Hyaluronidase and Hyaluronan Oligosaccharides Promote Neurological Recovery after Intraventricular Hemorrhage

Comparison of the effects of submucosal hyaluronidase and dexamethasone on postoperative edema, pain, trismus, and infection following impacted third molar surgery

BACKGROUND

Limiting postoperative edema, pain, trismus, and infection is crucial for smooth healing. This prospective, controlled clinical trial investigated and compared the effectiveness of dexamethasone and hyaluronidase in relieving these complications.

METHODS

In groups Ia and IIa, 8 mg of dexamethasone and 150 IU of hyaluronidase were administered following the removal of impacted teeth, respectively. The contralateral sides (groups Ib and IIb) were determined as control groups. Edema, pain, trismus, and infection were clinically evaluated on the 1st, 2nd, 3rd, and 7th postoperative days.

RESULTS

60 patients were enrolled in the study. Hyaluronidase provided significantly more edema relief than dexamethasone on the 1st, 2nd, 3rd, and 7th postoperative days (P = 0.031, 0.002, 0.000, and 0.009, respectively). No statistical difference was found between dexamethasone and hyaluronidase in VAS and rescue analgesic intake amount values for all time points. Hyaluronidase was more effective in reducing trismus than dexamethasone on the 2nd and 3rd postoperative days (P = 0.029, 0.024, respectively). Neither of the agents significantly increased the postoperative infection rate.

CONCLUSIONS

Hyaluronidase can be selected when postoperative excessive edema and trismus are anticipated. Dexamethasone may be a cost-effective option if postoperative pain control is merely targeted.

TRIAL REGISTRATION

This trial was registered in the Clinical Trials Protocol Registration and Results System (ClinicalTrials.gov identifier number: NCT05466604) on 20/07/2022.

Integrating spatial and single-cell transcriptomics to characterize the molecular and cellular architecture of the ischemic mouse brain

Neuroinflammation is acknowledged as a pivotal pathological event after cerebral ischemia. However, there is limited knowledge of the molecular and spatial characteristics of nonneuronal cells, as well as of the interactions between cell types in the ischemic brain. Here, we used spatial transcriptomics to study the ischemic hemisphere in mice after stroke and sequenced the transcriptomes of 19,777 spots, allowing us to both visualize the transcriptional landscape within the tissue and identify gene expression profiles linked to specific histologic entities. Cell types identified by single-cell RNA sequencing confirmed and enriched the spatial annotation of ischemia-associated gene expression in the peri-infarct area of the ischemic hemisphere. Analysis of ligand-receptor interactions in cell communication revealed galectin-9 to cell-surface glycoprotein CD44 (LGALS9-CD44) as a critical signaling pathway after ischemic injury and identified microglia and macrophages as the main source of galectins after stroke. Extracellular vesicle-mediated Lgals9 delivery improved the long-term functional recovery in photothrombotic stroke mice. Knockdown of Cd44 partially reversed these therapeutic effects, inhibiting oligodendrocyte differentiation and remyelination. In summary, our study provides a detailed molecular and cellular characterization of the peri-infact area in a murine stroke model and revealed Lgals9 as potential treatment target that warrants further investigation.

Temporal characterization of hyaluronidases after peripheral nerve injury

Hyaluronic acid (HA) is ubiquitously found in biological tissues and mediates wound healing mechanisms after injury by promoting cell migration and proliferation. With the development of tissue-engineered neural therapeutics, including off-the-shelf grafts for peripheral nerve repair, HA is an attractive material for clinical use because of its various biological roles. HA-based biomaterials have been carefully engineered to elicit specific in vivo host responses, however an important design feature that should be considered in these scaffolds is endogenous degradation. Hyaluronidases (HYALs) are the complementary enzymes that are responsible for HA turnover. Although HYAL expression has been widely characterized in various tissues, including the central nervous system, and for different pathologies, there remains a lack of knowledge of HYAL mediated turnover in peripheral nerve tissue. In this work, gene expression of two hyaluronidases, HYAL1 and HYAL2, and HA-binding receptor, CD44, were studied in two injury models: rat sciatic nerve crush and critical gap transection. HYAL2 and CD44 were shown to be upregulated 3 days after crush injury, whereas HYAL1 was upregulated at 3 weeks, which collectively demonstrate temporal patterning of HA breakdown. Additionally, differences were observed between HYAL and HA expression at 3 weeks when compared for both nerve injury models. The activity of HYAL in peripheral nerve tissue was determined to be approximately 0.11 μmol/min, which could be used to further model HA-based biomaterial breakdown for peripheral nerve applications. Overall, this work provides a landscape of HA turnover in peripheral nerve that can be used for future neural applications.

The link between neuroinflammation and the neurovascular unit in synucleinopathies

The neurovascular unit (NVU) is composed of vascular cells, glial cells, and neurons. As a fundamental functional module in the central nervous system, the NVU maintains homeostasis in the microenvironment and the integrity of the blood-brain barrier. Disruption of the NVU and interactions among its components are involved in the pathophysiology of synucleinopathies, which are characterized by the pathological accumulation of α-synuclein. Neuroinflammation contributes to the pathophysiology of synucleinopathies, including Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies. This review aims to summarize the neuroinflammatory response of glial cells and vascular cells in the NVU. We also review neuroinflammation in the context of the cross-talk between glial cells and vascular cells, between glial cells and pericytes, and between microglia and astroglia. Last, we discuss how α-synuclein affects neuroinflammation and how neuroinflammation influences the aggregation and spread of α-synuclein and analyze different properties of α-synuclein in synucleinopathies.

Enzymatic Production of Low-Molecular-Weight Hyaluronan and Its Oligosaccharides: A Review and Prospects

Hyaluronic acid (HA) is a nonsulfated linear glycosaminoglycan with a negative charge. Different from the high-molecular-weight HAs, the low-molecular-weight HAs (LMW-HAs, 4-120 kDa) and hyaluronan oligosaccharides (O-HAs, <4 kDa) exhibit certain unique biological properties, owing to which these have a wide range of applications in the field of medicine. However, the chemical synthesis of high-purity LMW-HAs and O-HAs requires complex procedures, which renders this process difficult to achieve. The degradation of HA is achieved under the catalysis of hyaluronidases. In recent years, various hyaluronidase genes have been identified, and their enzymatic properties have been analyzed. In this context, the present review summarizes the hyaluronidases from different sources, which have been characterized. The review focuses on the crystal structure and the catalytic mechanism underlying the biological properties of hyaluronidases. In addition, the molecular weight distributions and the preparation approaches of the enzymatic products LMW-HAs and O-HAs are described. The general orientation of the research on hyaluronidases was speculated based on the existing literature. Accordingly, the efficient large-scale production of LMW-HAs and O-HAs using the green enzymatic approach was anticipated.

Effectiveness of Bone Marrow-Derived Platelet-Rich Fibrin on Rotator Cuff Healing in a Rabbit Degenerative Model

BACKGROUND

Platelet-rich fibrin (PRF) is a second-generation platelet concentrate. Although peripheral blood-derived PRF (P-PRF) is commonly applied in biological augmentation, there is no report about the therapeutic effect of bone marrow-derived PRF (BM-PRF) for degenerative rotator cuff tears (RCTs).

PURPOSE/HYPOTHESIS

To examine the effects of platelet-rich plasma (PRP), P-PRF, and BM-PRF during rotator cuff repair (RCR) in degenerative RCTs in rabbits. We hypothesized that BM-PRF would accelerate the bone-tendon healing after RCR.

STUDY DESIGN

Controlled laboratory study.

METHODS

Degenerative RCT models were created 2 weeks before beginning the study, and 68 juvenile rabbits were divided into 4 groups: the control, PRP, P-PRF, and BM-PRF groups. RCR without augmentation was done in the control group. PRP was prepared by centrifuging peripheral blood twice using a plastic tube. P-PRF and BM-PRF were prepared by centrifuging peripheral blood and bone marrow, respectively, using a glass tube. Rabbits from PRP, P-PRF, and BM-PRF groups were administered the augmentation in a similar fashion for RCR, between the rotator cuff and the footprint of the humerus. At 4, 8, and 12 weeks, rabbits were euthanized and histologically assessed using hematoxylin and eosin staining, Alcian blue staining, and immunohistochemical staining for type I and III collagen. The sections were also evaluated with immunofluorescence staining of vascular endothelial growth factor (VEGF) at 4 weeks.

RESULTS

The continuity was significantly better in the BM-PRF group at 4 weeks (P < .05). Immunofluorescence staining demonstrated that VEGF-positive stained cells were significantly greater in the BM-PRF group than in the control group (P < .01). The modified tendon maturing score was significantly greater in the BM-PRF group than in the control and PRP groups at 12 weeks (P < .05). There was no significant difference in the modified tendon maturing score of the P-PRF group compared with the control group.

CONCLUSION

The rabbit model of degenerative RCTs demonstrated that RCR combined with BM-PRF enhanced tendon-bone continuity and increased the VEGF-positive cells at 4 weeks and obtained preferable tendon-bone maturation at 12 weeks.

CLINICAL RELEVANCE

RCR augmented with BM-PRF has the potential to improve clinical outcomes for RCTs.

Pericyte dynamics in the mouse germinal matrix angiogenesis

Germinal matrix-intraventricular hemorrhage (GM-IVH) is the most devastating neurological complication in premature infants. GM-IVH usually begins in the GM, a highly vascularized region of the developing brain where glial and neuronal precursors reside underneath the lateral ventricular ependyma. Previous studies using human fetal tissue have suggested increased angiogenesis and paucity of pericytes as key factors contributing to GM-IVH pathogenesis. Yet, despite its relevance, the mechanisms underlying the GM vasculature's susceptibility to hemorrhage remain poorly understood. To gain better understanding on the vascular dynamics of the GM, we performed a comprehensive analysis of the mouse GM vascular endothelium and pericytes during development. We hypothesize that vascular development of the mouse GM will provide a good model for studies of human GM vascularization and provide insights into the role of pericytes in GM-IVH pathogenesis. Our findings show that the mouse GM presents significantly greater vascular area and vascular branching compared to the developing cortex (CTX). Analysis of pericyte coverage showed abundance in PDGFRβ-positive and NG2-positive pericyte coverage in the GM similar to the developing CTX. However, we found a paucity in Desmin-positive pericyte coverage of the GM vasculature. Our results underscore the highly angiogenic nature of the GM and reveal that pericytes in the developing mouse GM exhibit distinct phenotypical and likely functional characteristics compared to other brain regions which might contribute to the high susceptibility of the GM vasculature to hemorrhage.

Pharmacological Neuroprotection of the Preterm Brain: Current Evidence and Perspectives

Despite improvements in viability, the long-term neurodevelopmental outcomes of preterm babies remain serious concern as a significant percentage of these infants develop neurological and/or intellectual impairment, and they are also at increased risk of psychiatric illnesses later in life. The current challenge is to develop neuroprotective approaches to improve adverse outcomes in preterm survivors. The purpose of this review was to provide an overview of the current evidence on pharmacological agents targeting the neuroprotection of the preterm brain. Among them, magnesium sulfate, given antenatally to pregnant women with imminent preterm birth before 30 to 34 weeks of gestation, as well as caffeine administered to preterm infants after birth, exhibited neuroprotective effects for human preterm brain. Erythropoietin treatment of preterm infants did not result in neuroprotection at 2 years of age in two out of three published large randomized controlled trials; however, long-term follow-up of these infants is needed to come to definite conclusions. Further studies are also required to assess whether melatonin, neurosteroids, inhaled nitric oxide, allopurinol, or dietary supplements (omega-3 fatty acids, choline, curcumin, etc.) could be implemented as neuroprotectants in clinical practice. Furthermore, other pharmacological agents showing promising signs of neuroprotective efficacy in preclinical studies (growth factors, hyaluronidase inhibitors or treatment, antidiabetic drugs, cannabidiol, histamine-H3 receptor antagonists, etc.), as well as stem cell- or exosomal-based therapies and nanomedicine, may prove useful in the future as potential neuroprotective approaches for human preterm brain. KEY POINTS: · Magnesium and caffeine have neuroprotective effects for the preterm brain.. · Follow-up of infants treated with erythropoietin is needed.. · Neuroprotective efficacy of several drugs in animals needs to be shown in humans..

Recovery of the brain after intraventricular hemorrhage

Intraventricular hemorrhage (IVH) remains a major complication of prematurity, worldwide. The severity of IVH is variable, ranging from a tiny germinal matrix bleed to a moderate-to-large ventricular hemorrhage or periventricular hemorrhagic infarction. Survivors with IVH often suffer from hydrocephalus and white matter injury. There is no tangible treatment to prevent post-hemorrhagic cerebral palsy, cognitive deficits, or hydrocephalus in these infants. White matter injury is attributed to blood-induced damage to axons and maturing oligodendrocyte precursors, resulting in reduced myelination and axonal loss. Hydrocephalus results from obstructed CSF circulation by blood clots, increased CSF production, and reduced CSF absorption by lymphatics and arachnoid villi. Several strategies to promote neurological recovery have shown promise in animal models, including the elimination of blood and blood products, alleviating cerebral inflammation and oxidative stress, as well as promoting survival and maturation of oligodendrocyte precursors. The present review integrates novel mechanisms of brain injury in IVH and the imminent therapies to alleviate post-hemorrhagic white matter injury and hydrocephalus in the survivors with IVH.

The anti-inflammatory activity of specific-sized hyaluronic acid oligosaccharides

Severe acute inflammatory conditions may cause tissue damage, sepsis, and death. As a critical component of the extracellular matrix, hyaluronic acid (HA) has been reported to possess pro- and anti-inflammatory properties via Toll-like receptors (TLRs). In this study, we prepared different sizes and structures of HA oligosaccharides and derivatives and investigated the effects on inflammation in vitro and in vivo. Our results showed that HA tetra-saccharide was the minimum fragment to enhance inflammation, whereas HA disaccharide competitively blocked TLR4-dependent inflammation. The enzymatic HA disaccharide (ΔHA2) inhibited lipopolysaccharide (LPS)-induced inflammation. Based on structure-activity relationship analysis, we observed that anti-inflammatory activity depended on HAs polymerization degree, acetyl group, and configuration. In addition, we demonstrated that ΔHA2 reduced LPS-induced pro-inflammatory cytokines production in vivo. ΔHA2, a native metabolite of HA polysaccharides, may have a potential role against LPS-mediated inflammatory diseases.

Severe intraventricular hemorrhage causes long-lasting structural damage in a preterm rabbit pup model

BACKGROUND

Intraventricular hemorrhage causes significant lifelong mortality and morbidity, especially in preterm born infants. Progress in finding an effective therapy is stymied by a lack of preterm animal models with long-term follow-up. This study addresses this unmet need, using an established model of preterm rabbit IVH and analyzing outcomes out to 1 month of age.

METHODS

Rabbit pups were delivered preterm and administered intraperitoneal injection of glycerol at 3 h of life and approximately 58% developed IVH. Neurobehavioral assessment was performed at 1 month of age followed by immunohistochemical labeling of epitopes for neurons, synapses, myelination, and interneurons, analyzed by means of digital quantitation and assessed via two-way ANOVA or Student's t test.

RESULTS

IVH pups had globally reduced myelin content, an aberrant cortical myelination microstructure, and thinner upper cortical layers (I-III). We also observed a lower number of parvalbumin (PV)-positive interneurons in deeper cortical layers (IV-VI) in IVH animals and reduced numbers of neurons, synapses, and microglia. However, there were no discernable changes in behaviors.

CONCLUSIONS

We have established in this preterm pup model that long-term changes after IVH include significant wide-ranging alterations to cortical organization and microstructure. Further work to improve the sensitivity of neurocognitive testing in this species at this age may be required.

IMPACT

This study uses an established animal model of preterm birth, in which the rabbit pups are truly born preterm, with reduced organ maturation and deprivation of maternally supplied trophic factors. This is the first study in preterm rabbits that explores the impacts of severe intraventricular hemorrhage beyond 14 days, out to 1 month of age. Our finding of persisting but subtle global changes including brain white and gray matter will have impact on our understanding of the best path for therapy design and interventions.

Matters of size: Roles of hyaluronan in CNS aging and disease

Involvement of extracellular matrix (ECM) components in aging and age-related neurodegeneration is not well understood. The role of hyaluronan (HA), a major extracellular matrix glycosaminoglycan, in malignancy and inflammation is gaining new understanding. In particular, the differential biological effects of high molecular weight (HMW-HA) and low molecular weight hyaluronan (LMW-HA), and the mechanism behind such differences are being uncovered. Tightly regulated in the brain, HA can have diverse effects on cellular development, growth and degeneration. In this review, we summarize the homeostasis and signaling of HA in healthy tissue, discuss its distribution and ontogeny in the central nervous system (CNS), summarize evidence for its involvement in age-related neurodegeneration and Alzheimer Disease (AD), and assess the potential of HA as a therapeutic target in the CNS.

Cloning, expression, and characterization of a glycosaminoglycan lyase from Vibrio sp. H240

Glycosaminoglycan lyase is an effective tool for the functional studies of glycosaminoglycans and for the preparation of oligosaccharides. In this study, a new glycosaminoglycan lyase HCLaseV with a molecular weight of 90 kDa was cloned, expressed, and characterized from Vibrio sp. H240. The lyase belonged to the polysaccharide lyase (PL)- 8 family. HCLaseV showed enzyme activities toward chondroitin sulfate A, chondroitin sulfate B, chondroitin sulfate C, and hyaluronic acid. HCLaseV exhibited the highest activity against HA at pH 7.0 and 40 °C. HCLaseV was an endo-type enzyme whose degradation end-product was unsaturated disaccharides. Ca²⁺ inhibited the activity of HCLaseV to a certain extent, which was different from most of the enzymes in the PL-8 family. Mutagenesis studies showed that the Ca²⁺ inhibition might be related to the Asn²⁴⁴ residue. The sequence homology was evaluated by mutagenesis studies, and the catalytic residues in HCLaseV were presumed to be His²⁷⁸, Trp⁴⁸⁵, and Tyr²⁸⁷. These characteristics are helpful for further basic research and application.

Modulation of hyaluronan signaling as a therapeutic target in human disease

The extracellular matrix is an active participant, modulator and mediator of the cell, tissue, organ and organismal response to injury. Recent research has highlighted the role of hyaluronan, an abundant glycosaminoglycan constituent of the extracellular matrix, in many fundamental biological processes underpinning homeostasis and disease development. From this basis, emerging studies have demonstrated the therapeutic potential of strategies which target hyaluronan synthesis, biology and signaling, with significant promise as therapeutics for a variety of inflammatory and immune diseases. This review summarizes the state of the art in this field and discusses challenges and opportunities in what could emerge as a new class of therapeutic agents, that we term "matrix biologics".

White matter injury in infants with intraventricular haemorrhage: mechanisms and therapies

Intraventricular haemorrhage (IVH) continues to be a major complication of prematurity that can result in cerebral palsy and cognitive impairment in survivors. No optimal therapy exists to prevent IVH or to treat its consequences. IVH varies in severity and can present as a bleed confined to the germinal matrix, small-to-large IVH or periventricular haemorrhagic infarction. Moderate-to-severe haemorrhage dilates the ventricle and damages the periventricular white matter. This white matter injury results from a constellation of blood-induced pathological reactions, including oxidative stress, glutamate excitotoxicity, inflammation, perturbed signalling pathways and remodelling of the extracellular matrix. Potential therapies for IVH are currently undergoing investigation in preclinical models and evidence from clinical trials suggests that stem cell treatment and/or endoscopic removal of clots from the cerebral ventricles could transform the outcome of infants with IVH. This Review presents an integrated view of new insights into the mechanisms underlying white matter injury in premature infants with IVH and highlights the importance of early detection of disability and immediate intervention in optimizing the outcomes of IVH survivors.

Germinal Matrix-Intraventricular Hemorrhage of the Preterm Newborn and Preclinical Models: Inflammatory Considerations

The germinal matrix-intraventricular hemorrhage (GM-IVH) is one of the most important complications of the preterm newborn. Since these children are born at a critical time in brain development, they can develop short and long term neurological, sensory, cognitive and motor disabilities depending on the severity of the GM-IVH. In addition, hemorrhage triggers a microglia-mediated inflammatory response that damages the tissue adjacent to the injury. Nevertheless, a neuroprotective and neuroreparative role of the microglia has also been described, suggesting that neonatal microglia may have unique functions. While the implication of the inflammatory process in GM-IVH is well established, the difficulty to access a very delicate population has lead to the development of animal models that resemble the pathological features of GM-IVH. Genetically modified models and lesions induced by local administration of glycerol, collagenase or blood have been used to study associated inflammatory mechanisms as well as therapeutic targets. In the present study we review the GM-IVH complications, with special interest in inflammatory response and the role of microglia, both in patients and animal models, and we analyze specific proteins and cytokines that are currently under study as feasible predictors of GM-IVH evolution and prognosis.

Softening of the chronic hemi-section spinal cord injury scar parallels dysregulation of cellular and extracellular matrix content

Regeneration following spinal cord injury (SCI) is challenging in part due to the modified tissue composition and organization of the resulting glial and fibrotic scar regions. Inhibitory cell types and biochemical cues present in the scar have received attention as therapeutic targets to promote regeneration. However, altered Young's modulus of the scar as a readout for potential impeding factors for regeneration are not as well-defined, especially in vivo. Although the decreased Young's modulus of surrounding tissue at acute stages post-injury is known, the causation and outcomes at chronic time points remain largely understudied and controversial, which motivates this work. This study assessed the glial and fibrotic scar tissue's Young's modulus and composition (scar morphometry, cell identity, extracellular matrix (ECM) makeup) that contribute to the tissue's stiffness. The spatial Young's modulus of a chronic (~18-wks, post-injury) hemi-section, including the glial and fibrotic regions, were significantly less than naïve tissue (~200 Pa; p < 0.0001). The chronic scar contained cystic cavities dispersed in areas of dense nuclei packing. Abundant CNS cell types such as astrocytes, oligodendrocytes, and neurons were dysregulated in the scar, while epithelial markers such as vimentin were upregulated. The key ECM components in the CNS, namely sulfated proteoglycans (sPGs), were significantly downregulated following injury with concomitant upregulation of unsulfated glycosaminoglycans (GAGs) and hyaluronic acid (HA), likely altering the foundational ECM network that contributes to tissue stiffness. Our results reveal the Young's modulus of the chronic SCI scar as well as quantification of contributing elastic components that can provide a foundation for future study into their role in tissue repair and regeneration.

Diverse Roles for Hyaluronan and Hyaluronan Receptors in the Developing and Adult Nervous System

Hyaluronic acid (HA) plays a vital role in the extracellular matrix of neural tissues. Originally thought to hydrate tissues and provide mechanical support, it is now clear that HA is also a complex signaling molecule that can regulate cell processes in the developing and adult nervous systems. Signaling properties are determined by molecular weight, bound proteins, and signal transduction through specific receptors. HA signaling regulates processes such as proliferation, differentiation, migration, and process extension in a variety of cell types including neural stem cells, neurons, astrocytes, microglia, and oligodendrocyte progenitors. The synthesis and catabolism of HA and the expression of HA receptors are altered in disease and influence neuroinflammation and disease pathogenesis. This review discusses the roles of HA, its synthesis and breakdown, as well as receptor expression in neurodevelopment, nervous system function and disease.

Intraventricular Hemorrhage and White Matter Injury in Preclinical and Clinical Studies

Germinal matrix-intraventricular hemorrhage (IVH) occurs in nearly half of infants born at less than 26 weeks' gestation. Up to 50% of survivors with IVH develop cerebral palsy, cognitive deficits, behavioral disorders, posthemorrhagic ventricular dilatation, or a combination of these sequelae. After the initial bleeding and the primary brain injury, inflammation and secondary brain injury might lead to periventricular leukomalacia or diffuse white matter injury. Potential factors that are involved include microglia and astrocyte activation, degradation of blood components with release of "toxic" products, infiltration of the brain by systemic immune cells, death of neuronal and glial cells, and arrest of preoligodendrocyte maturation. In addition, impairment of the blood-brain barrier may play a major role in the pathophysiology. A wide range of animal models has been used to explore causes and mechanisms leading to IVH-induced brain injury. Preclinical studies have identified potential targets for enhancing brain repair. However, little has been elucidated about the effectiveness of potential interventions in clinical studies. A systematic review of available preclinical and clinical studies might help identify research gaps and which types of interventions may be prioritized. Future trials should report clinically robust and long-term outcomes after IVH.

GSK3β Inhibition Restores Impaired Neurogenesis in Preterm Neonates With Intraventricular Hemorrhage

Intraventricular hemorrhage (IVH) is a common complication of prematurity in infants born at 23-28 weeks of gestation. Survivors exhibit impaired growth of the cerebral cortex and neurodevelopmental sequeale, but the underlying mechanism(s) are obscure. Previously, we have shown that neocortical neurogenesis continues until at least 28 gestational weeks. This renders the prematurely born infants vulnerable to impaired neurogenesis. Here, we hypothesized that neurogenesis is impaired by IVH, and that signaling through GSK3β, a critical intracellular kinase regulated by Wnt and other pathways, mediates this effect. These hypotheses were tested observationally in autopsy specimens from premature infants, and experimentally in a premature rabbit IVH model. Significantly, in premature infants with IVH, the number of neurogenic cortical progenitor cells was reduced compared with infants without IVH, indicating acutely decreased neurogenesis. This finding was corroborated in the rabbit IVH model, which further demonstrated reduction of upper layer cortical neurons after longer survival. Both the acute reduction of neurogenic progenitors, and the subsequent decrease of upper layer neurons, were rescued by treatment with AR-A014418, a specific inhibitor of GSK3β. Together, these results indicate that IVH impairs late stages of cortical neurogenesis, and suggest that treatment with GSK3β inhibitors may enhance neurodevelopment in premature infants with IVH.

Cardiac mesenchymal cells from failing and nonfailing hearts limit ventricular dilation when administered late after infarction

Although cell therapy-mediated cardiac repair offers promise for treatment/management of heart failure, lack of fundamental understanding of how cell therapy works limits its translational potential. In particular, whether reparative cells from failing hearts differ from cells derived from nonfailing hearts remains unexplored. Here, we assessed differences between cardiac mesenchymal cells (CMC) derived from failing (HF) versus nonfailing (Sham) hearts and whether the source of donor cells (i.e., from HF vs. Sham) limits reparative capacity, particularly when administered late after infarction. To determine the impact of the donor source of CMCs, we characterized the transcriptional profile of CMCs isolated from sham (Sham-CMC) and failing (HF-CMC) hearts. RNA-seq analysis revealed unique transcriptional signatures in Sham-CMC and HF-CMC, suggesting that the donor source impacts CMC. To determine whether the donor source affects reparative potential, C57BL6/J female mice were subjected to 60 min of regional myocardial ischemia and then reperfused for 35 days. In a randomized, controlled, and blinded fashion, vehicle, HF-CMC, or Sham-CMC were injected into the lumen of the left ventricle at 35 days post-MI. An additional 5 weeks later, cardiac function was assessed by echocardiography, which indicated that delayed administration of Sham-CMC and HF-CMC attenuated ventricular dilation. We also determined whether Sham-CMC and HF-CMC treatments affected ventricular histopathology. Our data indicate that the donor source (nonfailing vs. failing hearts) affects certain aspects of CMC, and these insights may have implications for future studies. Our data indicate that delayed administration of CMC limits ventricular dilation and that the source of CMC may influence their reparative actions.NEW & NOTEWORTHY Most preclinical studies have used only cells from healthy, nonfailing hearts. Whether donor condition (i.e., heart failure) impacts cells used for cell therapy is not known. We directly tested whether donor condition impacted the reparative effects of cardiac mesenchymal cells in a chronic model of myocardial infarction. Although cells from failing hearts differed in multiple aspects, they retained the potential to limit ventricular remodeling.

Regulation of Oligodendrocyte Functions: Targeting Lipid Metabolism and Extracellular Matrix for Myelin Repair

: Myelin is an essential structure that protects axons, provides metabolic support to neurons and allows fast nerve transmission. Several neurological diseases, such as multiple sclerosis, are characterized by myelin damage, which is responsible of severe functional impairment. Myelin repair requires the timely recruitment of adult oligodendrocyte precursor cells (OPCs) at the lesion sites, their differentiation and maturation into myelinating oligodendrocytes. As a consequence, OPCs undergo profound changes in their morphology, functions, and interactions with other cells and extracellular environment, thus requiring the reorganization of both their lipid metabolism and their membrane composition, which is substantially different compared to other plasma membranes. Despite the growing knowledge in oligodendroglia biology and in the mechanisms involved in OPC-mediated regeneration, the identification of strategies to promote remyelination still remains a challenge. Here, we describe how altered lipid metabolism in oligodendrocytes influences the pathogenesis of demyelination, and we show that several FDA-approved drugs with a previously unknown remyelination potential do act on cholesterol and lipid biosynthetic pathways. Since the interplay between myelin lipids and axons is strictly coordinated by the extracellular matrix (ECM), we also discuss the role of different ECM components, and report the last findings on new ECM-modifiers able to foster endogenous remyelination.

Extracellular Superoxide Dismutase Regulates Early Vascular Hyaluronan Remodeling in Hypoxic Pulmonary Hypertension

Chronic hypoxia leads to pathologic remodeling of the pulmonary vasculature and pulmonary hypertension (PH). The antioxidant enzyme extracellular superoxide dismutase (SOD3) protects against hypoxia-induced PH. Hyaluronan (HA), a ubiquitous glycosaminoglycan of the lung extracellular matrix, is rapidly recycled at sites of vessel injury and repair. We investigated the hypothesis that SOD3 preserves HA homeostasis by inhibiting oxidative and enzymatic hyaluronidase-mediated HA breakdown. In SOD3-deficient mice, hypoxia increased lung hyaluronidase expression and activity, hyaluronan fragmentation, and effacement of HA from the vessel wall of small pulmonary arteries. Hyaluronan fragmentation corresponded to hypoxic induction of the cell surface hyaluronidase-2 (Hyal2), which was localized in the vascular media. Human pulmonary artery smooth muscle cells (HPASMCs) demonstrated hypoxic induction of Hyal2 and SOD-suppressible hyaluronidase activity, congruent to our observations in vivo. Fragmentation of homeostatic high molecular weight HA promoted HPASMC proliferation in vitro, whereas pharmacologic inhibition of hyaluronidase activity prevented hypoxia- and oxidant-induced proliferation. Hypoxia initiates SOD3-dependent alterations in the structure and regulation of hyaluronan in the pulmonary vascular extracellular matrix. These changes occurred soon after hypoxia exposure, prior to appearance of PH, and may contribute to the early pathogenesis of this disease.

The extracellular matrix of the blood-brain barrier: structural and functional roles in health, aging, and Alzheimer's disease

There is increasing interest in defining the location, content, and role of extracellular matrix (ECM) components in brain structure and function during development, aging, injury, and neurodegeneration. Studies in vivo confirm brain ECM has a dynamic composition with constitutive and induced alterations that impact subsequent cell-cell and cell-matrix interactions. Moreover, it is clear that for any given ECM component, the brain region, and cell type within that location, determines the direction, magnitude, and composition of those changes. This review will examine the ECM at the neurovascular unit (NVU) and the blood-brain barrier (BBB) within the NVU. The discussion will begin at the glycocalyx ECM on the luminal surface of the vasculature, and progress to the abluminal side with a focus on changes in basement membrane ECM during aging and neurodegeneration.

Hyaluronan synthesis supports glutamate transporter activity

Hyaluronan is synthesized, secreted, and anchored by hyaluronan synthases (HAS) at the plasma membrane and comprises the backbone of perineuronal nets around neuronal soma and dendrites. However, the molecular targets of hyaluronan to regulate synaptic transmission in the central nervous system have not been fully identified. Here, we report that hyaluronan is a negative regulator of excitatory signals. At excitatory synapses, glutamate is removed by glutamate transporters to turn off the signal and prevent excitotoxicity. Hyaluronan synthesized by HAS supports the activity of glial glutamate transporter 1 (GLT1). GLT1 also retracted from cellular processes of cultured astrocytes after hyaluronidase treatment and hyaluronan synthesis inhibition. A serial knockout study showed that all three HAS subtypes recruit GLT1 to cellular processes. Furthermore, hyaluronidase treatment activated neurons in a dissociated rat hippocampal culture and caused neuronal damage due to excitotoxicity. Our findings reveal that hyaluronan helps to turn off excitatory signals by supporting glutamate clearance. Cover Image for this issue: doi: 10.1111/jnc.14516.

Preterm brain injury: Germinal matrix-intraventricular hemorrhage and post-hemorrhagic ventricular dilatation

Germinal matrix hemorrhage and intraventricular hemorrhages (GMH-IVH) remain a common and clinically significant problem in preterm infants, particularly extremely preterm infants. A large GMH-IVH is often complicated by posthemorrhagic ventricular dilation (PHVD) or parenchymal hemorrhagic infarction and is associated with an increased risk of adverse neurologic sequelae. The widespread use of cranial ultrasonography since the early 1980s has shown a gradual decrease in the incidence of GMH-IVH and has helped with the identification of antenatal and perinatal risk factors and timing of the lesion. The increased use of magnetic resonance imaging (MRI) has contributed to more detailed visualization of the site and extent of the GMH-IVH. In addition, MRI has contributed to the awareness of associated white matter changes as well as associated cerebellar hemorrhages. Although GMH-IVH and PHVD still cannot be prevented, cerebrospinal fluid drainage initiated in the early stage of PHVD development seems to be associated with a better neurodevelopmental outcome. Further studies are underway to improve treatment strategies for PHVD and to potentially prevent and repair GMH-IVH and PHVD and associated brain injury. This chapter discusses the pathogenesis, incidence, risk factors, and management, including preventive measures, of GHM-IVH and PHVD.

Challenges for intraventricular hemorrhage research and emerging therapeutic targets

INTRODUCTION

Intraventricular hemorrhage (IVH) affects both premature infants and adults. In both demographics, it has high mortality and morbidity. There is no FDA approved therapy that improves neurological outcome in either population highlighting the need for additional focus on therapeutic targets and treatments emerging from preclinical studies. Areas covered: IVH induces both initial injury linked to the physical effects of the blood (mass effect) and secondary injury linked to the brain response to the hemorrhage. Preclinical studies have identified multiple secondary injury mechanisms following IVH, and particularly the role of blood components (e.g. hemoglobin, iron, thrombin). This review, with an emphasis on pre-clinical IVH research, highlights therapeutic targets and treatments that may be of use in prevention, acute care, or repair of damage. Expert opinion: An IVH is a potentially devastating event. Progress has been made in elucidating injury mechanisms, but this has still to translate to the clinic. Some pathways involved in injury also have beneficial effects (coagulation cascade/inflammation). A greater understanding of the downstream pathways involved in those pathways may allow therapeutic development. Iron chelation (deferoxamine) is in clinical trial for intracerebral hemorrhage and preclinical data suggest it may be a potential treatment for IVH.

White matter damage after traumatic brain injury: A role for damage associated molecular patterns

Traumatic brain injury (TBI) is a leading cause of mortality and long-term morbidity worldwide. Despite decades of pre-clinical investigation, therapeutic strategies focused on acute neuroprotection failed to improve TBI outcomes. This lack of translational success has necessitated a reassessment of the optimal targets for intervention, including a heightened focus on secondary injury mechanisms. Chronic immune activation correlates with progressive neurodegeneration for decades after TBI; however, significant challenges remain in functionally and mechanistically defining immune activation after TBI. In this review, we explore the burgeoning evidence implicating the acute release of damage associated molecular patterns (DAMPs), such as adenosine 5'-triphosphate (ATP), high mobility group box protein 1 (HMGB1), S100 proteins, and hyaluronic acid in the initiation of progressive neurological injury, including white matter loss after TBI. The role that pattern recognition receptors, including toll-like receptor and purinergic receptors, play in progressive neurological injury after TBI is detailed. Finally, we provide support for the notion that resident and infiltrating macrophages are critical cellular targets linking acute DAMP release with adaptive immune responses and chronic injury after TBI. The therapeutic potential of targeting DAMPs and barriers to clinical translational, in the context of TBI patient management, are discussed.