Sensitization and Desensitization in Vascularized Composite Allotransplantation

Urinary bladder transplantation in humans - current status and future perspectives

Urinary bladder vascularized allograft transplantation in humans is currently extensively being investigated worldwide, owing to the theoretical potential of this approach as a therapeutic option for individuals with end-stage, non-oncological bladder conditions or congenital bladder pathologies. To date, a successful attempt at urinary bladder autotransplantation was carried out in a heart-beating brain-dead research human donor. The robot-assisted surgical technique was shown to be optimal for performing this procedure, achieving a good performance in terms of both bladder allograft collection as well as vascular, ureterovesical and vesicourethral anastomoses. The urinary bladder vascularized allograft would be an alternative to traditional urinary diversion methods that rely on the use of intestinal segments, potentially avoiding adverse effects associated with these approaches. However, different from ileal urinary diversion, bladder transplantation would require lifelong immune suppression. Clinical trials are in progress to assess the vascularized bladder allograft transplantation technique, as well as the safety of this procedure in oncological and non-oncological indications.

Immunogenicity and tolerance induction in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) is the transplantation of multiple tissues such as skin, muscle, bone, nerve, and vessels, as a functional unit (i.e., hand or face) to patients suffering from major tissue trauma and functional deficits. Though the surgical feasibility has been optimized, issues regarding graft rejection remains. VCA rejection involves a diverse population of cells but is primarily driven by both donor and recipient lymphocytes, antigen-presenting cells, macrophages, and other immune as well as donor-derived cells. In addition, it is commonly understood that different tissues within VCA, such as the skin, elicits a stronger rejection response. Currently, VCA recipients are required to follow potent and lifelong immunosuppressing regimens to maximize graft survival. This puts patients at risk for malignancies, opportunistic infections, and cancers, thereby posing a need for less perilous methods of inducing graft tolerance. This review will provide an overview of cell populations and mechanisms, specific tissue involved in VCA rejection, as well as an updated scope of current methods of tolerance induction.

Transplantation of Donor-Recipient Chimeric Cells Restores Peripheral Blood Cell Populations and Increases Survival after Total Body Irradiation-Induced Injury in a Rat Experimental Model

Current therapies for acute radiation syndrome (ARS) involve bone marrow transplantation (BMT), leading to graft-versus-host disease (GvHD). To address this challenge, we have developed a novel donor-recipient chimeric cell (DRCC) therapy to increase survival and prevent GvHD following total body irradiation (TBI)-induced hematopoietic injury without the need for immunosuppression. In this study, 20 Lewis rats were exposed to 7 Gy TBI to induce ARS, and we assessed the efficacy of various cellular therapies following systemic intraosseous administration. Twenty Lewis rats were randomly divided into four experimental groups (n = 5/group): saline control, allogeneic bone marrow transplantation (alloBMT), DRCC, and alloBMT + DRCC. DRCC were created by polyethylene glycol-mediated fusion of bone marrow cells from 24 ACI (RT1a) and 24 Lewis (RT11) rat donors. Fusion feasibility was confirmed by flow cytometry and confocal microscopy. The impact of different therapies on post-irradiation peripheral blood cell recovery was evaluated through complete blood count, while GvHD signs were monitored clinically and histopathologically. The chimeric state of DRCC was confirmed. Post-alloBMT mortality was 60%, whereas DRCC and alloBMT + DRCC therapies achieved 100% survival. DRCC therapy also led to the highest white blood cell counts and minimal GvHD changes in kidney and skin samples, in contrast to alloBMT treatment. In this study, transplantation of DRCC promoted the recovery of peripheral blood cell populations after TBI without the development of GVHD. This study introduces a novel and promising DRCC-based bridging therapy for treating ARS and extending survival without GvHD.

Novel Human Umbilical Di-Chimeric (HUDC) cell therapy for transplantation without life-long immunosuppression

Background

Cell-based therapies are promising for tolerance induction in bone marrow (BM), solid organs, and vascularized composite allotransplantation (VCA). The toxicity of bone marrow transplantation (BMT) protocols precludes this approach from routine clinical applications. To address this problem, we developed a new therapy of Human Umbilical Di-Chimeric (HUDC) cells for tolerance induction in transplantation. This study established in vitro characterization of the created HUDC cells.

Methods

We performed sixteen ex vivo polyethylene glycol (PEG)-mediated fusions of human umbilical cord blood (UCB) cells from two unrelated donors. Fusion feasibility was confirmed in vitro by flow cytometry (FC) and confocal microscopy (CM). The HUDC cells' genotype was assessed by lymphocytotoxicity test and short tandem repeat-polymerase chain reaction (STR-PCR) analysis, phenotype by FC, viability by LIVE/DEAD® assay, and apoptosis level by Annexin V staining. We used COMET assay to assess HUDC cells' genotoxicity after the fusion procedure. Clonogenic properties of HUDC cells were evaluated by colony forming unit (CFU) assay. Mixed lymphocyte reaction (MLR) assay assessed immunogenic and tolerogenic properties of HUDC cells.

Results

We confirmed the creation of HUDC cells from two unrelated human donors of UCB cells by FC and CM. Human leukocyte antigen (HLA) class I and II typing, and STR-PCR analysis of HUDC cells confirmed the presence of alleles and loci from both unrelated UCB donors (donor chimerism: 49%±8.3%, n=4). FC confirmed the hematopoietic phenotype of HUDC cells. We confirmed high HUDC cells' viability (0.47% of dead cells) and a low apoptosis level of fused HUDC cells (15.9%) compared to positive control of PKH-stained UCB cells (20.4%) before fusion. COMET assay of HUDC cells revealed a lack of DNA damage. CFU assay confirmed clonogenic properties of HUDC cells, and MLR assay revealed a low immunogenicity of HUDC cells.

Conclusions

This study confirmed creation of a novel HUDC cell line by ex vivo PEG-mediated fusion of UCB cells from two unrelated donors. The unique concept of creating a HUDC cell line, representing the genotype and phenotype of both, transplant donor and the recipient, introduces a promising approach for tolerance induction in BM, solid organs, and VCA transplantation.

Cellular activation pathways and interaction networks in vascularized composite allotransplantation

Vascularized composite allotransplantation (VCA) is an evolving field of reconstructive surgery that has revolutionized the treatment of patients with devastating injuries, including those with limb losses or facial disfigurement. The transplanted units are typically comprised of different tissue types, including skin, mucosa, blood and lymphatic vasculature, muscle, and bone. It is widely accepted that the antigenicity of some VCA components, such as skin, is particularly potent in eliciting a strong recipient rejection response following transplantation. The fine line between tolerance and rejection of the graft is orchestrated by different cell types, including both donor and recipient-derived lymphocytes, macrophages, and other immune and donor-derived tissue cells (e.g., endothelium). Here, we delineate the role of different cell and tissue types during VCA rejection. Rejection of VCA grafts and the necessity of life-long multidrug immunosuppression remains one of the major challenges in this field. This review sheds light on recent developments in decoding the cellular signature of graft rejection in VCA and how these may, ultimately, influence the clinical management of VCA patients by way of novel therapies that target specific cellular processes.

Potential Roles of miRNAs in Acute Rejection for Vascularized Composite Allotransplantation

Aim

The development of microsurgery has greatly advanced vascularized composite allotransplantation (VCA). However, like organ transplantation, VCA is also limited by acute rejection, and concerns regarding long-term survival and function of the transplanted graft. Therefore, it is necessary to elucidate the molecular mechanisms underlying acute rejection caused by VCA, in order to improve patient survival.

Methods

Firstly, we used Brown Norway rats and Lewis rats to construct animal model of VCA. Regularly record the appearance changes of all subjects. Specimens were collected for histological examination, microRNAs (miRNAs) sequencing and RT-qPCR verification when acute immune rejection occurred. Then, bioinformatics analysis was employed to predict miRNA related molecules and pathway information. Finally, differentially expressed miRNAs were tested and verified.

Results

MiRNAs are small non coding RNA transcripts that regulate gene expression at the post-transcriptional level. Studies have shown that miRNAs are involved in immune regulation and several miRNAs have been identified that are potential diagnostic and prognostic biomarkers of acute rejection. In this study, we found that the expression levels of rno-miR-21-5p, rno-miR-340-5p, rno-miR-1-3p and rno-miR-195-5p are significantly associated with acute rejection following VCA.

Conclusion

This miRNA signature can potentially an auxiliary diagnostic indicator of rejection, which can help clinicians adjust the immunosuppressive program in time during acute rejection.