The IL-33 Receptor/ST2 acts as a positive regulator of functional mouse bone marrow hematopoietic stem and progenitor cells

There is a paucity of information on a potential role for the IL-33 receptor/ST2 in the regulation of mouse bone marrow (BM) hematopoietic stem (HSC) and progenitor (HPC) cells. Comparing the BM of st2(-/-) and wild type (WT) control mice using functional assays, it was found that st2(-/-) BM cells had poorer engrafting capacity than WT BM in a competitive repopulating assay using congenic mice, with no changes in reconstitution of B-, T- and myeloid cells following transplantation. The BM of st2(-/-) mice also had fewer granulocyte-macrophage, ery- throid, and multipotential progenitors than that of WT BM and these st2(-/-) HPC were in a slow cycling state compared to that of the rapidly cycling HPC of the WT mice. While functional assessment of HSC and HPC demonstrated that ST2 has a positive in fluence on regulation of HSC, we could not pick up di fferences in st2(-/-) compared to WT BM using only phenotypic analysis of HSC and HPC populations prior to transplantation, again demonstrating that phenotypic analysis of HSC and HPC do not always recapitulate the functional assessments of these immature hematopoietic cells.