Chitosan conduits combined with nerve growth factor microspheres repair facial nerve defects

Enhancing the Effect of Placental Extract on the Regeneration of Crush Injured Facial Nerve

There is a scarcity of experimental studies on peripheral nerve regeneration using placental extract (PE). This study aimed to investigate the effects of topical PE application on recovery after crush injury to the rat facial nerve using functional, electrophysiological, and morphological evaluations. The viability of the RSC96 Schwann cells treated with PE (0.5~4 mg/ml) increased significantly. Immunoblot test revealed that PE application enhanced the migration of RSC96 cells. Quantitative polymerase chain reaction demonstrated that PE increased the expression of neurotropic genes. The recovery from vibrissa fibrillation in the PE-treated group was superior to that in the control group. The threshold of action potential was also significantly lower in the PE group. Histopathological examination showed that crushed facial nerves treated with PE exhibited larger axons. The surrounding myelin sheaths were more distinct and thicker in the PE-treated group. Hence, PE may be considered a topical therapeutic agent for treating traumatic facial nerve paralysis.

Analysis of Related Factors Affecting Facial Nerve Function after Acoustic Neuroma Surgery

Objective

To investigate the factors affecting facial nerve function after acoustic neuroma surgery and to provide theoretical reference for clinicians to preserve facial nerve function better after surgery.

Methods

A retrospective cohort study was conducted to analyze the correlation between postoperative facial nerve function and surgical approach, age, sex, tumor size and adhesion degree of facial nerve in 152 patients with acoustic neuroma.

Results

In the choice of surgical approach, there was no significant difference in the anatomy of the complete facial nerve in labyrinth path, retrosigmoid sinus path, and middle cranial fossa path. There was no statistically significant difference between the middle cranial fossa path and the retrosigmoid sinus path in facial nerve function preservation 7 days after surgery. The difference between middle cranial fossa path and labyrinthine path was statistically significant (P < 0.01). There were statistically significant differences between labyrinth path and retrosigmoid sinus path (P < 0.05). Logistic multivariate regression analysis showed that the operative approach and the degree of adhesion between tumor and facial nerve were the risk factors affecting functional preservation of facial nerve 7 days after surgery. Age and the degree of adhesion between tumor and facial nerve were the risk factors for functional preservation of facial nerve 1 year after operation.

Conclusion

The facial nerve function injury in patients with acoustic neuroma may be related to the choice of surgical approach, the adhesion degree of tumor and facial nerve, and their age. Clinicians need to comprehensively evaluate the risk factors before surgery, so as to achieve individualized treatment to protect the integrity of postoperative facial nerve function of patients.

Applications of Chitosan in Surgical and Post-Surgical Materials

The continuous advances in surgical procedures require continuous research regarding materials with surgical applications. Biopolymers are widely studied since they usually provide a biocompatible, biodegradable, and non-toxic material. Among them, chitosan is a promising material for the development of formulations and devices with surgical applications due to its intrinsic bacteriostatic, fungistatic, hemostatic, and analgesic properties. A wide range of products has been manufactured with this polymer, including scaffolds, sponges, hydrogels, meshes, membranes, sutures, fibers, and nanoparticles. The growing interest of researchers in the use of chitosan-based materials for tissue regeneration is obvious due to extensive research in the application of chitosan for the regeneration of bone, nervous tissue, cartilage, and soft tissues. Chitosan can serve as a substance for the administration of cell-growth promoters, as well as a support for cellular growth. Another interesting application of chitosan is hemostasis control, with remarkable results in studies comparing the use of chitosan-based dressings with traditional cotton gauzes. In addition, chitosan-based or chitosan-coated surgical materials provide the formulation with antimicrobial activity that has been highly appreciated not only in dressings but also for surgical sutures or meshes.

Chitosan Tubes Inoculated with Dental Pulp Stem Cells and Stem Cell Factor Enhance Facial Nerve-Vascularized Regeneration in Rabbits

Facial nerve injury is a common clinical condition that leads to disfigurement and emotional distress in the affected individuals, and the recovery presents clinical challenges. Tissue engineering is the standard method to repair nerve defects. However, nerve regeneration is still not satisfactory because of poor neovascularization after implantation, especially for the long-segment nerve defects. In the current study, we aimed to investigate the potential of chitosan tubes inoculated with stem cell factor (SCF) and dental pulp stem cells (DPSCs) in facial nerve-vascularized regeneration. In the in vitro experiment, DPSCs were isolated, cultured, and then identified. The optimal concentration of SCF was screened by CCK8. Cytoskeleton and living-cell staining, migration, CCK8 test, and neural differentiation assays were performed, revealing that SCF promoted the biological activity of DPSCs. Surprisingly, SCF increased the neural differentiation of DPSCs. The migration and angiogenesis experiments were carried out to show that SCF promoted the angiogenesis and migration of human umbilical vein endothelial cells (HUVECs). In the facial nerve, 7 mm defects of New Zealand white rabbits, hematoxylin-eosin (HE), immunohistochemistry, toluidine blue staining, and transmission electron microscopy observation were performed at 12 weeks postsurgery to show more nerve fibers and better myelin sheath in the SCF + DPSC group. In addition, the whisker movements, Masson's staining, and western blot assays were performed, demonstrating functional repair and that the expression level of CD31 protein in the group SCF + DPSCs was relatively close to that in the group Autograft. In summary, chitosan tubes inoculated with SCF and DPSCs increased neurovascularization and provided an effective method for repairing facial nerve defects, indicating great promise for clinical application.

A Review of Techniques for Biodelivery of Nerve Growth Factor (NGF) to the Brain in Relation to Alzheimer's Disease

Age-dependent progressive neurodegeneration and associated cognitive dysfunction represent a serious concern worldwide. Currently, dementia accounts for the fifth highest cause of death, among which Alzheimer's disease (AD) represents more than 60% of the cases. AD is associated with progressive cognitive dysfunction which affects daily life of the affected individual and associated family. The cognitive dysfunctions are at least partially due to the degeneration of a specific set of neurons (cholinergic neurons) whose cell bodies are situated in the basal forebrain region (basal forebrain cholinergic neurons, BFCNs) but innervate wide areas of the brain. It has been explicitly shown that the delivery of the neurotrophic protein nerve growth factor (NGF) can rescue BFCNs and restore cognitive dysfunction, making NGF interesting as a potential therapeutic substance for AD. Unfortunately, NGF cannot pass through the blood-brain barrier (BBB) and thus peripheral administration of NGF protein is not viable therapeutically. NGF must be delivered in a way which will allow its brain penetration and availability to the BFCNs to modulate BFCN activity and viability. Over the past few decades, various methodologies have been developed to deliver NGF to the brain tissue. In this chapter, NGF delivery methods are discussed in the context of AD.

Ten-eleven translocation methylcytosine dioxygenase 3-loaded microspheres penetrate neurons in vitro causing active demethylation and neurite outgrowth

Epigenetic processes, such as DNA methylation and other chromatin modifications, are believed to be largely responsible for establishing a reduced capacity for growth in the mature nervous system. Ten-eleven translocation methylcytosine dioxygenase 3 (Tet3)-, a member of the Tet gene family, plays a crucial role in promoting injury-induced DNA demethylation and expression of regeneration-associated genes in the peripheral nervous system. Here, we encapsulate Tet3 protein within a clinically tolerated poly(lactide-co-glycolide) microsphere system. Next, we show that Tet3-loaded microspheres are internalized into mHippoE-18 embryonic hippocampal cells. We compare the outgrowth potential of Tet3 microspheres with that of commonly used nerve growth factor (NGF)-loaded microspheres in an in vitro injury model. Tet3-containing microspheres increased levels of nuclear 5-hydroxymethylcytosine indicating active demethylation and outperformed NGF-containing microspheres in measures of neurite outgrowth. Our results suggest that encapsulated demethylases may represent a novel avenue to treat nerve injuries.

Repair of temporal branch of the facial nerve with novel polyglycolic acid-collagen tube: a case report of two cases

Autologous nerve transplantation has been the gold standard in the treatment of facial nerve injury, however it has not been achieved satisfactory result and needs donor sacrifice. A polyglycolic acid collagen conduit (Nerbridge, Toyobo Co., Japan) has the potential to compare to or exceed autologous nerve grafts in promoting nerve regeneration. Here we report two cases of traumatic temporal facial nerve injury repairs with Nerbridge. The severed temporal branch of the facial nerve was repaired with Nerbridge conduits in two patients. Recovery of movement was assessed by clinical photography and needle electromyography. The frontal muscle started moving five months postoperatively in both cases. Electromyography at twelve months showed polymorphic electric discharge, suggesting connection of the injured nerve to the frontal muscle. In the final results, each patient had good eyebrow elevation distance and moderate forward gaze recovery in comparison to their healthy sides. Considering that facial nerves are reported to recover incompletely even in autologous nerve graft repair cases, our two cases showed reasonable recovery comparable to nerve autografting. The Nerbridge conduit is a promising alternative to standard treatments for facial nerve recovery.

[The fabrication and related properties study of chitosan-poly (lactide-co-glycolide) double-walled microspheres loaded with nerve growth factor]

Objective

To evaluate the feasibility of the chitosan-poly (lactide-co-glycolide) (PLGA) double-walled microspheres for sustained release of bioactive nerve growth factor (NGF) in vitro.

Methods

NGF loaded chitosan-PLGA double-walled microspheres were prepared by emulsion-ionic method with sodium tripolyphosphate (TPP) as an ionic cross-linker. The double-walled microspheres were cross-linked by different concentrations of TPP [1%, 3%, 10% ( W/ V)]. NGF loaded PLGA microspheres were also prepared. The outer and inner structures of double-walled microspheres were observed by light microscopy, scanning electron microscopy, confocal laser scanning microscopy, respectively. The size and distribution of microspheres and fourier transform infra red spectroscopy (FT-IR) were analyzed. PLGA microspheres with NGF or chitosan-PLGA double-walled microspheres cross-linked by 1%, 3%, and 10%TPP concentration (set as groups A, B, C, and D respectively) were used to determine the degradation ratio of microspheres in vitro and the sustained release ratio of NGF in microspheres at different time points. The bioactivity of NGF (expressed as the percentage of PC12 cells with positive axonal elongation reaction) in the sustained release solution of chitosan-PLGA double-walled microspheres without NGF (set as group A1) was compared in groups B, C, and D.

Results

The chitosan-PLGA double-walled microspheres showed relative rough and spherical surfaces without aggregation. Confocal laser scanning microscopy showed PLGA microspheres were evenly uniformly distributed in the chitosan-PLGA double-walled microspheres. The particle size of microspheres ranged from 18.5 to 42.7 μm. The results of FT-IR analysis showed ionic interaction between amino groups and phosphoric groups of chitosan in double-walled microspheres and TPP. In vitro degradation ratio analysis showed that the degradation ratio of double-walled microspheres in groups B, C, and D appeared faster in contrast to that in group A. In addition, the degradation ratio of double-walled microsphere in groups B, C, and D decreased when the TPP concentration increased. There were significant differences in the degradation ratio of each group ( P<0.05). In vitro sustained release ratio of NGF showed that when compared with PLGA microspheres in group A, double-walled microspheres in groups B, C, and D released NGF at a relatively slow rate, and the sustained release ratio decreased with the increase of TPP concentration. Except for 84 days, there was significant difference in the sustained release ratio of NGF between groups B, C, and D ( P<0.05). The bioactivity of NGF results showed that the percentage of PC12 cells with positive axonal elongation reaction in groups B, C, and D was significantly higher than that in group A1 ( P<0.05). At 7 and 28 days of culture, there was no significant difference between groups B, C, and D ( P>0.05); at 56 and 84 days of culture, the percentage of PC12 cells with positive axonal elongation reaction in groups C and D was significantly higher than that in group B ( P<0.05), and there was no significant difference between groups C and D ( P>0.05).

Conclusion

NGF loaded chitosan-PLGA double-walled microspheres have a potential clinical application in peripheral nerve regeneration after injury.

Relevance and Recent Developments of Chitosan in Peripheral Nerve Surgery

Developments in tissue engineering yield biomaterials with different supporting strategies to promote nerve regeneration. One promising material is the naturally occurring chitin derivate chitosan. Chitosan has become increasingly important in various tissue engineering approaches for peripheral nerve reconstruction, as it has demonstrated its potential to interact with regeneration associated cells and the neural microenvironment, leading to improved axonal regeneration and less neuroma formation. Moreover, the physiological properties of its polysaccharide structure provide safe biodegradation behavior in the absence of negative side effects or toxic metabolites. Beneficial interactions with Schwann cells (SC), inducing differentiation of mesenchymal stromal cells to SC-like cells or creating supportive conditions during axonal recovery are only a small part of the effects of chitosan. As a result, an extensive body of literature addresses a variety of experimental strategies for the different types of nerve lesions. The different concepts include chitosan nanofibers, hydrogels, hollow nerve tubes, nerve conduits with an inner chitosan layer as well as hybrid architectures containing collagen or polyglycolic acid nerve conduits. Furthermore, various cell seeding concepts have been introduced in the preclinical setting. First translational concepts with hollow tubes following nerve surgery already transferred the promising experimental approach into clinical practice. However, conclusive analyses of the available data and the proposed impact on the recovery process following nerve surgery are currently lacking. This review aims to give an overview on the physiologic properties of chitosan, to evaluate its effect on peripheral nerve regeneration and discuss the future translation into clinical practice.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Approaches to Peripheral Nerve Repair: Generations of Biomaterial Conduits Yielding to Replacing Autologous Nerve Grafts in Craniomaxillofacial Surgery

Peripheral nerve injury is a common clinical entity, which may arise due to traumatic, tumorous, or even iatrogenic injury in craniomaxillofacial surgery. Despite advances in biomaterials and techniques over the past several decades, reconstruction of nerve gaps remains a challenge. Autografts are the gold standard for nerve reconstruction. Using autografts, there is donor site morbidity, subsequent sensory deficit, and potential for neuroma development and infection. Moreover, the need for a second surgical site and limited availability of donor nerves remain a challenge. Thus, increasing efforts have been directed to develop artificial nerve guidance conduits (ANCs) as new methods to replace autografts in the future. Various synthetic conduit materials have been tested in vitro and in vivo, and several first- and second-generation conduits are FDA approved and available for purchase, while third-generation conduits still remain in experimental stages. This paper reviews the current treatment options, summarizes the published literature, and assesses future prospects for the repair of peripheral nerve injury in craniomaxillofacial surgery with a particular focus on facial nerve regeneration.

Morphological study of dynamic culture of thermosensitive collagen hydrogel in constructing tissue engineering complex

ABSTACT The purpose of this study is to research the morphologies and functional characteristics of the cell-scaffold complex in vitro constructed under dynamic culture conditions. BMSCs were isolated from the long bones of Fischer344 rats, and performed in vitro amplification to the third generation as seed cells, together with thermosensitive collagen hydrogel (TCH) as cell adhesion matrix, and poly-L-lactic acid (PLLA) as scaffold, to construct cell-scaffold complex. The cell-scaffold complexes in the experiment group and the control group were then performed dynamic culture and static culture. After 7 d of in vitro culture, the complexes in the 2 groups were performed gross observation and SEM; meanwhile, the total DNA content in the complex was detected on D0,1,3, and 7 of culture. After cultured using these 2 ways, collagen could both wrap the PLLA scaffold, forming dense film-like structures on the PLLA surface. The total DNA contents in the cell-scaffold complex of the experiment group on D1,3, and 7 were significantly higher than the control group (P < 0.05). Compared with D0, the total DNA contents on D1,3, and 7 in both groups were gradually increased, but only the total DNA contents on D7 showed statistically significant difference than D0 (P < 0.05). TCH -PLLA fiber joint-constructed complex extracellular matrix had good biocompatibility, and dynamic culture could promote the distribution of BMSCs on the surface and inside the structure, thus promoting cell proliferation, so it could be used for the in vitro construction of tissue engineering complex.

Exogenous nerve growth factor protects the hypoglossal nerve against crush injury

Studies have shown that sensory nerve damage can activate the p38 mitogen-activated protein kinase (MAPK) pathway, but whether the same type of nerve injury after exercise activates the p38MAPK pathway remains unclear. Several studies have demonstrated that nerve growth factor may play a role in the repair process after peripheral nerve injury, but there has been little research focusing on the hypoglossal nerve injury and repair. In this study, we designed and established rat models of hypoglossal nerve crush injury and gave intraperitoneal injections of exogenous nerve growth factor to rats for 14 days. p38MAPK activity in the damaged neurons was increased following hypoglossal nerve crush injury; exogenous nerve growth factor inhibited this increase in acitivity and increased the survival rate of motor neurons within the hypoglossal nucleus. Under transmission electron microscopy, we found that the injection of nerve growth factor contributed to the restoration of the morphology of hypoglossal nerve after crush injury. Our experimental findings indicate that exogenous nerve growth factor can protect damaged neurons and promote hypoglossal nerve regeneration following hypoglossal nerve crush injury.

Past, Present, and Future of Nerve Conduits in the Treatment of Peripheral Nerve Injury

With significant advances in the research and application of nerve conduits, they have been used to repair peripheral nerve injury for several decades. Nerve conduits range from biological tubes to synthetic tubes, and from nondegradable tubes to biodegradable tubes. Researchers have explored hollow tubes, tubes filled with scaffolds containing neurotrophic factors, and those seeded with Schwann cells or stem cells. The therapeutic effect of nerve conduits is improving with increasing choice of conduit material, new construction of conduits, and the inclusion of neurotrophic factors and support cells in the conduits. Improvements in functional outcomes are expected when these are optimized for use in clinical practice.

Dorsal root ganglion-derived Schwann cells combined with poly(lactic-co-glycolic acid)/chitosan conduits for the repair of sciatic nerve defects in rats

Schwann cells, nerve regeneration promoters in peripheral nerve tissue engineering, can be used to repair both the peripheral and central nervous systems. However, isolation and purification of Schwann cells are complicated by contamination with fibroblasts. Current reported measures are mainly limited by either high cost or complicated procedures with low cell yields or purity. In this study, we collected dorsal root ganglia from neonatal rats from which we obtained highly purified Schwann cells using serum-free melanocyte culture medium. The purity of Schwann cells (> 95%) using our method was higher than that using standard medium containing fetal bovine serum. The obtained Schwann cells were implanted into poly(lactic-co-glycolic acid)/chitosan conduits to repair 10-mm sciatic nerve defects in rats. Results showed that axonal diameter and area were significantly increased and motor functions were obviously improved in the rat sciatic nerve tissue. Experimental findings suggest that serum-free melanocyte culture medium is conducive to purify Schwann cells and poly(lactic-co-glycolic acid)/chitosan nerve conduits combined with Schwann cells contribute to restore sciatic nerve defects.

Craniocerebral injury promotes the repair of peripheral nerve injury

The increase in neurotrophic factors after craniocerebral injury has been shown to promote fracture healing. Moreover, neurotrophic factors play a key role in the regeneration and repair of peripheral nerve. However, whether craniocerebral injury alters the repair of peripheral nerve injuries remains poorly understood. Rat injury models were established by transecting the left sciatic nerve and using a free-fall device to induce craniocerebral injury. Compared with sciatic nerve injury alone after 6–12 weeks, rats with combined sciatic and craniocerebral injuries showed decreased sciatic functional index, increased recovery of gastrocnemius muscle wet weight, recovery of sciatic nerve ganglia and corresponding spinal cord segment neuron morphologies, and increased numbers of horseradish peroxidase-labeled cells. These results indicate that craniocerebral injury promotes the repair of peripheral nerve injury.

Dynamic culture of a thermosensitive collagen hydrogel as an extracellular matrix improves the construction of tissue-engineered peripheral nerve

Tissue engineering technologies offer new treatment strategies for the repair of peripheral nerve injury, but cell loss between seeding and adhesion to the scaffold remains inevitable. A thermosensitive collagen hydrogel was used as an extracellular matrix in this study and combined with bone marrow mesenchymal stem cells to construct tissue-engineered peripheral nerve composites in vitro. Dynamic culture was performed at an oscillating frequency of 0.5 Hz and 35° swing angle above and below the horizontal plane. The results demonstrated that bone marrow mesenchymal stem cells formed membrane-like structures around the poly-L-lactic acid scaffolds and exhibited regular alignment on the composite surface. Collagen was used to fill in the pores, and seeded cells adhered onto the poly-L-lactic acid fibers. The DNA content of the bone marrow mesenchymal stem cells was higher in the composites constructed with a thermosensitive collagen hydrogel compared with that in collagen I scaffold controls. The cellular DNA content was also higher in the thermosensitive collagen hydrogel composites constructed with the thermosensitive collagen hydrogel in dynamic culture than that in static culture. These results indicate that tissue-engineered composites formed with thermosensitive collagen hydrogel in dynamic culture can maintain larger numbers of seeded cells by avoiding cell loss during the initial adhesion stage. Moreover, seeded cells were distributed throughout the material.