PDL1Ig gene-loaded BMSCs Induce liver transplantation immune tolerance

Effect of HO-1-modified BMMSCs on immune function in liver transplantation

We examined whether haem oxygenase-1 (HO-1) could enhance the immunosuppressive effects of bone marrow mesenchymal stem cells (BMMSCs) on the rejection of transplanted liver allografts in rats. The animals were divided into three groups: the normal saline (NS) group, BMMSC group and HO-1/BMMSCs group. In vitro, the extraction, culture and HO-1 transfection of BMMSCs were performed. Mixed lymphocyte response (MLR) analysis of HO-1/BMMSCs efficacy was performed. The rejection model of orthotopic liver transplantation in rats was established when BMMSCs and HO-1/BMMSCs were transfused via the portal vein. To reduce research bias, we established an isogenic Liver transplantation model of (LEW → LEW) and (BN → BN), which can achieve tolerance. Changes in histopathology and liver function in the transplanted liver and changes in regulatory T cell (Tregs), natural killer (NK) cells and cytokines after transplantation were observed in the different groups. The severe acute rejection after liver transplantation on postoperative Day 10 was observed in the NS group. The BMMSC group showed strong protective effects against rejection within the first 10 days after transplantation, while HO-1/BMMSCs showed stronger effects on rejection than BMMSCs alone. In addition, the activity of natural killer (NK) cells decreased significantly, the levels of regulatory T cells (Tregs), interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) increased significantly and the levels of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-17 (IL-17), interleukin-23 (IL-23), tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) decreased significantly in the HO-1/BMMSC group compared with the BMMSC group. HO-1/BMMSCs showed better immunosuppressive effects after liver transplantation than the other treatments. Our findings reveal that HO-1 can enhance the effects of BMMSCs on inhibiting acute rejection in orthotopic liver transplantation in rats.

Preconditioned Mesenchymal Stromal Cells to Improve Allotransplantation Outcome

Mesenchymal stromal cells (MSCs) are tissue-derived progenitor cells with immunomodulatory as well as multilineage differentiation capacities, and have been widely applied as cellular therapeutics in different disease systems in both preclinical models and clinical studies. Although many studies have applied MSCs in different types of allotransplantation, the efficacy varies. It has been demonstrated that preconditioning MSCs prior to in vivo administration may enhance their efficacy. In the field of organ/tissue allotransplantation, many recent studies have shown that preconditioning of MSCs with (1) pretreatment with bioactive factors or reagents such as cytokines, or (2) specific gene transfection, could prolong allotransplant survival and improve allotransplant function. Herein, we review these preconditioning strategies and discuss potential directions for further improvement.

Immunological Determinants of Liver Transplant Outcomes Uncovered by the Rat Model

For many individuals with end-stage liver disease, the only treatment option is liver transplantation. However, liver transplant rejection is observed in 24%-80% of transplant patients and lifelong drug regimens that follow the transplant procedure lead to serious side effects. Furthermore, the pool of donor livers available for transplantation is far less than the demand. Well-characterized and physiologically relevant models of liver transplantation are crucial to a deeper understanding of the cellular processes governing the outcomes of liver transplantation and serve as a platform for testing new therapeutic strategies to enhance graft acceptance. Such a model has been found in the rat transplant model, which has an advantageous size for surgical procedures, similar postoperative immunological progression, and high genome match to the human liver. From rat liver transplant studies published in the last 5 years, it is clear that the rat model serves as a strong platform to elucidate transplant immunological mechanisms. Using the model, we have begun to uncover potential players and possible therapeutic targets to restore liver tolerance and preserve host immunocompetence. Here, we present an overview of recent literature for rat liver transplant models, with an aim to highlight the value of the models and to provide future perspectives on how these models could be further characterized to enhance the overall value of rat models to the field of liver transplantation.

A combination of the percentages of IFN-γ+CD4+T cells and granzyme B+CD19+B cells is associated with acute hepatic rejection: a case control study

Background

T cells and B cells play a key role in alloimmune responses. We aimed to characterize the shift of T cell subsets and B cell subsets during acute hepatic rejection, and further determine whether they could serve as a prognostic marker.

Methods

Blood samples together with the clinical data from liver transplant recipients with and without acute hepatic rejection were collected and analyzed as well as from a validation cohort.

Results

Upon activation the expression of TGF-β and granzyme B in CD19⁺B cells, and the expression of IL-2 and IFN-γ in CD4⁺T cells were higher in acute hepatic rejection. However, only the frequencies of granzyme B⁺CD19⁺B cells and IFN-γ⁺CD4⁺T cells correlated with liver function in addition to with each other. A combination of the two cell subsets as a novel marker could classify rejection versus non-rejection (area under the curve 0.811, p = 0.001) with the cut-off value of 62.93%, which was more sensitive for worse histological changes (p = 0.027). Moreover, the occurrence rate of acute rejection was higher in the group with the novel marker > 62.93% (p = 0.000). The role of the novel marker was further confirmed in a validation cohort, which was identified to be the only significant independent risk factor for acute rejection (odds ratio: 0.923; 95% CI confidence interval: 0.885–0.964; p = 0.000).

Conclusions

A combination of the percentages of IFN-γ⁺CD4⁺T cells and granzyme B⁺CD19⁺B cells can distinguish rejection from non-rejection, which can be used as a potential prognostic marker for acute rejection in liver transplant recipients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02855-w.

Mesenchymal Stromal Cell Therapy in Solid Organ Transplantation

Transplantation is the gold-standard treatment for the failure of several solid organs, including the kidneys, liver, heart, lung and small bowel. The use of tailored immunosuppressive agents has improved graft and patient survival remarkably in early post-transplant stages, but long-term outcomes are frequently unsatisfactory due to the development of chronic graft rejection, which ultimately leads to transplant failure. Moreover, prolonged immunosuppression entails severe side effects that severely impact patient survival and quality of life. The achievement of tolerance, i.e., stable graft function without the need for immunosuppression, is considered the Holy Grail of the field of solid organ transplantation. However, spontaneous tolerance in solid allograft recipients is a rare and unpredictable event. Several strategies that include peri-transplant administration of non-hematopoietic immunomodulatory cells can safely and effectively induce tolerance in pre-clinical models of solid organ transplantation. Mesenchymal stromal cells (MSC), non-hematopoietic cells that can be obtained from several adult and fetal tissues, are among the most promising candidates. In this review, we will focus on current pre-clinical evidence of the immunomodulatory effect of MSC in solid organ transplantation, and discuss the available evidence of their safety and efficacy in clinical trials.