page_title: Glial scar
section_title: Reactive astrocytes
hierarchical_section_title: Glial scar / Scar components / Reactive astrocytes
caption_attribution_description: English: High magnification micrograph showing reactive astrocytes in massive cerebral ischemia leading to pseudolaminar necrosis. H&amp;E-LFB stain. Related images Very low mag. Intermed. mag. High mag.
context_page_description: Glial scar formation is a reactive cellular process involving astrogliosis that occurs after injury to the central nervous system. As with scarring in other organs and tissues, the glial scar is the body's mechanism to protect and begin the healing process in the nervous system.
  In the context of neurodegeneration, formation of the glial scar has been shown to have both beneficial and detrimental effects. Particularly, many neuro-developmental inhibitor molecules are secreted by the cells within the scar that prevent complete physical and functional recovery of the central nervous system after injury or disease. On the other hand, absence of the glial scar has been associated with impairments in the repair of the blood brain barrier.
context_section_description: Reactive astrocytes are the main cellular component of the glial scar. After injury, astrocytes undergo morphological changes, extend their processes, and increase synthesis of glial fibrillary acidic protein (GFAP). GFAP is an important intermediate filament protein that allows the astrocytes to begin synthesizing more cytoskeletal supportive structures and extend pseudopodia. Ultimately, the astrocytes form a dense web of their plasma membrane extensions that fills the empty space generated by the dead or dying neuronal cells (a process called astrogliosis). The heavy proliferation of astrocytes also modifies the extracellular matrix surrounding the damaged region by secreting many molecules including laminin, fibronectin, tenascin C, and proteoglycans. These molecules are important modulators of neuronal outgrowth.  Accordingly, their presence after injury contributes to inhibition of regeneration.
  Another important caveat of the astrocytic response to CNS injuries is its heterogeneity. Particularly, the response of the astrocytes to the injury varies depending on factors such as the nature of the injury and the microenvironment at the injury location. Further, the reactive astrocytes in the immediate vicinity of the injury increase gene expression, thus compounding the response of other astrocytes and contributing to the heterogeneity. Particularly, astrocytes closest to the lesion generally secrete more inhibitory molecules into the extracellular matrix.
caption: Micrograph of the superficial cerebral cortex showing neuron loss and reactive astrocytes in a person who suffered a stroke. H&E-LFB stain.
exif: {"Image Make": "Canon", "Image Model": "Canon EOS DIGITAL REBEL XSi", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2010:12:25 00:21:16", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "192", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "9118", "Thumbnail JPEGInterchangeFormatLength": "9076", "EXIF ExposureTime": "1/800", "EXIF FNumber": "0", "EXIF ExposureProgram": "Aperture Priority", "EXIF ISOSpeedRatings": "1600", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2010:12:23 09:23:40", "EXIF DateTimeDigitized": "2010:12:23 09:23:40", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "77/8", "EXIF ApertureValue": "2147483648", "EXIF ExposureBiasValue": "-1/3", "EXIF MeteringMode": "Spot", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "0", "EXIF SubSecTime": "63", "EXIF SubSecTimeOriginal": "63", "EXIF SubSecTimeDigitized": "63", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2848", "EXIF ExifImageLength": "4272", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "8994", "EXIF FocalPlaneXResolution": "2136000/439", "EXIF FocalPlaneYResolution": "356000/73", "EXIF FocalPlaneResolutionUnit": "2", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF SceneCaptureType": "Standard"}