosphorylation was enhanced in monocytes after pro-angiogenic stimulation. Kinase inhibition almost abrogated intracellular LD accumulation.

These data suggest that hematopoietic cell preparations containing monocytes bear the risk of foam cell formation after pro-angiogenic induction. EPCs and MSPCs instead may drive vascular regeneration without atherogenesis aggravation. A thorough understanding of cell biology is necessary to develop new strategies combining pro-angiogenic and anti-atherogenic cellular effects during therapeutic angiogenesis.

No relevant conflicts of interest to declare.