Peripherin immunoreactive structures in amyotrophic lateral sclerosis

Increased levels of the neuron-specific intermediate filament, peripherin, have been recently detected in regenerating motor neurons of rat spinal cord after nerve transection. No data are yet available on peripherin expression in normal and diseased human spinal cord.

We have investigated the presence of peripherin immunoreactive structures in routinely processed spinal cord of human patients with amyotrophic lateral sclerosis and control cases by immunohistochemistry and immunoelectron microscopy. Adjacent sections were stained with antibodies to neurofilaments (NF) and ubiquitin.

In control cases, immunoreactivity for peripherin was found in neurons of dorsal root ganglia, in the posterior columns, in dorsal and ventral roots, and in scattered age-related axonal swellings. The cytoplasms of motor neurons were unstained. In amyotrophic lateral sclerosis cases most spheroids were immunoreactive for NF and to a lesser extent for peripherin. A few spheroids were strongly reactive for peripherin and were only weakly stained by antibodies to NF in adjacent sections. Both antibodies to NF and peripherin failed to demonstrate structures corresponding to the intraneuronal filamentous inclusions labeled by ubiquitin.

The accumulation of peripherin and NF in spheroids is likely related to the reduced anterograde transport. Alternatively, the spheroids showing a higher degree of peripherin immunoreactivity might represent regenerating axonal terminals.