Abstract
Purpose: :
To assess the histopathological changes in a postmortem sample derived from an eye donor with Macular Telangiectasia Type 2 (MacTel type 2) to gain further insight into the cause of the disease. MacTel type 2 affects such a specific region around the fovea that is consistent in terms of clinical observations between patients, the specificity of this region might be due to anatomical/biochemical differences in the macula compared to the rest of the retina.
Methods: :
Macular pigment distribution of freshly dissected eyes was photographed. Sections of the retina-RPE-choroid complex from both the macular and peripheral regions were assessed using antigen retrieval and immunohistochemistry to study the distribution of cell-specific markers for blood vessels, glial cells, microglia and photoreceptors. Using anatomical landmarks the sections were matched with the macular pigment distribution and a fluorescein angiogram that was taken before the donors’ death.
Results: :
Macular pigment was absent in the macula. Abnormally dilated capillaries were indentified in a macula that correlated spatially with regions of fluorescein leakage in an angiogram that was taken 12 years prior to death. These telangiectatic vessels displayed a marked reduction of the basement membrane component collagen IV, indicating vascular pathology. GFAP was limited to retinal astrocytes and no reactive Müller cells were identified. Importantly, reduced immunoreactivity with Müller cell markers (vimentin, glutamine synthetase and retinaldehyde binding protein) in the macula was observed, which correlated to the region of depleted macular pigment.
Conclusions: :
These findings suggest that macular Müller cell loss or dysfunction is a critical component of MacTel type 2, which may have implications for future treatment strategies. Due to the spatially restricted pathology in MacTel type 2, we also conclude that the specificity of the disease area implies that there is a fundamental biological or biochemical difference between the retina in the macula and the periphery.
Keywords: macula/fovea • Muller cells • pathobiology