NEI Study Reveals Annexin-V’s Role in Retinal Diseases

A recent study led by the National Eye Institute (NEI) has revealed new insights into annexin-V, a key biomarker traditionally used to track apoptosis (programmed cell death) and retinal cell degeneration in eye diseases. Published in the International Journal of Biological Sciences, the findings suggest that annexin-V also binds to immune cells, hinting at a potential role in detecting ocular inflammation.

Annexin-V's Established Role in Retinal Imaging

Annexin-V has long been a cornerstone in retinal research and clinical diagnostics. It is commonly used as a marker for apoptosis in retinal ganglion cells, which connect the retina to the brain for processing light and images. The degeneration of these cells, as seen in conditions like glaucoma, leads to vision loss and eventual blindness.

The biomarker is integral to an imaging technique called DARC (Detection of Apoptosing Retinal Cells), widely applied in research and clinical investigations over the last two decades. DARC imaging leverages fluorescently labeled annexin-V to identify apoptotic cells, providing a window into disease progression.

New Findings: Annexin-V and Immune Cell Interaction

While annexin-V has been instrumental in retinal research, uncertainties about its exact mechanisms prompted the NEI research team to reexamine its function. Their studies uncovered an unexpected discovery: annexin-V binds not only to apoptotic retinal ganglion cells but also to immune cells and a subset of microglial cells in the retina.

Microglial cells are the retina’s first responders to cellular damage or environmental changes, playing a crucial role in neuroinflammation. This finding suggests that annexin-V may serve as a marker for early inflammation, expanding its potential applications in retinal disease diagnostics.

Implications for DARC Imaging and Retinal Disease Diagnosis

The study’s findings challenge existing interpretations of DARC imaging, which primarily rely on annexin-V fluorescence counts to assess apoptosis. As Kiyoharu Miyagishima, PhD, study co-first author and NEI staff scientist, explains:

“Now we discovered that annexin-V also binds to immune cells, which complicates our interpretation of findings when using this biomarker.”

These findings necessitate a reevaluation of annexin-V's role in diagnosing retinal diseases and underscore the need for further research to clarify its interactions.

New Opportunities in Retinal Therapeutics

While the results introduce complexity in interpreting annexin-V's role, they also open the door to exciting new possibilities. The authors suggest that annexin-V could be leveraged to monitor microglial activation and neuroinflammation, with potential applications in understanding and treating neurodegenerative retinal diseases such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP).

With further study, annexin-V could serve as a dual-purpose biomarker for apoptosis and inflammation, advancing both diagnostics and therapeutics in retinal diseases.

These findings mark an important step toward refining imaging techniques and developing more targeted treatments for eye diseases, offering new hope for patients with retinal conditions.

Resource:

https://www.nei.nih.gov/about/news-and-events/news/nei-study-new-take-old-marker-cell-death