Bletilla Striata Polysaccharide Alleviates Neutropenia by Promoting C/EBPε-Dependent Hematopoietic Reconstitution.

Neutropenia is a common complication in oncology patients receiving chemotherapy, and rapid regeneration of functional neutrophils is critical for effective management. Bletilla striata polysaccharide (BSP) has shown therapeutic potential, but its mechanisms and molecular targets remain unclear. Here, we demonstrate that BSP accelerates the recovery of white blood cells, particularly neutrophils, in a chemotherapy-induced neutropenia (CIN) mouse model with cyclophosphamide (CY). The regenerated neutrophils retained phagocytic activity against bacteria, and BSP treatment significantly reduced mortality in the endotoxin-induced mouse death model. Furthermore, BSP enhanced the repopulation of hematopoietic stem and progenitor cells (HSPCs) in the bone marrow and promoted cell-cycle entry, resulting in increased frequencies of long-term hematopoietic stem cells (LT-HSCs), multipotent progenitors 2 (MPP2), and MPP3/4 subsets. Both in vitro colony formation and in vivo competitive transplantation assays confirmed that BSP reshapes hematopoietic reconstitution and corrects aberrant myeloid differentiation. PCR array analysis of HSPCs indicated that this process is mediated by C/EBPε and its downstream genes (LTF, LCN2, and ELANE). Consistently, BSP failed to support myeloid reconstitution following C/EBPε knockdown in vitro. In a C/EBPε knockout mouse model, HSPCs repopulation and regeneration were impaired, and BSP failed to promote neutrophil recovery after CY challenge or the mobilization of MPP2 and MPP3/4 subsets. The regulatory effects of BSP on C/EBPε target genes were also abolished. In conclusion, our findings identify C/EBPε as a key mediator of BSP activity, driving HSPCs repopulation and restoring hematopoietic function. These results highlight BSP as a potential therapeutic strategy for chemotherapy-induced neutropenia.