Parkinson’s disease is a neurodegenerative disorder usually associated with motor symptoms such as tremors, stiffness, and slowed movements. However, another common symptom of Parkinson’s disease is loss of smell, also known as hyposmia or anosmia.
Studies show that about 75-90% of Parkinson’s patients report a reduced sense of smell, even before the onset of motor symptoms.
Researchers at the Yale School of Medicine have discovered the biological mechanism behind the loss of smell in Parkinson’s disease, a common but less studied symptom.
Using a mouse model with alpha-synuclein A30P, they found that mice with later symptoms of Parkinson’s disease showed olfactory impairment due to severe pathology in projection neurons of the olfactory pathway and reduced neurogenesis in the olfactory bulb. This is in contrast to healthy aging brains, which continue to form new neurons in the olfactory bulb throughout life.
Patients with Parkinson’s disease report a reduced sense of smell for years, said corresponding author Dr. Charles Greer, deputy director of the study in the division of neurosurgery and professor of neurology at Yale School of Medicine. However, because the motor symptoms of the disease have been more debilitating, very little research has been done to understand the underlying biological mechanism of the olfactory dimension.
Sriganga Chandra, MD, associate professor of neurology and neuroscience at Yale University, said, “We are excited to begin to understand the basis of anosmia in patients with Parkinson’s disease.”
Dr. Greer. said, “We set out to understand the nature of a symptom associated with Parkinson’s disease that is largely anecdotal. People diagnosed with Parkinson’s disease report loss of smell up to 10 years before diagnosis. These findings could help develop a tool for very early diagnosis of the disease.
“α-synuclein pathology and reduced neurogenesis in the olfactory system affect olfaction in a mouse model of Parkinson’s disease” provides an overview of the research question and the context of the study.
The experiment focused on Parkinson’s disease, which is a neurodegenerative disorder characterized by motor symptoms such as tremors, stiffness and slowed movements. The introduction emphasizes that Parkinson’s disease is also associated with non-motor symptoms, such as loss of smell or olfactory impairment. The researchers explain that about 75-90% of patients with Parkinson’s disease report a reduced sense of smell, even before the onset of motor symptoms, and that this symptom is now recognized as a non-motor symptom of Parkinson’s disease.
This study investigated how Parkinson’s disease affects the sense of smell in mice. The researchers found that mice with advanced symptoms of Parkinson’s disease had problems with their sense of smell, which was linked to changes in their brains. Specifically, the mice had damage to specific cells in the olfactory pathway. They reduce the growth of new cells in the olfactory bulb, which can contribute to problems with the sense of smell.
The researchers also found problems with how the cells in the olfactory bulb communicate with each other. These findings suggest that Parkinson’s disease may affect the sense of smell by causing damage to certain parts of the brain.
This study used mice with a condition that mimics Parkinson’s disease to understand how the disease affects their sense of smell. The researchers found that mice with advanced symptoms of Parkinson’s disease had problems with smell linked to changes in specific brain cells.
They also found that the mice had fewer new cells growing in their olfactory bulb and problems with the way the cells communicate with each other. These changes likely contribute to the olfactory problems seen in Parkinson’s disease.
Overall, the study provides important insight into the biological mechanisms underlying olfactory impairment in Parkinson’s disease and suggests potential therapeutic strategies to improve olfactory function in these patients. The conclusion highlights the importance of these findings and their potential implications for the study and treatment of Parkinson’s disease.
- Eduardo Martin-Lopez, DJ Vidyadhara, etal.α-synuclein pathology and reduced neurogenesis in the olfactory system affect olfaction in a mouse model of Parkinson’s disease. Journal of Neuroscience DOI: 10.1523/JNEUROSCI.1526-22.2022