Physiological Migration of Hematopoietic Stem and Progenitor Cells

TLDR

Hematopoietic stem cells are primarily located in bone marrow, with a small peripheral blood population. The authors tracked blood‑borne HSCs in genetically marked parabiotic mice sharing a common circulation. These cells rapidly engraft partners, sustain hematopoiesis after separation, are cleared quickly from blood, and thus constitutively migrate to support bone marrow reengraftment.

Abstract

Hematopoietic stem cells (HSCs) reside predominantly in bone marrow, but low numbers of HSCs are also found in peripheral blood. We examined the fate of blood-borne HSCs using genetically marked parabiotic mice, which are surgically conjoined and share a common circulation. Parabionts rapidly established stable, functional cross engraftment of partner-derived HSCs and maintained partner-derived hematopoiesis after surgical separation. Determination of the residence time of injected blood-borne progenitor cells suggests that circulating HSCs/progenitors are cleared quickly from the blood. These data demonstrate that HSCs rapidly and constitutively migrate through the blood and play a physiological role in, at least, the functional reengraftment of unconditioned bone marrow.