Interpretation of transplant biopsies and immune responses following Treg cell therapy

iPSC-derived MSC therapy induces immune tolerance and supports long-term graft survival in mouse orthotopic tracheal transplants

Background

Lung transplantation is a life-saving surgical replacement of diseased lungs in patients with end-stage respiratory malfunctions. Despite remarkable short-term recovery, long-term lung survival continues to face several major challenges, including chronic rejection and severe toxic side effects due to global immunosuppression. Stem cell-based immunotherapy has been recognized as a crucial immunoregulatory regimen in various preclinical and clinical studies. Despite initial therapeutic outcomes, conventional stem cells face key limitations. The novel Cymerus™ manufacturing facilitates production of a virtually limitless supply of consistent human induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells, which could play a key role in selective immunosuppression and graft repair during rejection.

Methods

Here, we demonstrated the impact of iPSC-derived human MSCs on the development of immune tolerance and long-term graft survival in mouse orthotopic airway allografts. BALB/c → C57BL/6 allografts were reconstituted with iPSC-derived MSCs (2 million/transplant/at d0), and allografts were examined for regulatory T cells (Tregs), oxygenation, microvascular blood flow, airway epithelium, and collagen deposition during rejection.

Results

We demonstrated that iPSC-derived MSC treatment leads to significant increases in hTSG-6 protein, followed by an upregulation of mouse Tregs and IL-5, IL-10, and IL-15 cytokines, which augments graft microvascular blood flow and oxygenation, and thereby maintained a healthy airway epithelium and prevented the subepithelial deposition of collagen at d90 post transplantation.

Conclusions

Collectively, these data confirmed that iPSC-derived MSC-mediated immunosuppression has potential to establish immune tolerance and rescue allograft from sustained hypoxic/ischemic phase, and subsequently limits long-term airway epithelial injury and collagen progression, which therapeutically warrant a study of Cymerus iPSC-derived MSCs as a potential management option for immunosuppression in transplant recipients.

C5a Blockade Increases Regulatory T Cell Numbers and Protects Against Microvascular Loss and Epithelial Damage in Mouse Airway Allografts

Microvascular injury during acute rejection has been associated with massive infiltration of CD4+ T effector cells, and the formation of complement products (C3a and C5a). Regulatory T cells (Tregs) are potent immunosuppressors of the adaptive immune system and have proven sufficient to rescue microvascular impairments. Targeting C5a has been linked with improved microvascular recovery, but its effects on the Treg and T effector balance is less well known. Here, we demonstrate the impact of C5a blockade on Treg induction and microvascular restoration in rejecting mouse airway allografts. BALB/c→C57BL/6 allografts were treated with a C5a-neutralizing l-aptamer (10 mg/kg, i.p. at d0 and every second day thereafter), and allografts were serially monitored for Treg infiltration, tissue oxygenation (tpO2), microvascular blood flow, and functional microvasculature between donor and recipients during allograft rejection. We demonstrated that C5a blocking significantly leads to enhanced presence of Tregs in the allograft, reinstates donor-recipient functional microvasculature, improves tpO2, microvascular blood flow, and epithelial repair, followed by an upregulation of IL-5, TGF-β, IL-10 vascular endothelial growth factor, and ANGPT1 gene expression, while it maintained a healthy epithelium and prevented subepithelial collagen deposition at d28 posttransplantation. Together, these data indicate that inhibition of C5a signaling has potential to preserve microvasculature and rescue allograft from a sustained hypoxic/ischemic phase, limits airway tissue remodeling through the induction of Treg-mediated immune tolerance. These findings may be useful in designing anti-C5a therapy in combination with existing immunosuppressive regimens to rescue tissue/organ rejection.

In Vivo Costimulation Blockade-Induced Regulatory T Cells Demonstrate Dominant and Specific Tolerance to Porcine Islet Xenografts

BACKGROUND

Although islet xenotransplantation is a promising therapy for type 1 diabetes, its clinical application has been hampered by cellular rejection and the requirement for high levels of immunosuppression. The aim of this study was to determine the role of Foxp3 regulatory T (Treg) cells in costimulation blockade-induced dominant tolerance to porcine neonatal islet cell cluster (NICC) xenografts in mice.

METHODS

Porcine-NICC were transplanted under the renal capsule of BALB/c or C57BL/6 recipients and given a single dose of CTLA4-Fc at the time of transplant and 4doses of anti-CD154 mAb to day 6. Depletion of Foxp3Treg cell was performed in DEpletion of REGulatory T cells mice at day 80 posttransplantation. Foxp3Treg cell from spleens of treated BALB/c mice (tolerant Treg cell), and splenocytes were cotransferred into islet transplanted nonobese diabetic background with severe combined immunodeficiency mice to assess suppressive function.

RESULTS

In treated mice, increased numbers of Foxp3Treg cell were identified in the porcine-NICC xenografts, draining lymph node, and spleen. Porcine-NICC xenografts from treated mice expressed elevated levels of TGF-β, IL-10 and IFN-γ. Porcine-NICC xenograft tolerance was abrogated after depletion of Foxp3Treg cell. Tolerant Treg cell produced high levels of IL-10 and had diverse T cell receptor Vβ repertoires with an oligoclonal expansion in CDR3 of T cell receptor Vβ14. These tolerant Treg cells had the capacity to transfer dominant tolerance and specifically exhibited more potent regulatory function to porcine-NICC xenografts that naive Treg cell.

CONCLUSIONS

This study demonstrated that short-term costimulation blockade-induced dominant tolerance and that Foxp3Treg cell played an essential role in its maintenance. Foxp3Treg cells were activated and had more potent regulatory function in vivo than naive Treg cells.

Cell Therapy in Kidney Transplantation: Focus on Regulatory T Cells

Renal transplantation is the renal replacement modality of choice for suitable candidates with advanced CKD or ESRD. Prevention of rejection, however, requires treatment with nonspecific pharmacologic immunosuppressants that carry both systemic and nephrologic toxicities. Use of a patient's own suppressive regulatory T cells (Tregs) is an attractive biologic approach to reduce this burden. Here, we review the immunologic underpinnings of Treg therapy and technical challenges to developing successful cell therapy. These issues include the selection of appropriate Treg subsets, ex vivo Treg expansion approaches, how many Tregs to administer and when, and how to care for patients after Treg administration.

Global Regulatory T-Cell Research from 2000 to 2015: A Bibliometric Analysis

We aimed to analyze the global scientific output of regulatory T-cell (Treg) research and built a model to qualitatively and quantitatively evaluate publications from 2000 to 2015. Data were obtained from the Web of Science Core Collection (WoSCC) of Thomson Reuters on January 1, 2016. The bibliometric method and Citespace III were used to analyze authors, journals, publication outputs, institutions, countries, research areas, research hotspots, and trends. In total, we identified 35,741 publications on Treg research from 2000 to 2015, and observed that the annual publication rate increased with time. The Journal of Immunology published the highest number of articles, the leading country was the USA, and the leading institute was Harvard University. Sakaguchi, Hori, Fontenot, and Wang were the top authors in Treg research. Immunology accounted for the highest number of publications, followed by oncology, experimental medicine, cell biology, and hematology. Keyword analysis indicated that autoimmunity, inflammation, cytokine, gene expression, foxp3, and immunotherapy were the research hotspots, whereas autoimmune inflammation, gene therapy, granzyme B, RORγt, and th17 were the frontiers of Treg research. This bibliometric analysis revealed that Treg-related studies are still research hotspots, and that Treg-related clinical therapies are the research frontiers; however, further study and collaborations are needed worldwide. Overall, our findings provide valuable information for the editors of immunology journals to identify new perspectives and shape future research directions.