Plasma osteopontin is correlated with bone resorption markers in rheumatoid arthritis patients.
OBJECTIVE
To assess whether any form of osteopontin (OPN) is correlated with bone resorption markers or treatment effects in rheumatoid arthritis (RA).


METHODS
Subjects comprised 119 patients with RA. RA disease activity was evaluated by Disease Activity Score (DAS) 28, erythrocyte sedimentation rate (ESR), and levels of C-reactive protein (CRP), rheumatoid factor (RF) and matrix metalloproteinase (MMP)-3. OPN levels in plasma and urine were measured by enzyme-linked immunosorbent assay (ELISA). Levels of tartrate-resistant acid phosphatase (TRACP) 5b in serum and C-terminal telopeptide of type 1 collagen (CTX)-1 in urine were measured by ELISA. Patients were divided into responder and nonresponder groups, and OPN levels were compared at baseline and after treatment.


RESULTS
Levels of full-length OPN in plasma (P-fOPN) were significantly correlated with levels of TRACP 5b (r = 0.44, P < 0.001), urine CTX-1 (r = 0.26, P = 0.004) and MMP-3 (r = 0.34, P < 0.001). Levels of TRACP 5b were significantly correlated with age (r = 0.25, P = 0.007), but levels of P-fOPN were not. After treatment, plasma OPN levels were significantly decreased in responders (P = 0.003). Levels of full-length or thrombin-cleaved forms of OPN in urine were not correlated with TRACP 5b or CTX-1.


CONCLUSIONS
Our results suggest that plasma OPN may reflect inflammatory bone destruction in RA patients.
Department of Gastroenterology and Rheumatology, Fukushima Medical University School of Medicine, Fukushima, Japan.
Haruyo
H
Iwadate
Hiroko
H
Kobayashi
Takashi
T
Kanno
Tomoyuki
T
Asano
Rie
R
Saito
Shuzo
S
Sato
Eiji
E
Suzuki
Hiroshi
H
Watanabe
Hiromasa
H
Ohira
D000135:Acid Phosphatase / Q000097:blood; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy / Q000652:urine; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001799:Blood Sedimentation; D001862:Bone Resorption / Q000097:blood* / Q000175:diagnosis / Q000652:urine; D024042:Collagen Type I / Q000652:urine; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000097:blood; D008297:Male; D019278:Matrix Metalloproteinase 3 / Q000097:blood; D008875:Middle Aged; D053495:Osteopontin / Q000097:blood* / Q000652:urine; D010455:Peptides / Q000652:urine; D012720:Severity of Illness Index; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors; D016896:Treatment Outcome
D018501:Antirheumatic Agents; D015415:Biomarkers; D024042:Collagen Type I; D007527:Isoenzymes; D010455:Peptides; C506895:SPP1 protein, human; C052929:collagen type I trimeric cross-linked peptide; D053495:Osteopontin; C000605510:ACP5 protein, human; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3
CTX-1; TRACP 5b; osteopontin; rheumatoid arthritis