THE POTENTIAL RESIDUAL DAMAGE OF HEMOPOIETIC STEM CELLS AFTER LARGE DOSE ~(60)Co IRRADIATION
Shen Ming-yan and Chu Jen-pao (Institute of Radiation Medicine,Academy of Military Medical Sciences,Beijing)
In this paper,we further study the pro-perties of hemopoietic stem cells (HSC) in mice after exposure to 8.5 Gy γ-ray irradia-tion.Firstly,we used serial transplantation technique to determine the self-renewal capa-city of HSC.Secondly,we harvested bone marrow cells (BMC) from the mice completely recovered from lethal irradiation 4 months after exposure and transplanted such BMC to the lethally irradiated syngeneic recipients.The ability of hemopoietic reconstitution of such cells was carefully observed. The results of experiments showed that the self-renewal capacity of HSC is greatly reduced after large dose of γ-irradiation.The therapeutic effect of transplantation of BMC collected from heavily irradiated mice was much lower than that of the control group.The rate of regeneration of hemopoietic stem cells was 1/17 of that resulted from trans-plantation of normal BMC.The karyotype ana-lysis showed that such HSC have partially lost their ability to form permanent radiation chimeras in the recipients.All these facts may reflect the possibility that the capacity of hemopoietic reconstitution of irradiated BMC is to a great extent hampered. From the results of experiments it seems quite certain that different degrees of potential residual damage have become marked in the irradiated murine HSC.The underlying me-chanism of such changes is unknown,but it may be related to proliferative failure of stem cell and genetic housekeeping hypothesis.