Prior poliomyelitis: an immunohistochemical study of cytoskeletal proteins and a marker for muscle fibre regeneration in relation to usage of remaining motor units.

Patients with prior poliomyelitis with paresis and excessive use (n = 8) and low use (n = 6) of residual anterior tibial motor units (MUs) during walking were subjected to muscle biopsy of the anterior tibial muscle (TA). Antibodies directed against cytoskeletal proteins, spectrin and desmin, and against Leu-19, a myoblast and satellite cell related antigen, were applied. In the patients with excessive use of residual MUs there was an almost total predominance of hypertrophic type I fibres. In the hypertrophic fibres, staining for spectrin and desmin was normal while staining for Leu-19 was seen in a few fibres. Scattered atrophic fibres seen in the patients with excessive use showed staining for spectrin, desmin and Leu-19. In the patients with low use of residual MUs there were extensive pathological muscle fibre changes. Increased staining for spectrin, desmin and Leu-19 was found in most of the atrophic fibres. The predominance of type I fibres in the patients with excessive use of residual MUs is suggested to be due to muscle fibre transformation. The normal staining pattern for spectrin and desmin in the hypertrophic fibres indicates a normal cytoskeletal structure which might suggest that the adaptive muscle fibre changes are adequate to meet the increased demand. The increased staining for spectrin, desmin and Leu-19 in the atrophic fibres might indicate an ongoing denervation process which earlier has been suggested as an important factor for the development of postpolio progressive muscular atrophy.