Functional cloning of IGFBP-3 from human microvascular endothelial cells reveals its novel role in promoting proliferation of primitive CD34+CD38- hematopoietic cells in vitro.
Ex vivo expansion of hematopoietic stem cells (HSCs) has been investigated as a means of enhancing engraftment of transplantation therapies, but current ex vivo expansion methods typically result in a loss of functional stem cell activity. Factors that can selectively expand human HSCs remain elusive. Recently we have isolated three functionally distinct human brain microvascular endothelial cells (HBMVECs) that differ greatly in their ability to support in vitro proliferation of human umbilical cord blood (UBC) CD34+CD38-cells. Using these distinct HBMVEC populations, we have devised a cell-based functional cloning assay to identify a molecule(s) capable of facilitating expansion of HSCs in vitro. A gene encoded for IGFBP-3 (insulin-like growth factor binding protein-3) has been identified. IGFBP-3 mRNA and protein are differentially expressed in distinct HBMVEC populations. In vitro cell proliferation assay and CD34+CD38- immunophenotype analysis showed that the addition of an exogenous IGFBP-3 to cultures of purified CD34+/-CD38-Lin- cells (CD2/CD3/CD14/CD16/CD19/CD24/CD56/CD66b/GlyA depleted) enhanced proliferation of primitive hematopoietic cells with CD34+CD38- phenotype, suggesting that IGFBP-3 is capable of expanding primitive human blood cells. These expanded primitive blood cells were illustrated to maintain ability to generate functional progenitors. IGFBP-3 belongs to a family of high-affinity IGFBPs, which binds to IGFs and modulates their actions. IGFBP-3 appears to have intrinsic bioactivity that is independent of IGF binding. We are currently exploring the underlying mechanism by which IGFBP-3 modulates proliferation of primitive hematopoietic cells, and the potential of IGFBP-3 to expand pluripotent human repopulating cells capable of hematopoietic reconstitution of irradiated NOD/SCID recipients.
ViaCell Inc., Worcester, MA 01605, USA. lliu@viacellinc.com
Li-Qin
LQ
Liu
Margaret
M
Sposato
Hai-Yan
HY
Liu
Tracy
T
Vaudrain
Meng-Jiao
MJ
Shi
Kristin
K
Rider
Zack
Z
Stevens
Jan
J
Visser
Hong-Kui
HK
Deng
Morey
M
Kraus
D036541:ADP-ribosyl Cyclase / Q000032:analysis; D051997:ADP-ribosyl Cyclase 1; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D001921:Brain / Q000098:blood supply; D002450:Cell Communication / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D002999:Clone Cells / Q000378:metabolism; D003001:Cloning, Molecular; D046508:Culture Techniques / Q000379:methods; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005312:Fetal Blood / Q000166:cytology; D016298:Hematopoietic Cell Growth Factors / Q000235:genetics / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins
D015703:Antigens, CD; D018952:Antigens, CD34; D018797:Cell Cycle Proteins; D016298:Hematopoietic Cell Growth Factors; D018972:Insulin-Like Growth Factor Binding Protein 3; D008562:Membrane Glycoproteins; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1