Cardiac Gene Transfer Research Articles

Cardiac gene transfer of HGF is superior to TMR in inducing therapeutic coronary neoangiogenesis

Cardiac gene transfer of HGF is superior to TMR in inducing therapeutic coronary neoangiogenesis

High-efficiency, long-term cardiac expression of foreign genes in living mouse embryos and neonates.

The development of improved strategies for efficient and reproducible in vivo gene transfer into the murine heart will ultimately allow the intersection of somatic and germline gene transfer strategies to study complex features of cardiac biology and diseases. For embryonic gene transfer, an adenovirus vector expressing beta-galactosidase was injected in utero into the ventricular cavity of living embryos via microsurgical approaches. The injected embryos were developed to term, and efficient expression of the transgene was detected in all cell types in the heart. For postnatal cardiac gene transfer, adenovirus was injected into the cardiac ventricle of neonatal mice, resulting in efficient expression of the transgene in the outer layer of the myocardium as well as cardiomyocytes in the middle and inner layers of the cardiac wall. Mice examined after 3 weeks displayed a pattern of expression that completely mimicked the pattern seen after 3 days, and gene expression was also found after 6 months. The infected myocytes can be identified by coinfection of an adenovirus expressing green fluorescent protein without affecting their normal physiological function. We have developed a new strategy to achieve efficient and long-term foreign gene expression in both embryonic and postnatal mouse myocardium via direct intracardiac injection of recombinant adenovirus. The strategy should allow the functional assessment of the expression of dominantly acting exogenous genes, overexpression of wild-type genes, and Cre recombinase-mediated gene ablations at the single-cell level in the context of the intact adult mouse myocardium.

Efficient transmural cardiac gene transfer by intrapericardial injection in neonatal mice.

An efficient cardiac gene transfer technique in murine models would greatly facilitate the elucidation of the pathophysiology of cardiomyopathies and the development of genetic therapies. Direct myocardial injection or catheter-based intracoronary infusion is not easily achievable in mice and resultant transgene expression is often limited in distribution. A replication-defective, recombinant adenovirus encoding luciferase (5x10(9)pfu) or lacZ (4-5x10(10)particles/animal) was injected percutaneously into the pericardial cavity of 4-5 day old mice. Chemiluminescence assay for luciferase activity at 3 days post-injection revealed the highest activity in the heart (heart=288+/-110, lungs=19+/-5, liver=11+/-5 ng/gm tissue, n=11). X-gal staining of cryostat sections demonstrated widespread transmural lacZ expression in the left ventricle, interventricular septum, right ventricle, and atrial appendages, and the average fractional area of X-gal staining in a left ventricle was 66+/-16% (range 40-92%, n=21 sections). However, the long-term survival of these mice was compromised. Reduction in the injectate volume by 50% significantly improved survival but concurrently reduced lacZ expression. Significant lacZ expression was observed in the right ventricle and interventricular septum but left ventricular expression was predominantly epicardial, with variable myocardial penetration. At 2 months post-injection, lacZ expression persisted only in atrial tissues, pulmonary veins, and great vessels. Despite lack of persistent transgene expression in ventricular tissues, the high degree of transgene expression achieved may be sufficient to allow evaluation of short-term effects of specific genetic manipulations in the heart.

Efficient transmural cardiac gene transfer by intrapericardial injection in neonatal mice

Abstract An efficient cardiac gene transfer technique in murine models would greatly facilitate the elucidation of the pathophysiology of cardiomyopathies and the development of genetic therapies. Direct myocardial injection or catheter-based intracoronary infusion is not easily achievable in mice and resultant transgene expression is often limited in distribution. A replication-defective, recombinant adenovirus encoding luciferase (5×10 9 pfu) or lacZ (4–5×10 10 particles/animal) was injected percutaneously into the pericardial cavity of 4–5 day old mice. Chemiluminescence assay for luciferase activity at 3 days post-injection revealed the highest activity in the heart (heart=288±110, lungs=19±5, liver=11±5 ng/gm tissue, n =11). X-gal staining of cryostat sections demonstrated widespread transmural lacZ expression in the left ventricle, interventricular septum, right ventricle, and atrial appendages, and the average fractional area of X-gal staining in a left ventricle was 66±16% (range 40–92%, n =21 sections). However, the long-term survival of these mice was compromised. Reduction in the injectate volume by 50% significantly improved survival but concurrently reduced lacZ expression. Significant lacZ expression was observed in the right ventricle and interventricular septum but left ventricular expression was predominantly epicardial, with variable myocardial penetration. At 2 months post-injection, lacZ expression persisted only in atrial tissues, pulmonary veins, and great vessels. Despite lack of persistent transgene expression in ventricular tissues, the high degree of transgene expression achieved may be sufficient to allow evaluation of short-term effects of specific genetic manipulations in the heart.

Modulation of ventricular function through gene transfer in vivo.

We used a catheter-based technique to achieve generalized cardiac gene transfer in vivo and to alter cardiac function by overexpressing phospholamban (PL) which regulates the activity of the sarcoplasmic reticulum Ca2+ ATPase (SERCA2a). By using this approach, rat hearts were transduced in vivo with 5 x 10(9) pfu of recombinant adenoviral vectors carrying cDNA for either PL, beta-galactosidase (beta-gal), or modified green fluorescent protein (EGFP). Western blot analysis of ventricles obtained from rats transduced by Ad.PL showed a 2.8-fold increase in PL compared with hearts transduced by Ad.betagal. Two days after infection, rat hearts transduced with Ad.PL had lower peak left ventricular pressure (58.3 +/- 12.9 mmHg, n = 8) compared with uninfected hearts (92.5 +/- 3.5 mmHg, n = 6) or hearts infected with Ad.betagal (92.6 +/- 5.9 mmHg, n = 6). Both peak rate of pressure rise and pressure fall (+3, 210 +/- 298 mmHg/s, -2, 117 +/- 178 mmHg/s, n = 8) were decreased in hearts overexpressing PL compared with uninfected hearts (+5, 225 +/- 136 mmHg/s, -3, 805 +/- 97 mmHg/s, n = 6) or hearts infected with Ad.betagal (+5, 108 +/- 167 mmHg/s, -3, 765 +/- 121 mmHg/s, n = 6). The time constant of left ventricular relaxation increased significantly in hearts overexpressing PL (33.4 +/- 3.2 ms, n = 8) compared with uninfected hearts (18.5 +/- 1.0 ms, n = 6) or hearts infected with Ad.betagal (20.8 +/- 2.1 ms, n = 6). These differences in ventricular function were maintained 7 days after infection. These studies open the prospect of using somatic gene transfer to modulate overall cardiac function in vivo for either experimental or therapeutic applications.

In utero cardiac gene transfer via intraplacental delivery of recombinant adenovirus.

The relationship among the maternal, placental, and uniquely shunted embryonic circulation was explored to provide access to the embryonic cardiovascular system in utero. Manipulation of gene expression in the developing heart would be particularly useful for studying the effects of altered gene expression on cardiac development and in the etiology of congenital cardiac anomalies. Dye studies demonstrated that intraplacental injection allows direct access to the embryonic cardiac and systemic circulation. To evaluate the efficacy of cardiac gene transfer using this approach, replication-deficient recombinant adenoviral vectors encoding luciferase or beta-galactosidase as reporter genes were injected intraplacentally into embryonic day (E)12.5 murine embryos, an age at which the mass of the heart was observed to be large compared with other organs. Embryos were assayed for transgene expression at E15.5 and at birth. Survival rates at these times were similar among vector-injected and control groups. At E15.5 and at birth, luciferase activity within the heart was 9- and 23-fold higher, respectively, than in the remainder of the embryo, although levels of expression were generally lower at birth than during embryonic life. Beta-galactosidase expression was observed within all regions of the embryonic heart and was localized to approximately 15% of atrial and ventricular cells. Intraplacental delivery of adenovirus at embryonic day 12.5 results in somatic gene transfer to the murine embryonic heart, which persists at least until birth. The combination of intraplacental injection to directly access the fetal coronary circulation and injection at E12.5 when the mass of the heart is large compared with other organs results in transgene expression in cardiac cells. Intraplacental injections early in embryonic life may thus be useful to study the effects of temporal manipulation of gene expression on cardiac development and disease.

Ultrarapid, highly efficient viral gene transfer to the heart.

Gene therapy for common myocardial diseases will require effective and homogeneous gene delivery throughout the intact heart. We created two experimental models to identify and optimize parameters important for adenovirus-mediated cardiac gene transfer. In cultured rabbit ventricular myocytes, the percentage of infected cells increased with higher absolute numbers of virus particles, longer durations of virus exposure, physiological temperatures, and specific culture media compositions. Simulating the in vitro conditions, we delivered adenovirus to intact rabbit hearts by intracoronary perfusion. The percentage of infected cells increased with higher coronary flow rates, longer virus exposure times, and higher virus concentrations. Under optimal conditions, nearly 100% of myocytes expressed the reporter gene beta-galactosidase after ex vivo infection. This novel delivery method, the first to demonstrate virtually complete transduction of any intact organ, could be adapted to achieve widespread gene transfer in vivo.

Cardiac gene transfer by intracoronary infusion of adenovirus vector—mediated reporter gene in the transplanted mouse heart

This study introduces a model for intracoronary gene transfer in murine cardiac isografts using adenovirus vectors. This approach may offer an opportunity to modulate alloreactivity after cardiac transplantation. Donor hearts were infected via the coronary arteries with a volume of 10 9 plaque-forming units per milliliter of a recombinant adenovirus containing the β-galactosidase–encoding gene (Ad.CMVLacZ). In a control group, 200 μl of normal saline solution was infused. The grafts were stored in 4º C cold saline solution for 15 minutes, then transplanted heterotopically into syngeneic hosts (B10.BR). The grafts were harvested at 3, 7, 15, or 30 days ( n = 5 for each group) after transplantation, and β-galactosidase activity was assessed by histochemical staining (X-gal). All grafts were functioning when harvested. X-gal staining pattern was nonuniform with positive staining appearing in epicardial, myocardial, and endocardial cells, as well as in the vessel walls. The cells permissive to infection consisted predominantly of myocardial cells. The mean total numbers of β-gal–positive staining cells per slice were 68.7 ± 27.3 in the 3-day group, 330.4 ± 53.8 in the 7-day group, 151.3 ± 48.0 in the 15-day group, and 39.9 ± 10.8 in the 30-day group, thus peaking in the 7-day group ( p < 0.05). Control isografts ( n = 5), retrieved at day 30, revealed no staining activity. In conclusion, our model demonstrates that intracoronary gene transfer to the transplanted murine cardiac grafts is feasible at the time of harvest. Adenovirus-mediated gene transfer produces widespread gene expression which, though perhaps transient, does not adversely affect myocardial structure or function. This technology may allow modification of graft immunogenicity in the future through the production of therapeutic proteins sufficient to modulate local immune responses. (J T HORAC C ARDIOVASC S URG 1996;111:246-52)

The molecular and cellular biology of heart failure

We review recent publications that use molecular and cellular biology to explore the diagnosis and treatment of cardiovascular diseases that have relevance to heart failure. Familial hypertrophic cardiomyopathy has now been shown to be due to mutations not only in the previously described beta myosin heavy chain gene, but also in the troponin T and alpha-tropomyosin genes, thus providing some symmetry to the idea that this is a molecular disease of the sarcomere. The basis for a type of familial dilated cardiomyopathy without substantial skeletal muscle involvement, caused by a mutation in the dystrophin gene, has been explored. However, by-and-large, the disease basis for most patients with dilated cardiomyopathy remains a molecular mystery. The role of a polymorphism in the angiotensin-converting enzyme gene was examined as a risk factor for a number of cardiovascular diseases. In animal models, the hypothesis that the devolution from hypertrophy to heart failure includes alterations in the molecular direction of extracellular matrix production gained some support. The experimental foundation was laid this year for the concept of and approach to cardiomyocytoplasty--the molecular and cellular treatment of heart failure by augmentation, repair, or replacement of cardiac myocytes--by experiments in cardiac gene transfer and transgenic animals. Gene causes and cures for restenosis after angioplasty garnered considerable attention. As we gain greater understanding of the molecular basis for disease, we will also have to increase our wisdom in the application of genetic testing.