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P Anklesaria, JS Greenberger, TJ Fitzgerald, B Sullenbarger, M Wicha and A Campbell
Department of Radiation Oncology, University of Massachusetts Medical
School, Worcester.
Mutant Sl/Sld mice exhibit decreased marrow hematopoiesis. The defect is
known to reside in the marrow microenvironment of these animals, which is
reproduced in vitro by primary marrow explants as well as by cloned marrow
stromal cell lines. Bone marrow progenitor cells are incapable of adhering
to primary Sl/Sld stromal cells or cloned stromal cell lines derived from
them to form cobblestone-islands and proliferate. The role of hemonectin, a
marrow-specific adhesion protein in the defective hematopoiesis of the
Sl/Sld mice, was studied. Indirect immunoperoxidase staining of marrow in
situ from Sl/Sld mice showed little specific staining while specific
staining was seen in a pericellular distribution in marrow from +/+ mice.
Hemonectin expression in several cloned stromal cell lines from Sl/Sld mice
was compared by immunoblotting with that in cloned stromal cell lines from
normal +/+ littermates. Cell line Sld3, which has the least hematopoiesis
supportive capacity in vitro, showed no detectable hemonectin by
immunoblotting, while Sld1 and Sld2 showed detectable but greatly reduced
amounts compared with normal +/+ 2.4, GBI/6, and D2XRII. Confluent cultures
incubated with purified hemonectin and engrafted with enriched progenitors
showed a significant increase in the cumulative number of
cobbleston-islands and day 14 spleen colony- forming units (CFU-s) forming
progenitors (39.15 +/- 3.6/dish; 16.3 +/- 3.1/dish, respectively), compared
with untreated Sld3 cultures (cobblestone-islands 8.1 +/- 3.6/dish; CFU-s
forming progenitors 8.8 +/- 0.05/dish). Hemonectin-mediated progenitor cell
binding to the Sld3 stromal cells was specifically inhibited by
antihemonectin but not by preimmune serum. These data support the role of
hemonectin in early progenitor-stromal cell interactions.
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| Copyright © 1991 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||