The change of splenic morphometric parameters in aged laboratory animals exposed to ionizing radiation after undergoing stem cells transplantation

Aim. To study the changes of splenic morphometric parameters in aged laboratory animals exposed to ionizing radiation in the dose of 4Gr after multipotent mesenchymal and hematopoietic stem cells transplantation. Methods. The experiments were conducted on 72 white male laboratory mice at the third year of life with the body weight of 50 g. Multipotent mesenchymal stem cells and hematopoietic stem cells were obtained from 8 laboratory female mice with the body weight of 30 g aged 3-4 months, the gestation term was 14 days. The first group (36 animals exposed to radiation) was subdivided to 2 subgroups of 18 animals each. The suspension of multipotent mesenchymal stem cells (6 000 000 cells/kg) and hematopoietic stem cells (330 000 cells/kg) was introduced as single intravenous injection to the experimental subgroup (18 animals) 1 hour after the animals were exposed to radiation. The animals of control subgroup (18 animals) were injected 0.2 ml of normal saline. The second group included two subgroups 18 mice each that underwent the same procedure without being exposed to radiation. 9 animals from each group were withdrawn from the study at 1st and 7th day each. The lymphoid follicle gross area, area of the T-cell and B-cell zones, general numbers of cells in the red pulp of spleen, including erythrocyte and lymphocyte count, were measured in splenic histologic specimens using the morphometric «BioVision 2008» software. Results. It was shown that on the 7th day after exposure to ionizing radiation followed by stem cells transplantation, the area of thymus-independent zone of lymphoid follicle restored back to normal ranges. The effect of multipotent mesenchymal stem cells and hematopoietic stem cells transplantation also resulted in the increase of the number of cells in the red pulp of spleen. There were no significant changes observed in numbers of erythroid cells and white blood cells in the spleen red pulp compared to control subgroup. At the same time, the leukocyte number in the red pulp of spleen restored to normal values. Conclusion. The restoration of the basic morphometric parameters in spleen of aged laboratory animals exposed to ionizing radiation may be explained be increased homing of splenic colony-forming units with subsequent activation of extramedullary hematopoiesis in spleen, and apoptosis-reducing effect of multipotent mesenchymal stem cells.

ionizing radiation, stem cells, splenic morphometric parameters, ageing