Interaction of human hematopoietic stem cells and niche

Abstract

Hematopoiesis is a dynamic and strictly regulated process orchestrated by self-renewing hematopoietic stem cells (HSCs) and the supporting microenvironment. However, the exact mechanisms in which individual human HSCs involved to sustain hematopoietic homeostasis remain to be clarified. To understand how the long-term repopulating cell (LTRC) activity of individual human HSCs and the hematopoietic hierarchy are maintained in the BM microenvironment, we traced the repopulating dynamics of human HSC. Our study presented several lines of evidence regarding the in vivo dynamics of human hematopoiesis. We demonstrated that human LTRCs existed in a rare population of CD34^＋CD38^－cells that localized to the stem cell niches and maintained their stem cell activities while being in a quiescent state. We further demonstrated that human mesenchymal stem cells differentiated into key components of the niche and maintained LTRC activity by closely interacting with quiescent human LTRCs, resulting in the increased number of LTRCs.