Muscle-Derived Extracellular Vesicles Influence Motor Neuron Regeneration Accuracy

Muscle-specific Bet1L knockdown induces neuromuscular denervation, motor neuron degeneration, and motor dysfunction in a rat model of familial ALS

Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by specific loss of motor neurons in the spinal cord and brain stem. Although ALS has historically been characterized as a motor neuron disease, there is evidence that motor neurons degenerate in a retrograde manner, beginning in the periphery at the neuromuscular junctions (NMJs) and skeletal muscle. We recently reported a vesicle trafficking protein Bet1L (Bet1 Golgi Vesicular Membrane Trafficking Protein Like) as a new molecule possibly linked to NMJ degeneration in ALS. In this study, we tested the hypothesis that Bet1L gene silencing in skeletal muscle could influence NMJ integrity, motor neuron function, and survival in a rat model of familial ALS (SOD1G93A transgenic). Small interfering RNA (siRNA) targeting the Bet1L gene was injected on a weekly basis into the hindlimb muscle of pre-symptomatic ALS and wild-type (WT) rats. After 3 weeks, intramuscular Bet1L siRNA injection significantly increased the number of denervated NMJs in the injected muscle. Bet1L knockdown decreased motor neuron size in the lumbar spinal cord, which innervated the siRNA-injected hindlimb. Impaired motor function was identified in the hindlimbs of Bet1L siRNA-injected rats. Notably, the effects of Bet1L knockdown on NMJ and motor neuron degeneration were more significant in ALS rats when compared to WT rats. Together, Bet1L knockdown induces denervation of NMJs, but also this knockdown accelerates the disease progression in ALS. Our results provide new evidence to support the potential roles of Bet1L as a key molecule in NMJ maintenance and ALS pathogenesis.

Utilization of Cannabidiol in Post-Organ-Transplant Care

Cannabidiol (CBD) is one of the major phytochemical constituents of cannabis, Cannabis sativa, widely recognized for its therapeutic potential. While cannabis has been utilized for medicinal purposes since ancient times, its psychoactive and addictive properties led to its prohibition in 1937, with only the medical use being reauthorized in 1998. Unlike tetrahydrocannabinol (THC), CBD lacks psychoactive and addictive properties, yet the name that suggests its association with cannabis has significantly contributed to its public visibility. CBD exhibits diverse pharmacological properties, most notably anti-inflammatory effects. Additionally, it interacts with key drug-metabolizing enzyme families, including cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT), which mediate phase I and phase II metabolism, respectively. By binding to these enzymes, CBD can inhibit the metabolism of co-administered drugs, which can potentially enhance their toxicity or therapeutic effects. Mild to moderate adverse events associated with CBD use have been reported. Advances in chemical formulation techniques have recently enabled strategies to minimize these effects. This review provides an overview of CBD, covering its historical background, recent clinical trials, adverse event profiles, and interactions with molecular targets such as receptors, channels, and enzymes. We particularly emphasize the mechanisms underlying its anti-inflammatory effects and interaction with drugs relevant to organ transplantation. Finally, we explore recent progress in the chemical formulation of CBD in order to enhance its bioavailability, which will enable decreasing the dose to use and increase its safety and efficacy.

Muscle-derived extracellular vesicles mediate crosstalk between skeletal muscle and other organs

Skeletal muscle (SKM) has crucial roles in locomotor activity and posture within the body and also functions have been recognized as an actively secretory organ. Numerous bioactive molecules are secreted by SKM and transported by extracellular vesicles (EVs), a novel class of mediators of communication between cells and organs that contain various types of cargo molecules including lipids, proteins and nucleic acids. SKM-derived EVs (SKM-EVs) are intercellular communicators with significant roles in the crosstalk between SKM and other organs. In this review, we briefly describe the biological characteristics, composition, and uptake mechanisms of EVs, particularly exosomes, comprehensively summarize the regulatory effects of SKM-EVs on the function of, which include myogenesis, muscle repair and regeneration, as well as metabolic regulation. Furthermore, we explore the impact of SKM- EVs on various organs including bone, the cardiovascular system, adipose tissue, and nervous system. As emerging evidence suggests that SKM-EVs are involved in the development and regulation of type 2 diabetes (T2D), systemic inflammation, and other chronic diseases, we also highlight the potential of SKM-EVs as therapeutic targets and diagnostic biomarkers, emphasizing the need for further research to elucidate the complex mechanisms underlying intercellular communication in physiological and pathological contexts.

Analysis of translatomic changes in the Ubqln2P497S model of ALS reveals that motor neurons express muscle-associated genes in non-disease states

Introduction

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressively worsening motor symptoms that lead to eventual fatal paralysis. The number of gene mutations associated with ALS have increased dramatically in recent years, suggesting heterogeneity in the etiology of ALS and the need to develop new models of the disease that encompass these pathologies. In 2011, mutations in the UBQLN2 gene were identified in families with both ALS and frontotemporal dementia (FTD) and have since been linked to ubiquitinated TDP43 inclusion pathology. The involvement of UBQLN2 in ubiquitination and proteasome function suggests an important role in proteostasis, which is reported to be impaired in ALS.

Methods

A UBQLN2 mouse model was generated for the P497S mutation and recapitulates some of the motor symptoms of ALS. We utilized ribosomal profiling followed by mRNA sequencing of associated transcripts to characterize gene expression changes of motor neurons in the Ubqln2P497S model and evaluated ALS phenotypes in these animals.

Results

At 12 months of age, we observed reduced motor neuron survival and neuromuscular junction denervation in these mice that translated into motor deficits observed in locomotor behavioral trials. The sequencing of motor neuron transcripts revealed that Wnt pathways and muscle-related transcripts were downregulated in Ubqln2P497S mice, while metabolic pathways were upregulated.

Discussion

Surprisingly, genes often reported to be muscle-specific, such as Desmin and Acta1, were expressed in motor neurons and were dramatically downregulated in symptomatic Ubqln2P497S mice. The expression of muscle transcripts by motor neurons suggests their potentially supportive role in skeletal muscle maintenance.

New perspectives of the role of skeletal muscle derived extracellular vesicles in the pathogenesis of amyotrophic lateral sclerosis: the 'dying back' hypothesis

Amyotrophic lateral sclerosis (ALS), is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord, and is characterized by muscle weakness, paralysis and ultimately, respiratory failure. The exact causes of ALS are not understood, though it is believed to combine genetic and environmental factors. Until now, it was admitted that motor neurons (MN) in the brain and spinal cord degenerate, leading to muscle weakness and paralysis. However, as ALS symptoms typically begin with muscle weakness or stiffness, a new hypothesis has recently emerged to explain the development of the pathology, that is, the 'dying back hypothesis', suggesting that this degeneration starts at the connections between MN and muscles, resulting in the loss of muscle function. Over time, this damage extends along the length of the MN, ultimately affecting their cell bodies in the spinal cord and brain. While the dying back hypothesis provides a potential framework for understanding the progression of ALS, the exact mechanisms underlying the disease remain complex and not fully understood. In this review, we are positioning the role of extracellular vesicles as new actors in ALS development.

Possible Combinatorial Utilization of Phytochemicals and Extracellular Vesicles for Wound Healing and Regeneration

Organ and tissue damage can result from injury and disease. How to facilitate regeneration from damage has been a topic for centuries, and still, we are trying to find agents to use for treatments. Two groups of biological substances are known to facilitate wound healing. Phytochemicals with bioactive properties form one group. Many phytochemicals have anti-inflammatory effects and enhance wound healing. Recent studies have described their effects at the gene and protein expression levels, highlighting the receptors and signaling pathways involved. The extremely large number of phytochemicals and the multiple types of receptors they activate suggest a broad range of applicability for their clinical use. The hydrophobic nature of many phytochemicals and the difficulty with chemical stabilization have been a problem. Recent developments in biotechnology and nanotechnology methods are enabling researchers to overcome these problems. The other group of biological substances is extracellular vesicles (EVs), which are now known to have important biological functions, including the improvement of wound healing. The proteins and nanoparticles contained in mammalian EVs as well as the specificity of the targets of microRNAs included in the EVs are becoming clear. Plant-derived EVs have been found to contain phytochemicals. The overlap in the wound-healing capabilities of both phytochemicals and EVs and the differences in their nature suggest the possibility of a combinatorial use of the two groups, which may enhance their effects.

Exploring the Role of Extracellular Vesicles in Skeletal Muscle Regeneration

Skeletal muscle regeneration entails a multifaceted process marked by distinct phases, encompassing inflammation, regeneration, and remodeling. The coordination of these phases hinges upon precise intercellular communication orchestrated by diverse cell types and signaling molecules. Recent focus has turned towards extracellular vesicles (EVs), particularly small EVs, as pivotal mediators facilitating intercellular communication throughout muscle regeneration. Notably, injured muscle provokes the release of EVs originating from myofibers and various cell types, including mesenchymal stem cells, satellite cells, and immune cells such as M2 macrophages, which exhibit anti-inflammatory and promyogenic properties. EVs harbor a specific cargo comprising functional proteins, lipids, and nucleic acids, including microRNAs (miRNAs), which intricately regulate gene expression in target cells and activate downstream pathways crucial for skeletal muscle homeostasis and repair. Furthermore, EVs foster angiogenesis, muscle reinnervation, and extracellular matrix remodeling, thereby modulating the tissue microenvironment and promoting effective tissue regeneration. This review consolidates the current understanding on EVs released by cells and damaged tissues throughout various phases of muscle regeneration with a focus on EV cargo, providing new insights on potential therapeutic interventions to mitigate muscle-related pathologies.

Muscle stem cell niche dynamics during muscle homeostasis and regeneration

The process of skeletal muscle regeneration involves a coordinated interplay of specific cellular and molecular interactions within the injury site. This review provides an overview of the cellular and molecular components in regenerating skeletal muscle, focusing on how these cells or molecules in the niche regulate muscle stem cell functions. Dysfunctions of muscle stem cell-to-niche cell communications during aging and disease will also be discussed. A better understanding of how niche cells coordinate with muscle stem cells for muscle repair will greatly aid the development of therapeutic strategies for treating muscle-related disorders.

Motor neurons and endothelial cells additively promote development and fusion of human iPSC-derived skeletal myocytes

BACKGROUND

Neurovascular cells have wide-ranging implications on skeletal muscle biology regulating myogenesis, maturation, and regeneration. Although several in vitro studies have investigated how motor neurons and endothelial cells interact with skeletal myocytes independently, there is limited knowledge about the combined effect of neural and vascular cells on muscle maturation and development.

METHODS

Here, we report a triculture system comprising human-induced pluripotent stem cell (iPSC)-derived skeletal myocytes, human iPSC-derived motor neurons, and primary human endothelial cells maintained under controlled media conditions. Briefly, iPSCs were differentiated to generate skeletal muscle progenitor cells (SMPCs). These SMPCs were seeded at a density of 5 × 104 cells/well in 12-well plates and allowed to differentiate for 7 days before adding iPSC-derived motor neurons at a concentration of 0.5 × 104 cells/well. The neuromuscular coculture was maintained for another 7 days in coculture media before addition of primary human umbilical vein endothelial cells (HUVEC) also at 0.5 × 104 cells/well. The triculture was maintained for another 7 days in triculture media comprising equal portions of muscle differentiation media, coculture media, and vascular media. Extensive morphological, genetic, and molecular characterization was performed to understand the combined and individual effects of neural and vascular cells on skeletal muscle maturation.

RESULTS

We observed that motor neurons independently promoted myofiber fusion, upregulated neuromuscular junction genes, and maintained a molecular niche supportive of muscle maturation. Endothelial cells independently did not support myofiber fusion and downregulated expression of LRP4 but did promote expression of type II specific myosin isoforms. However, neurovascular cells in combination exhibited additive increases in myofiber fusion and length, enhanced production of Agrin, along with upregulation of several key genes like MUSK, RAPSYN, DOK-7, and SLC2A4. Interestingly, more divergent effects were observed in expression of genes like MYH8, MYH1, MYH2, MYH4, and LRP4 and secretion of key molecular factors like amphiregulin and IGFBP-4.

CONCLUSIONS

Neurovascular cells when cultured in combination with skeletal myocytes promoted myocyte fusion with concomitant increase in expression of various neuromuscular genes. This triculture system may be used to gain a deeper understanding of the effects of the neurovascular niche on skeletal muscle biology and pathophysiology.

The human neurosecretome: extracellular vesicles and particles (EVPs) of the brain for intercellular communication, therapy, and liquid-biopsy applications

Emerging evidence suggests that brain derived extracellular vesicles (EVs) and particles (EPs) can cross blood-brain barrier and mediate communication among neurons, astrocytes, microglial, and other cells of the central nervous system (CNS). Yet, a complete understanding of the molecular landscape and function of circulating EVs & EPs (EVPs) remain a major gap in knowledge. This is mainly due to the lack of technologies to isolate and separate all EVPs of heterogeneous dimensions and low buoyant density. In this review, we aim to provide a comprehensive understanding of the neurosecretome, including the extracellular vesicles that carry the molecular signature of the brain in both its microenvironment and the systemic circulation. We discuss the biogenesis of EVPs, their function, cell-to-cell communication, past and emerging isolation technologies, therapeutics, and liquid-biopsy applications. It is important to highlight that the landscape of EVPs is in a constant state of evolution; hence, we not only discuss the past literature and current landscape of the EVPs, but we also speculate as to how novel EVPs may contribute to the etiology of addiction, depression, psychiatric, neurodegenerative diseases, and aid in the real time monitoring of the "living brain". Overall, the neurosecretome is a concept we introduce here to embody the compendium of circulating particles of the brain for their function and disease pathogenesis. Finally, for the purpose of inclusion of all extracellular particles, we have used the term EVPs as defined by the International Society of Extracellular Vesicles (ISEV).

The Cellular and Molecular Signature of ALS in Muscle

Amyotrophic lateral sclerosis is a disease affecting upper and lower motor neurons. Although motor neuron death is the core event of ALS pathology, it is increasingly recognized that other tissues and cell types are affected in the disease, making potentially major contributions to the occurrence and progression of pathology. We review here the known cellular and molecular characteristics of muscle tissue affected by ALS. Evidence of toxicity in skeletal muscle tissue is considered, including metabolic dysfunctions, impaired proteostasis, and deficits in muscle regeneration and RNA metabolism. The role of muscle as a secretory organ, and effects on the skeletal muscle secretome are also covered, including the increase in secretion of toxic factors or decrease in essential factors that have consequences for neuronal function and survival.

Role of exosomes in the pathogenesis, diagnosis, and treatment of central nervous system diseases

Central nervous system (CNS) diseases, such as multiple sclerosis, Alzheimer's disease (AD), and Parkinson’s disease (PD), affect millions of people around the world. Great efforts were put in disease related research, but few breakthroughs have been made in the diagnostic and therapeutic approaches. Exosomes are cell-derived extracellular vesicles containing diverse biologically active molecules secreted by their cell of origin. These contents, including nucleic acids, proteins, lipids, amino acids, and metabolites, can be transferred between different cells, tissues, or organs, regulating various intercellular cross-organ communications and normal and pathogenic processes. Considering that cellular environment and cell state strongly impact the content and uptake efficiency of exosomes, their detection in biological fluids and content composition analysis potentially offer a multicomponent diagnostic readout of several human diseases. Recently, studies have found that aberrant secretion and content of exosomes are closely related to the pathogenesis of CNS diseases. Besides, loading natural cargoes, exosomes can deliver drugs cross the blood brain barrier, making them emerging candidates of biomarkers and therapeutics for CNS diseases. In this review, we summarize and discuss the advanced research progress of exosomes in the pathological processes of several CNS diseases in regarding with neuroinflammation, CNS repair, and pathological protein aggregation. Moreover, we propose the therapeutic strategies of applying exosomes to the diagnosis, early detection, and treatment of CNS diseases.

The Role of Extracellular Vesicles in Cancer-Nerve Crosstalk of the Peripheral Nervous System

Although the pathogenic operations of cancer–nerve crosstalk (e.g., neuritogenesis, neoneurogensis, and perineural invasion—PNI) in the peripheral nervous system (PNS) during tumorigenesis, as well as the progression of all cancer types is continuing to emerge as an area of unique scientific interest and study, extensive, wide-ranging, and multidisciplinary investigations still remain fragmented and unsystematic. This is especially so in regard to the roles played by extracellular vesicles (EVs), which are lipid bilayer-enclosed nano- to microsized particles that carry multiple-function molecular cargos, facilitate intercellular communication in diverse processes. Accordingly, the biological significance of EVs has been greatly elevated in recent years, as there is strong evidence that they could contribute to important and possibly groundbreaking diagnostic and therapeutic innovations. This can be achieved and the pace of discoveries accelerated through cross-pollination from existing knowledge and studies regarding nervous system physiology and pathology, as well as thoroughgoing collaborations between oncologists, neurobiologists, pathologists, clinicians, and researchers. This article offers an overview of current and recent past investigations on the roles of EVs in cancer–nerve crosstalk, as well as in neural development, physiology, inflammation, injury, and regeneration in the PNS. By highlighting the mechanisms involved in physiological and noncancerous pathological cellular crosstalk, we provide hints that may inspire additional translational studies on cancer–nerve interplay.

The Neurotoxicity of Vesicles Secreted by ALS Patient Myotubes Is Specific to Exosome-Like and Not Larger Subtypes

Extracellular vesicles can mediate communication between tissues, affecting the physiological conditions of recipient cells. They are increasingly investigated in Amyotrophic Lateral Sclerosis, the most common form of Motor Neurone Disease, as transporters of misfolded proteins including SOD1, FUS, TDP43, or other neurotoxic elements, such as the dipeptide repeats resulting from C9orf72 expansions. EVs are classified based on their biogenesis and size and can be separated by differential centrifugation. They include exosomes, released by the fusion of multivesicular bodies with the plasma membrane, and ectosomes, also known as microvesicles or microparticles, resulting from budding or pinching of the plasma membrane. In the current study, EVs were obtained from the myotube cell culture medium of ALS patients or healthy controls. EVs of two different sizes, separating at 20,000 or 100,000 g, were then compared in terms of their effects on recipient motor neurons, astrocytes, and myotubes. Compared to untreated cells, the smaller, exosome-like vesicles of ALS patients reduced the survival of motor neurons by 31% and of myotubes by 18%, decreased neurite length and branching, and increased the proportion of stellate astrocytes, whereas neither those of healthy subjects, nor larger EVs of ALS or healthy subjects, had such effects.

Extracellular vesicles and their role in peripheral nerve regeneration

Peripheral nerve injuries often result in sensory and motor dysfunction in respective parts of the body. Regeneration after peripheral nerve injuries is a complex process including the differentiation of Schwann cells, recruiting of macrophages, blood vessel growth and axonal regrowth. Extracellular vesicles (EVs) are considered to play a pivotal role in intercellular communication and transfer of biological information. Specifically, their bioactivity and ability to deliver cargos of various types of nucleic acids and proteins have made them a potential vehicle for neurotherapeutics. However, production, characterization, dosage and targeted delivery of EVs still pose challenges for the clinical translation of EV therapeutics. This review summarizes the current knowledge of EVs in the context of the healthy and injured peripheral nerve and addresses novel concepts for modification of EVs as therapeutic agents for peripheral nerve regeneration.

Potential Roles of Muscle-Derived Extracellular Vesicles in Remodeling Cellular Microenvironment: Proposed Implications of the Exercise-Induced Myokine, Irisin

Extracellular vesicles (EVs) have emerged as key players of intercellular communication and mediate crosstalk between tissues. Metastatic tumors release tumorigenic EVs, capable of pre-conditioning distal sites for organotropic metastasis. Growing evidence identifies muscle cell-derived EVs and myokines as potent mediators of cellular differentiation, proliferation, and metabolism. Muscle-derived EVs cargo myokines and other biological modulators like microRNAs, cytokines, chemokines, and prostaglandins hence, are likely to modulate the remodeling of niches in vital sites, such as liver and adipose tissues. Despite the scarcity of evidence to support a direct relationship between muscle-EVs and cancer metastasis, their indirect attribution to the regulation of niche remodeling and the establishment of pre-metastatic homing niches can be put forward. This hypothesis is supported by the role of muscle-derived EVs in findings gathered from other pathologies like inflammation and metabolic disorders. In this review, we present and discuss studies that evidently support the potential roles of muscle-derived EVs in the events of niche pre-conditioning and remodeling of metastatic tumor microenvironment. We highlight the potential contributions of the integrin-mediated interactions with an emerging myokine, irisin, to the regulation of EV-driven microenvironment remodeling in tumor metastasis. Further research into muscle-derived EVs and myokines in cancer progression is imperative and may hold promising contributions to advance our knowledge in the pathophysiology, progression and therapeutic management of metastatic cancers.

Extracellular vesicles from skin precursor-derived Schwann cells promote axonal outgrowth and regeneration of motoneurons via Akt/mTOR/p70S6K pathway

Background

Skin precursor-derived Schwann cells (SKP-SCs) have been shown to benefit the recovery of spinal cord injury (SCI) and peripheral nerve injury (PNI) with motor dysfunction. However, the effect of extracellular vesicles (EVs) from SKP-SCs responsible for neuroregeneration remains unknown.

Methods

Based on the obtainment and identification of rat SKP-SCs and their derived EVs, the primary rat injury model of motoneurons resulting from axotomy in vitro or nerve crush in vivo, as well as the secondary rat ischemic hypoxic injury model of motoneuron exposure to oxygen-glucose-deprivation (OGD) in vitro, were treated with EVs from skin precursor-derived Schwann cells (SKP-SC-EVs), respectively. Then, the axonal outgrowth and regrowth was observed and compared, and cell viability as well as the protein kinase B/mammalian target of rapamycin/p70 S6 kinase (Akt/mTOR/p70S6K) signaling pathway was detected, moreover, rapamycin (an mTOR inhibitor) was used to further reveal the underlying molecular mechanism.

Results

The internalization of SKP-SC-EVs by neuronal cells was identified in vitro and in vivo. Besides the pro-axonal outgrowth effect of SKP-SC-EVs, prospectively, the treatment of OGD-injured motoneurons with SKP-SC-EVs potentiated the restoration of neuronal viability and axonal regrowth. Furthermore, the axotomizing injury could be improved with SKP-SC-EVs treatment in vitro and in vivo. Finally, it was shown that the application of SKP-SC-EVs could activate the Akt/mTOR/p70S6K signaling pathway that can be abolished by rapamycin.

Conclusions

In summary, the addition of SKP-SC-EVs could regulate the cell growth and death signaling pathway mediated by Akt/mTOR/p70S6K, owing to the transmission of cargos in EVs to damaged motoneurons, which leads to axonal regrowth and neuronal resurrection. Thus, SKP-SC-EVs treatment could be a novel promising strategy for improving the axonal outgrowth and regeneration of motoneurons.

Caspase-3 Cleaves Extracellular Vesicle Proteins During Auditory Brainstem Development

Sound localization requires extremely precise development of auditory brainstem circuits, the molecular mechanisms of which are largely unknown. We previously demonstrated a novel requirement for non-apoptotic activity of the protease caspase-3 in chick auditory brainstem development. Here, we used mass spectrometry to identify proteolytic substrates of caspase-3 during chick auditory brainstem development. These auditory brainstem caspase-3 substrates were enriched for proteins previously shown to be cleaved by caspase-3, especially in non-apoptotic contexts. Functional annotation analysis revealed that our caspase-3 substrates were also enriched for proteins associated with several protein categories, including proteins found in extracellular vesicles (EVs), membrane-bound nanoparticles that function in intercellular communication. The proteome of EVs isolated from the auditory brainstem was highly enriched for our caspase-3 substrates. Additionally, we identified two caspase-3 substrates with known functions in axon guidance, namely Neural Cell Adhesion Molecule (NCAM) and Neuronal-glial Cell Adhesion Molecule (Ng-CAM), that were found in auditory brainstem EVs and expressed in the auditory pathway alongside cleaved caspase-3. Taken together, these data suggest a novel developmental mechanism whereby caspase-3 influences auditory brainstem circuit formation through the proteolytic cleavage of extracellular vesicle (EV) proteins.

Next Stage Approach to Tissue Engineering Skeletal Muscle

Large-scale muscle injury in humans initiates a complex regeneration process, as not only the muscular, but also the vascular and neuro-muscular compartments have to be repaired. Conventional therapeutic strategies often fall short of reaching the desired functional outcome, due to the inherent complexity of natural skeletal muscle. Tissue engineering offers a promising alternative treatment strategy, aiming to achieve an engineered tissue close to natural tissue composition and function, able to induce long-term, functional regeneration after in vivo implantation. This review aims to summarize the latest approaches of tissue engineering skeletal muscle, with specific attention toward fabrication, neuro-angiogenesis, multicellularity and the biochemical cues that adjuvate the regeneration process.

Extracellular Vesicles as Innovative Tool for Diagnosis, Regeneration and Protection against Neurological Damage

Extracellular vesicles (EVs) have recently attracted a great deal of interest as they may represent a new biosignaling paradigm. According to the mode of biogenesis, size and composition, two broad categories of EVs have been described, exosomes and microvesicles. EVs have been shown to carry cargoes of signaling proteins, RNA species, DNA and lipids. Once released, their content is selectively taken up by near or distant target cells, influencing their behavior. Exosomes are involved in cell–cell communication in a wide range of embryonic developmental processes and in fetal–maternal communication. In the present review, an outline of the role of EVs in neural development, regeneration and diseases is presented. EVs can act as regulators of normal homeostasis, but they can also promote either neuroinflammation/degeneration or tissue repair in pathological conditions, depending on their content. Since EV molecular cargo constitutes a representation of the origin cell status, EVs can be exploited in the diagnosis of several diseases. Due to their capability to cross the blood–brain barrier (BBB), EVs not only have been suggested for the diagnosis of central nervous system disorders by means of minimally invasive procedures, i.e., “liquid biopsies”, but they are also considered attractive tools for targeted drug delivery across the BBB. From the therapeutic perspective, mesenchymal stem cells (MSCs) represent one of the most promising sources of EVs. In particular, the neuroprotective properties of MSCs derived from the dental pulp are here discussed.