Schematic view of the anatomical structure of the human hematopoietic niche. This schema provides a simplified view of the cellular architecture of the human BM niche. It reflects the idea that hHSCs are mainly found in close proximity to the vasculature in direct contact with CD271⁺ MSCs.^3,9  Similar to the mouse BM niche, arterioles and capillaries near the endosteum are ensheated by sympathetic nerve fibers.¹⁰  Surface markers distinguishing different cellular subsets are also indicated. CD146⁺ MSCs are close to the vasculature.¹¹  Nestin and endoglin (CD105) have been proposed to mark arteriolar and sinusoidal ECs, respectively.^5,20