Proliferation activity and number of stromal (CFU-f) and haemopoietic (CFUs) stem cells in bone marrow and spleen of rats of different ages

The number and proliferation activity of stromal (CFU-f) and haemopoietic ( CFUs) stem cells of the femoral bone marrow and the spleen of Wistar rats o f different ages were investigated. CFUs were assayed by the spleen colony technique in irradiated recipient rats. For the determination of numbers of CFU-f an in vitro liquid culture was used. Proliferation activities of bot h types of cells were evaluated in vivo after intraperitoneal administratio n of hydroxyurea. The numbers of both CFU-f and CFUs increased in the femor al bone marrow cavity while they decreased in the spleen within the period from one to five months of the rat age. The total number of nucleated cells per marrow cavity of the femur was higher in the aged rats than in the you ng ones, in the spleen only slight differences were observed with advancing age of rats. It may be thus concluded that the compartment size of CFU-f a nd CFUs increases in the bone marrow and decreases in the spleen during the aging. Proliferation activities of both CFU-f CFUs decreased substantially with time when the populations of both cells reached the size which is mai ntained in adult haemopoietic organs. After sublethal gamma irradiation the recovery of CFU-f has preceded the recovery of CFUs in both the bone marro w and the spleen. The relationship between the stromal stem cells (CFU-f) p roliferation and the state of haemopoiesis is discussed.