Drug – bio-affecting and body treating compositions – Whole live micro-organism – cell – or virus containing – Genetically modified micro-organism – cell – or virus
Reexamination Certificate
2000-07-12
2004-08-17
Crouch, Deborah (Department: 1632)
Drug, bio-affecting and body treating compositions
Whole live micro-organism, cell, or virus containing
Genetically modified micro-organism, cell, or virus
C424S093100, C424S093200, C514S04400A
Reexamination Certificate
active
06776987
ABSTRACT:
BACKGROUND OF THE INVENTION
The natural pacemaker of the mammalian heart is the sinoatrial node (SA node) which is located in the high right atrium, and which comprises specialized pacemaker cells that generate electrical impulses characterized by an intrinsic rhythm. The electrical impulse, or pacemaker potential results from the spontaneous depolarization (a bioelectrical process involving the influx and egress of ions which reduces a membrane potential to a less negative value) of the cardiomyocytes within the SA node. This depolarization spreads from the sinus node through the surrounding atrial tissue and then into the atrial-ventricular node (AV node) before proceeding into the ventricular conduction system. Cardiac chronotropic incompetence resulting from cardiac conduction pathway dysfunction results in abnormalities of the cardiac cycle which are commonly referred to as arrhythmias.
It has been demonstrated that &bgr;-adrenergic receptors (&bgr;AR) regulate cardiac myocyte inotropic and chronotropic responses through a G protein-linked signaling pathway (Holmer, S. R., and Homcy, C. J.,
Circulation
, 84(5):1891-1902 (1991); Inglese, J. et al.,
J Biol Chem
. 268(32):23735-23738 (1993); Lefkowitz, R. J., and Caron, M. G.,
J Biol Chem
. 263(11):4993-6 (1988)). These signaling pathways involve both G
&agr;s
-direct and cAMP-mediated interactions with ion channels involved in myocyte depolarization. Stimulation of &bgr;AR increases heart rate as well as cardiac inotropic force. Conversely, blockade of &bgr;AR decreases heart rate and cardiac contractility. Cardiac chronotropic incompetence is associated with an increased prevalence of morbidity and mortality.
The majority of the causes of chronotropic incompetence require the implantation of an electronic pacemaker, either temporarily or permanently. The dangers of such surgical procedures are well known. Furthermore, electronic pacemaker devices are subject to failure, which necessitates subsequent surgical procedures to replace the defective device. Future treatments for chronotropic incompetence may be based on therapeutics (biological pacemakers) which can specifically enhance the pacemaker potential of endogenous cardiac tissue. Therefore, it is useful to provide novel compositions and alternative methods to alleviate chronotropic incompetence without the necessity of surgical intervention.
SUMMARY OF THE INVENTION
The present invention relates to compositions and methods for regulating heart rate comprising localized introduction (e.g., delivery) of one or more exogenous genes to cardiac tissue. Specifically encompassed by the present invention are methods employing gene therapy strategies to provide molecular-mediated or cellular-based biological pacemakers to treat cardiac chronotropic and conduction disorders. The resulting ability to reconstitute the function of defective &bgr;-adrenergic signaling cascade in the myocardial tissue localized to the SA node of patients with arrhythmias, cardiac disease, or age-associated myocardial dysfunction offers great hope for the reduction of morbidity and mortality.
As described herein, a murine cDNA chronotropic test system was developed to evaluate the effects of expressing the human &bgr;
2
-adrenergic receptor (&bgr;
2
AR) in mice under in vitro, ex vivo and finally in vivo conditions. The ability of &bgr;
2
AR gene therapy to restore the normal function of endogenous cardiac tissue was further evaluated in a direct porcine cardiac gene therapy system. More specifically, the present invention describes a gene therapy strategy which utilizes localized expression of biological pacemakers to restore the function of the &bgr;-adrenergic signaling cascade. The strategy results in improved cardiac performance and is a useful modality to restore the chronotropic and inotropic responsiveness of dysfunctional or senescent mammalian cardiac tissue.
In one embodiment, the biological cardiac pacemaker is a molecularly-mediated pacemaker. The molecularly-mediated pacemaker is an expression construct comprising at least one gene encoding a cellular protein which either upregulates heart rate, alters cardiac rhythm, or encodes a receptor protein or signal transduction molecule which is essential to normal physiologic cardiac conductance. The gene, or genes, are operably linked to expression control sequences. The expression construct comprising the molecularly-mediated pacemaker can mediate either transient or stable expression. For example, the molecularly-mediated pacemakers can be transiently expressed, and can comprise at least one gene selected from the group consisting of a &bgr;
2
AR gene, a&bgr;
1
AR gene, and a G
&agr;s
gene. The gene can encode either the endogenous protein or a heterologous protein which is sufficiently homologous to the endogenous protein to possess biological activity in the recipient host cell. In an alternative embodiment, the molecularly-mediated pacemaker can comprise at least one gene selected from the above listed group operably linked to expression control sequences suitable for transient expression under the control of a cardiac tissue specific promoter, which can be either constitutive or inducible. In a further embodiment the cardiac tissue promoter can be specific for atrial tissue.
The invention also pertains to a cellular-based biological cardiac pacemaker utilizing genetically modified cells. A cellular-based cardiac pacemaker can comprise at least one cell transfected or transduced with at least one gene that upregulates heart rate or alters cardiac rhythm, for example a &bgr;
2
AR gene a &bgr;
1
AR gene or a G
&agr;s
gene.
The invention also encompasses methods of regulating in vivo cardiac pacemaking (chronotropic) activity in a mammal by introducing one of the biologic cardiac pacemakers described herein into the SA node region of an endogenous mammalian heart. The mammal for example be a human. The biological pacemaker is introduced into the heart of the mammal, for example, into the right atrium at a site which is localized to a region surrounding the sinoatrial node. The chronotropic method can employ a molecularly-mediated cardiac biological pacemaker comprising at least one gene that upregulates heart rate or alters cardiac rhythm under the control of expression control elements which mediate either transient expression or stable expression, which is either constitutive or inducible.
Cardiac pacemaking activity can also be controlled by a method employing a cellular-based cardiac biological pacemaker comprising at least one myocyte transfected or transduced with at least one gene that upregulates heart rate or alters cardiac rhythm introduced (transplanted or grafted) into the SA node region of the right atria of the recipient host mammal.
The cardiac chronotropy methods described herein can be used for an individual suffering from cardiac conductive tissue incompetence (arrhythmias) indicative of a underlying disorder of cardiac impulse generation, or to treat an older patient experiencing age-related defects in cardiac performance. For example, the method may be useful in clinical conditions characterized by an abnormal sinus rhythm including but not limited to individuals having sick sinus syndrome, sinus bradycardia, or heartblock.
The methods can also be used for permanently regulating cardiac pacemaking activity in a mammal by introducing a stable cellular-based cardiac pacemaker comprising at least one myocyte transfected or transduced with at least one gene that upregulates heart rate or alters cardiac rhythm, or by introducing an molecularly-mediated cardiac pacemaker transcriptionally regulated for stable expression under the control of an inducible promoter.
The invention also encompasses methods of enhancing the basal heart rate of a mammal by delivery into the mammal of a biological pacemaker comprising exogenous genes which upregulate heart rate or alters cardiac chronotropic or inotropic responsiveness. The invention further encompasses methods of enhancing (upregulating) inotropic responsiveness (cardiac functio
Edelberg Jay M.
Rosenberg Robert D.
Crouch Deborah
Hamilton Brook Smith & Reynolds P.C.
Massachusetts Institute of Technology
Ton Thai-an N.
LandOfFree
Enhancement of cardiac chronotropy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Enhancement of cardiac chronotropy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Enhancement of cardiac chronotropy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3325742