Biomarker in the Eye Could Diagnose Neurodegeneration

Biomarker in the Eye Could Diagnose Neurodegeneration
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Neurofilament light chain (NfL), a promising protein biomarker of neurodegeneration, has been identified in the cerebrospinal fluid (CSF) and blood as a potential screening tool and prognostic indicator, may now be on the brink of clinical applicability.

A new study led by Boston Medical Center researchers found that Nfl is now detectable in the vitreous humor, or fluid within the eye. Published in Alzheimer’s Research & Therapy, the study establishes a foundation for future studies to investigate the potential of Nfl in Alzheimer’s disease, Parkinson’s disease, and other neurodegenerative diseases.

Early diagnosis and treatment for neurodegenerative diseases is essential to stop the deadly progression associated with these conditions. But having an accessible and reliable biomarker has been elusive.

In their study, the researchers measured the amount of Nfl in the eye and correlated that with amounts of amyloid beta, tau, inflammatory cytokines, vascular proteins. They also looked for correlations with apolipoprotein E genotypes (APOE), mini-mental state examination (MMSE) scores, systemic diseases and ophthalmic diseases.

The team studied collected vitreous samples from 77 patient undergoing previously scheduled eye surgery.  They detected Nfl in all 77 samples.  There was no association between Nfl and the patient’s ophthalmic condition, so the levels of Nfl in the vitreous humor do not appear to be influenced by their clinical eye conditions.  Similarly, no association was found between Nfl and APOE genotypes, MMSE scores, or systemic disease, such as diabetes.

However, NfL levels were positively associated with increased vitreous levels of Aβ40, Aβ42, and t-tau – well known biomarkers known to be associated with Alzheimer’s disease.

NfL also had significant associations with select inflammatory cytokines such as interleukin-15, IL-16, monocyte chemoattractant protein-1 (MCP1). Similarly, Nfl was also correlated with vascular proteins including vascular endothelial growth factor receptor-1 (VEGFR1), Vegf-C), vascular cell adhesion molecule-1 (VCAM-1), Tie-2, and intracellular adhesion molecular-1 (ICAM-1).

“Our results serve as a foundation for further investigation of NfL in the ocular fluids to inform us about the potential utility of its presence in the eye,” the authors write.

The study did not collect CSF and blood levels of NfL Aβ40, Aβ42, and t-tau, so the team was not able to study its correlation and discriminate vitreous levels with CSF and serum levels in order to compare it with established biomarkers of neurodegenerative disease. Moving ahead, the team suggests that further study on this will be very useful in assessing the utility of NfL in the eye fluid.