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Disease severity in K/BxN serum transfer-induced arthritis is not affected by IL-33 deficiency.

Martin P, Talabot-Ayer D, Seemayer CA, Vigne S, Lamacchia C, Rodriguez E, Finckh A, Smith DE, Gabay C, Palmer G - Arthritis Res. Ther. (2013)

Bottom Line: Interleukin (IL)-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor.Disease severity was monitored by clinical and histological scoring.This observation might relate to IL-33 independent effects of ST2, and/or reveal the existence of confounding variables affecting the severity of joint inflammation in these KO strains.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Introduction: Interleukin (IL)-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor. Previous work suggested implication of the IL-33/ST2 axis in the pathogenesis of human and mouse arthritis. Here, we directly investigated the role of endogenous IL-33 in K/BxN serum transfer-induced arthritis by using IL-33 knockout (KO) mice.

Methods: Arthritis was induced by injection of complete K/BxN serum or purified IgG. Disease severity was monitored by clinical and histological scoring.

Results: K/BxN serum transfer induced pronounced arthritis with similar incidence and severity in IL-33 KO and wild-type (WT) mice. In contrast, disease development was significantly reduced in ST2 KO mice. IL-33 expression in synovial tissue was comparable in arthritic WT and ST2 KO mice, and absent in IL-33 KO mice. Transfer of purified arthritogenic IgG instead of complete K/BxN serum also resulted in similar arthritis severity in IL-33 KO and WT mice, excluding a contribution of IL-33 contained in the serum of donor mice to explain this result. We investigated additional potential confounding factors, including purity of genetic background, but the mechanisms underlying reduced arthritis in ST2 KO mice remained unclear.

Conclusions: The data obtained with IL-33 KO mice indicate that endogenous IL-33 is not required for the development of joint inflammation in K/BxN serum transfer-induced arthritis. On the contrary, arthritis severity was reduced in ST2 KO mice. This observation might relate to IL-33 independent effects of ST2, and/or reveal the existence of confounding variables affecting the severity of joint inflammation in these KO strains.

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Influence of 129 genetic background carryover on arthritis severity in ST2 KO mice. (A) Schematic representation of markers screened on chromosome 1, cM 0-32. (B) Heterogeneity of genetic background in ST2 KO mice upstream of the ST2 locus on chromosome 1, as assessed by size differences in markers D1Mit3 and D1Mit211, in the ST2 KO (n = 10, lanes 1 to 10) mice used for the arthritis experiment shown in Figure 1. M, size ladder; B6, C57BL/6 control DNA; 129, 129SvPas control DNA; F1, B6x129F1 hybrid control DNA; bp, base pairs. (C) Correlation of D1Mit211 (left panel), D6Mit159 (middle panel) and D15Mit193 (right panel) genotypes (B6, hybrid or 129) with maximal clinical arthritis severity scores in the ST2 KO mice (n = 20) used for the arthritis experiments shown in Figure 1 and 3. Absolute values for arthritis severity scores were corrected for overall mean maximal severity in each experiment. KO, knockout.
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Figure 6: Influence of 129 genetic background carryover on arthritis severity in ST2 KO mice. (A) Schematic representation of markers screened on chromosome 1, cM 0-32. (B) Heterogeneity of genetic background in ST2 KO mice upstream of the ST2 locus on chromosome 1, as assessed by size differences in markers D1Mit3 and D1Mit211, in the ST2 KO (n = 10, lanes 1 to 10) mice used for the arthritis experiment shown in Figure 1. M, size ladder; B6, C57BL/6 control DNA; 129, 129SvPas control DNA; F1, B6x129F1 hybrid control DNA; bp, base pairs. (C) Correlation of D1Mit211 (left panel), D6Mit159 (middle panel) and D15Mit193 (right panel) genotypes (B6, hybrid or 129) with maximal clinical arthritis severity scores in the ST2 KO mice (n = 20) used for the arthritis experiments shown in Figure 1 and 3. Absolute values for arthritis severity scores were corrected for overall mean maximal severity in each experiment. KO, knockout.

Mentions: IL-33 KO and ST2 KO mice were generated in 129Sv, respectively 129P2/OlaHsd ES cells and backcrossed to a C57BL/6 background. It has become increasingly clear that despite extensive backcrossing, genetic material of the original mouse strain, and in particular regions closely linked to the targeted loci, remains associated to KOs in recipient strains, sometimes leading to confounding effects mistakenly attributed to the disrupted gene [38,39]. We thus wondered whether carryover of 129 genetic material might have influenced the outcome of our experiments. IL-33 KO mice were considered 100% C57BL/6 congenic at the end of their backcross based on screening of a 377-marker panel. In addition, at the end of the experiment shown in Figure 1, we screened three mice per genotype using a 55-marker panel [32] to obtain a picture of the genetic background in our local mouse colonies. We confirmed 98% purity of the C57BL/6 background in WT (one heterogeneous marker: D4Mit166) and 100% purity in IL-33 KO mice. Screening of ST2 KO mice revealed lower (89%) purity (six heterogeneous markers: D1Mit211, D6Mi166, D6Mit159, D6Mit102, D11Mit224, D15Mit193). We further examined two additional markers close to the Il1rl1 gene on chromosome 1 (D1Mit3 and D1Mit75a, Figure 6A, Table 2), one of which (D1Mit3) was also non-C57BL/6 in 17 out of 20 ST2 KO mice tested (Figure 6B and data not shown). In contrast, the D1Mit75a and D1Mit303 markers, located downstream of the ST2 locus were C57BL/6 in all ST2 KO mice examined. Finally, we screened the 20 ST2 KO mice used in arthritis experiments (Figure 1 and 3) for the presence of either C57BL/6, or 129 alleles at the D1Mit211, D6Mi166, D6Mit159, D6Mit102, and D15Mit193 loci and correlated their genotypes with arthritis severity of individual mice (Figure 6C and data not shown). With the limited number of mice included in these studies, we observed no significant correlations. However, arthritis severity in mice carrying two C57BL/6 alleles at a given locus often tended to be lowest (D1Mit211, D6Mit166; D6Mit159).


Disease severity in K/BxN serum transfer-induced arthritis is not affected by IL-33 deficiency.

Martin P, Talabot-Ayer D, Seemayer CA, Vigne S, Lamacchia C, Rodriguez E, Finckh A, Smith DE, Gabay C, Palmer G - Arthritis Res. Ther. (2013)

Influence of 129 genetic background carryover on arthritis severity in ST2 KO mice. (A) Schematic representation of markers screened on chromosome 1, cM 0-32. (B) Heterogeneity of genetic background in ST2 KO mice upstream of the ST2 locus on chromosome 1, as assessed by size differences in markers D1Mit3 and D1Mit211, in the ST2 KO (n = 10, lanes 1 to 10) mice used for the arthritis experiment shown in Figure 1. M, size ladder; B6, C57BL/6 control DNA; 129, 129SvPas control DNA; F1, B6x129F1 hybrid control DNA; bp, base pairs. (C) Correlation of D1Mit211 (left panel), D6Mit159 (middle panel) and D15Mit193 (right panel) genotypes (B6, hybrid or 129) with maximal clinical arthritis severity scores in the ST2 KO mice (n = 20) used for the arthritis experiments shown in Figure 1 and 3. Absolute values for arthritis severity scores were corrected for overall mean maximal severity in each experiment. KO, knockout.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 6: Influence of 129 genetic background carryover on arthritis severity in ST2 KO mice. (A) Schematic representation of markers screened on chromosome 1, cM 0-32. (B) Heterogeneity of genetic background in ST2 KO mice upstream of the ST2 locus on chromosome 1, as assessed by size differences in markers D1Mit3 and D1Mit211, in the ST2 KO (n = 10, lanes 1 to 10) mice used for the arthritis experiment shown in Figure 1. M, size ladder; B6, C57BL/6 control DNA; 129, 129SvPas control DNA; F1, B6x129F1 hybrid control DNA; bp, base pairs. (C) Correlation of D1Mit211 (left panel), D6Mit159 (middle panel) and D15Mit193 (right panel) genotypes (B6, hybrid or 129) with maximal clinical arthritis severity scores in the ST2 KO mice (n = 20) used for the arthritis experiments shown in Figure 1 and 3. Absolute values for arthritis severity scores were corrected for overall mean maximal severity in each experiment. KO, knockout.
Mentions: IL-33 KO and ST2 KO mice were generated in 129Sv, respectively 129P2/OlaHsd ES cells and backcrossed to a C57BL/6 background. It has become increasingly clear that despite extensive backcrossing, genetic material of the original mouse strain, and in particular regions closely linked to the targeted loci, remains associated to KOs in recipient strains, sometimes leading to confounding effects mistakenly attributed to the disrupted gene [38,39]. We thus wondered whether carryover of 129 genetic material might have influenced the outcome of our experiments. IL-33 KO mice were considered 100% C57BL/6 congenic at the end of their backcross based on screening of a 377-marker panel. In addition, at the end of the experiment shown in Figure 1, we screened three mice per genotype using a 55-marker panel [32] to obtain a picture of the genetic background in our local mouse colonies. We confirmed 98% purity of the C57BL/6 background in WT (one heterogeneous marker: D4Mit166) and 100% purity in IL-33 KO mice. Screening of ST2 KO mice revealed lower (89%) purity (six heterogeneous markers: D1Mit211, D6Mi166, D6Mit159, D6Mit102, D11Mit224, D15Mit193). We further examined two additional markers close to the Il1rl1 gene on chromosome 1 (D1Mit3 and D1Mit75a, Figure 6A, Table 2), one of which (D1Mit3) was also non-C57BL/6 in 17 out of 20 ST2 KO mice tested (Figure 6B and data not shown). In contrast, the D1Mit75a and D1Mit303 markers, located downstream of the ST2 locus were C57BL/6 in all ST2 KO mice examined. Finally, we screened the 20 ST2 KO mice used in arthritis experiments (Figure 1 and 3) for the presence of either C57BL/6, or 129 alleles at the D1Mit211, D6Mi166, D6Mit159, D6Mit102, and D15Mit193 loci and correlated their genotypes with arthritis severity of individual mice (Figure 6C and data not shown). With the limited number of mice included in these studies, we observed no significant correlations. However, arthritis severity in mice carrying two C57BL/6 alleles at a given locus often tended to be lowest (D1Mit211, D6Mit166; D6Mit159).

Bottom Line: Interleukin (IL)-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor.Disease severity was monitored by clinical and histological scoring.This observation might relate to IL-33 independent effects of ST2, and/or reveal the existence of confounding variables affecting the severity of joint inflammation in these KO strains.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Introduction: Interleukin (IL)-33 is a cytokine of the IL-1 family, which signals through the ST2 receptor. Previous work suggested implication of the IL-33/ST2 axis in the pathogenesis of human and mouse arthritis. Here, we directly investigated the role of endogenous IL-33 in K/BxN serum transfer-induced arthritis by using IL-33 knockout (KO) mice.

Methods: Arthritis was induced by injection of complete K/BxN serum or purified IgG. Disease severity was monitored by clinical and histological scoring.

Results: K/BxN serum transfer induced pronounced arthritis with similar incidence and severity in IL-33 KO and wild-type (WT) mice. In contrast, disease development was significantly reduced in ST2 KO mice. IL-33 expression in synovial tissue was comparable in arthritic WT and ST2 KO mice, and absent in IL-33 KO mice. Transfer of purified arthritogenic IgG instead of complete K/BxN serum also resulted in similar arthritis severity in IL-33 KO and WT mice, excluding a contribution of IL-33 contained in the serum of donor mice to explain this result. We investigated additional potential confounding factors, including purity of genetic background, but the mechanisms underlying reduced arthritis in ST2 KO mice remained unclear.

Conclusions: The data obtained with IL-33 KO mice indicate that endogenous IL-33 is not required for the development of joint inflammation in K/BxN serum transfer-induced arthritis. On the contrary, arthritis severity was reduced in ST2 KO mice. This observation might relate to IL-33 independent effects of ST2, and/or reveal the existence of confounding variables affecting the severity of joint inflammation in these KO strains.

Show MeSH
Related in: MedlinePlus