Bone Marrow–Derived Cells and Vascular Growth
To the Editor:
We read with great interest the study by Ziegelhoeffer et al,1 who tested whether circulating bone marrow–derived cells incorporate into collateral arteries after femoral artery ligation. Although the investigators did not find any incorporation of bone marrow–derived cells in the endothelium and tunica media of growing vessels, they observed accumulations of bone marrow–derived cells in areas of collateral artery growth and capillary growth and identified these cells as fibroblasts, pericytes, and primarily leukocytes. These exciting data add another piece of evidence to the concept that apparently not mural, tissue-resident cells but other cell types play a more central role in vascular repair.
Given the diversity of blood leukocyte populations, the exact identity of these cells deserves careful consideration. In this context, we recently identified dendritic cells as a novel neointimal cell type and demonstrated their maximal frequency during early neointima formation after rat carotid balloon injury.2 In another study, we also showed bone marrow– and neural crest–derived cells within human in-stent restenosis atherectomy samples.3 Herein, dendritic cells constituted the major mononuclear lesional cell type, whereas monocytes/macrophages were confined to areas adjacent to stent struts.3 It is tempting to speculate that dendritic cells may have contributed to the bone marrow–derived perivascular leukocyte populations described by Ziegelhoeffer et al.1 Because most dendritic cells are thought to originate from hematopoietic stem cells and to share initial differentiation steps with monocytes,4 we also would like to suggest that further studies on vascular repair should evaluate the presence of specific subpopulations of the monocyte/macrophage cell lineage as well as the role of dendritic cells.
Ziegelhoeffer T, Fernandez B, Kostin S, Heil M, Voswinckel R, Helisch A, Schaper W. Bone marrow–derived cells do not incorporate into the adult growing vasculature. Circ Res. 2004; 94: 230–238.
Skowasch D, Jabs A, Andrié R, Dinkelbach S, Lüderitz B, Bauriedel G. Presence of bone-marrow- and neural-crest-derived cells in intimal hyperplasia at the time of clinical in-stent restenosis. Cardiovasc Res. 2003; 60: 684–691.