Photoreceptor cell death by apoptosis in dogs with sudden acquired retinal degeneration syndrome.

OBJECTIVE

To examine the role of apoptosis in retinal photoreceptor degeneration in dogs with sudden acquired retinal degeneration syndrome (SARDS).

SAMPLE POPULATION

Retinas from 3 dogs with SARDS and from 2 clinically normal adult dogs.

PROCEDURE

Apoptosis was identified by in situ end-labeling and observation of characteristic morphologic changes by light microscopy.

RESULTS

The degree of photoreceptor degeneration varied with duration of vision loss in SARDS-affected eyes. The retina of all 3 SARDS-affected eyes had numerous (34, 61, and 70) apoptotic nuclei per section that were overwhelmingly located in the outer nuclear layer. Apoptotic nuclei were not detected, or were rare in similarly sized retinal sections from normal dogs. Inflammation was not an important feature of SARDS.

CONCLUSIONS

Apoptosis appears to be at least 1 mechanism of photoreceptor cell death in dogs with SARDS.

CLINICAL RELEVANCE

Because apoptosis appears to be a final common pathway in many retinal degeneration syndromes, future treatment strategies that control apoptosis in other diseases may be applicable to dogs with SARDS. Halting this pathway may allow some photoreceptors to survive and, perhaps, preserve vision.