The extracellular matrix of the central and peripheral nervous systems: structure and function

Both Type I Bovine Collagen Conduits and Porcine Small Intestine Submucosa Conduits Result in Functional Sensory Recovery Following Peripheral Nerve Microsurgery: A Systematic Review and Meta-Analysis

PURPOSE

The study purpose was to measure and compare the time to functional sensory recovery (FSR) and incidence of FSR by 6 and 12 months between type I bovine collagen conduits versus porcine small intestine submucosa (SIS) conduits with primary neurorrhaphy for peripheral nerve injury repair.

METHODS

A systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were conducted. The predictor variable was the type of conduit-either bovine collagen or porcine SIS. The primary outcome variable was the number of months between surgery and the patient achieving FSR. The secondary outcome variable was the proportion of patients who achieved FSR that did so by 6 and 12 months. A log-rank test was performed to evaluate the statistical significance of the differences observed in the overall time-to-FSR data and by 6 and 12 months.

RESULTS

We screened 67 publications of which 8 were included. The sample sizes were 137 and 96 patients for the bovine collagen and porcine SIS groups, respectively. The median time to FSR for the bovine collagen conduit group was 9 months (interquartile range: 6); the median time to FSR for the porcine SIS conduit group 6 months (interquartile range: 3 months) (P = .50). Of the patients who achieved FSR, 42% of patients with bovine collagen conduits and 64% of patients with porcine SIS conduits did so within 6 months (P < .01). Of the patients who achieved FSR, 94% of patients with bovine collagen conduits and 82% of patients with porcine SIS conduits did so within 12 months (P < .01).

CONCLUSION

Although a significant difference was found in the incidence of FSR at 6 and 12 months, no significant difference was found in overall time to FSR, supporting the use of either conduit for peripheral nerve repair.

Decellularization of various tissues and organs through chemical methods

Due to the increase in demand for donor organs and tissues during the past 20 years, new approaches have been created. These methods include, for example, tissue engineering in vitro and the production of regenerative biomaterials for transplantation. Applying the natural extracellular matrix (ECM) as a bioactive biomaterial for clinical applications is a unique approach known as decellularization technology. Decellularization is the process of eliminating cells from an extracellular matrix while preserving its natural components including its structural and functional proteins and glycosaminoglycan. This can be achieved by physical, chemical, or biological processes. A naturally formed three-dimensional structure with a biocompatible and regenerative structure is the result of the decellularization process. Decreasing the biological factors and antigens at the transplant site reduces the risk of adverse effects including inflammatory responses and immunological rejection. Regenerative medicine and tissue engineering applications can benefit from the use of decellularization, a promising approach that provides a biomaterial that preserves its extracellular matrix.

Exploring tissue permeability of brain tumours in different grades: Insights from pore-scale fluid dynamics analysis

Interstitial fluid (ISF) flow is identified as an essential physiological process that plays an important role in the development and progression of brain tumours. However, the relationship between the permeability of the tumour tissue, a complex porous medium, and the interstitial fluid flow around the tumour cells at the microscale is not well understood. To shed light on this issue, and in the absence of experimental techniques that can provide direct measurements, we develop a computational model to predict the tissue permeability of brain tumours in different grades by analysing the ISF flow at the pore scale. The 3-D geometrical models of tissue extracellular spaces are digitally reconstructed for each grade tumour based on their morphological properties measured from microscopic images. The predictive accuracy of the framework is validated by experimental results reported in the literature. Our results indicate that high-grade brain tumours are less permeable despite their higher porosity, whereas necrotic areas of glioblastoma are more permeable than the viable tumour areas. This implies that tissue permeability is primarily governed by both tissue porosity and the deposition of hyaluronic acid (HA), a key component of the extracellular matrix, while the HA deposition can have a greater effect than macro-level porosity. Parametric studies show that tissue permeability falls exponentially with increasing HA concentration in all grades of brain tumours, and this can be captured using an empirically derived relationship in a quantitative manner. These findings provide an improved understanding of the hydraulic properties of brain tumours and their intrinsic links to tumour microstructure. This work can be used to reveal the intratumoural physiochemical processes that rely on fluid flow and offer a powerful tool to tune textured and porous biomaterials for desired transport properties. STATEMENT OF SIGNIFICANCE: Interstitial fluid flow in the extracellular space of brain tumours plays a crucial role in their progression, development, and response to drug treatments. However, the mechanisms of interstitial fluid transport around tumour cells and the characterization of these microscale transports at the tissue scale to meet clinical requirements are largely unknown. In the absence of advanced experimental techniques to capture these pore-scale transport phenomena, we have developed and validated a computational framework to successfully reveal these phenomena across all grades of brain tumours. For the first time, we have quantitatively determined the tissue permeability of all grades of brain tumours as a function of the concentration of hyaluronic acid, a key component of the extracellular matrix. This framework will enhance our ability to capture the intratumoural physicochemical processes in brain tumours and correlate them with tumour tissue-scale behaviours.

Impact of cannabinoids on synapse markers in an SH-SY5Y cell culture model

Patients suffering from schizophrenic psychosis show reduced synaptic connectivity compared to healthy individuals, and often, the use of cannabis precedes the onset of schizophrenic psychosis. Therefore, we investigated if different types of cannabinoids impact methylation patterns and expression of schizophrenia candidate genes concerned with the development and preservation of synapses and synaptic function in a SH-SY5Y cell culture model. For this purpose, SH-SY5Y cells were differentiated into a neuron-like cell type as previously described. Effects of the cannabinoids delta-9-THC, HU-210, and Anandamide were investigated by analysis of cell morphology and measurement of neurite/dendrite lengths as well as determination of methylation pattern, expression (real time-qPCR, western blot) and localization (immunocytochemistry) of different target molecules concerned with the formation of synapses. Regarding the global impression of morphology, cells, and neurites appeared to be a bit more blunted/roundish and to have more structures that could be described a bit boldly as resembling transport vesicles under the application of the three cannabinoids in comparison to a sole application of retinoic acid (RA). However, there were no obvious differences between the three cannabinoids. Concerning dendrites or branch lengths, there was a significant difference with longer dendrites and branches in RA-treated cells than in undifferentiated control cells (as shown previously), but there were no differences between cannabinoid treatment and exclusive RA application. Methylation rates in the promoter regions of synapse candidate genes in cannabinoid-treated cells were in between those of differentiated cells and untreated controls, even though findings were significant only in some of the investigated genes. In other targets, the methylation rates of cannabinoid-treated cells did not only approach those of undifferentiated cells but were also valued even beyond. mRNA levels also showed the same tendency of values approaching those of undifferentiated controls under the application of the three cannabinoids for most investigated targets except for the structural molecules (NEFH, MAPT). Likewise, the quantification of expression via western blot analysis revealed a higher expression of targets in RA-treated cells compared to undifferentiated controls and, again, lower expression under the additional application of THC in trend. In line with our earlier findings, the application of RA led to higher fluorescence intensity and/or a differential signal distribution in the cell in most of the investigated targets in ICC. Under treatment with THC, fluorescence intensity decreased, or the signal distribution became similar to the dispersion in the undifferentiated control condition. Our findings point to a decline of neuronal differentiation markers in our in vitro cell-culture system under the application of cannabinoids.

Satellite glial cell manipulation prior to axotomy enhances developing dorsal root ganglion central branch regrowth into the spinal cord

The central and peripheral nervous systems (CNS and PNS, respectively) exhibit remarkable diversity in the capacity to regenerate following neuronal injury with PNS injuries being much more likely to regenerate than those that occur in the CNS. Glial responses to damage greatly influence the likelihood of regeneration by either promoting or inhibiting axonal regrowth over time. However, despite our understanding of how some glial lineages participate in nerve degeneration and regeneration, less is known about the contributions of peripheral satellite glial cells (SGC) to regeneration failure following central axon branch injury of dorsal root ganglia (DRG) sensory neurons. Here, using in vivo, time-lapse imaging in larval zebrafish coupled with laser axotomy, we investigate the role of SGCs in axonal regeneration. In our studies we show that SGCs respond to injury by relocating their nuclei to the injury site during the same period that DRG neurons produce new central branch neurites. Laser ablation of SGCs prior to axon injury results in more neurite growth attempts and ultimately a higher rate of successful central axon regrowth, implicating SGCs as inhibitors of regeneration. We also demonstrate that this SGC response is mediated in part by ErbB signaling, as chemical inhibition of this receptor results in reduced SGC motility and enhanced central axon regrowth. These findings provide new insights into SGC-neuron interactions under injury conditions and how these interactions influence nervous system repair.

Engineering cell-derived extracellular matrix for peripheral nerve regeneration

Extracellular matrices (ECMs) play a key role in nerve repair and are recognized as the natural source of biomaterials. In parallel to extensively studied tissue-derived ECMs (ts-ECMs), cell-derived ECMs (cd-ECMs) also have the capability to partially recapitulate the complicated regenerative microenvironment of native nerve tissues. Notably, cd-ECMs can avoid the shortcomings of ts-ECMs. Cd-ECMs can be prepared by culturing various cells or even autologous cells in vitro under pathogen-free conditions. And mild decellularization can achieve efficient removal of immunogenic components in cd-ECMs. Moreover, cd-ECMs are more readily customizable to achieve the desired functional properties. These advantages have garnered significant attention for the potential of cd-ECMs in neuroregenerative medicine. As promising biomaterials, cd-ECMs bring new hope for the effective treatment of peripheral nerve injuries. Herein, this review comprehensively examines current knowledge about the functional characteristics of cd-ECMs and their mechanisms of interaction with cells in nerve regeneration, with a particular focus on the preparation, engineering optimization, and scalability of cd-ECMs. The applications of cd-ECMs from distinct cell sources reported in peripheral nerve tissue engineering are highlighted and summarized. Furthermore, current limitations that should be addressed and outlooks related to clinical translation are put forward as well.

Mechanical properties of the brain: Focus on the essential role of Piezo1-mediated mechanotransduction in the CNS

BACKGROUND

The brain is a highly mechanosensitive organ, and changes in the mechanical properties of brain tissue influence many physiological and pathological processes. Piezo type mechanosensitive ion channel component 1 (Piezo1), a protein found in metazoans, is highly expressed in the brain and involved in sensing changes of the mechanical microenvironment. Numerous studies have shown that Piezo1-mediated mechanotransduction is closely related to glial cell activation and neuronal function. However, the precise role of Piezo1 in the brain requires further elucidation.

OBJECTIVE

This review first discusses the roles of Piezo1-mediated mechanotransduction in regulating the functions of a variety of brain cells, and then briefly assesses the impact of Piezo1-mediated mechanotransduction on the progression of brain dysfunctional disorders.

CONCLUSIONS

Mechanical signaling contributes significantly to brain function. Piezo1-mediated mechanotransduction regulates processes such as neuronal differentiation, cell migration, axon guidance, neural regeneration, and oligodendrocyte axon myelination. Additionally, Piezo1-mediated mechanotransduction plays significant roles in normal aging and brain injury, as well as the development of various brain diseases, including demyelinating diseases, Alzheimer's disease, and brain tumors. Investigating the pathophysiological mechanisms through which Piezo1-mediated mechanotransduction affects brain function will give us a novel entry point for the diagnosis and treatment of numerous brain diseases.

Collagen turnover is associated with cardiovascular autonomic and peripheral neuropathy in type 1 diabetes: novel pathophysiological mechanism?

BACKGROUND

Diabetic cardiovascular autonomic neuropathy (CAN) and distal symmetrical polyneuropathy (DSPN) are severe diabetic complications. Collagen type VI (COL6) and III (COL3) have been associated with nerve function. We investigated if markers of COL6 formation (PRO-C6) and COL3 degradation (C3M) were associated with neuropathy in people with type 1 diabetes (T1D).

METHODS

In a cross-sectional study including 300 people with T1D, serum and urine PRO-C6 and C3M were obtained. CAN was assessed by cardiovascular reflex tests: heart rate response to deep breathing (E/I ratio), to standing (30/15 ratio) and to the Valsalva maneuver (VM). Two or three pathological CARTs constituted CAN. DSPN was assessed by biothesiometry. Symmetrical vibration sensation threshold above 25 V constituted DSPN.

RESULTS

Participants were (mean (SD)) 55.7 (9.3) years, 51% were males, diabetes duration was 40.0 (8.9) years, HbA1c was 63 (11 mmol/mol, (median (IQR)) serum PRO-C6 was 7.8 (6.2;11.0) ng/ml and C3M 8.3 (7.1;10.0) ng/ml. CAN and DSPN were diagnosed in 34% and 43% of participants, respectively. In models adjusted for relevant confounders a doubling of serum PRO-C6, was significantly associated with odds ratio > 2 for CAN and > 1 for DSPN, respectively. Significance was retained after additional adjustments for eGFR only for CAN. Higher serum C3M was associated with presence of CAN, but not after adjustment for eGFR. C3M was not associated with DSPN. Urine PRO-C6 analyses indicated similar associations.

CONCLUSIONS

Results show previously undescribed associations between markers of collagen turnover and risk of CAN and to a lesser degree DSPN in T1D.

Collagen for neural tissue engineering: Materials, strategies, and challenges

Neural tissue engineering (NTE) has made remarkable strides in recent years and holds great promise for treating several devastating neurological disorders. Selecting optimal scaffolding material is crucial for NET design strategies that enable neural and non-neural cell differentiation and axonal growth. Collagen is extensively employed in NTE applications due to the inherent resistance of the nervous system against regeneration, functionalized with neurotrophic factors, antagonists of neural growth inhibitors, and other neural growth-promoting agents. Recent advancements in integrating collagen with manufacturing strategies, such as scaffolding, electrospinning, and 3D bioprinting, provide localized trophic support, guide cell alignment, and protect neural cells from immune activity. This review categorises and analyses collagen-based processing techniques investigated for neural-specific applications, highlighting their strengths and weaknesses in repair, regeneration, and recovery. We also evaluate the potential prospects and challenges of using collagen-based biomaterials in NTE. Overall, this review offers a comprehensive and systematic framework for the rational evaluation and applications of collagen in NTE.

Microenvironments Matter: Advances in Brain-on-Chip

To highlight the particular needs with respect to modeling the unique and complex organization of the human brain structure, we reviewed the state-of-the-art in devising brain models with engineered instructive microenvironments. To acquire a better perspective on the brain's working mechanisms, we first summarize the importance of regional stiffness gradients in brain tissue, varying per layer and the cellular diversities of the layers. Through this, one can acquire an understanding of the essential parameters in emulating the brain in vitro. In addition to the brain's organizational architecture, we addressed also how the mechanical properties have an impact on neuronal cell responses. In this respect, advanced in vitro platforms emerged and profoundly changed the methods of brain modeling efforts from the past, mainly focusing on animal or cell line research. The main challenges in imitating features of the brain in a dish are with regard to composition and functionality. In neurobiological research, there are now methods that aim to cope with such challenges by the self-assembly of human-derived pluripotent stem cells (hPSCs), i.e., brainoids. Alternatively, these brainoids can be used stand-alone or in conjunction with Brain-on-Chip (BoC) platform technology, 3D-printed gels, and other types of engineered guidance features. Currently, advanced in vitro methods have made a giant leap forward regarding cost-effectiveness, ease-of-use, and availability. We bring these recent developments together into one review. We believe our conclusions will give a novel perspective towards advancing instructive microenvironments for BoCs and the understanding of the brain's cellular functions either in modeling healthy or diseased states of the brain.

Decellularized brain extracellular matrix slice glioblastoma culture model recapitulates the interaction between cells and the extracellular matrix without a nutrient-oxygen gradient interference

Decellularized extracellular matrix (dECM) is a valuable tool for generating three-dimensional in vitro tumor models that effectively recapitulate tumor-extracellular matrix (ECM) interactions. However, in current culture models, the components and structures of dECM are enzymatically disrupted to form hydrogels, making it difficult to recapitulate the native ECM. Additionally, when studying ECM-cell interactions, large-volume tumor culture models are incompatible with traditional experimental techniques and the nutrient-oxygen concentration gradient, which is a significant confounding factor. To address these issues, we developed a decellularized brain extracellular matrix slice (dBECMS) glioblastoma (GBM) culture model. This model possesses good light transmittance and substance diffusivity, making it compatible with traditional experimental techniques without forming nutrient-oxygen concentration gradients. Through transcriptomic analysis, we found that native brain ECM has a broad impact on glioma cells; the impact involves the ECM-ECM receptor interactions and the ECM and metabolic reprogramming. Further experiments demonstrated that dBECMS promoted glucose consumption and lactate production in GBM cells. Silver staining experiments revealed abundant proteins in the media of dBECMS, suggesting the degradation of the brain ECM by GBM cells. Transcriptome analysis also showed that the dBECMS-GBM culture model more accurately recapitulated the transcriptional profile of GBM than the two-dimensional culture. We experimentally demonstrated that the dBECMS-GBM model enhanced the resistance of GBM cells to temozolomide and increased the stemness of GBM cells. Additionally, we demonstrated the feasibility of the dBECMS-GBM model as a platform for drug response modeling. STATEMENT OF SIGNIFICANCE: The decellularized brain extracellular matrix (ECM) slice glioblastoma culture model mimics the interaction between native brain ECM and glioblastoma when glioblastoma infiltrates the brain and reveals the effects of native brain ECM on glioblastoma metabolism, ECM reprogramming, drug responsiveness, and stemness.

Hyaluronic acid based next generation bioink for 3D bioprinting of human stem cell derived corneal stromal model with innervation

Corneal transplantation remains gold standard for the treatment of severe cornea diseases, however, scarcity of donor cornea is a serious bottleneck. 3D bioprinting holds tremendous potential for cornea tissue engineering (TE). One of the key technological challenges is to design bioink compositions with ideal printability and cytocompatibility. Photo-crosslinking and ionic crosslinking are often used for the stabilization of 3D bioprinted structures, which can possess limitations on biological functionality of the printed cells. Here, we developed a hyaluronic acid-based dopamine containing bioink using hydrazone crosslinking chemistry for the 3D bioprinting of corneal equivalents. First, the shear thinning property, viscosity, and mechanical stability of the bioink were optimized before extrusion-based 3D bioprinting for the shape fidelity and self-healing property characterizations. Subsequently, human adipose stem cells (hASCs) and hASC-derived corneal stromal keratocytes were used for bioprinting corneal stroma structures and their cell viability, proliferation, microstructure and expression of key proteins (lumican, vimentin, connexin 43,α-smooth muscle actin) were evaluated. Moreover, 3D bioprinted stromal structures were implanted intoex vivoporcine cornea to explore tissue integration. Finally, human pluripotent stem cell derived neurons (hPSC-neurons), were 3D bioprinted to the periphery of the corneal structures to analyze innervation. The bioink showed excellent shear thinning property, viscosity, printability, shape fidelity and self-healing properties with high cytocompatibility. Cells in the printed structures displayed good tissue formation and 3D bioprinted cornea structures demonstrated excellentex vivointegration to host tissue as well asin vitroinnervation. The developed bioink and the printed cornea stromal equivalents hold great potential for cornea TE applications.

Altered Extracellular Matrix as an Alternative Risk Factor for Epileptogenicity in Brain Tumors

Seizures are one of the most common symptoms of brain tumors. The incidence of seizures differs among brain tumor type, grade, location and size, but paediatric-type diffuse low-grade gliomas/glioneuronal tumors are often highly epileptogenic. The extracellular matrix (ECM) is known to play a role in epileptogenesis and tumorigenesis because it is involved in the (re)modelling of neuronal connections and cell-cell signaling. In this review, we discuss the epileptogenicity of brain tumors with a focus on tumor type, location, genetics and the role of the extracellular matrix. In addition to functional problems, epileptogenic tumors can lead to increased morbidity and mortality, stigmatization and life-long care. The health advantages can be major if the epileptogenic properties of brain tumors are better understood. Surgical resection is the most common treatment of epilepsy-associated tumors, but post-surgery seizure-freedom is not always achieved. Therefore, we also discuss potential novel therapies aiming to restore ECM function.

A System-based Approach for the Evaluation of Electromechanical Properties of Brain Tumors

We have developed a semi-automated system integrated with MEMS-based electromechanical sensors to characterize human brain tumors. The electrical impedance and elastic moduli of three types of brain tumors and six normal brain regions were evaluated using the system. The impedance and elastic modulus of glioma was found to be significantly lower than the normal region. It was also observed that the white matter tissues had higher impedance and elastic moduli compared with the grey matter of the same neuroanatomic location. There were observable differences in the electromechanical behavior of gliomas, which originate from glial cells to that of schwannoma and meningioma of different cellular origins. Clinical Relevance- The observations suggest that simultaneous electromechanical characterization of brain tumors can serve as an effective tool for tumor delineation. The developed tool can be used alongside gold standard histopathological analysis to better understand human brain tumors.

Materials for Implantable Surface Electrode Arrays: Current Status and Future Directions

Surface electrode arrays are mainly fabricated from rigid or elastic materials, and precisely manipulated ductile metal films, which offer limited stretchability. However, the living tissues to which they are applied are nonlinear viscoelastic materials, which can undergo significant mechanical deformation in dynamic biological environments. Further, the same arrays and compositions are often repurposed for vastly different tissues rather than optimizing the materials and mechanical properties of the implant for the target application. By first characterizing the desired biological environment, and then designing a technology for a particular organ, surface electrode arrays may be more conformable, and offer better interfaces to tissues while causing less damage. Here, the various materials used in each component of a surface electrode array are first reviewed, and then electrically active implants in three specific biological systems, the nervous system, the muscular system, and skin, are described. Finally, the fabrication of next-generation surface arrays that overcome current limitations is discussed.

Magnetic Resonance Neurography: Improved Diagnosis of Peripheral Neuropathies

Peripheral neuropathies account for the most frequent disorders seen by neurologists, and causes are manifold. The traditional diagnostic gold-standard consists of clinical neurologic examinations supplemented by nerve conduction studies. Due to well-known limitations of standard diagnostics and atypical clinical presentations, establishing the correct diagnosis can be challenging but is critical for appropriate therapies. Magnetic resonance neurography (MRN) is a relatively novel technique that was developed for the high-resolution imaging of the peripheral nervous system. In focal neuropathies, whether traumatic or due to nerve entrapment, MRN has improved the diagnostic accuracy by directly visualizing underlying nerve lesions and providing information on the exact lesion localization, extension, and spatial distribution, thereby assisting surgical planning. Notably, the differentiation between distally located, complete cross-sectional nerve lesions, and more proximally located lesions involving only certain fascicles within a nerve can hold difficulties that MRN can overcome, when basic technical requirements to achieve sufficient spatial resolution are implemented. Typical MRN-specific pitfalls are essential to understand in order to prevent overdiagnosing neuropathies. Heavily T2-weighted sequences with fat saturation are the most established sequences for MRN. Newer techniques, such as T2-relaxometry, magnetization transfer contrast imaging, and diffusion tensor imaging, allow the quantification of nerve lesions and have become increasingly important, especially when evaluating diffuse, non-focal neuropathies. Innovative studies in hereditary, metabolic or inflammatory polyneuropathies, and motor neuron diseases have contributed to a better understanding of the underlying pathomechanism. New imaging biomarkers might be used for an earlier diagnosis and monitoring of structural nerve injury under causative treatments in the future.

Quantitative trait locus mapping identifies a locus linked to striatal dopamine and points to collagen IV alpha-6 chain as a novel regulator of striatal axonal branching in mice

Dopaminergic neurons (DA neurons) are controlled by multiple factors, many involved in neurological disease. Parkinson's disease motor symptoms are caused by the demise of nigral DA neurons, leading to loss of striatal dopamine (DA). Here, we measured DA concentration in the dorsal striatum of 32 members of Collaborative Cross (CC) family and their eight founder strains. Striatal DA varied greatly in founders, and differences were highly heritable in the inbred CC progeny. We identified a locus, containing 164 genes, linked to DA concentration in the dorsal striatum on chromosome X. We used RNAseq profiling of the ventral midbrain of two founders with substantial difference in striatal DA-C56BL/6 J and A/J-to highlight potential protein-coding candidates modulating this trait. Among the five differentially expressed genes within the locus, we found that the gene coding for the collagen IV alpha 6 chain (Col4a6) was expressed nine times less in A/J than in C57BL/6J. Using single cell RNA-seq data from developing human midbrain, we found that COL4A6 is highly expressed in radial glia-like cells and neuronal progenitors, indicating a role in neuronal development. Collagen IV alpha-6 chain (COL4A6) controls axogenesis in simple model organisms. Consistent with these findings, A/J mice had less striatal axonal branching than C57BL/6J mice. We tentatively conclude that DA concentration and axonal branching in dorsal striatum are modulated by COL4A6, possibly during development. Our study shows that genetic mapping based on an easily measured Central Nervous System (CNS) trait, using the CC population, combined with follow-up observations, can parse heritability of such a trait, and nominate novel functions for commonly expressed proteins.

Assessment of a Reliable Fractional Anisotropy Cutoff in Tractography of the Corticospinal Tract for Neurosurgical Patients

Background: Tractography has become a standard technique for planning neurosurgical operations in the past decades. This technique relies on diffusion magnetic resonance imaging. The cutoff value for the fractional anisotropy (FA) has an important role in avoiding false-positive and false-negative results. However, there is a wide variation in FA cutoff values. Methods: We analyzed a prospective cohort of 14 patients (six males and eight females, 50.1 ± 4.0 years old) with intracerebral tumors that were mostly gliomas. Magnetic resonance imaging (MRI) was obtained within 7 days before and within 7 days after surgery with T1 and diffusion tensor image (DTI) sequences. We, then, reconstructed the corticospinal tract (CST) in all patients and extracted the FA values within the resulting volume. Results: The mean FA in all CSTs was 0.4406 ± 0.0003 with the fifth percentile at 0.1454. FA values in right-hemispheric CSTs were lower (p < 0.0001). Postoperatively, the FA values were more condensed around their mean (p < 0.0001). The analysis of infiltrated or compressed CSTs revealed a lower fifth percentile (0.1407 ± 0.0109 versus 0.1763 ± 0.0040, p = 0.0036). Conclusion: An FA cutoff value of 0.15 appears to be reasonable for neurosurgical patients and may shorten the tractography workflow. However, infiltrated fiber bundles must trigger vigilance and may require lower cutoffs.

A microfabricated multi-compartment device for neuron and Schwann cell differentiation

Understanding the complex communication between different cell populations and their interaction with the microenvironment in the central and peripheral nervous systems is fundamental in neuroscience research. The development of appropriate in vitro approaches and tools, able to selectively analyze and/or probe specific cells and cell portions (e.g., axons and cell bodies in neurons), driving their differentiation into specific cell phenotypes, has become therefore crucial in this direction. Here we report a multi-compartment microfluidic device where up to three different cell populations can be cultured in a fluidically independent circuit. The device allows cell migration across the compartments and their differentiation. We showed that an accurate choice of the device geometrical features and cell culture parameters allows to (1) maximize cell adhesion and proliferation of neuron-like human cells (SH-SY5Y cells), (2) control the inter-compartment cell migration of neuron and Schwann cells, (3) perform long-term cell culture studies in which both SH-SY5Y cells and primary rat Schwann cells can be differentiated towards specific phenotypes. These results can lead to a plethora of in vitro co-culture studies in the neuroscience research field, where tuning and investigating cell-cell and cell-microenvironment interactions are essential.

Decellularization techniques and their applications for the repair and regeneration of the nervous system

A variety of surgical and non-surgical approaches have been used to address the impacts of nervous system injuries, which can lead to either impairment or a complete loss of function for affected patients. The inherent ability of nervous tissues to repair and/or regenerate is dampened due to irreversible changes that occur within the tissue remodeling microenvironment following injury. Specifically, dysregulation of the extracellular matrix (i.e., scarring) has been suggested as one of the major factors that can directly impair normal cell function and could significantly alter the regenerative potential of these tissues. A number of tissue engineering and regenerative medicine-based approaches have been suggested to intervene in the process of remodeling which occurs following injury. Decellularization has become an increasingly popular technique used to obtain acellular scaffolds, and their derivatives (hydrogels, etc.), which retain tissue-specific components, including critical structural and functional proteins. These advantageous characteristics make this approach an intriguing option for creating materials capable of stimulating the sensitive repair mechanisms associated with nervous system injuries. Over the past decade, several diverse decellularization methods have been implemented specifically for nervous system applications in an attempt to carefully remove cellular content while preserving tissue morphology and composition. Each application-based decellularized ECM product requires carefully designed treatments that preserve the unique biochemical signatures associated within each tissue type to stimulate the repair of brain, spinal cord, and peripheral nerve tissues. Herein, we review the decellularization techniques that have been applied to create biomaterials with the potential to promote the repair and regeneration of tissues within the central and peripheral nervous system.

How tissue fluidity influences brain tumor progression

Mechanical properties of biological tissues and, above all, their solid or fluid behavior influence the spread of malignant tumors. While it is known that solid tumors tend to have higher mechanical rigidity, allowing them to aggressively invade and spread in solid surrounding healthy tissue, it is unknown how softer tumors can grow within a more rigid environment such as the brain. Here, we use in vivo magnetic resonance elastography (MRE) to elucidate the role of anomalous fluidity for the invasive growth of soft brain tumors, showing that aggressive glioblastomas (GBMs) have higher water content while behaving like solids. Conversely, our data show that benign meningiomas (MENs), which contain less water than brain tissue, are characterized by fluid-like behavior. The fact that the 2 tumor entities do not differ in their soft properties suggests that fluidity plays an important role for a tumor's aggressiveness and infiltrative potential. Using tissue-mimicking phantoms, we show that the anomalous fluidity of neurotumors physically enables GBMs to penetrate surrounding tissue, a phenomenon similar to Saffman-Taylor viscous-fingering instabilities, which occur at moving interfaces between fluids of different viscosity. Thus, targeting tissue fluidity of malignant tumors might open horizons for the diagnosis and treatment of cancer.

A proof of concept study demonstrating that environmental levels of carbamazepine impair early stages of chick embryonic development

Carbamazepine (CBZ) is an anticonvulsant drug used for epilepsy and other disorders. Prescription of CBZ during pregnancy increases the risk for congenital malformations. CBZ is ubiquitous in effluents and persistent during wastewater treatment. Thus, it is re-introduced into agricultural ecosystems upon irrigation with reclaimed wastewater. People consuming produce irrigated with reclaimed wastewater were found to be exposed to CBZ. However, environmental concentrations of CBZ (μgL^-1) are magnitudes lower than its therapeutic levels (μgml^-1), raising the question of whether and how environmental levels of CBZ affect embryonic development. The chick embryo is a powerful and highly sensitive amniotic model system that enables to assess environmental contaminants in the living organism. Since the chick embryonic development is highly similar to mammalians, yet, it develops in an egg, toxic effects can be directly analyzed in a well-controlled system without maternal influences. This research utilized the chick embryo to test whether CBZ is embryo-toxic by using morphological, cellular, molecular and imaging strategies. Three key embryonic stages were monitored: after blastulation (st.1HH), gastrulation/neurulation (st.8HH) and organogenesis (st.15HH). Here we demonstrate that environmental relevant concentrations of CBZ impair morphogenesis in a dose- and stage- dependent manner. Effects on gastrulation, neural tube closure, differentiation and proliferation were exhibited in early stages by exposing embryos to CBZ dose as low as 0.1μgL^-1. Quantification of developmental progression revealed a significant difference in the total score obtained by CBZ-treated embryos compared to controls (up to 5-fold difference, p<0.05). Yet, defects were unnoticed as embryos passed gastrulation/neurulation. This study provides the first evidence for teratogenic effect of environmental-relevant concentrations of CBZ in amniotic embryos that impair early but not late stages of development. These findings call for in-depth risk analysis to ensure that the environmental presence of CBZ and other drugs is not causing irreversible ecological and public-health damages.

Demystifying the extracellular matrix and its proteolytic remodeling in the brain: structural and functional insights

The extracellular matrix (ECM) plays diverse roles in several physiological and pathological conditions. In the brain, the ECM is unique both in its composition and in functions. Furthermore, almost all the cells in the central nervous system contribute to different aspects of this intricate structure. Brain ECM, enriched with proteoglycans and other small proteins, aggregate into distinct structures around neurons and oligodendrocytes. These special structures have cardinal functions in the normal functioning of the brain, such as learning, memory, and synapse regulation. In this review, we have compiled the current knowledge about the structure and function of important ECM molecules in the brain and their proteolytic remodeling by matrix metalloproteinases and other enzymes, highlighting the special structures they form. In particular, the proteoglycans in brain ECM, which are essential for several vital functions, are emphasized in detail.

Biomimetic modification of dual porosity poly(2-hydroxyethyl methacrylate) hydrogel scaffolds-porosity and stem cell growth evaluation

The macroporous synthetic poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels as 3D cellular scaffolds with specific internal morphology, so called dual pore size, were designed and studied. The morphological microstructure of hydrogels was characterized in the gel swollen state and the susceptibility of gels for stem cells was evaluated. The effect of specific chemical groups covalently bound in the hydrogel network by copolymerization on cell adhesion and growth, followed by effect of laminin coating were investigated. The evaluated gels contained either carboxyl groups of the methacrylic acid or quaternary ammonium groups brought by polymerizable ammonium salt or their combinations. The morphology of swollen gel was visualized using the laser scanning confocal microscopy. All hydrogels had very similar porous structures - their matrices contained large pores (up to 10² μm) surrounded with gel walls with small pores (10⁰ μm). The total pore volume in hydrogels swollen in buffer solution ranged between 69 and 86 vol%. Prior to the seeding of the mouse embryonal stem cells, the gels were coated with laminin. The hydrogel with quaternary ammonium groups (with or without laminin) stimulated the cell growth the most. The laminin coating lead to a significant and quaternary ammonium groups. The gel chemical modification influenced also the topology of cell coverage that ranged from individual cell clusters to well dispersed multi cellular structures. Findings in this study point out the laser scanning confocal microscopy as an irreplaceable method for a precise and quick assessment of the hydrogel morphology. In addition, these findings help to optimize the chemical composition of the hydrogel scaffold through the combination of chemical and biological factors leading to intensive cell attachment and proliferation.

Recapitulation of Human Neural Microenvironment Signatures in iPSC-Derived NPC 3D Differentiation

Brain microenvironment plays an important role in neurodevelopment and pathology, where the extracellular matrix (ECM) and soluble factors modulate multiple cellular processes. Neural cell culture typically relies on heterologous matrices poorly resembling brain ECM. Here, we employed neurospheroids to address microenvironment remodeling during neural differentiation of human stem cells, without the confounding effects of exogenous matrices. Proteome and transcriptome dynamics revealed significant changes at cell membrane and ECM during 3D differentiation, diverging significantly from the 2D differentiation. Structural proteoglycans typical of brain ECM were enriched during 3D differentiation, in contrast to basement membrane constituents in 2D. Moreover, higher expression of synaptic and ion transport machinery was observed in 3D cultures, suggesting higher neuronal maturation in neurospheroids. This work demonstrates that 3D neural differentiation as neurospheroids promotes the expression of cellular and extracellular features found in neural tissue, highlighting its value to address molecular defects in cell-ECM interactions associated with neurological disorders.

Extracellular matrix and traumatic brain injury

The brain extracellular matrix (ECM) plays a crucial role in both the developing and adult brain by providing structural support and mediating cell-cell interactions. In this review, we focus on the major constituents of the ECM and how they function in both normal and injured brain, and summarize the changes in the composition of the ECM as well as how these changes either promote or inhibit recovery of function following traumatic brain injury (TBI). Modulation of ECM composition to facilitates neuronal survival, regeneration and axonal outgrowth is a potential therapeutic target for TBI treatment.

Engineering of M13 Bacteriophage for Development of Tissue Engineering Materials

M13 bacteriophages have several qualities that make them attractive candidates as building blocks for tissue regenerating scaffold materials. Through genetic engineering, a high density of functional peptides and proteins can be simultaneously displayed on the M13 bacteriophage's outer coat proteins. The resulting phage can self-assemble into nanofibrous network structures and can guide the tissue morphogenesis through proliferation, differentiation and apoptosis. In this manuscript, we will describe methods to develop major coat-engineered M13 phages as a basic building block and aligned tissue-like matrices to develop regenerative nanomaterials.

BAMBI promotes macrophage proliferation and differentiation in gliomas

The present study investigated the capacity of Bone morphogenic protein and activin membrane‑bound inhibitor homolog (BAMBI) to regulate the migration and differentiation of macrophages in gliomas. Using a migration assay, it was determined that BAMBI stimulated monocytes migration in a dose‑dependent effect. When induced by phorbol myristate acetate (PMA) the monocytes differentiated into macrophages, and BAMBI also increased the migration of PMA‑induced macrophages compared with control cells. The expression of CD68 and BAMBI protein and mRNA in glioma and normal specimens were detected using immunohistochemistry and reverse transcription‑quantitative polymerase chain reaction, respectively. The localization of BAMBI was primarily in macrophages, as demonstrated by staining for the macrophage marker CD68, and the mRNA expression of CD68 and BAMBI were higher in gliomas compared to normal tissues. In addition, the mRNA expression of CD68 and BAMBI were positively correlated (R2=0.64). After treatment with 50 nM PMA and 10 nM BAMBI for 48 h, RAW 264.7 macrophages were exhibited dendrite‑like morphology, indicating that the co‑treatment promoted the differentiation of monocytes to macrophages. The expression of specific markers of M1 [inducible nitric oxide synthase (iNOS) and interleukin (IL)-12] and M2 (IL-10 and arginase 1) type macrophages was determined following 10 nM BAMBI treatment. BAMBI promoted the expression of M1 markers, whereas the M2 markers were not affected, which indicated that BAMBI induced differentiation of M1 type macrophages. These results indicate that BAMBI may be involved in macrophage differentiation in gliomas.

Polymeric scaffolds for three-dimensional culture of nerve cells: a model of peripheral nerve regeneration

Understanding peripheral nerve repair requires the evaluation of 3D structures that serve as platforms for 3D cell culture. Multiple platforms for 3D cell culture have been developed, mimicking peripheral nerve growth and function, in order to study tissue repair or diseases. To recreate an appropriate 3D environment for peripheral nerve cells, key factors are to be considered including: selection of cells, polymeric biomaterials to be used, and fabrication techniques to shape and form the 3D scaffolds for cellular culture. This review focuses on polymeric 3D platforms used for the development of 3D peripheral nerve cell cultures.

Stabilization, Rolling, and Addition of Other Extracellular Matrix Proteins to Collagen Hydrogels Improve Regeneration in Chitosan Guides for Long Peripheral Nerve Gaps in Rats

BACKGROUND: Autograft is still the gold standard technique for the repair of long peripheral nerve injuries. The addition of biologically active scaffolds into the lumen of conduits to mimic the endoneurium of peripheral nerves may increase the final outcome of artificial nerve devices. Furthermore, the control of the orientation of the collagen fibers may provide some longitudinal guidance architecture providing a higher level of mesoscale tissue structure.

OBJECTIVE: To evaluate the regenerative capabilities of chitosan conduits enriched with extracellular matrix-based scaffolds to bridge a critical gap of 15 mm in the rat sciatic nerve.

METHODS: The right sciatic nerve of female Wistar Hannover rats was repaired with chitosan tubes functionalized with extracellular matrix-based scaffolds fully hydrated or stabilized and rolled to bridge a 15 mm nerve gap. Recovery was evaluated by means of electrophysiology and algesimetry tests and histological analysis 4 months after injury.

RESULTS: Stabilized constructs enhanced the success of regeneration compared with fully hydrated scaffolds. Moreover, fibronectin-enriched scaffolds increased muscle reinnervation and number of myelinated fibers compared with laminin-enriched constructs.

CONCLUSION: A mixed combination of collagen and fibronectin may be a promising internal filler for neural conduits for the repair of peripheral nerve injuries, and their stabilization may increase the quality of regeneration over long gaps.

Extracellular matrix components as therapeutics for spinal cord injury

There is no treatment for people with spinal cord injury that leads to significant functional improvements. The extracellular matrix is an intricate, 3-dimensional, structural framework that defines the environment for cells in the central nervous system. The components of extracellular matrix have signaling and regulatory roles in the fate and function of neuronal and non-neuronal cells in the central nervous system. This review discusses the therapeutic potential of extracellular matrix components for spinal cord repair.

Potential new complication in drug therapy development for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by motor neuron degeneration in the brain and spinal cord. Treatment development for ALS is complicated by complex underlying disease factors. Areas covered: Numerous tested drug compounds have shown no benefits in ALS patients, although effective in animal models. Discrepant results of pre-clinical animal studies and clinical trials for ALS have primarily been attributed to limitations of ALS animal models for drug-screening studies and methodological inconsistencies in human trials. Current status of pre-clinical and clinical trials in ALS is summarized. Specific blood-CNS barrier damage in ALS patients, as a novel potential reason for the clinical failures in drug therapies, is discussed. Expert commentary: Pathological perivascular collagen IV accumulation, one unique characteristic of barrier damage in ALS patients, could be hindering transport of therapeutics to the CNS. Restoration of B-CNS-B integrity would foster delivery of therapeutics to the CNS.

Adhesion molecules and the extracellular matrix as drug targets for glioma

The formation of tumor vasculature and cell invasion along white matter tracts have pivotal roles in the development and progression of glioma. A better understanding of the mechanisms of angiogenesis and invasion in glioma will aid the development of novel therapeutic strategies. The processes of angiogenesis and invasion cause the production of an array of adhesion molecules and extracellular matrix (ECM) components. This review focuses on the role of adhesion molecules and the ECM in malignant glioma. The results of clinical trials using drugs targeted against adhesion molecules and the ECM for glioma are also discussed.

Expression pattern of invasion-related molecules in the peritumoral brain

OBJECTIVE

The effectiveness of therapy of intracerebral neoplasms is mainly influenced by the invasive behaviour of the tumour. The peritumoral invasion depends on the interaction between the tumour cells and the extracellular matrix (ECM) of the surrounding brain. The invading tumour cells induce change in the activity of proteases, synthases and expression of ECM-components. These alterations in the peritumoral ECM are in connection to the highly different invasiveness of gliomas and metastatic brain tumours. To understand the fairly modified invasive potential of anaplastic intracerebral tumours of different origin, the effect of tumour on the peritumoral ECM and alterations of invasion related ECM components in the peritumoral brain were evaluated.

METHODS

For this reason the mRNA expression of 19 invasion-related molecules by quantitative reverse transcriptase polymerase chain reaction was determined in normal brain tissue (Norm), in the peritumoral brain tissue of glioblastoma (peri-GBM) and of intracerebral adenocarcinoma metastasis (peri-Met). To evaluate the translational expression of the investigated molecules protein levels were determined by targeted proteomic methods.

RESULTS

Establishing the invasion pattern of the investigated tissue samples 8 molecules showed concordant difference at mRNA and protein levels in the peri-GBM and peri-Met, 11 molecules in the peri-Met and normal brain and 12 in the peri-GBM and normal brain comparison.

CONCLUSION

Our results bring some ECM molecules into focus that probably play key role in arresting tumour cell invasion around the metastatic tumour, and also in the lack of impeding tumour cell migration in case of glioblastoma.

Invasion and anti-invasion research of glioma cells in an improved model of organotypic brain slice culture

AIMS AND BACKGROUND

Although glioblastomas infiltrate diffusely into adjacent brain, it is difficult to unequivocally identify the solitary invading glioma cell. It is necessary to develop coculture models to study the motility of glioma cells, and to monitor the cellular morphology, movement direction, migration area and invasion rate.

METHODS

Cerebral slices were cultured on Millicell-CM membrane inserts in a petri dish. The neuronal viability and organizational structure of the brain sections were well maintained by experimental verification. C6 cell clones with persistent enhanced green fluorescent protein (EGFP) expression were established. EGFP-expressing glioma cells were cultured to form aggregates, which were implanted on the brain slices. The invasion area and migration rates of C6 cells on brain slices were measured. We evaluated the invasion area and depth after C6 cells were treated with the Rac1 inhibitor NSC23766.

RESULTS

We successfully established the glioma cell-brain slice coculture model. In coculture, the average migration rate of C6 glioma cells within brain slices reached 11.36-15.27 μm/hour. The polarity of C6 glioma cells was parallel to the white matter tracts after 7 days. The invasive ability of C6 cells (depth: 105.3 ± 10.3 μm) treated with NSC23766 was weakened compared with the control group (depth: 198 ± 9.2 μm) within the white matter of brain slices (t = 16.26, p&lt;0.05).

CONCLUSIONS

We developed the model to analyze the invasion features of glioma cells. The significant suppression of glioma cell invasion by NSC23766 in brain slices indicates that anti-Rac1 treatment may represent an important future therapeutic strategy for glioblastoma.

In vivo modeling of malignant glioma: the road to effective therapy

Despite an increased emphasis on developing new therapies for malignant gliomas, they remain among the most intractable tumors faced today as they demonstrate a remarkable ability to evade current treatment strategies. Numerous candidate treatments fail at late stages, often after showing promising preclinical results. This disconnect highlights the continued need for improved animal models of glioma, which can be used to both screen potential targets and authentically recapitulate the human condition. This review examines recent developments in the animal modeling of glioma, from more established rat models to intriguing new systems using Drosophila and zebrafish that set the stage for higher throughput studies of potentially useful targets. It also addresses the versatility of mouse modeling using newly developed techniques recreating human protocols and sophisticated genetically engineered approaches that aim to characterize the biology of gliomagenesis. The use of these and future models will elucidate both new targets and effective combination therapies that will impact on disease management.

Nanosurgical resection of malignant brain tumors: beyond the cutting edge

Advances in surgical procedures and improvements in patient outcomes have resulted from applications of new technologies in the operating room over the past three decades. All surgeons would be excited about the possibilities of improving their resections of tumors for patients with cancer if a new technology were introduced to facilitate this. In this issue of ACS Nano, Karabeber et al. use a hand-held Raman scanner to probe the completeness of resection of glioblastoma multiforme (GBM), the most malignant brain cancer, in a genetically engineered mouse model. They show that the hand-held scanner could accurately detect gold-silica surface-enhanced Raman scattering nanoparticles embedded within the GBM, resulting in a complete tumor resection. In this Perspective, we review potential applications of nanotechnologies to neurosurgery and describe how new systems, such as the one described in this issue, may be brought closer to the operating room through modifications in nanoparticle size, overcoming the obstacles presented by the blood-brain barrier, and functionalizing nanoparticle conjugates so that they reach their target at highest concentrations possible. Finally, with adaptations of the actual hand-held Raman scanner device itself, one can envision the day when "nanosurgical" procedures will be a part of the surgeon's armamentarium.

CNS macrophages and peripheral myeloid cells in brain tumours

Primary brain tumours (gliomas) initiate a strong host response and can contain large amounts of immune cells (myeloid cells) such as microglia and tumour-infiltrating macrophages. In gliomas the course of pathology is not only controlled by the genetic make-up of the tumour cells, but also depends on the interplay with myeloid cells in the tumour microenvironment. Especially malignant gliomas such as glioblastoma multiforme (GBM) are notoriously immune-suppressive and it is now evident that GBM cells manipulate myeloid cells to support tumour expansion. The protumorigenic effects of glioma-associated myeloid cells comprise a support for angiogenesis as well as tumour cell invasion, proliferation and survival. Different strategies for inhibiting the pathological functions of myeloid cells in gliomas are explored, and blocking the tropism of microglia/macrophages to gliomas or manipulating the signal transduction pathways for immune cell activation has been successful in pre-clinical models. Hence, myeloid cells are now emerging as a promising target for new adjuvant therapies for gliomas. However, it is also becoming evident that some myeloid-directed glioma therapies may only be beneficial for distinct subclasses of gliomas and that a more cell-type-specific manipulation of either microglia or macrophages may improve therapeutic outcomes.