A newly developed fluorescent imaging probe has the groundbreaking ability to measure the loss of smell—medically referred to as anosmia—in a way that is both objective and non-invasive. By focusing on the olfactory nerve, this innovative tool could replace the need for biopsies that are currently used to diagnose certain types of anosmia and could assist in creating new treatment methods. This research appeared in the August edition of The Journal of Nuclear Medicine.
Studies indicate that around 13.3 million adults in the United States experience various smell disorders, with 3.4 million suffering from severe hyposmia or complete anosmia. However, these findings were published before the COVID-19 pandemic, likely underestimating the true number of individuals currently affected by such disorders.
Dr. Dauren Adilbay, an assistant professor in the Otolaryngology/Head and Neck Surgery Department at the Medical University of South Carolina in Charleston, stated, “Despite how crucial the sense of smell is for quality of life, and the widespread nature of anosmia, there are currently no objective, user-independent methods to evaluate smell perception available in clinical or research settings.” The team aimed to explore a new approach for diagnosing smell loss using a specific fluorescent imaging agent known as Tsp1a-IR800P.
This agent targets sodium channel 1.7 (Nav1.7), essential for olfaction as it facilitates signals traveling to the olfactory bulb. To assess Nav1.7 levels, researchers employed Tsp1a-IR800P imaging on both mice with a normal sense of smell and those with chemically induced anosmia. Additional imaging tests were carried out on olfactory epithelium tissues from non-human primates, as well as olfactory epithelium from hamsters infected with COVID-19 and human cadavers of patients who had previously tested positive for the virus.
The results revealed that Nav1.7 was highly expressed in subjects with normal smell, while individuals with anosmia showed a marked reduction in Nav1.7 expression, indicated by a weaker fluorescence signal. The study noted that the intensity of this fluorescence signal correlated with the extent of damage; lower signals suggest loss of smell, while stronger signals could indicate a positive response to treatment and potential recovery of the sense.
The authors of the study highlighted that this fluorescent imaging agent could be utilized in medical offices with an endoscope for diagnosing smell disorders. It also offers immediate applicability in preclinical investigations involving animal models—an area that currently lacks objective and non-invasive assessment tools—that could evaluate the effectiveness of drug treatments aimed at restoring the sense of smell, thereby fostering the development of new therapeutic options.
Dr. Naga Vara Kishore Pillarsetty, a professor in the Department of Radiology at Memorial Sloan Kettering Cancer Center in New York, commented, “Timely detection of smell disorders could lead to quick interventions to treat or slow down the disease, ultimately enhancing patients’ quality of life.” This advancement could pave the way for similar imaging agents for other sensory and neurological conditions, expanding the possibilities of molecular imaging.
