BACKGROUND: Spondyloarthritis is a family of related inflammatory diseases including psoriatic arthritis and ankylosing spondylitis. The cytokine IL-23 is known to play an important role in spondyloarthritis development. Overexpression of IL-23 using IL-23 minicircle DNA in B10.RIII mice results in the development of a spondyloarthritis-like disease. B10.RIII is a major histocompatibility complex (MHC) congenic mouse strain that is susceptible to a number of autoimmune and autoinflammatory diseases. Contaminating regions outside the congenic interval from the donor strain, RIII, have been previously detected. While B10.RIII mice develop collagen-induced arthritis (CIA) and collagen antibody induced arthritis (CAIA), the background strain, C57BL/10 (B10) does not. The MHC region is known to play a role in the susceptibility of B10.RIII mice to CIA, but not in CAIA development, so other regions must be involved in arthritis development as well. These contaminating RIII-derived regions may control susceptibility to IL-23 minicircle induced arthritis in B10.RIII mice. OBJECTIVE: This study aimed to identify RIII-derived regions in the genome of B10.RIII mice and begin to interrogate their effects on IL-23 minicircle induced arthritis. METHODS: A systematic literature review was conducted using Pubmed and Web of Science. Articles using B10.RIII mice to study inflammatory disease models were included and data about year of publication, inbred mouse strains used, disease model, and inbred strain notation were extracted. Genome sequences of B10.RIII(71NS)/Sn, C57BL/10SnJ, and C57BL/10J were compared to identify RIII-derived clusters of variation in the B10.RIII genome. B10.RIII mice were crossed with B10 mice and subsequently backcrossed to B10.RIII mice to introduce the B10 allele at chromosome 15. Chr15b/b, Chr15b/r, and Chr15r/r B10.RIII mice were hydrodynamically injected with IL-23 minicircles, and arthritis development was monitored every other day for two weeks. RESULTS: The systematic literature review yielded 8 studies that compared arthritis development in B10.RIII to RIII or B10. These studies identified three arthritis susceptibility regions: Cia5/Eae3 on chromosome 3, Eae2 on chromosome 15, and Eae39 on chromosome 5. Eae2 is further split into four sub-regions: Cia30, Cia31, Cia32, and Cia26. Genome sequence comparison identified RIII-derived clusters in B10.RIII mice on chromosomes 10, 14, 15, and 17. The chromosome 15 region overlaps with the Eae2 susceptibility region for approximately 17 Mbp and includes the arthritis susceptibility loci Cia26 and Cia32. When this region was interrogated in vivo, Chr15r/r and Chr15b/r B10.RIII mice developed IL-23 minicircle arthritis, while Chr15b/b mice did not. CONCLUSION: The B10.RIII(71NS)/Sn strain contains several large RIII/WySn-derived regions outside the congenic MHC region. One of these clusters on chromosome 15 includes the arthritis susceptibility loci Cia26 and Cia32 and appears to determine susceptibility to IL-23 minicircle induced arthritis. Future studies will interrogate the role of the chromosome 15 RIII-derived region in arthritis development in more detail and aim to identify the specific gene variants that control arthritis susceptibility. / 2023-01-28T00:00:00Z

BACKGROUND: Spondyloarthritis is a subset of inflammatory rheumatic diseases that includes ankylosing spondyloarthritis, psoriatic arthritis, undifferentiated spondyloarthritis, and arthritis related to inflammatory bowel. The IL-23 cytokine has been implicated in the pathogenesis of spondyloarthritis. B10.RIII mice hydrodynamically injected with IL-23 minicircle overexpress the IL-23 cytokine, which leads to the development of spondyloarthritis-like disease. It is important to note that B10.RIII is a major histocompatibility complex (MHC) congenic mouse strain that is susceptible to autoimmune and autoinflammatory diseases where the background strain, C57BL/10 (B10), or the MHC donor strain, RIIIS/J, is resistant. For instance, the B10.RIII strain of mice is susceptible to IL-23-induced arthritis, while the B10 background strain is not. Large contaminating RIII-derived regions outside of the selected congenic interval on chromosome 17 were identified on chromosomes 10, 14, 15, and 17. Genetic variations in these intervals may contribute to the susceptibility of the B10.RIII mice to arthritis induced by IL-23 minicircle. OBJECTIVE: This study aimed to interrogate the arthritis phenotype after IL-23 minicircle injection in Chr17 subcongenic B10.RIII mice. In addition, chromosome 17 RIII-derived Ilrun gene and its role in regulating the Interferon signaling pathway between the B10.RIII and B10 mice were investigated. METHOD: Chromosome 17 subcongenic mice were generated by crossing B10.RIII mice with B10 mice and backcrossing the offspring to the B10.RIII mice. Offspring heterozygous b/r for the Chr17 region were then intercrossed to generate B10.RIII mice that are identical to the B10.RIII mice, except at chromosome 17, where they had the genotypes Chr17b/b, Chr17b/r, or Chr17r/r. These mice were then hydrodynamically injected with IL-23 minicircle DNA, and disease development was monitored every other day for two weeks using two parameters: clinical arthritis score and paw swelling. Bone marrow-derived macrophages were differentiated in vitro from B10.RIII and B10 mice. Cells were stimulated with TLR agonists (Pam3CSK4, Poly (I:C), LPS) that induce either the Ilrun-regulated Interferon signaling pathway or the NF-kB signaling pathway. Gene expression changes of NF-kB and Interferon-induced genes were measured using real-time quantitative PCR. TNF protein concentration in the supernatant was measured by ELISA. RESULTS: Upon IL-23 minicircle injection, Chr17r/r and Chr17b/r B10.RIII mice developed arthritis while Chr17b/b B10.RIII mice did not. In addition, the disease severity increased with the number of r alleles as the Chr17r/r B10.RIII mice had a higher clinical score and paw swelling when compared to the heterozygote Chr17b/r mice. Gene expression analysis of NF-kB and Interferon response genes revealed that there was no difference in the induction of NF-kB and Interferon response genes in bone marrow-derived macrophages from B10.RIII and B10 mice. In addition, there was also no difference in the induction of the Ilrun gene in bone marrow-derived macrophages from B10.RIII and B10 mice. CONCLUSION: The B10.RIII(71NS)/Sn strain contains three major RIII/WySn-derived regions outside of the congenic MHC region. The chromosome 17 cluster appears to play a role in susceptibility to IL-23 minicircle-induced arthritis. In vitro studies with bone marrow-derived macrophages failed to show functional differences in Ilrun between the B10.RIII and B10 mice. Future studies will interrogate chromosome 17 RIII-derived regions in arthritis development in more detail and investigate the role of Ilrun in immune responses using Ilrun knock-out mice. / 2025-02-28T00:00:00Z