Gene Expression Profiles of Neurotrophic Factors in Rat Cultured Spinal Cord Cells Under Cyclic Tensile Stress

Abstract

An experimental study to investigate the in vitro gene expression of neurotrophic factors and receptors in cultured rat spinal cord cells subjected to cyclic mechanical stretch forces. We evaluated in vitro expression of neurotrophic factors and receptors in cultured rat spinal cord cells under cyclic tensile stress. Application of compressive mechanical stress to the spinal cord results in multiple changes making it difficult to examine the expression of neurotrophic factors and their receptors. There are no in vitro studies that investigated the biologic responses of cultured spinal cord cells to tensile stress. Spinal cord cells were isolated for culture from 15-day Sprague-Dawley rat embryos. We used the FX3000 Flexercell Strain Unit to induce mechanical stress. We analyzed the effects of mechanical stress on cell morphology, mRNA expression levels of various neurotrophic factors, and their immunoreactivities at 0, 2, 6, 12, 24, and 36 hours. Tensile stress for 6 hours resulted in reduction of spinal cord cells and loss of neurites. Cells that survived 24-hours stress showed swollen irregular-shaped soma, bleb formation, and fragmented neurites. The cell survival rate decreased, whereas lactate dehydrogenase release increased significantly at 6 hours. There were significant increases in mRNA expression levels of nerve growth factor, brain-derived neurotrophic factor, trkB, p75 neurotrophin receptor (p75), glial cell line-derived neurotrophic factor, and caspase-9 during the early period after application of tensile stress. Our results suggest survival of spinal cord neuronal cells under injurious tensile stress with increased synthesis and utilization of several neurotrophic factors, receptors, and expression of proteins related to cell apoptosis.