Laminins in the adult and aged brain.

Only recently have we become aware of the diversity of laminins in adult brain. In vascular basement membranes, the expression of at least five laminin chains has been demonstrated, suggesting the presence of several laminin variants. Recent ultrastructural evidence for heterogeneity of laminin expression in vascular basement membranes is an exciting finding, and points to structural and functional diversity of the basement membranes around cerebral blood vessels. Neuronal laminin-like immunoreactivity in the adult brain is a consistent observation, but does not fit well in the current understanding of the physiology and biochemistry of the heterotrimeric laminins. Nevertheless, the unique localization of putative neuronal laminins warrants their further characterization. The structure and function of laminins produced by reactive astrocytes in the lesioned adult brain and that seen in the brains of Alzheimer disease (AD) patients are not yet resolved. The possibility that these laminins play an important role in the CNS response to injury and pathophysiology of AD is expected to be a fruitful investigation. The next decade should see very significant advances in the characterization of brain laminins and, hopefully, in the elucidation of functional correlates to the structural diversity of laminins in brain.