The assignee for this patent application is
Reporters obtained the following quote from the background information supplied by the inventors: "Pacemaker and defibrillator devices use electrical impulses to regulate beating of the heart. Current implantable artificial pacemakers and defibrillators rely on a programmable electronic device and wired electrodes to electrically stimulate and synchronize beating of the myocardium (pacemaker) or to correct cardiac arrhythmia (defibrillator). However, these implantable devices are unresponsive to autonomic heart rate modulation, require invasive surgical implantation and replacement every 5-10 years, are susceptible to temporary malfunction in the presence of magnets, e.g., metal detectors or MRI machines, or environmental noise, and increase the patient's inflammatory response and risk of infection. They have a limited battery life and their long-term use has been associated with permanent cardiac tissue damage. In addition, these electronic devices are often unsuitable for pediatric patients (see, e.g., emedicine.medscape.com/article/780825-overview).
"Furthermore, implantable electrical cardiac defibrillators function by delivering a large, brief electric shock to reset a tachycardic/fibrillating heart and restore normal beating. Like pacemakers, the defibrillators must be implanted surgically and are prone to mechanical failure. A major complaint of patients with implanted defibrillators is the extreme pain from the electric shock produced by the devices.
"Biological pacemakers are one alternative to artificial electrical pacing therapy. Biological pacemakers are responsive to autonomic modulation, require no external power source or replacement, present minimal inflammatory response, can be permanent, and can be autologous. Attempts at restoring cardiac automaticity with biologics have recently focused on two main approaches: gene therapy and cell transplantation (reviewed in M R Rosen et al., Anat. Rec. Part A 280A: 1046-1052, 2004). Gene therapy approaches introduce genes, such as the pacemaker gene, HCN2, directly into myocardial cells to restore or enhance automaticity. For example, adenovirus carrying an HCN2 construct has been injected into the left ventricular bundle branch system of canine hearts. Upon vagal stimulation, transgenic hearts demonstrated a more rapid heart rate than control hearts. Cell transplantation approaches involve transplanting isolated spontaneously active or genetically-engineered cells directly into the myocardium. For example, adult mesenchymal stem cells have been transformed with HCN2. The transformed stem cells were injected into the left ventricular anterior wall of a canine heart and were capable of stimulating heart rhythms (M R Rosen et al., Anat. Rec. Part A 280A: 1046-1052, 2004).
"These short-term studies demonstrate the potential of biological pacemakers. Biological defibrillators have not, as yet, been explored. However, for both technologies, miniaturized systems and a minimally invasive means to access and regulate the cellular devices would facilitate and optimize control and repair of cardiac function in patients. Thus, there is a need in the art for biological pacemakers and/or defibrillators which are less invasive and more effective in regulating beating of the heart."
In addition to obtaining background information on this patent application, NewsRx editors also obtained the inventor's summary information for this patent application: "The present invention provides a biologically engineered tissue comprising a population of pacing, e.g., cardiac cells, e.g., pacemaker cells, expressing a photosensitive membrane transport mechanism, such as a light-gated ion channel or a light-driven ion pump. The photosensitive membrane transport mechanism may advantageously be responsive to photostimulation, e.g., responsive to light of a particular wavelength(s). Thus, photostimulation of the membrane transport mechanism may advantageously affect membrane potential of the pacing cells, e.g., cardiac cells, e.g., pacemaker cells. For example, the pacing cells may be selectively and controllably depolarized or hyperpolarized in response to photostimulation.
"In one aspect of the invention, genetically engineered photosensitive tissues are provided. The genetically engineered photosensitive tissues include a population of pacing cells expressing a photosensitive membrane transport mechanism. The photosensitive membrane transport mechanism may include a light-gated ion channel and/or a light-driven ion pump. In one embodiment, the photosensitive membrane transport mechanism comprises a rhodopsin. In one embodiment the rhodopsin is selected from the group consisting of channelrhodopsin-1, channelrhodopsin-2, V-channelrhodopsin-1, halorhodopsin, and combinations thereof.
"In another aspect, the present invention provides methods of preparing genetically engineered photosensitive tissues. The methods include transfecting a population of cells selected from the group consisting of sinoatrial node cardiac cells, atrioventricular cardiac cells, cardiac conduction cells, cardiac progenitor cells, embryonic stem cells, induced pluripotent stem cells, adult mesenchymal stem cells, adult cardiac resident stem cells, and other adult stem cells, with a nucleic acid molecule encoding a photosensitive membrane transport mechanism. The photosensitive membrane transport mechanism may include a light-gated ion channel and/or a light-driven ion pump. In one embodiment, the photosensitive membrane transport mechanism comprises a rhodopsin. In one embodiment, the rhodopsin is selected from the group consisting of channelrhodopsin-1, channelrhodopsin-2, V-channelrhodopsin1, halorhodopsin, and combinations thereof.
"In yet another aspect, the present invention also provides photosensitive cardiac rhythm modulation tissue structures. The photosensitive cardiac rhythm modulation tissue structures include a flexible polymer layer and a genetically engineered photosensitive tissue which is attached to the flexible polymer layer.
"In one aspect, the present invention further provides photosensitive cardiac rhythm modulation systems. The photosensitive cardiac rhythm modulation systems include a photosensitive cardiac rhythm modulation tissue structure, a light source adapted to provide photostimulation to the photosensitive cardiac rhythm modulation tissue structure, and a sensor array. The photosensitive cardiac rhythm modulation systems may further comprise a power generator. In one embodiment, the light source is selected from the group consisting of a light emitting diode and a diode laser, and wherein the light source is coupled to an optical fiber.
"In one embodiment, the genetically engineered photosensitive tissue of a photosensitive cardiac pacemaker comprising a photosensitive cardiac rhythm modulation system is capable of depolarizing, generating an action potential, and beating in response to photostimulation. In another embodiment, the genetically engineered photosensitive tissue of a photosensitive cardiac defibrillator comprising a photosensitive cardiac rhythm modulation system is capable of hyperpolarizing, suppressing generation of an action potential, and suppressing beating in response to photostimulation.
"In another aspect, the present invention provides methods of treating cardiac dysfunction in a subject in need thereof. The methods include attaching a photosensitive cardiac rhythm modulation system in the vicinity of cardiac tissue of the subject. The photosensitive cardiac rhythm modulation systems may be capable of stimulating an action potential in response to photostimulation, capable of suppressing an action potential in response to photostimulation, or capable of both stimulating and suppressing an action potential in response to activation by light, wherein the wavelength of the light determines whether the action potential is stimulated or suppressed.
"In yet another aspect, the present invention provides methods of treating cardiac dysfunction in a subject in need thereof. The methods include the steps of contacting a photosensitive cardiac rhythm modulation tissue structure to cardiac tissue of the subject, allowing the genetically engineered photosensitive tissue to become electrically coupled with the cardiac tissue of the subject, and photostimulating the genetically engineered photosensitive tissue, thereby treating cardiac dysfunction in the subject.
"In yet another aspect, the present invention provides methods of treating cardiac dysfunction in a subject in need thereof. The methods include contacting a pacing cell of the subject with a nucleic acid molecule comprising a photosensitive membrane transport mechanism, and photostimulating the genetically engineered photosensitive tissue, thereby treating cardiac dysfunction in the subject.
"In one aspect, the present invention provides an in vitro model for electrophysiological studies of cardiac function. The in vitro model includes one or more photosensitive cardiac rhythm modulation tissue structures.
"In another aspect, the present invention provides methods for identifying a compound that modulates a cardiac tissue activity. The methods include the steps of providing an in vitro model for electrophysiological studies of cardiac function, contacting the model with a test compound, and evaluating the activity of the model in response to the test compound, thereby identifying a compound that modulates a cardiac tissue activity.
"The present invention is further described by the following detailed description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 is a schematic depicting one embodiment for the fabrication of a Muscle Thin Film (MTF). (1) The substrates are fabricated on a glass cover slip spin coated with PIPAAM that provides temporary adhesion to a PDMS top layer. The PDMS is patterned with ECM, fibronectin (FN) in this case, to elicit cell adhesion and growth. (2) Substrates are placed in culture with a cell suspension to allow pacemaking cells to settle and adhere to the surface. (3) MTFs are cultured in an incubator until the pacemaking cells form a two-dimensional tissue. (4) A desired shape is cut in the tissue/PDMS film. (5) The PIPAAM is dissolved by lowering the bath temperature below 35.degree. C., releasing the MTF. The cutout shape floats free or is gently peeled off. (6) The free-standing MTF is then used directly or modified further by folding into a three-dimensional conformation.
"FIG. 2 depicts spontaneous gap junction formation between cardiac myocytes cultured on a micropatterned substrate. Connexin 43 (white), sarcomere Z-lines are indicated by fluorescent staining of .alpha.-actinin (gray).
"FIG. 3 depicts in vitro testing of a pacing MTF. FIG. 3A depicts an engineered myocardium on a 128 channel optical mapping system. The optical fiber array is depicted with a white circular outline for each photodiode. The cells are stained with RH237, a potential-sensitive dye. Scale bar is 100 .mu.m. FIG. 3B depicts action potential traces recorded for each photodiode. FIG. 3C depicts an activation map illustrating the arrival time of the action potential at points in the tissue. FIG. 3D depicts isochrones mapping to the activation map are used to precisely calculate the action potential conduction velocity as it propagates through the tissue. FIG. 3E depicts time sequences showing when the action potential arrives at different parts of the tissue. In these experiments, the tissue was paced by bipolar point stimulation. When a pacing MTF is fixed onto the tissue, these activation maps are used to determine if the pacing MTF is electrically controlling the whole tissue construct. Calculations of the conduction velocity from the arrival times in the isochrones are used to verify gap-junction coupling between the pacing MTF and the myocardium. Local conduction velocity can be calculated from conduction velocity vector fields according to the method of Bayly et al. (IEEE Trans Biomed Eng, 45: 563-71, 1998).
"FIG. 4 depicts action potential wavefront propagation in paced tissues with different anisotropy ratios (AR). In this example, all tissues were stimulated with a point electrode in the center of the tissue. The optical signals were normalized by the action potential amplitude to represent the transmembrane voltage in color. For each frame, the gray scale bar on the left indicates the resting state with dark gray and the peak of the action potential with medium gray. The white trace on the bottom is from a recording made at the site marked by the white square. The top panels show the action potential wavefront propagation in an isotropic tissue (AR=1). The middle and bottom panels show the wavefront propagation in anisotropic tissues with AR=2 and AR=3, respectively.
"FIGS. 5A-5D depict in vitro studies, in which an engineered anisotropic tissue is cultured on a PDMS covered glass cover slip with a pacing MTF (wedge). FIG. 5A depicts anisotropic tissue (dark grey); Pacing MTF (wedge of cells over anisotropic tissue); Cell nuclei (light gray). FIG. 5B depicts an enlargement of the area in square in FIG. 5A. Upper cells are MTF and lower cells are anisotropic tissue. Gap junctions spontaneously form, electrically coupling the pacing MTF to the ventricular tissue. FIG. 5C depicts optical action potentials which are recorded from an area of engineered anisotropic tissue and display typical sharp upstrokes. FIG. 5D depicts optical action potentials recorded from an area of engineered anisotropic tissue in direct contact with a pacing MTF display slow diastolic depolarization due to the pacing current supplied by the MTF.
"FIG. 6 depicts two embodiments of an optical pacemaker. FIG. 6A depicts a basic optical pacemaker controlled by a sensor array. Light-activated pacemaker cells are stimulated by light transmitted from a light source through an optical fiber. The pacemaker cells will function as a pacemaker or defibrillator depending on the heterologous ion channels present. FIG. 6B depicts an optical pacemaker controlled by optical cellular sensor. Light-activated pacemaker cells are stimulated by light provided by light-producing cells and transmitted through an optical fiber.
"FIG. 7 depicts an embodiment of an optical pacemaker/defibrillator. Light of the appropriate wavelength is transmitted through optical fibers to either light-activated or light-silenced pacemaker cells to regulate cardiac function."
For more information, see this patent application: Parker,
Keywords for this news article include: Bioengineering, Biotechnology, Cardiology, Defibrillators, Engineering, Gene Therapy, Ion Channels, Medical Devices, Membrane Glycoproteins, Membrane Transport Proteins, Pacemakers,
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