Increased osteopontin in muscle and serum from patients with idiopathic inflammatory myopathies.
OBJECTIVE
Osteopontin (OPN) is a non-traditional pro-inflammatory cytokine and is involved in muscle regeneration and inflammation. The aim of this study was to investigate the expression of OPN in skeletal muscle and serum of patients with IIMs.


METHODS
45 patients with IIMs (27 with PM and 18 with DM) were included in the study. Patients received initial prednisone therapy (1-1.5 mg/kg/day) without other immunosuppressive agents. Muscle biopsies were taken before start of treatment and serum samples were collected from each patient before and after corticosteroid treatment. The expression of OPN in skeletal muscle was using immunofluorescence staining and western blotting. Serum OPN levels were detected by enzyme-linked immunosorbent assays (ELISA).


RESULTS
OPN expression was increased in muscle samples from IIM patients compared to control muscle. The serum level of OPN was significantly higher in IIM patients than in controls. Moreover, the serum concentrations in the DM subgroup were significantly higher compared to the PM groups. Serum OPN levels positively correlated with creatinine kinase (CK), C-reactive protein (CRP) in PM and DM patients, respectively. After corticosteroid treatment, serum OPN levels decreased significantly in steroid responders compared to baseline, but no significant decrease was observed in steroid non-responders.


CONCLUSIONS
OPN is increased in patients with DM and PM, both in muscle and serum. OPN may play an important role in the pathogenesis of IIMs. Moreover, serum OPN may be a potential biomarker for this illness, and changes in serum OPN may provide an index of therapeutic efficacy.
Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Fei
F
Xiao
Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Jia-ze
JZ
Tan
Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Xin
X
Xu
Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Bin-lin
BL
Zhu
Department of Dermatology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Sheng
S
Fang
Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Xue-feng
XF
Wang
D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001706:Biopsy; D015153:Blotting, Western; D002097:C-Reactive Protein / Q000378:metabolism; D016022:Case-Control Studies; D003402:Creatine Kinase / Q000097:blood; D003882:Dermatomyositis / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D053495:Osteopontin / Q000097:blood*; D017285:Polymyositis / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy; D011237:Predictive Value of Tests; D011241:Prednisone / Q000627:therapeutic use; D016896:Treatment Outcome; D015854:Up-Regulation; D055815:Young Adult
D015415:Biomarkers; D005938:Glucocorticoids; D018836:Inflammation Mediators; C506895:SPP1 protein, human; D053495:Osteopontin; D002097:C-Reactive Protein; D003402:Creatine Kinase; D011241:Prednisone