Studies in feline long-term marrow culture: hematopoiesis on normal and
feline leukemia virus infected stromal cells
ML Linenberger and JL Abkowitz
Department of Medicine, University of Washington, Seattle 98195.
To study the effects of feline leukemia virus (FeLV) on the hematopoietic
microenvironment, a two-step feline long-term marrow culture (LTMC) system
was developed and characterized. The adherent, stromal layer of these
cultures is composed of fibroblastoid cells (50% to 80%), macrophages (10%
to 30%), fat cells (10% to 20%), and large, polygonal cells that express
muscle actin (1% to 2%). When fresh, enriched marrow mononuclear cells
(MMNC) were added to 3-week-old irradiated stromal cultures, nonadherent
erythroid progenitors (BFU-E) and granulocyte/macrophage progenitors
(CFU-GM) could be detected for up to 5 and 12 weeks, respectively. LTMC
stromal layers established from marrow cells from cats viremic with either
a nonpathogenic strain of FeLV (FeLV-A/61E) or the anemogenic strain
FeLV-C/Sarma were morphologically equivalent to uninfected LTMC stromal
layers, although more than 80% of the stromal cells expressed FeLV gag
protein. When FeLV-infected stromal cultures were recharged with uninfected
MMNC, altered patterns of hematopoiesis were observed, compared with
recharged, uninfected stromal cultures. In cultures with infected stroma,
fewer nonadherent cells (NAC), nonadherent BFU-E, and nonadherent CFU-GM
were detected during the first 4 to 5 weeks after recharge. In contrast,
greater numbers of NAC and nonadherent CFU-GM were found from weeks 5 to 12
after recharge. When FeLV-infected stromal cultures were recharged with
MMNC from a cat heterozygous for the X-chromosome-linked enzyme
glucose-6-phosphate dehydrogenase (G-6- PD), the percentage of nonadherent
CFU-GM expressing the domestic type G-6-PD isoenzyme remained stable over
time (mean % domestic [%d], 53% +/- 3%), and was equivalent to that of
nonadherent CFU-GM maintained in uninfected cultures (mean %d, 56% +/- 3%),
indicating that clonal drift or clonal selection was not responsible for
the enhanced maintenance of CFU-GM. Furthermore, as only 10% to 20% of
recharged hematopoietic cells became infected with FeLV in vitro, it is
unlikely that the altered pattern was due to progenitor infection. We
hypothesize that the increase in NAC and nonadherent CFU-GM in
FeLV-infected cultures resulted from enhanced growth factor production by
stromal cells. The two-step LTMC system may facilitate the characterization
of stromal- derived factors that affect progenitor cell engraftment and
proliferation.
Volume 80,
Issue 3,
pp. 651-662,
08/01/1992
Copyright © 1992 by The American Society of Hematology
