Transplantation Model Research Articles

Study on the Extrapolability of Current Tumorgenicity Test With Mice by Comparing the Syngeneic or Allogeneic Mouse Transplantation Model.

The extrapolability of the current tumorigenicity test performed by transplanting human cell product into immunodeficient (NOG) mice was investigated. For this purpose, the susceptibility to form teratomas of NOG mice was assessed by transplanting undifferentiated human-induced pluripotent stem cells (hiPSCs) as positive control cells via the liver, striatum, or tail vein and evaluating the TPD50 value (dose required to form teratomas in half of the transplanted mice). This was then compared to the TPD50 of syngeneic or allogeneic mouse models. The TPD50 of C57/BL/6(B6)-iPSC or 129/Ola(129)-embryonic stem cell (ESC) transplanted into the liver of syngeneic mice was 4.08 × 105 and 4.64 × 104 cells, respectively, while the TPD50 of hiPSC administered into the liver of NOG mice was 4.64 × 104 cells. The TPD50 of B6-miPSC-synergic, 129-mESC-synergic, or 129-cell/B6 allogeneic transplantation into the striatum was 5.09 × 102, 1.0 × 104, and 3.73 × 104 cells, respectively, while that of hiPSC/NOG mice was 1.0 × 103 cells. The TPD50 for B6-miPSC or 129-mESC syngeneic tail vein infusion was 3.16 × 106 or 5.62 × 106 cells, respectively, while no incidence was observed from 1 × 107 B6-miPSCs in 129 mice or hiPSCs in NOG mice infusion study. Although the number of data sets was limited, these data indicate that the teratoma formation from transplanted undifferentiated hiPSCs via the liver or striatum in NOG mice is comparable to that in syngeneic or allogeneic mouse transplantation model, suggesting that the result of the current tumorigenicity test in NOG mice would provide useful information to infer the incidence of teratoma from residual undifferentiated hPSCs in hPSC-derived products after transplantation.

DYRK1B blockade promotes tumoricidal macrophage activity in pancreatic cancer

ObjectiveHighly malignant pancreatic ductal adenocarcinoma (PDAC) is characterised by an abundant immunosuppressive and fibrotic tumour microenvironment (TME). Future therapeutic attempts will therefore demand the targeting of tumours and stromal compartments...

The DNA methyltransferase inhibitor 5-aza-4'-thio-2'-deoxycytidine induces C>G transversions and acute lymphoid leukemia development.

DNA methyltransferase inhibitors (DNMTi), most commonly cytidine analogs, are compounds that decrease 5'-cytosine methylation. DNMTi are used clinically based on the hypothesis that cytosine demethylation will lead to re-expression of tumor suppressor genes. 5-Aza-4'-thio-2'-deoxycytidine (Aza TdCyd or ATC) is a recently described thiol substituted DNMTi that has been shown to have anti-tumor activity in solid tumor models. Here, we investigated the therapeutic potential of ATC in a murine transplantation model of myelodysplastic syndrome. ATC treatment led to transformation of transplanted wild-type bone marrow nucleated cells into lymphoid leukemia, and healthy mice treated with ATC also developed lymphoid leukemia. Whole exome sequencing revealed thousands of acquired mutations, almost all of which were C>G transversions in a specific 5'-NCG-3' context. These mutations involved dozens of genes involved in human lymphoid leukemia, such as Notch1, Pten, Pax5, Trp53, and Nf1. Human cells treated in vitro with ATC showed thousands of acquired C>G transversions in a similar context. Deletion of Dck, the rate-limiting enzyme for the cytidine salvage pathway, eliminated C>G transversions. Taken together, these findings demonstrate a highly penetrant mutagenic and leukemogenic phenotype associated with ATC.

IL-6 inhibition prevents costimulation blockade-resistant allograft rejection in T cell-depleted recipients by promoting intragraft immune regulation in mice

The efficacy of costimulation blockade with CTLA4-Ig (belatacept) in transplantation is limited due to T cell-mediated rejection, which also persists after induction with anti-thymocyte globulin (ATG). Here, we investigate why ATG fails to prevent costimulation blockade-resistant rejection and how this barrier can be overcome. ATG did not prevent graft rejection in a murine heart transplant model of CTLA4-Ig therapy and induced a pro-inflammatory cytokine environment. While ATG improved the balance between regulatory T cells (Treg) and effector T cells in the spleen, it had no such effect within cardiac allografts. Neutralizing IL-6 alleviated graft inflammation, increased intragraft Treg frequencies, and enhanced intragraft IL-10 and Th2-cytokine expression. IL-6 blockade together with ATG allowed CTLA4-Ig therapy to achieve long-term, rejection-free heart allograft survival. This beneficial effect was abolished upon Treg depletion. Combining ATG with IL-6 blockade prevents costimulation blockade-resistant rejection, thereby eliminating a major impediment to clinical use of costimulation blockers in transplantation.

Dose-dependent effects of Dnmt3a in an inducible murine model of KrasG12D-driven leukemia

DNMT3A mutations are frequently found in clonal hematopoiesis and a variety of hematologic malignancies, including acute myeloid leukemia. An assortment of mouse models have been engineered to explore the tumorigenic potential and malignant lineage bias due to loss of function of DNMT3A in consort with commonly comutated genes in myeloid malignancies, such as Flt3, Nras, Kras, and c-Kit. We employed several tamoxifen-inducible Cre-ERT2 murine model systems to study the effects of constitutively active KrasG12D-driven myeloid leukemia (Kras) development together with heterozygous (3aHet) or homozygous Dnmt3a deletion (3aKO). Due to the rapid generation of diverse nonhematologic tumors appearing after tamoxifen induction, we employed a transplantation model. With pretransplant tamoxifen induction, most Kras mice died quickly of T-cell malignancies regardless of Dnmt3a status. Using posttransplant induction, we observed a dose-dependent effect of DNMT3A depletion that skewed the leukemic phenotype toward a myeloid lineage. Specifically, 64% of 3aKO/Kras mice had exclusively myeloid disease compared with 36% of 3aHet/Kras and only 13% of Kras mice. Here, 3aKO combined with Kras led to increased disease burden, multiorgan infiltration, and faster disease progression. DOT1L inhibition exerted profound antileukemic effects in malignant 3aKO/Kras cells, but not malignant cells with Kras mutation alone, consistent with the known sensitivity of DNMT3A-mutant leukemia to DOT1L inhibition. RNAseq from malignant myeloid cells revealed that biallelic Dnmt3a deletion was associated with loss of cell-cycle regulation, MYC activation, and TNF⍺ signaling. Overall, we developed a robust model system for mechanistic and preclinical investigations of acute myeloid leukemia with DNMT3A and Ras-pathway lesions.

Pirfenidone treatment reduces cardiac allograft vasculopathy in a mouse model

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): ISHLT research grant Objectives Chronic rejection in the form of cardiac allograft vasculopathy after heart transplantation remains without effective treatment. Main characteristics of cardiac allograft vasculopathy are immigration of leukocytes and proliferation of smooth muscle cells - collectively resulting in development of a neointima narrowing the vessel lumen and leading to graft ischemia. Pirfenidone is an anti-fibrotic drug with anti-inflammatory properties that is already approved for treatment of idiopathic pulmonary fibrosis. The aim of this study was to evaluate whether application of pirfenidone leads to reduced luminal occlusion corresponding with decreased chronic rejection in a mouse transplant model. Methods Murine thoracic aortas were transplanted into the abdominal aorta of CBA mice (H2k). For allogeneic transplantation, C57BL/6 mice (H2b) were used as donors (n = 8 / group). After transplantation, mice were fed a 0.5% pirfenidone diet versus conventional diet. Preliminary tests were performed determining the blood pirfenidone level by mass spectrometry throughout the study period on days 1, 3, 7, 14, 21 and 28, respectively, as well as after obtaining the aortic grafts on day 30 for histological analysis. Results Preliminary tests confirmed the successful uptake of pirfenidone by achieving constant plasma levels of pirfenidone and its metabolite 5-carboxy-pirfenidone over the whole examination period. Pirfenidone treated murine aortic grafts showed significantly reduced neointima formation compared to control allografts (luminal occlusion: 32.92 % ± 13.02 % vs. 42.44 % ± 19.81 %, p=0.046). As expected, syngeneic aortic grafts with and without pirfenidone treatment showed no luminal occlusion. Conclusion The results indicate that pirfenidone application after aortic transplantation reduces neointima formation and thus chronic rejection in a mouse aortic transplant model. Further analyses of underlying mechanisms are currently underway.

Mechanical load regulates the proliferation of multiple cell types in the heart

Abstract Funding Acknowledgements None. Introduction The adult mammalian heart has a poor regenerative and angiogenic potential. At the same time, both primary cardiac tumors and cardiac metastases are extremely rare. This suggests that shared mechanisms may halt the proliferation of cardiac (both cardiomyocyte and endothelial) and cancer cells. Among the mechanisms that have been claimed to be responsible for the loss of proliferative potential of cardiomyocytes early after birth is a sudden increase in mechanical load. Purpose Here, we investigate whether alterations in mechanical load affect the proliferation of multiple cell types in the heart. Methods Adult heart unloading in vivo was achieved using a mouse model of heterotopic heart transplantation, followed by EdU injection to label proliferating cells. Engineered heart tissues (EHTs) were generated using neonatal cardiomyocytes and fibroblasts, with a modified protocol allowing to finely tune mechanical load. Primary cardiac endothelial cells and multiple types of cancer cells (lung, melanoma and colon cancer) along with adult cardiac endothelial cells were included in EHTs. Results In line with our hypothesis, unloaded, heterotransplanted hearts showed a significant number of proliferating cardiomyocytes and endothelial cells, which were almost absent in native hearts. While cancer cells did not grow in native hearts, they massively proliferated in unloaded hearts. Consistent with in vivo results, mechanical unloading in EHTs significantly increased the percentage of EdU-positive cardiomyocytes, endothelial and cancer cells. In contrast, increasing afterload reduced cell proliferation in all cell types. Mechanistically, we identified Nesprin2 as an essential factor in sensing mechanical load and translating it into a cell proliferation arrest. Conclusions Overall, these data indicate that variations in mechanical load have a dramatic effect on the proliferation of multiple cell types within the heart tissue, including cardiomyocytes, endothelial and cancer cells and that Nesprin2 is required to mediate this effect.Unloading in the heartUnloading in EHT

Inhibition of interferon regulatory factor 4 orchestrates T cell dysfunction, extending mouse cardiac allograft survival.

T cell dysfunction, which includes exhaustion, anergy, and senescence, is a distinct T cell differentiation state that occurs after antigen exposure. Although T cell dysfunction has been a cornerstone of cancer immunotherapy, its potential in transplant research, while not yet as extensively explored, is attracting growing interest. Interferon regulatory factor 4 (IRF4) has been shown to play a pivotal role in inducing T cell dysfunction. A novel ultra-low-dose combination of Trametinib and Rapamycin, targeting IRF4 inhibition, was employed to investigate T cell proliferation, apoptosis, cytokine secretion, expression of T-cell dysfunction-associated molecules, effects of MAPK and mammalian target of Rapamycin (mTOR) signaling pathways, and allograft survival in both in vitro and BALB/c to C57BL/6 mouse cardiac transplantation models. In vitro, blockade of IRF4 in T cells effectively inhibited T cell proliferation, increased apoptosis, and significantly upregulated the expression of programmed cell death protein 1 (PD-1), Helios, CD160, and cytotoxic T lymphocyte-associated antigen (CTLA-4), markers of T cell dysfunction. Furthermore, it suppressed the secretion of pro-inflammatory cytokines interferon (IFN)-γ and interleukin (IL)-17. Combining ultra-low-dose Trametinib (0.1mg·kg-1·day-1) and Rapamycin (0.1mg·kg-1·day-1) demonstrably extended graft survival, with 4 out of 5 mice exceeding 100 days post-transplantation. Moreover, analysis of grafts at day 7 confirmed sustained IFN regulatory factor 4 (IRF4) inhibition, enhanced PD-1 expression, and suppressed IFN-γ secretion, reinforcing the in vivo efficacy of this IRF4-targeting approach. The combination of Trametinib and Rapamycin synergistically inhibited the MAPK and mTOR signaling network, leading to a more pronounced suppression of IRF4 expression. Targeting IRF4, a key regulator of T cell dysfunction, presents a promising avenue for inducing transplant immune tolerance. In this study, we demonstrate that a novel ultra-low-dose combination of Trametinib and Rapamycin synergistically suppresses the MAPK and mTOR signaling network, leading to profound IRF4 inhibition, promoting allograft acceptance, and offering a potential new therapeutic strategy for improved transplant outcomes. However, further research is necessary to elucidate the underlying pharmacological mechanisms and facilitate translation to clinical practice.

Formation of Stable Vascular Networks by 3D Coaxial Printing and Schiff-Based Reaction.

Vascularized organs hold potential for various applications, such as organ transplantation, drug screening, and pathological model establishment. Nevertheless, the in vitro construction of such organs encounters many challenges, including the incorporation of intricate vascular networks, the regulation of blood vessel connectivity, and the degree of endothelialization within the inner cavities. Natural polymeric hydrogels, such as gelatin and alginate, have been widely used in three-dimensional (3D) bioprinting since 2005. However, a significant disparity exists between the mechanical properties of the hydrogel materials and those of human soft tissues, necessitating the enhancement of their mechanical properties through modifications or crosslinking. In this study, we aim to enhance the structural stability of gelatin-alginate hydrogels by crosslinking gelatin molecules with oxidized pullulan (i.e., a polysaccharide) and alginate molecules with calcium chloride (CaCl2). A continuous small-diameter vascular network with an average outer diameter of 1 mm and an endothelialized inner surface is constructed by printing the cell-laden hydrogels as bioinks using a coaxial 3D bioprinter. The findings demonstrate that the single oxidized pullulan crosslinked gelatin and oxidized pullulan/CaCl2 double-crosslinked gelatin-alginate hydrogels both exhibit a superior structural stability compared to their origins and CaCl2 solely crosslinked gelatin-alginate hydrogels. Moreover, the innovative gelatin and gelatin-alginate hydrogels, which have excellent biocompatibilities and very low prices compared with other hydrogels, can be used directly for tissue/organ construction, tissue/organ repairment, and cell/drug transportation.

#1887 Comparison of the efficacy of preservation at 22°C versus 4°C in warm ischemic kidneys from MHC-inbred CLAWN miniature swine

Abstract Background and Aims Static cold preservation, the standard in transplantation, is primarily aimed at reducing metabolic and oxygen demand. Kidney transplantation from donors after cardiac death (DCD) addresses the shortage of donor organs, but these kidneys are susceptible to cold preservation. A previous study using small animal models demonstrated the potential benefits of preserving DCD kidneys at a warmer temperature of 22°C using extracellular-type solutions (Iwai S., PLoS One 2012). Based on this foundational research, our study aimed to evaluate the efficacy of preserving warm ischemic kidneys at temperatures of either 4°C or 22°C using preclinical large animal miniature swine models. Method After 2 hours of warm ischemia, the pig kidneys were preserved for 60 minutes at either 4°C or 22°C with extracellular-type solutions (ETK®). In Experiment 1, these preserved kidneys underwent ex-vivo perfusion for 120 minutes at 37°C with a mean arterial pressure of 85 mmHg. This perfusion used a Ringer's solution supplemented with red blood cells, aiming to determine the early functionality of kidneys subjected to 2-hour warm ischemia in transplantation and to assess whether preservation at 4°C or 22°C could maintain renal function during the acute postoperative period (n = 3 in each group). During this period, both physiological parameters (renal blood flow, intrarenal resistance, and urine output) and metabolic parameters (oxygen consumption) were evaluated. In Experiment 2, kidneys that underwent similar warm ischemia and preservation procedures were transplanted into MHC-matched recipients. These recipients received continuous tacrolimus treatment for 12 days to minimize rejection due to minor antigen differences. After transplantation, renal function was monitored and assessed by serum creatinine levels and renal biopsies for 14 days (n = 3 in each group). Results Experiment 1 demonstrated that kidneys subjected to 2 hours of warm ischemia and then preserved at 22°C had better physiological and metabolic indices during a subsequent 2-hour ex-vivo perfusion compared to those preserved at 4°C. The results were as follows: 22°C vs. 4°C—mean renal blood flow (27 ± 5 vs. 10 ± 0 ml/min), intrarenal resistance (3.5 ± 0.5 vs. 8.7 ± 0.1 mmHg/ml/min), total urine volume (14 ± 5 vs. 5 ± 4 ml), and oxygen consumption (224 ± 39 vs. 93 ± 16 ml/min/g). Importantly, there was no complete cessation of blood flow in either group, indicating the potential for long-term evaluation using a transplantation model. In Experiment 2, kidneys preserved at 22°C resulted in significantly lower peak post-transplant serum creatinine levels compared to those preserved at 4°C (3.9 ± 0.6 mg/dl vs 8.9 ± 0.3 mg/dl, p = 0.0015). There was a marked decrease in the area under the curve of creatinine from day 0 to day 14, with a 36% reduction from 61 mg/dL per day in the 4°C group to 39 mg/dL per day in the 22°C group. Renal biopsies performed on post-operative day 4 revealed extensive necrosis in the renal tubules of kidneys stored at 4°C. In contrast, kidneys preserved at 22°C showed more localized damage. In addition, PCNA staining indicated accelerated regeneration of the tubular epithelium in kidneys preserved at 22°C. Conclusion This study demonstrates that kidneys subjected to 2 hours of warm ischemia from MHC-inbred miniature swine are more effectively preserved at 22°C than at 4°C when using an extracellular-type solution. To our knowledge, this is the first report demonstrating the efficacy of organ preservation at 22°C in clinically relevant, large animal models. From the evaluation of ex-vivo perfusion of preserved kidneys, it was suggested that kidneys preserved at 22°C maintain better blood perfusion to severely ischemic kidneys immediately after transplantation, which leads to the rapid recovery of renal function of acute kidney injury. Future research will focus on elucidating the mechanisms underlying the superior outcomes associated with 22°C preservation. In addition, investigations will be conducted to determine whether similar benefits can be achieved using intracellular-type solutions, which are more commonly used in renal transplantation.

Surgical Protocol for Partial Heart Transplantation in Growing Piglets.

Partial heart transplantation is a new approach to deliver growing heart valve implants. Partial heart transplants differ from heart transplants because only the part of the heart containing the necessary heart valve is transplanted. This allows partial heart transplants to grow, similar to the valves in heart transplants. However, the transplant biology of partial heart transplantation remains unexplored. This is a critical barrier to progress of the field. Without knowledge about the specific transplant biology of partial heart transplantation, children with partial heart transplants are empirically treated like children with heart transplants because the valves in heart transplants are known to grow. In order to progress the field, an animal model for partial heart transplantation is necessary. Here, we contribute our surgical protocol for partial heart transplantation in growing piglets. All aspects of partial heart transplantation, including the donor procedure, the recipient procedure, and recipient perioperative care are described in detail. There are important nuances in the conduct of virtually all aspects of open heart surgery that differs in piglets from humans. Our surgical protocol, which is based on our experience with 34 piglets, will allow other investigators to leverage our experience to seek fundamental knowledge about the nature of partial heart transplants. This is significant because the partial heart transplant model in piglets is complex and very resource intensive.

#1945 Comparative analysis of kidney transplantation modeled using precision-cut kidney slices and kidney transplantation in pigs

Abstract Background and Aims Kidney transplants are at risk for so far unavoidable ischemia-reperfusion injury. Several experimental kidney transplantation models are available to study this injury, but all have their own limitations. Here, we describe precision-cut kidney slices (PCKS) as a novel model of kidney ischemia-reperfusion injury in comparison with pig and human kidney transplantation. Method Following bilateral nephrectomy in pigs, we applied warm ischemia (1 h), cold ischemia (20 h) and a reperfusion period (4 h) to one whole kidney undergoing transplantation to a recipient pig and, in parallel, established PCKS undergoing ischemia and modeled reperfusion. Tissues were analyzed using standard histopathology assessment by two blinded pathologists, and bulk RNAseq with gene set enrichment analysis with comparison to human kidney biopsy gene sets obtained from Gene Expression Omnibus. Results Histopathological assessment revealed the presence of some but not all morphological features of tubular injury in PCKS as seen in pig kidney transplantation. RNAseq demonstrated that the majority of changes occurred after reperfusion only, with a partial overlap between PCKS and kidney transplantation, with some differences in transcriptional response attributable to systemic inflammatory responses and immune cell migration. Comparison of PCKS and pig kidney transplantation with RNAseq data from human kidney biopsies by gene set enrichment analysis revealed that both PCKS and pig kidney transplantation reproduced the post-reperfusion pattern of human kidney transplantation. In contrast, only post-cold ischemia PCKS and pig kidney partially resembled the gene set of human acute kidney injury. Conclusion Overall, the present study established that a PCKS protocol can model kidney transplantation and its reperfusion-related damage on a histological and a transcriptomic level. PCKS may thus expand the toolbox for developing novel therapeutic strategies against ischemia-reperfusion injury.

Characterization of an orthotopic mouse transplant model reveals early changes in the tumor microenvironment of lung cancer

Characterization of an orthotopic mouse transplant model reveals early changes in the tumor microenvironment of lung cancer

Clinical Trial Protocol for Porcine Islet Xenotransplantation in South Korea.

Islet transplantation holds promise for treating selected type 1 diabetes mellitus patients, yet the scarcity of human donor organs impedes widespread adoption. Porcine islets, deemed a viable alternative, recently demonstrated successful longterm survival without zoonotic risks in a clinically relevant pig-to-non-human primate islet transplantation model. This success prompted the development of a clinical trial protocol for porcine islet xenotransplantation in humans. A single-center, open-label clinical trial initiated by the sponsor will assess the safety and efficacy of porcine islet transplantation for diabetes patients at Gachon Hospital. The protocol received approval from the Gachon Hospital Institutional Review Board (IRB) and the Korean Ministry of Food and Drug Safety (MFDS) under the Investigational New Drug (IND) process. Two diabetic patients, experiencing inadequate glycemic control despite intensive insulin treatment and frequent hypoglycemic unawareness, will be enrolled. Participants and their family members will engage in deliberation before xenotransplantation during the screening period. Each patient will receive islets isolated from designated pathogen-free pigs. Immunosuppressants and systemic infection prophylaxis will follow the program schedule. The primary endpoint is to confirm the safety of porcine islets in patients, and the secondary endpoint is to assess whether porcine islets can reduce insulin dose and the frequency of hypoglycemic unawareness. A clinical trial protocol adhering to global consensus guidelines for porcine islet xenotransplantation is presented, facilitating streamlined implementation of comparable human trials worldwide.

Lack of TGFβ signaling competency predicts immune poor cancer conversion to immune rich and response to checkpoint blockade.

Transforming growth factor beta (TGFβ) is well-recognized as an immunosuppressive player in the tumor microenvironment but also has a significant impact on cancer cell phenotypes. Loss of TGFβ signaling impairs DNA repair competency, which is described by a transcriptomic score, βAlt. Cancers with high βAlt have more genomic damage and are more responsive to genotoxic therapy. The growing appreciation that cancer DNA repair deficits are important determinants of immune response prompted us to investigate the association of βAlt with response to immune checkpoint blockade (ICB). We predicted that high βAlt tumors would be infiltrated with lymphocytes because of DNA damage burden and hence responsive to ICB. We analyzed public transcriptomic data from clinical trials and preclinical models using transcriptomic signatures of TGFβ targets, DNA repair genes, tumor educated immune cells and interferon. A high βAlt, immune poor mammary tumor derived transplant model resistant to programmed death ligand 1 (PD-L1) antibodies was studied using multispectral flow cytometry to interrogate the immune system. Metastatic bladder patients in IMvigor 210 who responded to ICB had significantly increased βAlt scores and experienced significantly longer overall survival compared to those with low βAlt scores (hazard ratio 0.62, P=0.011) . Unexpectedly, 75% of high βAlt cancers were immune poor as defined by low expression of tumor educated immune cell and interferon signatures. The association of high βAlt with immune poor cancer was also evident in TCGA and preclinical cancer models. We used a high βAlt, immune poor cancer to test therapeutic strategies to overcome its inherent anti-PD-L1 resistance. Combination treatment with radiation and TGFβ inhibition were necessary for lymphocytic infiltration and activated NK cells were required for ICB response. Bioinformatic analysis identified high βAlt, immune poor B16 and CT26 preclinical models and paired biopsies of cancer patients that also demonstrated NK cell activation upon response to ICB. Our studies support βAlt as a biomarker that predicts response to ICB albeit in immune poor cancers, which has implications for the development of therapeutic strategies to increase the number of cancer patients who will benefit from immunotherapy.

Animal models for partial heart transplantation.

Partial heart transplantation delivers growing heart valve implants by transplanting the part of the heart containing the necessary heart valve only. In contrast to heart transplantation, partial heart transplantation spares the native ventricles. This has important implications for partial heart transplant biology, including the allowable ischemia time, optimal graft preservation, primary graft dysfunction, immune rejection, and optimal immunosuppression. Exploration of partial heart transplant biology will depend on suitable animal models. Here we review our experience with partial heart transplantation in rodents, piglets, and non-human primates. This review is based on our experience with partial heart transplantation using over 100 rodents, over 50 piglets and one baboon. Suitable animal models for partial heart transplantation include rodent heterotopic partial heart transplantation, piglet orthotopic partial heart transplantation, and non-human primate partial heart xenotransplantation. Rodent models are relatively cheap and offer extensive availability of research tools. However, rodent open-heart surgery is technically not feasible. This limits rodents to heterotopic partial heart transplant models. Piglets are comparable in size to children. This allows for open-heart surgery using clinical grade equipment for orthoptic partial heart transplantation. Piglets also grow rapidly, which is useful for studying partial heart transplant growth. Finally, nonhuman primates are immunologically most closely related to humans. Therefore, nonhuman primates are most suitable for studying partial heart transplant immunobiology and xenotransplantation. Animal research is a privilege that is contingent on utilitarian ethics and the 3R principles of replacement, reduction and refinement. This privilege allows the research community to seek fundamental knowledge about partial heart transplantation, and to apply this knowledge to enhance the health of children who require partial heart transplants.

Hydrogen Therapy Reverses Cancer-Associated Fibroblasts Phenotypes and Remodels Stromal Microenvironment to Stimulate Systematic Anti-Tumor Immunity.

Tumor microenvironment (TME) plays an important role in the tumor progression. Among TME components, cancer-associated fibroblasts (CAFs) show multiple tumor-promoting effects and can induce tumor immune evasion and drug-resistance. Regulating CAFs can be a potential strategy to augment systemic anti-tumor immunity. Here, the study observes that hydrogen treatment can alleviate intracellular reactive oxygen species of CAFs and reshape CAFs' tumor-promoting and immune-suppressive phenotypes. Accordingly, a controllable and TME-responsive hydrogen therapy based on a CaCO3 nanoparticles-coated magnesium system (Mg-CaCO3) is developed. The hydrogen therapy by Mg-CaCO3 can not only directly kill tumor cells, but also inhibit pro-tumor and immune suppressive factors in CAFs, and thus augment immune activities of CD4+ T cells. As implanted in situ, Mg-CaCO3 can significantly suppress tumor growth, turn the "cold" primary tumor into "hot", and stimulate systematic anti-tumor immunity, which is confirmed by the bilateral tumor transplantation models of "cold tumor" (4T1 cells) and "hot tumor" (MC38 cells). This hydrogen therapy system reverses immune suppressive phenotypes of CAFs, thus providing a systematic anti-tumor immune stimulating strategy by remodeling tumor stromal microenvironment.

Triptolide promotes differentiation of human monocytes into immunosuppressive MDSCs

BackgroundMyeloid-derived suppressor cells (MDSCs) negatively modulate immune activity. Prior investigations have shown much promise in using MDSCs-assisted immunotherapy for organ transplantation patients. Additionally, owing to its immunosuppressive activity, MDSCs can also be used to manage immune-associated disorders. MethodsGranulocyte-macrophage colony-stimulating factor (GM-CSF) was employed to stimulate myeloid progenitor cell differentiation. Triptolide (PG490) was introduced toward the later phases of in vitro MDSCs induction. Lastly, real-time PCR (RT-PCR) and flow cytometry were used to assess transcript expression and cell phenotype, and a mouse skin transplantation model was established to evaluate the MDSCs-mediated immune suppression in vivo. ResultsCo-stimulation with PG490 and GM-CSF potently induced myeloid-derived monocytes to form MDSCs, with remarkable immune-suppressive activity. The underlying mechanism involved downregulation of T cell proliferation, activation, enhancement of inflammatory cytokine release, as well as T cell conversion to Treg cells. PG490 strongly enhanced iNOS expression in MDSCs, and iNOS inhibition successfully reversed the immune-suppression. The PG490- and GM-CSF-induced MDSCs substantially extended survival duration of murine skin grafts, thereby validating their strong immune-suppressive activity in vivo. ConclusionsHerein, we presented a new approach involving MDSCs-based immunosuppression in vitro. PG490 and GM-CSF co-treatment strongly induced immuno-suppressive activity in MDSCs both in vitro and in vivo. Our findings highlight the promise of applying MDSCs-based therapy in clinical organ transplantation treatment.

Abstract B024: Development of HM-001 as a therapeutic drug for non-muscle invasive bladder cancer

Abstract HM-001 is a drug containing sodium chlorite as the active ingredient that is being developed as a drug for non-muscle invasive bladder cancer (NMIBC), and is currently undergoing physician-led clinical trials. It has been discovered that sodium chlorite generates radicals in an acidic environment, and phosphatidylserine on the surface of tumor cells acts as a Lewis acid to generate radicals. HM-001, like other anticancer drugs and BCG, is intended to be injected into the bladder, retained, and then excreted. GLP studies using the same administration method has been completed, and no toxic changes have been observed in human trial doses. The efficacy of HM-001 against NMIBC was evaluated using an orthotopic transplantation model of UM-UC-3, a bladder cancer cell line. In the model, cells were transplanted into the bladder of SCID mouse after epithelial removal with trypsin, 600, 800, 1,600, and 3,200 ppm of HM-001 were administered once a week, and the weight of the excised bladder was calculated. After 4 weeks, the tumor weight was calculated and the tumor weight suppression rate in the control group was evaluated. As a result, the medicinal efficacy was confirmed at concentrations of 800ppm or higher. On the other hand, the UM-UC-3 model is a commonly used model, but it mimics CIS (carcinoma in situ) and can only partially mimic NMIBC. That is, other models are needed to evaluate efficacy for low- and high-grade NMIBC other than CIS. Therefore, we established high-grade and low-grade PDX and evaluated the effectiveness of HM-001 against low- and high-grade PDX through ex vivo testing. First, patient-derived tissue was transplanted into SCID mice, allowed to grow, and then removed. After extraction, they were cut into 2 mm3 pieces, exposed to HM-001 at 800, 1600, and 3200 ppm for 2 hours, and then transplanted into SCID mice. As a result of comparing the tumor size after transplantation with the control group, a dose-dependent tumor regression effect was confirmed in high-grade and low-grade PDX. NMIBC is divided into low-, medium-, and high-risk categories, with different treatment methods and drugs used for each. In particular, low-grade forms are restricted to low- and intermediate-risk groups. The results of this study show that HM-001 is effective not only for high-risk (including CIS) NMIBC but also for low- and intermediate-risk (low-grade) NMIBC. Citation Format: Shinji Mima, Monta Sakaki, Noriaki Kiya, Atsunari Kawashima, Norio Nonomura, Chihaya Kakinuma. Development of HM-001 as a therapeutic drug for non-muscle invasive bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr B024.

Evaluating the Correlation Between Anteroposterior Diameter, Body Surface Area, and Height for Liver Transplant Donors and Recipients.

Small stature and female sex correlate to decreased deceased donor liver transplant (DDLT) access and higher waitlist mortality. However, efforts are being made to improve access and equity of allocation under the new continuous distribution (CD) system. Liver anteroposterior diameter (APD) is a method used by many centers to determine size compatibility for DDLT but is not recorded systematically, so it cannot be used for allocation algorithms. We therefore seek to correlate body surface area (BSA) and height to APD in donors and recipients and compare waitlist outcomes by these factors to support their use in the CD system. APD was measured from single-center DDLT recipients and donors with cross-sectional imaging. Linear, Pearson, and PhiK correlation coefficient were used to correlate BSA and height to APD. Competing risk analysis of waitlist outcomes was performed using United Network for Organ Sharing data. For 143 pairs, donor BSA correlated better with APD than height (PhiK = 0.63 versus 0.20). For recipient all comers, neither BSA nor height were good correlates of APD, except in recipients without ascites, where BSA correlated well (PhiK = 0.63) but height did not. However, among female recipients, BSA, but not height, strongly correlated to APD regardless of ascites status (PhiK = 0.80 without, PhiK = 0.70 with). Among male recipients, BSA correlated to APD only in those without ascites (PhiK = 0.74). In multivariable models, both BSA and height were predictive of waitlist outcomes, with higher values being associated with increased access, decreased delisting for death/clinical deterioration, and decreased living donor transplant (model concordance 0.748 and 0.747, respectively). Taken together, BSA is a good surrogate for APD and can therefore be used in allocation decision making in the upcoming CD era to offset size and gender-based disparities among certain candidate populations.