Systemic autoimmune abnormalities alter the morphology of mucosa-associated lymphoid tissues in the rectum of MRL/MpJ-Faslpr/lpr mice

Systemic autoimmune diseases (ADs) might affect the morphology and function of gut-associated lymphoid tissue (LTs) indirectly; however, their exact relationship remains unclear. Therefore, we investigated mouse LTs in the anorectal canal and morphologically compared them between MRL/MpJ-Fas+/+ and MRL/MpJ-Faslpr/lpr mice. LT aggregations, also known as rectal mucosa-associated lymphoid tissues (RMALTs), were exclusively seen in the lamina propria and submucosa of the rectum. The mean size and number of the LT aggregations both significantly increased in MRL/MpJ-Faslpr/lpr mice compared to those in MRL/MpJ-Fas+/+ mice. The distance from the anorectal junction to the first LT aggregate was significantly shorter in MRL/MpJ-Faslpr/lpr mice than that in MRL/MpJ-Fas+/+ mice. Immunostaining revealed that the RMALTs included CD3+,CD4+, and CD8+ T cells; B220+ B cells; IBA1+ macrophages; Ki67+ proliferative cells; and PNAd+ high-endothelial venules (HEVs). The numbers of macrophages, proliferative cells, CD4+ T cells, CD8+ T cells, and HEVs were significantly increased in MRL/MpJ-Faslpr/lpr mice compared to those in MRL/MpJ mice. Furthermore, the gene expression levels of chemokines (Cxcl9 and Cxcl13) and their corresponding receptors (Cxcr3 and Cxcr5) were significantly higher in MRL/MpJ-Faslpr/lpr mice than those in MRL/MpJ-Fas+/+ mice. Although the morphology of rectal epithelium was comparable between the strains, M cell number was significantly higher in MRL/MpJ-Faslpr/lpr mice than in MRL/MpJ-Fas+/+ mice. Thus, ADs could alter RMALT morphology, and quantitative changes in T-cell subsets, proliferative cells, macrophages, HEVs, chemokine expression, and M cells could affect their cell composition and development.

Effects of autoimmune abnormalities on skeletal muscle regeneration after needle puncture in mice

Regeneration of injured skeletal muscles is supported by the activation of satellite cells, and excessive traumatic injuries may trigger abnormal processes, such as fibrosis. Because the participation of immune cells is crucial during skeletal muscle repair, systemic autoimmune diseases impair their regeneration. This study focused on a traumatic injury by injection and investigated the effect of autoimmune diseases on skeletal muscle regeneration. Male mice of MRL/MpJ-Faslpr/lpr and MRL/MpJ (6-7 months old) were used for autoimmune disease and healthy groups. The abdominal walls punctured by a needle were histologically analyzed at 1, 3, and 8 days postinjection. In both groups, injured skeletal muscle tissues showed necrosis and inflammatory cell infiltrations on day 1, increased cell density at 3 days, and regenerative myotubes with central nuclei without fibrosis at 8 days. Gr-1+ neutrophils at injured skeletal muscle were abundant at 1 day, and then substantially decreased starting from 3 days in both groups. The number of CD3+ T cells was remarkably higher in MRL/MpJ-Faslpr/lpr than that in MRL/MpJ at 1 day, and a similar tendency was observed in B220+ B cells. The numbers of IBA1+ macrophages and bromodeoxyuridine-incorporating cells tended to be higher at 3 days, and those of the latter, mainly proliferating paired-box-7+ satellite cells, showed significance at other time points and negatively correlated with the autoimmune disease indices, such as spleen weights or serum autoantibody level. Thus, this result suggested that injured skeletal muscle by minor trauma is normally regenerated regardless of the effects of autoimmune diseases, although lymphocyte infiltrations during these processes were more severe in MRL/MpJ-Faslpr/lpr.

Ameliorated Renal Pathological Feature in MRL/MpJ-Faslpr/lpr Background Interleukin-36 Receptor-Deficient Mice

Systemic autoimmune diseases frequently induce lupus nephritis, causing altered balance and expression of interleukin 36 receptor (IL-36R) ligands, including agonists (IL-36α, β, γ) and antagonists (IL-36Ra, IL-38), in kidneys. Here, we established and analyzed a mouse model of lupus nephritis, MRL/MpJ-Faslpr/lpr with IL-36R-knockout (KO), compared to wild-type (WT) mice. In both genotypes, indices for immune abnormalities and renal functions were comparable, although female WT mice showed higher serum autoantibody levels than males. IL-36R ligand expression did not differ significantly between genotypes at the mRNA level or in IL-36α and IL-38 scores. However, glomerular lesions, especially mesangial matrix expansion, were significantly ameliorated in both sexes of IL-36R-KO mice compared to WT mice. Cell infiltration into the tubulointerstitium with the development of tertiary lymphoid structures was comparable between genotypes. However, the positive correlation with the IL-36α score in WT mice was not evident in IL-36R-KO mice. Fibrosis was less in female IL-36R-KO mice than in WT mice. Importantly, some IL-36α+ nuclei co-localized with acetylated lysine and GCN5 histone acetyltransferase, in both genotypes. Therefore, IL-36R ligands, especially IL-36α, contribute to the progression of renal pathology in lupus nephritis via IL-36R-dependent and IL-36R-independent pathways.