Bone marrow-derived endothelial progenitor cells participate in the initiation of moyamoya disease.

The mechanisms through which moyamoya disease occurs and progresses remain unknown. Recent studies have indicated the involvement of circulating endothelial progenitor cells (EPCs) in the development of moyamoya disease. This study directly investigated the participation of EPCs in moyamoya disease, using specimens of the supraclinoid internal carotid artery collected from two adult patients. The specimens were stained with primary antibodies against CD34, CD133, and vascular endothelial growth factor receptor-2 (VEGFR2) to localize the circulating EPCs in the thickened intima of occlusive arterial lesion. The CD34- and VEGFR2-positive cells were densely found in the thickened intima of occlusive arterial lesion, particularly clustered in the superficial layer of thickened intima. However, the number of CD34- and CD133-positive cells was very small. The CD34-positive cells also expressed von Willebrand factor on the surface of thickened intima and were also positive for α-smooth muscle actin in the deeper layer. These findings suggest that circulating EPCs may be involved in the development of occlusive arterial lesion in moyamoya disease.