Nerve Regeneration In Animal Models Research Articles

Increased efficiency of peripheral nerve regeneration using supercritical carbon dioxide-based decellularization in acellular nerve graft

Acellular nerve grafts (ANGs) are a promising therapeutic for patients with nerve defects caused by injuries. Conventional decellularization methods utilize a variety of detergents and enzymes. However, these methods have disadvantages, such as long processing times and the presence of detergents that remain on the graft. In this study, we aimed to reduce process time and minimize the risks associated with residual detergents by replacing them with supercritical carbon dioxide (scCO2) and compared the effectiveness to Hudson’s decellularization method, which uses several detergents. The dsDNA and the expression of MHC1 and 2 were significantly reduced in both decellularized groups, which confirmed the effective removal of cellular debris. The extracellular matrix proteins and various factors were found to be better preserved in the scCO2 ANGs compared to the detergent-ANGs. We conducted behavioral tests and histological analyses to assess the impact of scCO2 ANGs on peripheral nerve regeneration in animal models. Compared with Hudson’s method, the scCO2 method effectively improved the efficacy of peripheral nerve regeneration. Therefore, the decellularization method using scCO2 is not only beneficial for ANG synthesis, but it may also be helpful for therapeutics by enhancing the efficacy of peripheral nerve regeneration.

Adipose Tissue Derivatives in Peripheral Nerve Regeneration after Transection: A Systematic Review.

Peripheral nerve injury (PNI) is increasingly prevalent and challenging to treat despite advances in microsurgical techniques. In this context, adipose tissue derivatives, such as adipose-derived stem cells, nanofat, and stromal vascular fraction have been gaining attention as potential allies in peripheral nerve regeneration. This study aims to explore the use of adipose tissue derivatives in nerve regeneration following peripheral nerve transection in murine models. Thus, we assess and synthesize the key techniques and methods used for evaluating the obtained nerve regeneration to guide future experimental research and clinical interventions. A systematic review was conducted in February 2024, adhering to the Cochrane and PRISMA 2020 guidelines, using the PubMed, SciELO, and LILACS databases. The focus was on experimental studies involving adipose tissue derivatives in nerve regeneration in animal models post-transection. Only experimental trials reporting nerve regeneration outcomes were included; studies lacking a comparator group or evaluation methods were excluded. Out of 273 studies initially identified from MEDLINE, 19 were selected for detailed analysis. The average study included 32.5 subjects, with about 10.2 subjects per intervention subgroup. The predominant model was the sciatic nerve injury with a 10 mm gap. The most common intervention involved unprocessed adipose-derived stem cells, utilized in 14 articles. This review underscores the significant potential of current methodologies in peripheral nerve regeneration, particularly highlighting the use of murine models and thorough evaluation techniques.

Therapeutic Effect of Schwann Cell-Like Cells Differentiated from Human Tonsil-Derived Mesenchymal Stem Cells on Diabetic Neuropathy in db/db Mice.

Diabetic neuropathy (DN) is the most common complication of diabetes, and approximately 50% of patients with this disease suffer from peripheral neuropathy. Nerve fiber loss in DN occurs due to myelin defects and is characterized by symptoms of impaired nerve function. Schwann cells (SCs) are the main support cells of the peripheral nervous system and play important roles in several pathways contributing to the pathogenesis and development of DN. We previously reported that human tonsil-derived mesenchymal stem cells differentiated into SCs (TMSC-SCs), named neuronal regeneration-promoting cells (NRPCs), which cells promoted nerve regeneration in animal models with peripheral nerve injury or hereditary peripheral neuropathy. In this study, NRPCs were injected into the thigh muscles of BKS-db/db mice, a commonly used type 2 diabetes model, and monitored for 26weeks. Von Frey test, sensory nerve conduction study, and staining of sural nerve, hind foot pad, dorsal root ganglia (DRG) were performed after NRPCs treatment. Von Frey test results showed that the NRPC treatment group (NRPC group) showed faster responses to less force than the vehicle group. Additionally, remyelination of sural nerve fibers also increased in the NRPC group. After NRPCs treatment, an improvement in response to external stimuli and pain sensation was expected through increased expression of PGP9.5 in the sole and TRPV1 in the DRG. The NRPCs treatment may alleviate DN through the remyelination and the recovery of sensory neurons, could provide a better life for patients suffering from complications of this disease.

The Effect of Acetyl-L-Carnitine (ALCAR) on Peripheral Nerve Regeneration in Animal Models: A Systematic Review.

Peripheral neuropathies caused by the peripheral nervous system (PNS) damage can occur due to trauma and other disorders. They present as altered sensation, weakness, autonomic symptoms, and debilitating pain syndrome with a wide range of clinical signs. Acetyl-L-Carnitine (ALCAR) is a biological compound with essential roles in mitochondrial oxidative metabolism and anti-oxidant effects that protects mitochondria from oxidative damage and inhibits apoptosis caused by mitochondrial damage. This study is a systematic review and meta-analysis of the effects of ALCAR on peripheral nerve injuries. This review examines studies on treating traumatic peripheral neuropathies in which ALCAR is administered to rats with sciatic nerve injury with an appropriate control group. The articles were divided based on the mode of ALCAR administration. If one method was used in more than one article, their results were entered in the "Revman5.4" software and were meta-analyzed. Studies were selected from 1994 to 2018 on rats with varying physical injuries to their sciatic nerves. In one study, ALCAR was provided to rats in their drinking water, while in other studies, ALCAR was injected intra-peritoneally. Different mechanisms of ALCAR actions have been suggested in this study, but the underpinnings of the neuroprotective effects of ALCAR are still unclear. Further studies are mandatory to clarify the actual mechanisms of the neuroprotective activity of ALCAR. Based on the results of existing studies, ALCAR effectively increases the tolerance threshold of thermal and mechanical stimuli, reduces latency, and reduces apoptosis; finally, adjusting the dose and duration of administration may increase the dose and duration axon diameter.

Pro-angiogenic scaffold-free Bio three-dimensional conduit developed from human induced pluripotent stem cell-derived mesenchymal stem cells promotes peripheral nerve regeneration

Although autologous nerve grafting is widely accepted as the gold standard treatment for segmental nerve defects, harvesting autologous nerves is highly invasive and leads to functional loss of the ablated part. In response, artificial nerve conduits made of artificial materials have been reported, but the efficacy of the nerve regeneration still needs improvement. The purpose of this study is to investigate the efficacy and mechanism of the Bio three-dimensional (3D) conduit composed of xeno-free human induced pluripotent stem cell–derived mesenchymal stem cells (iMSCs). The 5-mm nerve gap of the sciatic nerve in immunodeficient rats was bridged with the Bio 3D conduit or silicone tube. Functional and histological recovery were assessed at 8 weeks after surgery. The regenerated nerve in the Bio 3D group was significantly superior to that in the silicone group based on morphology, kinematics, electrophysiology, and wet muscle weight. Gene expression analyses demonstrated neurotrophic and angiogenic factors. Macroscopic observation revealed neovascularization both inside and on the surface of the Bio 3D conduit. Upon their subcutaneous implantation, iMSCs could induce angiogenesis. The Bio 3D conduit fabricated from iMSCs are an effective strategy for nerve regeneration in animal model. This technology will be useful in future clinical situations.

Successful and Complete Recovery of the Ulnar Nerve After Eight Years of Chronic Injury Through Local Steroid Injections: A Case Report.

Peripheral neuropathy is a common neurodegenerative disease, with vastness of inducers and causalities. The acquired form peripheral neuropathy can be caused by traumatic injuries caused by nerve lacerations or compressions. Such injuries are usually followed by Wallerian degeneration, and inflammatory reaction. We present a case of a 33-year-old female with a chronic loss of the ulnar nerve function for 8 years after traumatic laceration. After that, she regained the functions of ulnar nerve after nerve stimulation by peri-ulnar nerve injection of methylprednisolone and lidocaine. The theory behind using steroids is related to the fact that the immune system could induce a secondary injury that interferes with the recovery. Many studies have shown effectiveness in using steroids alone or when combined with other substances on nerve regeneration in animal models. We believe that this is the first report of nerve recovery using local steroidal injections after a traumatic injury.

Neurotrophic support by traumatized muscle-derived multipotent progenitor cells: Role of endothelial cells and Vascular Endothelial Growth Factor-A

BackgroundAdult mesenchymal stem cells (MSCs) have been shown to increase nerve regeneration in animal models of nerve injury. Traumatized muscle-derived multipotent progenitor cells (MPCs) share important characteristics with MSCs and are isolated from severely damaged muscle tissue following surgical debridement. Previous investigations have shown that MPCs may be induced to increase production of several neurotrophic factors, suggesting the possible utility of autologous MPCs in peripheral nerve regeneration following injury. Recent findings have also shown that components of the vascular niche, including endothelial cells (ECs) and vascular endothelial growth factor (VEGF)-A, regulate neural progenitor cells and sensory neurons.MethodsIn this study, we have investigated the neuroinductive activities of MPCs, particularly MPC-produced VEGF-A, in the context of an aligned, neuroconductive nerve guide conduit and the endothelial component of the vascular system. Embryonic dorsal root ganglia (DRG) seeded on poly-ϵ-caprolactone aligned nanofibrous scaffold (NF) constructs and on tissue culture plastic, were cocultured with induced MPCs or treated with their conditioned medium (MPC-CM).ResultsIncreased neurite extension was observed on both NF and tissue culture plastic in the presence of MPC-CM versus cell-free control CM. The addition of CM from ECs significantly increased the neurotrophic activity of induced MPC-CM, suggesting that MPC and EC neurotrophic activity may be synergistic. Distinctly higher VEGF-A production was seen in MPCs following neurotrophic induction versus culture under normal growth conditions. Selective removal of VEGF-A from MPC-CM reduced the observed DRG neurite extension length, indicating VEGF-A involvement in neurotrophic activity of the CM.ConclusionsTaken together, these findings suggest the potential of MPCs to encourage nerve growth via a VEGF-A-dependent action, and the use of MPC-CM or a combination of MPC and CM from ECs for peripheral nerve repair in conjunction with NFs in a nerve guide conduit. Due to the ease of use, application of bioactive agents derived from cultured cells to enhance neurotrophic support presents a promising line of research into peripheral nerve repair.

The Comparison of Schwann Cells Transplantation Effect with Autograft Model in Peripheral Nerve Regeneration in Animal Model

The Comparison of Schwann Cells Transplantation Effect with Autograft Model in Peripheral Nerve Regeneration in Animal Model

Electrical stimulation enhances sensory recovery: a randomized controlled trial.

Brief postsurgical electrical stimulation (ES) has been shown to enhance peripheral nerve regeneration in animal models following axotomy and crush injury. However, whether this treatment is beneficial in humans with sensory nerve injury has not been tested. The goal of this study was to test the hypothesis that ES would enhance sensory nerve regeneration following digital nerve transection compared to surgery alone. Patients with complete digital nerve transection underwent epineurial nerve repair. After coaptation of the severed nerve ends, fine wire electrodes were implanted before skin closure. Postoperatively, patients were randomized to receiving either 1 hour of 20Hz continuous ES or sham stimulation in a double-blinded manner. Patients were followed monthly for 6 months by a blinded evaluator to monitor physiological recovery of spatial discrimination, pressure threshold, and quantitative small fiber sensory testing. Functional disability was measured using the Disability of Arm, Shoulder, and Hand questionnaire. A total of 36 patients were recruited, with 18 in each group. Those in the ES group showed consistently greater improvements in all sensory modalities by 5 to 6 months postoperatively compared to the controls. Although there was a trend of greater functional improvements in the ES group, it was not statistically significant (p > 0.01). Postsurgical ES enhanced sensory reinnervation in patients who sustained complete digital nerve transection. The conferred benefits apply to a wide range of sensory functions.

Electrical regulation of Schwann cells using conductive polypyrrole/chitosan polymers

Electrical stimulation (ES) can dramatically enhance neurite outgrowth through conductive polymers and accelerate peripheral nerve regeneration in animal models of nerve injury. Therefore, conductive tissue engineering graft in combination with ES is a potential treatment for neural injuries. Conductive tissue engineering graft can be obtained by seeding Schwann cells on conductive scaffold. However, when ES is applied through the conductive scaffold, the impact of ES on Schwann cells has never been investigated. In this study, a biodegradable conductive composite made of conductive polypyrrole (PPy, 2.5%) and biodegradable chitosan (97.5%) was prepared in order to electrically stimulate Schwann cells. The tolerance of Schwann cells to ES was examined by a cell apoptosis assay. The growth of the cells was characterized using DAPI staining and a MTT assay. mRNA and protein levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in Schwann cells were assayed by RT-PCR and Western blotting, and the amount of NGF and BDNF secreted was determined by an ELISA assay. The results showed that the PPy/chitosan membranes supported cell adhesion, spreading, and proliferation with or without ES. Interestingly, ES applied through the PPy/chitosan composite dramatically enhanced the expression and secretion of NGF and BDNF when compared with control cells without ES. These findings highlight for the first time the possibility of enhancing nerve regeneration in conductive scaffolds through ES-increased neurotrophin secretion.

The application of viral vectors to enhance regeneration after peripheral nerve repair

Objective: Despite great advancements in surgical repair techniques, a considerable degree of functional impairment remains in the majority of patients after peripheral nerve reconstruction. New concepts to promote regeneration of the peripheral nerve are needed since it is generally held that surgery has reached an optimal technical refinement. Several neurotrophic factors stimulate regeneration of the peripheral nerve, but the effects of the exogenous application of these factors have so far been limited, possibly as the result of their fast degradation and unwanted side effects after systemic application. These problems can be resolved with the recent development of non-toxic, non-immunogenic viral vectors that drive local, long-term transgene expression.Methods: The literature was searched for papers describing the application of gene therapy, specifically viral vectors, in peripheral nerve lesion models.Results: Retroviral vectors have been used successfully for the ex vivo transduction of Schwann cells, before seeding in artificial nerve guides. Lentiviral (LV) vectors direct long-term transgene expression in Schwann cells in rat peripheral nerves. LV vectors are also capable of transducing cultured segments of human sural nerve, thereby providing 'proof of concept' for the feasibility of genetic modification of sural nerve transplants in a clinical setting.Discussion: In the near future, viral vectors will increasingly be used to study a wide range of neurotrophic factors and other potentially therapeutic proteins for their effect on peripheral nerve regeneration in animal models. If this approach leads to beneficial effects on regeneration and functional recovery, the safety and clinical applicability of these viral vectors will allow the rapid translation of basic research to clinical trials. This makes the use of viral vectors a highly attractive concept that holds great promise as a novel adjuvant therapy to peripheral nerve reconstruction.

Fetal Ultrasound

In this discussion, any biological effect of ultrasound that is accompanied by temperature increments less than 1 degrees C above normal physiologic levels is called a mechanical effect. However, one should keep in mind that the term mechanical effect also includes processes that are not of a mechanical nature but arise secondary to mechanical interaction between ultrasound and tissues, such as chemical reactions initiated by free oxygen species generated during cavitation and sonoluminescence. Investigations with laboratory animals have documented that pulsed ultrasound can produce damage to biological tissues in vivo through nonthermal mechanisms. The acoustic output used to induce these adverse bio-effects is considerably greater than the output of diagnostic devices when gas bodies are not present. However, low-intensity pulsed ultrasound is used clinically to accelerate the bone fracture repair process and induce healing of nonunions in humans. Low-intensity pulsed ultrasound also has been shown to enhance repair of soft tissue damage and accelerate nerve regeneration in animal models. Although such exposures to low intensity do not appear to cause damage to exposed tissues, they do raise questions about the acoustic threshold that might induce potentially adverse developmental effects in the fetus. To date, bioeffects studies in humans do not substantiate a causal relationship between diagnostic ultrasound exposure during pregnancy and adverse biological effects to the fetus. However, the epidemiologic studies were conducted with commercially available devices predating 1992, having outputs not exceeding a derated spatial-peak temporal-average intensity (ISPTA.3) of 94 mW/cm2. Current limits in the United States allow an ISPTA.3 of 720 mW/cm2 for obstetric modes. At the time of this report, available evidence, experimental or epidemiologic, is insufficient to conclude that there is a causal relationship between obstetric diagnostic ultrasound exposure and adverse nonthermal effects to the fetus. However, low-intensity pulsed ultrasound effects reported in humans and animal models indicate a need for further investigation of potentially adverse developmental effects.

NT-3 promotes nerve regeneration and sensory improvement in CMT1A mouse models and in patients

Xenografts from patients with Charcot-Marie-Tooth type 1A (CMT1A) have shown delayed myelination and impaired regeneration of nude mice axons passing through the grafted segments. Neurotrophin-3 (NT-3), an important component of the Schwann cell (SC) autocrine survival loop, could correct these deficiencies. To assess the efficacy of NT-3 treatment in preclinical studies using animal models of CMT1A and to conduct a double-blind, placebo-controlled, randomized, pilot clinical study to assess the efficacy of subcutaneously administered NT-3 in patients with CMT1A. Nude mice harboring CMT1A xenografts and Trembler(J) mice with a peripheral myelin protein 22-point mutation were treated with NT-3, and the myelinated fiber (MF) and SC numbers were quantitated. Eight patients received either placebo (n = 4) or 150 microg/kg NT-3 (n = 4) three times a week for 6 months. MF regeneration in sural nerve biopsies before and after treatment served as the primary outcome measure. Additional endpoint measures included the Mayo Clinic Neuropathy Impairment Score (NIS), electrophysiologic measurements, quantitative muscle testing, and pegboard performance. The NT-3 treatment augmented axonal regeneration in both animal models. For CMT1A patients, changes in the NT-3 group were different from those observed in the placebo group for the mean number of small MFs within regeneration units (p = 0.0001), solitary MFs, (p = 0.0002), and NIS (p = 0.0041). Significant improvements in these variables were detected in the NT-3 group but not in the placebo group. Pegboard performance was significantly worsened in the placebo group. NT-3 was well tolerated. Neurotrophin-3 augments nerve regeneration in animal models for CMT1A and may benefit patients clinically, but these results need further confirmation.