HSC Trans-differentiates Primarily To Lung Tissue Cells For Radiation-induced Damage Repair

ObjectiveTo determine whether hematopoietic stem cells(HSC)are able to trans-differentiate primarily to lung tissue cells for radiation-induced damage repair.Methods(1)Observation of histological repair in radiation-induced lung damage via HSC transplantation:HSCs of C57 mice were transplanted into CD45.1 mice irradiated with 60Co γ-ray lethal dose of 9 Gy.Eight weeks after transplantation,the control non-irradiated group,the irradiated group(7 days after irradiation),and the irradiated-transplantation group were sacrificed.The pathological changes of lung in each group were observed using HE staining.(2)Detection of the mitigation of radiation-induced lung inflammatory response via HSC transplantation:HSCs of C57 mice were transplanted into CD45.I mice irradiated with 60Co γ-ray lethal dose of 9 Gy.Eight weeks after transplantation,the control non-irradiated control group,the irradiated control group(7 days after irradiation),and the irradiated-transplantation group were dissected for their lung tissue.The relative expression levels of inflammatory factors IL-1β,IL-6,TNF-α,IL-10,IL-13 in lung tissues of each group were quantified using Q-PCR.(3)Quantification of donor-derived cells in recipients’ lungs using flow cytometry:HSCs of male RosamT/mG mice were transplanted into female CD45.1 mice irradiated with 60Co γ-ray lethal dose of 9 Gy.The mice were dissected for their organs,including heart,liver,lung,kidney and intestine.Flow cytometry identification of donor-derived cells(tomato-red-fluorescent-expressing cells)in recipients’lungs was performed,excluding pseudo positive cell types(circulated hematopoietic cells,pulmonary macrophages and megakaryocytes).(4)Detection of Ddx3y specific gene of donor-derived Y chromosome in recipients’ lung cells using PCR:HSCs of male RosamT/mG mice were transplanted into female CD45.1 mice irradiated with 60Co γ-ray lethal dose of 9 Gy.PCR was used to confirm the existence of Ddx3y in recipients’ lung sixteen weeks post transplantation.(5)Identification of co-expression between donor marker(tomato-red fluorescent)and lung specific markers using confocal and imaging flow cytometry:HSCs of male RosamT/mG mice were transplanted into female CD45.1 mice irradiated with 60Co γ-ray lethal dose of 9 Gy.Sixteen weeks post transplantation,confocal and imaging flow cytometry were utilized to analyze the co-expression between donor marker(tomato-red fluorescent)and lung epithelial cell markers(including Pan-keratin,T1-α,SP-C).Results(1)HSC transplantation can rescue lethally irradiated mice with an overall of 90 percent survival rate,and the transplanted mice can then survive for a long period.Pathological report showed signs of radiation-induced pulmonary inflammation,including alveolar space narrowing,alveolar septum hyperplasia,inflammatory cell infiltration,bronchial structure damage,bleeding,etc.HSC transplantation can alleviate radiation-induced inflammatory response in lungs.Most part of the lung recovered to normal,with no bleeding and no inflammatory cell infiltration.(2)HSC transplantation can relieve the inflammatory response in lungs of mice exposed to lethal doses of y-ray.Levels of inflammatory factors IL-1β,IL-6,TNF-α,IL-10,IL-13 was significantly lower after HSC transplantation.The inflammation achieved remission.(3)Four months after transplanting HSCs of RosamT/mG mice into lethally-irradiated CD45.1 mice,excluding pseudo positive cell types(hematopoietic cells,pulmonary macrophages and megakaryocytes),the ratio of tomato-red fluorescent was highest in recipients’lungs amongst all organs tested.(4)Lung epithelial cells,endothelial cells and mesenchymal cells were detected with the existence of Y chromosome after HSC transplantation.(5)Co-expression was detected between donor-derived tomato-red fluorescent and lung epithelial cell markers(Pan-keratin,T1-α,SP-C)using confocal and imaging flow cytometry.Conclusion(1)Transplanted hematopoietic stem cells promotes the repair of radiation-induced lung injury via trans-differentiation.