The localization of laminin and fibronectin on the Schwann cell basal lamina.

Abstract

Summary.The localization of laminin and fibronectin was examined on the basal laminae of Schwann cells. Basal laminae from sciatic nerves were isolated by sonication, and the localization of laminin and fibronectin on such isolated basal laminae was studied by immunoferritin histochemistry.Laminin was localized mainly on the cellular side (i.e. the side originally facing the Schwann cell plasma membrane) of the basal laminae.On the other hand, fibronectin was found to be present as aggregates only on the interstitial side (i.e., the side originally facing the endoneurial connective tissue) of the basal laminae.Thus, the locations of laminin and fibronectin were distinctly different. It is presumed that laminin might be involved in the attachment of axons and Schwann cells to the basal laminae, while fibronectin mediates the adhesion of the basal laminae to connective tissue elements, including the collagen fibrils.These findings are discussed from a standpoint of nerve regeneration through the basal laminae scaffolds of Schwann cells.Schwann cells are surrounded by basement membranes.As the pathways of their elongation regenerating axons utilize the Bungner's bands which are formed by Schwann cell processes with the basement membranes after denervation.It has been demonstrated that Schwann cells in grafted nerves, which have been killed by repetitive freezing and thawing, are phagocytized by macrophages, leaving the basement membranes, or more exactly, the basal laminae in a tube or scaffold, and that regenerating nerves always extend through such basal lamina scaffolds (IDE, 1983;IDE et al., 1983). This fact suggests that unlike the outer surface, the inner or adluminal surface of the basal lamina scaffolds has some particular constituents favorable to the attachment of axons and Schwann cells to the basal laminae.The basement membrane of Schwann cells, as that of epithelial and muscle cells, can be divided into three layers: the basal lamina, the lamina lucida and the reticular layer (lamina) (KEFALIDES et al., 1979). The basal lamina is the electron dense region which corresponds to the lamina densa of the glomerular basement membrane, the lamina lucida is in contact with the cell plasma membranes, and the reticular lamina faces the connective tissues. The glomerular basement membrane, which also consists of three layers, i.e. the lamina densa, the lamina rara interna and the externa, differs from that of other tissues in being devoid of reticular lamina having originated by the fusion of two basement membranes of different tissues belonging to the endothelium and the epitelium (FARQUHAR,1981).

Cold preserved nerve allografts: Changes in basement membrane, viability, immunogenicity, and regeneration

“…2A-C). Immunoelectron microscopy has confirmed the location of the laminin seen on light microscopy to be on the inner aspect of the SCBL, 66 and we have assumed this location in the present study. The intensity of laminin staining was similar in the stored and FT grafts, clearly present on all SCBL, blood vessels, and the perineurium.…”

“…11 Whereas the other components lie external to the basal lamina, only laminin is situated on the inner basal lamina in contact with regenerating axon cones. 66 Schwann cells must be in simultaneous contact with axon on one side and extracellular matrix on the other (a laminin receptor-laminin-collagen linkage) for normal Schwann cell production of basal lamina, ensheathment, and myelination. 11 Laminin has been shown to promote cell adhesion, growth, migration, differentiation, collagenase IV production, and phagocytosis in a variety of cell systems.…”

Role of Peripheral Nerve Extracellular Matrix in Schwann Cell Function and in Neurite Regeneration

“…32] have been detected in both endoneurium and perineurium, in regions corresponding to SC and perineurial cell basement membranes. Although fibronectin may be present in SC basement membrane [66], it is often difficult to resolve in this po sition by immunofluorescence because fibro nectin presents a light and diffuse staining pattern throughout the endoneurium. The perineurium is much more heavily stained for fibronectin than the endoneurium [5,28,51,55], SC basement membrane can be stained by four monoclonal antibodies (to an un characterized antigen) that do not stain base ment membranes of perineurial cells [57].…”

Merkel Cells Do Not Express Bullous Pemphigoid Antigen

“…IVand are overlayered with Lam [14], In contrast, BP Ag is not a component of the nerve basal lamina (unpublished data and fig. 4).…”