Ivan Molano

Complement component C3 is not required for full expression of immune complex glomerulonephritis in MRL/lpr mice.

Complement activation and tissue deposition of complement fragments occur during disease progression in lupus nephritis. Genetic deficiency of some complement components (e.g., Factor B) and infusion of complement inhibitors (e.g., Crry, anti-C5 Ab) protect against inflammatory renal disease. Paradoxically, genetic deficiencies of early components of the classical complement pathway (e.g., C1q, C4, and C2) are associated with an increased incidence of lupus in humans and lupus-like disease in murine knockout strains. Complement protein C3 is the converging point for activation of all three complement pathways and thus plays a critical role in biologic processes mediated by complement activation. To define the role of C3 in lupus nephritis, mice rendered C3 deficient by targeted deletion were backcrossed for eight generations to MRL/lpr mice, a mouse strain that spontaneously develops lupus-like disease. We derived homozygous knockout (C3−/−), heterozygous (C3+/−), and C3 wild-type (C3+/+) MRL/lpr mice. Serum levels of autoantibodies and circulating immune complexes were similar among the three groups. However, there was earlier and significantly greater albuminuria in the C3−/− mice compared with the other two groups. Glomerular IgG deposition was also significantly greater in the C3−/− mice than in the other two groups, although overall pathologic renal scores were similar. These results indicate that C3 and/or activation of C3 is not required for full expression of immune complex renal disease in MRL/lpr mice and may in fact play a beneficial role via clearance of immune complexes.

Decreased expression of the Ets family transcription factor Fli-1 markedly prolongs survival and significantly reduces renal disease in MRL/lpr mice

Increased Fli-1 mRNA is present in PBLs from systemic lupus erythematosus patients, and transgenic overexpression of Fli-1 in normal mice leads to a lupus-like disease. We report in this study that MRL/lpr mice, an animal model of systemic lupus erythematosus, have increased splenic expression of Fli-1 protein compared with BALB/c mice. Using mice with targeted gene disruption, we examined the effect of reduced Fli-1 expression on disease development in MRL/lpr mice. Complete knockout of Fli-1 is lethal in utero. Fli-1 protein expression in heterozygous MRL/lpr (Fli-1+/−) mice was reduced by 50% compared with wild-type MRL/lpr (Fli-1+/+) mice. Fli-1+/− MRL/lpr mice had significantly decreased serum levels of total IgG and anti-dsDNA Abs as disease progressed. Fli-1+/− MRL/lpr mice had significantly increased splenic CD8+ and naive T cells compared with Fli-1+/+ MRL/lpr mice. Both in vivo and in vitro production of MCP-1 were significantly decreased in Fli-1+/− MRL/lpr mice. The Fli-1+/− mice had markedly decreased proteinuria and significantly lower pathologic renal scores. At 48 wk of age, survival was significantly increased in the Fli-1+/− MRL/lpr mice, as 100% of Fli-1+/− MRL/lpr mice were alive, in contrast to only 27% of Fli-1+/+ mice. These findings indicate that Fli-1 expression is important in lupus-like disease development, and that modulation of Fli-1 expression profoundly decreases renal disease and improves survival in MRL/lpr mice.

The Transcription Factor Fli-1 Modulates Marginal Zone and Follicular B Cell Development in Mice

Fli-1 belongs to the Ets transcription factor family and is expressed primarily in hematopoietic cells, including most cells active in immunity. To assess the role of Fli-1 in lymphocyte development in vivo, we generated mice that express a truncated Fli-1 protein, lacking the C-terminal transcriptional activation domain (Fli-1ΔCTA). Fli-1ΔCTA/Fli-1ΔCTA mice had significantly fewer splenic follicular B cells, and an increased number of transitional and marginal zone B cells, compared with wild-type controls. Bone marrow reconstitution studies demonstrated that this phenotype is the result of lymphocyte intrinsic effects. Expression of Igα and other genes implicated in B cell development, including Pax-5, E2A, and Egr-1, are reduced, while Id1 and Id2 are increased in Fli-1ΔCTA/Fli-1ΔCTA mice. Proliferation of B cells from Fli-1ΔCTA/Fli-1ΔCTA mice was diminished, although intracellular Ca2+ flux in B cells from Fli-1ΔCTA/Fli-1ΔCTA mice was similar to that of wild-type controls after anti-IgM stimulation. Immune responses and in vitro class switch recombination were also altered in Fli-1ΔCTA/Fli-1ΔCTA mice. Thus, Fli-1 modulates B cell development both centrally and peripherally, resulting in a significant impact on the in vivo immune response.

Differential effect of allogeneic versus syngeneic mesenchymal stem cell transplantation in MRL/lpr and (NZB/NZW)F1 mice.

MSC are being explored as a promising novel treatment for SLE. In this study, we: 1) assessed the differential effects of allogeneic versus syngeneic MSC transplantation on lupus-like disease, 2) explored the mechanisms by which MSC modulate disease, and 3) investigated whether lupus-derived-MSC have intrinsic immunomodulatory defects. We showed that in MRL/lpr mice and (NZB/NZW)F1 mice, both B6-MSC and lupus-MSC from young mice ameliorated SLE-like disease and reduced splenic CD3+CD4+ T lymphocytes and CD19+CD21+ B lymphocytes. However, lupus-MSC from older (NZB/NZW)F1 mice did not reduce spleen weights, glomerular IgG deposits, renal pathology, interstitial inflammation, CD3+CD4+ T lymphocytes or CD19+CD21+ B lymphocytes significantly. Thus MSC transplantation ameliorates SLE-like disease partly through decreasing CD4+ T cell and naïve mature B cell numbers. Allogeneic MSC may be preferred over syngeneic lupus-derived-MSC given the decreased overall effectiveness of post-lupus-derived-MSC, which appears partially due to disease and not exclusively intrinsic defects in the MSC themselves.

Differential Efficacy of Human Mesenchymal Stem Cells Based on Source of Origin

Mesenchymal stem cells (MSCs) are useful in tissue repair but also possess immunomodulatory properties. Murine and uncontrolled human trials suggest efficacy of MSCs in treating lupus. Autologous cells are preferable; however, recent studies suggest that lupus-derived MSCs lack efficacy in treating disease. Thus, the optimum derivation of MSCs for use in lupus is unknown. It is also unknown which in vitro assays of MSC function predict in vivo efficacy. The objectives for this study were to provide insight into the optimum source of MSCs and to identify in vitro assays that predict in vivo efficacy. We derived MSCs from four umbilical cords, four healthy bone marrows (BMs), and four lupus BMs. In diseased MRL/lpr mice, MSCs from healthy BM and umbilical cords significantly decreased renal disease, whereas lupus BM MSCs only delayed disease. Current in vitro assays did not differentiate efficacy of the different MSCs. However, differences in MSC efficacy were observed in B cell proliferation assays. Our results suggest that autologous MSCs from lupus patients are not effective in treating disease. Furthermore, standard in vitro assays for MSC licensing are not predictive of in vivo efficacy, whereas inhibiting B cell proliferation appears to differentiate effective MSCs from ineffective MSCs.

Impact of Fli-1 transcription factor on autoantibody and lupus nephritis in NZM2410 mice

The transcription factor Fli‐1 is implicated in the pathogenesis of both murine and human lupus. Increased levels of Fli‐1 mRNA were present in the peripheral blood lymphocytes from lupus patients; furthermore, transgenic overexpression of Fli‐1 in normal mice resulted in the development of a lupus‐like disease. Lupus nephritis is a major cause of death in both lupus patients as well as in animal models. In this study, we generated Fli‐1 heterozygous knockout (Fli‐1+/‐) NZM2410 mice (of which the wild‐type is a widely used lupus murine model) that expressed decreased levels of Fli‐1 and investigated the impact of Fli‐1 expression on lupus nephritis development and survival. Ninety‐three per cent of the Fli‐1+/− NZM2410 mice survived to the age of 52 weeks compared to only 35% of wild‐type NZM2410 mice. Autoantibodies, including anti‐dsDNA and anti‐glomerular basement antigen, in Fli‐1+/− NZM2410 mice were statistically significantly lower when compared to wild‐type NZM2410 mice at the ages of 30 and 34 weeks. Total B cell and activated B cell populations in the spleens from Fli‐1+/− NZM2410 mice were decreased significantly compared to wild‐type NZM2410 mice. Fli‐1+/− NZM2410 mice also had remarkably diminished proteinuria and decreased renal pathological scores when compared with wild‐type NZM2410 mice. Expression of early growth response 1 (Egr‐1) was decreased significantly in the kidneys from Fli‐1+/− NZM2410 mice when compared to wild‐type littermates. Our data indicate that expression of Fli‐1 plays an important role in lupus disease development in NZM2410 mice.

Effect of genetic deficiency of terminal deoxynucleotidyl transferase on autoantibody production and renal disease in MRL/lpr mice

Terminal deoxynucleotidyl transferase (TdT) places non-template-coded nucleotides (N additions) in the VH CDR3 of T cell receptors and immunoglobulins. Amino acids coded for by N additions are important in autoantibody binding of dsDNA in lupus. We hypothesized that a genetic lack of TdT would modulate disease in lupus-prone mice. To test this hypothesis, we derived TdT-deficient MRL/lpr mice. Serum levels of anti-dsDNA antibodies and anti-dsDNA producing splenocytes were significantly lower in the TdT(-) versus TdT(+) littermates. Albuminuria, glomerular IgG deposition, and pathologic renal disease were significantly reduced in the TdT(-) mice. Sequence analysis of anti-dsDNA hybridomas derived from TdT(-) mice revealed a lack of N additions, short VH CDR3 segments, yet the presence of VH CDR3 arginines. Thus, the genetic absence of TdT reduces autoantibody production and clinical disease in MRL/lpr mice, confirming the importance of N additions in the autoimmune response in these mice.

Decreased expression of Fli-1 in bone marrow-derived haematopoietic cells significantly affects disease development in Murphy Roths Large/lymphoproliferation (MRL/lpr) mice

The transcription factor Fli‐1 is implicated in the pathogenesis of both murine and human lupus. Decreased expression of Fli‐1 in heterozygous (Fli‐1+/−) Murphy Roths Large (MRL)/lpr mice resulted in significantly lower kidney pathological scores and markedly increased survival. In this study, bone marrow (BM) transplantation was used to investigate the role of decreased expression of Fli‐1 in haematopoietic versus non‐haematopoietic cell lineages in autoimmune disease development. Wild‐type (WT) MRL/lpr that received BM from Fli‐1+/− MRL/lpr mice had statistically significantly lower autoantibodies, less proteinuria, reduced renal disease and prolonged survival compared to WT MRL/lpr mice that received BM from WT MRL/lpr mice. Although not statistically significant, Fli‐1+/− MRL/lpr mice that received BM from WT MRL/lpr mice also had lower autoantibodies and improved survival compared to WT MRL/lpr mice that received BM from WT MRL/lpr mice. Our data indicate that expression of Fli‐1 in haematopoietic cell lineages has a significant effect on disease development in MRL/lpr mice.

FLI1 Levels Impact CXCR3 Expression and Renal Infiltration of T Cells and Renal Glycosphingolipid Metabolism in the MRL/lpr Lupus Mouse Strain

The ETS factor Friend leukemia virus integration 1 (FLI1) is a key modulator of lupus disease expression. Overexpressing FLI1 in healthy mice results in the development of an autoimmune kidney disease similar to that observed in lupus. Lowering the global levels of FLI1 in two lupus strains (Fli1+/−) significantly improved kidney disease and prolonged survival. T cells from MRL/lpr Fli1+/− lupus mice have reduced activation and IL-4 production, neuraminidase 1 expression, and the levels of the glycosphingolipid lactosylceramide. In this study, we demonstrate that MRL/lpr Fli1+/− mice have significantly decreased renal neuraminidase 1 and lactosylceramide levels. This corresponds with a significant decrease in the number of total CD3+ cells, as well as CD4+ and CD44+CD62L− T cell subsets in the kidney of MRL/lpr Fli1+/− mice compared with the Fli1+/+ nephritic mice. We further demonstrate that the percentage of CXCR3+ T cells and Cxcr3 message levels in T cells are significantly decreased and correspond with a decrease in renal CXCR3+ cells and in Cxcl9 and Cxcl10 expression in the MRL/lpr Fli1+/− compared with the Fli1+/+ nephritic mice. Our results suggest that reducing the levels of FLI1 in MRL/lpr mice may be protective against development of nephritis in part through downregulation of CXCR3, reducing renal T cell infiltration and glycosphingolipid levels.