EFFECT OF 14-DAY UNLOADING AND RE-ADAPTATION ON HEMATOPOIETIC PRECURSORS FROM THE DISTAL AND PROXIMAL PARTS OF RAT’S HINDLIMBS

After space mission, blood composition of cosmonauts is noted to change. One of the reasons is the impairment of the bone marrow (BM) hematopoiesis. We have studied of the effects of rat hindlimb unloading and readaptation on BM hematopoietic cells. Samples of rats’ femoral and tibial BM were used for analysis of hematopoietic colony-forming units (CFUs) following 14-d hindlimb unloading (HLU) and subsequent 14-d recovery of the reloading (HLU+R). HLU reduced the CFUs total count in tibial BM only, primarily in consequence of a decreased number of colonies of the common granulocytes and monocytes progenitor (CFU-GM). As for the hematopoietic precursors from femoral BM, there was a considerable reduction in monocyte (CFU-M) and erythroid (CFU-E) colonies. In tibial BM, there was a considerable reduction in bipotent granular-monocytes cells (CFU-GM) only. In femoral BM, all CFUs colonies returned to the basal level during the period of readaptation. In tibial BM, a significant activation of the growth of bipotent CFU-GM and unipotent (CFU-G and CFU-M) precursors was observed. Therefore, the progenitor hematopoietic cells in various parts of rat’s limbs demonstrated different reactions to unloading and patterns of CFUs colonies restoration during readaptation. This can be a reason for the shift in the hematopoietic precursor profile and committed progeny due to exposure to the spaceflight factors.