Histopathological changes of the spinal cord and motor neuron dynamics in SOD1 Tg mice.

We analyzed the histopathological changes and the number of motor neurons (MNs) in the lumbar spinal cord of Cu/Zn superoxide dismutase transgenic (SOD1Tg) mice, which are frequently used as a disease model of amyotrophic lateral sclerosis (ALS). In SOD1Tg mice, hyaline inclusions and foamy vacuoles in the neuronal cell body were observed at 7 weeks of age before neurologic symptoms, and large vacuoles, spheroid formation, and nerve cell aggregation became prominent after 13 weeks of age. The number of healthy MNs was 28.7 to 37.1 cells/animal in wild-type mice and 9.3 to 13.6 cells/animal in transgenic (Tg) mice. Furthermore, the number of MNs, including degenerative neurons, in Tg mice was 27.3-36.1 cells/animal at 18 weeks of age and 17.8-19.6 cells/animal at 21 weeks of age. The present results provide useful information for the development of drugs in ALS treatment.