Indispensable roles of OX40L-derived signal and epistatic genetic effect in immune-mediated pathogenesis of spontaneous pulmonary hypertension

<p>Abstract</p> <p>Background</p> <p>Pulmonary hypertension (PH) refers to a spectrum of diseases with elevated pulmonary artery pressure. Pulmonary arterial hypertension (PAH) is a disease category that clinically presents with severe PH and that is histopathologically characterized by the occlusion of pulmonary arterioles, medial muscular hypertrophy, and/or intimal fibrosis. PAH occurs with a secondary as well as a primary onset. Secondary PAH is known to be complicated with immunological disorders. The aim of the present study is to histopathologically and genetically characterize a new animal model of PAH and clarify the role of OX40 ligand in the pathogenesis of PAH.</p> <p>Results</p> <p>Spontaneous onset of PAH was stably identified in mice with immune abnormality because of overexpression of the tumor necrosis factor (TNF) family molecule OX40 ligand (OX40L). Histopathological and physical examinations revealed the onset of PAH-like disorders in the C57BL/6 (B6) strain of OX40L transgenic mice (B6.TgL). Comparative analysis performed using different strains of transgenic mice showed that this onset depends on the presence of OX40L in the B6 genetic background. Genetic analyses demonstrated a susceptibility locus of a B6 allele to this onset on chromosome 5. Immunological analyses revealed that the excessive OX40 signals in TgL mice attenuates expansion of regulatory T cells the B6 genetic background, suggesting an impact of the B6 genetic background on the differentiation of regulatory T cells.</p> <p>Conclusion</p> <p>Present findings suggest a role for the OX40L-derived immune response and epistatic genetic effect in immune-mediated pathogenesis of PAH.</p

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