Functional and histopathological changes induced by intraparenchymal injection of kainic acid in the rat cervical spinal cord

The role of astrocytes response triggered by hyperglycaemia during spinal cord injury

Objective: This manuscript aimed to provide a comprehensive overview of the physiological, molecular, and cellular mechanisms triggered by reactive astrocytes (RA) in the context of spinal cord injury (SCI), with a particular focus on cases involving hyperglycaemia.Methods: The compilation of articles related to astrocyte responses in neuropathological conditions, with a specific emphasis on those related to SCI and hyperglycaemia, was conducted by searching through databases including Science Direct, Web of Science, and PubMed.Results and Conclusions: This article explores the dual role of astrocytes in both neurophysiological and neurodegenerative conditions within the central nervous system (CNS). In the aftermath of SCI and hyperglycaemia, astrocytes undergo a transformation into RA, adopting a distinct phenotype. While there are currently no approved therapies for SCI, various therapeutic strategies have been proposed to alleviate the detrimental effects of RAs following SCI and hyperglycemia. These strategies show promising potential in the treatment of SCI and its likely comorbidities.

Hypoxia-inducible factor prolyl hydroxylase domain (PHD) inhibition after contusive spinal cord injury does not improve locomotor recovery

Traumatic spinal cord injury (SCI) is a devastating neurological condition that involves both primary and secondary tissue loss. Various cytotoxic events including hypoxia, hemorrhage and blood lysis, bioenergetic failure, oxidative stress, endoplasmic reticulum (ER) stress, and neuroinflammation contribute to secondary injury. The HIF prolyl hydroxylase domain (PHD/EGLN) family of proteins are iron-dependent, oxygen-sensing enzymes that regulate the stability of hypoxia inducible factor-1α (HIF-1α) and also mediate oxidative stress caused by free iron liberated from the lysis of blood. PHD inhibition improves outcome after experimental intracerebral hemorrhage (ICH) by reducing activating transcription factor 4 (ATF4)-driven neuronal death. As the ATF4-CHOP (CCAAT-enhancer-binding protein homologous protein) pathway plays a role in the pathogenesis of contusive SCI, we examined the effects of PHD inhibition in a mouse model of moderate T9 contusive SCI in which white matter damage is the primary driver of locomotor dysfunction. Pharmacological inhibition of PHDs using adaptaquin (AQ) moderately lowers acute induction of Atf4 and Chop mRNAs and prevents the acute decline of oligodendrocyte (OL) lineage mRNAs, but does not improve long-term recovery of hindlimb locomotion or increase chronic white matter sparing. Conditional genetic ablation of all three PHD isoenzymes in OLs did not affect Atf4, Chop or OL mRNAs expression levels, locomotor recovery, and white matter sparing after SCI. Hence, PHDs may not be suitable targets to improve outcomes in traumatic CNS pathologies that involve acute white matter injury.

Intracerebroventricular Delivery of Human Umbilical Cord Mesenchymal Stem Cells as a Promising Therapy for Repairing the Spinal Cord Injury Induced by Kainic Acid

Spinal cord injury (SCI) is a common pathological condition that leads to permanent or temporal loss of motor and autonomic functions. Kainic acid (KA), an agonist of kainate receptors, a type of ionotropic glutamate receptor, is widely used to induce experimental neurodegeneration models of CNS. Mesenchymal Stem Cells (MSC) therapy applied at the injured nervous tissue have emerged as a promising therapeutic treatment. Here we used a validated SCI experimental model in which an intraparenchymal injection of KA into the C5 segment of rat spinal cord induced an excitotoxic lesion. Three days later, experimental animals were treated with an intracerebroventricular injection of human umbilical cord (hUC) MSC whereas control group only received saline solution. Sensory and motor skills as well as neuronal and glial reaction of both groups were recorded. Differences in motor behavior, neuronal counting and glial responses were observed between hUC-MSC-treated and untreated rats. According to the obtained results, we suggest that hUC-MSC therapy delivered into the fourth ventricle using the intracerebroventricular via can exert a neuroprotective or neurorestorative effect on KA-injected animals.

Intracisternal IGF-1 gene therapy abrogates kainic acid-induced excitotoxic damage of the rat spinal cord

Development of alternative therapies for treating functional deficits after different neurological damages is a challenge in neuroscience. Insulin-like growth factor-1 (IGF-1) is a potent neurotrophic factor exerting neuroprotective actions in brain and spinal cord. It is used to prevent or treat injuries of the central nervous system using different administration routes in different animal models. In this study, we evaluated whether intracisternal (IC) route for IGF-1 gene therapy may abrogate or at least reduce the structural and behavioral damages induced by the intraparenchymal injection of kainic acid (KA) into the rat spinal cord. Experimental (Rad-IGF-1) and control (Rad-DsRed-KA) rats were evaluated using a battery of motor and sensory tests before the injection of the recombinant adenovector (day -3), before KA injection (day 0) and at every post-injection (pi) time point (days 1, 2, 3 and 7 pi). Histopathological changes and neuronal and glial counting were assessed. Pretreatment using IC delivery of RAd-IGF-1 improved animal's general condition and motor and sensory functions as compared to Rad-DsRed-KA-injected rats. Besides, IC Rad-IGF-1 therapy abrogated later spinal cord damage and reduced the glial response induced by KA as observed in Rad-DsRed-KA rats. We conclude that the IC route for delivering RAd-IGF-1 prevents KA-induced excitotoxicity in the spinal cord.

Effects of estrogen on Survival and Neuronal Differentiation of adult human olfactory bulb neural stem Cells Transplanted into Spinal Cord Injured Rats.. [DOI: 10.1101/571950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

In the present study we developed an excitotoxic spinal cord injury (SCI) model using kainic acid (KA) to evaluate of the therapeutic potential of human olfactory bulb neural stem cells (h-OBNSCs) for spinal cord injury (SCI). In a previous study, we assessed the therapeutic potential of these cells for SCI; all transplanted animals showed successful engraftment. These cells differentiated predominantly as astrocytes, not motor neurons, so no improvement in motor functions was detected. In the current study we used estrogen as neuroprotective therapy before transplantation of OBNSCs to preserve some of endogenous neurons and enhance the differentiation of these cells towards neurons. The present work demonstrated that the h-GFP-OBNSCs were able to survive for more than eight weeks after sub-acute transplantation into injured spinal cord. Stereological quantification of OBNSCs showed approximately a 2.38-fold increase in the initial cell population transplanted. 40.91% of OBNSCs showed differentiation along the neuronal lineages, which was the predominant fate of these cells. 36.36% of the cells differentiated into mature astrocytes; meanwhile 22.73% of the cells differentiated into oligodendrocytes. Improvement in motor functions was also detected after cell transplantation.

Reactivity of microglia and astrocytes after an excitotoxic injury induced by kainic acid in the rat spinal cord

After injury of the nervous system glial cells react according to the stimuli by modifying their morphology and function. Glia activation was reported in different kainic acid (KA)-induced neurodegeneration models. Here, we describe glial morphometric changes occurring in an excitotoxic KA-induced cervical spinal cord injury model. Concomitant degenerative and apoptotic processes are also reported. Male rats injected at the spinal cord C5 segment either with KA or saline were euthanized at post-injection (PI) days 1, 2, 3 or 7. Anti-IBA-1 and anti-GFAP antibodies were used to identify microglia and activated astrocytes, respectively, and to morphometrically characterized them. Fluoro-Jade B staining and TUNEL reaction were used to determine neuronal and glial degeneration and apoptosis. KA-injected group showed a significant increase in microglia number at the ipsilateral side by PI day 3. Different microglia reactive phenotypes were observed. Reactive microglia was still present by PI day 7. Astrocytes in KA-injected group showed a biphasic increase in number at PI days 1 and 3. Degenerative and apoptotic events were only observed in KA-injected animals, increasing mainly by PI day 1. Understanding the compromise of glia in different neurodegenerative processes may help to define possible common or specific therapeutic approaches directed towards neurorestorative strategies.

Neurons of the rat cervical spinal cord express vimentin and neurofilament after intraparenchymal injection of kainic acid

Intermediate filaments (IF) can be altered under disorders such as neurodegenerative diseases. Kainic acid (KA) induce behavioral changes and histopathological alterations of the spinal cord of injected rats. Our goal was to evaluate the IF expression in neurons during this injury model. Animals were injected with KA at the C5 segment of the cervical spinal cord and euthanized at 1, 3 and 7 post injection (pi) days. Neuronal cell counting showed a significant loss of neurons at the injection site when compared with those of sham and non-operated animals. Immunohistochemistry for vimentin and neurofilament showed positive labeling of perikarya in sham and KA-injected animals since day 1 pi that lasted for the remaining experimental days. Colocalization analysis between enolase and vimentin or neurofilament confirmed a high index of colocalization in both experimental groups at day 1 pi. This index decreased in sham animals by day 3 pi whereas that of KA-injected animals remained high throughout the experiment. These results may suggest that perikarya initiate an unconventional IF expression, which may respond to the neuronal damage induced by the mechanical injury and the excitotoxic effect of KA. It seems that vimentin and neurofilament expression may be a necessary change to promote recovery of the damaged tissue.

Delayed application of the anesthetic propofol contrasts the neurotoxic effects of kainate on rat organotypic spinal slice cultures

Excitotoxicity due to hyperactivation of glutamate receptors is thought to underlie acute spinal injury with subsequent strong deficit in spinal network function. Devising an efficacious protocol of neuroprotection to arrest excitotoxicity might, therefore, spare a substantial number of neurons and allow later recovery. In vitro preparations of the spinal cord enable detailed measurement of spinal damage evoked by the potent glutamate analogue kainate. Any clinically-relevant neuroprotective treatment should start after the initial lesion and spare networks for at least 24h when cell damage plateaus. Using this strategy, we have observed that the gas anesthetic methoxyflurane provided strong, delayed neuroprotection. It is unclear if this beneficial effect was due to the mechanism of action by methoxyflurane, or it was the consequence of anesthetic depression. To test this hypothesis, we investigated the effect by propofol (commonly injected i.v. for general anesthesia) after kainate excitotoxicity induced on organotypic spinal slices. At 5μM concentration, propofol significantly attenuated cell death, including neuronal losses and, especially, damage to the highly vulnerable motoneurons. The action by propofol was fully prevented when co-applied with the GABAA antagonist bicuculline, indicating that neuroprotection required intact GABAA receptor function. Although bicuculline per se was not neurotoxic, it largely enhanced the lesional effects of kainate, suggesting that GABAA receptor activity could limit excitotoxicity. Our data might offer an explanation for the beneficial clinical outcome of neurosurgery performed as soon as possible after spinal lesion: we posit that general anesthesia contributes to this outcome, regardless of the type of anesthetic used.