Abstract
Retinal degenerative diseases, such as Retinitis Pigmentosa and Age-Related Macular Degeneration are characterized by selective degeneration of photoreceptors. Routine clinical methods neither allow confirmed diagnosis nor an assessment of extent and severity of the degeneration. We asked if Peanut Agglutinin (PNA) could selectively label mammalian retinal cones in vivo, when administered intravitreally. We injected FITC-conjugated PNA intravitreally into anesthetized mouse, guinea pig or monkey, and found it to stain cones, selectively and reversibly. To examine if PNA affected other retinal neurons, we immunostained them for several retinal cell markers, and found their expression indistinguishable from normal. TUNEL assay did not show any PNA-induced apoptosis. Visual behavior of animals in a Visual Cliff test 10 hours after the PNA injection showed no impairment. Finally, PNA-stained cones in an animal model of photoreceptor degeneration showed a pattern that reflected progressive degeneration. Together, these findings demonstrate that intravitreally injected PNA can selectively bind to mammalian cones in vivo without causing, at least any overt adverse effects. We propose this as a potential tool to make a confirmed diagnosis, and to assess the extent and severity of photoreceptor degeneration in some of the retinal degenerative diseases in humans.
This work was supported by grants from NBRC and DBT (BT/PR6615/MED/14/857/2005)