Wo. Waegell et al., GROWTH ACCELERATION AND STEM-CELL EXPANSION IN DEXTER-TYPE CULTURES BY NEUTRALIZATION OF TGF-BETA, Experimental hematology, 22(11), 1994, pp. 1051-1057
Hematopoietic lineage-restricted stem cell growth has been shown to be
significantly inhibited by the addition of exogenous transforming gro
wth factor-beta (TGF-beta) to Dexter-type long-term murine bone-marrow
cultures. In order to examine whether TGF-beta produced by these cell
s has a role in hematopoietic growth regulation, Dexter cultures have
been treated with either 1D11.16, a monoclonal antibody that neutraliz
es the biological activity of TGF-beta types 1, 2, and 3, or with a co
ntrol antibody. The composition and cellularity of the nonadherent cel
l populations in these cultures were assessed weekly. Treatment with a
nti-TGF-beta antibody resulted in a five- to 20-fold increase in nonad
herent cells in the cultures when compared to either the control or un
treated cultures by week 4. The majority of these cells were granulocy
te/macrophage-lineage cells as assessed by histologic and flow-cytomet
ric analysis. There was also a significant increase of megakaryocytes
in cultures treated with anti-TGF-beta antibody. Stem-cell analysis, u
sing a colony-forming unit-spleen (CFU-S) assay that combined both the
adherent and nonadherent populations from either 4- or B-week culture
s, showed that there are an equivalent number of hematopoietic stem ce
lls per 10(6) cells regardless of antibody treatment. Therefore, cultu
res treated with anti-TGF-beta antibody contained at least three times
as many stem cells as the control cultures. Finally, kinetics studies
show that the presence of anti-TGF-beta antibody is required from the
onset of culture to produce these effects. These results suggest that
TGF-beta is involved in normal growth regulation of bone-marrow hemat
opoietic cells. By addition of a neutralizing antibody, the normal TGF
-beta negative growth signal is disrupted, allowing for expanded growt
h of several cell populations.