A matrix metalloproteinase-responsive hydrogel system controls angiogenic peptide release for repair of cerebral ischemia/reperfusion injury

Vascular endothelial growth factor and its mimic peptide KLTWQELYQLKYKGI(QK)are widely used as the most potent angiogenic factors for the treatment of multiple ischemic diseases.However,conventional topical drug delivery often results in a burst release of the drug,leading to transient retention(inefficacy)and undesirable diffusion(toxicity)in vivo.Therefore,a drug delivery system that responds to changes in the microenvironment of tissue regeneration and controls vascular endothelial growth factor release is crucial to improve the treatment of ischemic stroke.Matrix metalloproteinase-2(MMP-2)is gradually upregulated after cerebral ischemia.Herein,vascular endothelial growth factor mimic peptide QK was self-assembled with MMP-2-cleaved peptide PLGLAG(TIMP)and customizable peptide amphiphilic(PA)molecules to construct nanofiber hydrogel PA-TIMP-QK.PA-TIMP-QK was found to control the delivery of QK by MMP-2 upregulation after cerebral ischemia/reperfusion and had a similar biological activity with vascular endothelial growth factor in vitro.The results indicated that PA-TIMP-QK promoted neuronal survival,restored local blood circulation,reduced blood-brain barrier permeability,and restored motor function.These findings suggest that the self-assembling nanofiber hydrogel PA-TIMP-QK may provide an intelligent drug delivery system that responds to the microenvironment and promotes regeneration and repair after cerebral ischemia/reperfusion injury.

Placenta-derived mesenchymal stem cells attenuate secondary brain injury after controlled cortical impact in rats by inhibiting matrix metalloproteinases

Background:As a form of biological therapy,placenta-derived mesenchymal stem cells(PDMSCs)exhibit considerable promise in addressing the complex pathological processes of traumaticbrain injury(TBI)due to their multi-target and multi-pathway mode of action.Material&Methods:This study investigates the protective mechanisms and benefits of PDMSCs in mitigating the effects of controlled cortical impact(CCI)in rats and glutamate-induced oxidative stress injury in HT22 cells in vitro.Our primary objective is to provide evidence supporting the clinical application of PDMSCs.Results:In the in vivo arm of our investigation,we observed a swift elevation of matrix metalloproteinase-9(MMP-9)in the proximal cortex of injured brain tissues after CCI.PDMSCs,distinguished by their heightened expression of metalloproteinase tissue inhibitors-1 and-2(TIMP-1 and TIMP-2):were intravenously administered via the caudal vein.This intervention yielded significant reductions in the permeability of the blood-brain barrier(BBB):the extent of brain edema,the levels of inflammatory cytokines IL-1βand TNF-αin damaged brain tissue,and the activation status of microglia in CCI-afflicted rats.In the realm of in vitro experiments,PDMSC-conditioned media demonstrated substantial reductions in mortality rates and cleaved caspase-3 levels in glutamate-induced HT22 cells compared with conventional media.Notably,this advantage was negated upon the introduction of neutralizing antibodies targeting TIMP-1 and TIMP-2.Conclusion:Collectively,our findings underscore the potential of PDMSCs in alleviating oxidative stress injury and secondary brain injury in the pathological process of TBI.

Time dependent integration of matrix metalloproteinases and their targeted substrates directs axonal sprouting and synaptogenesis following central nervous system injury

Over the past two decades, many investigators have reported how extracellular matrix molecules act to regulate neuroplasticity. The majority of these studies involve proteins which are targets of matrix metalloproteinases. Importantly, these enzyme/substrate interactions can regulate degenerative and regenerative phases of synaptic plasticity, directing axonal and dendritic reorganization after brain insult. The present review first summarizes literature support for the prominent role of matrix metalloproteinases during neuroregeneration, followed by a discussion of data contrasting adaptive and maladaptive neuroplasticity that reveals time-dependent metalloproteinase/substrate regulation of postinjury synaptic recovery. The potential for these enzymes to serve as therapeutic targets for enhanced neuroplasticity after brain injury is illustrated with experiments demonstrating that metalloproteinase inhibitors can alter adaptive and maladaptive outcome. Finally, the complexity of metalloproteinase role in reactive synaptogenesis is revealed in new studies showing how these enzymes interact with immune molecules to mediate cellular response in the local regenerative environment, and are regulated by novel binding partners in the brain extracellular matrix. Together, these different examples show the complexity with which metalloproteinases are integrated into the process of neuroregeneration, and point to a promising new angle for future studies exploring how to facilitate brain plasticity.

Reviving the use of inhibitors of matrix metalloproteases in spinal cord injury:a case for specificity

At present,there are no resto rative therapies in the clinic for spinal cord injury,with current treatments offering only palliative treatment options.The role of matrix metalloproteases is well established in spinal cord injury,howeve r,translation into the clinical space was plagued by early designs of matrix metalloprotease inhibitors that lacked specificity and fears of musculos keletal syndrome prevented their further development.Newe r,much more specific matrix metalloprotease inhibitors have revived the possibility of using these inhibitors in the clinic since they are much more specific to their to rget matrix metalloproteases.Here,the evidence for use of matrix metalloproteases after spinal cord injury is reviewed and researche rs are urged to overcome their old fears rega rding matrix metalloprotease inhibition and possible side effects for the field to progress.Recently published work by us shows that inhibition of specific matrix metalloproteases after spinal cord injury holds promise since four key consequences of spinal cord injury could be alleviated by specific,next-gene ration matrix metalloprotease inhibitors.For example,specific inhibition of matrix metalloprotease-9 and matrix metalloprotease-12 within 24 hours after injury and for 3 days,alleviates spinal cord injury-induced edema,blood-s pinal co rd barrier breakdown,neuro pathic pain and resto res sensory and locomotor function.Attempts are now underway to translate this therapy into the clinic.

Picroside Ⅱ down-regulates matrix metalloproteinase-9 expression following cerebral ischemia/reperfusion injury in rats

Studies have shown that Picroside Ⅱ attenuates inflammatory reactions following brain ischemia through the inhibition of the TLR-4-NF-KB signal transduction pathway, and ameliorates cerebral edema through the reduction of aquaporin-4 expression. Matrix metalloproteinase-9 （MMP-9）, located downstream of the TLR-4-NF-KB signal transduction pathway, can degrade the neurovascular matrix, damage the blood-brain barrier to induce cerebral edema, and directly result in neuronal apoptosis and brain injury, Therefore, the present study further observed MMP-9 expression in the brain tissues of rats with cerebral ischemia/reperfusion injury following Picroside Ⅱ treatment. Results demonstrated that Picroside Ⅱ significantly reduced MMP-9 expression in ischemic brain tissues, as well as neuronal apoptosis and brain infarct volume, suggesting Picroside Ⅱ exhibits neuroprotection by down-regulating MMP-9 expression and inhibiting cell apoptosis.

Matrix metalloproteinase-9 expression and blood brain barrier permeability in the rat brain after cerebral ischemia/reperfusion injury

BACKGROUND： The integrity of the blood brain barrier （BBB） plays an important role in the patho-physiological process of cerebral ischemia/reperfusion injury. It has been recently observed that metalloproteinase-9 （MMP-9） is closely related to cerebral ischemia/reperfusion injury OBJECTIVE： This study was designed to observe MMP-9 expression in the rat brain after cerebral ischemia/reperfusion injury and to investigate its correlation to BBB permeability. DESIGN, TIME AND SETTING： This study, a randomized controlled animal experiment, was performed at the Institute of Neurobiology, Central South University between September 2005 and March 2006. MATERIALS： Ninety healthy male SD rats, aged 3-4 months, weighing 200-280 g, were used in the present study. Rabbit anti-rat MMP-9 polyclonal antibody （Boster, Wuhan, China） and Evans blue （Sigma, USA） were also used. METHODS： All rats were randomly divided into 9 groups with 10 rats in each group： normal control group, sham-operated group, and ischemia for 2 hours followed by reperfusion for 3, 6, 12 hours, 1, 2, 4 and 7 days groups. In the ischemia/reperfusion groups, rats were subjected to ischemia/reperfusion injury by suture occlusion of the right middle cerebral artery. In the sham-operated group, rats were merely subjected to vessel dissociation. In the normal control group, rats were not modeled. MAIN OUTCOME MEASURES： BBB permeability was assessed by determining the level of effusion of Evans blue. MMP-9 expression was detected by an immunohistochemical method. RESULTS： All 90 rats were included in the final analysis. BBB permeability alteration was closely correlated to ischemia/reperfusion time. BBB permeability began to increase at ischemia/reperfusion for 3 hours, then it gradually reached a peak level at ischemia/reperfusion for 1 day, and thereafter it gradually decreased. MMP-9 expression began to increase at ischemia/reperfusion for 3 hours, then gradually reached its peak level 2 days after perfusion, and thereafter it gradually decreased. CONCLUSION： MMP-9 expression increases in rat brain tissue after focal cerebral ischemia/reperfusion injury, which correlates with increased permeability of the BBB.

Matrix metalloproteinase-9 in the initial injury after hepatectomy in mice

AIM:To investigate the role of matrix metalloproteinase(MMP)-9 in the pathogenesis of postoperative liver failure(PLF) after extended hepatectomy(EH).METHODS:An insufficient volume of the remnant liver(RL) results in higher morbidity and mortality,and a murine model with 80%-hepatectomy was used.All investigations were performed 6 h after EH.Mice were first divided into two groups based on the postoperative course(i.e.,the PLF caused or did not),and MMP-9 expression was measured by Western blotting.The source of MMP-9 was then determined by immunohistological stainings.Tissue inhibitor of metalloproteinase(TIMP)-1 is the endogenous inhibitor of MMP-9,and MMP-9 behavior was assessed by the experiments in wild-type,MMP-9(-/-) and TIMP-1(-/-) mice by Western blotting and gelatin zymography.The behavior of neutrophils was also assessed by immunohistological stainings.An anti-MMP-9 monoclonal antibody and a broadspectrum MMP inhibitor were used to examine the role of MMP-9.RESULTS:Symptomatic mice showed more severe PLF(histopathological assessments:2.97 ± 0.92 vs 0.11 ± 0.08,P < 0.05) and a higher expression of MMP-9(71085 ± 18274 vs 192856 ± 22263,P < 0.01).Nonnative leukocytes appeared to be the main source of MMP-9,because MMP-9 expression corresponding with CD11b positive-cell was observed in the findings of immunohistological stainings.In the histopathological findings,the PLF was improved in MMP-9(-/-) mice(1.65% ± 0.23% vs 0.65% ± 0.19%,P < 0.01) and it was worse in TIMP-1(-/-) mice(1.65% ± 0.23% vs 1.78% ± 0.31%,P < 0.01).Moreover,neutrophil migration was disturbed in MMP-9(-/-) mice in the immunohistological stainings.Two methods of MMP-9 inhibition revealed reduced PLF,and neutrophil migration was strongly disturbed in MMP-9-blocked mice in the histopathological assessments(9.6 ± 1.9 vs 4.2 ± 1.2,P < 0.05,and 9.9 ± 1.5 vs 5.7 ± 1.1,P < 0.05).CONCLUSION:MMP-9 is important for the process of PLF.The initial injury is associated with MMP-9 derived from neutrophils,and MMP-9 blockade reduces PLF.MMP-9 may be a potential target to prevent PLF after EH and to overcome an insufficient RL.

Sex-dependent alterations in extracellular vesicles linking chronic spinal cord injury to brain neuroinflammation and neurodegeneration

Traumatic spinal cord injury(SCI)is a devastating exogenous injury with long-lasting consequences and a leading cause of death and disability worldwide.Advances in assistive technology,rehabilitative interventions,and the ability to identify and intervene in secondary conditions have significantly increased the long-term survival rate of SCI patients,with some people even living well into their seventh or eighth decade.These survival changes have led neurotrauma researchers to examine how SCI interacts with brain aging.Public health and epidemiological data showed that patients with long-term SCI can have a lower life expectancy and quality of life,along with a higher risk of comorbidities and complications.

Spinal cord injury regenerative therapy development:integration of design of experiments

Spinal cord injury(SCI)can cause motor and sensory paralysis,and autonomic nervous system disorders including malfunction of urination and defecation,thereby significantly impairing the quality of life.Researchers continue to explo re new stem cell strategies for the treatment of paralysis by transpla nting human induced pluripotent stem cell-derived neural ste m/progenitor cells(hiPSCNS/PCs)into spinal cord injured tissues.

Deciphering the mechanobiology of microglia in traumatic brain injury with advanced microsystems

Advanced microsystems in traumatic brain injury research:Traumatic brain injury(TBI)results from a mechanical insult to the brain,leading to neuronal and axonal damage and subsequently causing a secondary injury.Within minutes of TBI,a neuroinflammatory response is triggered,driven by intricate molecular and cellular inflammatory processes.

Visualizing traumatic brain injury:ocular clues for diagnosis and assessment

Traumatic brain injury (TBI) is defined as damage to the brain resulting from an external sudden physical force or shock to the head.It is considered a silent public health epidemic causing significant death and disability globally.There were 64,000 TBI related deaths reported in the USA in 2020,with about US$76 billion in direct and indirect medical costs annually.

A lead role for a“secondary”axonal injury response

Stress signaling following axon injury stimulates a transcriptional program for regeneration that might be exploited to promote central nervous system repair.However,this stress response drives neuronal apoptosis in non-regenerative environments.This duality presents a quandary for the development of therapeutic interventions:manipulating stress signaling to enhance recovery of damaged neurons risks accelerating neurodegeneration or restricting regenerative potential.This dichotomy is well illustrated by the fates of retinal ganglion cells(RGCs)following optic nerve crush.In this central nervous system injury model,disruption of a stress-activated MAP kinase(MAPK)cascade blocks the extensive apoptosis of RGCs that occurs in wild-type mice(Watkins et al.,2013;Welsbie et al.,2017).

Secretome of polarized macrophages:potential for targeting inflammatory dynamics in spinal cord injury

Spinal cord injury(SCI)involves an initial traumatic phase,followed by secondary events such as ischemia,increased blood-spinal cord barrier permeability,ionic disruption,glutamate excitotoxicity,and metabolic alterations.A pe rsistent and exagge rated inflammato ry response within the spinal cord accompanies these events(Lima et al.,2022).The complexity and interplay of these mechanisms exacerbate the initial injury,leading to a degenerative process at the injury site.While the initial trauma is unavoidable,the secondary injury begins within minutes and can last for months,creating an optimal window for therapeutic intervention.

Remaking a connection:molecular players involved in post-injury synapse formation

Functional recovery from central nervous system(CNS)trauma depends not only on axon regeneration or compensatory sprouting of uninjured fibers but also on the ability of newly grown axons to establish functional synapses with appropriate targets.Although several studies have successfully promoted long-distance axonal regeneration in distinct CNS injury models,none of them have resulted in a viable therapeutic approach for patient recovery.A possible reason may be the lack of new synaptogenesis for reestablishing the circuitry lost after injury.Herein,we discuss how our understanding of the mechanisms that instruct synapse formation in the injured nervous system may contribute to the design of new strategies to promote functional restoration in traumatic CNS disorders.

New insights on the role of chondroitin sulfate proteoglycans in neural stem cell–mediated repair in spinal cord injury

Extensive neurodegeneration is a hallmark of traumatic spinal cord injury (SCI) that underlies permanent sensorimotor and autonomic impairments (Alizadeh et al.,2019).Following the primary impact,the spinal cord undergoes a cascade of secondary injury mechanisms that are driven by disruption of the blood-spinal cord ba rrier,vascula r inju ry,glial reactivity,neu roinfla mmation,oxidative stress,lipid peroxidation,and glutamate excitotoxicity that culminate in neuronal and oligodendroglial cell death,demyelination,and axonal damage(Alizadeh et al.,2019).To achieve a meaningful functional recovery after SCI,regeneration of new neurons and oligodendrocytes and their successful growth and integration within the neural network are critical steps for reconstructing the damaged spinal cord tissue (Fischer et al.,2020).

Stepping up after spinal cord injury:negotiating an obstacle during walking

Every day walking consists of frequent voluntary modifications in the gait pattern to negotiate obstacles.After spinal cord injury,stepping over an obstacle becomes challenging.Stepping over an obstacle requires sensorimotor transformations in several structures of the brain,including the parietal cortex,premotor cortex,and motor cortex.Sensory information and planning are transformed into motor commands,which are sent from the motor cortex to spinal neuronal circuits to alter limb trajectory,coordinate the limbs,and maintain balance.After spinal cord injury,bidirectional communication between the brain and spinal cord is disrupted and animals,including humans,fail to voluntarily modify limb trajectory to step over an obstacle.Therefore,in this review,we discuss the neuromechanical control of stepping over an obstacle,why it fails after spinal cord injury,and how it recovers to a certain extent.

Hypidone hydrochloride(YL-0919)ameliorates functional deficits after traumatic brain injury in mice by activating the sigma-1 receptor for antioxidation

Traumatic brain injury involves complex pathophysiological mechanisms,among which oxidative stress significantly contributes to the occurrence of secondary injury.In this study,we evaluated hypidone hydrochloride(YL-0919),a self-developed antidepressant with selective sigma-1 receptor agonist properties,and its associated mechanisms and targets in traumatic brain injury.Behavioral experiments to assess functional deficits were followed by assessment of neuronal damage through histological analyses and examination of blood-brain barrier permeability and brain edema.Next,we investigated the antioxidative effects of YL-0919 by assessing the levels of traditional markers of oxidative stress in vivo in mice and in vitro in HT22 cells.Finally,the targeted action of YL-0919 was verified by employing a sigma-1 receptor antagonist(BD-1047).Our findings demonstrated that YL-0919 markedly improved deficits in motor function and spatial cognition on day 3 post traumatic brain injury,while also decreasing neuronal mortality and reversing blood-brain barrier disruption and brain edema.Furthermore,YL-0919 effectively combated oxidative stress both in vivo and in vitro.The protective effects of YL-0919 were partially inhibited by BD-1047.These results indicated that YL-0919 relieved impairments in motor and spatial cognition by restraining oxidative stress,a neuroprotective effect that was partially reversed by the sigma-1 receptor antagonist BD-1047.YL-0919 may have potential as a new treatment for traumatic brain injury.

Complement-dependent neuroinflammation in spinal cord injury:from pathology to therapeutic implications

Spinal cord injury remains a major cause of disability in young adults,and beyond acute decompression and rehabilitation,there are no pharmacological treatments to limit the progression of injury and optimize recovery in this population.Following the thorough investigation of the complement system in triggering and propagating cerebral neuroinflammation,a similar role for complement in spinal neuroinflammation is a focus of ongoing research.In this work,we survey the current literature investigating the role of complement in spinal cord injury including the sources of complement proteins,triggers of complement activation,and role of effector functions in the pathology.We study relevant data demonstrating the different triggers of complement activation after spinal cord injury including direct binding to cellular debris,and or activation via antibody binding to damage-associated molecular patterns.Several effector functions of complement have been implicated in spinal cord injury,and we critically evaluate recent studies on the dual role of complement anaphylatoxins in spinal cord injury while emphasizing the lack of pathophysiological understanding of the role of opsonins in spinal cord injury.Following this pathophysiological review,we systematically review the different translational approaches used in preclinical models of spinal cord injury and discuss the challenges for future translation into human subjects.This review emphasizes the need for future studies to dissect the roles of different complement pathways in the pathology of spinal cord injury,to evaluate the phases of involvement of opsonins and anaphylatoxins,and to study the role of complement in white matter degeneration and regeneration using translational strategies to supplement genetic models.

Astrocytes, reactive astrogliosis, and glial scar formation in traumatic brain injury

Traumatic brain injury is a global health crisis,causing significant death and disability worldwide.Neuroinflammation that follows traumatic brain injury has serious consequences for neuronal survival and cognitive impairments,with astrocytes involved in this response.Following traumatic brain injury,astrocytes rapidly become reactive,and astrogliosis propagates from the injury core to distant brain regions.Homeostatic astroglial proteins are downregulated near the traumatic brain injury core,while pro-inflammatory astroglial genes are overexpressed.This altered gene expression is considered a pathological remodeling of astrocytes that produces serious consequences for neuronal survival and cognitive recovery.In addition,glial scar formed by reactive astrocytes is initially necessary to limit immune cell infiltration,but in the long term impedes axonal reconnection and functional recovery.Current therapeutic strategies for traumatic brain injury are focused on preventing acute complications.Statins,cannabinoids,progesterone,beta-blockers,and cerebrolysin demonstrate neuroprotective benefits but most of them have not been studied in the context of astrocytes.In this review,we discuss the cell signaling pathways activated in reactive astrocytes following traumatic brain injury and we discuss some of the potential new strategies aimed to modulate astroglial responses in traumatic brain injury,especially using cell-targeted strategies with miRNAs or lncRNA,viral vectors,and repurposed drugs.

Combinatorial therapies for spinal cord injury repair

Spinal cord injuries have profound detrimental effects on individuals, regardless of whether they are caused by trauma or non-traumatic events. The compromised regeneration of the spinal cord is primarily attributed to damaged neurons, inhibitory molecules, dysfunctional immune response, and glial scarring. Unfortunately, currently, there are no effective treatments available that can fully repair the spinal cord and improve functional outcomes. Nevertheless, numerous pre-clinical approaches have been studied for spinal cord injury recovery, including using biomaterials, cells, drugs, or technological-based strategies. Combinatorial treatments, which target various aspects of spinal cord injury pathophysiology, have been extensively tested in the last decade. These approaches aim to synergistically enhance repair processes by addressing various obstacles faced during spinal cord regeneration. Thus, this review intends to provide scientists and clinicians with an overview of pre-clinical combinatorial approaches that have been developed toward the solution of spinal cord regeneration as well as update the current knowledge about spinal cord injury pathophysiology with an emphasis on the current clinical management.