A Study On The Effect Of Post-IR Dietary Restriction On Hematopoietic Reconstitution In Mice

Background/Aims:Cancer has become the foremost cause of mortality,and ionizing radiation(IR)is a primary remedy for malignant tumors.On a clinical level,cancer patients are frequently unable to eat due to tumor ingestion,gastrointestinal toxins and side effects from radiotherapy and chemotherapy,and the incapacity to eat because of gastrointestinal issues.Malnutrition is another risk factor that affects the prognosis of radiotherapy.However,there is a lack of research on the impact of nutritional restrictions on the hematopoietic system damage caused by radiotherapy.The mechanism of nutritional metabolism and stem cell regulation is currently a frontier hot spot,and radiotherapy-related bone marrow suppression is a common problem faced by most radiotherapy patients.This project aims to study the effect and related mechanisms of post-irradiation dietary restriction on hematopoietic reconstruction in mice,providing new ideas for improving radiotherapy-related bone marrow suppression.Methods:2-month-old mice were treated with 30% dietary restriction(DR)for 1 month and compared to female mice of the same age fed AL and to AL mice fed 1 month post-IR." Peripheral blood cell counts were analyzed at different time points(1d,7d,12 d,1m);femurs were taken for histological analysis 1 month after IR;1 month after IR,HSC(hematopoietic stem cells,HSCs)numbers and HSC cell cycle activity,downstream lineages(lymphoid and myeloid)were analyzed by flow cytometry;γ-H2AX(phospho-Histone H2AX)immunostaining and comet assay to quantify DNA damage;real-time fluorescence quantitative PCR to detect classical DNA damage repair genes(Trp53,P21,Bax,Bcl2,Puma,Caspase 3,Caspase 9,ATM,RAD51,53BP1)in hematopoietic stem cells of mice 1 month after IR The relative expression of the classical DNA damage repair genes(Trp53,P21,Bax,Bcl2,Puma,Caspase 3,Caspase 9,ATM,RAD51,53BP1)in hematopoietic stem cells of mice at 1 month post-irradiation.Results:(1)Our study showed that the number of peripheral blood leukocytes and lymphocytes in mice with dietary restriction(DR)for one month after a single total body irradiation with X-rays was difficult to recover,the total number of bone marrow cells was significantly reduced,lymphoid progenitor cells and downstream cells were reduced,and the degree of bone marrow damage was increased.The hematopoietic phenotype was damaged by post-irradiation food restriction.(2)postIR dietary restriction caused increased DNA damage and decreased repair,as evidenced by increased γ-H2 ax focus,increased comet trailing,more active cell cycle and significantly suppressed Rad51 repair gene expression.(3)post-IR dietary restriction caused increased apoptosis of hematopoietic stem cells by significantly activating DNA damage signaling pathways(caspase3,caspase 9,Bax,Puma).(4)Splenic colony formation assay and bone marrow competition transplantation assay suggested that post-IR dietary restriction exacerbated the hematopoietic reconstitution dysfunction of HSC in mice.Conclusion:post-IR dietary restriction(DR)significantly inhibits post-transplant hematopoietic reconstitution in transplant donors after bone marrow transplantation,Damage to the reconstruction of the hematopoietic system.