A study conducted by researchers at Massachusetts General Hospital found that one dose of anti-Mullerian hormone (AMH) gene therapy can cause long-term contraception in felines, potentially providing a safe and effective alternative to surgical spaying. The study was published in Nature Communications.
“AMH is a naturally occurring non-steroidal hormone produced by the ovaries in human females and other mammals and in the testes in males,” said Dr. Patricia K. Donahue, the study’s co-author and director of the Pediatric Surgical Research Laboratories and chief emerita of pediatric surgical services at Massachusetts General Hospital.
The work was conducted in collaboration with the Center for Conservation and Research of Endangered Wildlife at the Cincinnati Zoo and Botanical Garden and the Horae Gene Therapy Center at the University of Massachusetts Medical School.
The researchers investigated AMH’s efficacy in protecting the ovarian reserve in women undergoing chemotherapy. They discovered that when the AMH level was increased above a certain threshold, ovarian follicle growth was suppressed, inhibiting ovulation and conception. Using that knowledge, the team created an adeno-associated viral (AAV) gene therapy vector with a slightly altered version of the feline AMH gene to raise AMH levels in six female cats at two different doses.
“A single injection of gene therapy vector causes the cat’s muscles to produce AMH, which is normally only produced in the ovaries, and raises the overall level of AMH about 100 times higher than normal,” said senior author Dr. David Pepin, associate director of the Pediatric Surgical Research Laboratories.
The researchers followed the six treated cats and three control cats for more than two years.
The cats were exposed to a male for two four-month-long mating trials. The three control cats produced kittens, but the six treated cats did not become pregnant. In addition, the six treated cats exhibited no adverse effects, demonstrating that the treatment was safe and well tolerated at the doses tested, the researchers said.
“The treatment maintained high AMH levels for over two years, and we’re confident that those contraceptive levels will be sustained in the animals for much longer,” said Dr. Phillippe Godin, a study co-author.
Additional studies of larger cat numbers are needed to confirm the promising findings, Dr. Godin said. The gene therapy has the potential to fight pet overpopulation and prevent the euthanasia of healthy cats, the researchers stated.
Dr. Pepin acknowledged a lack of resources to produce enough doses to administer gene therapy to millions of cats.
“Our goal is to show that safe and effective permanent contraception in companion animals can be achieved using gene therapy,” Dr. Pepin said. “We hope that as the manufacturing capability of producing viral vectors increases with the rise of gene therapy in humans, delivering this contraceptive in the field to control unowned outdoor cat populations will become feasible.”
Research funding was provided by the Michelson Prize and Grants, the Joanie Bernard Foundation, and the Massachusetts General Hospital surgery department.