摘要Background:Busulfan(BU)is an alkylating agent used as a conditioning agent prior to hematopoietic stem cell(HSC)transplantation as it is known to be cytotoxic to host hematopoietic stem and progenitor cells.The susceptibility of HSCs to BU injury plays an important role in the myeloablative efficacy of BU.Different susceptibilities were demonstrated in genetically diverse(GD)mice in our preliminary research.Methods:Three strains of GD mice with different susceptibilities to BU-induced HSC injury were used for screening biological markers of HSC injury susceptibility in urine.The urine proteins were analyzed using liquid chromatography coupled with tandem mass spectrometry to screen for differentially expressed proteins.Screening for pos-sible biomarkers based on differences in protein expression abundance was validated using enzyme-linked immunoassay(ELISA).Results:Functional analysis showed that the differential proteins were all involved in a series of biological pathways related to cellular senescence,apoptosis,and an-giogenesis;whereas the differential proteins of the high-susceptible strain were enriched for the regulation of bone marrow microenvironment pathways,those of low-susceptible strain were enriched for the proapoptotic effect of GTPase path-ways.Based on protein abundance differences,several urinary proteins that may be indicative of susceptibility were screened,and ELISA validation results showed that angiotensin-converting enzyme may be a potential biomarker predicting HSC suscep-tibility for BU conditioning.Conclusions:This study indicates that urinary protein levels can reflect differences in susceptibility to BU-induced HSC injury.Using GD mice to construct genetic differ-ence models will provide preclinical data for screening BU-related biological markers.