Membrane instability in late-stage erythropoiesis

During maturation of the red blood cell (RBC) from the nucleated normoblast stage to the mature biconcave discocyte, both the structure and mechanical properties of the cell undergo radical changes. The development of the mec hanical stability of the membrane reflects underlying changes in the organi zation of membrane-associated cytoskeletal proteins, and so provides an ass essment of the time course of the development of membrane structural organi zation. Membrane stability in maturing erythrocytes was assessed by measuri ng forces required to form thin, tubular, lipid strands (tethers) from the surfaces of mononuclear cells obtained from fresh human marrow samples, mar row reticulocytes, circulating reticulocytes, and mature erythrocytes. Cell s were biotinylated and manipulated with a micropipette to form an adhesive contact with a glass microcantilever, which gave a measure of the tetherin g force. The cell was withdrawn at controlled velocity and aspiration press ure to form a tether from the cell surface, The mean force required to form tethers from marrow reticulocytes and normoblasts was 27 +/- 9 pN, compare d to 54 +/- 14 pN for mature cells, The energy of dissociation of the bilay er from the underlying skeleton increases 4-fold between the marrow reticul ocyte stage and the mature cell, demonstrating that the mechanical stabilit y of the membrane is not completely established until the very last stages of RBC maturation. (Blood, 2001;97:1869-1875) (C) 2001 by The American Soci ety of Hematology.