Stretch-Induced Injury of Cultured Neuronal, Glial, and Endothelial Cells

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Abstract
Background and Purpose There is abundant evidence that after in vivo traumatic brain injury, oxygen radicals contribute to changes in cerebrovascular structure and function; however, the cellular source of these oxygen radicals is not clear. The purpose of these experiments was to use a newly developed in vitro tissue culture model to elucidate the effect of strain, or stretch, on neuronal, glial, and endothelial cells and to determine the effect of the free radical scavenger polyethylene glycol–conjugated superoxide dismutase (PEG-SOD; pegorgotein, Dismutec) on the response of each cell type to trauma. Methods Rat brain astrocytes, neuronal plus glial cells, and aortic endothelial cells were grown in cell culture wells with 2-mm-thick silastic membrane bottoms. A controllable, 50-millisecond pressure pulse was used to transiently deform the silastic membrane and thus stretch the cells. Injury was assessed by quantifying the number of cells that took up the normally cell-impermeable dye propidium iodide. Some cultures were pretreated with 100 to 300 U/mL PEG-SOD. Results Increasing degrees of deformation produced increased cell injury in astrocytes, neuronal plus glial cultures, and aortic endothelial cells. By 24 hours after injury, all cultures showed evidence of repair as demonstrated by cells regaining their capacity to exclude propidium iodide. Compared with astrocytes or neuronal plus glial cultures, endothelial cells were much more resistant to stretch-induced injury and more quickly regained their capacity to exclude propidium iodide. PEG-SOD had no effect on the neuronal or glial response to injury but reduced immediate posttraumatic endothelial cell dye uptake by 51%. Conclusions These studies further document the utility of the model for studying cell injury and repair and further support the vascular endothelial cell as a site of free radical generation and radical-mediated injury. On the assumption that, like aortic endothelial cells, stretch-injured cerebral endothelial cells also produce oxygen radicals, our results further suggest the endothelial cell as a site of therapeutic action of free radical scavengers after traumatic brain injury.