Structural remodeling of gray matter astrocytes in the neonatal pig brain after hypoxia/ischemia.
Astrocytes play a vital role in the brain; their structural integrity and sustained function are essential for neuronal viability, especially after injury or insult. In this study, we have examined the response of astrocytes to hypoxia/ischemia (H/I), employing multiple methods (immunohistochemistry, iontophoretic cell injection, Golgi-Kopsch staining, and D-aspartate uptake) in a neonatal pig model of H/I. We have identified morphological changes in cortical gray matter astrocytes in response to H/I. Initial astrocytic changes were evident as early as 8 h post-insult, before histological evidence for neuronal damage. By 72 h post-insult, astrocytes exhibited significantly fewer processes that were shorter, thicker, and had abnormal terminal swellings, compared with astrocytes from control brains that exhibited a complex structure with multiple fine branching processes. Quantification and image analysis of astrocytes at 72 h post-insult revealed significant decreases in the average astrocyte size, from 686 microm(2) in controls to 401 microm(2) in H/I brains. Sholl analysis revealed a significant decrease (>60%) in the complexity of astrocyte branching between 5 and 20 microm from the cell body. D-Aspartate uptake studies revealed that the H/I insult resulted in impaired astrocyte function, with significantly reduced clearance of the glutamate analog, D-aspartate. These results suggest that astrocytes may be involved in the pathophysiological events of H/I brain damage at a far earlier time point than first thought. Developing therapies that prevent or reverse these astrocytic changes may potentially improve neuronal survival and thus might be a useful strategy to minimize brain damage after an H/I insult.
Sullivan
Susan M
SM
UQ Centre for Clinical Research and Perinatal Research Centre, The University of Queensland, Herston, Brisbane, Queensland 4029, Australia. susan.sullivan@uq.edu.au
Björkman
S Tracey
ST
Miller
Stephanie M
SM
Colditz
Paul B
PB
Pow
David V
DV
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000473:pathology* / Q000502:physiology; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D048429:Cell Size; D026603:D-Aspartic Acid / Q000378:metabolism; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology* / Q000503:physiopathology; D007150:Immunohistochemistry; D007546:Isoquinolines; D008297:Male; D036421:Nerve Fibers, Unmyelinated; D013552:Swine; D013997:Time Factors
D005904:Glial Fibrillary Acidic Protein; D007546:Isoquinolines; D018698:Glutamic Acid; D026603:D-Aspartic Acid; C017475:lucifer yellow