PTPN2 links colonic and joint inflammation in experimental autoimmune arthritis
Wan-Chen Hsieh, Mattias N.D. Svensson, Martina Zoccheddu, Michael L. Tremblay, Shimon Sakaguchi, Stephanie M. Stanford, Nunzio Bottini
Wan-Chen Hsieh, Mattias N.D. Svensson, Martina Zoccheddu, Michael L. Tremblay, Shimon Sakaguchi, Stephanie M. Stanford, Nunzio Bottini
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Research Article Inflammation

PTPN2 links colonic and joint inflammation in experimental autoimmune arthritis

Abstract

Loss-of-function variants of protein tyrosine phosphatase non-receptor type 2 (PTPN2) enhance risk of inflammatory bowel disease and rheumatoid arthritis; however, whether the association between PTPN2 and autoimmune arthritis depends on gut inflammation is unknown. Here we demonstrate that induction of subclinical intestinal inflammation exacerbates development of autoimmune arthritis in SKG mice. Ptpn2-haploinsufficient SKG mice — modeling human carriers of disease-associated variants of PTPN2 — displayed enhanced colitis-induced arthritis and joint accumulation of Tregs expressing RAR-related orphan receptor γT (RORγt) — a gut-enriched Treg subset that can undergo conversion into FoxP3–IL-17+ arthritogenic exTregs. SKG colonic Tregs underwent higher conversion into arthritogenic exTregs when compared with peripheral Tregs, which was exacerbated by haploinsufficiency of Ptpn2. Ptpn2 haploinsufficiency led to selective joint accumulation of RORγt-expressing Tregs expressing the colonic marker G protein–coupled receptor 15 (GPR15) in arthritic mice and selectively enhanced conversion of GPR15+ Tregs into exTregs in vitro and in vivo. Inducible Treg-specific haploinsufficiency of Ptpn2 enhanced colitis-induced SKG arthritis and led to specific joint accumulation of GPR15+ exTregs. Our data validate the SKG model for studies at the interface between intestinal and joint inflammation and suggest that arthritogenic variants of PTPN2 amplify the link between gut inflammation and arthritis through conversion of colonic Tregs into exTregs.

Authors

Wan-Chen Hsieh, Mattias N.D. Svensson, Martina Zoccheddu, Michael L. Tremblay, Shimon Sakaguchi, Stephanie M. Stanford, Nunzio Bottini

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Figure 4

PTPN2 maintains the stability of colonic Tregs.

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PTPN2 maintains the stability of colonic Tregs. (A) Schematic of SKG Tre...
(A) Schematic of SKG Treg fate-mapping mouse. (B) Left: representative flow cytometric gating of IL-17–producing cells among tdTomato+CD4+ T cells isolated from B6.SKG.H2d/d FoxP3YFP.Cre+/– tdTomatofl/+ Ptpn2+/+ or Ptpn2fl/+ Treg fate-mapping mice. Right: frequency of IL-17–producing exTregs (CD4+tdTomato+IL-17A+FoxP3YFP–) in spleens and colons isolated from 12-week-old prearthritic Treg fate-mapping SKG mice. (C) In vitro conversion assay of Ptpn2+/+ (n = 6) and Ptpn2+/– (n = 5) colonic SKG Tregs (cTregs) into IL-17–producing ex-cTregs (CD4+IL-17+FoxP3–). Cells were analyzed after 4 days of stimulation. Left: representative flow cytometry plots. Right: frequency of ex-cTregs. (D–G) CD45.1 SKG CD4+ FoxP3EGFP+ colonic Tregs (cTregs) or splenic Tregs (spTreg) were cotransferred with CD45.2 SKG CD4+CD25– effector T cells (Teffs) into Rag2-KO recipient mice (n = 4/group). Arthritis was induced in recipient mice 1 week after transfer by injection of mannan, and mice were analyzed at day 35. (D) Schematic for adoptive transfer experiment. (E) Clinical score and change in ankle thickness of recipient mice. (F) Frequency of CD45.1 IL-17A+ exTregs (CD4+IL-17+FoxP3–) in ankles of arthritic recipient mice. (G) Frequency of Th17 (CD4+IL-17A+FoxP3–) among transferred CD45.2 SKG CD4+CD25– Teffs in ankles of arthritic recipient mice. (H–K) Cotransfer of CD45.2 SKG CD4+FoxP3EGFP+ Ptpn2+/+ or Ptpn2+/– cTregs together with CD45.1 SKG CD4+CD25– Ptpn2+/+ Teff into Rag2-KO recipient mice (n = 7/group). Arthritis was induced in recipient mice 1 week after transfer by injection of mannan, and mice were analyzed at day 28. (H) Schematic for adoptive transfer experiment. (I) Clinical score and change in ankle thickness in recipient mice. (J) Frequency of Ptpn2+/+ and Ptpn2+/– CD45.2 IL-17A+ ex-cTregs (CD4+IL-17A+FoxP3–) in ankles of arthritic recipient mice. (K) Frequency of Th17 (CD45.1+CD4+IL-17A+FoxP3–) among CD45.1 Teff in ankles of arthritic recipient mice. Compiled data from 2 independent experiments are shown in A–K. Each symbol in B, C, F, G, J, and K represents an individual mouse. Arthritis severity was quantified using the area under the curve. Graphs show mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 by 2-way ANOVA (B), unpaired t test (C, F, G, and J–K), or Mann-Whitney U test (E and I).