Scientists have restored the sense of smell in mice through gene therapy for the first time -- a hopeful sign for people who can't smell anything from birth or lose it due to disease.
The achievement in curing congenital anosmia -- the medical term for lifelong inability to detect odors -- may also aid research on other conditions that also stem from problems with the cilia. Those tiny hair-shaped structures on the surfaces of cells throughout the body are involved in many diseases, from the kidneys to the eyes.
The new findings, published online in Nature Medicine, come from a team at the University of Michigan Medical School and their colleagues at several other institutions.
The researchers caution that it will take time for their work to affect human treatment, and that it will be most important for people who have lost their sense of smell due to a genetic disorder, rather than those who lose it due to aging, head trauma, or chronic sinus problems. But their work paves the way for a better understanding of anosmia at the cellular level.
"Using gene therapy in a mouse model of cilia dysfunction, we were able to rescue and restore olfactory function, or sense of smell," says senior author Jeffrey Martens, Ph.D., an associate professor of pharmacology at U-M. "Essentially, we induced the neurons that transmit the sense of smell to regrow the cilia they'd lost."
The mice in the study all had a severe genetic defect that affected a protein called IFT88, causing a lack of cilia throughout their bodies. Such mice are prone to poor feeding and to early death as a result. In humans, the same genetic defect is fatal.
The researchers were able to insert normal IFT88 genes into the cells of the mice by giving them a common cold virus loaded with the normal DNA sequence, and allowing the virus to infect them and insert the DNA into the mouse's own cells. They then monitored cilia growth, feeding habits, and well as signals within and between the nerve cells, called neurons, that are involved in the sense of smell.
Only 14 days after the three-day treatment, the mice had a 60 percent increase in their body weight, an indication they were likely eating more. Cell-level indicators showed that neurons involved in smelling were firing correctly when the mice were exposed to amyl acetate, a strong-smelling chemical also called banana oil.
"At the molecular level, function that had been absent was restored," says Martens.
"By restoring the protein back into the olfactory neurons, we could give the cell the ability to regrow and extend cilia off the dendrite knob, which is what the olfactory neuron needs to detect odorants," says postdoctoral fellow and first author Jeremy McIntyre, Ph.D.
Martens notes that the research has importance for other ciliopathies, or diseases caused by cilia dysfunction. These include such conditions as polycystic kidney disease, retinitis pigmentosa in the eye, and rare inherited disorders such as Alström syndrome, Bardet-Biedl syndrome, primary ciliary dyskinesia and nephronopthisis.
Scientists believe that nearly every cell in the body has the capacity to grow one or more cilia. In the olfactory system, multiple cilia project from olfactory sensory neurons, sensory cells that are found in the olfactory epithelium, tissue high up in the nasal cavity. Receptors that bind odorants are localized on the cilia, which is why a loss of cilia results in a loss in the ability to smell.
Because the new findings show that gene therapy is a viable option for the functional rescue of cilia in established, already differentiated cells, researchers working on those conditions might be able to use gene therapy to attempt to restore cilia function as well.
Meanwhile, Martens and his team will continue to look for other cilia-related genetic causes of anosmia, including those that are not lethal in humans.
"We hope this stimulates the olfactory research community to look at anosmia caused by other factors, such as head trauma and degenerative diseases," he says. "We know a lot about how this system works – now have to look at how to fix it when it malfunctions." And, he notes because the neurons involved in the sense of smell connect to the nose, delivery of gene therapy treatments would not need to involve invasive procedures.
The study was funded by four parts of National Institutes of Health: the National Institute on Deafness and Other Communications Disorders, the National Institute on Diabetes and Digestive and Kidney Diseases, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Eye Institute.
In addition to Martens and McIntyre, the paper's authors include Ariell Joiner, Corey Williams, Paul Jenkins, Dyke McEwen, Lian Zhang and John Escobado from the Martens lab at U-M; Randall Reed from the Johns Hopkins University; Erica Davis, I-Chun Tsai and Nicholas Katsanis from Duke University; Aniko Sabo, Donna Muzny and Richard Gibbs from the Baylor College of Medcine; Eric Green and James Mullikin from the National Institutes of Health Intramural Sequencing Center; Bradley Yoder from the University of Alabama-Birmingham; Sophie Thomas and Tania Attié-Bitach from the Université Paris Descartes; Katarzyna Szymanska and Colin A Johnson from St. James's University Hospital in Leeds, UK; and Philip Beales from University College London, UK.
Reference: Nature Medicine, Advance Online Publication, DOI 10.1038/nm.2860
Grant numbers: R01DC009606, F32DC011990, R01DC004553, R01DC008295, R01DK75996, R01DK072301, R01DK075972, R01HD042601, and R01EY021872.
For more about the Martens lab at the U-M Medical School, visit http://www-personal.umich.edu/~martensj/Home.html
Kara Gavin | EurekAlert!
Further reports about: > Alström syndrome > Bardet-Biedl syndrome > Medical Wellness > Medicine > Nature Immunology > chronic sinus problems > ciliary dyskinesia > ciliopathies > congenital anosmia > degenerative disease > gene therapy > head trauma > health services > kidney disease > nephronopthisis > nerve cell > sense of smell > tiny hair-shaped structures
Researchers release the brakes on the immune system
18.10.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn
Norovirus evades immune system by hiding out in rare gut cells
12.10.2017 | University of Pennsylvania School of Medicine
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research