Cyclic Mechanical Stretch Stress Enhances BDNF and NT-3 immunoreactivity in Cultured Spinal Cord Neuronal, Glial cells

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Study Design. A rat model designed to investigate the effects of applied cyclic stretch stress on neurotrophic factor synthesis in the rat spinal cord cells in vitro.Objective. To evaluate the neurotrophic response in vitro neuron and glia cell under mechanical stress using immunohistological analysis.Summary of Background Data. Recent studies conducted in animals with experimental spinal cord damage examined the function, source and dynamics of induction of endogenious neurotrophic factors including brain-derived neurotrophic factor (BDNF), neurotrophin (NT)-3. To our knowledge, there are no studies that examined biological and pathological responses to mechanical stress in cultured cells derived from spinal cord.Methods. The cultured spinal cord cells were isolated from 14 day Sprague-Dawley rat embryos. For providing mechanical stress to cells, FX-3000TM-Flexercell Strain Unit (Flexercell International Corp., McKeesport, PA, USA) was used. After starting application of stimulation, the cell morphology and immunoreactivity was observed over time (0, 1, 2, 6, 12 and 48 hours).Results. Decrease in the number of surviving neuron, thickening of cell membrane and extention of intercellular substance were observed after providing stress to cells for 6 hours or more. The number of microtubule-associated protein (MAP)-2 positive cells decreases with time, while the number of glial fibrillary acidic protein GFAP positive cells was comparatively kept against stress. For astrocytes, the number of anti-GFAP/BDNF and NT-3 antibody positive cells was comparatively kept with the lapse of stress time, but observation over time revealed a high immuno-reactivity of the remaining anti-GFAP positive cells.Conclusion. Our results indicate that reactive astrocytes increase the expression of neurotrophic factors to the mechanical stress, a possibility that reactive astrocytes against mechanical stress in cultured cells are involved in the prolongation of survival and mechanical repair.