Glucocorticoids inhibit human hematopoietic stem cell differentiation toward a common ILC precursor

Background: Innate lymphoid cells (ILCs) comprise cytotoxic NK cells and “helper” ILCs (hILCs). Human hILC development is less characterized as compared to NK cells, although all ILCs are developmentally related. It has been reported that the immunosuppressive drugs glucocorticoids (GCs) regulate ILCs function, but whether they control ILCs differentiation from hematopoietic stem cells (HSCs) is unknown. Objective: We sought to analyze the effect of GCs on ILC development from HSCs. Methods: We exploited an in vitro system to generate and expand from peripheral blood (PB) HSCs a multipotent CD56+ ILC precursor able to differentiate into NK cells, ILC1s and ILC3s. We also analyzed ex vivo, at different time points, the PB of allogeneic HSC transplantation (HSCT) recipients who were or were not treated with GCs and compared ILC subset reconstitution. Results: We show that, in vitro, GCs favor the generation of NK cells from myeloid precursors, while they strongly impair lymphoid development. In support to these data, HSCT recipients who had been treated with GCs display a lower number of circulating hILCs, including the ILCP previously identified as a systemic substrate for tissue ILC differentiation. Conclusions: GCs impair the development of the CD117+ ILCP from CD34+ HSCs, while they do not affect the further steps of ILCP differentiation towards NK cells and hILC subsets. This reflects an association of GC treatment with a marked reduction of circulating hILCs in the recipients of HSCT. CD34+ HSC isolated from mobilized HDs' peripheral blood apheresis were cultured for 10 days with SCF, FLT3L, IL15 and IL7 in the presence or absence of Dexamethasone, then RNA was extracted for RNA-seq. Three biological replicates were generated for each condition (Dex and ctrl).