Beneficial effects of perioperative low-dose inhaled carbon monoxide on pulmonary allograft survival in MHC-inbred CLAWN miniature swine

The Effects of Volatile Anesthetics on Lung Ischemia-Reperfusion Injury: Basic to Clinical Studies

Case reports from as early as the 1970s have shown that intravenous injection of even a small dose of volatile anesthetics result in fatal lung injury. Direct contact between volatile anesthetics and pulmonary vasculature triggers chemical damage in the vessel walls. A wide variety of factors are involved in lung ischemia-reperfusion injury (LIRI), such as pulmonary endothelial cells, alveolar epithelial cells, alveolar macrophages, neutrophils, mast cells, platelets, proinflammatory cytokines, and surfactant. With a constellation of factors involved, the assessment of the protective effect of volatile anesthetics in LIRI is difficult. Multiple animal studies have reported that with regards to LIRI, sevoflurane demonstrates an anti-inflammatory effect in immunocompetent cells and an anti-apoptotic effect on lung tissue. Scattered studies have dismissed a protective effect of desflurane against LIRI. While a single-center randomized controlled trial (RCT) found that volatile anesthetics including desflurane demonstrated a lung-protective effect in thoracic surgery, a multicenter RCT did not demonstrate a lung-protective effect of desflurane. LIRI is common in lung transplantation. One study, although limited due to its small sample size, found that the use of volatile anesthetics in organ procurement surgery involving "death by neurologic criteria" donors did not improve lung graft survival. Future studies on the protective effect of volatile anesthetics against LIRI must examine not only the mechanism of the protective effect but also differences in the effects of different types of volatile anesthetics, their optimal dosage, and the appropriateness of their use in the event of marked alveolar capillary barrier damage.

Heme Oxygenase-1 in liver transplant ischemia-reperfusion injury: From bench-to-bedside

Hepatic ischemia-reperfusion injury (IRI), a major risk factor for early allograft dysfunction (EAD) and acute or chronic graft rejection, contributes to donor organ shortage for life-saving orthotopic liver transplantation (OLT). The graft injury caused by local ischemia (warm and/or cold) leads to parenchymal cell death and release of danger-associated molecular patterns (DAMPs), followed by reperfusion-triggered production of reactive oxygen species (ROS), activation of inflammatory cells, hepatocellular damage and ultimate organ failure. Heme oxygenase 1 (HO-1), a heat shock protein-32 induced under IR-stress, is an essential component of the cytoprotective mechanism in stressed livers. HO-1 regulates anti-inflammatory responses and may be crucial in the pathogenesis of chronic diseases, such as arteriosclerosis, hypertension, diabetes and steatosis. An emerging area of study is macrophage-derived HO-1 and its pivotal intrahepatic homeostatic function played in IRI-OLT. Indeed, ectopic hepatic HO-1 overexpression activates intracellular SIRT1/autophagy axis to serve as a key cellular self-defense mechanism in both mouse and human OLT recipients. Recent translational studies in rodents and human liver transplant patients provide novel insights into HO-1 mediated cytoprotection against sterile hepatic inflammation. In this review, we summarize the current bench-to-bedside knowledge on HO-1 molecular signaling and discuss their future therapeutic potential to mitigate IRI in OLT.

The Protective Effects of Carbon Monoxide Against Hepatic Warm Ischemia-Reperfusion Injury in MHC-Inbred Miniature Swine

BACKGROUND

The development of treatment strategies to protect against ischemia-reperfusion injury (IRI) to livers is important not only for liver surgeries but also in regard to increasing the utilization of livers from marginal donors. In this study, we examined whether inhalational carbon monoxide (CO) therapy reduced IRI after a 45-min (min) warm ischemia (WI) in a miniature swine model.

MATERIALS AND METHODS

Six CLAWN miniature swine underwent a 45-min hepatic WI induced by clamping the portal vein and proper hepatic artery. Three animals were subjected to control conditions while the remaining three were treated with CO inhalation for a total of 345-min, including 120-min after reperfusion to maintain a concentration of CO-Hb under 15% (CO-treated group). IRI of the livers was evaluated by liver function tests, serum pro-inflammatory cytokines, and liver biopsies.

RESULTS

All controls had statistically significant increased levels of liver enzymes compared to the CO-treated group (p < 0.05). In controls, liver biopsies at 2 h after reperfusion showed marked histological changes including diffuse hemorrhage, congestion, necrosis, vacuolization, and neutrophil infiltration with apoptosis. In contrast, the CO-treated group showed less obvious or only minimal histological changes. Furthermore, increases in high-mobility group box 1, TNF-α, and IL-6 in sera that were induced by IRI in controls were markedly inhibited by the CO treatment.

CONCLUSION

We demonstrated that low-dose CO inhalation reduces hepatic warm IRI, potentially through downregulation of pro-inflammatory mediators and activation of anti-apoptotic pathways. To our knowledge, this is the first report demonstrating CO inhalation attenuated hepatic IRI following WI in a large animal model.

Development of an immunodeficient pig model allowing long-term accommodation of artificial human vascular tubes

Before they are used in the clinical setting, the effectiveness of artificially produced human-derived tissue-engineered medical products should be verified in an immunodeficient animal model, such as severe combined immunodeficient mice. However, small animal models are not sufficient to evaluate large-sized products for human use. Thus, an immunodeficient large animal model is necessary in order to properly evaluate the clinical efficacy of human-derived tissue-engineered products, such as artificial grafts. Here we report the development of an immunodeficient pig model, the operational immunodeficient pig (OIDP), by surgically removing the thymus and spleen, and creating a controlled immunosuppressive protocol using a combination of drugs commonly used in the clinical setting. We find that this model allows the long-term accommodation of artificial human vascular grafts. The development of the OIDP is an essential step towards a comprehensive and clinically relevant evaluation of human cell regeneration strategies at the preclinical stage.

The development of tissue-engineered vascular grafts heavily relies on the availability of large animal models that allow long-term assessment of graft patency. Here Itoh et al. propose a novel model of immunodeficient pigs that allows long-term accommodation of human cell-derived three-dimensional bioprinted vascular tubes.

GalT-KO pig lungs are highly susceptible to acute vascular rejection in baboons, which may be mitigated by transgenic expression of hCD47 on porcine blood vessels

BACKGROUND

Despite recent progress in survival times of xenografts in non-human primates, there are no reports of survival beyond 5 days of histologically well-aerated porcine lung grafts in baboons. Here, we report our initial results of pig-to-baboon xeno-lung transplantation (XLTx).

METHODS

Eleven baboons received genetically modified porcine left lungs from either GalT-KO alone (n = 3), GalT-KO/humanCD47(hCD47)/hCD55 (n = 3), GalT-KO/hD47/hCD46 (n = 4), or GalT-KO/hCD39/hCD46/hCD55/TBM/EPCR (n = 1) swine. The first 2 XLTx procedures were performed under a non-survival protocol that allowed a 72-hour follow-up of the recipients with general anesthesia, while the remaining 9 underwent a survival protocol with the intention of weaning from ventilation.

RESULTS

Lung graft survivals in the 2 non-survival animals were 48 and >72 hours, while survivals in the other 9 were 25 and 28 hours, at 5, 5, 6, 7, >7, 9, and 10 days. One baboon with graft survival >7 days, whose entire lung graft remained well aerated, was euthanized on POD 7 due to malfunction of femoral catheters. hCD47 expression of donor lungs was detected in both alveoli and vessels only in the 3 grafts surviving >7, 9, and 10 days. All other grafts lacked hCD47 expression in endothelial cells and were completely rejected with diffuse hemorrhagic changes and antibody/complement deposition detected in association with early graft loss.

CONCLUSIONS

To our knowledge, this is the first evidence of histologically viable porcine lung grafts beyond 7 days in baboons. Our results indicate that GalT-KO pig lungs are highly susceptible to acute humoral rejection and that this may be mitigated by transgenic expression of hCD47.

Lung xenotransplantation

PURPOSE OF REVIEW

This review describes the most recent progress in xeno lung transplantation (XLTx) to date. It describes the potential mechanisms of early xeno lung graft loss, as well as the latest therapeutic strategies to overcome them.

RECENT FINDINGS

Using ex-vivo perfusion models of porcine lungs with human blood, the use of genetically modified pig lungs along with novel pharmaceutical approaches has recently been studied. Strategies that have demonstrated improved lung survival include the knockout of known xenoantigens (GalTKO and N-glycolylneuraminic acid-KO), genes that regulate complement activation (hCD46 and hCD55), as well as the inflammation/coagulation cascade (human leukocyte antigen-E, human thrombomodulin, human endothelial protein C receptor, hCD47, hCD39, hCD73 and heme oxygenase-1). Furthermore, pharmacologic interventions including the depletion of pulmonary intravascular macrophages or von Willebrand factor, inhibition of thromboxane synthase and blockade of histamine receptors have also demonstrated protective effects on xeno lung grafts. Using in-vivo pig to nonhuman primate lung transplant models, these approaches have been shown to extend pulmonary xenograft survival to 5 days.

SUMMARY

The development of new multitransgenic GalTKO pigs has demonstrated prolongation of porcine xenograft survival; however, advancement in XLTx has remained frustratingly limited. Further intensive and innovative strategies including genetic manipulation of donors, as well as inflammation/coagulation dysregulation, are required to make XLTx a clinical possibility.

Effects of carbon monoxide on early dysfunction and microangiopathy following GalT-KO porcine pulmonary xenotransplantation in cynomolgus monkeys

BACKGROUND

Despite progress in the current genetic manipulation of donor pigs, most non-human primates were lost within a day of receiving porcine lung transplants. We previously reported that carbon monoxide (CO) treatment improved pulmonary function in an allogeneic lung transplant (LTx) model using miniature swine. In this study, we evaluated whether the perioperative treatment with low-dose inhalation of CO has beneficial effects on porcine lung xenografts in cynomolgus monkeys (cynos).

METHODS

Eight cynos received orthotopic left LTx using either α-1,3-galactosyltransferase knockout (GalT-KO; n = 2) or GalT-KO with human decay accelerating factor (hDAF) (GalT-KO/hDAF; n = 6) swine donors. These eight animals were divided into three groups. In Group 1 (n = 2), neither donor nor recipients received CO therapy. In Group 2 (n = 4), donors were treated with inhaled CO for 180-minute. In Group 3 (n = 2), both donors and recipients were treated with CO (donor: 180-minute; recipient: 360-minute). Concentration of inhaled CO was adjusted based on measured levels of carboxyhemoglobin in the blood (15%-20%).

RESULTS

Two recipients survived for 3 days; 75 hours (no-CO) and 80 hours (CO in both the donor and the recipient), respectively. Histology showed less inflammatory cell infiltrates, intravascular thrombi, and hemorrhage in the 80-hour survivor with the CO treatment than the 75-hours non-CO treatment. Anti-non-Gal cytotoxicity levels did not affect the early loss of the grafts. Although CO treatment did not prolong overall xeno lung graft survival, the recipient/donor CO treatment helped to maintain platelet counts and inhibit TNF-α and IL-6 secretion at 2 hours after revascularization of grafts. In addition, lung xenografts that were received recipient/donor CO therapy demonstrated fewer macrophage and neutrophil infiltrates. Infiltrating macrophages as well as alveolar epithelial cells in the CO-treated graft expressed heme oxygenase-1.

CONCLUSION

Although further investigation is required, CO treatment may provide a beneficial strategy for pulmonary xenografts.

Role of Intrinsic (Graft) Versus Extrinsic (Host) Factors in the Growth of Transplanted Organs Following Allogeneic and Xenogeneic Transplantation

In our studies of life-supporting α-1,3-galactocyltransferase knockout (GalT-KO) pig-to-baboon kidneys, we found that some recipients developed increased serum creatinine with growth of the grafts, without histological or immunological evidence of rejection. We hypothesized that the rapid growth of orthotopic pig grafts in smaller baboon recipients may have led to deterioration of organ function. To test this hypothesis for both kidneys and lungs, we assessed whether the growth of outbred (Yorkshire) organ transplants in miniature swine was regulated by intrinsic (graft) or extrinsic (host environment) factors. Yorkshire kidneys exhibited persistent growth in miniature swine, reaching 3.7 times their initial volume over 3 mo versus 1.2 times for miniature swine kidneys over the same time period. Similar rapid early growth of lung allografts was observed and, in this case, led to organ dysfunction. For xenograft kidneys, a review of our results suggests that there is a threshold for kidney graft volume of 25 cm³ /kg of recipient body weight at which cortical ischemia is induced in transplanted GalT-KO kidneys in baboons. These results suggest that intrinsic factors are responsible, at least in part, for growth of donor organs and that this property should be taken into consideration for growth-curve-mismatched transplants, especially for life-supporting organs transplanted into a limited recipient space.

Targeting heme oxygenase-1 and carbon monoxide for therapeutic modulation of inflammation

The heme oxygenase-1 (HO-1) enzyme system remains an attractive therapeutic target for the treatment of inflammatory conditions. HO-1, a cellular stress protein, serves a vital metabolic function as the rate-limiting step in the degradation of heme to generate carbon monoxide (CO), iron, and biliverdin-IXα (BV), the latter which is converted to bilirubin-IXα (BR). HO-1 may function as a pleiotropic regulator of inflammatory signaling programs through the generation of its biologically active end products, namely CO, BV and BR. CO, when applied exogenously, can affect apoptotic, proliferative, and inflammatory cellular programs. Specifically, CO can modulate the production of proinflammatory or anti-inflammatory cytokines and mediators. HO-1 and CO may also have immunomodulatory effects with respect to regulating the functions of antigen-presenting cells, dendritic cells, and regulatory T cells. Therapeutic strategies to modulate HO-1 in disease include the application of natural-inducing compounds and gene therapy approaches for the targeted genetic overexpression or knockdown of HO-1. Several compounds have been used therapeutically to inhibit HO activity, including competitive inhibitors of the metalloporphyrin series or noncompetitive isoform-selective derivatives of imidazole-dioxolanes. The end products of HO activity, CO, BV and BR may be used therapeutically as pharmacologic treatments. CO may be applied by inhalation or through the use of CO-releasing molecules. This review will discuss HO-1 as a therapeutic target in diseases involving inflammation, including lung and vascular injury, sepsis, ischemia-reperfusion injury, and transplant rejection.

Characterization of pig sperm hyaluronidase and improvement of the digestibility of cumulus cell mass by recombinant pSPAM1 hyaluronidase in an in vitro fertilization assay

Although sperm hyaluronidase is thought to play an important role in mammalian fertilization, the molecular function underlying these steps remains largely unknown. In mouse models, sperm-specific SPAM1 and HYAL5 hyaluronidase are believed to function in both sperm penetration of the cumulus matrix and sperm-ZP binding. However, gene-targeting studies for SPAM1 or HYAL5 show that hyaluronidases are not essential for fertilization, despite the fact that exogenous hyaluronidase can disrupt the cumulus matrix. Therefore, to evaluate whether sperm hyaluronidase is essential for mammalian fertilization, it is necessary to generate HYAL5/SPAM1 double-knockout mice. However, generating double-knockout mice is very difficult because these two genes exist on the same chromosome. Recently, investigators have begun to employ the pig model system to study human disease due to its similarities to human anatomy and physiology. In this study, we confirmed that pig SPAM1 exists as a single copy gene on chromosome 18 and is specifically expressed in the testis. In addition, we expressed recombinant pig SPAM1 in human embryonic kidney 293 cells and showed that these enzymes possess hyaluronidase activity. We also demonstrated that a polyclonal antibody against pig sperm hyaluronidase inhibits sperm-egg interactions in an in vitro fertilization (IVF) assay. Our results suggest that pig SPAM1 may play a critical role in pig fertilization and that recombinant SPAM1 can disperse the oocyte-cumulus complex in an IVF assay.

The pig as a model for translational research: overview of porcine animal models at Jichi Medical University

To improve the welfare of experimental animals, investigators seek to respect the 3R principle (Replacement, Reduction, and Refinement). Even when large animal studies are essential before moving to clinical trials, it is important to look for ways to reduce the number of experimental animals used. At the Center for the Development of Advanced Medical Technology, we consider ‘medical’ pigs to be ideal preclinical model systems.

We have been using both wild-type and genetically modified pigs. We began using this approach about 10 years ago with a ‘total pig system’ to model human health and disease for the purposes of both medical skill education and the development of new devices and therapeutic strategies.

At our Center, medical students and residents use pigs to gain experience with surgical skills and train for emergency procedures after appropriate simulation training. Senior clinicians have also used these models to advance the development of innovative tools for endo- and laparoscopic procedures. The Center focuses on translational research for organ transplantation and stem cell therapy. Several pig models have been established for liver, intestine, kidney, pancreas, and lung transplantation. Mesenchymal stromal cells have been established in green fluorescent protein- and red fluorescent protein-transgenic pigs and tested to trans-differentiate organogenesis. A program to establish induced pluripotent stem cells in the pig is ongoing at our Center.

Here, we review our 10 years of activity in this field. Based on our experience in surgical education and research, experimental pigs are valuable models in translational research.

Intracoronary artery transplantation of cardiomyoblast-like cells from human adipose tissue-derived multi-lineage progenitor cells improve left ventricular dysfunction and survival in a swine model of chronic myocardial infarction

Transplantation of human cardiomyoblast-like cells (hCLCs) from human adipose tissue-derived multi-lineage progenitor cells improved left ventricular function and survival of rats with myocardial infarction. Here we examined the effect of intracoronary artery transplantation of human CLCs in a swine model of chronic heart failure. Twenty-four pigs underwent balloon-occlusion of the first diagonal branch followed by reperfusion, with a second balloon-occlusion of the left ascending coronary artery 1 week later followed by reperfusion. Four weeks after the second occlusion/reperfusion, 17 of the 18 surviving animals with severe chronic MI (ejection fraction <35% by echocardiography) were immunosuppressed then randomly assigned to receive either intracoronary artery transplantation of hCLCs hADMPCs or placebo lactic Ringer's solution with heparin. Intracoronary artery transplantation was followed by the distribution of DiI-stained hCLCs into the scarred myocardial milieu. Echocardiography at post-transplant days 4 and 8 weeks showed rescue and maintenance of cardiac function in the hCLCs transplanted group, but not in the control animals, indicating myocardial functional recovery by hCLCs intracoronary transplantation. At 8 week post-transplantation, 7 of 8 hCLCs transplanted animals were still alive compared with only 1 of the 5 control (p=0.0147). Histological studies at week 12 post-transplantation demonstrated engraftment of the pre DiI-stained hCLCs into the scarred myocardium and their expression of human specific alpha-cardiac actin. Human alpha cardiac actin-positive cells also expressed cardiac nuclear factors; nkx2.5 and GATA-4. Our results suggest that intracoronary artery transplantation of hCLCs is a potentially effective therapeutic strategy for future cardiac tissue regeneration.