Connexin43 and astrocytic gap junctions in the rat spinal cord after acute compression injury

Abstract

To examine the possible role of interastrocytic gap junctions in the maintenance of tissue homeostasis after spinal cord damage, we initiated studies of the astrocytic gap junctional protein connexin43 (Cx43) in relation to temporal and spatial parameters of neuronal loss, reactive gliosis, and white matter survival in a rat model of traumatic spinal cord injury (SCI). Cx43 immunolocalization in normal and compression-injured spinal cord was compared by using two different sequence-specific anti-Cx43 antibodies that have previously exhibited different immunorecognition properties at lesion sites in brain. At 1- and 3-day survival times, gray matter areas with mild to moderate neuronal depletion exhibited a loss of immunolabeling with one of the two antibodies. At the lesion epicenter, these areas consisted of a zone that separated normal staining distal to the lesion from intensified labeling seen with both antibodies immediately adjacent to the lesion. Loss of immunoreactivity with only one of the two antibodies suggested masking of the corresponding Cx43 epitope. By 7 days post-SCI, Cx43 labeling was absent with both antibodies in all regions extending up to 1 mm from the lesion site. Reactive astrocytes displaying glial fibrillary acidic protein (GFAP) appeared by 1 day and were prominent by 3 days post-SCI. Their distribution in white and gray matter corresponded closely to that of Cx43 staining at 1 day, but less so at 3 days when GFAP-positive profiles were present at sites where Cx43 labeling was absent. By 7 days post-SCI, Cx43 again co-localized with GFAP-positive cells in the surviving subpial rim, and with astrocytic processes on radially oriented vascular profiles investing the central borders of the lesion. The results indicate that alterations in Cx43 cellular localization and Cx43 molecular modifications reflected by epitope masking, which were previously correlated with gap junction remodeling following excitotoxin-induced lesions in brain, are not responses limited to exogenously applied excitotoxins; they also occur in damaged spinal cord and are evoked by endogenous mechanisms after traumatic SCI. The GFAP/Cx43 co-localization results suggest that during their transformation to a reactive state, spinal cord astrocytes undergo a transitional phase marked by altered Cx43 localization or expression.

A model for ex vivo spinal cord segment culture—A tool for analysis of injury repair strategies

“…In damaged spinal cord, connexin43 levels are up-regulated within 4 h of injury, reaching two to three times normal level within one day, and lasting for at least 28 days (Theriault et al, 1997;Lee et al, 2005). Changes in connexin43 expression are associated with central nervous system inflammation, characterised by glial cell proliferation and phenotypic changes (Rouach et al, 2002).…”

Spatial and temporal activation of spinal glial cells: Role of gliopathy in central neuropathic pain following spinal cord injury in rats

“…Astrocytes communicate with neighboring neurons via synapses and gap junctions (Theriault et al, 1997). The radial branches of astrocytes synapse with single and/or several neurons or microglia; contributing to multiple astrocytic-neuronal and astocytic-microglial communication possibilities; whereas, microglia are freely motile and primarily play important roles in the endogenous immune responses (Bezzi et al, 2001; Mukaino et al, 2010).…”

Gap junction protein connexin43 (GJA1) in the human glaucomatous optic nerve head and retina

“…27 Connexin43 is the most abundant gap junction protein in the CNS and is primarily expressed on astrocytes. Alterations in connexin43 expression have been described following acute injury to the CNS [28][29][30][31][32][33][34] and in a variety of degenerative 35,36 and inflammatory diseases, 37 suggesting a role in the pathogenesis of neuronal damage. Furthermore, modulation of connexin43 expression has been shown to reduce neuronal death following traumatic and ischaemic injury to the brain 18 and spinal cord.…”