Processes are described for obtaining high levels of gene expression in primates after injection of nucleic acid to the liver via the lumen of the hepatic vein. The described process results in high level of gene expression with transient increases in liver enzymes.

Description of the Invention

FIELD OF THE INVENTION

The invention generally relates to techniques for transferring genes into mammalian parenchymal cells in vivo. More particularly, a method is provided for transfecting hepatic cells with polynucleotides delivered intravascularly under pressure.

BACKGROUND OF THE INVENTION

It was first observed that the in vivo injection of plasmid DNA into muscle enabled the expression of foreign genes in the muscle (Wolff et al. Direct gene transfer into mouse muscle in vivo. Science 1990; 247:1465-1468.). Since that report, several other studies have reported the ability for foreign gene expression following the direct injection of DNA into the parenchyma of other tissues. Naked DNA was expressed following its injection into cardiac muscle (Acsadi et al. Direct gene transfer and expression into rat heart in vivo. The New Biologist 1991, 3(1), 71-81), pig epidermis (Hengge et al. Nature Genetics 1995, 10:161-166), rabbit thyroid (Sikes et al. Hum. Gene Ther. 1994, 5, 837), lung by intratracheal injection (Meyer et al. Gene Ther. 2, 450, 1995), into arteries using a hydrogel-coated angioplasty balloon (Riessen et al, Human Gene Ther. 1993, 4, 749; Chapman et al. Circ. Res. 1992, 71, 27), melanoma tumors (Vile et al. Cancer Res. 1993, 53, 962) and rat liver (Malone et al. JBC 1994, 269:29903-29907; Hickman Human Gene Therapy 1994, 5:1477-1483).

Another important target tissue for gene therapy is the mammalian liver, given its central role in metabolism and the production of serum proteins. A variety of techniques have been developed to transfer genes into the liver. Cultured hepatocytes have been genetically modified by retroviral vectors (Wolff et al. PNAS 1987, 84:3344-3348; Ledley et al. PNAS 1987, 84:5335-53397) and re-implanted back into the livers in animals and in people (Chowdhury et al. Science 1991, 254, 1802; Grossman et al. Nature Genetics 1994, 6, 335). Retroviral vectors have also been delivered directly to livers in which hepatocyte division was induced by partial hepatectomy (Kay et al Hum Gene Ther. 1992, 3:641-647; Ferry et al. PNAS 1991, 88:8377-8381; Kaleko et al. Hum Gene Ther. 1991, 2:27-321). The injection of adenoviral vectors into the portal or systemic circulatory systems leads to high levels of foreign gene expression that is transient (Stratford-Perricaudet et al. Hum. Gene Ther. 1990, 1, 241; Jaffe et al. Nat. Genet. 1992, 1, 372; Li et al. Hum. Gene Ther. 1993, 4, 403). Non-viral transfer methods have included polylysine complexes of asialoglycoproteins that are injected into the system circulation Wu et al. J. Biol. Chem. 1988, 263:14621-14624).

Foreign gene expression has also been achieved by repetitively injecting naked DNA in isotonic solutions into the liver parenchyma of animals treated with dexamethasone (Malone et al. JBC 1994, 269:29903-29907; Hickman Human Gene Therapy 1994, 5:1477-1483). Plasmid DNA expression in the liver has also been achieved via liposomes delivered by tail vein or intraportal routes (Kaneda et al. J. Biol. Chem. 1989, 264:12126-12129; Soriano et al. PNAS 1983, 80:7128-7131; Kaneda et al. Science 1989, 243:375-378).

Despite this progress, there is still a need for a gene transfer method that can efficiently and safely cause the expression of foreign genes in the liver in a and/or repetitive manner.

SUMMARY OF THE INVENTION

The present invention provides for the transfer of polynucleotides into parenchymal cells within tissues in situ and in vivo. An intravascular route of administration enables a prepared polynucleotide to be delivered to the parenchymal cells more evenly distributed and more efficiently expressed than direct parenchymal injections. The efficiency of polynucleotide delivery and expression was increased substantially by increasing the permeability of the tissue's blood vessel. This was done by increasing the intravascular hydrostatic (physical) pressure and/or increasing the osmotic pressure. Expression of a foreign DNA was obtained in mammalian liver by intraportally injecting plasmid DNA in a hypertonic solution and transiently clamping the hepatic vein/inferior vena cava. Optimal expression was obtained by clamping the portal vein and injecting the hepatic vein/inferior vena cava.

A process is described for delivering a polypeptide into a parenchymal cell in a mammal, comprising, transporting the polynucleotide into a vessel communicating with the parenchymal cell of the mammal such that the polynucleotide is transfected into the parenchymal cell.

A process for delivering a coded polynucleotide into a parenchymal cell of a mammal for expression of a protein, comprising, transporting the polynucleotide to a vessel containing a fluid and having a permeable wall; and, increasing the permeability of the wall for a time sufficient to complete delivery of the polynucleotide.

DETAILED DESCRIPTION

The term polynucleotide is a term of art that refers to a string of at least two base-sugar-phosphate combinations. Nucleotides are the monomeric units of nucleic acid polymers. The term includes deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in the form of an oligonucleotide messenger RNA, anti-sense, plasmid DNA, parts of a plasmid DNA or genetic material derived from a virus. A polynucleotide is distinguished, here, from a oligonucleotide by containing more than 120 monomeric units. Anti-sense is a polynucleotide that interferes with the function of DNA and/or RNA. A polynucleotide is considered in this specification to include a non-natural polynucleotide (not occurring in nature), for example: a derivative of natural nucleotides such as phosphothionates or peptide nucleic acids.

A polynucleotide can be delivered to a cell in order to produce a cellular change that is therapeutic. The delivery of polynucleotides or other genetic material for therapeutic purposes (the art of improving health in an animal including treatment or prevention of disease) is gene therapy. The polynucleotides are coded to express a whole or partial protein, or may be anti-sense, and can be delivered either directly to the organism in situ or indirectly by transfer to a cell that is then transplanted into the organism. The protein can be missing or defective in an organism as a result of genetic, inherited or acquired defect in its genome.

For example, a polynucleotide may be coded to express the protein dystrophin that is missing or defective in Duchenne muscular dystrophy. The coded polynucleotide is delivered to a selected group or groups of cells and incorporated into those cell's genome or remain apart from the cell's genome. Subsequently, dystrophin is produced by the formerly deficient cells. Other examples of imperfect protein production that can be treated with gene therapy include the addition of the protein clotting factors that are missing in the hemophilias and enzymes that are defective in inborn errors of metabolism such as phenylalanine hydroxylase.

A delivered polynucleotide can also be therapeutic in acquired disorders such as neurodegenerative disorders, cancer, heart disease, and infections. The polynucleotide has its therapeutic effect by entering the cell. Entry into the cell is required for the polynucleotide to produce the therapeutic protein, to block the production of a protein, or to decrease the amount of a RNA.

Additionally, a polynucleotide can be delivered to block gene expression. Such polynucleotides can be anti-sense by preventing translation of a messenger RNA or could block gene expression by preventing transcription of the gene. Small inhibiting RNA (siRNA) can also be used to inhibit gene expression. Preventing both RNA translation as well as DNA transcription is considered preventing expression. Transcription can be blocked by the polynucleotide binding to the gene as a duplex or triplex. It could also block expression by binding to proteins that are involved in a particular cellular biochemical process.

Polynucleotides may be delivered that recombine with genes. The polynucleotides may be DNA, RNA, hybrids and derivatives of natural nucleotides. Recombine is the mixing of the sequence of a delivered polynucleotide and the genetic code of a gene. Recombine includes changing the sequence of a gene.

Delivery of a polynucleotide means to transfer a polynucleotide from a container outside a mammal to within the outer cell membrane of a cell in the mammal. The term transfection is used herein, in general, as a substitute for the term delivery, or, more specifically, the transfer of a polynucleotide from directly outside a cell membrane to within the cell membrane. If the polynucleotide is a primary RNA transcript that is processed into messenger RNA, a ribosome translates the messenger RNA to produce a protein within the cytoplasm. If the polynucleotide is a DNA, it enters the nucleus where it is transcribed into a messenger RNA that is transported into the cytoplasm where it is translated into a protein. The polynucleotide contains sequences that are required for its transcription and translation. These include promoter and enhancer sequences that are required for initiation. DNA and thus the corresponding messenger RNA (transcribed from the DNA) contains introns that must be spliced, poly A addition sequences, and sequences required for the initiation and termination of its translation into protein. Therefore if a polynucleotide expresses its cognate protein, then it must have entered a cell.

A therapeutic effect of the protein in attenuating or preventing the disease state can be accomplished by the protein either staying within the cell, remaining attached to the cell in the membrane or being secreted and dissociating from the cell where it can enter the general circulation and blood. Secreted proteins that can be therapeutic include hormones, cytokines, growth factors, clotting factors, anti-protease proteins (e.g. alpha-antitrypsin) and other proteins that are present in the blood. Proteins on the membrane can have a therapeutic effect by providing a receptor for the cell to take up a protein or lipoprotein. For example, the low density lipoprotein (LDL) receptor could be expressed in hepatocytes and lower blood cholesterol levels and thereby prevent atherosclerotic lesions that can cause strokes or myocardial infarction. Therapeutic proteins that stay within the cell can be enzymes that clear a circulating toxic metabolite as in phenylketonuria. They can also cause a cancer cell to be less proliferative or cancerous (e.g. less metastatic). A protein within a cell could also interfere with the replication of a virus.

The delivered polynucleotide can stay within the cytoplasm or nucleus apart from the endogenous genetic material. Alternatively, the polynucleotide could recombine (become a part of) the endogenous genetic material. For example, DNA can insert into chromosomal DNA by either homologous or non-homologous recombination.

Parenchymal cells are the distinguishing cells of a gland or organ contained in and supported by the connective tissue framework. The parenchymal cells typically perform a function that is unique to the particular organ. The term "parenchymal" often excludes cells that are common to many organs and tissues such as fibroblasts and endothelial cells within the blood vessels.

In a liver organ, the parenchymal cells include hepatocytes, Kupffer cells and the epithelial cells that line the biliary tract and bile ductules. The major constituent of the liver parenchyma are polyhedral hepatocytes (also known as hepatic cells) that presents at least one side to an hepatic sinusoid and apposed sides to a bile canaliculus. Liver cells that are not parenchymal cells include cells within the blood vessels such as the endothelial cells or fibroblast cells.

In striated muscle, the parenchymal cells include myoblasts, satellite cells, myotubules, and myofibers. In cardiac muscle, the parenchymal cells include the myocardium also known as cardiac muscle fibers or cardiac muscle cells and the cells of the impulse connecting system such as those that constitute the sinoatrial node, atrioventricular node, and atrioventricular bundle.

In a pancreas, the parenchymal cells include cells within the acini such as zymogenic cells, centroacinar cells, and basal or basket cells and cells within the islets of Langerhans such as alpha and beta cells.

In spleen, thymus, lymph nodes and bone marrow, the parenchymal cells include reticular cells and blood cells (or precursors to blood cells) such as lymphocytes, monocytes, plasma cells and macrophages.

In the nervous system which includes the central nervous system (the brain and spinal cord) peripheral nerves, and ganglia, the parenchymal cells include neurons, glial cells, microglial cells, oligodendrocytes, Schwann cells, and epithelial cells of the choroid plexus.

In the kidney, parenchymal cells include cells of collecting tubules and the proximal and distal tubular cells. In the prostate, the parenchyma includes epithelial cells.

In glandular tissues and organs, the parenchymal cells include cells that produce hormones. In the parathyroid glands, the parenchymal cells include the principal cells (chief cells) and oxyphilic cells. In the thyroid gland, the parenchymal cells include follicular epithelial cells and parafollicular cells. In the adrenal glands, the parenchymal cells include the epithelial cells within the adrenal cortex and the polyhedral cells within the adrenal medulla.

In the parenchyma of the gastrointestinal tract such as the esophagus, stomach, and intestines, the parenchymal cells include epithelial cells, glandular cells, basal, and goblet cells.

In the parenchyma of lung, the parenchymal cells include the epithelial cells, mucus cells, goblet cells, and alveolar cells.

In fat tissue, the parenchymal cells include adipose cells or adipocytes. In the skin, the parenchymal cells include the epithelial cells of the epidermis, melanocytes, cells of the sweat glands, and cells of the hair root.

In cartilage, the parenchyma includes chondrocytes. In bone, the parenchyma includes osteoblasts, osteocytes, and osteoclasts.

An intravascular route of administration enables a polynucleotide to be delivered to parenchymal cells more evenly distributed and more efficiently expressed than direct parenchymal injections. Intravascular herein means within a hollow tubular structure called a vessel that is connected to a tissue or organ within the body. Within the cavity of the tubular structure, a bodily fluid flows to or from the body part. Examples of bodily fluid include blood, lymphatic fluid, or bile. Examples of vessels include arteries, arterioles, capillaries, venules, sinusoids, veins, lymphatics, and bile ducts. The intravascular route includes delivery through the blood vessels such as an artery or a vein.

Polypeptide refers to a linear series of amino acid residues connected to one another by peptide bonds between the alpha-amino group and carboxy group of contiguous amino acid residues.

Protein refers to a linear series of greater than 50 amino acid residues connected one to another as in a polypeptide.

Vectors are polynucleic molecules originating from a virus, a plasmid, or the cell of a higher organism into which another nucleic fragment of appropriate size can be integrated without loss of the vectors capacity for self- replication; vectors introduce foreign DNA into host cells, where it can be reproduced. Examples are plasmids, cosmids, and yeast artificial chromosomes; vectors are often recombinant molecules containing DNA sequences from several sources. A vector includes a viral vector: for example, adenovirus (icosahedral (20-sided) virus that contains; there are over 40 different adenovirus varieties, some of which cause the common cold) DNA; adenoassociated viral vectors (AAV) which are derived from adenoassociated viruses and are smaller than adenoviruses; and retrovirus (any virus in the family Retroviridae that has RNA as its nucleic acid and uses the enzyme reverse transcriptase to copy its genome into the DNA of the host cell's chromosome; examples include VSV G and retroviruses that contain components of lentivirus including HIV type viruses).

Afferent blood vessels of organs are defined as vessels which are directed towards the organ or tissue and in which blood flows towards the organ or tissue under normal physiologic conditions. Conversely, the efferent blood vessels of organs are defined as vessels which are directed away from the organ or tissue and in which blood flows away from the organ or tissue under normal physiologic conditions. In the liver, the hepatic vein is an efferent blood vessel since it normally carries blood away from the liver into the inferior vena cava. Also in the liver, the portal vein and hepatic arteries are afferent blood vessels in relation to the liver since they normally carry blood towards the liver.

B. Delivery of Polynucleotides

In a preferred embodiment of the present invention, a naked polynucleotide is delivered into a liver blood vessel at distal or proximal points. A liver blood vessel includes the portal venous system which transports blood from the gastrointestinal tract and other internal organs (e.g. spleen, pancreas and gall bladder) to the liver. Another liver blood vessel is the hepatic vein. The hepatic vein may also be reached via the inferior vena cava or another blood vessel that ultimately connects to the liver. A needle or catheter is used to inject the polynucleotide into the vascular system. The injection can be performed under direct observation following an incision and visualization of the tissues blood vessels. Alternatively, a catheter can be inserted at a distant site and threaded so that it resides in the vascular system that connects with the target tissue. In another embodiment, the injection could be performed by using a needle that traverses the intact skin and enters a vessel that supplies or drains from the target tissue.

In a preferred embodiment, the liver and portal vein of mice (25 g, 6-week old ICR mice) are visualized through a ventral midline incision. Anesthesia was obtained from intramuscular injections of 1000 .mu.g of ketamine-HCl (Parke-Davis, Morris Plains, N.J.) in 1 ml of normal saline and methoxyflurane (Pitman-Moore, Mudelein, Ill. USA) which was administered by inhalation as needed. Plasmid DNA in 1 ml of various solutions containing heparin to prevent clotting was injected into the portal vein using a needle over approximately 30 sec. At various times after the injection, the animals were sacrificed by cervical dislocation and the livers (average weight of 1.5 g) were divided into six sections composed of two pieces of median lobe, two pieces of left lateral lobe, the right lateral lobe, and the caudal lobe plus a small piece of right lateral lobe. Each of the six sections were placed separately into an homogenizing buffer. The homogenates were centrifuged and the supernatant analyzed for the foreign gene product. If the gene product is secreted then blood is obtained from the retro-orbital venous sinus and the level of the secreted protein is assayed in the blood. For example, the expression of the human growth hormone gene can be detected by measuring the amount of human growth hormone in the mouse serum using a radioimmune assay (RIA) (HGH-TGES 100T kit from Nichols Institute, San Juan Capistrano, Calif., USA). Alternatively, the foreign gene could produce an enzyme that corrects an abnormality in the disease state. For example, the phenylalanine hydroxylase gene could be used to normalize the elevated phenylalanine blood levels in a genetic mouse model of phenylketonuria.

In the liver, the hepatic vein is an efferent blood vessel since it normally carries blood away from the liver into the inferior vena cava. Also in the liver, the portal vein and hepatic arteries are afferent blood vessels in relation to the liver since they normally carry blood towards the liver. In a preferred embodiment, plasmid DNA may be efficiently expressed if delivered by a retrograde route into the efferent vessel of the liver (i.e. the hepatic vein). As demonstrated in the examples that follow, injections were directed into the inferior cava which was clamped in two locations; proximal and distal to the entry of the hepatic vein into the inferior vena cava. Specifically, the downstream inferior vena cava clamp was placed between the diaphragm and the entry point of the hepatic vein. The upstream inferior vena cava clamp was placed just upstream of the entry point of the renal veins. Since the veins of other organs such as the renal veins enter the inferior vena cava at this location, not all of the injection fluid went into the liver. In some of the animals that received retrograde injections in the inferior vena cava, the hepatic artery, mesenteric artery, and portal vein were clamped (occluded).

C. Permeability

The efficiency of the polynucleotide delivery and expression was increased substantially by increasing the permeability of a blood vessel within the target tissue. Permeability is defined here as the propensity for macromolecules such as polynucleotides to move through vessel walls and enter the extravascular space. One measure of permeability is the rate at which macromolecules move through the vessel wall and out of the vessel. Another measure of permeability is the lack of force that resists the movement through the vessel wall and out of the vessel. Vessels contain elements that prevent macromolecules from leaving the intravascular space (internal cavity of the vessel). These elements include endothelial cells and connective material (e.g. collagen). Increased permeability indicates that there are fewer of these elements that can block the egress of macromolecules and that the spaces between these elements are larger and more numerous. In this context, increased permeability enables a high percentage of polynucleotides being delivered to leave the intravascular space; while low permeability indicates that a low percentage of the polynucleotides will leave the intravascular space.

The permeability of a blood vessel can be increased by increasing the intravascular hydrostatic pressure. In a preferred embodiment, the intravascular hydrostatic pressure is increased by rapidly (from 10 seconds to 30 minutes) injecting a polynucleotide in solution into the blood vessel which increases the hydrostatic pressure. In another preferred embodiment, hydrostatic pressure is increased by obstructing the outflow of the injection solution from the tissue for a period of time sufficient to allow delivery of a polynucleotide. Obstructing means to block or impede the outflow of injection fluid, thereby transiently (reversibly) blocking the outflow of the blood. Furthermore, rapid injection may be combined with obstructing the outflow in yet another preferred embodiment. For example, an afferent vessel supplying an organ is rapidly injected and the efferent vessel draining the tissue is ligated transiently. The efferent vessel (also called the venous outflow or tract) draining outflow from the tissue is also partially or totally clamped for a period of time sufficient to allow delivery of a polynucleotide. In the reverse, an efferent is injected and an afferent vessel is occluded.

In another preferred embodiment, the intravascular pressure of a blood vessel is increased by increasing the osmotic pressure within the blood vessel. Typically, hypertonic solutions containing salts such as NaCl, sugars or polyols such as mannitol are used. Hypertonic means that the osmolality of the injection solution is greater than physiologic osmolality. Isotonic means that the osmolality of the injection solution is the same as the physiological osmolality (the tonicity or osmotic pressure of the solution is similar to that of blood). Hypertonic solutions have increased tonicity and osmotic pressure similar to the osmotic pressure of blood and cause cells to shrink.

The permeability of the blood vessel can also be increased by a biologically-active molecule in another preferred embodiment. A biologically-active molecule is a protein or a simple chemical such as histamine that increases the permeability of the vessel by causing a change in function, activity, or shape of cells within the vessel wall such as the endothelial or smooth muscle cells. Typically, biologically-active molecules interact with a specific receptor or enzyme or protein within the vascular cell to change the vessel's permeability. Biologically-active molecules include vascular permeability factor (VPF) which is also known as vascular endothelial growth factor (VEGF). Another type of biologically-active molecule can also increase permeability by changing the extracellular connective material. For example, an enzyme could digest the extracellular material and increase the number and size of the holes of the connective material.
 

Claim 1 of 17 Claims

1. A process for delivering a polynucleotide to a liver cell in a mammal, comprising: a) forming an occlusion in a hepatic vessel in said mammal; and, b) injecting the polynucleotide in a solution into the lumen of said hepatic vessel.

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