Heterotopic Abdominal Heart Transplantation Research Articles

Normothermic Ex Vivo Heart Perfusion With Exosomes From Human Umbilical Cord Mesenchymal Stem Cells Improves Graft Function in Donation After Circulatory Death Hearts.

This study aimed to investigate the cardioprotective effect of exosomes derived from human umbilical cord mesenchymal stem cells on donation after circulatory death (DCD) hearts preserved with normothermic ex vivo heart perfusion (EVHP) in a rat heart transplantation model. Thirty-two male Lewis rats were divided into 2 groups: the control group and the exosome group. The donor-heart rats were subjected to the DCD procedure by suffering a 15-min warm ischemia injury, subsequently preserved with EVHP for 90 min, and then transplanted into recipients via abdominal heterotopic heart transplantation. Vehicle or exosome was added into the perfusate of normothermic EVHP in the control or exosome group. We evaluated left ventricular graft function, myocardial inflammation, and myocardial apoptosis of the donor heart 1.5 h after heart transplantation. Furthermore, we investigate the alternation of myocardial gene expression in the donor hearts between both groups by transcriptome sequencing. The treatment with exosome significantly enhanced cardiac function through increasing left ventricular developed pressure, dp/dtmax, and dp/dtmin of DCD hearts at 90 min after heart transplantation compared with the control group. The myocardial cells in the exosome group exhibited an orderly arrangement without obvious edema. Furthermore, exosome added into perfusate in the exosome group significantly attenuated the level of inflammatory response and apoptosis. Transcriptome sequencing and RT-qPCR showed the phosphoinositide 3-kinase/protein kinase B pathway was activated after exosome treatment. Normothermic EVHP combined with exosome can be a promising and novel DCD heart preservation strategy, alleviating myocardial ischemia-reperfusion injury in the DCD heart.

Modified Heterotopic Abdominal Heart Transplantation and a Novel Aortic Regurgitation Model in Rats.

Over the past 50 years, many researchers have reported heterotopic abdominal heart transplantation in mice and rats, with some variations in the surgical technique. Modifying the transplantation procedure to strengthen the myocardial protection could prolong the ischemia time while preserving the donor's cardiac function. This technique's key points are as follows: transecting the donor's abdominal aorta before harvesting to unload the donor's heart; perfusing the donor's coronary arteries with a cold cardioplegic solution; and topical cooling of the donor's heart during the anastomosis procedure. Consequently, since this procedure prolongs the acceptable ischemia time, beginners can easily perform it and achieve a high success rate. Moreover, a new aortic regurgitation (AR) model was established in this work using a technique different from the existing one,which is created by inserting a catheter from the right carotid artery and puncturing the native aortic valve under continuous echocardiographic guidance. A heterotopic abdominal heart transplantation was performed using the novel AR model. In the protocol, after the donor's heart is harvested, a stiff guidewire is inserted into the donor's brachiocephalic artery and advanced toward the aortic root. The aortic valve is punctured by pushing the guidewire further even after the resistance is felt, thus inducing AR. It is easier to damage the aortic valve using this method than with the procedure described in the conventional AR model. Additionally, this novel AR model does not contribute to the recipient's circulation; therefore, this method is expected to produce a more severe AR model than the conventional procedure.

Antagonist of sphingosine 1-phosphate receptor 3 reduces cold injury of rat donor hearts for transplantation

Cold storage is widely used to preserve an organ for transplantation; however, a long duration of cold storage negatively impacts graft function. Unfortunately, the mechanisms underlying cold exposure remain unclear. Based on the sphingosine-1-phosphate (S1P) signal involved in cold tolerance in hibernating mammals, we hypothesized that S1P signal blockage reduces damage from cold storage. We used an in vitro cold storage and rewarming model to evaluate cold injury and investigated the relationship between cold injury and S1P signal. Compounds affecting S1P receptors (S1PR) were screened for their protective effect in this model and its inhibitory effect on S1PRs was measured using the NanoLuc Binary Technology (NanoBiT)-β-arrestin recruitment assays. The effects of a potent antagonist were examined via heterotopic abdominal rat heart transplantation. The heart grafts were transplanted after 24-hour preservation and evaluated on day 7 after transplantation. Cold injury increased depending on the cold storage time and was induced by S1P. The most potent antagonist strongly suppressed cold injury consistent with the effect of S1P deprivation in vitro. In vivo, this antagonist enabled 24-hour preservation, and drastically improved the beating score, cardiac size, and serological markers. Pathological analysis revealed that it suppressed the interstitial edema, inflammatory cell infiltration, myocyte lesion, TUNEL-positive cell death, and fibrosis. In conclusion, S1PR3 antagonist reduced cold injury, extended the cold preservation time, and improved graft viability. Cold preservation strategies via S1P signaling may have clinical applications in organ preservation for transplantation and contribute to an increase in the donor pool.

337.2: Comparison of Hypothermic Static and Normothermic Ex-situ Donor Heart Preservation in Heterotopic Heart Transplantation With the Murine Model

Introduction and Background: Hypothermic static and Normothermic ex-situ preservation methods are the most widely used preservation technique worldwide. While cold static storage is associated with subsequent ischemic injury, Normothermic perfusion preservation has the potential to elongate preservation time with less ischemia. The current study compares the hypothermic and normothermic preservation methods in terms of graft performance, morphologic changes, and acute immune response in an experimental model. Materials and Method: Twenty-five rats underwent heterotopic abdominal heart transplantation after two hours of donor heart hypothermic storage (HT group; n=10) or normothermic ex-situ preservation (NT group; n=15). Blood samples were obtained just before and after 4-hours of implantation to analyze surface markers of immune cells (CD4, CD8, CD161, CD45R). ECG and Echocardiography were performed before harvesting and after implantation. Hearts were extracted after four hours of implantation for Hematoxylin-Eosin (HE) and TUNEL-staining, and recipient rats were euthanized. Results: 19 (76%) rats successfully survived after implantation (HT group: 100%, NT group: 60%). The mean ischemic time of the donor heart was 162.7±8.34 minutes in the HT group and 45±3.7 minutes in the NT group. The NT group showed no significant change in the heart rate before and after implantation but significantly decreased in the first hour of implantation in the HT group (259.5±24.3rpm) and normalized at 3 hours (338.3±34.1rpm). Ejection fraction and fractional shortening significantly decreased after implantation in both groups but were less significant in the NT group (P=0.001). Granulocyte was less significantly increased in the NT group compared to the HT group after the experiment (p=0.037). Although the gross structure was well preserved in both groups in HE-staining, the number of TUNEL positive cells was significantly higher in the HT group. Conclusions: Our findings suggest that normothermic ex-situ preservation is associated with well-preserved donor hearts but similar recipient immune response in comparison with hypothermic static preservation.

Abstract P3069: The Impact Of Lymphatic Vasculature Post-Cardiac Transplantation On Allograft Function, Fibrotic Remodeling, And Lymphatic Drainage

Lymphatic drainage inherently modulates cardiac function by maintaining the immune response and tissue-fluid homeostasis. During cardiac transplantation, the lymphatic collecting vessels are severed at the time of donor heart excision and not surgically reconstructed in the recipient. We hypothesize severed cardiac lymphatics contribute to transplant rejection and reduced cardiac function by influencing myocardial edema and immune cell transit. Methods: A heterotopic abdominal heart transplant (HAHT) rodent model permitted the immunologic evaluation of transplant rejection as supported in past literature. Echocardiography confirmed allograft survival via active contraction, while histologic quantification of lymphatic vessels and fibrosis were obtained for native and transplanted rodent hearts (n=3). Lymphatic drainage was assessed via intramyocardial injection of fluorescein isothiocyanate (FITC)-dextran. Results: Electrocardiographic impulses detected during the echocardiograms revealed additional QRS complexes attributed to contractions of the transplanted hearts. Histologic analysis of fibrosis in rodent allografts at an early timepoint exhibited increases in total tissue accumulation (1.48 – 5.15 fold) and significant increases in various focal regions (left ventricle, ***p < 0.001; interventricular septum, ****p < 0.0001) compared to the native hearts. Furthermore, large amounts of cellular infiltrate and marginal increases in cardiac diameter (1.10 – 1.42 fold) were observed in the transplants. While the scarcity of immunofluorescence signal for lymphatic markers has caused cardiac lymphatic quantification to be inconclusive, evaluation of lymphatic transport revealed fluctuating time-dependent circulating FITC levels (0.002 - 0.010 mg/mL; *p < 0.05) suggesting multi-teared compartmental release properties between the microcirculatory system, lymphatic system, and cardiac tissue. Conclusion: The HAHT rodent model provides a promising modality to assess both lymphatic transport and transplant rejection. Moreover, these studies will progress understanding of transplant rejection’s pathological intricacies and provide the groundwork for lymphangiogenic-based therapeutic intervention.

Blood Circuit Reconstruction in an Abdominal Mouse Heart Transplantation Model.

The surgical technique of heterotopic abdominal heart transplantation in mice is a standard model for research in transplantation immunology. Here, the established technique for a modified blood circuit reconstruction in a heterotopic abdominal heart transplantation model is presented. This method uses the intrathoracic inferior vena cava (IIVC) instead of the pulmonary artery of the donor heart for the anastomosis to the inferior vena cava of the recipient. It is facilitating and improving success rates for abdominal heart transplantation in mice.

PJ34, a PARP1 inhibitor, attenuates acute allograft rejection after murine heart transplantation via regulating the CD4+ T lymphocyte response.

Acute allografts rejection is the most important factor causing allograft disability for many patients undergoing organ transplantation. PJ34, which is a specific inhibitor of poly(ADP-ribose) polymerase 1, is involved in immune regulation, may be effective in preventing acute cardiac rejection. We performed the models of abdominal heterotopic heart transplantation. PJ34 was injected intraperitoneally daily (20mg/kg/day) starting the day after surgery. The severity of rejection was determined by histology. The mRNA expression levels of cytokines and transcription factors in the grafts were measured by quantitative polymerase chain reaction (qPCR). The proportion and number of T-cell subpopulations in the spleens were analyzed by flow cytometry. In vitro, the effect of PJ34 on allogeneic responses was investigated. We found treatment with PJ34 prolonged allograft survival compared with normal saline treatment. Compared with the control group, PJ34 treatment reduced the proportion of CD4+ IFN-γ+ and CD4+ IL-17A+ cells and increased the percent of CD4+ IL-4+ and CD4+ Foxp3+ cells in the spleens. In vitro, PJ34 treatment significantly inhibited the mRNA levels of IFN-γ and IL-17A and promoted the mRNA levels of TGF-β and FOXP-3 in activated CD4+ T cells. Modulating the CD4+ T lymphocyte response with PJ34 could attenuate acute allografts rejection after murine heart transplantation. These findings indicate that PARP1 may be a promising therapeutic target to attenuate acute cardiac allograft rejection.

Targeted galectin-7 inhibition with ultrasound microbubble targeted gene therapy as a sole therapy to prevent acute rejection following heart transplantation in a Rodent model

BackgroundDespite significant advances in transplantation, acute cellular rejection (AR) remains a major obstacle that is most prevalent in the first months post heart transplantation (HT). Current treatments require high doses of immunosuppressive drugs followed by maintenance therapies that have systemic side effects including early infection. In this study, we attempted to prevent AR with a myocardial-targeted galectin-7-siRNA delivery method using cationic microbubbles (CMBs) combined with ultrasound targeted microbubble destruction (UTMD) to create local immunosuppression in a rat abdominal heterotopic heart transplantation acute rejection model. Methods and resultsGalectin-7-siRNA (siGal-7) bound to CMBs were synthesized and effective ultrasound-targeted delivery of siGal-7 into target cells confirmed in vitro. Based on these observations, three transplant rat models were tested：①isograft (ISO); ② Allograft (ALLO) +UTMD; and ③ALLO + PBS. UTMD treatments were administered at 1, 3, 5, 7 days after HT. Galectin 7 expression was reduced by 50% compared to ALLO + PBS (p < 0.005), and this was associated with significant reductions in both galectin 7 and Interleukin-2 protein levels (p < 0.001). The ALLO + UTMD group had Grade II or less inflammatory infiltration and myocyte damage in 11/12 rats using International Society For Heart and Lung Transplantation grading, compared to 0/12 rats with this grading in the ALLO + PBS group at 10 days post HT (p < 0.001). ConclusionsUltrasound-targeted galectin-7-siRNA knockdown with UTMD can prevent acute cellular rejection in the early period after allograft heart transplantation without the need for systemic immunosuppression. Key wordsMicrobubble, Acute Rejection, Heart Transplantation, Galectin-7, RNA.

Combined abdominal heterotopic heart and aorta transplant model in mice.

Allograft vasculopathy (AV) remains a major obstacle to long-term allograft survival. While the mouse aortic transplantation model has been proven as a useful tool for study of the pathogenesis of AV, simultaneous transplantation of the aorta alongside the transplantation of another organ may reveal more clinically relevant mechanisms that contribute to the pathogenesis of chronic allograft rejection. Therefore, we developed a combined abdominal heart and aorta transplantation model in mice which benefits from reducing animal and drug utilization, while providing an improved model to study the progressive nature of AV. The middle of the infrarenal aorta of the recipient mouse was ligatured between the renal artery and its bifurcation. Proximal and distal aortotomies were performed at this site above and below the ligature, respectively, for the subsequent anastomoses of the donor aorta and heart grafts to the recipient infrarenal aorta in an end-to-side fashion. The distal anastomotic site of the recipient infrarenal aorta was connected with the outlet of the donor aorta. Uniquely, the proximal anastomotic site on the recipient infrarenal aorta was shared to connect with both the inlet of the donor aorta and the inflow tract to the donor heart. The outflow tract from the donor heart was connected to the recipient inferior vena cava (IVC). The median times for harvesting the heart graft, aorta graft, recipient preparation and anastomosis were 11.5, 8.0, 9.0 and 40.5 min, respectively, resulting in a total median ischemic time of 70 min. The surgery survival rate was more than 96% (29/30). Both the syngeneic C57Bl/6 aorta and heart grafts survived more than 90 days in 29 C57Bl/6 recipients. Further, Balb/c to C57Bl/6 allografts treated with anti-CD40L and CTLA4.Ig survived more than 90 days with a 100% (3/3) survival rate. (3/3). This model is presented as a new tool for researchers to investigate transplant immunology and assess immunosuppressive strategies. It is possible to share a common anastomotic stoma on the recipient abdominal aorta to reconstruct both the aorta graft entrance and heart graft inflow tract. This allows for the study of allogeneic effects on both the aorta and heart from the same animal in a single survival surgery.

Inhibition of cardiac allograft rejection in mice using interleukin-35-modified mesenchymal stem cells.

Interleukin-35 (IL-35) is a cytokine recently discovered to play a potent immunosuppressive role by intensifying the functions of regulatory T cells and inhibiting the proliferation and functions of T helper 1 and T helper 17 cells. Mesenchymal stem cells (MSCs) have recently emerged as promising candidates for cell-based immune therapy, and our previous study showed that IL-35 gene modification can effectively enhance the therapeutic effect of MSCs in vitro. In this study, we isolated adipose tissue-derived MSCs in vitro and infected them with lentiviral vectors overexpressing the IL-35 gene, thereby creating IL-35-MSCs. Subsequently, IL-35-MSCs were then injected into mice of the allogeneic heterotopic abdominal heart transplant model to determine their effect on allograft rejection. The results showed that IL-35-MSCs could continuously secrete IL-35 in vivo and in vitro, successfully alleviate allograft rejection and prolong graft survival. In addition, compared to MSCs, IL-35-MSCs showed a stronger immunosuppressive ability and further reduced the percentage of Th17 cells, increased the proportion of CD4+ Foxp3+ T cells, and regulated Th1/Th2 balance in heart transplant mice. These findings suggest that IL-35-MSCs have more advantages than MSCs in inhibiting graft rejection and may thus provide a new approach for inducing immune tolerance during transplantation.

Eugenol protects the transplanted heart against ischemia/reperfusion injury in rats by inhibiting the inflammatory response and apoptosis.

The aim of the present study was to investigate the protective effect of eugenol on the transplanted heart and explore its mechanisms of action. Male Sprague-Dawley rats were randomly divided into a sham group (n=10), a eugenol group (n=10 pairs, donors and recipients) and a control group (n=10 pairs, donors and recipients). The recipients in the eugenol group received an intraperitoneal injection of eugenol (20 mg/kg/day). The sham group and the control group received equal volumes of physiological saline by intraperitoneal injection. After 15 days the recipients in the control and eugenol groups underwent abdominal heterotopic heart transplantation, while the sham group received only a coeliotomy. The orthotopic hearts in the sham group and the heterotopic hearts in the eugenol and control groups, as well as the peripheral blood samples from all three groups were taken 3 h post operation for biochemical, histopathological, molecular and apoptosis analyses. Compared with the control group, the eugenol treatment significantly reduced the myocardial malondialdehyde content, serum cardiac troponin I, creatine kinase-MB, tumor necresis factor-α and interleukin-6 levels (P<0.05) and significantly alleviated myocardial injury. Western blot analysis demonstrated that the protein expression of cleaved Poly (ADP-ribose) polymerase 1, BAX and active caspase-3 in the eugenol group were significantly decreased, while B-cell lymphoma 2 expression was significantly increased compared with the control group (P<0.05). The myocardial apoptosis rate of the eugenol group was significantly decreased compared with the control group (P<0.05). In conclusion eugenol treatment significantly reduced myocardial injury and demonstrated protective effects for the transplanted heart.

Isovolumic loading of the failing heart by intraventricular placement of a spring expander attenuates cardiac atrophy after heterotopic heart transplantation.

Cardiac atrophy is the most common complication of prolonged application of the left ventricle (LV) assist device (LVAD) in patients with advanced heart failure (HF). Our aim was to evaluate the course of unloading-induced cardiac atrophy in rats with failing hearts, and to examine if increased isovolumic loading obtained by intraventricular implantation of an especially designed spring expander would attenuate this process. Heterotopic abdominal heart transplantation (HTx) was used as a rat model of heart unloading. HF was induced by volume overload achieved by creation of the aorto-caval fistula (ACF). The degree of cardiac atrophy was assessed as the weight ratio of the heterotopically transplanted heart (HW) to the control heart. Isovolumic loading was increased by intraventricular implantation of a stainless steel three-branch spring expander. The course of cardiac atrophy was evaluated on days 7, 14, 21, and 28 after HTx. Seven days unloading by HTx in failing hearts sufficed to substantially decrease the HW (−59 ± 3%), the decrease progressed when measured on days 14, 21, and 28 after HTx. Implantation of the spring expander significantly reduced the decreases in whole HW at all the time points (−39 ± 3 compared with −59 ± 3, −52 ± 2 compared with −69 ± 3, −51 ± 2 compared with –71 ± 2, and −44 ± 2 compared with −71 ± 3%, respectively; P<0.05 in each case). We conclude that the enhanced isovolumic heart loading obtained by implantation of the spring expander attenuates the development of unloading-induced cardiac atrophy in the failing rat heart.

Immune modulation by silencing CD80 and CD86 production in dendritic cells using small hairpin RNA to reduce heart transplant rejection

RNA interference (RNAi) plays a potential role in organ transplantation. Small hairpin RNA (shRNA) is an artificial RNA molecule with a tight hairpin turn that can be used to silence the expression of a target gene. We constructed shRNA targeting on the cluster of differentiation 80 (CD80, B7-1) and the cluster of differentiation 86 (CD86, B7-2) and transfected it into dendritic cells (DCs). Fluorescence real-time PCR and flow cytometry confirmed the gene-silencing effect. Interleukin-2 (IL-2) mRNA expression level decreased in T cells that were cocultured with pB7-shRNA-transfected DCs. For in-vivo experiment, we built mice models of abdominal heterotopic heart transplantation and transfused the models with pB7-shRNA-transfected donor-derived DCs. The survival time of the transplanted heart increased; the grade of organ rejection decreased. IL-2 mRNA expression level decreased and it was positively correlated with the grade of organ rejection.

Effects of increased myocardial tissue concentration of myristic, palmitic and palmitoleic acids on the course of cardiac atrophy of the failing heart unloaded by heterotopic transplantation.

The present experiments were performed to evaluate if increased heart tissue concentration of fatty acids, specifically myristic, palmitic and palmitoleic acids that are believed to promote physiological heart growth, can attenuate the progression of unloading-induced cardiac atrophy in rats with healthy and failing hearts. Heterotopic abdominal heart transplantation (HT(x)) was used as a model for heart unloading. Cardiac atrophy was assessed from the ratio of the native- to-transplanted heart weight (HW). The degree of cardiac atrophy after HT(x) was determined on days 7, 14, 21 and 28 after HT(x) in recipients of either healthy or failing hearts. HT(x) of healthy hearts resulted in 23+/-3, 46+/-3, 48+/-4 and 46+/-4 % HW loss at the four time-points. HT(x) of the failing heart resulted in even greater HW losses, of 46+/-4, 58+/-3, 66+/-2 and 68+/-4 %, respectively (P<0.05). Activation of "fetal gene cardiac program" (e.g. beta myosin heavy chain gene expression) and "genes reflecting cardiac remodeling" (e.g. atrial natriuretic peptide gene expression) after HT(x) was greater in failing than in healthy hearts (P<0.05 each time). Exposure to isocaloric high sugar diet caused significant increases in fatty acid concentrations in healthy and in failing hearts. However, these increases were not associated with any change in the course of cardiac atrophy, similarly in healthy and post-HT(x) failing hearts. We conclude that increasing heart tissue concentrations of the fatty acids allegedly involved in heart growth does not attenuate the unloading-induced cardiac atrophy.

Abstract 21087: Coronary Reperfusion Ameliorates the Deleterious Effect of Mechanical Unloading on Infarct Size and Interstitial Fibrosis After Acute Myocardial Infarction

Background: Contemporary studies show that myocardial fibrosis worsens after mechanical unloading with left ventricular assist devices (LVADs). The exact mechanism underlying this phenomenon remains unknown. Mechanical unloading has however been associated with a reduction in microvascular lumenal diameter in the failing heart, suggesting a link with negative auto-regulatory effects on the collateral circulation. We hypothesise that coronary reperfusion after myocardial infarction ameliorates the deleterious effect of mechanical unloading on infarct size and interstitial fibrosis. Methods: Syngeneic male Lewis rats weighing 200 to 300g were studied. Myocardial infarction – acute (AMI) and chronic (CMI) - was induced by LAD ligation. Two groups were generated: a permanent ligation group (AMI and CMI) and a reperfusion - coronary circulation restored after 90 minutes - group (AMI/R and CMI/R). In each group hearts were either loaded (L) or unloaded (U). In the loaded subgroup, rats were recovered after coronary ligation. In the unloaded subgroup, the infarcted hearts were explanted after 90 minutes and transplanted into the abdomen of healthy recipients via heterotopic abdominal heart transplantation. Hearts were explanted on day 2, day 7, and 16wks. The recipient’s heart acted as control. Histological analysis and western blotting for αSMA and TGF-β1 (markers of fibrosis) were completed. Results: Ninety rats were studied. There was a significant increase in infarct ratio (IR) - infarct size/area at risk-, and interstitial fibrosis (IF) after mechanical unloading in the permanent ligation group at day 2 (AMI-L vs AMI-U p = 0.0073 (IR) and p = 0.0012 (IF)) and day 7 (AMI-L vs AMI-U p = 0.0166 (IR) and p = 0.0363 (IF)). After coronary reperfusion, there was no increase in IR or IF with mechanical unloading. At 16wks however, this protective effect of reperfusion was lost (CMI/R-L vs CMI/R-U p = 0.004 (IR) and p = 0.0024 (IF)). The expression profiles of αSMA and TGF-β1 correlated with the results above. Conclusion: These data suggest an association between the revascularisation of a less auto-regulated vessel and amelioration of the deleterious effect of mechanical unloading on the extracellular matrix with implications for LVAD induced recovery.

Heterotopic Abdominal Rat Heart Transplantation as a Model to Investigate Volume Dependency of Myocardial Remodeling.

Heterotopic abdominal rat heart transplantation has been extensively used to investigate ischemic-reperfusion injury, immunological consequences during heart transplantations and also to study remodeling of the myocardium due to volume unloading. We provide a unique review on the latter and present a summary of the experimental studies on rat heart transplantation to illustrate changes that occur to the myocardium due to volume unloading. We divided the literature based on whether normal or failing rat heart models were used. This analysis may provide a basis to understand the physiological effects of mechanical circulatory support therapy.

Development of a Vascularized Heterotopic Neonatal Rat Heart Transplantation Model

Background/Purpose: Rodent adult-to-adult heterotopic heart transplantation is a well-established animal model, and the detailed surgical technique with several modifications has been previously described. In immature donor organ transplantation, however, the surgical technique needs to be revised given the smaller size and fragility of the donor graft. Here, we report our surgical technique for heterotopic abdominal (AHTx) and femoral (FHTx) neonatal rat heart transplantation based on an experience of over 300 cases. Methods: Heterotopic heart transplantation was conducted in syngeneic Lewis rats. Neonatal rats (postnatal day 2-4) served as donors. AHTx was performed by utilizing the conventional adult-to-adult transplant method with specific modifications for optimal aortotomy and venous anastomosis. In the FHTx, the donor heart was vascularized by connecting the donor's aorta and pulmonary artery to the recipient's right femoral artery and vein, respectively, in an end-to-end manner. A specifically fashioned butterfly-shaped rubber sheet was used to align the target vessels properly. The transplanted graft was visually assessed for its viability and was accepted as a technical success when the viability met specific criteria. Successfully transplanted grafts were subject to further postoperative evaluation. Forty cases (AHTx and FHTx; n = 20 each) were compared regarding perioperative parameters and outcomes. Results: Both models were technically feasible (success rate: AHTx 75% vs. FHTx 70%) by refining the conventional heterotopic transplant technique. Injury to the fragile donor aorta and congestion of the graft due to suboptimal venous connection were predominant causes of failure, leading to refractory bleeding and poor graft viability. Although the FHTx required significantly longer operation time and graft ischemic time, the in situ graft viabilities were comparable. The FHTx provided better postoperative monitoring as it enabled daily graft palpation and better echocardiographic visualization. Conclusions: We describe detailed surgical techniques for AHTx and FHTx while addressing neonatal donor-specific issues. Following our recommendations potentially reduces the learning curve to achieve reliable and reproducible results with these challenging animal models.

Molecular immunology profiles of monkeys following xenografting with the islets and heart of α-1,3-galactosyltransferase knockout pigs.

Effective immunosuppression strategies and genetically modified animals have been used to prevent hyperacute and acute xenograft rejection; however, the underlying mechanisms remain unknown. In this study, we evaluated the expression of a comprehensive set of immune system-related genes (89 genes, including five housekeeping genes) in the blood of cynomolgus monkeys (~5 yr old) used as graft recipients, before and after the xenografting of the islets and heart from single and double α-1,3-galactosyltransferase (GalT) knockout (KO) pigs (<6 weeks old). The immunosuppressive regimen included administration of cobra venom factor, anti-thymocyte globulin, rituximab, and anti-CD154 monoclonal antibodies to recipients before and after grafting. Islets were xenografted into the portal vein in type 1 diabetic monkeys, and the heart was xenografted by heterotopic abdominal heart transplantation. Genes from recipient blood were analyzed using RT(2) profiler PCR arrays and the web-based RT(2) profiler PCR array software v.3.5. Recipients treated with immunosuppressive agents without grafting showed significant downregulation of CCL5, CCR4, CCR6, CD4, CD40LG, CXCR3, FASLG, CXCR3, FOXP3, GATA3, IGNG, L10, IL23A, TRAF6, MAPK8, MIF, STAT4, TBX21, TLR3, TLR7, and TYK2 and upregulation of IFNGR1; thus, genes involved in protection against viral and bacterial infection were downregulated, confirming the risk of infection. Notably, C3-level control resulted in xenograft failure within 2 days because of a 7- to 11-fold increase in all xenotransplanted models. Islet grafting using single GalT-KO pigs resulted in upregulation of CXCL10 and MX1, early inflammation, and acute rejection-associated signals at 2 days after xenografting. We observed at least 5-fold upregulation in recipients transplanted with islets grafts from single (MX1) or double (C3, CCR8, IL6, IL13, IRF6, CXCL10, and MX1) GalT-KO pigs after 77 days; single GalT-KO incurred early losses owing to immune attacks. Our results suggest that this novel, simple, non-invasive, and time-efficient procedure (requiring only 1.5 ml blood) for evaluating graft success, minimizing immune rejection, and blocking infection.

HMGB1 blockade differentially impacts pulmonary inflammation and defense responses in poly(I:C)/LPS-exposed heart transplant mice.

A large number of recipients are in a compromised immune defense condition because of the routine application of immunosuppressive regimens after heart transplantation. Our previous work demonstrated that blockade of high-mobility group box 1 (HMGB1) prolongs the graft survival. Whether and how HMGB1 blockade impacts respiratory responses against pathogen-like challenge in organ transplant recipients when it improves cardiac graft are not elucidated. At the present study, after abdominal heterotopic heart transplantation, the recipient mice were treated with HMGB1 mAb, and then challenged with poly(I:C) or LPS intratracheally on day 7 post transplantation. We found that the level of bronchoalveolar lavage (BAL) HMGB1 was elevated after heart transplantation, and aggravated responses to respiratory tract poly(I:C)/LPS challenge were observed. HMGB1 neutralizing mAb treatment in poly(I:C)-challenged recipient mice alleviated pulmonary histopathological changes, neutrophil infiltration and inflammatory cytokine release, but unaffected the level of IFN-β, the distribution of CD11b(+)CD27(+)/CD11b(+)CD27(-) NK cell subsets, and CD8(+) T cell responses. In LPS-exposed recipient mice, HMGB1 mAb treatment ameliorated pulmonary inflammatory damage and enhanced the phagocytosis of phagocytic cells. Thus, this study may establish a basis for the application of HMGB1 blockade to improve the outcomes of heart transplant recipients because HMGB1 inhibition ameliorates pulmonary inflammation, but maintains defense-associated responses.

ERK5 promotes TLR2-dependent up-regulation of inflammatory mediator expression induces by global myocardial ischemia

Global myocardial ischemia and reperfusion [I/R] injury is predominantly associated with heart transplant and coronary artery bypass graft (CABG) surgery. Toll-like receptor-2 (TLR2) is a pivotal pathogen recognition receptor that has a key role in inflammation and injury. The proinflammatory role for ERK5 downstream of TLR2 in global myocardial I/R has not been reported previously. The aim of this study was to investigate to what extent inflammatory stimuli modify the expression by ERK5 of TLR2. Global myocardial I/R was induced in male TLR2+/+ and TLR2−/− mice using heterotopic abdominal heart transplantation model that allows to subject donor hearts to global hypothermic ischemia and blood reperfusion, which very closely stimulates I/R conditions associated with cardiac surgical operations. The results show that inhibition or siRNA knockdown of ERK5 reduces the TLR2-dependent activation of expression of cytokines, attenuated myocardial injury, less oxidative stress and decreased NF-κB activation and indicating that ERK5 promotes cytokine expression downstream of TLR2. We have identified novel aspects of TLR2 signaling in cold myocardial I/R, including that ERK5 activity is required for TLR2 activation.