Platelet-derived microparticles stimulate proliferation, survival, adhesion, and chemotaxis of hematopoietic cells.
OBJECTIVE
Peripheral blood platelet-derived microparticles (PMPs) circulate in blood and may interact directly with target cells affecting their various biological functions.


METHODS
To investigate the effect of human PMPs on hematopoiesis, we first phenotyped them for expression of various surface molecules and subsequently studied various biological responses of normal stem/progenitor (CD34(+)) and more differentiated precursor cells as well as several leukemic cell lines to PMPs.


RESULTS
We found that, in addition to platelet-endothelium attachment receptors (CD41, CD61 and CD62), PMPs express G-protein-coupled seven transmembrane-span receptors such as CXCR4 and PAR-1; cytokine receptors including TNF-RI, TNF-RII, and CD95; and ligands such as CD40L and PF-4. Moreover, we found that several of these receptors could be transferred by PMPs to the membranes of normal as well as malignant cells and observed that PMPs: 1) chemoattract these cells, 2) increase their adhesion, proliferation, and survival, and 3) activate in these cells various intracellular signaling cascades including MAPK p42/44, PI-3K-AKT, and STAT proteins. The biological effects of PMPs were only partly reduced by heat inactivation or trypsin digest, indicating that, in addition to the protein components of PMPs, lipid components are also responsible for their biological activity.


CONCLUSIONS
We conclude that PMPs modulate biological functions of hematopoietic cells and postulate that they play an important but as yet not fully understood role in intercellular cross-talk in hematopoiesis. Further studies, however, are needed to identify the PMP components that exert specific biological effects.
Baj-Krzyworzeka
Monika
M
Stem Cell Biology Program, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA.
Majka
Marcin
M
Pratico
Domenico
D
Ratajczak
Janina
J
Vilaire
Gaston
G
Kijowski
Jacek
J
Reca
Ryan
R
Janowska-Wieczorek
Anna
A
Ratajczak
Mariusz Z
MZ
D018952:Antigens, CD34 / Q000032:analysis; D015415:Biomarkers / Q000032:analysis; D001792:Blood Platelets / Q000502:physiology*; D001854:Bone Marrow Cells / Q000166:cytology; D002448:Cell Adhesion / Q000502:physiology*; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival; D022082:Cellular Structures / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology*; D004900:Erythroblasts / Q000166:cytology / Q000502:physiology; D018922:HL-60 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000502:physiology; D006801:Humans; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D014407:Tumor Cells, Cultured
D018952:Antigens, CD34; D015415:Biomarkers; D010750:Phosphoproteins