THU0368 IL-22 Impact on Human Bone Marrow Mesenchymal Stem Cells Functions; A Novel Pathway That May Contribute To Aberrant New Bone Formation in Human SPA
Authors: Y. El-Sherbiny, A. El-Zayadi, S. Churchman, T. Baboolal, R. Cuthbert, J. El-Jawhari, A. Alase, A. Badawy, E. Jones, D. McGonagle
Journal: Annals of the Rheumatic Diseases (2016)

<h3>Background</h3> The spondyloarthropathies (SpAs) including ankylosing spondylitis (AS) show a propensity for florid new bone formation following bouts of inflammation. However, in other skeletal diseases such as rheumatoid arthritis, inflammation predictably leads to diffuse bone loss and periarticular erosion.<sup>1</sup> Anti-TNF therapies effectively alleviate spinal inflammation in SpA but fail to arrest the new bone formation. SpAs are genetically and therapeutically linked to IL-23, which in turn regulates IL-22. it is a master regulator of stem cell niches in the intestine, liver, endometrium and skin<sup>2</sup> but to the best of our knowledge, no data on its influence upon human osteoprogenitors or MSCs has been described. <h3>Objectives</h3> We hypothesized that IL-22, a master regulator of stem cells in other niches, might also regulate mesenchymal stem cell (MSC) osteogenesis in an inflammation-dependent context. <h3>Methods</h3> Bone marrow samples were obtained after informed consent (n=10), and MSCs isolated and culture expanded for 2–4 passages. Cells were analysed using flowcytometry for ISCT criteria and expression IL-22R ±IFNG and TNFa stimulation. IL-22 effects were tested with and without inflammatory cytokines (IFNG and TNFa) on: MSC proliferation using colorimetric XTT assay, MSC migration using transwell migration assays, the expression of trascriptional factors of MSC adipo-, osteo- or chondro-genic potential using qRT-PCR, and on osteogenic differentiation assay evaluated by colorimetric calcium assay. <h3>Results</h3> Interestingly, IL-22R expression was detected in MSCs intracellularly and showed a mean 1.8±0.12 fold increase post IFNG and TNFa stimulation. MSC stimulation with combined IL-22, IFNG and TNFa but not single cytokines increased MSC proliferation (p=0.008) and migration (p=0.037) compared to unstimulated MSCs. Osteogenic, adipogenic but not chondrogenic transcription factors were upregulated by IL-22 (p&lt;0.05). Moreover, Inflammatory stimuli (IFNG+TNFa±IL-22) did not affect the chondro- and adipogenic transcription factors but did temper the increase of pro-osteogenic <i>RUNX2</i>. Mature bone markers, particularly <i>BGLAP</i>/osteocalcin were rarely detectable in the presence of inflammation. The inflammatory milieu also downregulated all tested chondrogenic markers <i>ACAN</i>, <i>COL2A1</i> and <i>COL10A1</i> compared to unstimulated and IL-22 stimulated MSCs. Notably, MSC osteogenesis was enhanced following IL-22 exposure (p=0.031 for calcium production). The combination of IFNG and TNFa with or without IL-22 suppressed MSC osteogenesis (p=0.0313 for both). <h3>Conclusions</h3> This is the first study to show that IL-22 is involved in MSC proliferation/migration in inflammatory environments with MSC osteogenesis occurring only in IFNG/TNFa absence. Given the genetic link with SpA, these physiological MSC bone responses need evaluation in pathological post-inflammation osteogenesis in human SpA. <h3>References</h3> Hreggvidsdottir HS, Noordenbos T, Baeten DL. Inflammatory pathways in spondyloarthritis. Mol Immunol 2014;57(1):28–37. Feng D, Kong X, Weng H, et al. Interleukin-22 promotes proliferation of liver stem/progenitor cells in mice and patients with chronic hepatitis B virus infection. Gastroenterology 2012;143(1):188–98 e7. <h3>Disclosure of Interest</h3> None declared