Immunohistochemical analysis of laminin components in the blood–nerve barrier and blood–brain barrier

Abstract

AbstractObjectiveThe blood–brain barrier (BBB) and blood–nerve barrier (BNB) play crucial roles in the maintenance of the central and peripheral nervous system. It had previously been thought that the BNB was leaky compared with the BBB, but several recent reports showed that the BNB has almost the same properties as a barrier system as the BBB, suggesting that the specific structural component of the basement membrane (especially laminin) in the BNB acts as a distinct barrier. Although the role of the laminin isoforms has been linked to BBB, the laminins in the BNB still remain unknown. Here, we aim to show the laminin components in the BNB and BBB.MethodsThe laminin isoforms (α5, α4, β1, β2 and γ1) were immunohistochemically analyzed in the brain and a median nerve specimen of a post‐mortem amyotrophic lateral sclerosis patient. Then the expression of these laminin isoforms was scrutinized in sural nerve specimens of some peripheral neuropathies.ResultsThe present histological data showed that laminin α4 was hardly present in BNB compared with BBB, whereas other laminin isoforms were widely expressed in BBB and BNB. Additionally, laminin α4 in BNB decreased in both amyotrophic lateral sclerosis and the peripheral neuropathies in which the BNB was supposed to be broken down.ConclusionsLaminin α4 did not decrease in BBB, but did decrease in BNB in the patients with or without peripheral neuropathies. As previous reports showed that laminin α4 is essential for T lymphocytes to migrate across the BBB, these results suggested that BNB might have a distinct mechanism for T cell migration that does not require laminin α4.