Rats made congenic for Oia3 on chromosome 10 become susceptible to squalene-induced arthritis

Several quantitative trait loci (QTLs) regulating the risk of experimental arthritis have been identified by genome-wide linkage analyses, but only the MHC has thus far been reported to transfer arthritis susceptibility in congenic animals. We have produced a congenic strain for Oia3, a genetic factor originally identified as an oil-induced arthritis (OIA) QTL in arthritis-prone DA rats. A 46 cM telomeric region of chromosome 10 encompassing Oia3 was transferred from DA rats to MHC-identical but minutely arthritis-susceptible LEW.1AV1 rats by selective breeding. Arthritis development was provoked in Oia3-congenic rats by intradermal injection of different adjuvant oils. One successful arthritis trigger was squalene, which is approved for vaccinations in humans and has been implicated in Gulf War syndrome. The endogenous cholesterol precursor squalene induced T cell infiltration into joints and macroscopic arthritis in Oia3-congenic rats and DA rats, whereas LEW.1AV1 rats were almost resistant. Arthritis onset, approximately 14 days post-injection, coincided with arrested body-weight gain and increased plasma levels of the inflammation markers fibrinogen and alpha 1-acid glycoprotein. Congenic rats displayed intermediate phenotypes compared with the two parental strains, and similar to rheumatoid arthritis in humans, female preponderance was observed in Oia3-congenic rats. Finally, recombinant rat strains were constructed and were used to map a susceptibility gene(s) in females to a telomeric 4--19 cM Oia3 subregion. The experimental system described allows transformation of multifactorial arthritis susceptibility into dichotomous phenotypes.