Expression of the novel metalloproteinase inhibitor RECK
(reversion inducing cysteine-rich protein with Kazal
motifs) in inflamed membranes of rheumatoid arthritis
patients: cytoplasmatic but not membrane bound
expression
of RECK in synovial macrophages
Peter van Lent 1*, Paul Span 2, Annet Sloetjes 3, Tim Radstake 4, ATW van Lieshout 1, JJTM Heuvel 5, Fred Sweep 2 and Wim van den Berg 4
1 Dep of Rheumatology, Nijmegen, The Netherlands
2 Dep of Chemical Endocrinology, Nijmegen, The Netherlands
3 Dep of Rheumatology,Nijmegen,The Netherlands
4 Dep of Rheumatology, Nijmegen,The Netherlands
5 Dep of Chemical Endrocrinology,Nijmegen,The Netherlands
* To whom correspondence should be addressed. E-mail: p.vanlent{at}reuma.umcn.nl.
Accepted 1 September 2004
 | Abstract |
|---|
Objective: To assess the expression and
localization of the novel metalloproteinase inhibitor
RECK (reversion inducing cysteine-rich protein with
kazal motifs), a crucial inhibitor of the membrane bound
MMP-14 secretion and activity, in the synovial membrane
of patients with Rheumatoid Arthritis (RA).
Methods: Quantitative real time reverse
transcription-polymerase chain reaction (Q-PCR) was
performed to study the expression of RECK in synovium
samples from RA, Osteoarthritis (OA) and "trauma"
patients. RECK mRNA levels were compared with those of
the enzyme MMP-14. Goat-anti-human RECK monoclonal
antibody was used to reveal RECK expression on cryostat
sections of synovium. Western blots were performed to
measure protein expression of RECK. RECK expression on
macrophages was investigated by double staining of CD68
and RECK on cryostat sections and characterized by
confocal microscopy. RECK expression on RA monocytes or
normal monocytes was further investigated using FACS
analysis.
Results: Q-PCR of RECK revealed expression levels
in synovial membrane samples of RA patients that were
significantly lower when compared to OA and controls.
MMP-14 mRNA levels were not significantly different
between the three groups. In RA synovium, RECK protein
was mainly expressed in the lining layer but also by
macrophages lying around blood vessels. Fibroblasts and
approximately 50% of the CD68 positive macrophages
clearly expressed RECK. Interestingly in the CD68
positive macrophages, RECK was only expressed in
secretory granules and not on the membrane. The same
pattern was found in M-CSF cultured macrophages of RA
patients and controls. In contrast, synovial fibroblasts
showed a diffuse membrane expression within the synovium
similar to cultured RA fibroblasts. RECK expression was
low on the membrane of monocytes according to FACS
analysis.
Conclusion: The novel MMP inhibitor RECK is
expressed in synovial membranes of RA. In contrast to
fibroblasts, macrophages in the synovium express RECK
only cytoplasmatic and not on their membrane.
Keywords:
MMP inhibitors, MMP-14, RECK, rheumatoid arthritis, synovial membrane
