Dendritic abnormalities in retinal ganglion cells of three-month diabetic rats.

PURPOSE

To determine the effect of three-month diabetes on the retinal ganglion cell (RGC) morphology and density.

METHODS

Experimental diabetes was induced in Sprague-Dawley rats by intraperitoneal injection of streptozotocin (STZ). Retinas from three-month diabetic and age-matched control rats were harvested, and immunohistochemistry with monoclonal anti-Thy-1 antibody was carried out for calculating RGC density. Random RGC labeling with gene gun propelled lipophilic fluorescent dye, DiI, coated particles (DiOlistic method) was done for detailed RGC classification, dendritic field, and soma size measurement.

RESULTS

The number of Thy1-labeled RGCs in the three-month diabetic rats was significantly reduced compared with that in the age-matched control. Obvious RGC morphology changes were observed, and the number of RGCs that could not be classified was significantly greater in the diabetic retinas. Among those well-classified RGCs, cells with enlarged dendritic fields were more frequently seen in the RGA group (401+/-86 um, n = 59, P < 0.001), but the soma sizes were unchanged from the controls (P > 0.05). For cells in the groups of RGB and RGC, no significant changes in the dendritic fields and soma sizes were found (P > 0.05).

CONCLUSIONS

In the three-month STZ-induced diabetic rat, retinal ganglion cell loss is associated with morphology change. The surviving RGCs in the diabetic retina, especially those in RGA group, show significant dendritic field enlargement. This plasticity of the surviving RGC dendrites may represent a compensatory response to the overall loss of RGCs in diabetes.