CD44 expression in tuberous sclerosis.

CD44, a cell adhesion molecule, mediates cell-cell and cell-matrix interactions. In the central nervous system, CD44 is expressed in astrocytic processes, predominantly in white matter and subpial regions, suggesting its involvement in the maintenance of a stable central nervous system cytoarchitecture. In this study, we investigated immunohistochemically the expression of CD44 and glial fibrillary acidic protein in neurosurgically resected specimens of patients with or without tuberous sclerosis. In controls, CD44 immunoreactivity was noted in the processes of astrocytes close to blood vessels and subpial cortex. Glial fibrillary acidic protein immunoreactivity was noted in both cell bodies and cytoplasmic processes of astrocytes in white matter. In tubers, CD44 antigen was also noted in the processes of astrocytes close to blood vessels and pial surface, and in abundance in the network of astrocyte processes. Moreover, CD44 antigen showed immunoreactive halos around balloon cells in tubers and around tumor cells in subependymal lesions. Glial fibrillary acidic protein antigen was noted in both cell bodies and cytoplasmic processes of some balloon cells in tubers, but not in tumor cells. In Western blot analyses, the CD44 immunoreactive band was more intense in tubers or subependymal giant-cell tumors than in control tissue. This increase in CD44 antigen seemed to correlate with the degree of astrogliosis. Immunoreactivity surrounding the cell surfaces of balloon or tumor cells suggests that the clustering of these cells may be due to the expression of CD44. Glial fibrillary acidic protein immunoreactive band was detected in tubers, but not in subependymal giant cell tumors.