Selective regional myocardial infiltration by the percutaneous coronary venous route: A novel technique for local drug delivery

Stem cell therapy for cardiovascular disease: the demise of alchemy and rise of pharmacology

Regenerative medicine holds great promise as a way of addressing the limitations of current treatments of ischaemic disease. In preclinical models, transplantation of different types of stem cells or progenitor cells results in improved recovery from ischaemia. Furthermore, experimental studies indicate that cell therapy influences a spectrum of processes, including neovascularization and cardiomyogenesis as well as inflammation, apoptosis and interstitial fibrosis. Thus, distinct strategies might be required for specific regenerative needs. Nonetheless, clinical studies have so far investigated a relatively small number of options, focusing mainly on the use of bone marrow-derived cells. Rapid clinical translation resulted in a number of small clinical trials that do not have sufficient power to address the therapeutic potential of the new approach. Moreover, full exploitation has been hindered so far by the absence of a solid theoretical framework and inadequate development plans. This article reviews the current knowledge on cell therapy and proposes a model theory for interpretation of experimental and clinical outcomes from a pharmacological perspective. Eventually, with an increased association between cell therapy and traditional pharmacotherapy, we will soon need to adopt a unified theory for understanding how the two practices additively interact for a patient's benefit.

Non-surgical stem cell delivery strategies and in vivo cell tracking to injured myocardium

Heart failure is a major economic and public health problem. Despite the recent advances in drug therapy and coronary revascularization, the lost cardiomyocytes due to necrosis and apoptosis are not replaced by new myocardial tissue. Cell therapy is an interesting therapeutic option as it potentially improves contractility and restores regional ventricular function. Early clinical data demonstrated that cell transplantation, mainly delivered through non-surgical methods, is safe and feasible. However, several important issues need to be elucidated. This includes, next to determining the best cell type, the optimal delivery strategy, the biodistribution and the survival of implanted stem cells after transplantation. In this view, pre-clinical animal experiments are indispensable. Reporter genes, magnetic or radioactive labeling of stem cells have been developed to observe the fate and the distribution of transplanted cells using non-invasive imaging techniques. Several studies have demonstrated that these direct and non-direct labeling techniques may become an important tool in cell therapy. Integration of cell delivery and cell tracking will probably be a key for the success of cell therapy in patients. This review will provide a comprehensive overview on the various cell tracking and non-surgical cell delivery techniques, which are highly important in view of experimental and clinical studies.

Transvenous intramyocardial cellular delivery increases retention in comparison to intracoronary delivery in a porcine model of acute myocardial infarction

BACKGROUND

Clinical trials using intracoronary (IC) delivery of cells have addressed efficacy but the optimal delivery technique is unknown. Our study aimed to determine whether transvenous intramyocardial (TVIM) approach was advantageous for cellular retention in AMI.

METHODS

Domestic pigs (n = 4) underwent catheterization with coronary angiography and ventriculography prior to infarction and pre- and post-cells. Pigs underwent 90-minute balloon occlusion of the left anterior descending artery (LAD). After one week they were prepared for IC (n = 2) or TVIM (n = 2) delivery of bone marrow mononuclear cells (MNC) labeled with GFP. IC infusion used an over-the-wire catheter to engage the LAD and balloon inflation to prevent retrograde flow. Venography via the coronary sinus was used for TVIM delivery. The anterior interventricular vein was engaged with a guidewire allowing use of the TransAccess catheter that is outfitted with an ultrasound tip for visualization. Animals were sacrificed one hour after delivery and tissue was analyzed.

RESULTS

Procedures were performed without complication and monitoring was uneventful. 1 x 10(8) MNC were isolated from each bone marrow (BM) preparation and 1 x 10(7) MNC delivered. Ventriculography at one week revealed wall motion abnormalities consistent with an anterior AMI. TVIM and IC delivery revealed mean 452 cells per section and 235 cells per section on average, respectively, in the infarct zone (P = 0.01).

CONCLUSION

We have demonstrated that TVIM approach for cell delivery is feasible and safe. Moreover, this approach may provide an advantage over IC infusion in retention of the cellular product; however, larger studies will be necessary.

Coronary venous retroperfusion: an old concept, a new approach

The potential of the coronary veins for revascularization has been evaluated by many investigators for more than a century. The major hurdle has been the damage of veins during sudden exposure to arterial pressure. The solution to this problem has typically involved the use of intricate and complicated apparatus and devices, which has prevented routine clinical utility in the catheterization laboratory. This review examines this old concept from a new perspective and proposes a novel hypothesis to address previous shortcomings. We speculate on an approach that may serve to eliminate the edema and hemorrhage that result during venous retroperfusion as the pressure is suddenly increased to arterial values. We propose the rationale to increase the venous pressure to arterial values more gradually to allow prearterializations of the veins before full exposure of arterial pressure. Finally, we discuss various possible indications for this selective autoretroperfusion strategy to combat myocardial ischemia in cardiogenic shock patients, ST-elevation myocardial infarct patients, no-option patients, and beyond.

Cardiovascular gene delivery: The good road is awaiting

Atherosclerotic cardiovascular disease is a leading cause of death worldwide. Despite recent improvements in medical, operative, and endovascular treatments, the number of interventions performed annually continues to increase. Unfortunately, the durability of these interventions is limited acutely by thrombotic complications and later by myointimal hyperplasia followed by progression of atherosclerotic disease over time. Despite improving medical management of patients with atherosclerotic disease, these complications appear to be persisting. Cardiovascular gene therapy has the potential to make significant clinical inroads to limit these complications. This article will review the technical aspects of cardiovascular gene therapy; its application for promoting a functional endothelium, smooth muscle cell growth inhibition, therapeutic angiogenesis, tissue engineered vascular conduits, and discuss the current status of various applicable clinical trials.

Three catheter-based strategies for cardiac delivery of therapeutic gelatin microspheres

Gelatin hydrogel microspheres (GHMs) have been reported as novel non-viral vectors for gene or protein delivery (GHM therapy). However, the components of an effective catheter-based delivery strategy for GHM therapy are unknown. We evaluated the effectiveness of three catheter-based strategies for cardiac GHM therapy: (1) antegrade injection (AI) via coronary arteries; (2) retrograde injection (RI) via coronary veins; and (3) direct myocardial injection (DI) via the coronary sinus. AI distributed microspheres homogeneously throughout the target area with 73+/-11% retention. RI scattered microspheres non-homogenously with 22+/-8% retention. DI distributed microspheres in the needle-advanced area with 47+/-14% retention. However, despite high efficiency, AI did not show biological effects of inducing angiogenesis from basic fibroblast growth factor bound to GHMs. Furthermore, focal micro-infarctions, owing to micro-embolism of aggregated GHMs into small coronary arterioles, were detected in the AI group. Conversely, only RI and DI groups displayed increased coronary flow reserve. DI groups also demonstrated increased capillary density. These results suggest that RI and DI are effective for cardiac GHM therapy, while AI appears inappropriate owing to the risk of focal infarctions.

Enhancing myocardial plasmid expression by retrograde coronary venous delivery

Myocardial delivery of genes holds great promise for treating many heart diseases; however, the optimal delivery technique, which maximizes safety and efficacy, has not been established. Two delivery techniques were evaluated in swine; percutaneous retrograde coronary venous delivery (RCVD) and direct intramyocardial injection (IM). RCVD was performed in the anterior interventricular vein (AIV) with an end-hole occlusion balloon catheter. The plasmid gWiz, encoding beta-galactosidase (10 ml; 1 mg/ml), was injected using either manual high pressure (HP-RCVD; n = 5) or pressure wire-guided low pressure (LP-RCVD; n = 4). For the IM group (n = 4), beta-Gal plasmid (5 mg/ml) was injected at 10 sites (200 microl/site) in the anterior left ventricular wall. Animals were euthanized after 5 days. The percentage of beta-Gal expressing cells in the delivered region was higher in the HP-RCVD (0.26% +/- 0.05%) than the LP-RCVD (0.05% +/- 0.03%; P = 0.07) and IM groups (0.02% +/- 0.01%; P = 0.01). Myocardium from the HP-RCVD group contained 7- and 17-fold higher levels of beta-Gal activity than either LP-RCVD and IM groups, respectively (P = 0.05 for both). The results of this study confirm the safety and efficacy of RCVD for myocardial gene delivery.

Radiolabeled Cell Distribution After Intramyocardial, Intracoronary, and Interstitial Retrograde Coronary Venous Delivery

Background— Several clinical studies are evaluating the therapeutic potential of delivery of various progenitor cells for treatment of injured hearts. However, the actual fate of delivered cells has not been thoroughly assessed for any cell type. We evaluated the short-term fate of peripheral blood mononuclear cells (PBMNCs) after intramyocardial (IM), intracoronary (IC), and interstitial retrograde coronary venous (IRV) delivery in an ischemic swine model.

Methods and Results— Myocardial ischemia was created by 45 minutes of balloon occlusion of the left anterior descending coronary artery. Six days later, 10 7 111 indium-oxine–labeled human PBMNCs were delivered by IC (n=5), IM (n=6), or IRV (n=5) injection. The distribution of injected cells was assessed by γ-emission counting of harvested organs. For each delivery method, a significant fraction of delivered cells exited the heart into the pulmonary circulation, with 26±3% (IM), 47±1% (IC), and 43±3% (IRV) of cells found localized in the lungs. Within the myocardium, significantly more cells were retained after IM injection (11±3%) compared with IC (2.6±0.3%) ( P <0.05) delivery. IRV delivery efficiency (3.2±1%) trended lower than IM infusion for PBMNCs, but this difference did not reach significance. The IM technique displayed the greatest variability in delivery efficiency by comparison with the other techniques.

Conclusions— The majority of delivered cells is not retained in the heart for each delivery modality. The clinical implications of these findings are potentially significant, because cells with proangiogenic or other therapeutic effects could conceivably have effects in other organs to which they are not primarily targeted but to which they are distributed. Also, we found that although IM injection was more efficient, it was less consistent in the delivery of PBMNCs compared with IC and IRV techniques.

Testing clinical therapeutic angiogenesis using basic fibroblast growth factor (FGF-2)

Therapeutic angiogenesis represents an attempt to relieve inadequate blood flow by the directed growth and proliferation of blood vessels. Neovascularization is a complex process involving multiple growth factors, receptors, extracellular matrix glycoproteins, intracellular and extracellular signaling pathways, and local and bone-marrow-derived constituent cells, all responding to a symphonic arrangement of temporal and spatial cues. In cardiovascular disease, patients with refractory angina and lower extremity intermittent claudication seem most amenable to early tests of therapeutic angiogenesis. Monotherapy with the recombinant protein basic fibroblast growth factor (FGF-2) has been tested in six human trials. These have shown provisional safety, and two have provided 'proof of concept' for the strategy of therapeutic angiogenesis. One large randomized phase II trial failed to show significant efficacy in coronary artery disease. Another showed significant efficacy in peripheral artery disease, although the magnitude of benefit was disappointing at the dose tested. This overview details the suitable clinical trial design and further steps toward the clinical development of FGF-2.

Myocardial gene transfer by selective pressure-regulated retroinfusion of coronary veins

OBJECTIVES

We sought to study adenoviral gene delivery using percutaneous selective pressure-regulated retroinfusion and to compare it directly with surgical and percutaneous intramyocardial delivery (PIMD) for the first time.

BACKGROUND

Intramyocardial delivery (IMD) has been recommended to be the preferred gene delivery strategy so far. However, surgical and percutaneous intramyocardial injection lead to incomplete retention of the injected viral vectors and to limited spatial myocardial distribution. Percutaneous selective pressure-regulated retroinfusion of the coronary veins was developed recently to provide an effective and more homogenous regional myocardial gene transfer.

METHODS

In 15 pigs, adenoviral vectors (Ad2-CMV beta-galactosidase [beta-gal] 5 x 10(9) pfu) were applied via surgical IMD (n = 5), PIMD (n = 5), and selective pressure-regulated retroinfusion (n = 5). Seven days after gene transfer, myocardial beta-gal expression was measured by ELISA.

RESULTS

Selective retroinfusion into the anterior cardiac vein substantially increased reporter gene expression (1,039 +/- 79 pg beta-gal/mg protein) in the targeted left anterior descending coronary artery territory when compared with surgical (448 +/- 127, p < 0.05) and PIMD (842 +/- 145, p < 0.05). Both IMD approaches showed an inhomogenous beta-gal expression, particularly along the injection sites, while retroinfusion resulted in a more homogenous transmural gene expression.

CONCLUSIONS

Percutaneous selective pressure-regulated retroinfusion compares favorably with surgical and percutaneous intramyocardial injection techniques by providing a more homogenous and even more efficient adenoviral gene delivery.

Evaluation of high-pressure retrograde coronary venous delivery of FGF-2 protein

Delivery of angiogenic factors to ischemic myocardium remains a practical challenge. We evaluated the efficiency and efficacy of delivery of fibroblast growth factor-2 (FGF-2) protein via high-pressure retrograde injection into the anterior interventricular vein (AIV) in a porcine model of chronic myocardial ischemia. Labeled FGF-2 protein was delivered to the myocardium of three pigs via the AIV and the left anterior descending (LAD) coronary artery in three others. At 1 hr, the amount of protein in the left ventricle and the LAD region was quantified. Copper stents were implanted in the LAD of 25 pigs, resulting in chronic myocardial ischemia. At 4 weeks, microsphere-derived myocardial blood flow was assessed at rest and during pacing. In eight pigs (AIV FGF), FGF-2 protein (6 microg/kg) was delivered via high-pressure retrograde injection into the AIV. Six pigs (intracoronary FGF) received the same amount of FGF-2 by intracoronary delivery. Five pigs (AIV saline) received a placebo injection into the AIV and six pigs (control) served as controls. Four weeks later, myocardial blood flow was reassessed. At 1 hr, significantly more FGF remained in the left ventricle (1.3 vs. 0.82 microg; P < 0.04) and in the LAD region (1.2 vs. 0.64 microg; P = 0.03) after AIV compared to intracoronary delivery. Four weeks after treatment, resting LAD blood flow (normalized to right ventricular flow) improved slightly in the AIV FGF and intracoronary FGF arms (1.32-1.37 for both; P = 0.11), while it decreased significantly in the AIV saline (1.32-1.23; P = 0.02) and the control arms (1.32-1.19; P = 0.0004). Pacing LAD blood flow decreased significantly in the control arm (1.30-1.23; P < 0.05), but did not change significantly in the other three arms. High-pressure retrograde injection into the AIV may represent an efficient and effective means for delivering angiogenic factors to ischemic myocardium.

Widespread regional myocardial transfection by plasmid encoding Del-1 following retrograde coronary venous delivery

This study quantifies myocardial transfection following percutaneous retrograde coronary venous delivery (RCVD) of a plasmid encoding human Del-1. RCVD of Del-1, GFP plasmid, or marker dye was conducted in 14 pigs. After selective cannulation of a coronary vein, a delivery site was confirmed by contrast injection and myocardial blush. Ten milliliters of plasmid hDel-1 or GFP was administered. Animals were euthanized 3 and 7 days post-RCVD. hDel-1 gene expression was evaluated by quantitative RT-PCR. An average myocardial expression of 4.5 x 10(5) copies hDel-1/microg total RNA was observed within the approximately 5 x 5 cm(2) target tissue of the left ventricle. GFP expression was detected by fluorescent microscopy. hDel-1 protein expression was confirmed by immunohistochemistry. Regionalized myocardial expression was found in all pigs. hDel-1 RNA was not found in distant tissues except in the three pigs with prominent venovenous washout (PVW). These levels were 3 to 4 log unites lower than those found in myocardium. Single retrograde coronary venous administration resulted in efficient regional myocyte transfection of hDel-1 and GFP. This method may be useful and clinically feasible for myocardial angiogenesis therapy.