Developmental changes of heat shock protein 73 in human brain.

The expression of heat shock protein (HSP) 73, a constitutive form of HSP, was evaluated immunohistologically in human brains, from embryos to adults. HSP 73 immunoreactivity was first detected in the embryo at 6 weeks of gestational age (GW) in the ventral horn cells of the spinal cord and the dorsal root ganglion cells. During the fetal period, the reactivity extended cranially, becoming detectable in the cerebral pyramidal cells at 40 GW. Glial cells in the spinal cord also showed HSP 73 immunoreactivity, from 22 GW. The time course of the development of HSP 73 immunoreactivity was mostly consistent with the time courses of overall neuronal and glial maturation, suggesting an increasing role of HSP 73 during neural cell differentiation.