RESEARCH - Cellular characterization of MRI bone edema in RA; implication for pathogenesis of erosive disease

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Ann Rheum Dis. 2008 Sep 2.

Cellular characterization of magnetic resonance imaging (MRI) bone

edema in rheumatoid arthritis; implications for pathogenesis of

erosive disease.

Dalbeth N, T, Gray S, Doyle A, Antill P, Lobo M, E,

King A, Cornish J, Shalley G, Gao A, McQueen FM.

University of Auckland, New Zealand.

Aims: MRI bone edema is an important predictor of bone erosion in

rheumatoid arthritis (RA). This study aimed to determine the cellular

components of MRI bone edema, and clarify the relationship between

bone erosion and MRI bone edema.

METHODS: Twenty-eight bones from 11 patients with RA undergoing

orthopedic surgery were analyzed by quantitative and semi-quantitative

immunohistochemistry. Pre-operative contrast-enhanced MRI scans were

analyzed for bone edema.

RESULTS: The density of osteoclasts was higher in those samples with

MRI bone edema than those without MRI bone edema (p=0.01). Other cells

identified within bone marrow included macrophages and plasma cells,

and these were more numerous in samples with MRI bone edema (p=0.02

and 0.05 respectively). B cells were present in lower numbers, but B

cell aggregates were identified in some samples with MRI bone edema.

There was a trend to increased RANKL expression in samples with MRI

bone edema (p=0.09). Expression of RANKL correlated with the number of

osteoclasts (r=0.592, p=0.004).

Summary: The increased number of osteoclasts and RANKL expression in

samples with MRI bone edema supports the hypothesis that bone erosion

in RA occurs through activation of local bone resorption mechanisms

within subchondral bone as well as through synovial invasion into

bone.

PMID: 18765428

http://www.ncbi.nlm.nih.gov/pubmed/18765428

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