Nerve Tissue Repair Research Articles

Endothelin-1 decreases the expression of Ephrin-A and B subtypes in cultured rat astrocytes through ETB receptors

Ephrin family proteins are cell surface molecules that regulate several cellular functions through cell-cell interactions. During nervous tissue repair after injury, the expression of ephrin subtypes in astrocytes is altered, affecting the axonal elongation and migration of neuronal precursors. However, the mechanism regulating the expression of ephrin subtypes in astrocytes has not been investigated. Herein, we studied the effects of endothelin-1 (ET-1) on the expression of ephrin subtypes in cultured rat astrocytes. Our results showed that ET-1 (100 nM) treatment for 1−24 h reduced the expression of ephrin-A2, -A4, -B2, and -B3 mRNA and protein in astrocytes, whereas the expression of ephrin-A1, -A3, -A5, and -B1 mRNA were not affected. Sarafotoxin S6c, a selective ETB receptor agonist, decreased the expression of ephrin-A2, -A4, -B2, and -B3 in cultured astrocytes. The decrease in ephrin-A2, -A4, -B2, and -B3 expression by ET-1 treatment was reduced in the presence of BQ788, an ETB receptor antagonist, while FR139317, an ETA receptor antagonist, had no effects. These results suggest that ET-1 is a signaling molecule that downregulates ephrin-A2, -A4, -B2, and -B3 expression in astrocytes.

Repair of injured spinal cord using platelet-rich plasma- and endometrial stem cells-loaded chitosan scaffolds

Engineering scaffolds that can not only act as a vehicle for stem cell delivery but also support axon regeneration, may significantly improve the treatment outcome of spinal cord injury (SCI). In this study, we developed chitosan scaffold containing human endometrial stem cells (hEnSCs) and platelet-rich plasma (PRP) to provide a controlled environment for facilitating cell ingrowth and differentiation and also to persuade axon nervous tissue repair. The results showed that 80 µL PRP-loaded chitosan scaffold has excellent hEnSCs viability and can promote the regeneration of nerve fibers and angiogenesis and prevent the formation of scar tissue in the repair of SCI.

Microglia influence host defense, disease, and repair following murine coronavirus infection of the central nervous system.

The present study examines functional contributions of microglia in host defense, demyelination, and remyelination following infection of susceptible mice with a neurotropic coronavirus. Treatment with PLX5622, an inhibitor of colony stimulating factor 1 receptor (CSF1R) that efficiently depletes microglia, prior to infection of the central nervous system (CNS) with the neurotropic JHM strain of mouse hepatitis virus (JHMV) resulted in increased mortality compared with control mice that correlated with impaired control of viral replication. Single cell RNA sequencing (scRNASeq) of CD45+ cells isolated from the CNS revealed that PLX5622 treatment resulted in muted CD4+ T cell activation profile that was associated with decreased expression of transcripts encoding MHC class II and CD86 in macrophages but not dendritic cells. Evaluation of spinal cord demyelination revealed a marked increase in white matter damage in PLX5622‐treated mice that corresponded with elevated expression of transcripts encoding disease‐associated proteins Osteopontin (Spp1), Apolipoprotein E (Apoe), and Triggering receptor expressed on myeloid cells 2 (Trem2) that were enriched within macrophages. In addition, PLX5622 treatment dampened expression of Cystatin F (Cst7), Insulin growth factor 1 (Igf1), and lipoprotein lipase (Lpl) within macrophage populations which have been implicated in promoting repair of damaged nerve tissue and this was associated with impaired remyelination. Collectively, these findings argue that microglia tailor the CNS microenvironment to enhance control of coronavirus replication as well as dampen the severity of demyelination and influence repair.

Elektroeğrilmiş Nanoliflerin Sinir Kılavuz Kanalı Uygulamalarında Kullanımı

Therapeutic methods developed for the repair of damaged nerves often do not provide adequate recovery. Along with the application of tissue engineering principles in the nerve tissue regeneration, many researches have been made and are still in progress to develop an ideal nerve guide channel. Promising studies are ongoing for the use of nano-sized fibrous scaffolds for nerve tissue repair, which can mimic the topography of the natural extracellular matrix. With the electrospinning method, nanofibers can be produced and the nanofiber nerve channels enabling neuron development and regrowth can be placed in the nerve gap that has lost its function. This study summarizes nerve tissue engineering strategies and clinical practices, including biomaterials and tissue scaffold production techniques to produce a structure that allows neurons to adhere, multiply, and eventually form nerves.

The effect of a nanofiber-hydrogel composite on neural tissue repair and regeneration in the contused spinal cord

An injury to the spinal cord causes long-lasting loss of nervous tissue because endogenous nervous tissue repair and regeneration at the site of injury is limited. We engineered an injectable nanofiber-hydrogel composite (NHC) with interfacial bonding to provide mechanical strength and porosity and examined its effect on repair and neural tissue regeneration in an adult rat model of spinal cord contusion. At 28 days after treatment with NHC, the width of the contused spinal cord segment was 2-fold larger than in controls. With NHC treatment, tissue in the injury had a 2-fold higher M2/M1 macrophage ratio, 5-fold higher blood vessel density, 2.6-fold higher immature neuron presence, 2.4-fold higher axon density, and a similar glial scar presence compared with controls. Spared nervous tissue volume in the contused segment and hind limb function was similar between groups. Our findings indicated that NHC provided mechanical support to the contused spinal cord and supported pro-regenerative macrophage polarization, angiogenesis, axon growth, and neurogenesis in the injured tissue without any exogenous factors or cells. These results motivate further optimization of the NHC and delivery protocol to fully translate the potential of the unique properties of the NHC for treating spinal cord injury.

Recent Advances in Carbon Nanotubes for Nervous Tissue Regeneration

Regenerative medicine has taken advantage of several nanomaterials for reparation of diseased or damaged tissues in the nervous system involved in memory, cognition, and movement. Electrical, thermal, mechanical, and biocompatibility aspects of carbon-based nanomaterials (nanotubes, graphene, fullerenes, and their derivatives) make them suitable candidates to drive nerve tissue repair and stimulation. This review article focuses on key recent advances on the use of carbon nanotube- (CNT-) based technologies on nerve tissue engineering, outlining how neurons interact with CNT interfaces for promoting neuronal differentiation, growth and network reconstruction. CNTs still represent strong candidates for use in therapies of neurodegenerative pathologies and spinal cord injuries.

Protective effect of Tβ4 on central nervous system tissues and its developmental prospects

Tissue repair and regeneration in the central nervous system (CNS) remains a serious medical problem. CNS diseases such as traumatic and neurological brain injuries have a high mortality and disability rate, thereby bringing a considerable amount of economic burden to society and families. How to treat traumatic and neurological brain injuries has always been a serious issue faced by neurosurgeons. The global incidence of traumatic and neurological brain injuries has gradually increased and become a global challenge. Thymosin β4 (Tβ4) is the main G-actin variant molecule in eukaryotic cells. During the development of the CNS, Tβ4 regulates neurogenesis, tangential expansion, tissue growth, and cerebral hemisphere folding. In addition, Tβ4 has anti-apoptotic and anti-inflammatory properties. It promotes angiogenesis, wound healing, stem/progenitor cell differentiation, and other characteristics of cell migration and survival, providing a scientific basis for the repair and regeneration of injured nerve tissue. This review provides evidence to support the role of Tβ4 in the protection and repair of nervous tissue in CNS diseases, especially with the potential to control brain inflammatory processes, and thus open up new therapeutic applications for a series of neurodegenerative diseases.

Pericytes in Microvessels: From "Mural" Function to Brain and Retina Regeneration.

Pericytes are branched cells located in the wall of capillary blood vessels that are found throughout the body, embedded within the microvascular basement membrane and wrapping endothelial cells, with which they establish a strong physical contact. Pericytes regulate angiogenesis, vessel stabilization, and contribute to the formation of both the blood-brain and blood-retina barriers by Angiopoietin-1/Tie-2, platelet derived growth factor (PDGF) and transforming growth factor (TGF) signaling pathways, regulating pericyte-endothelial cell communication. Human pericytes that have been cultured for a long period give rise to multilineage progenitor cells and exhibit mesenchymal stem cell (MSC) features. We focused our attention on the roles of pericytes in brain and ocular diseases. In particular, pericyte involvement in brain ischemia, brain tumors, diabetic retinopathy, and uveal melanoma is described. Several molecules, such as adenosine and nitric oxide, are responsible for pericyte shrinkage during ischemia-reperfusion. Anti-inflammatory molecules, such as IL-10, TGFβ, and MHC-II, which are increased in glioblastoma-activated pericytes, are responsible for tumor growth. As regards the eye, pericytes play a role not only in ocular vessel stabilization, but also as a stem cell niche that contributes to regenerative processes in diabetic retinopathy. Moreover, pericytes participate in melanoma cell extravasation and the genetic ablation of the PDGF receptor reduces the number of pericytes and aberrant tumor microvessel formation with important implications for therapy efficacy. Thanks to their MSC features, pericytes could be considered excellent candidates to promote nervous tissue repair and for regenerative medicine.

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.

L-tryptophan promotes the cheliped regeneration of Chinese mitten crab (Eriocheir sinensis) through melatonin, serotonin and dopamine involvement

It is particularly important to artificially promote limb regeneration of Eriocheir sinensis with high limb-impairment rate. This study was designed to evaluate the effects of dietary supplementation of L-tryptophan (L-trp) on cheliped regeneration. Through this study, we find that the dietary supplementation of 0.53% and 0.70% L-trp significantly increases limb regeneration rates over 14 d (P < .05). The expression of EcR-mRNA (ecdysteroid receptor) and Chi-mRNA (chitinase) are significantly upregulated with the dietary supplementation of 0.53% or 0.70% L-trp while the expression of MIH-mRNA (molt-inhibiting hormone) is significantly downregulated (P < .05). Moreover, digestive enzyme activities are significantly enhanced with dietary supplementation of 0.53% or 0.70% L-trp (P < .05). Further, dietary supplementation of L-trp significantly increases melatonin (MT) levels in eyestalks and L-trp levels in muscles of E. sinensis (P < .05). Interestingly, our study preliminarily explores the role of 5-HT and DA related receptors in the cheliped regeneration of E. sinensis. We find that dietary L-trp supplementation regulates the expression of 5-HT and DA-related receptors in digestive organs (hepatopancreas and intestines) and nervous tissues (cranial and thoracic ganglia), speculating that it may be involved in the improvement of digestion and absorption function and the regulation of nerve tissue repair during the cheliped regeneration of E. sinensis. Taken together, dietary supplementation of L-trp can promote limb regeneration by regulating regeneration-related gene expression and hepatopancreatic digestion in E. sinensis, which may be achieved by regulating MT levels and the binding of 5-HT and DA to corresponding receptors.

Chitosan-Gelatin-Polypyrrole Cryogel Matrix for Stem Cell Differentiation into Neural Lineage and Sciatic Nerve Regeneration in Peripheral Nerve Injury Model.

With the advances in tissue engineering and regenerative medicine, various approaches have been developed for peripheral nerve tissue repair and regeneration. In the current study, we have synthesized a cryogel matrix from chitosan and gelatin incorporated with polypyrrole for neural tissue regeneration. The three-dimensional (3-D) cryogel matrix was fabricated to mimic the in vivo microenvironment and analyzed for stem cell differentiation. Isolated bone marrow stem cells (BMSCs) cultured on a 3-D cryogel matrix differentiated into neural lineage on the basis of scaffold properties, in a co-culture system and by treatment with the spent media of Neuro 2a cells. To validate the cell-cell contact and BMSCs differentiation, scanning electron micrography and fluorescent imaging were done, which revealed the differentiation of the BMSCs. Immunostaining and gene expression analysis showed the BMSCs differentiation in all of the three cases studied. However, BMSCs in the co-culture system showed increased neurotransmitter levels of dopamine (34%) and acetylcholine (16%) with a respective concentration of 2.04 ± 0.03 ng/mL and 15.06 ± 0.19 pg/mL. Based on these properties, an in vivo study explored the potential of the synthesized cryogel in regeneration of a 1.5 cm nerve gap in the sciatic nerve of rats for a period of 12 weeks. The biocompatibility analysis showed that the scaffold did not induce any adverse immune response. Moreover, the walking track analysis and electrophysiological and immunostaining analyses revealed enhanced sciatic nerve regeneration in comparison to the negative control group. This study reveals the regenerative potential of the cryogel matrix for peripheral nerve regeneration.

Transplantation of BDNF Gene Recombinant Mesenchymal Stem Cells and Adhesive Peptide-modified Hydrogel Scaffold for Spinal Cord Repair.

Mesenchymal Stem Cells (MSCs) are promising candidates for nerve tissue engineering. Brain Derived Neurotrophic Factor (BDNF) secreted by MSCs can function to increase neural differentiation and relieve inflammation response. Gene transfection technology is an efficient strategy to increase the secretion levels of cytokines and enhance cellular functions. However, transfection and in vivo gene expression of environmentally sensitive stem cells have been one of the most challenging subjects due to the requirement in both safety and transfection efficiency. In this study, gene transfection technology was applied to prepare BDNF gene recombinant MSCs based on our previously reported liposomal vector ScreenFect® A. To improve cellular survival and gene expression after in situ implantation of MSCs, an adhesive peptide modified hydrogel scaffold was constructed using hyaluronic acid. The scaffold was optimized and modified with an adhesive peptide PPFLMLLKGSTR. The transfected MSCs exhibited improved cellular survival and sustained gene expression in the three-Dimentional (3D) scaffold in vitro. Compared to untransfected MSCs, gene recombinant MSCs effectively improved spinal tissue integrity, inhibited glial scar formation and alleviated inflammatory response. These effects were found discounted when cells were implanted without the scaffold. The study developed a promising implantation system for therapy of severe spinal cord injury and provided the first understanding of Screenfect® A about its functions on stem cell therapy for nerve tissue repair as well as three-dimentional gene expression.

Advances in 3D Bioprinting for Neural Tissue Engineering

AbstractCurrent therapies for nerve regeneration within injured tissues have had limited success due to complicated neural anatomy and inhibitory barriers in situ. Recent advancements in 3D bioprinting technologies have enabled researchers to develop novel 3D scaffolds with complex architectures in an effort to mitigate the challenges that beset reliable and defined neural tissue regeneration. Among several possible neuroregenerative treatment approaches that are being explored today, 3D bioprinted scaffolds have the unique advantage of being highly modifiable, which promotes greater resemblance to the native biological architecture of in vivo systems. This high architectural similarity between printed constructs and in vivo structures is thought to facilitate a greater capacity for repair of damaged nerve tissues. In this review, advances of several 3D bioprinting methods are introduced, including laser bioprinting, inkjet bioprinting, and extrusion‐based printing. In addition, the emergence of 4D printing is discussed, which adds a dimension of transformation over time to traditional 3D printing. Finally, an overview of emerging trends in advanced bioprinting materials is provided and their therapeutic potential for application in neural tissue regeneration is evaluated in both the central nervous system and the peripheral nervous system.

Self-Assembled Tetrahedral DNA Nanostructures Promote Neural Stem Cell Proliferation and Neuronal Differentiation.

Stem cell-based therapy is considered a promising approach for the repair of nervous tissues. Neural stem cells (NSCs) cannot proliferate or differentiate efficiently; hence, different biomaterials have been explored to improve NSC proliferation and differentiation. However, these agents either had low bioavailability or poor biocompatibility. In this work, our group investigated the effects of tetrahedral DNA nanostructures (TDNs), a novel DNA biological material, on the self-renew and differentiation of neuroectodermal (NE-4C) stem cells. We observed that TDN treatment promoted self-renew of the stem cells via activating the Wnt/β -catenin pathway. In addition, our findings suggested that NE-4C stem cells' neuronal differentiation could be promoted effectively by TDNs via inhibiting the notch signaling pathway. In summary, this is the first report about the effects of TDNs on the proliferation and differentiation of NE-4C stem cells and the results demonstrate that TDNs have a great potential in nerve tissue regeneration.

BFGF and Poly‐RGD Cooperatively Establish Biointerface for Stem Cell Adhesion, Proliferation, and Differentiation

AbstractBiointerface design is widely used to functionalize biomaterials with controllable physicochemical properties. Functionalized biointerface provides a versatile platform to connect biological entities and nonbiogenic materials. Existing nanofabrication approaches to create such a nanostructured biointerface involve in low stability of the functionalized nanolayer and simple functionalities that limit its applicability. Here, a stable nanolayered synthetic polypeptide (poly[LA‐co‐(Glc‐alt‐Lys)] and modified with arginine‐glycine‐aspartic acid, PRGD)/basic fibroblast growth factor (bFGF) biointerface is created via structural matching, charge interaction, and hydrogen bonding. The cooperative effect of the PRGD/bFGF biointerface shows multiple functionalities in promoting stem cell adhesion by 33% increase in cell adhesion to poly(d,l‐lactic acid) substrate as compared to experiments on bare substrate as a control. Moreover, the biointerface enhances proliferation by 40% in cell density, potential differentiation by 62%, and gene expression by 40 and 80% respectively as compared to the control samples. The fabricated biointerface may have applications in nerve regeneration, tissue repair, and stem cell‐based therapy.

Strategies on the treatment of nerve injuries accompanied by severe soft tissue damage - Consensus statement of the German-Speaking Society for Microsurgery of Peripheral Nerves and Vessels

Nerve injuries with severe soft tissue damage are rare and demand a complex and individualized treatment approach, in order to limit medical and socioeconomic consequences. Since uniform systematic evidence so far is lacking, inconsistent therapy standards are implemented depending on individual experiences and background of respective microsurgeons.In order to provide best conditions for further healing, basic expert consensus statements were developed in a workshop on the 38th Annual Meeting of the German-speaking Community for Microsurgery of the Peripheral Nerves and Vessels (DAM).Statements were consented in regard of the aspects: timing of nerve and soft tissue repair, techniques of nerve repair, as well as rehabilitation and healing process control.

Noncoding RNAs and Their Potential Therapeutic Applications in Tissue Engineering

Abstract Tissue engineering is a relatively new but rapidly developing field in the medical sciences. Noncoding RNAs (ncRNAs) are functional RNA molecules without a protein-coding function; they can regulate cellular behavior and change the biological milieu of the tissue. The application of ncRNAs in tissue engineering is starting to attract increasing attention as a means of resolving a large number of unmet healthcare needs, although ncRNA-based approaches have not yet entered clinical practice. In-depth research on the regulation and delivery of ncRNAs may improve their application in tissue engineering. The aim of this review is: to outline essential ncRNAs that are related to tissue engineering for the repair and regeneration of nerve, skin, liver, vascular system, and muscle tissue; to discuss their regulation and delivery; and to anticipate their potential therapeutic applications.

Fabrication and characterization of Antheraea pernyi silk fibroin-blended P(LLA-CL) nanofibrous scaffolds for peripheral nerve tissue engineering

Electrospun nanofibers have gained widespreading interest for tissue engineering application. In the present study, ApF/P(LLA-CL) nanofibrous scaffolds were fabricated via electrospinning. The feasibility of the material as tissue engineering nerve scaffold was investigated in vitro. The average diameter increased with decreasing the blend ratio of ApF to P(LLA-CL). Characterization of 13C NMR and FTIR clarified that there is no obvious chemical bond reaction between ApF and P(LLA-CL). The tensile strength and elongation at break increased with the content increase of P(LLA-CL). The surface hydrophilic property of nanofibrous scaffolds enhanced with the increased content of ApF. Cell viability studies with Schwann cells demonstrated that ApF/P(LLA-CL) blended nanofibrous scaffolds significantly promoted cell growth as compare to P(LLA-CL), especially when the weight ratio of ApF to P(LLA-CL) was 25:75. The present work provides a basis for further studies of this novel nanofibrous material (ApF/P(LLA-CL)) in peripheral nerve tissue repair or regeneration.

3D Printing of Aniline Tetramer-Grafted-Polyethylenimine and Pluronic F127 Composites for Electroactive Scaffolds.

Electroactive hydrogel scaffolds are fabricated by the 3D-printing technique using composites of 30% Pluronic F127 and aniline tetramer-grafted-polyethylenimine (AT-PEI) copolymers with various contents from 2.5% to 10%. The synthesized AT-PEI copolymers can self-assemble into nanoparticles with the diameter of ≈50 nm and display excellent electroactivity due to AT conjugation. The copolymers are then homogeneously distributed into 30% Pluronic F127 solution by virtue of the thermosensitivity of F127, denoted as F/AT-PEI composites. Macroscopic photographs of latticed scaffolds elucidate their excellent printability of F/AT-PEI hydrogels for the 3D-printing technique. The conductivities of the printed F/AT-PEI scaffolds are all higher than 2.0 × 10-3 S cm-1 , which are significantly improved compared with that of F127 scaffold with only 0.94 × 10-3 S cm-1 . Thus, the F/AT-PEI scaffolds can be considered as candidates for application in electrical stimulation of tissue regeneration such as repair of muscle and cardiac nerve tissue.

Pore structure and dielectric behaviour of the 3D collagen-DAC scaffolds designed for nerve tissue repair

The design and selection of a suitable scaffold with well-defined pores size distribution and dielectric properties are critical features for neural tissue engineering. In this study we use mercury porosimetry and the dielectric spectroscopy in the alpha-dispersion region of the electric field to determine the microarchitecture and activation energy of collagen (Col) modified by 2,3 dialdehyde cellulose (DAC). The scaffold was synthesized in three steps: (i) preparation of DAC by oxidation of cellulose, (ii) construction of a 3D Col sponge-shape or film, (iii) cross-linkage of the Col samples using DAC. The activation energy needed to break the bonds formed by water in the Col-DAC composite is approximately 2 times lower than that in the unmodified Col. In addition, the magnitude of conductivity for modified Col at 70°C is approximately 40% lower than that recorded for the unmodified Col. The largest fraction, of which at least 70% of the total pore volume comprises the sponge, is occupied by pores ranging from 20 to 100μm in size. The knowledge on the dielectric behaviour and microstructure of the Col-DAC scaffold may prove relevant to neural tissue engineering focused on the regeneration of the nervous system.