Reduction of glial fibrillary acidic protein-immunoreactive astrocytes in some brain areas of old hairless rhino-j mice (hr-rh-j).

Mutations in the hairless (hr) gene of mice result in hair follicle and other epithelial defects. The hr gene is expressed at high levels in the brain where it probably participates in the survival and maintenance of some neuronal populations, but whether it also supports glial populations of the central nervous system has been not investigated. To clarify this, quantitative immunohistochemistry for astrocytes (glial fibrillary acidic protein (GFAP)) and microglial cells (CD11b macrophage antigen) was used in the brain of a mutant mouse strain, the hairless (hr-rh-j) type, which carries the homozygous hr gene rhino mutation. The glial cell density was assessed in the cerebral cortex, hippocampus, striatum, hypothalamus and cerebellum of young (3 months) and old (9 months) hr-rh-j mice. No significant differences were found between young wild-type and hr-rh-j mice. The density of GFAP immunoreactive astrocytes normally increased as a function of age, but in older hr-rh-j mice there was a severe reduction (P<0.01) in the striatum, hypothalamus, and hippocampus. Conversely, the microglial cells were insensible to aging or to hr-rh-j mutation. These results suggest that the hr gene is involved in the maintenance of the GFAP immunoreactive cells in some cerebral areas. Nevertheless, because these animals do not show any neurological signs, the functional significance of the present findings remains to be established.