Myeloid Differentiation Factor 88–Silenced Bone Marrow–Derived Dendritic Cells Exhibit Enhanced Tolerogenicity in Intestinal Transplantation in Rats

Interleukin-4 affects the mature phenotype and function of rat bone marrow-derived dendritic cells

Granulocyte macrophage‑colony stimulating factor (GM‑CSF), and GM‑CSF plus interleukin‑4 (GM‑CSF + IL‑4) are two commonly‑used cytokine therapies for the generation of bone marrow‑derived dendritic cells (DCs). However, the mechanisms underlying IL‑4 involvement in DC generation and maturation remain unclear. In order to investigate the effect of IL‑4 on DC generation, DCs from rat bone marrow progenitors were generated using GM‑CSF, with and without IL‑4. GM‑CSF + IL‑4 DCs exhibited more mature phenotypes, and the levels of naïve allogeneic T cell stimulation were greater compared with GM‑CSF DCs. Phosphorylated signal transducer and activator of transcription 6 (p‑STAT6), the active form of STAT6, was expressed in GM‑CSF + IL‑4 DCs but not in GM‑CSF DCs. The present study demonstrated that IL‑4 influences DC morphology and immune function, and that this process may be associated with the activation of STAT6.

Adoptive infusion of tolerance dendritic cells prolongs survival of small intestine allografts in rats: systematic review and meta-analysis

BACKGROUND

Postoperative infections and rejection are the main limiting factors of small intestine allograft survival. In this study, we performed a systematic review and meta-analysis to review rat small intestine allograft survival following infusion of tolerance dendritic cells (Tol-DCs) induced by different methods.

METHODS

Relevant publications were searched from PubMed database and EMbase database. Meta-analysis was performed using RevMan 5.0 software. We chose allograft survival, mixed leukocyte reaction, Th1/Th2 differentiation, Treg induction, and cytotoxic T lymphocyte activity as the outcomes by which to examine possible mechanisms that promote survival.

RESULTS

Eleven suitable articles were identified and assessed. Tol-DCs induced by four methods all prolonged allograft survival. The difference in survival time between the Tol-DC group and the control group was indicated by SMD as follows: drug intervention (SMD = 3.02, 95% CI 1.16 to 4.88, P = 0.001), gene modification (SMD = 2.43, 95% CI 1.77 to 3.10, P < 0.00001), imDC (SMD = 1.76, 95% CI 0.90 to 2.62, P < 0.0001), cytokine induction (SMD = 1.68, 95% CI 0.40 to 2.96, P = 0.01). Tol-DCs were also synergistic with immunosuppressive drugs or costimulation inhibitors, but no immune tolerance was observed. A single-dose intravenous injection of 5×10(6) to 6×10(6) Tol-DCs showed the highest allograft survival. Possible mechanisms included donor-specific T-cell hyporesponsiveness and Th2 differentiation.

CONCLUSIONS

Our results demonstrated that Tol-DCs induced by four methods prolong rat small intestine allograft survival. Intravenous infusion of 5×10(6) to 6×10(6) Tol-DCs was the optimum dose in rat small intestine transplantation. Immunosuppressive or costimulatory blockade was synergistic with Tol-DC on graft survival. Additional high-quality studies with larger sample sizes are needed to better investigate small intestinal graft longer term survival.

Dendritic cells play an essential role in transplantation responses via myeloid differentiation factor 88 signaling

BACKGROUND

DCs (dendritic cells), play an important role in allo-recognition, but there is no direct evidence that DCs trigger and control allo-responses. In this study, we investigated the role of DCs by using a self-created MyD88 (myeloid differentiation factor 88) inhibitor and a minor antigen-mismatched (HY-mismatched) skin transplantation model in mice.

METHODS

An HY-mismatched skin allograft model (BALB/c ♂ → BALB/c ♀) using MyD88-knockout mice was employed in this study. WT (Wild-type) BALB/c immature BMDCs (bone marrow dendritic cells) were co-cultured with or without TJ-M2010 in vitro for 12 hours before transfusion of DCs (2× 10(7)/mouse) into recipients of skin transplantations. Wild-type BALB/c BMDCs were stimulated by the TLR9 (Toll-like receptor 9) agonist, CpG (cytidine-phosphate-guanosine), in the presence of TJ-M2010 or not for 12 hours in vitro. Costimulatory molecules CD80/CD86 were analyzed by flow cytometry. WT C57BL/6 naïve T cells stained with CFSE (carboxyfluorescein diacetate succinimidyl ester) were co-cultured with WT BALB/c DCs for 3 days in the presence or absence of TJ-M2010. CD3(+)/CFSE(+) cells were analyzed by flow cytometry.

RESULTS

TJ-M2010 inhibited DC maturation and T cell proliferation. Permanent survival of the skin allografts was observed in MyD88 knockout (MyD88- KO) mice. However, skin allografts were rejected by MyD88-KO mice infused with wild-type (WT) DCs. More interestingly, after treating the WT DCs with TJ-M2010, the DC infusion could not reverse the tolerance to skin allografts.

CONCLUSION

This study provided evidence that DCs play an essential role in alloresponses.

Immunologic challenges in small bowel transplantation

Since the introduction of tacrolimus, small-bowel and multivisceral transplantion has increased to 100-200/year in the United States. The intestine carries more passenger lymphocytes than other organs, and bidirectional trafficking of lymphocytes and other immunocytes begins as soon as the vascular clamp is released. Because of ischemia-reperfusion injury and exposure to ligands for Toll-like receptors from the lumen, the innate immune system of the graft is activated, causing inflammation which must be brought under control by regulatory cells. Inclusion of the liver in the allograft favors graft acceptance, but the mechanism of this effect has not been determined. Anti-HLA and other anti-donor antibodies clearly play a major role in determining the long-term fate of the graft, as reflected in 5-year graft survival. Development of new (de novo) HLA antibodies and/or increases in their titers or function-especially the ability to bind C1q and activate complement increase the risk of graft loss. Monitoring antidonor antibody production and the use of new therapies including complement inhibitors will contribute to increasing success of SBT.

RNA interference for improving the outcome of islet transplantation

Islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still not common because a large number of transplanted islets get damaged by multiple challenges including instant blood mediated inflammatory reaction, hypoxia/reperfusion injury, inflammatory cytokines, and immune rejection. RNA interference (RNAi) is a novel strategy to selectively degrade target mRNA. The use of RNAi technologies to downregulate the expression of harmful genes has the potential to improve the outcome of islet transplantation. The aim of this review is to gain a thorough understanding of biological obstacles to islet transplantation and discuss how to overcome these barriers using different RNAi technologies. This eventually will help improve islet survival and function post transplantation. Chemically synthesized small interferring RNA (siRNA), vector based short hairpin RNA (shRNA), and their critical design elements (such as sequences, promoters, and backbone) are discussed. The application of combinatorial RNAi in islet transplantation is also discussed. Last but not the least, several delivery strategies for enhanced gene silencing are discussed, including chemical modification of siRNA, complex formation, bioconjugation, and viral vectors.