Background Sclerostin is a negative regulator of bone formation that might be involved in osteoarthritis (OA) pathophysiology.

Objectives Our aim was to analyze the association between spine OA severity and serum sclerostin concentration in older men.

Methods In this cross-sectional analysis of 694 men aged 50-85 years, spine osteoarthritis was assessed at 6 intervertebral spaces using Lane's score [1]. Total score of osteophytes was calculated as the sum of osteophyte scores for each intervertebral level. Total scores of disc space narrowing and of subchondral sclerosis were calculated similarly. Sclerostin level was measured in fasting serum using ELISA assay (TECOsclerostin EIA kit, TECOmedical). Bone mineral density (BMD) at the total hip was measured by dual energy X-ray absorptiometry using the HOLOGIC 1000W device.

Results After adjustment for age, weight, serum 17beta-estradiol concentration and glomerular filtration rate, serum sclerostin level increased across the quartiles of total osteophyte score (p for trend <0.001). Sclerostin level was 15% (0.42SD, p<0.001) higher in the highest quartile of total osteophyte score (>12) compared with the lowest quartile (≤5). After similar adjustments, the analysis was performed in four groups defined by the most severe grade of osteophytes (no or mild, moderate, severe). Average sclerostin level increased with the increasing osteophyte grade (p for trend <0.001). It was 13% (0.37SD, p<0.005) higher in the 471 men who had at least one intervertebral level with severe osteophytes compared with the 109 men who had no or mild osteophytes. The associations between osteophyte severity (quartiles, grades) and sclerostin level remained significant (p<0.05 to <0.01) after additional adjustment for total hip BMD, disc space narrowing score and subchondral sclerosis score.

After adjustment for confounders, serum sclerostin increased across the quartiles of total disc space narrowing score (p for trend <0.001). It was 12% (0.38 SD, p<0.001) higher in the highest quartile vs the lowest quartile. After similar adjustment, the analysis was performed in four groups defined by the most severe grade of disc space narrowing. Average serum sclerostin increased with the increasing grade of disc space narrowing (p for trend <0.005). However, all the associations between disc space narrowing (quartiles, grades) and sclerostin levels lost significance (p>0.23) after additional adjustment for total hip BMD, osteophyte severity and subchondral sclerosis score.

There was a non-significant trend to higher sclerostin levels in men with subchondral sclerosis at ≥2 intervertebral levels in comparison with other men (5%, 0.18SD, p=0.053). This trend became non-significant after additional adjustment for total hip BMD, osteophyte severity and disc space narrowing score (p=0.88).

Conclusions In older men severe osteophytes - but not severe disc space narrowing or subchondral sclerosis - were independently associated with higher sclerostin concentration.

References

1. Lane NE, Nevitt MC, Genant HK, Hochberg MC. Reliability of new indices of radiographic osteoarthritis of the hand and hip and lumbar disc degeneration. J Rheumatol. 1993 20:1911-8.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.4225