Light and electron microscopic demonstration of the p75 nerve growth factor receptor in normal human cutaneous nerve fibers: new vistas.
The nerve growth factor and its receptor are important in nerve growth, differentiation, maturation, and maintenance. In order to explore the exact distribution of p75 low-affinity nerve growth factor receptor (p75 NGFr) expression in cutaneous nerve fibers, p75 NGFr and neuron-specific enolase double immunofluorescence and immunoelectron microscopic studies were conducted on normal human skin samples. After p75 NGFr and neuron-specific enolase immunofluorescence double staining, the dermal nerves were strongly p75 NGFr-immunoreactive (IR); however, very few p75 NGFr-IR nerve fibers were found in the epidermis. p75 NGFr immunoreactivity was found mainly in the peripheral part of cutaneous nerve trunks and fibers, whereas neuron-specific enolase immunoreactivity was mainly seen within the axons. After ultrastructural immunostaining, the Schwann cell membrane was strongly p75 NGFr-IR. The Schwann cell membrane facing the connective tissue was more strongly p75 NGFr-IR than the part of the membrane close to the axon; the Schwann cell cytoplasm nearest to the membrane sometimes also showed a high p75 NGFr immunoreactivity, whereas the rest of the cytoplasm was generally more weakly p75 NGFr-IR; however, the axon itself seldom showed any such immunoreactivity; actually, only a few parts of the axonal membrane revealed a weak staining, leaving most of the membrane unstained. The axoplasm was not p75 NGFr-IR. The results--that in human cutaneous nerves it is mainly the Schwann cells that express p75 NGFr immunoreactivity--further stress the active role of the glial ensheathment in the control and maintenance of a normal target innervation.
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
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Liang
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Johansson
D005455:Fluorescent Antibody Technique; D006801:Humans; D016253:Microscopy, Immunoelectron; D009412:Nerve Fibers / Q000737:chemistry*; D010751:Phosphopyruvate Hydratase / Q000032:analysis; D017475:Receptors, Nerve Growth Factor / Q000032:analysis* / Q000276:immunology; D012867:Skin / Q000294:innervation* / Q000648:ultrastructure
D017475:Receptors, Nerve Growth Factor; D010751:Phosphopyruvate Hydratase