Treg Promoted New Bone Formation Through Suppressing Th17 by Secreting IL-10 in AS.

MINI: Treg induced NBF of AS through suppressing Th17 by secreting IL10 and declining of the ratio of Th17/Treg indicated the development of NBF. This is important not only for screening development of NBF, but also for control of NBF of AS by immune therapy. STUDY DESIGN Retrospective single- center study. OBJECTIVE We want to know if IL10-secreting regulatory T cells (Treg) promote the NBF through suppressing Th17 in AS. SUMMARY OF BACKGROUND DATA New bone formation (NBF) in ankylosing spondylitis (AS) is unknown. Since there' are balances of bone remodeling in human body and proinflammatory helper T cells Th17 promoted bone resorption. METHODS 18 AS patients with or without NBF (both 9 cases) and 9 healthy individuals were selected and the demographic data, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), MRI sacroiliitis score (MRISIS) and computer tomography sacroiliitis score (CTSIS) recorded. Removed hip ligament tissue in the lesions after arthroplasty was collected and the lymphocytes and the peripheral blood mononuclear cells were prepared. Secondly, pathological section in H.E. stain were analyzed and flow cytometry and quantitative PCR analyses were carried out to detect the levels of Th17, Treg, IL10 and NFKB, and the relevance between them. The effect of Treg on Th17 was further analyzed by using Transwell coculturing. RESULTS Compared to AS patients without NBF, AS patients with NBF had significantly higher CTSIS and complications (p value <0.05 and 0.01, respectively), but significantly lower BASDAI (3.0±0.4) and MRISIS (3.3 ± 0.8) (p value <0.01 and 0.05, respectively) and no acute inflammation in H.E. stain for hip joint. Compared to healthy donors, the ratio of Th17/Treg was significantly higher in AS patients without NBF and lower in AS patient with NBF (both p value <0.01) in FCA. Furthermore, Th17 significantly decreased after indirectly co-culturing with Treg in FCA (p value <0.01). Finally, IL10 had significantly higher mRNA expression in AS patients with NBF (p value <0.01), and NFKB had significantly higher mRNA expression in AS patients without NBF (p value <0.05) than healthy donors. Only the mRNA expression of IL10 was significantly correlated to the ratio of Th17/Treg (r=-0.93, p value <0.01). CONCLUSIONS Treg induced NBF of AS through suppressing Th17 by secreting IL10 and declining of the ratio of Th17/Treg indicated the development of NBF. This is important not only for screening development of NBF, but also for control of NBF of AS by immune therapy. LEVEL OF EVIDENCE N/A.