engleski

Neuroplastin: from neurodevelopment to neurodegeneration

Neuroplastin, glycoprotein found in two splice isoforms (np65, np55), is a member of immunoglobulin superfamily including different cell adhesion molecules. Brain-specific localization of np65 isoform and its association with synaptic plasticity and long-term potentiation was found in rodent brain. Distribution of np65 in adult human brain has been described, however systematic data on its expression during developmental stages, maturation, aging and neurodegeneration are lacking. The aim of our study was to investigate the developmental expression of neuroplastin in human hippocampal tissue as well as in hippocampal tissue affected by Alzheimer’s disease (AD). Paraffin-embedded sections of human hippocampi of different prenatal and postnatal ages (ranging from 12 gestational weeks to young adulthood) and hippocampal sections derived from AD and age/gender-matched controls were analyzed by immunohistochemistry. Sections were analyzed using an optical microscope and digitally by the ImageJ software which enabled quantitative analysis of neuroplastin immunoreactivity patern and intensity. Neuroplastin immunoreactivity in human hippocampal tissue was detected at 22nd gestational week the earliest, and was gradually higher with increasing gestational age. Development of characteristic adult pattern of neuroplastin immunoreactivity in different layers of dentate gyrus was also observed. Immunohistochemical analysis of AD hippocampal tissue showed increased neuroplastin immunoreactivity when compared with control sections, markedly in the neuronal population of the dentate gyrus inner molecular layer. Furthermore, a disturbed organisation of neuroplastin immunoreactive fibers of CA1 radial layer was observed in AD sections. Increased neuroplastin expression in human hippocampus during brain development coincides with formation of hippocampal synapses, indicating that neuroplastin is one of the molecules involved in synaptogenesis and regulation of synaptic plasticity. Additionally, altered expression of neuroplastin in the hippocampus in Alzheimer’s disease may be associated with attempt of tissue reorganization and compensatory response to neurodegeneration. This study is the first report encompassing data on neuroplastin expression in human fetal hippocampal tissue and hippocampal tissue affected by Alzheimer’s neurodegeneration. We suggest that neuroplastin may serve as a plasticity marker, as its expression is increased in critical neurodevelopmental stages as well as during reorganization and plasticity reactivation in neurodegeneration. The results of the study strongly support presumed important roles and involvement of neuroplastin in neurodevelopmental and neurodegenerative processes.

neuroplastin; neurodevelopment; neurodegeneration

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