title: Strain rate-dependent induction of reactive astrogliosis and cell death in three-dimensional neuronal-astrocytic co-cultures.
abstract: A mechanical insult to the brain drastically alters the microenvironment as specific cell types become reactive in an effort to sequester severely damaged tissue. Although injury-induced astrogliosis has been investigated, the relationship between well-defined biomechanical inputs and acute astrogliotic alterations is not well understood. We evaluated the effects of strain rate on cell death and astrogliosis using a three-dimensional (3-D) in vitro model of neurons and astrocytes within a bioactive matrix. At 21 days post-plating, co-cultures were deformed to 0.50 shear strain at strain rates of 1, 10, or 30 s(-1). We found that cell death and astrogliotic profiles varied differentially based on strain rate at 2 days post-insult. Significant cell death was observed after moderate (10 s(-1)) and high (30 s(-1)) rate deformation, but not after quasi-static (1 s(-1)) loading. The vast majority of cell death occurred in neurons, suggesting that these cells are more susceptible to high rate shear strains than astrocytes for the insult parameters used here. Injury-induced astrogliosis was compared to co-cultures treated with transforming growth factor beta, which induced robust astrocyte hypertrophy and increased glial fibrillary acidic protein (GFAP) and chondroitin sulfate proteoglycans (CSPGs). Quasi-static loading resulted in increased cell density and CSPG secretion. Moderate rate deformation increased cell density, GFAP reactivity, and hypertrophic process density. High rate deformation resulted in increased GFAP reactivity; however, other astrogliotic alterations were not observed at this time-point. These results demonstrate that the mode and degree of astrogliosis depend on rate of deformation, demonstrating astrogliotic augmentation at sub-lethal injury levels as well as levels inducing cell death.
authors.affiliation: Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, 313 Ferst Dr., Atlanta, GA 30332-0535, USA.
authors.forename: D Kacy
authors.initials: DK
authors.lastname: Cullen
authors.forename: Crystal M
authors.initials: CM
authors.lastname: Simon
authors.forename: Michelle C
authors.initials: MC
authors.lastname: LaPlaca
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000502:physiology*; D018929:Cell Culture Techniques / Q000295:instrumentation* / Q000379:methods; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D018920:Coculture Techniques; D016207:Cytokines / Q000494:pharmacology; D004622:Embryo, Mammalian; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010812:Physical Stimulation / Q000295:instrumentation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D033081:Shear Strength; D013314:Stress, Mechanical
chemical_list: D016207:Cytokines; D005904:Glial Fibrillary Acidic Protein