Percutaneous methods of vector delivery in preclinical models

Base editing correction of hypertrophic cardiomyopathy in human cardiomyocytes and humanized mice

The most common form of genetic heart disease is hypertrophic cardiomyopathy (HCM), which is caused by variants in cardiac sarcomeric genes and leads to abnormal heart muscle thickening. Complications of HCM include heart failure, arrhythmia and sudden cardiac death. The dominant-negative c.1208G>A (p.R403Q) pathogenic variant (PV) in β-myosin (MYH7) is a common and well-studied PV that leads to increased cardiac contractility and HCM onset. In this study we identify an adenine base editor and single-guide RNA system that can efficiently correct this human PV with minimal bystander editing and off-target editing at selected sites. We show that delivery of base editing components rescues pathological manifestations of HCM in induced pluripotent stem cell cardiomyocytes derived from patients with HCM and in a humanized mouse model of HCM. Our findings demonstrate the potential of base editing to treat inherited cardiac diseases and prompt the further development of adenine base editor-based therapies to correct monogenic variants causing cardiac disease.

Targeted Delivery for Cardiac Regeneration: Comparison of Intra-coronary Infusion and Intra-myocardial Injection in Porcine Hearts

BACKGROUND

The optimal delivery route to enhance effectiveness of regenerative therapeutics to the human heart is poorly understood. Direct intra-myocardial (IM) injection is the gold standard, however, it is relatively invasive. We thus compared targeted IM against less invasive, catheter-based intra-coronary (IC) delivery to porcine myocardium for the acute retention of nanoparticles using cardiac magnetic resonance (CMR) imaging and viral vector transduction using qPCR.

METHODS

Ferumoxytol iron oxide (IO) nanoparticles (5 ml) were administered to Yorkshire swine (n = 13) by: (1) IM via thoracotomy, (2) catheter-based IC balloon-occlusion (BO) with infusion into the distal left anterior descending (LAD) coronary artery, (3) IC perforated side-wall (SW) infusion into the LAD, or (4) non-selective IC via left main (LM) coronary artery infusion. Hearts were harvested and imaged using at 3T whole-body MRI scanner. In separate Yorkshire swine (n = 13), an adeno-associated virus (AAV) vector was similarly delivered, tissue harvested 4-6 weeks later, and viral DNA quantified from predefined areas at risk (apical LV/RV) vs. not at risk in a potential mid-LAD infarct model. Results were analyzed using pairwise Student's t-test.

RESULTS

IM delivery yielded the highest IO retention (16.0 ± 4.6% of left ventricular volume). Of the IC approaches, BO showed the highest IO retention (8.7 ± 2.2% vs. SW = 5.5 ± 4.9% and LM = 0%) and yielded consistent uptake in the porcine distal LAD territory, including the apical septum, LV, and RV. IM delivery was limited to the apex and anterior wall, without septal retention. For the AAV delivery, the BO was most efficient in the at risk territory (Risk: BO = 6.0 × 10-9, IM = 1.4 × 10-9, LM = 3.2 × 10-10 viral copies per μg genomic DNA) while all delivery routes were comparable in the non-risk territory (BO = 1.7 × 10-9, IM = 8.9 × 10-10, LM = 1.2 × 10-9).

CONCLUSIONS

Direct IM injection has the highest local retention, while IC delivery with balloon occlusion and distal infusion is the most effective IC delivery technique to target therapeutics to a heart territory most in risk from an infarct.

Development of a Multifunctional Needle for Percutaneous Heart Biopsy and Cell Therapy. A Technical Note

Validation of transendocardial injection as a method for delivering therapeutic agents to the diseased heart is increasing. Puncture heart biopsies should re-emerge as a possible alternative method to allow access to the myocardium and implantable biomaterial for cell therapy. Therefore, this work aims to present a percutaneous puncture device for biopsy and intramyocardial biomaterial injection, standardize the technique and attest to the safety of the method. The adaptation consists of creating myocardial microlesions that allow for better fixation of stem cells. The objective of this technical note covers only the development of the needle and the histological quality of the biopsies. It has not been used in humans yet.

Direct Myocardial Injection of Vectors

Gene therapy holds great promise as a targeted treatment of cardiovascular diseases, which remain a major cause of morbidity and mortality in contemporary societies. Selection of the appropriate vector delivery method is critical for efficient transduction in the myocardium. Direct myocardial delivery is a feasible and effective method that has been shown to exhibit enhanced gene expression compared to coronary infusion and pericardial delivery. It is one of the most widely used gene transfer methods in both animal studies and clinical trials. The advantages, which result from a delivery that avoids exposure to the blood and bypasses the endothelial barrier, are a high local concentration at the injection site and a decreased leakage to off-target organs. The vectors are injected either with an endomyocardial or an epicardial approach, either surgically or percutaneously. In this chapter, we present the different approaches of direct myocardial injection, their advantages and their realization method in preclinical large animal models of cardiovascular diseases.

Ultrasound-guided transthoracic intramyocardial injection in mice

Murine models of cardiovascular disease are important for investigating pathophysiological mechanisms and exploring potential regenerative therapies. Experiments involving myocardial injection are currently performed by direct surgical access through a thoracotomy. While convenient when performed at the time of another experimental manipulation such as coronary artery ligation, the need for an invasive procedure for intramyocardial delivery limits potential experimental designs. With ever improving ultrasound resolution and advanced noninvasive imaging modalities, it is now feasible to routinely perform ultrasound-guided, percutaneous intramyocardial injection. This modality efficiently and reliably delivers agents to a targeted region of myocardium. Advantages of this technique include the avoidance of surgical morbidity, the facility to target regions of myocardium selectively under ultrasound guidance, and the opportunity to deliver injectate to the myocardium at multiple, predetermined time intervals. With practiced technique, complications from intramyocardial injection are rare, and mice quickly return to normal activity on recovery from anesthetic. Following the steps outlined in this protocol, the operator with basic echocardiography experience can quickly become competent in this versatile, minimally invasive technique.

Adenoviral vector tethering to metal surfaces via hydrolyzable cross-linkers for the modulation of vector release and transduction

The use of arterial stents and other medical implants as a delivery platform for surface immobilized gene vectors allows for safe and efficient localized expression of therapeutic transgenes. In this study we investigate the use of hydrolyzable cross-linkers with distinct kinetics of hydrolysis for delivery of gene vectors from polyallylamine bisphosphonate-modified metal surfaces. Three cross-linkers with the estimated t1/2 of ester bonds hydrolysis of 5, 12 and 50 days demonstrated a cumulative 20%, 39% and 45% vector release, respectively, after 30 days exposure to physiological buffer at 37 °C. Transgene expression in endothelial and smooth muscles cells transduced with substrate immobilized adenovirus resulted in significantly different expression profiles for each individual cross-linker. Furthermore, immobilization of adenoviral vectors effectively extended their transduction effectiveness beyond the initial phase of release. Transgene expression driven by adenovirus-tethered stents in rat carotid arteries demonstrated that a faster rate of cross-linker hydrolysis resulted in higher expression levels at day 1, which declined by day 8 after stent implantation, while inversely, slower hydrolysis was associated with increased arterial expression at day 8 in comparison with day 1. In conclusion, adjustable release of transduction-competent adenoviral vectors from metallic surfaces can be achieved, both in vitro and in vivo, through surface immobilization of adenoviral vectors using hydrolyzable cross-linkers with structure-specific release kinetics.

Potential of gene therapy as a treatment for heart failure

Advances in understanding the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, make gene-based therapy a promising treatment option for heart conditions. Cardiovascular gene therapy has benefitted from recent advancements in vector technology, design, and delivery modalities. There is a critical need to explore new therapeutic approaches in heart failure, and gene therapy has emerged as a viable alternative. Advances in understanding of the molecular basis of myocardial dysfunction, together with the development of increasingly efficient gene transfer technology, has placed heart failure within reach of gene-based therapy. The recent successful and safe completion of a phase 2 trial targeting the cardiac sarcoplasmic/endoplasmic reticulum Ca2+ ATPase pump (SERCA2a) has the potential to open a new era for gene therapy for heart failure.