Gene delivery followed by ex vivo lung perfusion using an adeno-associated viral vector in a rodent lung transplant model

OBJECTIVE

Ex vivo lung perfusion has emerged as a platform for organ preservation, evaluation, and restoration. Gene delivery using a clinically relevant adeno-associated vector during ex vivo lung perfusion may be useful in optimizing donor allografts while the graft is maintained physiologically active. We evaluated the feasibility of adeno-associated vector-mediated gene delivery during ex vivo lung perfusion in a rat transplant model. Additionally, we assessed off-target effects and explored different routes of delivery.

METHODS

Rat heart-lung blocks were procured and underwent 1-hour ex vivo lung perfusion. Before ex vivo lung perfusion, 4e11 viral genome luciferase encoding adeno-associated vector 9 was administered via the left bronchus (Br group, n = 4), via the left pulmonary artery (PA group, n = 3), or directly into the circuit (Circuit group, n = 3). Donor lungs in the Control group (n = 3) underwent ex vivo lung perfusion without adeno-associated vector 9. Only the left lung was transplanted. Animals underwent bioluminescence imaging weekly before being killed at 2 weeks. Tissues were collected for luciferase activity measurement.

RESULTS

All recipients tolerated the transplant well. At 2 weeks post-transplant, luciferase activity in the transplanted lung was significantly higher among animals in the Br group compared with the other 3 groups (Br: 1.1 × 106 RLU/g, PA: 8.3 × 104 RLU/g, Circuit: 3.8 × 103 RLU/g, Control: 2.5 × 103 RLU/g, P = .0003). No off-target transgene expression was observed.

CONCLUSIONS

In this work, we demonstrate that a clinically relevant adeno-associated vector 9 vector mediates gene transduction during ex vivo lung perfusion in rat lung grafts when administered via the airway and potentially the pulmonary artery. Our preliminary results suggest a higher transduction efficiency when adeno-associated vector 9 was delivered via the airway, and delivery during ex vivo lung perfusion reduces off-target effects after graft implant.

A call to action in thoracic transplant surgical training

Thoracic organ recovery and implantation is increasing in complexity. Simultaneously the logistic burden and associated cost is rising. An electronic survey distributed to the surgical directors of thoracic transplant programs in the United States indicated dissatisfaction amongst 72% of respondents with current procurement training and 85% of respondents favored a process for certification in thoracic organ transplantation. These responses highlight concerns for the current paradigm of training in thoracic transplantation. We discuss the implications of advancements in organ retrieval and implant for surgical training and propose that the thoracic transplant community might address the need through formalized training in procurement and certification in thoracic transplantation.

Point-of-Care Assessment of DCD Livers During Normothermic Machine Perfusion in a Nonhuman Primate Model

Normothermic machine perfusion (NMP) provides clinicians an opportunity to assess marginal livers before transplantation. However, objective criteria and point-of-care (POC) biomarkers to predict risk and guide decision making are lacking. In this investigation, we characterized trends in POC biomarkers during NMP and compared primate donation after circulatory death (DCD) livers with short and prolonged warm ischemic injury. Following asystole, livers were subjected to either 5 minutes (DCD-5min, n = 4) or 45 minutes (DCD-45min, n = 4) of warm ischemia time. Livers were flushed with heparinized UW solution, and preserved in cold storage before NMP. During flow-controlled NMP, circulating perfusate and tissue biopsies were collected at 0, 2, 4, 6, and 8 hours for analysis. DCD-45min livers had greater terminal portal vein pressure (8.5 vs. 13.3 mm Hg, P = 0.027) and terminal portal vein resistance (16.3 vs. 32.4 Wood units, P = 0.005). During perfusion, DCD-45min livers had equivalent terminal lactate clearance (93% vs. 96%, P = 0.344), greater terminal alanine aminotransferase (163 vs. 883 U/L, P = 0.002), and greater terminal perfusate gamma glutamyltransferase (GGT) (5.0 vs. 31.7 U/L, P = 0.002). DCD-45min livers had higher circulating levels of flavin mononucleotide (FMN) at hours 2 and 4 of perfusion (136 vs. 250 ng/mL, P = 0.029; and 158 vs. 293 ng/mL, P = 0.003; respectively). DCD-5min livers produced more bile and demonstrated progressive decline in bile lactate dehydrogenase, whereas DCD-45min livers did not. On blinded histologic evaluation, DCD-45min livers demonstrated greater injury and necrosis at late stages of perfusion, indicative of nonviability. Conclusion: Objective criteria are needed to define graft viability during NMP. Perfusate lactate clearance does not discriminate between viable and nonviable livers during NMP. Perfusate GGT and FMN may represent POC biomarkers predictive of liver injury during NMP.

Resection of the irradiated esophagus: the impact of lymph node yield on survival

There is debate surrounding the appropriate threshold for lymph node harvest during esophagectomy in patients with esophageal cancer, specifically for those receiving preoperative radiation. The purpose of this study was to determine the impact of lymph node yield on survival in patients receiving preoperative chemoradiation for esophageal cancer. The National Cancer Database (NCDB) was utilized to identify patients with esophageal cancer that received preoperative radiation. The cohort was divided into patients undergoing minimal (<9) or extensive (≥9) lymph node yield. Demographic, operative, and postoperative outcomes were compared between the groups. Kaplan-Meier analysis with the log rank test was used to compare survival between the yield groups. Cox proportional hazards model was used to determine the association between lymph node yield and survival. In total, 886 cases were included: 349 (39%) belonging to the minimal node group and 537 (61%) to the extensive group. Unadjusted 5-year survival was similar between the minimal and extensive groups, respectively (37.3% vs. 38.8%; P > 0.05). After adjustment using Cox regression, extensive lymph node yield was associated with survival (hazard ratio 0.80, confidence interval 0.66-0.98, P = 0.03). This study suggests that extensive lymph node yield is advantageous for patients with esophageal cancer undergoing esophagectomy following induction therapy. This most likely reflects improved diagnosis and staging with extensive yield.

Anticoagulation Strategies in the Perioperative Period for Lung Transplant

Patients who are undergoing lung transplantation may require systemic anticoagulation in the perioperative period for various indications at the time of the procedure. Four-factor prothrombin complex concentrate has been approved in the United States to reverse the effects of warfarin for patients requiring urgent surgery. We describe a perioperative anticoagulation strategy with warfarin that is reversed before incision using 4-factor complex concentrate for off-pump lung transplant recipients.

Gastroesophageal reflux symptoms are not sufficient to guide esophageal function testing in lung transplant candidates

Gastroesophageal reflux disease and esophageal dysmotility are prevalent in patients with advanced lung disease and are associated with graft dysfunction following lung transplantation. As a result, many transplant centers perform esophageal function testing as part of the wait-listing process but guidelines for testing in this population are lacking. The aim of this study is to describe whether symptoms of gastroesophageal reflux correlate with abnormal results on pH-metry and high-resolution manometry and can be used to identify those who require testing. We performed a retrospective cohort study of 226 lung transplant candidates referred for high-resolution manometry and pH-metry over a 12-month period in 2015. Demographic data, results of a standard symptom questionnaire and details of esophageal function testing were obtained. Associations between the presence of symptoms and test results were analyzed using Fisher's exact tests and multivariable logistic regression. The most common lung disease diagnosis was interstitial lung disease (N = 131, 58%). Abnormal pH-metry was seen in 116 (51%) patients and the presence of symptoms was significantly associated with an abnormal study (p < 0.01). Dysmotility was found in 98 (43%) patients, with major peristaltic or esophageal outflow disorders in 45 (20%) patients. Symptoms were not correlated with findings on esophageal high-resolution manometry. Fifteen of 25 (60%) asymptomatic patients had an abnormal manometry or pH-metry. These results demonstrate that in patients with advanced lung disease, symptoms of gastroesophageal reflux increase the likelihood of elevated acid exposure on pH-metry but were not associated with dysmotility. Given the proportion of asymptomatic patients with abnormal studies and associated post-transplant risks, a practice of universal high-resolution manometry and pH-metry testing in this population is justifiable.

Long-term survival following kidney transplantation in previous lung transplant recipients-An analysis of the unos registry

BACKGROUND

Kidney transplantation has been advocated as a therapeutic option in lung recipients who develop end-stage renal disease (ESRD). This analysis outlines patterns of allograft survival following kidney transplantation in previous lung recipients (KAL).

METHODS

Data from the UNOS lung and kidney transplantation registries (1987-2013) were cross-linked to identify lung recipients who were subsequently listed for and/or underwent kidney transplantation. Time-dependent Cox models compared the survival rates in KAL patients with those waitlisted for renal transplantation who never received kidneys. Survival analyses compared outcomes between KAL patients and risk-matched recipients of primary, kidney-only transplantation with no history of lung transplantation (KTx).

RESULTS

A total of 270 lung recipients subsequently underwent kidney transplantation (KAL). Regression models demonstrated a lower risk of post-listing mortality for KAL patients compared with 346 lung recipients on the kidney waitlist who never received kidneys (P<.05). Comparisons between matched KAL and KTx patients demonstrated significantly increased risk of death and graft loss (P<.05), but not death-censored graft loss, for KAL patients (P = .86).

CONCLUSIONS

KAL patients enjoy a significant survival benefit compared with waitlisted lung recipients who do not receive kidneys. However, KAL patients do poorly compared with KTx patients. Decisions about KAL transplantation must be made on a case-by-case basis considering patient and donor factors.

Extracorporeal membrane oxygenation in the pre and post lung transplant period

Evolution in technology has resulted in rapid increase in utilization of extracorporeal membrane oxygenation (ECMO) as a bridge to recovery and/or transplantation. Although there is limited evidence for the use of ECMO, recent improvements in ECMO technology, personnel training, ambulatory practices on ECMO and lung protective strategies have resulted in improved outcomes in patients bridged to lung transplantation. This review provides an insight into the current outcomes and best practices for utilization of ECMO in the pre- and post-lung transplantation period.

Staging of Bilateral Lung Transplantation for High-Risk Patients With Interstitial Lung Disease: One Lung at a Time

The choice of a single or bilateral lung transplant for interstitial lung disease (ILD) is controversial, as surgical risk, long-term survival and organ allocation are competing factors. In an effort to balance risk and benefit, our center adopted a staged bilateral lung transplant approach for higher surgical risk ILD patients where the patient has a single lung transplant followed by a second single transplant at a later date. We sought to understand the surgical risk, organ allocation and early outcomes of these staged bilateral recipients as a group and in comparison to matched single and bilateral recipients. Our analysis demonstrates that staged bilateral lung transplant recipients (n = 12) have a higher lung allocation score (LAS), lower pulmonary function tests and a lower glomerular filtration rate prior to the first transplant compared to the second (p < 0.01). There was a shorter length of hospital stay for the second transplant (p = 0.02). The staged bilateral compared to the single and bilateral case-matched controls had comparable short-term survival (p = 0.20) and pulmonary function tests at 1 year. There was a higher incidence of renal injury in the conventional bilateral group compared to the single and staged bilateral groups. The staged bilateral procedure is a viable option in select ILD patients.

Chronic aspiration of gastric fluid induces the development of obliterative bronchiolitis in rat lung transplants

Long-term survival of a pulmonary allograft is currently hampered by obliterative bronchiolitis (OB), a form of chronic rejection that is unique to lung transplantation. While tracheobronchial aspiration from gastroesophageal reflux disease (GERD) has clinically been associated with OB, no experimental model exists to investigate this problem. Using a WKY-to-F344 rat orthotopic left lung transplant model, the effects of chronic aspiration on pulmonary allograft were evaluated. Recipients received cyclosporine with or without 8 weekly aspirations of gastric fluid into the allograft. Six (66.7%) of 9 allografts with aspiration demonstrated bronchioles with surrounding monocytic infiltrates, fibrosis and loss of normal lumen anatomy, consistent with the development of OB. In contrast, none of the allografts without aspiration (n = 10) demonstrated these findings (p = 0.002). Of the grafts examined grossly, 83% of the allografts with chronic aspiration but only 20% without aspiration appeared consolidated (p = 0.013). Aspiration was associated with increased levels of IL-1 alpha, IL-1 beta, IL-6, IL-10, TNF-alpha and TGF-beta in BAL and of IL-1 alpha, IL-4 and GM-CSF in serum. This study provides experimental evidence linking chronic aspiration to the development of OB and suggests that strategies aimed at preventing aspiration-related injuries might improve outcomes in clinical lung transplantation.