Hypoxia Inducible Factor 1α-driven steroidogenesis impacts systemic hematopoiesis
Glucocorticoids regulate hematopoiesis, but how chronic elevation of endogenous glucocorticoid production affects hematopoietic stem cell (HSC) function and immune cell development remains incompletely understood. Using an adrenocortical cell-specific HIF1 (Hypoxia inducible Factor-1)-deficient mouse model (P2H1Ad.Cortex) resulting in elevated glucocorticoid (GC) levels, we here demonstrate that sustained GC exposure promotes hematopoietic stem and progenitor cell (HSPC) expansion while shifting HSCs toward a more quiescent and metabolically restrained state. Functionally, these HSCs exhibited enhanced regenerative potential, as evidenced by superior donor chimerism in transplantation assays. In addition, we observed a striking increase in myeloid progenitors, as well as in their progeny (monocytes and granulocytes). Conversely, B-cell differentiation in the bone marrow was severely impaired, with a strong block at the pre-pro-B cell stage. To determine whether these phenotypes were driven by glucocorticoid receptor (GR) signaling, we performed transplantation experiments using GR-deficient or WT control bone marrow into P2H1Ad.Cortex or WT littermate recipients. This approach decisively demonstrated that both the increase in myeloid cells and the block in B-cell differentiation were GR-dependent, confirming that GC-GR signaling plays a pivotal role in shaping hematopoiesis. Taken together, our findings clearly suggest a direct role for chronic glucocorticoid exposure in regulating HSC function, lineage differentiation, and stress hematopoiesis. The mouse model of adrenocortical cell-specific HIF1 deficiency provides a valuable tool to study the long-term effects of elevated glucocorticoid levels on hematopoietic regulation and may provide further insight into hematologic disorders associated with chronic therapeutic glucocorticoid administration. Article Summary- Our study aimed to elucidate how chronic elevation of glucocorticoids impacts hematopoietic stem cell function and immune cell development using an adrenocortical cell-specific HIF1-deficient mouse model. - The main conclusion is that sustained glucocorticoid exposure, through glucocorticoid receptor signaling, promotes hematopoietic stem and progenitor cell expansion with enhanced regenerative potential while skewing lineage differentiation toward myeloid expansion and impeding B-cell development.