Mao, Y, Nguyen, T, Tonkin, RS, Lees, JG, Warren, C, O'Carroll, SJ, Nicholson, LFB, Green, CR, Moalem-Taylor, G & Gorrie, CA 2017, 'Characterisation of Peptide5 systemic administration for treating traumatic spinal cord injured rats.', Experimental Brain Research, vol. 235, no. 10, pp. 3033-3048.View/Download from: UTS OPUS or Publisher's site
Systemic administration of a Connexin43 mimetic peptide, Peptide5, has been shown to reduce secondary tissue damage and improve functional recovery after spinal cord injury (SCI). This study investigated safety measures and potential off-target effects of Peptide5 systemic administration. Rats were subjected to a mild contusion SCI using the New York University impactor. One cohort was injected intraperitoneally with a single dose of fluorescently labelled Peptide5 and euthanised at 2 or 4 h post-injury for peptide distribution analysis. A second cohort received intraperitoneal injections of Peptide5 or a scrambled peptide and was culled at 8 or 24 h post-injury for the analysis of connexin proteins and systemic cytokine profile. We found that Peptide5 did not cross the blood-spinal cord barrier in control animals, but reached the lesion area in the spinal cord-injured animals without entering non-injured tissue. There was no evidence that the systemic administration of Peptide5 modulates Connexin43 protein expression or hemichannel closure in the heart and lung tissue of SCI animals. The expression levels of other major connexin proteins including Connexin30 in astrocytes, Connexin36 in neurons and Connexin47 in oligodendrocytes were also unaltered by systemic delivery of Peptide5 in either the injured or non-injured spinal cords. In addition, systemic delivery of Peptide5 had no significant effect on the plasma levels of cytokines, chemokines or growth factors. These data indicate that the systemic delivery of Peptide5 is unlikely to cause any off-target or adverse effects and may thus be a safe treatment option for traumatic SCI.
Mao, Y, Tonkin, RS, Nguyen, T, O'Carroll, SJ, Nicholson, LF, Green, CR, Moalem-Taylor, G & Gorrie, CA 2017, 'Systemic administration of Connexin43 mimetic peptide improves functional recovery following traumatic spinal cord injury in adult rats.', Journal of Neurotrauma, vol. 34, no. 3, pp. 707-719.View/Download from: UTS OPUS or Publisher's site
Blocking of Connexin43 hemichannels, the main gap junction protein located on astrocytes in the central nervous system, has been shown to reduce neural injury in a number of models. We previously demonstrated that local administration of a Connexin43 mimetic peptide, Peptide5, reduces secondary tissue damage after spinal cord injury (SCI). Here, we investigated whether acute systemic delivery of Peptide5 is also protective in a model of SCI. Rats were subjected to a mild spinal cord contusion using the MASCIS impactor and were injected intraperitoneally with Peptide5 or a scrambled peptide immediately and at 2 and 4 hours post-injury. Rats were tested for locomotor recovery and pain hypersensitivity and euthanised at 8 hours, 24 hours, 2 weeks or 6 weeks post-injury. Compared to control rats, Peptide5 treated rats showed significant improvement in hindlimb locomotor function between 3 and 6 weeks post-injury and reductions in at-level mechanical allodynia from week 1 post-injury. Immunohistochemistry showed that Peptide5 treatment led to a reduction in total Connexin43 and increased phosphorylated Connexin43 at 8 hours compared to scrambled peptide. At 2 and 6 weeks, lesion size, the astrocytic and the activated macrophage and/or microglial response were all decreased in the Peptide5 animals. Additionally, neuronal cell numbers were higher in the Peptide5 animals compared to the scrambled peptide treated rats at 2 and 6 weeks. These results show for the first time that systemic administration of Peptide5 to block the pathological opening of Connexin43 hemichannels is a feasible treatment strategy in this setting, ameliorating the secondary SCI.
Nguyen, T, Mao, Y, Sutherland, T & Gorrie, CA 2017, 'Neural progenitor cells but not astrocytes respond distally to thoracic spinal cord injury in rat models.', Neural regeneration research, vol. 12, no. 11, pp. 1885-1894.View/Download from: UTS OPUS or Publisher's site
Traumatic spinal cord injury (SCI) is a detrimental condition that causes loss of sensory and motor function in an individual. Many complex secondary injury cascades occur after SCI and they offer great potential for therapeutic targeting. In this study, we investigated the response of endogenous neural progenitor cells, astrocytes, and microglia to a localized thoracic SCI throughout the neuroaxis. Twenty-five adult female Sprague-Dawley rats underwent mild-contusion thoracic SCI (n = 9), sham surgery (n = 8), or no surgery (n = 8). Spinal cord and brain tissues were fixed and cut at six regions of the neuroaxis. Immunohistochemistry showed increased reactivity of neural progenitor cell marker nestin in the central canal at all levels of the spinal cord. Increased reactivity of astrocyte-specific marker glial fibrillary acidic protein was found only at the lesion epicenter. The number of activated microglia was significantly increased at the lesion site, and activated microglia extended to the lumbar enlargement. Phagocytic microglia and macrophages were significantly increased only at the lesion site. There were no changes in nestin, glial fibrillary acidic protein, microglia and macrophage response in the third ventricle of rats subjected to mild-contusion thoracic SCI compared to the sham surgery or no surgery. These findings indicate that neural progenitor cells, astrocytes and microglia respond differently to a localized SCI, presumably due to differences in inflammatory signaling. These different cellular responses may have implications in the way that neural progenitor cells can be manipulated for neuroregeneration after SCI. This needs to be further investigated.
Sutherland, TC, Mathews, KJ, Mao, Y, Nguyen, T & Gorrie, CA 2017, 'Differences in the Cellular Response to Acute Spinal Cord Injury between Developing and Mature Rats Highlights the Potential Significance of the Inflammatory Response.', Frontiers in Cellular Neuroscience, vol. 10, pp. 1-18.View/Download from: UTS OPUS or Publisher's site
There exists a trend for a better functional recovery from spinal cord injury (SCI) in younger patients compared to adults, which is also reported for animal studies; however, the reasons for this are yet to be elucidated. The post injury tissue microenvironment is a complex milieu of cells and signals that interact on multiple levels. Inflammation has been shown to play a significant role in this post injury microenvironment. Endogenous neural progenitor cells (NPC), in the ependymal layer of the central canal, have also been shown to respond and migrate to the lesion site. This study used a mild contusion injury model to compare adult (9 week), juvenile (5 week) and infant (P7) Sprague-Dawley rats at 24 h, 1, 2, and 6 weeks post-injury (n = 108). The innate cells of the inflammatory response were examined using counts of ED1/IBA1 labeled cells. This found a decreased inflammatory response in the infants, compared to the adult and juvenile animals, demonstrated by a decreased neutrophil infiltration and macrophage and microglial activation at all 4 time points. Two other prominent cellular contributors to the post-injury microenvironment, the reactive astrocytes, which eventually form the glial scar, and the NPC were quantitated using GFAP and Nestin immunohistochemistry. After SCI in all 3 ages there was an obvious increase in Nestin staining in the ependymal layer, with long basal processes extending into the parenchyma. This was consistent between age groups early post injury then deviated at 2 weeks. The GFAP results also showed stark differences between the mature and infant animals. These results point to significant differences in the inflammatory response between infants and adults that may contribute to the better recovery indicated by other researchers, as well as differences in the overall injury progression and cellular responses. This may have important consequences if we are able to mirror and manipulate this response in patients of all ages; howev...
Mao, Y, Mathews, K & Gorrie, CA 2016, 'Temporal Response of Endogenous Neural Progenitor Cells Following Injury to the Adult Rat Spinal Cord', FRONTIERS IN CELLULAR NEUROSCIENCE, vol. 10.View/Download from: UTS OPUS or Publisher's site
Mao, Y, Nguyen, T, Sutherland, T & Gorrie, CA 2016, 'Endogenous neural progenitor cells in the repair of the injured spinal cord.', Neural regeneration research, vol. 11, no. 7, pp. 1075-1076.View/Download from: UTS OPUS or Publisher's site
Chen, H, Chan, YL, Nguyen, LT, Mao, Y, de Rosa, A, Beh, IT, Chee, C, Oliver, B, Herok, G, Saad, S & Gorrie, C 2016, 'Moderate traumatic brain injury is linked to acute behaviour deficits and long term mitochondrial alterations', CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, vol. 43, no. 11, pp. 1107-1114.View/Download from: UTS OPUS or Publisher's site
Tonkin, RS, Mao, Y, O'Carroll, SJ, Nicholson, LF, Green, CR, Gorrie, CA & Moalem-Taylor, G 2015, 'Gap junction proteins and their role in spinal cord injury.', Frontiers in Molecular Neuroscience, vol. 7, pp. 1-9.View/Download from: UTS OPUS or Publisher's site
Gap junctions are specialized intercellular communication channels that are formed by two hexameric connexin hemichannels, one provided by each of the two adjacent cells. Gap junctions and hemichannels play an important role in regulating cellular metabolism, signaling, and functions in both normal and pathological conditions. Following spinal cord injury (SCI), there is damage and disturbance to the neuronal elements of the spinal cord including severing of axon tracts and rapid cell death. The initial mechanical disruption is followed by multiple secondary cascades that cause further tissue loss and dysfunction. Recent studies have implicated connexin proteins as playing a critical role in the secondary phase of SCI by propagating death signals through extensive glial networks. In this review, we bring together past and current studies to outline the distribution, changes and roles of various connexins found in neurons and glial cells, before and in response to SCI. We discuss the contribution of pathologically activated connexin proteins, in particular connexin 43, to functional recovery and neuropathic pain, as well as providing an update on potential connexin specific pharmacological agents to treat SCI.