Dorsal root ganglia (DRG) are highly vulnerable to frataxin deficiency in Friedreich ataxia (FA). An immunohistochemical and immunofluorescence study of DRG in 15 FA cases and 12 controls revealed that FA causes major primary changes in satellite cells and inflammatory destruction of neurons. Reaction product of the cytoplasmic markers and laminin confirmed proliferation of satellite cells and processes into multiple perineuronal layers and residual nodules. The formation of connexin 43-reactive gap junctions between satellite cells was strongly upregulated. Proliferating satellite cells in FA displayed many more frataxin- and ATP5B-reactive mitochondria than normal. Monocytes entered into the satellite cell layer, appeared to penetrate neuronal plasma membranes, and infiltrated residual nodules. Satellite cells and IBA1-reactive monocytes displayed upregulated ferritin biosynthesis, which was most likely due to leakage of iron from dying neurons.

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