Prolonged skin grafts survival time by IFN-γ in allogeneic skin transplantation model during acute rejection through IFN-γ/STAT3/IDO pathway in epidermal layer

Upregulation of IDO gene expression reduces the immunogenicity of epidermal cells and strengthens the immune protection of epidermal cells during transplantation treatment of wounds

BACKGROUND

Epidermal cell transplantation is a feasible treatment option for large wounds; however, sources of autologous epidermal cells are often limited. Allogeneic epidermal cells can be cultured conveniently; however, related immune rejection needs to be addressed. Herein, we hypothesized that the immunogenicity of epidermal cells with high indoleamine 2,3-dioxygenase (IDO) expression may be reduced by gene transfection.

METHODS/RESULTS

To test this hypothesis, we obtained stable transfectants by transfecting epidermal stem cells with a lentiviral vector encoding the IDO gene and screening them for puromycin resistance (a marker for successful transfection). The phenotype tested using cell counting kit -8 and Transwell assays confirmed that IDO-transfected epidermal cells maintained their characteristics. Co-culture of IDO-transfected epidermal cells with allogeneic CD4+ T cells in vitro showed that the upregulation of IDO expression in epidermal cells inhibited the proliferation of CD4+ T cells (P < 0.001, P < 0.001, and P < 0.001, respectively) and promoted their apoptosis (P = 0.00028, P = 0.0006, and P = 0.00247, respectively) and transformation into functional regulatory T cells (Tregs) (P = 0.0051, P = 0.0132, and P = 0.0248, respectively) compared with Con, NC, and 1-MT groups. The increased proportion of Tregs may be related to the overexpression of IDO, which promoted the expression of transforming growth factor beta (TGF-β) (P = 0.0001, P = 0.0013, and, P = 0.0009) and interleukin (IL) 10 (IL-10) (P = 0.0062, P = 0.0058, and P = 0.0119) while inhibited the expression of IL-2 (P = 0.0012, P = 0.0126, and P = 0.0066). We further verified these effects in vivo as transplanted IDO-transfected epidermal stem cells were effective in treating wounds in mice. On days 5 and 7, wounds treated with IDO cells healed faster than those in the other groups (day 5: P = 0.012 and P = 0.0136; day 7: P = 0.0242 and P = 0.0187, respectively), whereas this effect was significantly inhibited by 1-methyltryptophan (1-MT) (day 5: P = 0.0303; day 7: P = 0.0105). Immunofluorescence staining detected IDO and CD4+ Foxp3+ Tregs in the transplanted wounds, which may promote Foxp3+ Tregs in the wound tissue (day 5: P < 0.0001, P < 0.0001, and P < 0.0001; day 7: P < 0.0001, P < 0.0001, and P < 0.0001), respectively) and decrease CD4+ T cells (day 5: P < 0.0001, P < 0.0001, and P < 0.0001; day 7: P < 0.0001, P < 0.0001, and P < 0.0001).

CONCLUSION

Our results suggest that the upregulation of IDO expression in epidermal stem cells can reduce their immunogenicity by promoting Tregs, thus inducing the immune protection of epidermal stem cells.

Multiple Injections of Adipose-Derived Stem Cells Improve Graft Survival in Human-to-Rat Skin Xenotransplantation through Immune Modulation

BACKGROUND

Adipose-derived stem cells (ADSCs) exert immunomodulatory effects in the treatment of transplant rejection. This study aimed to evaluate the effects of ADSCs on the skin graft survival in a human-to-rat xenograft transplantation model and to compare single and multiple injections of ADSCs.

METHODS

Full-thickness human skin xenografts were transplanted into the backs of Sprague-Dawley rats. The rats were injected subcutaneously on postoperative days 0, 3, and 5. The injections were as follows: triple injections of phosphate-buffered saline (PBS group), a single injection of ADSCs and double injections of PBS (ADSC × 1 group), and triple injections of ADSCs (ADSC × 3 group). The immunomodulatory effects of ADSCs on human skin xenografts were assessed.

RESULTS

Triple injections of ADSCs considerably delayed cell-mediated xenograft rejection compared with the PBS and ADSC × 1 groups. The vascularization and collagen type 1-3 ratios in the ADSC × 3 group were significantly higher than those in the other groups. In addition, intragraft infiltration of CD3-, CD4-, CD8-, and CD68-positive cells was reduced in the ADSC × 3 group. Furthermore, in the ADSC × 3 group, the expression levels of proinflammatory cytokine interferon-gamma (IFN-γ) were decreased and immunosuppressive prostaglandin E synthase (PGES) was increased in the xenograft and lymph node samples.

CONCLUSION

This study presented that triple injections of ADSCs appeared to be superior to a single injection in suppressing cell-mediated xenograft rejection. The immunomodulatory effects of ADSCs are associated with the downregulation of IFN-γ and upregulation of PGES in skin xenografts and lymph nodes.

An integrated cytokine and kynurenine network as the basis of neuroimmune communication

Two of the molecular families closely associated with mediating communication between the brain and immune system are cytokines and the kynurenine metabolites of tryptophan. Both groups regulate neuron and glial activity in the central nervous system (CNS) and leukocyte function in the immune system, although neither group alone completely explains neuroimmune function, disease occurrence or severity. This essay suggests that the two families perform complementary functions generating an integrated network. The kynurenine pathway determines overall neuronal excitability and plasticity by modulating glutamate receptors and GPR35 activity across the CNS, and regulates general features of immune cell status, surveillance and tolerance which often involves the Aryl Hydrocarbon Receptor (AHR). Equally, cytokines and chemokines define and regulate specific populations of neurons, glia or immune system leukocytes, generating more specific responses within restricted CNS regions or leukocyte populations. In addition, as there is a much larger variety of these compounds, their homing properties enable the superimposition of dynamic variations of cell activity upon local, spatially limited, cell populations. This would in principle allow the targeting of potential treatments to restricted regions of the CNS. The proposed synergistic interface of 'tonic' kynurenine pathway affecting baseline activity and the superimposed 'phasic' cytokine system would constitute an integrated network explaining some features of neuroimmune communication. The concept would broaden the scope for the development of new treatments for disorders involving both the CNS and immune systems, with safer and more effective agents targeted to specific CNS regions.

D-MT prompts the anti-tumor effect of oxaliplatin by inhibiting IDO expression in a mouse model of colon cancer

Colon cancer is one of the most common malignant tumors in the digestive system. Although oxaliplatin, a chemotherapy drug, has been clinically used to treat colon cancer, its therapeutic effect is unsatisfactory. It has been proved that indoleamine dioxygenase 2,3 (IDO) is a tumor immunosuppressive factor for the immune response. Herein, an IDO inhibitor, D-MT (indoximod, 1-Methyl-D-tryptophan), was combined with oxaliplatin to treat colon cancer in mice. T cell infiltration in tumor tissues, the ratios of immune cells in the spleens, and the tumor growth and survival of the mice were detected and recorded. The results showed that the combination of oxaliplatin and D-MT significantly inhibited tumor growth and prolonged the survival of tumor-bearing mice. More importantly, the combination treatment increased the ratios of CD4⁺ T, CD8⁺ T and NK cells from the spleen in tumor-bearing mice, and prompted T cell infiltration in tumor tissues. This study provided a new therapeutic strategy for colon cancer treatment in the clinic, especially for patients with oxaliplatin resistance.

MiR-669b-3p regulates CD4+ T cell function by down-regulating indoleamine-2, 3-dioxygenase

OBJECTIVE

Acute rejection is a major cause of morbidity and mortality after solid organ transplantation. Therefore, optimizing treatment strategies and improving curative effect is urgent and necessary. Reliable biomarkers for acute rejection and the underlying molecular mechanisms remain to be determined.

METHODS

In this study, we established a mouse-to-mouse cardiac transplantation model and identified miR-669b-3p as a potential biomarker of acute rejection using a microRNA polymerase chain reaction (PCR)-based chip assay.

RESULTS

Further analyses showed that miR-669b-3p negatively regulated indoleamine-2,3-dioxygenase (IDO), a rate-limiting enzyme of tryptophan catabolism inhibiting T cell function. Using mixed lymphocyte reaction assay, we showed that miR-669b-3p increased proliferation stimulation index and inhibited apoptosis in CD4⁺ T cells. Moreover, miR-669b-3p regulated the expression of inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and Interleukin 10 (IL-10) and contributed to cytokine shift towards a Th2-dominant response.

CONCLUSION

Our results advance the current understanding of the immune regulatory function of miRNA and shed light on the role of miR-669b-3p in CD4⁺ T cells, suggesting that miR-669b-3p is a potential target for acute allograft rejection.

ECDI-fixed donor splenocytes prolong skin allograft survival by promoting M2 macrophage polarization and inducing regulatory T cells

Rejection is a common complication of allogeneic tissue transplantation. Fixation of splenocytes (SP) with 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide (ECDI) induces immune tolerance in recipients post-transplantation; however, the mechanism underlying this effect remains unclear. Here, we determined the mechanisms of ECDI-fixed donor SP (ECDI-SP) in inducing tolerance in skin allograft transplantation. C57BL/6-recipient mice that received Balb/c full-thickness skin transplants with two infusions of donor-derived ECDI-SP, along with rapamycin showed superior skin allograft survival and lower inflammatory cell infiltration than mice that received rapamycin-only treatment. In ECDI-SP-treated mice, the levels of anti-inflammatory cytokines such as interleukin (IL)-10 in sera were markedly increased, whereas the expression of inflammatory cytokines was significantly suppressed. Splenic macrophages were significantly polarized to the alternative activated macrophage (M2) phenotype, with expansion of CD4+Foxp3+ regulatory T cells (Tregs) in the spleen and draining lymph nodes. Allostimulatory activity of ECDI-SP in vitro and donor-specific ex vivo hyporesponsiveness were observed. C57BL/6 macrophages engulfed allogeneic Balb/c-derived ECDI-SP, polarized to the M2 phenotype, with pronounced cAMP response element-binding (CREB) protein phosphorylation. By facilitating increased IL-10 expression, ECDI-SP induced M2 polarization and Treg production, inhibiting effector T-cell proliferation. Thus, ECDI-SP modulates macrophage M2 polarization by increasing CREB phosphorylation and promoting Treg production to suppress allogeneic skin graft rejection.

Genomics meets immunity in pancreatic cancer: Current research and future directions for pancreatic adenocarcinoma immunotherapy

Pancreatic adenocarcinoma (PDAC) remains a formidable disease that needs improved therapeutic strategies. Even though immunotherapy has revolutionized treatment for various solid tumor types, it remains largely ineffective in treating individuals with PDAC. This review describes how the application of genome-wide analysis is revitalizing the field of PDAC immunotherapy. Major themes include new insights into the body’s immune response to the cancer, and key immunosuppressive elements that blunt that antitumor immunity. In particular, new evidence indicates that T cell-based antitumor immunity against PDAC is more common, and more easily generated, than previously thought. However, equally common are an array of cellular and molecular defenses employed by the tumor against those T cells. These discoveries have changed how current immunotherapies are deployed and have directed development of novel strategies to better treat this disease. Thus, the impact of genomic analysis has been two-fold: both in demonstrating the heterogeneity of immune targets and defenses in this disease, as well as providing a powerful tool for designing and identifying personalized therapies that exploit each tumor’s unique phenotype. Such personalized treatment combinations may be the key to developing successful immunotherapies for pancreatic adenocarcinoma.