Genetic characterisation of spontaneous ankylosing arthropathy with unique inheritance from Fas-deficient strains of mice

FGF7 as an essential mediator for the onset of ankylosing enthesitis related to psoriatic dermatitis

IL-17A plays an important role in the pathology of psoriasis and psoriatic arthritis (PsA). However, the pathogenic association between the skin and joint manifestations in PsA is not completely understood. In this study, we initially observed that IL-17A and FGF7 induced endochondral ossification in the mouse entheseal histoculture. Importantly, the responses of endochondral ossification by IL-17A stimulation were strongly inhibited by the treatment of a blocking antibody to FGF receptor 2IIIb, which is the receptor of FGF7, suggesting that FGF7 acts as a downstream factor of IL-17A in the endochondral ossification in the culture. Next, using the animal PsA model, the administration of an anti-FGF receptor 2IIIb antibody resulted in significant suppression of ankylosing enthesitis but not dermatitis. Collectively, our findings indicate that augmented IL-17A in PsA dermatitis induces the elevation of FGF7 levels in joint enthesis and results in a non-redundant role of FGF7 signaling in the development of ankylosing enthesitis in PsA.

Ankylosing enthesitis associated with up-regulated IFN-gamma and IL-17 production in (BXSB x NZB) F(1) male mice: a new mouse model

We found that in contrast to (BXSB x NZB) F(1) female mice that spontaneously develop severe systemic lupus erythematosus (SLE), male (BXSB x NZB) F(1) mice are not prone to SLE, but instead develop seronegative ankylosing enthesitis in ankle/tarsal joints only when caged in groups, with the incidence reaching 83% at 7 months of age. This ankylosis is microscopically characterized by a marked proliferation of fibroblast-like cells positive for bone morphogenetic protein (BMP)-2 in association with heterotropic formation of cartilages and bones in hyperplastic entheseal tissues and subsequent fusion of tarsal bones. Elevated potentials of popliteal lymph node T cells producing interleukin (IL)-17 and interferon (IFN)-gamma were significantly associated with joint ankylosis, suggesting the involvement of these cytokines in effector phase mechanisms of the disease, including up-regulated BMP signaling pathways. There was no difference in serum autoantibody levels between affected and unaffected mice. Parental BXSB and NZB strains of both sexes did not develop the disease even when caged in groups, indicating that the disease develops under the control of susceptibility genes derived from both parental strains. These results indicate that (BXSB x NZB) F(1) male mice are a suitable model for clarifying genetic, environmental and molecular mechanisms underlying ankylosing enthesitis and related diseases.

A genetic locus controlling aging-sensitive regression of B lymphopoiesis in an autoimmune-prone MRL/lpr strain of mice

Aging readily affects immune system under the influence of environmental and/or intrinsic factors while accelerating the development of various immune disorders including autoimmune diseases. Little is known about molecular and cellular mechanisms connecting between immune senescence and development of autoimmune diseases. Here, we first show strain-specific and aging-sensitive onset of B-cell abnormality in a lupus-prone MRL/Mp.Fas(lpr) (MRL/lpr) strain of mice. This abnormality was characterized by the regression of B lymphopoiesis in the bone marrow of this strain. We next examined the association between the B-cell regression and onset of autoimmune diseases in aged (MRL/lpr x C3H/He.Fas(lpr)) F2 mice, in which pathologic phenotypes, such as glomerulonephritis, vasculitis, sialoadenitis and arthritis, variously developed. We also searched whole genome to identify genetic loci linked to the B-cell regression by using the same F2 mice. The B-cell regression manifested in the spleen of F2 mice was retrospectively evaluated by reverse transcriptase-based PCR quantification. The results demonstrated that the onset of autoimmune diseases in the F2 mice was not associated with the aging-sensitive B-cell regression. The genetic study identified a significant locus responsible for the B-cell regression in the vicinity of D5Mit233 (29 cM). This is first evidence for the presence of a genetic locus that affects B lymphopoiesis in an aging-sensitive manner.

A non-major histocompatibility locus determines tissue specificity in the pathogenic process underlying synovial proliferation in a mouse arthropathy model

BACKGROUND

The incidence and characteristics of spontaneous ankylosis in the ankle of specific F(1) mice descended from two Fas-deficient strains were reported. Here the coincidence of synovial proliferation and ankylosis in the descendent F(2) mice is reported.

AIM

To clarify whether the two distinct manifestations are genetically different.

METHODS

An arthropathic group of mice (MCF(2)) were bred by intercrossing MRL/Mp.Fas(lpr)-sap(-)/sap(-) and C3H/He.Fas(lpr) mice. All mice were killed by bleeding under anaesthesia when they were 6 months old. Pathological grades for synovial proliferation were determined by microscopical examination. To obtain a linkage locus, the whole genome of male MCF(2) mice was scanned by using 73 microsatellite markers.

RESULTS

Synovial proliferation was equally observed in male and female MCF(2) mice. No correlation was observed between the grades of synovial proliferation and the ankylosis occurring in the MCF(2) mice. A suggestive susceptibility locus was shown in the middle of chromosome 11. This locus was an MRL allele with a recessive inheritance mode.

CONCLUSION

The pathogenic mechanisms of synovial proliferation and ankylosis are genetically different. The present locus is overlapped with some loci associated with rheumatoid arthritis and with others associated with experimental arthritides.