Apoptosis Detection in Retinal Ganglion Cells Using Quantitative Changes in Multichannel Fluorescence Colocalization

Area of Science:

• Biomedical imaging
• Molecular sensing
• Neuroscience

Background:

• Programmed cell death is crucial in neurodegenerative diseases like glaucoma.
• Existing methods for monitoring cell death in vivo are limited.
• KcapTR488, a dual-fluorophore peptide sensor, was previously synthesized but not validated in vivo.

Purpose of the Study:

• To evaluate the in vivo utility of KcapTR488 for real-time reporting of programmed cell death.
• To assess sensor delivery, kinetics, and activation in live rat models.
• To explore KcapTR488's potential for studying retinal ganglion cell (RGC) death pathways.

Main Methods:

• In vitro FRET analysis to quantify enzyme rates and selectivity.
• Ex vivo fluorescence microscopy to assess sensor delivery kinetics in rat models.
• Dual-color confocal microscopy of retinal tissue from healthy and NMDA-injured rats.

Main Results:

• In vitro experiments confirmed FRET between Texas Red and Alexa Fluor 488 (AF488) in KcapTR488.
• In healthy retinas, KcapTR488 localized to RGC nuclei, showing intact FRET signals.
• In NMDA-induced injury models, sensor activation was detected as early as 2 hours post-injection.
• Quantitative fluorescence colocalization changes proved superior to FRET for monitoring injury.
• Longitudinal monitoring showed cleaved sensor fragments undergoing anterograde axonal transport.

Conclusions:

• KcapTR488 is a viable tool for in vivo monitoring of programmed cell death in RGCs.
• The sensor enables early detection of retinal injury in preclinical models.
• KcapTR488 shows promise for advancing research into glaucoma and other RGC-related pathologies.