Bone Abstracts

Background: Children with inflammatory bowel disease (IBD) have reduced bone mineral density (BMD). The aim of this study was to investigate whether changes in patient’s cellular immune response correlate with reductions in BMD.

Method: Children undergoing lower gastrointestinal endoscopy disease were approached with an aim of recruiting 15 patients newly diagnosed with Crohn’s Disease (CD) and 15 healthy controls. Lymphocytes were isolated from blood and mucosal biopsies, and analysed by flow cytometry including identification of gut primed lymphocytes expressing α4β7. The bone turnover markers osteocalcin, Type 1 procollagen amino-terminal propeptide (P1NP) and N-telopeptide of type 1 collagen (NTX) were measured in all participants. In CD patients lumbar BMD was measured by DXA.

Results: About 14 cases were recruited, of which 10 were newly diagnosed with CD. In cases there was a reduction in the percentage of white blood cells that were lymphocytes (P=0.022), with an increase in expression of CD25 by circulating CD4⁺ lymphocytes (P=0.019), and α4β7⁺CD4⁺ lymphocytes (P=0.005). Cases also had a significant reduction in their vBMD (0.29 vs 0.26 g/cm³; P=0.002), significant reductions in P1NP (P=0.08) and non-significant reductions in both osteocalcin and NTX. There was a positive correlation between numbers of CD4⁺ and α4β7⁺CD4⁺ lymphocytes and vBMD, whilst those cells expression of CD25 was negatively correlated with vBMD.

Conclusion: This is the first study demonstrating reductions in BMD alongside alterations in the cellular immune response in children with IBD, with uncoupling of bone metabolism. The small patient cohort potentially explains why correlations between the cellular immune response and BMD were not statistically significant. However, that the numbers of circulating lymphocytes and their activation status have potentially opposing influences makes further investigation of osteoimmune interactions in paediatric IBD warranted.

Disclosure: The authors declared no competing interests.