Reticulocyte rigidity and passage through endothelial-like pores
RE Waugh
Department of Biophysics, University of Rochester, School of Medicine and
Dentistry, NY 14642.
The importance of cell rigidity in regulating the release of reticulocytes
from the bone marrow has been investigated in a model system. Reticulocytes
were obtained from phlebotomized rabbits and separated from whole blood by
discontinuous density gradient centrifugation. The mechanical properties of
the cells were tested. Using single-cell micromechanical techniques, the
membrane elastic rigidity and the viscoelastic response of reticulocyte and
mature cell populations were measured. The reticulocyte membranes were more
rigid than the mature membranes, but the reticulocyte properties were
heterogeneous, and some cells exhibited behavior indistinguishable from the
mature cells. The mean time constant for viscoelastic recovery was the same
for reticulocytes as for mature cells, but the variability within the
reticulocyte population was greater. The possible influence of this
increased rigidity on cell egress from the bone marrow was tested using an
in vitro model of the thin endothelial pores found within the marrow. A
silicon wafer approximately 0.1 microns in thickness and containing a small
(1.2-microns diameter) pore in its center was cemented over the tip of a
large (15.0-microns ID) micropipette. The passage of cells through the pore
was observed as a function of the pressure across the pore. Consistent with
the difference in mechanical properties, the reticulocytes required greater
pressures (as great as 4.0 mm Hg compared with less than 1.0 mm Hg) and
took longer to traverse the pore. These measurements support the postulate
that deformability is important in the regulation of the release of cells
from bone marrow.
Volume 78,
Issue 11,
pp. 3037-3042,
12/01/1991
Copyright © 1991 by The American Society of Hematology
