The effect of transplantation of bone marrow cells induced by the contact with thymus-derived multipotent stromal cells on the immune system of mice, regenerating after cyclophosphamide treatment

Abstract

The effect of transplantation of syngeneic bone marrow cells (BMCs) after their contact in vitro with thymus-derived multipotent stromal cells (MSCs) for regeneration of damaged by cyclophosphamide immune system of mice was studied.Materials and methods. MSCs were obtained from C57BL/6 mice’s thymus by explants method. BMCs were obtained by flushing the femurs. BMCs were induced for 2 hours on the monolayer of thymus-derived MSCs. The immune deficiency of mice was modelled using cyclophosphamide injection. After that, cell transplantation was performed and the state of the immune system was assessed. The number of erythrocytes, hematocrit, hemoglobin concentration in the peripheral blood; the phases of the cell cycle and apoptosis of mesenteric lymph node cells were determined. The amount of antibody-producing cells in the spleen and the delayed hypersensitivity response was determined. The study of proliferative and cytotoxic activity of natural killer lymphocytes, the analysis of phagocytosis, spontaneous and induced bactericidal activity of peritoneal macrophages were performed.Results. It was shown that unlike intact bone marrow cells, BMCs induced by thymus-derived MSCs provided increased spontaneous proliferative activity of lymphocytes with a decrease in the number of lymph node cells in G0/G1 phase by 6.2 % and an increase the number of lymphocytes in S+G2/M phase by 28 % in comparison with the group of mice treated with cyclophosphamide, as well as the recovery of cellularity of the bone marrow, lymph nodes and spleen. At the same time in the lymph nodes, the number of cells in the apoptosis increased. BMCs induced by MSCs showed a pronounced negative effect on natural cytotoxicity, reducing its rates by 3 times compared with the group of cyclophosphamide-treated mice, and on adaptive immunity: the rates of delayed hypersensitivity response decreased by 1.7 times, number of antibody-producing cells by 1.8 times. Red blood cell regeneration was stimulated by intact BMCs, which was manifested by the normalization of hematocrit and hemoglobin and an increase in the number of reticulocytes in the blood by 2.2 times compared with the group of mice treated with cyclophosphamide.Conclusion. Transplanted BMCs improve erythropoiesis in mice after cyclophosphamide treatment, and BMCs, previously induced by thymus-derived MSCs, lose this ability. BMCs after co-culture are strongly activated to impact on the immune system, which is most likely due to the effect of contact interaction with thymus-derived MSCs, which is known, effectively affect hematopoietic cells and possess immunomodulatory properties.