Clinical application of ET-Kyoto solution for lung transplantation

Impact of perioperative airway pathogens on living-donor lobar lung transplantation outcomes

PURPOSE

To elucidate the clinical impact of pathogenic organism (PO) positivity early after transplantation, we evaluated the impact of perioperative airway POs on outcomes after living-donor lobar lung transplantation (LDLLT), where the graft airway is supposed to be sterile from a healthy donor.

METHOD

A retrospective review of 67 adult LDLLT procedures involving 132 living donors was performed. Presence of POs in the recipients' airways was evaluated preoperatively and postoperatively in intensive-care units.

RESULTS

POs were detected preoperatively in 13 (19.4%) recipients. No POs were isolated from the donor airways at transplantation. POs were detected in 39 (58.2%) recipients postoperatively; most were different from the POs isolated preoperatively. Postoperative PO isolation was not associated with short-term outcomes other than prolonged postoperative ventilation. The 5-year overall survival was significantly better in the PO-negative group than in the PO-positive group (89.1% vs. 63.7%, P = 0.014). In the multivariate analysis, advanced age (hazard ratio [HR]: 1.041 per 1-year increase, P = 0.033) and posttransplant PO positivity in the airway (HR: 3.684, P = 0.019) significantly affected the survival.

CONCLUSIONS

The airways of the living-donor grafts were microbiologically sterile. PO positivity in the airway early after transplantation negatively impacted long-term outcomes.

A Novel Trehalose Synthase for the Production of Trehalose and Trehalulose

A novel putative trehalose synthase gene (treM) was identified from an extreme temperature thermal spring. The gene was expressed in Escherichia coli followed by purification of the protein (TreM). TreM exhibited the pH optima of 7.0 for trehalose and trehalulose production, although it was functional and stable in the pH range of 5.0 to 8.0. Temperature activity profiling revealed that TreM can catalyze trehalose biosynthesis in a wide range of temperatures, from 5°C to 80°C. The optimum activity for trehalose and trehalulose biosynthesis was observed at 45°C and 50°C, respectively. A catalytic reaction performed at the low temperature of 5°C yielded trehalose with significantly reduced by-product (glucose) production in the reaction. TreM displayed remarkable thermal stability at optimum temperatures, with only about 20% loss in the activity after heat (50°C) exposure for 24 h. The maximum bioconversion yield of 74% trehalose (at 5°C) and 90% trehalulose (at 50°C) was obtained from 100 mM maltose and 70 mM sucrose, respectively. TreM was demonstrated to catalyze trehalulose biosynthesis utilizing the low-cost feedstock jaggery, cane molasses, muscovado, and table sugar.

IMPORTANCE Trehalose is a rare sugar of high importance in biological research, with its property to stabilize cell membrane and proteins and protect the organism from drought. It is instrumental in the cryopreservation of human cells, e.g., sperm and blood stem cells. It is also very useful in the food industry, especially in the preparation of frozen food products. Trehalose synthase is a glycosyl hydrolase 13 (GH13) family enzyme that has been reported from about 22 bacterial species so far. Of these enzymes, to date, only two have been demonstrated to catalyze the biosynthesis of both trehalose and trehalulose. We have investigated the metagenomic data of an extreme temperature thermal spring to discover a novel gene that encodes a trehalose synthase (TreM) with higher stability and dual transglycosylation activities of trehalose and trehalulose biosynthesis. This enzyme is capable of catalyzing the transformation of maltose to trehalose and sucrose to trehalulose in a wide pH and temperature range. The present investigation endorses the thermal aquatic habitat as a promising genetic resource for the biocatalysts with high potential in producing high-value rare sugars.

Ischemia-Reperfusion Injury in Lung Transplantation

Lung transplantation has been established worldwide as the last treatment for end-stage respiratory failure. However, ischemia–reperfusion injury (IRI) inevitably occurs after lung transplantation. The most severe form of IRI leads to primary graft failure, which is an important cause of morbidity and mortality after lung transplantation. IRI may also induce rejection, which is the main cause of mortality in recipients. Despite advances in donor management and graft preservation, most donor grafts are still unsuitable for transplantation. Although the pulmonary endothelium is the primary target site of IRI, the pathophysiology of lung IRI remains incompletely understood. It is essential to understand the mechanism of pulmonary IRI to improve the outcomes of lung transplantation. Therefore, we reviewed the state-of-the-art in the management of pulmonary IRI after lung transplantation. Recently, the ex vivo lung perfusion (EVLP) system has been clinically introduced worldwide. Various promising therapeutic strategies for the protection of the endothelium against IRI, including EVLP, inhalation therapy with therapeutic gases and substances, fibrinolytic treatment, and mesenchymal stromal cell therapy, are awaiting clinical application. We herein review the latest advances in the field of pulmonary IRI in lung transplantation.

Prevention of Chronic Rejection of Marginal Kidney Graft by Using a Hydrogen Gas-Containing Preservation Solution and Adequate Immunosuppression in a Miniature Pig Model

In clinical kidney transplantation, the marginal kidney donors are known to develop chronic allograft rejection more frequently than living kidney donors. In our previous study, we have reported that the hydrogen gas-containing organ preservation solution prevented the development of acute injuries in the kidney of the donor after cardiac death by using preclinical miniature pig model. In the present study, we verified the impact of hydrogen gas treatment in transplantation with the optimal immunosuppressive protocol based on human clinical setting by using the miniature pig model. Marginal kidney processed by hydrogen gas-containing preservation solution has been engrafted for long-term (longer than 100 days). A few cases showed chronic rejection reaction; however, most were found to be free of chronic rejection such as graft tissue fibrosis or renal vasculitis. We concluded that marginal kidney graft from donor after cardiac death is an acceptable model for chronic rejection and that if the transplantation is carried out using a strict immunosuppressive protocol, chronic rejection may be alleviated even with the marginal kidney.

Native lung complications after living-donor lobar lung transplantation

BACKGROUND

Living-donor lobar lung transplantation (LDLLT) is viable for critically ill patients in situations of donor shortage. Because it is sometimes difficult to find 2 ideal living donors with suitable graft sizes, we developed native lung-sparing procedures, including single LDLLT and native upper lobe-sparing LDLLT. This study aimed to investigate native lung complications (NLCs) in native lung-sparing LDLLT.

METHODS

Between April 2002 and March 2019, 92 LDLLTs and 124 cadaveric lung transplantations (CLTs) were performed at the Kyoto University Hospital. Our prospectively maintained database and clinical records were reviewed to compare NLCs among recipients who underwent native lung-sparing LDLLT (n = 21) with those among recipients who underwent single CLT (n = 61).

RESULTS

Among 21 recipients who underwent native lung-sparing LDLLT, 11 NLCs occurred in 8 recipients. No fatal NLC was noted; however, 2 required surgical intervention. Post-transplant survival was not significantly different between native lung-sparing LDLLT recipients with NLCs and those without NLCs. The incidence of NLCs was comparable between native lung-sparing LDLLT recipients and single CLT recipients (8/21 vs 26/61, p = 0.80); however, NLCs occurred significantly later in LDLLT recipients than in CLT recipients (median: 665 vs 181.5 days after transplantation, p = 0.014).

CONCLUSIONS

NLCs after native lung-sparing LDLLT had favorable outcomes. Therefore, native lung-sparing LDLLT is a useful treatment option for severely ill patients who cannot wait for CLT. However, it is important to recognize that NLCs may occur later in LDLLT than in CLT.

Autophagy Dynamics and Modulation in a Rat Model of Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (IR) injury leading to cell death is a major cause of acute kidney injury, contributing to morbidity and mortality. Autophagy counteracts cell death by removing damaged macromolecules and organelles, making it an interesting anchor point for treatment strategies. However, autophagy is also suggested to enhance cell death when the ischemic burden is too strong. To investigate whether the role of autophagy depends on the severity of ischemic stress, we analyzed the dynamics of autophagy and apoptosis in an IR rat model with mild (45 min) or severe (60 min) renal ischemia. Following mild IR, renal injury was associated with reduced autophagy, enhanced mammalian target of rapamycin (mTOR) activity, and apoptosis. Severe IR, on the other hand, was associated with a higher autophagic activity, independent of mTOR, and without affecting apoptosis. Autophagy stimulation by trehalose injected 24 and 48 h prior to onset of severe ischemia did not reduce renal injury markers nor function, but reduced apoptosis and restored tubular dilation 7 days post reperfusion. This suggests that trehalose-dependent autophagy stimulation enhances tissue repair following an IR injury. Our data show that autophagy dynamics are strongly dependent on the severity of IR and that trehalose shows the potential to trigger autophagy-dependent repair processes following renal IR injury.

Protective Effects of a Hydrogen-Rich Preservation Solution in a Canine Lung Transplantation Model

BACKGROUND

Molecular hydrogen (H₂) has protective effects against ischemia-reperfusion injury in various organs. Because they are easier to transport and safer to use than inhaled H₂, H₂-rich solutions are suitable for organ preservation. In this study, we examined the protective effects of an H₂-rich solution for lung preservation in a canine left lung transplantation (LTx) model.

METHODS

Ten beagles underwent orthotopic left LTx after 23 hours of cold ischemia followed by reperfusion for 4 hours. Forty-five minutes after reperfusion, the right main pulmonary artery was clamped to evaluate the function of the implanted graft. The beagles were divided into two groups: control group (n = 5), and H₂ group (n = 5). In the control group, the donor lungs were flushed and immersed during cold preservation at 4°C using ET-Kyoto solution, and in the H₂ group, these were flushed and immersed using H₂-rich ET-Kyoto solution. Physiologic assessments were performed during reperfusion. After reperfusion, the wet-to-dry ratios were determined, and histology examinations were performed.

RESULTS

Significantly higher partial pressure of arterial oxygen and significantly lower partial pressure of carbon dioxide were observed in the H₂ group than in the control group (P = .045 and P < .001, respectively). The wet-to-dry ratio was significantly lower in the H₂ group than in the control group (P = .032). Moreover, in histology examination, less lung injury and fewer apoptotic cells were observed in the H₂ group (P < .001 and P < .001, respectively).

CONCLUSIONS

Our results demonstrated that the H₂-rich preservation solution attenuated ischemia-reperfusion injury in a canine left LTx model.

Transplantation of Bioengineered Lungs Created From Recipient-Derived Cells Into a Large Animal Model

The use of bioartificial lungs may represent a breakthrough for the treatment of end-stage lung disease. The present study aimed to evaluate the feasibility of transplanting bioengineered lungs created from autologous cells. Porcine decellularized lung scaffolds were seeded with porcine recipient-derived airway and vascular cells. The porcine recipient-derived cells were collected from lung tissue obtained by pulmonary wedge resection. Following culture of autologous cells in the scaffolds, the resulting grafts were unilaterally transplanted into porcine recipients (n = 3). Allograft left unilateral lung transplantation was performed in the control group (n = 3). Left unilateral transplantation of decellularized grafts was also performed in a separate control group (n = 2). In vivo functions were assessed for 2 hours after transplantation. Histologic evaluation and immunostaining showed the presence of airway and vascular cells in the bioengineered lungs. No animals survived in the decellularized transplant group, whereas all animals survived in the bioengineered transplant and allotransplant groups. However, bioengineered lung grafts showed marked bullous changes. The oxygen exchange was comparable between the bioengineered lung graft transplant and allograft transplant groups. However, the carbon dioxide gas exchange of the bioengineered lung graft transplant group was significantly lower than that of the allograft transplant group at 2 hours after transplantation (4.10 ± 0.87 mm Hg vs 24.7 ± 10.1 mm Hg, P = 0.02). Transplantation of bioartificial lung grafts created from autologous cells was feasible in the super-acute phase. However, bullous changes and poor carbon dioxide gas exchange remain limitations of this method.

Protective effects of a hydrogen-rich solution during cold ischemia in rat lung transplantation

BACKGROUND

Molecular hydrogen can reduce the oxidative stress of ischemia-reperfusion injury in various organs for transplantation and potentially improve survival rates in recipients. This study aimed to evaluate the protective effects of a hydrogen-rich preservation solution against ischemia-reperfusion injury after cold ischemia in rat lung transplantation.

METHODS

Lewis rats were divided into a nontransplant group (n = 3), minimum-ischemia group (n = 3), cold ischemia group (n = 6), and cold ischemia with hydrogen-rich (more than 1.0 ppm) preservation solution group (n = 6). The rats in the nontransplant group underwent simple thoracotomy, and the rats in the remaining 3 groups underwent orthotopic left lung transplantation. The ischemic time was <30 minutes in the minimum-ischemia group and 6 hours in the cold ischemia groups. After 2-hour reperfusion, we evaluated arterial blood gas levels, pulmonary function, lung wet-to-dry weight ratio, and histologic features of the lung tissue. The expression of proinflammatory cytokines was measured using quantitative polymerase chain reaction assays, and 8-hydroxydeoxyguanosine levels were evaluated using enzyme-linked immunosorbent assays.

RESULTS

When compared with the nontransplant and minimum-ischemia groups, the cold ischemia group had lower dynamic compliance, lower oxygenation levels, and higher wet-to-dry weight ratios. However, these variables were significantly improved in the cold ischemia with hydrogen-rich preservation solution group. This group also had fewer signs of perivascular edema, lower interleukin-1β messenger RNA expression, and lower 8-hydroxydeoxyguanosine levels than the cold ischemia group.

CONCLUSIONS

The use of a hydrogen-rich preservation solution attenuates ischemia-reperfusion injury in rat lungs during cold ischemia through antioxidant and anti-inflammatory effects.

High-Pressure Carbon Monoxide and Oxygen Mixture is Effective for Lung Preservation

(1) Background: Heme oxygenase-1 (HO-1) degrades heme and generates carbon monoxide (CO), producing various anti-inflammatory, anti-oxidative, and anti-apoptotic effects. This study aimed to confirm the effects of CO on the ischemia–reperfusion injury (IRI) of donor lungs using a high-pressure gas (HPG) preservation method. (2) Methods: Donor rat and canine lungs were preserved in a chamber filled with CO (1.5 atm) and oxygen (O₂; 2 atm) and were ventilated with either CO and O₂ mixture (CO/O₂ group) or air (air group) immediately before storage. Rat lungs were subjected to heterotopic cervical transplantation and evaluated after reperfusion, whereas canine lungs were subjected to allogeneic transplantation and evaluated. (3) Results: Alveolar hemorrhage in the CO/O₂ group was significantly milder than that in the air group. mRNA expression levels of HO-1 remained unchanged in both the groups; however, inflammatory mediator levels were significantly lower in the CO/O₂ group than in the air group. The oxygenation of graft lungs was comparable between the two groups, but lactic acid level tended to be higher in the air group. (4) Conclusions: The HO-1/CO system in the HPG preservation method is effective in suppressing IRI and preserving donor lungs.

Preservation of Blood Vessels with an Oxygen Generating Composite

Damage caused by oxygen deficiency (hypoxia) is one of the major factors limiting tissue and organ preservation time. Cooling tissues slows down metabolic rate of cells thereby prolonging tissue and organ survival sufficiently to allow transport and transplantation within a few hours. Although metabolism is slowed, cells and some enzymes continue to consume oxygen that can render cold stored tissues hypoxic. Here, an oxygen-generating composite (OGC) with sustained oxygen release is reported for ex vivo blood vessel preservation. Aorta segments are cultured under hypothermia for 25 days in vascular preservation media. The presence of OGC increases cell viability from 9 ± 6% to 96 ± 3% and retains 65 ± 8% of original KCl stimulated contractile force after 25 days compared with 25 ± 4% in controls. Culture for 7 days in nitrogen demonstrates proof-of-concept for normothermic blood vessel preservation, OGC increases the cell viability from 45 ± 15% to 78 ± 2%, and KCl stimulates contractile force from 49 ± 7% to 95 ± 8%, respectively. Oxygen release materials then may have a role in augmenting current preservation techniques.

Organ preservation: from the past to the future

Organ transplantation is the most effective therapy for patients with end-stage disease. Preservation solutions and techniques are crucial for donor organ quality, which is directly related to morbidity and survival after transplantation. Currently, static cold storage (SCS) is the standard method for organ preservation. However, preservation time with SCS is limited as prolonged cold storage increases the risk of early graft dysfunction that contributes to chronic complications. Furthermore, the growing demand for the use of marginal donor organs requires methods for organ assessment and repair. Machine perfusion has resurfaced and dominates current research on organ preservation. It is credited to its dynamic nature and physiological-like environment. The development of more sophisticated machine perfusion techniques and better perfusates may lead to organ repair/reconditioning. This review describes the history of organ preservation, summarizes the progresses that has been made to date, and discusses future directions for organ preservation.

Biotechnical production of trehalose through the trehalose synthase pathway: current status and future prospects

Trehalose (α-D-glucopyranosyl-(1 → 1)-α-D-glucopyranoside) is a non-reducing disaccharide composed of two glucose molecules linked by an α,α-1,1-glycosidic bond. It possesses physicochemical properties, which account for its biological roles in a variety of prokaryotic and eukaryotic organisms and invertebrates. Intensive studies of trehalose gradually uncovered its functions, and its applications in foods, cosmetics, and pharmaceuticals have increased every year. Currently, trehalose is industrially produced by the two-enzyme method, which was first developed in 1995 using maltooligosyltrehalose synthase (EC 5.4.99.15) and subsequently using maltooligosyltrehalose trehalohydrolase (EC 3.2.1.141), with starch as the substrate. This biotechnical method has lowered the price of trehalose and expanded its applications. However, when trehalose synthase (EC 5.4.99.16) was later discovered, this method for trehalose production using maltose as the substrate soon became a popular topic because of its simplicity and potential in industrial production. Since then, many trehalose synthases have been studied. This review summarizes the sources and characteristics of reported trehalose synthases, and the most recent advances on structural analysis of trehalose synthase, catalytic mechanism, molecular modification, and usage in industrial production processes.

Trehalose prevents aggregation of exosomes and cryodamage

Exosomes are important mediators in intercellular communication. Released by many cell types, they transport proteins, lipids, and nucleic acids to distant recipient cells and contribute to important physiopathological processes. Standard current exosome isolation methods based on differential centrifugation protocols tend to induce aggregation of particles in highly concentrated suspensions and freezing of exosomes can induce damage and inconsistent biological activity. Trehalose is a natural, non-toxic sugar widely used as a protein stabilizer and cryoprotectant by the food and drug industry. Here we report that addition of 25 mM trehalose to pancreatic beta-cell exosome-like vesicle isolation and storage buffer narrows the particle size distribution and increases the number of individual particles per microgram of protein. Repeated freeze-thaw cycles induce an increase in particle concentration and in the width of the size distribution for exosome-like vesicles stored in PBS, but not in PBS 25 mM trehalose. No signs of lysis or incomplete vesicles were observed by cryo-electron tomography in PBS and trehalose samples. In macrophage immune assays, beta-cell extracellular vesicles in trehalose show consistently higher TNF-alpha cytokine secretion stimulation indexes suggesting improved preservation of biological activity. The addition of trehalose might be an attractive means to standardize experiments in the field of exosome research and downstream applications.