Distinct roles for hyaluronan in neural stem cell niches and perineuronal nets

Hyaluronan in mesenchymal stromal cell lineage differentiation from human pluripotent stem cells: application in serum free culture

BACKGROUND

Hyaluronan (HA) is an extracellular glycosaminoglycan polysaccharide with widespread roles throughout development and in healthy and neoplastic tissues. In pluripotent stem cell culture it can support both stem cell renewal and differentiation. However, responses to HA in culture are influenced by interaction with a range of cognate factors and receptors including components of blood serum supplements, which alter results. These may contribute to variation in cell batch production yield and phenotype as well as heighten the risks of adventitious pathogen transmission in the course of cell processing for therapeutic applications. MAIN: Here we characterise differentiation of a human embryo/pluripotent stem cell derived Mesenchymal Stromal Cell (hESC/PSC-MSC)-like cell population by culture on a planar surface coated with HA in serum-free media qualified for cell production for therapy. Resulting cells met minimum criteria of the International Society for Cellular Therapy for identification as MSC by expression of. CD90, CD73, CD105, and lack of expression for CD34, CD45, CD14 and HLA-II. They were positive for other MSC associated markers (i.e.CD166, CD56, CD44, HLA 1-A) whilst negative for others (e.g. CD271, CD71, CD146). In vitro co-culture assessment of MSC associated functionality confirmed support of growth of hematopoietic progenitors and inhibition of mitogen activated proliferation of lymphocytes from umbilical cord and adult peripheral blood mononuclear cells, respectively. Co-culture with immortalized THP-1 monocyte derived macrophages (Mɸ) concurrently stimulated with lipopolysaccharide as a pro-inflammatory stimulus, resulted in a dose dependent increase in pro-inflammatory IL6 but negligible effect on TNFα. To further investigate these functionalities, a bulk cell RNA sequence comparison with adult human bone marrow derived MSC and hESC substantiated a distinctive genetic signature more proximate to the former.

CONCLUSION

Cultivation of human pluripotent stem cells on a planar substrate of HA in serum-free culture media systems is sufficient to yield a distinctive developmental mesenchymal stromal cell lineage with potential to modify the function of haematopoietic lineages in therapeutic applications.

Unlocking the Potential of Stem Cell Microenvironments In Vitro

The field of regenerative medicine has recently witnessed groundbreaking advancements that hold immense promise for treating a wide range of diseases and injuries. At the forefront of this revolutionary progress are stem cells. Stem cells typically reside in specialized environments in vivo, known as microenvironments or niches, which play critical roles in regulating stem cell behavior and determining their fate. Therefore, understanding the complex microenvironments that surround stem cells is crucial for advancing treatment options in regenerative medicine and tissue engineering applications. Several research articles have made significant contributions to this field by exploring the interactions between stem cells and their surrounding niches, investigating the influence of biomechanical and biochemical cues, and developing innovative strategies for tissue regeneration. This review highlights the key findings and contributions of these studies, shedding light on the diverse applications that may arise from the understanding of stem cell microenvironments, thus harnessing the power of these microenvironments to transform the landscape of medicine and offer new avenues for regenerative therapies.

Neural stem cell therapies for spinal cord injury repair: an update on recent preclinical and clinical advances

Traumatic spinal cord injury (SCI) is a leading cause of lifelong disabilities. Permanent sensory, motor and autonomic impairments after SCI are substantially attributed to degeneration of spinal cord neurons and axons, and disintegration of neural network. To date, minimal regenerative treatments are available for SCI with an unmet need for new therapies to reconstruct the damaged spinal cord neuron-glia network and restore connectivity with the supraspinal pathways. Multipotent neural precursor cells (NPCs) have a unique capacity to generate neurons, oligodendrocytes and astrocytes. Due to this capacity, NPCs have been an attractive cell source for cellular therapies for SCI. Transplantation of NPCs has been extensively tested in preclinical models of SCI in the past two decades. These studies have identified opportunities and challenges associated with NPC therapies. While NPCs have the potential to promote neuroregeneration through various mechanisms, their low long-term survival and integration within the host injured spinal cord limit the functional benefits of NPC-based therapies for SCI. To address this challenge, combinatorial strategies have been developed to optimize the outcomes of NPC therapies by enriching SCI microenvironment through biomaterials, genetic and pharmacological therapies. In this review, we will provide an in-depth discussion on recent advances in preclinical NPC-based therapies for SCI. We will discuss modes of actions and mechanism by which engrafted NPCs contribute to the repair process and functional recovery. We will also provide an update on current clinical trials and new technologies that have facilitated preparation of medical-grade human NPCs suitable for transplantation in clinical studies.

Hindbrain boundaries as niches of neural progenitor and stem cells regulated by the extracellular matrix proteoglycan chondroitin sulphate

The interplay between neural progenitors and stem cells (NPSCs), and their extracellular matrix (ECM) is a crucial regulatory mechanism that determines their behavior. Nonetheless, how the ECM dictates the state of NPSCs remains elusive. The hindbrain is valuable to examine this relationship, as cells in the ventricular surface of hindbrain boundaries (HBs), which arise between any two neighboring rhombomeres, express the NPSC marker Sox2, while being surrounded with the membrane-bound ECM molecule chondroitin sulphate proteoglycan (CSPG), in chick and mouse embryos. CSPG expression was used to isolate HB Sox2+ cells for RNA-sequencing, revealing their distinguished molecular properties as typical NPSCs, which express known and newly identified genes relating to stem cells, cancer, the matrisome and cell cycle. In contrast, the CSPG- non-HB cells, displayed clear neural-differentiation transcriptome. To address whether CSPG is significant for hindbrain development, its expression was manipulated in vivo and in vitro. CSPG manipulations shifted the stem versus differentiation state of HB cells, evident by their behavior and altered gene expression. These results provide further understanding of the uniqueness of hindbrain boundaries as repetitive pools of NPSCs in-between the rapidly growing rhombomeres, which rely on their microenvironment to maintain their undifferentiated state during development.

The mechanisms of perineuronal net abnormalities in contributing aging and neurological diseases

The perineuronal net (PNN) is a highly latticed extracellular matrix in the central nervous system, which is composed of hyaluronic acid, proteoglycan, hyaluronan and proteoglycan link protein (Hapln), and tenascin. PNN is predominantly distributed in GABAergic interneurons expressing Parvalbumin (PV) and plays a critical role in synaptic function, learning and memory, oxidative stress, and inflammation. In addition, PNN's structure and function are also modulated by a variety of factors, including protein tyrosine phosphatase σ (PTPσ), orthodenticle homeo-box 2 (Otx2), and erb-b2 receptor tyrosine kinase 4 (ErbB4). Glycosaminoglycan (GAG), a component of proteoglycan, also influences PNN through its sulfate mode. PNN undergoes abnormal changes during aging and in various neurological diseases, such as Alzheimer's disease, Parkinson's disease, schizophrenia, autism spectrum disorder, and multiple sclerosis. Nevertheless, there is limited report on the relationship between PNN and aging or age-related neurological diseases. This review elaborates on the mechanisms governing PNN regulation and summarizes how PNN abnormalities contribute to aging and neurological diseases, offering insights for potential treatments.

Structural changes in perineuronal nets and their perforating GABAergic synapses precede motor coordination recovery post stroke

BACKGROUND

Stroke remains one of the leading causes of long-term disability worldwide, and the development of effective restorative therapies is hindered by an incomplete understanding of intrinsic brain recovery mechanisms. Growing evidence indicates that the brain extracellular matrix (ECM) has major implications for neuroplasticity. Here we explored how perineuronal nets (PNNs), the facet-like ECM layers surrounding fast-spiking interneurons, contribute to neurological recovery after focal cerebral ischemia in mice with and without induced stroke tolerance.

METHODS

We investigated the structural remodeling of PNNs after stroke using 3D superresolution stimulated emission depletion (STED) and structured illumination (SR-SIM) microscopy. Superresolution imaging allowed for the precise reconstruction of PNN morphology using graphs, which are mathematical constructs designed for topological analysis. Focal cerebral ischemia was induced by transient occlusion of the middle cerebral artery (tMCAO). PNN-associated synapses and contacts with microglia/macrophages were quantified using high-resolution confocal microscopy.

RESULTS

PNNs undergo transient structural changes after stroke allowing for the dynamic reorganization of GABAergic input to motor cortical L5 interneurons. The coherent remodeling of PNNs and their perforating inhibitory synapses precedes the recovery of motor coordination after stroke and depends on the severity of the ischemic injury. Morphological alterations in PNNs correlate with the increased surface of contact between activated microglia/macrophages and PNN-coated neurons.

CONCLUSIONS

Our data indicate a novel mechanism of post stroke neuroplasticity involving the tripartite interaction between PNNs, synapses, and microglia/macrophages. We propose that prolonging PNN loosening during the post-acute period can extend the opening neuroplasticity window into the chronic stroke phase.

AKT inhibitor Hu7691 induces differentiation of neuroblastoma cells

While neuroblastoma accounts for 15% of childhood tumor-related deaths, treatments against neuroblastoma remain scarce and mainly consist of cytotoxic chemotherapeutic drugs. Currently, maintenance therapy of differentiation induction is the standard of care for neuroblastoma patients in clinical, especially high-risk patients. However, differentiation therapy is not used as a first-line treatment for neuroblastoma due to low efficacy, unclear mechanism, and few drug options. Through compound library screening, we accidently found the potential differentiation-inducing effect of AKT inhibitor Hu7691. The protein kinase B (AKT) pathway is an important signaling pathway for regulating tumorigenesis and neural differentiation, yet the relation between the AKT pathway and neuroblastoma differentiation remains unclear. Here, we reveal the anti-proliferation and neurogenesis effect of Hu7691 on multiple neuroblastoma cell lines. Further evidence including neurites outgrowth, cell cycle arrest, and differentiation mRNA marker clarified the differentiation-inducing effect of Hu7691. Meanwhile, with the introduction of other AKT inhibitors, it is now clear that multiple AKT inhibitors can induce neuroblastoma differentiation. Furthermore, silencing AKT was found to have the effect of inducing neuroblastoma differentiation. Finally, confirmation of the therapeutic effects of Hu7691 is dependent on inducing differentiation in vivo, suggesting that Hu7691 is a potential molecule against neuroblastoma. Through this study, we not only define the key role of AKT in the progression of neuroblastoma differentiation but also provide potential drugs and key targets for the application of differentiation therapies for neuroblastoma clinically.

The importance of RHAMM in the normal brain and gliomas: physiological and pathological roles

Although the literature about the functions of hyaluronan and the CD44 receptor in the brain and brain tumours is extensive, the role of the receptor for hyaluronan-mediated motility (RHAMM) in neural stem cells and gliomas remain poorly explored. RHAMM is considered a multifunctional receptor which performs various biological functions in several normal tissues and plays a significant role in cancer development and progression. RHAMM was first identified for its ability to bind to hyaluronate, the extracellular matrix component associated with cell motility control. Nevertheless, additional functions of this protein imply the interaction with different partners or cell structures to regulate other biological processes, such as mitotic-spindle assembly, gene expression regulation, cell-cycle control and proliferation. In this review, we summarise the role of RHAMM in normal brain development and the adult brain, focusing on the neural stem and progenitor cells, and discuss the current knowledge on RHAMM involvement in glioblastoma progression, the most aggressive glioma of the central nervous system. Understanding the implications of RHAMM in the brain could be useful to design new therapeutic approaches to improve the prognosis and quality of life of glioblastoma patients.

N-Cadherin adhesive ligation regulates mechanosensitive neural stem cell lineage commitment in 3D matrices

We demonstrate a novel strategy to independently control cell–ECM and cell–cell interactions of neural stem cells in a 3D matrix.

Structural and Functional Modulation of Perineuronal Nets: In Search of Important Players with Highlight on Tenascins

The extracellular matrix (ECM) of the brain plays a crucial role in providing optimal conditions for neuronal function. Interactions between neurons and a specialized form of ECM, perineuronal nets (PNN), are considered a key mechanism for the regulation of brain plasticity. Such an assembly of interconnected structural and regulatory molecules has a prominent role in the control of synaptic plasticity. In this review, we discuss novel ways of studying the interplay between PNN and its regulatory components, particularly tenascins, in the processes of synaptic plasticity, mechanotransduction, and neurogenesis. Since enhanced neuronal activity promotes PNN degradation, it is possible to study PNN remodeling as a dynamical change in the expression and organization of its constituents that is reflected in its ultrastructure. The discovery of these subtle modifications is enabled by the development of super-resolution microscopy and advanced methods of image analysis.

The role of hyaluronan in myelination and remyelination after white matter injury

Hyaluronan is one of the major components of the neural extracellular matrix (ECM) and provides structural support in physiological conditions. Altered hyaluronan regulation is implicated in the pathogenesis of white matter injury (WMI), such as perinatal WMI, multiple sclerosis (MS), traumatic brain injury (TBI). Early research reported diverse central nervous system (CNS) insults led to accumulated high-molecular-weight (HMW) hyaluronan in hypomyelinating/demyelinating lesions. Furthermore, recent findings have shown an elevated production of hyaluronan fragments in WMI, possibly resulting from HMW hyaluronan degradation. Subsequent in vitro studies identified bioactive hyaluronan fragments with a specific molecular weight (around 2x10⁵ Da) regulating oligodendrocyte precursor cells (OPCs) maturation and myelination/remyelination in WMI. However, it is unclear about the effective hyaluronidases in generating bioactive hyaluronan fragments. Several hyaluronidases are proposed recently. Although PH20 is shown to block OPCs maturation by generating bioactive hyaluronan fragments in vitro, it seems unlikely to play a primary role in WMI with negligible expression levels in vivo. The role of other hyaluronidases on OPCs maturation and myelination/remyelination is still unknown. Other than hyaluronidases, CD44 and Toll-like receptors 2 (TLR2) are also implicated in HMW hyaluronan degradation in WMI. Moreover, recent studies elucidated bioactive hyaluronan fragments interact with TLR4, initiating signaling cascades to mediate myelin basic protein (MBP) transcription. Identifying key factors in hyaluronan actions may provide novel therapeutic targets to promote OPCs maturation and myelination/remyelination in WMI.

The effect of electrospun scaffolds on the glycosaminoglycan profile of differentiating neural stem cells

The use of electrospun scaffolds for neural tissue engineering applications allows a closer mimicry of the native tissue extracellular matrix (ECM), important for the transplantation of cells in vivo. Moreover, the role of the electrospun fiber mat topography on neural stem cell (NSC) differentiation remains to be completely understood. In this work REN-VM cells (NSC model) were differentiated on polycaprolactone (PCL) nanofibers, obtained by wet/wet electrospinning, and on flat glass lamellas. The obtained differentiation profile of NSCs was evaluated using immunofluorescence and qPCR analysis. Glycosaminoglycan (GAG) analysis was successfully emplyed to evaluate changes in the GAG profile of differentiating cells through the use of the highly sensitive liquid chromatography-tandem mass/mass spectrometry (LC-MS/MS) method. Our results show that both culture platforms allow the differentiation of REN-VM cells into neural cells (neurons and astrocytes) similarly. Moreover, LC-MS/MS analysis shows changes in the production of GAGs present both in cell cultures and conditioned media samples. In the media, hyaluronic acid (HA) was detected and correlated with cellular activity and the production of a more plastic extracellular matrix. The cell samples evidence changes in chondroitin sulfate (CS4S, CS6S, CS4S6S) and heparan sulfate (HS6S, HS0S), similar to those previously described in vivo studies and possibly associated with the creation of complex structures, such as perineural networks. The GAG profile of differentiating REN-VM cells on electrospun scaffolds was analyzed for the first time. Our results highlight the advantage of using platforms obtain more reliable and robust neural tissue-engineered transplants.

Impact of Reck expression and promoter activity in neuronal in vitro differentiation

Reck (REversion-inducing Cysteine-rich protein with Kazal motifs) tumor suppressor gene encodes a multifunctional glycoprotein which inhibits the activity of several matrix metalloproteinases (MMPs), and has the ability to modulate the Notch and canonical Wnt pathways. Reck-deficient neuro-progenitor cells undergo precocious differentiation; however, modulation of Reck expression during progression of the neuronal differentiation process is yet to be characterized. In the present study, we demonstrate that Reck expression levels are increased during in vitro neuronal differentiation of PC12 pheochromocytoma cells and P19 murine teratocarcinoma cells and characterize mouse Reck promoter activity during this process. Increased Reck promoter activity was found upon induction of differentiation in PC12 cells, in accordance with its increased mRNA expression levels in mouse in vitro models. Interestingly, Reck overexpression, prior to the beginning of the differentiation protocol, led to diminished efficiency of the neuronal differentiation process. Taken together, our findings suggest that increased Reck expression at early stages of differentiation diminishes the number of neuron-like cells, which are positive for the beta-3 tubulin marker. Our data highlight the importance of Reck expression evaluation to optimize in vitro neuronal differentiation protocols.

Modulatory properties of extracellular matrix glycosaminoglycans and proteoglycans on neural stem cells behavior: Highlights on regenerative potential and bioactivity

Despite the poor regenerative capacity of the adult central nervous system (CNS) in mammals, two distinct regions, subventricular zone (SVZ) and the subgranular zone (SGZ), continue to generate new functional neurons throughout life which integrate into the pre-existing neuronal circuitry. This process is not fixed but highly modulated, revealing many intrinsic and extrinsic mechanisms by which this performance can be optimized for a given environment. The capacity for self-renewal, proliferation, migration, and multi-lineage potency of neural stem cells (NSCs) underlines the necessity of controlling stem cell fate. In this context, the native and local microenvironment plays a critical role, and the application of this highly organized architecture in the CNS has been considered as a fundamental concept in the generation of new effective therapeutic strategies in tissue engineering approaches. The brain extracellular matrix (ECM) is composed of biomacromolecules, including glycosaminoglycans, proteoglycans, and glycoproteins that provide various biological actions through biophysical and biochemical signaling pathways. Herein, we review predominantly the structure and function of the mentioned ECM composition and their regulatory impact on multiple and diversity of biological functions, including neural regeneration, survival, migration, differentiation, and final destiny of NSCs.

The scrambled story between hyaluronan and glioblastoma

Advances in cancer biology are revealing the importance of the cancer cell microenvironment on tumorigenesis and cancer progression. Hyaluronan (HA), the main glycosaminoglycan in the extracellular matrix, has been associated with the progression of glioblastoma (GBM), the most frequent and lethal primary tumor in the central nervous system, for several decades. However, the mechanisms by which HA impacts GBM properties and processes have been difficult to elucidate. In this review, we provide a comprehensive assessment of the current knowledge on HA's effects on GBM biology, introducing its primary receptors CD44 and RHAMM and the plethora of relevant downstream signaling pathways that can scramble efforts to directly link HA activity to biological outcomes. We consider the complexities of studying an extracellular polymer and the different strategies used to try to capture its function, including 2D and 3D in vitro studies, patient samples, and in vivo models. Given that HA affects not only migration and invasion, but also cell proliferation, adherence, and chemoresistance, we highlight the potential role of HA as a therapeutic target. Finally, we review the different existing approaches to diminish its protumor effects, such as the use of 4-methylumbelliferone, HA oligomers, and hyaluronidases and encourage further research along these lines in order to improve the survival and quality of life of GBM patients.

Low-intensity ultrasound restores long-term potentiation and memory in senescent mice through pleiotropic mechanisms including NMDAR signaling

Advanced physiological aging is associated with impaired cognitive performance and the inability to induce long-term potentiation (LTP), an electrophysiological correlate of memory. Here, we demonstrate in the physiologically aged, senescent mouse brain that scanning ultrasound combined with microbubbles (SUS^+MB), by transiently opening the blood-brain barrier, fully restores LTP induction in the dentate gyrus of the hippocampus. Intriguingly, SUS treatment without microbubbles (SUS^only), i.e., without the uptake of blood-borne factors, proved even more effective, not only restoring LTP, but also ameliorating the spatial learning deficits of the aged mice. This functional improvement is accompanied by an altered milieu of the aged hippocampus, including a lower density of perineuronal nets, increased neurogenesis, and synaptic signaling, which collectively results in improved spatial learning. We therefore conclude that therapeutic ultrasound is a non-invasive, pleiotropic modality that may enhance cognition in elderly humans.

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.

4-Methylumbelliferone as a potent and selective antitumor drug on a glioblastoma model

Glioblastoma (GBM), the most frequent primary tumor of the central nervous system, has a median survival of 14.6 months. 4-Methylumbelliferone (4MU) is a coumarin derivative widely used as a hyaluronan synthesis inhibitor with proven antitumor activity and without toxic effects reported. We aim to evaluate the antitumor effect of 4MU alone or combined with temozolomide (TMZ) on a GBM cell line, its absence of toxicity on brain cells and its selectivity for tumor cells. The antitumor effect of 4MU alone or combined with TMZ was evaluated on GL26 cells by assessing the metabolic activity through the XTT assay, cell proliferation by BrdU incorporation assay, migration by the wound healing assay, cell death by fluorescein diacetate/propidium iodide (FDA/PI) staining, apoptosis by membrane asymmetry and DNA fragmentation and metalloproteinase activity by zymography. The levels of hyaluronan and its capacity to counteract the effects of 4MU and the expression of RHAMM and CD44 were also determined. The toxicity and selectivity of 4MU were determined by XTT assay and PI staining on normal brain primary cell culture (NBPC-GFP) and GL26/NBPC-GFP cocultures. The GL26 cells expressed RHAMM but not CD44 while synthetized hyaluronan. 4MU decreased hyaluronan synthesis, diminished proliferation and induced apoptosis while reducing cell migration and the activity of metalloproteinases, which was restored by addition of hyaluronic acid. Furthermore, 4MU sensitized GL26 cells to the TMZ effect and showed selective toxicity on tumor cells without exhibiting neurotoxic effects. We demonstrated for the first time the cytotoxic effect of 4MU on GBM cells, highlighting its potential usefulness to improve GBM treatment.

Dysregulation of Hyaluronan Homeostasis During White Matter Injury

Although the extra cellular matrix (ECM) comprises a major proportion of the CNS parenchyma, new roles for the ECM in regeneration and repair responses to CNS injury have only recently been appreciated. The ECM undergoes extensive remodeling following injury to the developing or mature CNS in disorders that -include perinatal hypoxic-ischemic cerebral injury, multiple sclerosis and age-related vascular dementia. Here we focus on recently described mechanisms involving hyaluronan (HA), which negatively impact myelin repair after cerebral white matter injury. Injury induced depolymerization of hyaluronan (HA)-a component of the neural ECM-can inhibit myelin repair through the actions of specific sizes of HA fragments. These bioactive fragments selectively block the maturation of late oligodendrocyte progenitors via an immune tolerance-like pathway that suppresses pro-myelination signaling. We highlight emerging new pathophysiological roles of the neural ECM, particularly of those played by HA fragments (HAf) after injury and discuss strategies to promoter repair and regeneration of chronic myelination failure.

Topological remodeling of cortical perineuronal nets in focal cerebral ischemia and mild hypoperfusion

Despite the crucial role of perineuronal nets (PNNs) in neural plasticity and neurological disorders, their ultrastructural organization remains largely unresolved. We have developed a novel approach combining superresolution structured illumination microscopy (SR-SIM) and mathematical reconstruction that allows for quantitative analysis of PNN topology. Since perineuronal matrix is capable to restrict neural plasticity but at the same time is necessary to maintain synapses, we hypothesized that a beneficial post stroke recovery requires a reversible loosening of PNNs. Our results indicated that focal cerebral ischemia induces partial depletion of PNNs and that mild hypoperfusion not associated with ischemic injury can induce ultra-structural rearrangements in visually intact meshworks. In line with the activation of neural plasticity under mild stress stimuli, we provide evidence that topological conversion of PNNs can support post stroke neural rewiring.