Posts tagged gene therapy

A new treatment for drug-resistant epilepsy with the potential to suppress seizures ‘on demand’ with a pill, similar to how you might take painkillers when you feel a headache coming on, has been developed by UCL researchers funded by the Wellcome Trust.

The treatment, described in Nature Communications, combines genetic and chemical approaches to suppress seizures without disrupting normal brain function. The technique was demonstrated in rodents but in future we could see people controlling seizures on-demand with a simple pill.

Epilepsy affects around 50 million people worldwide including 600,000 in the UK and around a quarter of cases are resistant to conventional treatments. Many of these cases could be addressed by the new treatment method, which relies on genetic modification of brain cells to make them sensitive to a normally inactive compound.

“First, we inject a modified virus into the area of the brain where seizures arise,” explains Professor Dimitri Kullmann of the UCL Institute of Neurology, senior author of the research. “This virus instructs the brain cells to make a protein that is activated by CNO (clozapine-N-oxide), a compound that can be taken as a pill. The activated protein then suppresses the over-excitable brain cells that trigger seizures, but only in the presence of CNO.

“At the moment, severe seizures are treated with drugs that suppress the excitability of all brain cells, and patients therefore experience side effects. Sometimes the dose required to stop seizures is so high that patients need to be sedated and taken to intensive care. If we can take our new method into the clinic, which we hope to do within the next decade, we could treat patients who are susceptible to severe seizures with a one-off injection of the modified virus, and then use CNO only when needed.

“CNO would be given as a pill in the event that patients could predict when seizures were likely to occur. For example, many people with treatment-resistant epilepsy experience clusters of seizures, where severe seizures are preceded by smaller ones. Seizure risk is also high when people are ill, sleep deprived, or at certain times of the menstrual cycle, so these would all be good times to take the pill as a preventative measure. In urgent situations, the compound could be given as an injection. We could even consider a fully automatic delivery system, where CNO was given by a pump, as is done for insulin in some people with diabetes.”

As CNO has a half-life of about a few hours and only affects the pre-treated epileptic parts of the brain, the new method avoids the need to permanently alter the brain or treat the whole brain with seizure-suppressing drugs. It builds on similar work by Professor Kullmann’s group using gene therapy to ‘calm down’ brain cells, or using light pulses to activate seizure-suppressing receptors in the brain. The new technique works in a similar way but is reversible and avoids the need for invasive devices to deliver light to the brain.

“After the one-off injection into affected areas of the brain, our new technique would require nothing beyond CNO, administered as an injection or a pill, to suppress seizures when required,” says Professor Kullmann. “This makes it more attractive than alternative forms of targeted therapy such as surgery to remove the brain region where seizures arise, or gene therapy that permanently alters the excitability of brain cells.

“Although there is currently no evidence that permanently suppressing excitability in a small area affects brain function, we cannot be sure that it would have no impact long-term. Our new method is completely reversible, so if there were any side-effects then people could simply stop taking the CNO pill.”

(Source: ucl.ac.uk)

TAU researcher uses DNA therapy in lab mice to improve cochlear implant functionality

One in a thousand children in the United States is deaf, and one in three adults will experience significant hearing loss after the age of 65. Whether the result of genetic or environmental factors, hearing loss costs billions of dollars in healthcare expenses every year, making the search for a cure critical.

Now a team of researchers led by Karen B. Avraham of the Department of Human Molecular Genetics and Biochemistry at Tel Aviv University’s Sackler Faculty of Medicine and Yehoash Raphael of the Department of Otolaryngology–Head and Neck Surgery at University of Michigan’s Kresge Hearing Research Institute have discovered that using DNA as a drug — commonly called gene therapy — in laboratory mice may protect the inner ear nerve cells of humans suffering from certain types of progressive hearing loss.

In the study, doctoral student Shaked Shivatzki created a mouse population possessing the gene that produces the most prevalent form of hearing loss in humans: the mutated connexin 26 gene. Some 30 percent of American children born deaf have this form of the gene. Because of its prevalence and the inexpensive tests available to identify it, there is a great desire to find a cure or therapy to treat it.

"Regenerating" neurons

Prof. Avraham’s team set out to prove that gene therapy could be used to preserve the inner ear nerve cells of the mice. Mice with the mutated connexin 26 gene exhibit deterioration of the nerve cells that send a sound signal to the brain. The researchers found that a protein growth factor used to protect and maintain neurons, otherwise known as brain-derived neurotrophic factor (BDNF), could be used to block this degeneration. They then engineered a virus that could be tolerated by the body without causing disease, and inserted the growth factor into the virus. Finally, they surgically injected the virus into the ears of the mice. This factor was able to “rescue” the neurons in the inner ear by blocking their degeneration.

"A wide spectrum of people are affected by hearing loss, and the way each person deals with it is highly variable," said Prof. Avraham. "That said, there is an almost unanimous interest in finding the genes responsible for hearing loss. We tried to figure out why the mouse was losing cells that enable it to hear. Why did it lose its hearing? The collaborative work allowed us to provide gene therapy to reverse the loss of nerve cells in the ears of these deaf mice."

Although this approach is short of improving hearing in these mice, it has important implications for the enhancement of sound perception with a cochlear implant, used by many people whose connexin 26 mutation has led to impaired hearing.

Embryonic hearing?

Inner ear nerve cells facilitate the optimal functioning of cochlear implants. Prof. Avraham’s research suggests a possible new strategy for improving implant function, particularly in people whose hearing loss gets progressively worse with time, such as those with profound hearing loss as well as those with the connexin gene mutation. Combining gene therapy with the implant could help to protect vital nerve cells, thus preserving and improving the performance of the implant.

More research remains. “Safety is the main question. And what about timing? Although over 80 percent of human and mouse genes are similar, which makes mice the perfect lab model for human hearing, there’s still a big difference. Humans start hearing as embryos, but mice don’t start to hear until two weeks after birth. So we wondered, do we need to start the corrective process in utero, in infants, or later in life?” said Prof. Avraham.

"Practically speaking, we are a long way off from treating hearing loss during embryogenesis. But we proved what we set out to do: that we can help preserve nerve cells in the inner ears of the mouse," Prof. Avraham continued. "This already looks very promising."

(Source: aftau.org)

The concept behind gene therapy is simple: deliver a healthy gene to compensate for one that is mutated. New research published today in the Journal of Neuroscience suggests this approach may eventually be a feasible option to treat Rett Syndrome, the most disabling of the autism spectrum disorders. Gail Mandel, Ph.D., a Howard Hughes Investigator at Oregon Health and Sciences University, led the study. The Rett Syndrome Research Trust, with generous support from the Rett Syndrome Research Trust UK and Rett Syndrome Research & Treatment Foundation, funded this work through the MECP2 Consortium.

In 2007, co-author Adrian Bird, Ph.D., at the University of Edinburgh astonished the scientific community with proof-of-concept that Rett is curable, by reversing symptoms in adult mice. His unexpected results catalyzed labs around the world to pursue a multitude of strategies to extend the pre-clinical findings to people.

Today’s study is the first to show reversal of symptoms in fully symptomatic mice using techniques of gene therapy that have potential for clinical application.

Rett Syndrome is an X-linked neurological disorder primarily affecting girls; in the US, about 1 in 10,000 children a year are born with Rett.  In most cases symptoms begin to manifest between 6 and 18 months of age, as developmental milestones are missed or lost. The regression that follows is characterized by loss of speech, mobility, and functional hand use, which is often replaced by Rett’s signature gesture: hand-wringing, sometimes so intense that it is a constant during every waking hour. Other symptoms include seizures, tremors, orthopedic and digestive problems, disordered breathing and other autonomic impairments, sensory issues and anxiety. Most children live into adulthood and require round-the-clock care.

The cause of Rett Syndrome’s terrible constellation of symptoms lies in mutations of an X-linked gene called MECP2 (methyl CpG-binding protein). MECP2 is a master gene that regulates the activity of many other genes, switching them on or off.

“Gene therapy is well suited for this disorder,” Dr. Mandel explains. “Because MECP2 binds to DNA throughout the genome, there is no single gene currently that we can point to and target with a drug. Therefore the best chance of having a major impact on the disorder is to correct the underlying defect in as many cells throughout the body as possible. Gene therapy allows us to do that.”

Healthy genes can be delivered into cells aboard a virus, which acts as a Trojan horse. Many different types of these Trojan horses exist. Dr. Mandel used adeno-associated virus serotype 9 (AAV9), which has the unusual and attractive ability to cross the blood-brain barrier. This allows the virus and its cargo to be administered intravenously, instead of employing more invasive direct brain delivery systems that require drilling burr holes into the skull.

Because the virus has limited cargo space, it cannot carry the entire MECP2 gene. Co-author Brian Kaspar of Nationwide Children’s Hospital collaborated with the Mandel lab to package only the gene’s most critical segments. After being injected into the Rett mice, the virus made its way to cells throughout the body and brain, distributing the modified gene, which then started to produce the MeCP2 protein.

As in human females with Rett Syndrome, only approximately 50% of the mouse cells have a healthy copy of MECP2. After the gene therapy treatment 65% of cells now had a functioning MECP2 gene.

The treated mice showed profound improvements in motor function, tremors, seizures and hind limb clasping. At the cellular level the smaller body size of neurons seen in mutant cells was restored to normal. Biochemical experiments proved that the gene had found its way into the nuclei of cells and was functioning as expected, binding to DNA.

One Rett symptom that was not ameliorated was abnormal respiration. Researchers hypothesize that correcting this may require targeting a greater number of cells than the 15% that had been achieved in the brainstem.

“We learned a critical and encouraging point with these experiments – that we don’t have to correct every cell in order to reverse symptoms. Going from 50% to 65% of the cells having a functioning gene resulted in significant improvements,” said co-author Saurabh Garg.

One of the potential challenges of gene therapy in Rett is the possibility of delivering multiple copies of the gene to a cell. We know from the MECP2 Duplication Syndrome that too much of this protein is detrimental. “Our results show that after gene therapy treatment the correct amount of MeCP2 protein was being expressed. At least in our hands, with these methods, overexpression of MeCP2 was not an issue,” said co-author Daniel Lioy.

Dr. Mandel cautioned that key steps remain before clinical trials can begin. “Our study is an important first step in highlighting the potential for AAV9 to treating the neurological symptoms in Rett. We are now working on improving the packaging of MeCP2 in the virus to see if we can target a larger percentage of cells and therefore improve symptoms even further,” said Mandel. Collaborators Hélène Cheval and Adrian Bird see this as a promising follow up to the 2007 work showing symptom reversal in Rett mice. “That study used genetic tricks that could not be directly applicable to humans, but the AAV9 vector used here could in principle deliver a gene therapeutically. This is an important step forward, but there is a way to go yet.”

“Gene therapy has had a tumultuous road in the past few decades but is undergoing a renaissance due to recent technological advances. Europe and Asia have gene therapy treatments already in the clinic and it’s likely that the US will follow suit. Our goal now is to prioritize the next key experiments and facilitate their execution as quickly as possible. Gene therapy, especially to the brain, is a tricky undertaking but I’m cautiously optimistic that with the right team we can lay out a plan for clinical development. I congratulate the Mandel and Bird labs on today’s publication, which is the third to be generated from the MECP2 Consortium in a short period of time,” said Monica Coenraads, Executive Director of the Rett Syndrome Research Trust and mother of a teenaged daughter with the disorder.

(Source: rsrt.org)

Borrowing a trick from nature, researchers have switched off the extra chromosome that causes Down syndrome in cells taken from patients with the condition.

Though not a cure, the technique, reported July 17 in Nature, has already produced insights into the disorder. In the long run it might even make the flaw that causes Down syndrome correctable through gene therapy.

“Gene therapy is now on the horizon,” says Elizabeth Fisher, a molecular geneticist at University College London. “But that horizon is very far away.”

Down syndrome, also called trisomy 21, occurs when people inherit three copies of chromosome 21 instead of the usual two. It is the most common chromosomal condition, affecting around one in every 700 babies born in the United States. People with the disorder typically have both physical and cognitive complications of having an extra chromosome.

“Down syndrome has been one of those disorders where people say, ‘Oh, there’s nothing you can do about it,’ ” says Jeanne Lawrence, a chromosome biologist and genetic counselor at the University of Massachusetts Medical School in Worcester, who led the study with colleagues Lisa Hall and Jun Jiang.

The researchers decided to see whether they could shut down the extra chromosome by drawing on a biological process called X inactivation. Women have two X chromosomes and men have only one X and a Y. To halve the amount of X chromosome products, female cells shut down one copy. Cells do that using a chunk of RNA called XIST, which is made by one X chromosome but not the other. The RNA works by pulling in proteins that essentially board up the chromosome like an abandoned building. The other X stays on by making a different RNA.

Lawrence and Hall thought that if they put XIST on another chromosome, it might shut that one down too. So Jiang put the gene for XIST onto one of the three copies of chromosome 21 carried by stem cells grown from a man with Down syndrome. That copy of the chromosome got switched off.

“It’s kind of surprising that it wasn’t done before. I’m smacking my own forehead and saying, ‘duh,’ ” says Roger Reeves, a geneticist at Johns Hopkins University.

One idea about why an extra chromosome 21 causes cognitive problems is that it may slow down the growth of brain cells. Jiang grew nerve cells from the Down patient’s stem cells to see how cells with one shut-down chromosome developed compared with cells bearing three active copies. The cells with only two working chromosomes grew faster, forming clusters of neurons in a day or two, while the uncorrected cells needed four or five days.

The work is an enormous step forward in Down syndrome research, Fisher says, and “may take us much closer to understanding the molecular basis of the disorder.” The technique could allow researchers to figure out which genes are involved in Down syndrome and how extra copies affect cells and ultimately the body, she says.

Reeves wants to use the technology in animal experiments, a critical step in determining whether it could find use as gene therapy for people with Down syndrome. He plans to work with Lawrence’s group to switch off the extra chromosome in mice engineered to have a disorder that simulates some features of Down syndrome.

But Reeves doubts that scientists could use the method to switch off the extra chromosome in every cell in the body. Doing so would probably require gene therapy at a very early stage of pregnancy, something scientists don’t know how to do. “I just don’t see how we would get there from where we are today,” Reeves says.

Such universal silencing of the extra chromosome may be necessary to forestall developmental problems. But other problems associated with Down syndrome might be prevented or reversed by shutting down the extra chromosome after birth. For instance, people with Down syndrome are at high risk of developing childhood leukemia and of getting Alzheimer’s disease. Gene therapy to turn off the extra chromosome in the bone marrow or the brain might prevent those problems.

Therapeutic possibilities are still far in the future and may never pan out, says William Mobley, a neurologist and neuroscientist at the University of California, San Diego. “We have to move cautiously and deliberately and not say that a cure for Down syndrome is on the horizon,” he says. “It’s not true, but gosh is there excitement that progress is being made.”

(Source: sciencenews.org)

Researchers at Northeastern University in Boston have developed a gene therapy approach that may one day stop Parkinson’s disease (PD) in it tracks, preventing disease progression and reversing its symptoms. The novelty of the approach lies in the nasal route of administration and nanoparticles containing a gene capable of rescuing dying neurons in the brain. Parkinson’s is a devastating neurodegenerative disorder caused by the death of dopamine neurons in a key motor area of the brain, the substantia nigra (SN). Loss of these neurons leads to the characteristic tremor and slowed movements of PD, which get increasingly worse with time. Currently, more than 1% of the population over age 60 has PD and approximately 60,000 Americans are newly diagnosed every year. The available drugs on the market for PD mimic or replace the lost dopamine but do not get to the heart of the problem, which is the progressive loss of the dopamine neurons.

The focus of Dr. Barbara Waszczak’s lab at Northeastern University in Boston is to find a way to harvest the potential of glial cell line-derived neurotrophic factor (GDNF) as a treatment for PD. GDNF is a protein known to nourish dopamine neurons by activating survival and growth-promoting pathways inside the cells. Not surprisingly, GDNF is able to protect dopamine neurons from injury and restore the function of damaged and dying neurons in many animal models of PD. However, the action of GDNF is limited by its inability to cross the blood-brain barrier (BBB), thus requiring direct surgical injection into the brain. To circumvent this problem, Waszczak’s lab is investigating intranasal delivery as a way to bypass the BBB. Their previous work showed that intranasal delivery of GDNF protects dopamine neurons from damage by the neurotoxin, 6-hydroxydopamine (6-OHDA), a standard rat model of PD.

Taking this work a step further, Brendan Harmon, working in Waszczak’s lab, has adapted the intranasal approach so that cells in the brain can continuously produce GDNF. His work utilized nanoparticles, developed by Copernicus Therapeutics, Inc., which are able to transfect brain cells with an expression plasmid carrying the gene for GDNF (pGDNF). When given intranasally to rats, these pGDNF nanoparticles increase GDNF production throughout the brain for long periods, avoiding the need for frequent re-dosing. Now, in new research presented on April 20 at 12:30 pm during Experimental Biology 2013 in Boston, MA, Harmon reports that intranasal administration of Copernicus’ pGDNF nanoparticles results in GDNF expression sufficient to protect SN dopamine neurons in the 6-OHDA model of PD.

Waszczak and Harmon believe that intranasal delivery of Copernicus’ nanoparticles may provide an effective and non-invasive means of GDNF gene therapy for PD, and an avenue for transporting other gene therapy vectors to the brain. This work, which was funded in part by the Michael J. Fox Foundation for Parkinson’s Research and Northeastern University, has the potential to greatly expand treatment options for PD and many other central nervous system disorders.

(Source: eurekalert.org)