P. Rameshwar et al., IMPLICATION OF CD44 IN ADHESION-MEDIATED OVERPRODUCTION OF TGF-BETA AND IL-1 IN MONOCYTES FROM PATIENTS WITH BONE-MARROW FIBROSIS, British Journal of Haematology, 93(1), 1996, pp. 22-29
Myelofibrosis (MF) is characterized by bone marrow (BM) fibrosis and e
xcessive deposits of extracellular matrix (ECM) proteins which include
fibronectin (FN), collagen type I and hyaluronic acid (HA), We have p
reviously reported that adhesion to polystyrene over-activates MF mono
cytes. We now confirm their activation by increased CD25 expression an
d tyrosine phosphorylation, We hypothesize that ECM protein-adhesion m
olecule interactions induce overproduction of fibrogenic cytokines in
MF monocytes leading to BM fibrosis. In this study we found that FN, c
ollagen type I and HA induce 2-3-fold more TGF-beta and 6-9-fold more
interleukin (IL)-1 in MF monocytes than normal controls (NC). Since CD
44 can function as the natural ligand for these proteins, its role was
studied. We found that CD44 mediated most of the TGF-beta and IL-1 pr
oduced, Immunoprecipitation of CD44 revealed three proteins at approxi
mately 110 kD in MF monocytes and one in NC. Our results indicate that
adhesion is important in overproduction of TGF-beta and IL-1, and tha
t their production is at least partly mediated by adhesion molecule-EC
M protein interactions, These results implicate at least one adhesion
molecule, CD44, in the pathophysiology of BM fibrosis.