The Role Of Nitric Oxide On The Proliferation Of Human Osteoblasts (Hos Cells) Stimulated With Hydroxyapatite
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Date
2006-04
Authors
SUGIATNO, ERWAN
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Abstract
Hydroxyapatite (HA) as a ceramic material is widely used for orthopaedic and
dental implants, since this biomaterial has ability to stimulate osteoblast functions in
vitro and in vivo. However, the exact mechanism by which HA accelerates osteoblast
function, thereby stimulating rapid bone formation, remains far from clear. It is well
known that bone formation is tightly regulated by nitric oxide (NO) via its effects on
osteoblast and osteoclast function. Therefore, the overall aim of the present studies was
to elucidate the possible regulation of NO in HA-stimulated HOS cell proliferation. The
present study used a human osteoblast cell line (HOS cells), since this cell line is known
to mimic the functions of normal human osteoblasts, thereby representing the biological
response of normal osteoblasts in humans.
The first experiments were carried out to delineate whether HA-stimulated HOS
cell proliferation is regulated by endogenous NO. The results showed that following
contact with HA, elevated NO production and HOS cell proliferation were observed.
Exogenous L-arginine further promoted HA-stimulated osteoblast NO production and
proliferation. Furthermore, cell proliferation and NO production by HA-stimulated HOS
cells in the presence of anti-human integrin a V antibody were reduced. Similarly
reduction of cell proliferation and NO production by HA-stimulated HOS cells was
observed when the cells were incubated with eNOS, but not nNOSand iNOS, inhibitor.
Deletion of NO production by a NO scavenger resulted in suppressed HA-stimulated
osteoblast proliferation.
The effect of exogenous NO on HA-stimulated HOS cell proliferation was then
determined. The results showed that exogenous NO up to 20 )lM enhances HAxv
sumUlatea tlu:s cell prOllteration. lhe ettect ot exogenous NU on HA-stimulated HUS
cell proliferation was abolished by the presence of NO scavenger but only partially
reduced by eNOS inhibitor. The effect of exogenous NO on HA-stimulated HOS cells
proliferation was also reduced when the cells were pre-treated with anti-human integrin
aVantibody.
The next experiments were to determine whether the regulation of NO on HAstimulated
HOS cell proliferation was via its ability to enhance prostaglandin E2 (PGE2)
production. The results showed that the production of PGE2 by HA-stimulated HOS
cells was augmented by exogenous NO. The presence of NO scavenger suppressed the
production of PGE2 by HA-stimulated HOS cells with or without the presence of
exogenous NO. The presence of eNOS inhibitor only partially suppressed the
production of PGE2 by HA-stimulated HOS cells with or without the presence of
exogenous NO. Again, the production of this prostaglandin by HA-stimulated HOS
cells with or without the presence of NO was reduced when the HOS cells were pretreated
with anti-human integrin aV antibody. The production of this prostaglandin and
cell proliferation by HA-stimulated HOS cells with or without the presence of NO was
reduced when the HOS cells were pre-treated with indomethacin (a COX-l and COX-2
inhibitor) or nimesulide (a COX-2 inhibitor) but not aspirin (a COX-l inhibitor),
suggesting COX2-mediated PGE2 synthesis. HA-stimulated cell proliferation with or
without the presence of NO was also decreased, when HOS cells were pre-coated with
anti-human EP4 receptor antibody.
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Keywords
The Role Of Nitric Oxide On The Proliferation Of Human Osteoblasts , Stimulated With Hydroxyapatite