Hm. Goselink et al., COLONY GROWTH OF HUMAN HEMATOPOIETIC PROGENITOR CELLS IN THE ABSENCE OF SERUM IS SUPPORTED BY A PROTEINASE-INHIBITOR IDENTIFIED AS ANTILEUKOPROTEINASE, The Journal of experimental medicine, 184(4), 1996, pp. 1305-1312
Serum contains many growth factors and nutrients that stimulate colony
formation of hematopoietic progenitor cells (HPC) in semisolid cultur
es. In the absence of serum, no proliferation of HPCs could be obtaine
d in semisolid medium cultures of partially purified bone marrow cells
in the presence of multiple hematopoietic growth factors, insulin, ch
olesterol, and purified clinical-grade human albumin, This appeared to
be due to a suppressive activity induced by monocyte- and T lymphocyt
e-depleted accessory cells on CD34(+) HPCs. Serum-free conditioned med
ium from the bladder carcinoma cellline 5637 could replace serum to su
pport the growth of HPCs in these cultures, After gel filtration and r
everse-phase high-performance liquid chromatography of 5637 supernatan
ts, this activity could be attributed to a 15-kD protein that was furt
her identified by NH2-terminal sequence analysis as the serine protein
ase inhibitor antileukoproteinase (ALP). The growth-supportive activit
y from the 5637 conditioned medium and the (partially) purified fracti
ons could be completely neutralized by a polyclonal rabbit IgG antibod
y against human ALP (huALP). Similar supportive effects on the growth
of HPC could be obtained in the presence of recombinant huALP, We demo
nstrated that the COOH-terminal domain of ALP containing the proteinas
e inhibitory activity was responsible for this effect. alpha-1 protein
ase inhibitor was capable of similar support of in vitro HPC growth. T
hese results illustrate that proteinase inhibitors play an important r
ole in the in vitro growth of hematopoietic cells by the neutralizatio
n of proteinases produced by bone marrow accessory cells. This may be
of particular relevance for in vitro expansion of human hematopoietic
stem cells in serum-free media.