Research article
BALB/c mice genetically susceptible to proteoglycan-induced arthritis and spondylitis show colony-dependent differences in disease penetrance
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* Corresponding author: Tibor T Glant tglant@rush.edu
1 Section of Molecular Medicine, Department of Orthopedic Surgery, Rush University Medical Center, 1735 W. Harrison Street, Cohn Research Building, Chicago, IL 60612, USA
2 Department of Immunology and Biotechnology, University of Pecs, Ifjusag u. 13, Pecs, Hungary
3 Biomedical Informatics Center, Northwestern University, 750 N. Lake Shore Drive, Chicago, IL 60611, USA
4 Department of Ophthalmology, Portland, Oregon Health Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239, USA
5 Department of Internal Medicine (Section of Rheumatology), Rush University Medical Center, 1730 W. Harrison Street, Cohn Research Building, Chicago, IL 60612, USA
6 Department of Immunology/Microbiology, Rush University Medical Center, 1730 W. Harrison Street, Cohn Research Building, Chicago, IL 60612, USA
7 Department of Biochemistry, Rush University Medical Center, 1730 W. Harrison Street, Cohn Research Building, Chicago, IL 60612, USA
Arthritis Research & Therapy 2009, 11:R21 doi:10.1186/ar2613
Published: 16 February 2009Abstract
Introduction
The major histocompatibility complex (H-2d) and non-major histocompatibility complex genetic backgrounds make the BALB/c strain highly susceptible to inflammatory arthritis and spondylitis. Although different BALB/c colonies develop proteoglycan-induced arthritis and proteoglycan-induced spondylitis in response to immunization with human cartilage proteoglycan, they show significant differences in disease penetrance despite being maintained by the same vendor at either the same or a different location.
Methods
BALB/c female mice (24 to 26 weeks old after 4 weeks of acclimatization) were immunized with a suboptimal dose of cartilage proteoglycan to explore even minute differences among 11 subcolonies purchased from five different vendors. In vitro-measured T-cell responses, and serum cytokines and (auto)antibodies were correlated with arthritis (and spondylitis) phenotypic scores. cDNA microarrays were also performed using spleen cells of naïve and immunized BALB/cJ and BALB/cByJ mice (both colonies from The Jackson Laboratory, Bar Harbor, ME, USA), which represent the two major BALB/c sublines.
Results
The 11 BALB/c colonies could be separated into high (n = 3), average (n = 6), and low (n = 2) responder groups based upon their arthritis scores. While the clinical phenotypes showed significant differences, only a few immune parameters correlated with clinical or histopathological abnormalities, and seemingly none of them affected differences found in altered clinical phenotypes (onset time, severity or incidence of arthritis, or severity and progression of spondylitis). Affymetrix assay (Affymetrix, Santa Clara, CA, USA) explored 77 differentially expressed genes (at a significant level, P < 0.05) between The Jackson Laboratory's BALB/cJ (original) and BALB/cByJ (transferred from the National Institutes of Health, Bethesda, MD, USA). Fourteen of the 77 differentially expressed genes had unknown function; 24 of 77 genes showed over twofold differences, and only 8 genes were induced by immunization, some in both colonies.
Conclusions
Using different subcolonies of the BALB/c strain, we can detect significant differences in arthritis phenotypes, single-nucleotide polymorphisms (SNPs), and a large number of differentially expressed genes, even in non-immunized animals. A number of the known genes (and SNPs) are associated with immune responses and/or arthritis in this genetically arthritis-prone murine strain, and a number of genes of as-yet-unknown function may affect or modify clinical phenotypes of arthritis and/or spondylitis.