Engraftment, Fate, and Function of HoxB8-Conditional Neutrophil Progenitors in the Unconditioned Murine Host.

Brittany M. Neumann,Renita Johnson,Anna Chorzalska,Zachary S. Wilson,Kristina D. Hinman,Patrycja M. Dubielecka,Craig T. Lefort,Joshua T. Cohen,Michael Danise

doi:10.3389/fcell.2022.840894

Brittany M. Neumann, Renita Johnson + Show 7 more

Open Access

https://doi.org/10.3389/fcell.2022.840894

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Abstract

The development and use of murine myeloid progenitor cell lines that are conditionally immortalized through expression of HoxB8 has provided a valuable tool for studies of neutrophil biology. Recent work has extended the utility of HoxB8-conditional progenitors to the in vivo setting via their transplantation into irradiated mice. Here, we describe the isolation of HoxB8-conditional progenitor cell lines that are unique in their ability to engraft in the naïve host in the absence of conditioning of the hematopoietic niche. Our results indicate that HoxB8-conditional progenitors engraft in a β1 integrin-dependent manner and transiently generate donor-derived mature neutrophils. Furthermore, we show that neutrophils derived in vivo from transplanted HoxB8-conditional progenitors are mobilized to the periphery and recruited to sites of inflammation in a manner that depends on the C-X-C chemokine receptor 2 and β2 integrins, the same mechanisms that have been described for recruitment of endogenous primary neutrophils. Together, our studies advance the understanding of HoxB8-conditional neutrophil progenitors and describe an innovative tool that, by virtue of its ability to engraft in the naïve host, will facilitate mechanistic in vivo experimentation on neutrophils.

Highlights

As mediators of the acute inflammatory response, neutrophils play essential roles in host defense against bacterial and fungal infection (Ley et al, 2018)
We reported that a HoxB8-conditional progenitor cell line that we derived is able to produce substantial numbers of donor graft-derived neutrophils in mice that were not subjected to any conditioning of the hematopoietic niche (Cohen et al, 2021)
For two of the independentlyestablished progenitor lines, line 2 (P2) and line 3 (P3), we observed very few donor-derived cells present in the recipient mouse bone marrow at 4 days after transplant (Figure 1A). This was in contrast to the robust engraftment of progenitor line 1 (P1), as measured by the fraction of CD45.2+ cells in bone marrow that were derived from transplanted donor progenitors (Figure 1A)

Summary

Introduction

As mediators of the acute inflammatory response, neutrophils play essential roles in host defense against bacterial and fungal infection (Ley et al, 2018). Neutrophil development into their mature effector state primarily occurs in the bone marrow. Neutrophils are abundant and short-lived, a combination that requires the expenditure of a great amount of energy and resources to produce around a billion mature neutrophils per kilogram human body mass per day under homeostasis (Kubes, 2018). While primary neutrophils are obtained from blood or tissue samples, they are nonproliferative and have a short lifespan.

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