Placenta-derived Mesenchymal Stromal-like Cells Promote Neutrophil Maturation and Macrophage Differentiation into M2 Like Phenotype

Placenta-derived stromal cells, PLX-R18, reduce lethality caused by Hematopoietic Sub-syndrome of Acute Radiation Syndrome (HS-ARS), by promoting rescue of hematopoietic lineage cellularity via secretion of pro-hematopoiesis proteins. PLX-R18 secretions promote bone marrow migration in vitro, and recent studies demonstrate specific migration of the neutrophil and monocyte populations. Therefore, in vitro studies were performed to assess the effect PLX-R18 secretions have on the neutrophil and monocyte/macrophage lineages.

Using flow cytometry and ELISA, we show that PLX-R18 conditioned medium (PLX–R18 CM) induces maturation of bone marrow neutrophils. In addition, PLX–R18 CM shifts differentiation of macrophages to an anti-inflammatory M2 phenotype.

Together, the findings demonstrate the ability of PLX-R18 secretions to alter the myeloid lineage, enabling early maturation and phenotypic shifts in hematopoietic cells. These findings shed light on PLX-R18’s mechanism of action and on its restoration of the adaptive immune system cellularity and function after irradiation damage.