a-porcine-heterotopic-heart-transplantation-protocol-for-delivery

A Porcine Heterotopic Heart Transplantation Protocol for Delivery of Therapeutics to a Cardiac Allograft

Cardiac transplantation is the gold standard treatment for end-stage heart failure. However, it remains limited by the number of available donor hearts ...

Duke University

Clinically, both percutaneous and surgical approaches to deliver viral vectors to the heart either have resulted in therapeutically inadequate levels of transgene expression or have raised safety concerns associated with extra-cardiac delivery. Recent developments in the field of normothermic ex vivo cardiac perfusion storage have now created opportunities to overcome these limitations and safety concerns of cardiac gene therapy. This study examined the feasibility of ex vivo perfusion as an approach to deliver a viral vector to a donor heart during storage and the resulting bio distribution and expression levels of the transgene in the recipient post-transplant. The influence of components (proprietary solution, donor blood, and ex vivo circuitry tubing and oxygenators) of the Organ Care System (OC) (TransMedics, Inc., Andover MA) on viral vector transduction was examined using a cell-based luciferase assay. Our ex vivo perfusion strategy, optimized for efficient Adenoviral vector transduction, was utilized to deliver 5 × 10 total viral particles of an Adenoviral firefly luciferase vector with a cytomegalovirus (CMV) promotor to porcine donor hearts prior to heterotopic implantation. We have evaluated the overall levels of expression, protein activity, as well as the bio distribution of the firefly luciferase protein in a series of three heart transplants at a five-day post-transplant endpoint. The perfusion solution and the ex vivo circuitry did not influence viral vector transduction, but the serum or plasma fractions of the donor blood significantly inhibited viral vector transduction. Thus, subsequent gene delivery experiments to the explanted porcine heart utilized an autologous blood recovery approach to remove undesired plasma or serum components of the donor blood prior to its placement into the circuit. Enzymatic assessment of luciferase activity in tissues (native heart, allograft, liver etc.) obtained post-transplant day five revealed wide-spread and robust luciferase activity in all regions of the allograft (right and left atria, right and left ventricles, coronary arteries) compared to the native recipient heart. Importantly, luciferase activity in recipient heart, liver, lung, spleen, or psoas muscle was within background levels. Similar to luciferase activity, the luciferase protein expression in the allograft appeared uniform and robust across all areas of the myocardium as well as in the coronary arteries. Importantly, despite high copy number of vector genomic DNA in transplanted heart tissue, there was no evidence of vector DNA in either the recipient's native heart or liver. Overall we demonstrate a simple protocol to achieve substantial, global gene delivery and expression isolated to the cardiac allograft. This introduces a novel method of viral vector delivery that opens the opportunity for biological modification of the allograft prior to implantation that may improve post-transplant outcomes.

A normothermic ex vivo organ perfusion delivery method for cardiac transplantation gene therapy.

Stroke remains a significant complication of left ventricular assist device (LVAD) therapy. We performed a single-center retrospective study evaluating patients undergoing first-time HeartWare HVAD (Medtronic Inc) or HeartMate 3 (Abbott Inc) implantation from September 2009-February 2018.

Stroke risk following implantation of current generation centrifugal flow left ventricular assist devices.

Stroke is a devastating complication of left ventricular assist device (LVAD) therapy. Understanding the characteristics, risk factors and outcomes of strokes associated with the centrifugal flow LVADs is important to devise better strategies for management and prevention. This is a retrospective cohort study at a single US academic medical center. The cohort includes patients who received a first time Heartmate 3 (HM3) or Heartware (HVAD) LVAD between September 2009 through February 2018 and had a stroke while the LVAD was in place. Descriptive statistics were used when appropriate. A logistic regression analysis was used to determine predictors of poor outcome. Out of a total of 247 patients, 12.1% (N = 30, 24 HVAD and 6 HM3) had a stroke (63% ischemic) and 3 of these patients had pump thrombosis. Events per patient year (EPPY) were similar for HVAD and HM3 patients (0.3 ± 0.1). INR was subtherapeutic in 47.4% of ischemic stroke patients and supratherapeutic in 18.2% of hemorrhagic stroke patients. Concurrent infections were more common in the setting of hemorrhagic stroke than ischemic stroke (45.4% vs 5.3%, p = 0.008). Strokes were severe in most cases, with initial NIH stroke scale (NIHSS) higher in HM3 patients compared to HVAD patients (mean 24.6 vs 16) and associated with high in-patient mortality (21.1% of ischemic stroke vs. 88.8% of hemorrhagic stroke). Predictors of death within 30 days and disability at 90 days included creatinine at stroke onset, concurrent infection, hemorrhaghic stroke, and initial stroke severity (NIHSS). A score derived from these variables predicted with 100% certainty mortality at 30 days and mRS ≥ 4 at 90 days. For patients with centrifugal flow LVADs, ischemic strokes were more common but hemorrhagic strokes were associated with higher in-patient mortality and more frequently seen in the setting of concurrent infections. Infections, sub or supratherapeutic INR range, and comorbid cardiovascular risk factors may all be contributing to the stroke burden. These findings may inform future strategies for stroke prevention in this population.

Characteristics of strokes associated with centrifugal flow left ventricular assist devices.

Programmed death-ligand 1 (PD-L1), a transmembrane protein and member of the CD28 T cell family is associated with lymphocyte activation. PD-L1 expression is upregulated on activated antigen presenting cells such as monocytes, myeloid and dendritic cells. When bound to its cognate receptor programmed cell death (PD-1), inhibition of immune responses including downregulation of T cell proliferation occurs. Mechanistically, such inhibition would be hypothetically favorable in the setting of a transplanted organ undergoing allograft rejection. However, there is a paucity of data addressing the role of PD-L1 and PD-1 expression in the human transplanted heart.

PD-1 and PD-L1 expression in cardiac transplantation.

Temporary left ventricular assist device may be safer than veno-arterial extracorporeal membrane oxygenation for treating shock in the presence of a mitral prosthesis.

Article	Year
A normothermic ex vivo organ perfusion delivery method for cardiac transplantation gene therapy. Scientific reports\| PubMed ID: 31142753	2019
Stroke risk following implantation of current generation centrifugal flow left ventricular assist devices. Journal of cardiac surgery\| PubMed ID: 31808964	2020
Characteristics of strokes associated with centrifugal flow left ventricular assist devices. Scientific reports\| PubMed ID: 33462301	2021
PD-1 and PD-L1 expression in cardiac transplantation. Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology\| PubMed ID: 33737091	2021
Temporary left ventricular assist device may be safer than veno-arterial extracorporeal membrane oxygenation for treating shock in the presence of a mitral prosthesis. JTCVS techniques\| PubMed ID: 34317873	2020

Yuting Chiang

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