Role Of Hemopoietic Blood Stem Cell In The Recovery Of Acute Tubular Necrosis In Mice

BACKGROUND: According to traditional theory of the recovery after acutetubular necrosis, reconstruction of renal tubule is dependent on residual epithelialcells next to the necrosis region. Undergoing the process of dedifferentiation,proliferation and redifferentiation, these cells can reestablish the injured tubule and itsfunction. Along with the study of stem cells, some polypotential stem cells namedadult stem cells have been found in adult tissue, which have the ability ofmulti-lineage differentiation, and this made them very important roles in tissueregeneration and recovery after injury. Adult stem cells are abundant in bone marrow,and some recent researches have found that hemopoietic blood stem cell maydifferentiate into renal tubular epithelial cells and play a role in turnover of acutetubular necrosis, though there is still controversy about this issue.OBJECTIVE: We intend to demonstrate hemopoietic blood stem cell candifferentiate into renal tubular epithelial cells by an animal bone marrowtransplantation model, discuss the role of hemopoietic blood stem cell in the recoveryof acute tubular necrosis, fertilize the theory of turnover in acute renal tubularnecrosis.METHODS: Transgenic C57BL/6 mice labeled with green flouresentprotein(GFP) as bone marrow donors, C57BL/6 mice without fluorescence label,recipients of bone marrow transplantation, were divided into seven groups: (1)Normal group: obtain physiological and renal histological data of normal C57BL/6mice.(2) Ischemia/Reperfusion group: cross clasp left renal pedicle for 30 minutesfollowed by reperfusion, fight renal pedicle left untouched, kidneys obtained on day 3,day 7, day 14 and day 28 after the operation, histological change of both sides wasobserved. (3) Bone Marrow Transplantion group: BMT after irradiation, sacrificed onday 56 and day 84 after transplantation, to observe the differentiation of hemopoieticblood stem cell in the kidneys without injury. (4) BMT+IR group: unilateral IRoperation carried out on day 56 after bone marrow transplantation, to observedifferentiation of donor hemopoietic blood stem cell in bilateral kidneys. Bonemarrow reconstruction after transplantation proved by blood routine and flow cytometry of bone marrow cells; distribution and amount of green fluorescence inkidneys of recipient mice observed by fluorescence histochemistry,immunohistochemistry means.RESULTS: Single lateral ischemia-reperfusion injury result in acute tubularnecrosis, and proximal tubule was the most sensitive to the injury. Significantdifference in pathology of kidney was found between the two sides of theischemia-reperfusion group. Biochemical results showed BUN and SCr in singlelateral ischemia-reperfusion group have no significant change; in our study, recoveryprocess of tubule in ATN models began on day 3 after induction and accomplished onday 28, similar result was seen in acute tubular necrosis models after bone marrowtransplantation.Green fluorescence was seen in renal tubular epithelium on day 56 and 84 afterbone marrow transplantation, further prove of these cells locating in tubularepithelium was obtained by laser scanning confocal microscope, fluorescencehistochemistry show these cells expressed renal tubular epithelium specific proteinmegalin, suggesting donor hemopoietic blood stem cell had differentiated intofounctional renal tubular epithelial cells. These results suggest that hemopoietic bloodstem cell can participate in regeneration of renal tubular epithium when the tubule notinjuried.In the ischemia-reperfusion model, number of the marrow derived renalepithelial cells on the ischemic side was more than that of contralateral, suggesting thelevel of hemopoietic blood stem cell differentiation into renal tubular epithelial cellsis associated with the degree of renal tubular injury.CONCLUSION: Ischemia-reperfusion injury can induce acute tubularnecrosis; hemopoietic blood stem cell can differentiate into renal tubular epitheliarcells and participate in regeneration of renal epithelium. Acut tubular necrosis can'mobil' hemopoietic blood stem cell in the process of injury turnover, number ofepitheliar cells derived from bone marrow is associated with the degree of injury.