Penn Medicine researchers have developed a new targeted approach to prevent a toxicity seen in the sensory neurons of dorsal root ganglia after gene therapy to treat neurological disorders. It's an important hurdle to clear, as the field works toward more safe and effective gene therapies for patients with disorders like spinal muscular atrophy.
"We believe that this new approach could improve safety in gene therapy universally," said first author Juliette Hordeaux, DVM, PhD, senior director of Translational Research in Penn's Gene Therapy Program.
The findings were reported online this week in theScience Translational Medicine.
The toxicity has not been reported in humans, but studies in nonhuman primates using adeno-associated viral (AAV) vectors to deliver corrected genes via the spinal cord fluid and intravenously have revealed problems of axonal degeneration in some tracts of the spinal cord and peripheral nerves. The cause was traced back to the dorsal root ganglion, or DRG, a cluster of neural cells on the outside of the spinal cord responsible for transmission of sensory messages.
This toxicity stems from the overexpression of an introduced gene, known as a transgene, in cells in the DRG, researchers from Penn's Gene Therapy Program found in the study. To correct that, they modified a transgene with a microRNA target designed to reduce the level of the transgene expression in the DRG. That alteration eliminated more than 80 percent of the transgene expression and reduced the toxicity in primates, the researchers report.
"We believe it is a safe, straightforward way to ameliorate the safety of AAV therapy for the central nervous system," said first author Juliette Hordeaux, DVM, PhD, senior director of Translational Research in Penn's Gene Therapy Program. "This approach could be used to design other gene therapy vectors to repress transgene expression in the cell types that are affected by the toxicity and not others, which is critical, because you need the expression everywhere else to effectively treat the disorder."
Gene transfer expert James M. Wilson, MD, PhD, director of the Gene Therapy Program, and professor of Medicine and Pediatrics in Penn's Perelman School of Medicine, served as the senior author of the paper.
After Penn researchers documented DRG toxicity in nonhuman primates, they began devising a way to overcome it. Though its asymptomatic in primates, the damage became clear under close study of histopathology in the CNS. Damage to the DRG in humans, researchers know, can lead to the breakdown of axons responsible for delivering impulses from nerves to the brain. Numbness and weakness in limbs, among other side effects, follow suit.
The observed toxicity in past animal studies was enough for the U.S. Food and Drug Administration to recently place a partial hold on human trials administering a gene therapy vector into the spinal cord to treat spinal muscular atrophy, the genetic disease that severely weakens muscles and causes problems with movement. In the new study, the researchers injected vectors with and without an microRNA target, first in mice and then primates. microRNA regulates gene expression and makes for an ideal target in the cells. microRNA-183 was chosen specifically because it is largely restricted to the neurons in the DRG.
Administering unmodified AAV vectors resulted in robust delivery of the new gene into target tissue and toxicity in DRG neurons. Vectors with the miRNA target, on the other hand, reduced transgene expression significantly, as well as the toxicity of DRG neurons, without affecting transduction elsewhere in the primate's brain, histological analyses of the specimens up to 90 days later showed. An immune response was first believed to be causing the toxicity; however, the researchers debunked that hypothesis through experiments that showed how immunosuppressants and steroids were unsuccessful at alleviating the toxicity.
According to the authors, toxicity of DRGs is likely to occur in any gene therapy that relies on high doses of a vector or direct delivery of a vector into the spinal cord fluid. This latest study paves a path forward to prevent that damage.
"We were concerned about the DRG pathology that was observed in most of our NHP studies," Wilson said. "This modified vector shows great promise to reduce DRG toxicity and should facilitate the development of safer AAV-based gene therapies for many CNS diseases."
Reference: Hordeaux J, Buza EL, Jeffrey B, et al. MicroRNA-mediated inhibition of transgene expression reduces dorsal root ganglion toxicity by AAV vectors in primates. Science Translational Medicine. 2020;12(569). doi:10.1126/scitranslmed.aba9188
This article has been republished from the following materials. Note: material may have been edited for length and content. For further information, please contact the cited source.
See original here:
New Approach Reduces the Toxicity of Brain-Targeted Gene Therapy - Technology Networks
- Faulty Circuits (preview) [Last Updated On: April 7th, 2010] [Originally Added On: April 7th, 2010]
- Faulty Circuits (preview) [Last Updated On: April 7th, 2010] [Originally Added On: April 7th, 2010]
- Rare flowers and common herbal supplements get unmasked with plant DNA barcoding [Last Updated On: April 20th, 2010] [Originally Added On: April 20th, 2010]
- Rare flowers and common herbal supplements get unmasked with plant DNA barcoding [Last Updated On: April 20th, 2010] [Originally Added On: April 20th, 2010]
- Biomarker Studies Could Realize Goal of More Effective and Personalized Cancer Medicine [Last Updated On: April 27th, 2010] [Originally Added On: April 27th, 2010]
- Biomarker Studies Could Realize Goal of More Effective and Personalized Cancer Medicine [Last Updated On: April 27th, 2010] [Originally Added On: April 27th, 2010]
- Schizophrenia shares genetic links with autism, genome study shows [Last Updated On: May 12th, 2010] [Originally Added On: May 12th, 2010]
- Schizophrenia shares genetic links with autism, genome study shows [Last Updated On: May 12th, 2010] [Originally Added On: May 12th, 2010]
- Alzheimer's: Forestalling the Darkness with New Approaches (preview) [Last Updated On: May 28th, 2010] [Originally Added On: May 28th, 2010]
- Alzheimer's: Forestalling the Darkness with New Approaches (preview) [Last Updated On: May 28th, 2010] [Originally Added On: May 28th, 2010]
- Large-Scale Autism Study Reveals Disorder's Genetic Complexity [Last Updated On: June 12th, 2010] [Originally Added On: June 12th, 2010]
- Large-Scale Autism Study Reveals Disorder's Genetic Complexity [Last Updated On: June 12th, 2010] [Originally Added On: June 12th, 2010]
- Cancer Therapy Goes Viral: Progress Is Made Tackling Tumors with Viruses [Last Updated On: June 24th, 2010] [Originally Added On: June 24th, 2010]
- Cancer Therapy Goes Viral: Progress Is Made Tackling Tumors with Viruses [Last Updated On: June 24th, 2010] [Originally Added On: June 24th, 2010]
- Vaccines Derived from Patients' Tumor Cells Are Individualizing Cancer Treatment [Last Updated On: June 26th, 2010] [Originally Added On: June 26th, 2010]
- Vaccines Derived from Patients' Tumor Cells Are Individualizing Cancer Treatment [Last Updated On: June 26th, 2010] [Originally Added On: June 26th, 2010]
- A genome story: 10th anniversary commentary by Francis Collins [Last Updated On: June 29th, 2010] [Originally Added On: June 29th, 2010]
- A genome story: 10th anniversary commentary by Francis Collins [Last Updated On: June 29th, 2010] [Originally Added On: June 29th, 2010]
- Hair Trigger: How a Cell's Primary Cilium Functions as a Molecular Antenna [Last Updated On: June 30th, 2010] [Originally Added On: June 30th, 2010]
- Hair Trigger: How a Cell's Primary Cilium Functions as a Molecular Antenna [Last Updated On: June 30th, 2010] [Originally Added On: June 30th, 2010]
- DNA Drugs Come of Age (preview) [Last Updated On: July 16th, 2010] [Originally Added On: July 16th, 2010]
- DNA Drugs Come of Age (preview) [Last Updated On: July 16th, 2010] [Originally Added On: July 16th, 2010]
- 2 Genes Linked to Embryonic Brain Impairment in Down's Syndrome [Last Updated On: July 22nd, 2010] [Originally Added On: July 22nd, 2010]
- 2 Genes Linked to Embryonic Brain Impairment in Down's Syndrome [Last Updated On: July 22nd, 2010] [Originally Added On: July 22nd, 2010]
- Stem Cells from Reprogrammed Adult Cells Found to Bring Along Genetic Defects of Their Donors [Last Updated On: October 11th, 2010] [Originally Added On: October 11th, 2010]
- Was Darwin a Punk? A Q&A with Punker-Paleontologist Greg Graffin [Last Updated On: October 11th, 2010] [Originally Added On: October 11th, 2010]
- Parkinsonian Power Failure: Neuron Degeneration May Be Caused by a Cellular Energy System Breakdown [Last Updated On: October 11th, 2010] [Originally Added On: October 11th, 2010]
- Was Darwin a Punk? A Q&A with Punker-Paleontologist Greg Graffin [Last Updated On: October 11th, 2010] [Originally Added On: October 11th, 2010]
- Desperation Drives Parents to Dubious Autism Treatments (preview) [Last Updated On: October 13th, 2010] [Originally Added On: October 13th, 2010]
- Revolution Postponed: Why the Human Genome Project Has Been Disappointing (preview) [Last Updated On: October 26th, 2010] [Originally Added On: October 26th, 2010]
- Controlling the Brain with Light (preview) [Last Updated On: October 26th, 2010] [Originally Added On: October 26th, 2010]
- Optogenetics: Controlling the Brain with Light [Extended Version] [Last Updated On: October 26th, 2010] [Originally Added On: October 26th, 2010]
- Clear New Insights into the Genetics of Depression [Last Updated On: November 7th, 2010] [Originally Added On: November 7th, 2010]
- TEDMED 2010: Technology and the people [Last Updated On: November 7th, 2010] [Originally Added On: November 7th, 2010]
- Bacteria, the anti-cancer soldier [Last Updated On: November 7th, 2010] [Originally Added On: November 7th, 2010]
- Clear New Insights into the Genetics of Depression [Last Updated On: November 7th, 2010] [Originally Added On: November 7th, 2010]
- TEDMED 2010: Technology and the people [Last Updated On: November 7th, 2010] [Originally Added On: November 7th, 2010]
- Bacteria, the anti-cancer soldier [Last Updated On: November 7th, 2010] [Originally Added On: November 7th, 2010]
- Scientific regress: When science goes backward [Last Updated On: November 29th, 2010] [Originally Added On: November 29th, 2010]
- Can You Live Forever? Maybe Not--But You Can Have Fun Trying [Last Updated On: December 26th, 2010] [Originally Added On: December 26th, 2010]
- How to Fix the Obesity Crisis (preview) [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- Personalizing cancer medicine [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- New Salmonella strain delivers gene-based therapy to fight virus in mice [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- How to Fix the Obesity Crisis (preview) [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- Personalizing cancer medicine [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- New Salmonella strain delivers gene-based therapy to fight virus in mice [Last Updated On: February 14th, 2011] [Originally Added On: February 14th, 2011]
- Steps toward a Bionic Eye [Last Updated On: February 20th, 2011] [Originally Added On: February 20th, 2011]
- Steps toward a Bionic Eye [Last Updated On: February 20th, 2011] [Originally Added On: February 20th, 2011]
- Giving HIV a Poor Reception: New AIDS Treatment Tinkers with Immune Cell Genes [Last Updated On: March 6th, 2011] [Originally Added On: March 6th, 2011]
- Giving HIV a Poor Reception: New AIDS Treatment Tinkers with Immune Cell Genes [Last Updated On: March 6th, 2011] [Originally Added On: March 6th, 2011]
- Smaller, cheaper, faster: Does Moore's law apply to solar cells? [Last Updated On: March 27th, 2011] [Originally Added On: March 27th, 2011]
- Smaller, cheaper, faster: Does Moore's law apply to solar cells? [Last Updated On: March 27th, 2011] [Originally Added On: March 27th, 2011]
- New Drugs for Hepatitis C on the Horizon [Last Updated On: April 10th, 2011] [Originally Added On: April 10th, 2011]
- Can we capture all of the world's carbon emissions? [Last Updated On: April 10th, 2011] [Originally Added On: April 10th, 2011]
- New Drugs for Hepatitis C on the Horizon [Last Updated On: April 10th, 2011] [Originally Added On: April 10th, 2011]
- Can we capture all of the world's carbon emissions? [Last Updated On: April 10th, 2011] [Originally Added On: April 10th, 2011]
- Drug-resistant genes found in cholera and dysentery strains in New Delhi water supply [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Fast Track to Vaccines: How Systems Biology Speeds Drug Development (preview) [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Drug-resistant genes found in cholera and dysentery strains in New Delhi water supply [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Fast Track to Vaccines: How Systems Biology Speeds Drug Development (preview) [Last Updated On: May 1st, 2011] [Originally Added On: May 1st, 2011]
- Autism's Tangled Genetics Full of Rare and Varied Mutations [Last Updated On: June 19th, 2011] [Originally Added On: June 19th, 2011]
- A New Look at Obsessive-Compulsive Disorder (preview) [Last Updated On: June 19th, 2011] [Originally Added On: June 19th, 2011]
- Autism's Tangled Genetics Full of Rare and Varied Mutations [Last Updated On: June 19th, 2011] [Originally Added On: June 19th, 2011]
- A New Look at Obsessive-Compulsive Disorder (preview) [Last Updated On: June 19th, 2011] [Originally Added On: June 19th, 2011]
- Close Encounters of Science and Medicine [Last Updated On: July 3rd, 2011] [Originally Added On: July 3rd, 2011]
- Close Encounters of Science and Medicine [Last Updated On: July 3rd, 2011] [Originally Added On: July 3rd, 2011]
- New Report Details Uphill Battle to Solve the U.S.'s Pain Problem [Last Updated On: July 24th, 2011] [Originally Added On: July 24th, 2011]
- New Report Details Uphill Battle to Solve the U.S.'s Pain Problem [Last Updated On: July 24th, 2011] [Originally Added On: July 24th, 2011]
- A Breath of Fresh Air: New Hope for Cystic Fibrosis Treatment (preview) [Last Updated On: August 7th, 2011] [Originally Added On: August 7th, 2011]
- A Breath of Fresh Air: New Hope for Cystic Fibrosis Treatment (preview) [Last Updated On: August 7th, 2011] [Originally Added On: August 7th, 2011]
- Sickle Cell Anemia: Stem Cell Gene Therapy - Donald Kohn [Last Updated On: August 18th, 2011] [Originally Added On: August 18th, 2011]
- Sickle Cell Anemia: Stem Cell Gene Therapy - A Patient's Perspective [Last Updated On: October 8th, 2011] [Originally Added On: October 8th, 2011]
- Gene therapy improves stem cell transplantation - Video [Last Updated On: October 14th, 2011] [Originally Added On: October 14th, 2011]
- THE NEW MORGELLONS HAIR - Video [Last Updated On: October 14th, 2011] [Originally Added On: October 14th, 2011]
- Studying Mental Illness in a Dish [Last Updated On: November 13th, 2011] [Originally Added On: November 13th, 2011]
- The Puzzle of Pancreatic Cancer: How Steve Jobs Did Not Beat the Oddsbut Nobel Winner Ralph Steinman Did [Last Updated On: November 13th, 2011] [Originally Added On: November 13th, 2011]
- Did Alternative Medicine Extend or Abbreviate Steve Jobs's Life? [Last Updated On: November 13th, 2011] [Originally Added On: November 13th, 2011]
- Calendar: MIND Events in November and December [Last Updated On: November 13th, 2011] [Originally Added On: November 13th, 2011]
- Studying Mental Illness in a Dish [Last Updated On: November 13th, 2011] [Originally Added On: November 13th, 2011]
- The Puzzle of Pancreatic Cancer: How Steve Jobs Did Not Beat the Odds?but Nobel Winner Ralph Steinman Did [Last Updated On: November 13th, 2011] [Originally Added On: November 13th, 2011]