Treatment of late radiation-induced cytopenia with hematopoietic stem cells

Hematopoiesis is one of the most radiosensitive system of the human organism. The intensity of effects induced by chronic radiation exposure depends on dose and dose rate. Completeness and duration of hematopoiesis recovery are determined by the intensity of changes occurring during the maximal radiation exposure and on individual radiosensitivity. Long-term (months, years) irradiation even during low dose rate exposure may lead to decrease of compensation and adjustment mechanisms and failure of adaptation. Exhaustion of abilities to adaptation and cumulation of radiation injuries in tissue cells comes when processes of alteration prevail in conditions of chronic radiation exposure. This effect is supposed to be a consequence of reduction of reparatory DNA synthesis during long-term exposure and exhaustion of antioxydative potential of the cell. Physiological loss of mature cells takes place in normal circumstances of organism functioning. This process could be compensated insufficiently under chronic radiation exposure as a result of reduction of highly radiosensitive stem and progenitor cells potential. Thus, in late period after the onset of chronic irradiation disturbance of organ (tissue) functioning can occur. Not organic changes (i.e. RBM hypoplasia, vascular insufficiency) lay in the basis of these processes but limited capacities of physiological regeneration of tissues as in consequence of stem cell pool exhaustion. Currently, the use of hematopoietic stem cells for treatment of the above-mentioned pathologic conditions is very perspective. Clinical trials approbation of the methods for hematopoietic stem cell therapy of hematologic disorders in chronically exposed population of Techa riverside villages is conducted at the URCRM. (author)