Deletion of Smad3 improves cardiac allograft rejection in mice

Macrophage-derived macrophage migration inhibitory factor mediates renal injury in anti-glomerular basement membrane glomerulonephritis

Macrophages are a rich source of macrophage migration inhibitory factor (MIF). It is well established that macrophages and MIF play a pathogenic role in anti-glomerular basement membrane crescentic glomerulonephritis (anti-GBM CGN). However, whether macrophages mediate anti-GBM CGN via MIF-dependent mechanism remains unexplored, which was investigated in this study by specifically deleting MIF from macrophages in MIFf/f-lysM-cre mice. We found that compared to anti-GBM CGN induced in MIFf/f control mice, conditional ablation of MIF in macrophages significantly suppressed anti-GBM CGN by inhibiting glomerular crescent formation and reducing serum creatinine and proteinuria while improving creatine clearance. Mechanistically, selective MIF depletion in macrophages largely inhibited renal macrophage and T cell recruitment, promoted the polarization of macrophage from M1 towards M2 via the CD74/NF-κB/p38MAPK-dependent mechanism. Unexpectedly, selective depletion of macrophage MIF also significantly promoted Treg while inhibiting Th1 and Th17 immune responses. In summary, MIF produced by macrophages plays a pathogenic role in anti-GBM CGN. Targeting macrophage-derived MIF may represent a novel and promising therapeutic approach for the treatment of immune-mediated kidney diseases.

Dissecting the immune discrepancies in mouse liver allograft tolerance and heart/kidney allograft rejection

The liver is the most tolerogenic of transplanted organs. However, the mechanisms underlying liver transplant tolerance are not well understood. The comparison between liver transplantation tolerance and heart/kidney transplantation rejection will deepen our understanding of tolerance and rejection in solid organs. Here, we built a mouse model of liver, heart and kidney allograft and performed single-cell RNA sequencing of 66,393 cells to describe the cell composition and immune cell interactions at the early stage of tolerance or rejection. We also performed bulk RNA-seq of mouse liver allografts from Day 7 to Day 60 post-transplantation to map the dynamic transcriptional variation in spontaneous tolerance. The transcriptome of lymphocytes and myeloid cells were characterized and compared in three types of organ allografts. Cell-cell interaction networks reveal the coordinated function of Kupffer cells, macrophages and their associated metabolic processes, including insulin receptor signalling and oxidative phosphorylation in tolerance induction. Cd11b+ dendritic cells (DCs) in liver allografts were found to inhibit cytotoxic T cells by secreting anti-inflammatory cytokines such as Il10. In summary, we profiled single-cell transcriptome analysis of mouse solid organ allografts. We characterized the immune microenvironment of mouse organ allografts in the acute rejection state (heart, kidney) and tolerance state (liver).

An Immune Atlas of T Cells in Transplant Rejection: Pathways and Therapeutic Opportunities

Short-term outcomes in allotransplantation are excellent due to technical and pharmacological advances; however, improvement in long-term outcomes has been limited. Recurrent episodes of acute cellular rejection, a primarily T cell-mediated response to transplanted tissue, have been implicated in the development of chronic allograft dysfunction and loss. Although it is well established that acute cellular rejection is primarily a CD4 + and CD8 + T cell mediated response, significant heterogeneity exists within these cell compartments. During immune responses, naïve CD4 + T cells are activated and subsequently differentiate into specific T helper subsets under the influence of the local cytokine milieu. These subsets have distinct phenotypic and functional characteristics, with reported differences in their contribution to rejection responses specifically. Of particular relevance are the regulatory subsets and their potential to promote tolerance of allografts. Unraveling the specific contributions of these cell subsets in the context of transplantation is complex, but may reveal new avenues of therapeutic intervention for the prevention of rejection.

Dissecting the regulatory network of transcription factors in T cell phenotype/functioning during GVHD and GVT

Transcription factors play a major role in regulation and orchestration of immune responses. The immunological context of the response can alter the regulatory networks required for proper functioning. While these networks have been well-studied in canonical immune contexts like infection, the transcription factor landscape during alloactivation remains unclear. This review addresses how transcription factors contribute to the functioning of mature alloactivated T cells. This review will also examine how these factors form a regulatory network to control alloresponses, with a focus specifically on those factors expressed by and controlling activity of T cells of the various subsets involved in graft-versus-host disease (GVHD) and graft-versus-tumor (GVT) responses.

Targeted galectin-7 inhibition with ultrasound microbubble targeted gene therapy as a sole therapy to prevent acute rejection following heart transplantation in a Rodent model

BACKGROUND

Despite significant advances in transplantation, acute cellular rejection (AR) remains a major obstacle that is most prevalent in the first months post heart transplantation (HT). Current treatments require high doses of immunosuppressive drugs followed by maintenance therapies that have systemic side effects including early infection. In this study, we attempted to prevent AR with a myocardial-targeted galectin-7-siRNA delivery method using cationic microbubbles (CMBs) combined with ultrasound targeted microbubble destruction (UTMD) to create local immunosuppression in a rat abdominal heterotopic heart transplantation acute rejection model.

METHODS AND RESULTS

Galectin-7-siRNA (siGal-7) bound to CMBs were synthesized and effective ultrasound-targeted delivery of siGal-7 into target cells confirmed in vitro. Based on these observations, three transplant rat models were tested：①isograft (ISO); ② Allograft (ALLO) +UTMD; and ③ALLO + PBS. UTMD treatments were administered at 1, 3, 5, 7 days after HT. Galectin 7 expression was reduced by 50% compared to ALLO + PBS (p < 0.005), and this was associated with significant reductions in both galectin 7 and Interleukin-2 protein levels (p < 0.001). The ALLO + UTMD group had Grade II or less inflammatory infiltration and myocyte damage in 11/12 rats using International Society For Heart and Lung Transplantation grading, compared to 0/12 rats with this grading in the ALLO + PBS group at 10 days post HT (p < 0.001).

CONCLUSIONS

Ultrasound-targeted galectin-7-siRNA knockdown with UTMD can prevent acute cellular rejection in the early period after allograft heart transplantation without the need for systemic immunosuppression.

KEY WORDS

Microbubble, Acute Rejection, Heart Transplantation, Galectin-7, RNA.

[Rapamycin alleviates inflammation by up-regulating TGF-β/Smad signaling in a mouse model of autoimmune encephalomyelitis]

OBJECTIVE

To evaluate the efficacy of rapmycin for treatment of experimental autoimmune encephalomyelitis (EAE) in mice and explore the underlying mechanism.

METHODS

An EAE model was established in C57BL/6 mice. After immunization, the mice were divided into model group and rapamycin groups treated daily with low-dose (0.3 mg/kg) or high-dose (1 mg/kg) rapamycin. The clinical scores of the mice were observed using Knoz score, the infiltration of IL-17 cells in the central nervous system (CNS) was determined using immunohistochemistry; the differentiation of peripheral Treg cells was analyzed using flow cytometry, and the changes in the levels of cytokines were detected with ELISA; the changes in the expressions of p-Smad2 and p- smad3 were investigated using Western blotting.

RESULTS

High-dose rapamycin significantly improved the neurological deficits scores of EAE mice. In high-dose rapamycin group, the scores in the onset stage, peak stage and remission stage were 0.14±0.38, 0.43±1.13 and 0.14±0.37, respectively, as compared with 1.14±0.69, 2.14±1.06 and 2.2±0.75 in the model group. The infiltration of inflammatory IL-17 cells was significantly lower in high-dose rapamycin group than in the model group (43±1.83 vs 153.5±7.02). High-dose rapamycin obviously inhibited the production of IL-12, IFN-γ, IL-17 and IL-23 and induced the anti-inflammatory cytokines IL-10 and TGF-β. The percentage of Treg in CD4+ T cells was significantly higher in high- dose rapamycin group than in the model group (10.17 ± 0.68 vs 3.52 ± 0.32). In the in vitro experiment, combined treatments of the lymphocytes isolated from the mice with rapamycin and TGF-β induced a significant increase in the number of Treg cells (13.66±1.89) compared with the treatment with rapamycin (6.23±0.80) or TGF-β (4.87±0.85) alone. Rapamycin also obviously up-regulated the expression of p-Smad2 and p-Smad3 in the lymphocytes.

CONCLUSIONS

Rapamycin can promote the differentiation of Treg cells by up-regulating the expression of p-Smad2 and p-smad3 to improve neurological deficits in mice with EAE.

The Regulatory T-cell Transcription Factor Foxp3 Protects against Crescentic Glomerulonephritis

Regulatory T cells (Tregs) have been shown to play a protective role in glomerulonephritis (GN) and Foxp3 is a master transcription factor in Treg development. In this study, we examined the functional role and mechanisms of Foxp3 in a mouse model of accelerated anti-glomerular basement membrane (anti-GBM) GN induced in antigen-primed Foxp3 transgenic (Tg) mice. Compared with littermate of wildtype (WT) mice in which induced severe crescentic GN developed with progressive renal dysfunction, Foxp3 Tg mice had reduced crescent formation, urinary protein excretion, plasma creatinine and decline in creatinine clearance. The protective role of Foxp3 in crescentic GN was associated with a markedly suppressed expression of proinflammatory interleukin-1 beta (IL-1β), tumour necrosis factor-alpha (TNF-α) and monocyte chemoattractant protein 1 (MCP-1), and diminished infiltration of the kidneys by CD3⁺ T cells and F4/80⁺ macrophages. Moreover, overexpression of Foxp3 resulted in a significant increase in CD4⁺ Foxp3⁺ Tregs systemically and in the diseased kidneys, thereby blunting Th1, Th2, and Th17 responses systemically and in the kidneys. In conclusion, Foxp3 protects against kidney injury in crescentic GN through enhancement of Treg numbers and function, and suppression of Th1, Th2 and Th17 immune responses at the systemic and local tissue levels.