Human umbilical cord blood stem cells and brain-derived neurotrophic factor for optic nerve injury:a biomechanical evaluation

Treatment for optic nerve injury by brain-derived neurotrophic factor or the transplantation of human umbilical cord blood stem cells has gained progress, but analysis by biomechanical indicators is rare. Rabbit models of optic nerve injury were established by a clamp. At 7 days after injury, the vitreous body received a one-time injection of 50 μg brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood stem cells. After 30 days, the maximum load, maximum stress, maximum strain, elastic limit load, elastic limit stress, and elastic limit strain had clearly improved in rabbit models of optical nerve injury after treatment with brain-derived neurotrophic factor or human umbilical cord blood stem cells. The damage to the ultrastructure of the optic nerve had also been reduced. These findings suggest that human umbilical cord blood stem cells and brain-derived neurotrophic factor effectively repair the injured optical nerve, improve biomechanical properties, and contribute to the recovery after injury.     

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.     

Polylactic-co-glycolic acid microspheres containing three neurotrophic factors promote sciatic nerve repair after injury

A variety of neurotrophic factors have been shown to repair the damaged peripheral nerve. However, in clinical practice, nerve growth factor, neurotrophin-3 and brain-derived neurotrophic factor are all peptides or proteins that may be rapidly deactivated at the focal injury site; their local effective concentration time following a single medication cannot meet the required time for spinal axons to regenerate and cross the glial scar. In this study, we produced polymer sustained-release microspheres based on the polylactic-co-glycolic acid copolymer; the microspheres at 300-μm diameter contained nerve growth factor, neurotrophin-3 and brain-derived neurotrophic factor. Six microspheres were longitudinally implanted into the sciatic nerve at the anastomosis site, serving as the experimental group; while the sciatic nerve in the control group was subjected to the end-to-end anastomosis using 10/0 suture thread. At 6 weeks after implantation, the lower limb activity, weight of triceps surae muscle, sciatic nerve conduction velocity and the maximum amplitude were obviously better in the experimental group than in the control group. Compared with the control group, more regenerating nerve fibers were observed and distributed in a dense and ordered manner with thicker myelin sheaths in the experimental group. More angiogenesis was also visible. Experimental findings indicate that polylactic-co-glycolic acid composite microspheres containing nerve growth factor, neurotrophin-3 and brain-derived neurotrophic factor can promote the restoration of sciatic nerve in rats after injury.     

Puerarin accelerates neural regeneration after sciatic nerve injury

Puerarin is a natural isoflavone isolated from plants of the genus Pueraria and functions as a protector against cerebral ischemia. We hypothesized that puerarin can be involved in the repair of peripheral nerve injuries. To test this hypothesis, doses of 10, 5, or 2.5 mg/kg per day puerarin(8-(β-D-Glucopyranosyl-7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) were injected intraperitoneally into mouse models of sciatic nerve injury. Puerarin at the middle and high doses significantly up-regulated the expression of growth-associated protein 43 in the L4–6 segments of the spinal cord from mice at 1, 2, and 4 weeks after modeling, and reduced the atrophy of the triceps surae on the affected side and promoted the regeneration of nerve fibers of the damaged spinal cord at 8 weeks after injury. We conclude that puerarin exerts an ongoing role to activate growth-associated protein 43 in the corresponding segment of the spinal cord after sciatic nerve injury, thus contributing to neural regeneration after sciatic nerve injuries.     

Chemically extracted aceUular allogeneic nerve graft combined with ciliary neurotrophic factor promotes sciatic nerve repair

A chemically extracted acellular allogeneic nerve graft can reduce postoperative immune rejection, similar to an autologous nerve graft, and can guide neural regeneration. However, it remains poorly understood whether a chemically extracted acellular allogeneic nerve graft combined with neurotrophic factors provides a good local environment for neural regeneration. This study investigated the repair of injured rat sciatic nerve using a chemically extracted acellular allogeneic nerve graft combined with ciliary neurotrophic factor. An autologous nerve anastomosis group and a chemical acellular allogeneic nerve bridging group were prepared as controls. At 8 weeks after repair, sciatic functional index, evoked potential amplitude of the soleus muscle, triceps wet weight recovery rate, total number of myelinated nerve fibers and myelin sheath thickness were measured. For these indices, values in the three groups showed the autologous nerve anastomosis group 〉 chemically extracted acellular nerve graft ＋ ciliary neurotrophic factor group 〉 chemical acellular allogeneic nerve bridging group. These results suggest that chemically extracted acellular nerve grafts combined with ciliary neurotrophic factor can repair sciatic nerve defects, and that this repair is inferior to autologous nerve anastomosis, but superior to chemically extracted acellular allogeneic nerve bridging alone.     

Acetyl-11-keto-beta-boswellic acid promotes sciatic nerve repair after injury: molecular mechanism

Previous studies showed that acetyl-11-keto-beta-boswellic acid (AKBA), the active ingredient in the natural Chinese medicine Boswellia, can stimulate sciatic nerve injury repair via promoting Schwann cell proliferation. However, the underlying molecular mechanism remains poorly understood. In this study, we performed genomic sequencing in a rat model of sciatic nerve crush injury after gastric AKBA administration for 30 days. We found that the phagosome pathway was related to AKBA treatment, and brain-derived neurotrophic factor expression in the neurotrophic factor signaling pathway was also highly up-regulated. We further investigated gene and protein expression changes in the phagosome pathway and neurotrophic factor signaling pathway. Myeloperoxidase expression in the phagosome pathway was markedly decreased, and brain-derived neurotrophic factor, nerve growth factor, and nerve growth factor receptor expression levels in the neurotrophic factor signaling pathway were greatly increased. Additionally, expression levels of the inflammatory factors CD68, interleukin-1β, pro-interleukin-1β, and tumor necrosis factor-α were also decreased. Myelin basic protein- and β3-tubulin-positive expression as well as the axon diameter-to-total nerve diameter ratio in the injured sciatic nerve were also increased. These findings suggest that, at the molecular level, AKBA can increase neurotrophic factor expression through inhibiting myeloperoxidase expression and reducing inflammatory reactions, which could promote myelin sheath and axon regeneration in the injured sciatic nerve.     

Changes in proteins related to early nerve repair in a rat model of sciatic nerve injury

Peripheral nerves have a limited capacity for self-repair and those that are severely damaged or have significant defects are challenging to repair. Investigating the pathophysiology of peripheral nerve repair is important for the clinical treatment of peripheral nerve repair and regeneration. In this study, rat models of right sciatic nerve injury were established by a clamping method. Protein chip assay was performed to quantify the levels of neurotrophic, inflammation-related, chemotaxis-related and cell generation-related factors in the sciatic nerve within 7 days after injury. The results revealed that the expression levels of neurotrophic factors (ciliary neurotrophic factor) and inflammation-related factors (intercellular cell adhesion molecule-1, interferon γ, interleukin-1α, interleukin-2, interleukin-4, interleukin-6, monocyte chemoattractant protein-1, prolactin R, receptor of advanced glycation end products and tumor necrosis factor-α), chemotaxis-related factors (cytokine-induced neutrophil chemoattractant-1, L-selectin and platelet-derived growth factor-AA) and cell generation-related factors (granulocyte-macrophage colony-stimulating factor) followed different trajectories. These findings will help clarify the pathophysiology of sciatic nerve injury repair and develop clinical treatments of peripheral nerve injury. This study was approved by the Ethics Committee of Peking University People’s Hospital of China (approval No. 2015-50) on December 9, 2015.

Chinese Library Classification No. R446; R745; R363     

Combining acellular nerve allografis with brain- derived neurotrophic factor transfected bone marrow mesenchymal stem cells restores sciatic nerve injury better than either intervention alone

In this study, we chemically extracted acellular nerve allografts from bilateral sciatic nerves, and repaired 10-mm sciatic nerve defects in rats using these grafts and brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells. Experiments were performed in three groups： the acellular nerve allograft bridging group, acellular nerve allograft ＋ bone marrow mesenchymal stem cells group, and the acellular nerve allograft ＋ brain-derived neurotrophic factor transfected bone marrow mesenchyrnal stem cells group. Results showed that at 8 weeks after bridging, sciatic functional index, triceps wet weight recovery rate, myelin thickness, and number of myelinated nerve fibers were significantly changed in the three groups. Variations were the largest in the acellular nerve allograft ＋ brain-derived neurotrophic factor transfected bone marrow mesenchymal stem cells group compared with the other two groups. Experimental findings suggest that chemically extracted acellular nerve allograft combined nerve factor and mesenchymal stem cells can promote the restoration of sciatic nerve defects. The repair effect seen is better than the single application of acellular nerve allograft or acellular nerve allograft combined mesenchymal stem cell transplantation.     

Intraoperative single administration of neutrophil peptide 1 accelerates the early functional recovery of peripheral nerves after crush injury

Neutrophil peptide 1 belongs to a family of peptides involved in innate immunity. Continuous intramuscular injection of neutrophil peptide 1 can promote the regeneration of peripheral nerves, but clinical application in this manner is not convenient. To this end, the effects of a single intraoperative administration of neutrophil peptide 1 on peripheral nerve regeneration were experimentally observed. A rat model of sciatic nerve crush injury was established using the clamp method. After model establishment, a normal saline group and a neutrophil peptide 1 group were injected with a single dose of normal saline or 10 μg/mL neutrophil peptide 1, respectively. A sham group, without sciatic nerve crush was also prepared as a control. Sciatic nerve function tests, neuroelectrophysiological tests, and hematoxylin-eosin staining showed that the nerve conduction velocity, sciatic functional index, and tibialis anterior muscle fiber cross-sectional area were better in the neutrophil peptide 1 group than in the normal saline group at 4 weeks after surgery. At 4 and 8 weeks after surgery, there were no differences in the wet weight of the tibialis anterior muscle between the neutrophil peptide 1 and saline groups. Histological staining of the sciatic nerve showed no significant differences in the number of myelinated nerve fibers or the axon cross-sectional area between the neutrophil peptide 1 and normal saline groups. The above data confirmed that a single dose of neutrophil peptide 1 during surgery can promote the recovery of neurological function 4 weeks after sciatic nerve injury. All the experiments were approved by the Medical Ethics Committee of Peking University People's Hospital, China(approval No. 2015-50) on December 9, 2015.     

Sericin protects against diabetes-induced injuries in sciatic nerve and related nerve cells

Sericin from discarded silkworm cocoons of silk reeling has been used in different fields, such as cosmetology, skin care, nutrition, and oncology. The present study established a rat model of type 2 diabetes by consecutive intraperitoneal injections of low-dose (25 mg/kg) streptozotocin. After intragastrical perfusion of sericin for 35 days, blood glucose levels significantly declined, and the expression of neurofilament protein in the sciatic nerve and nerve growth factor in L_4–6 spinal ganglion and anterior horn cells significantly increased. However, the expression of neuropeptide Y in spinal ganglion and anterior horn cells significantly decreased in model rats. These findings indicate that sericin protected the sciatic nerve and related nerve cells against injury in a rat type 2 diabetic model by upregulating the expression of neurofilament protein in the sciatic nerve and nerve growth factor in spinal ganglion and anterior horn cells, and downregulating the expression of neuropeptide Y in spinal ganglion and anterior horn cells.     

Miconazole enhances nerve regeneration and functional recovery after sciatic nerve crush injury

Introduction: Improving axonal outgrowth and remyelination is crucial for peripheral nerve regeneration. Miconazole appears to enhance remyelination in the central nervous system. In this study we assess the effect of miconazole on axonal regeneration using a sciatic nerve crush injury model in rats. Methods: Fifty Sprague‐Dawley rats were divided into control and miconazole groups. Nerve regeneration and myelination were determined using histological and electrophysiological assessment. Evaluation of sensory and motor recovery was performed using the pinprick assay and sciatic functional index. The Cell Counting Kit‐8 assay and Western blotting were used to assess the proliferation and neurotrophic expression of RSC 96 Schwann cells. Results: Miconazole promoted axonal regrowth, increased myelinated nerve fibers, improved sensory recovery and walking behavior, enhanced stimulated amplitude and nerve conduction velocity, and elevated proliferation and neurotrophic expression of RSC 96 Schwann cells. Discussion: Miconazole was beneficial for nerve regeneration and functional recovery after peripheral nerve injury. Muscle Nerve 57 : 821–828, 2018     

Ursolic acid induces neural regeneration after sciatic nerve injury

In this study,we aimed to explore the role of ursolic acid in the neural regeneration of the injured sciatic nerve.BALB/c mice were used to establish models of sciatic nerve injury through unilateral sciatic nerve complete transection and microscopic anastomosis at 0.5 cm below the ischial tuberosity.The successfully generated model mice were treated with 10,5,or 2.5 mg/kg ursolic acid via intraperitoneal injection.Enzyme-linked immunosorbent assay results showed that serum S100 protein expression level gradually increased at 1-4 weeks after sciatic nerve injury,and significantly decreased at 8 weeks.As such,ursolic acid has the capacity to significantly increase S100 protein expression levels.Real-time quantitative PCR showed that S100 mRNA expression in the L4-6 segments on the injury side was increased after ursolic acid treatment.In addition,the muscular mass index in the soleus muscle was also increased in mice treated with ursolic acid.Toluidine blue staining revealed that the quantity and average diameter of myelinated nerve fibers in the injured sciatic nerve were significantly increased after treatment with ursolic acid.10 and 5 mg/kg of ursolic acid produced stronger effects than 2.5 mg/kg of ursolic acid.Our findings indicate that ursolic acid can dose-dependently increase S100 expression and promote neural regeneration in BALB/c mice following sciatic nerve injury.     

Glial cell line-derived neurotrophic factor enhances axonal regeneration following sciatic nerve transection in adult rats

Adult rat sciatic nerve was transected and sutured with an entubulation technique. The nerve interstump gap was filled with either collagen gel (COL) or collagen gel mixed with glial cell line-derived neurotrophic factor (COL/GDNF). Four weeks after nerve transection, horseradish peroxidase (HRP)-labelled spinal cord motoneurons and the myelinated distal stump axons were quantified. Compared with the COL group, the percentages of labeled spinal somas and axon number were significantly increased after topically applied glial cell line-derived neurotrophic factor (GDNF). The functional recovery of the transected nerve was improved in COL/GDNF group. GAP-43 expression was also significantly higher in COL/GDNF group 1 and 2 weeks after sciatic nerve axotomy vs. COL group. These data provide strong evidence that GDNF could promote axonal regeneration in adult rats, suggesting the potential use of GDNF in therapeutic approaches to peripheral nerve injury and neuropathies.     

Disruption of the midkine gene (Mdk) delays degeneration and regeneration in injured peripheral nerve

Midkine (MK) is a growth factor implicated in the development and repair of various tissues, especially neural tissues. MK acts as a reparative neurotrophic factor in damaged peripheral nerves. A postulated role of MK in the degeneration and regeneration of sciatic nerves was explored by comparing wild‐type (Mdk^+/+) mice with MK‐deficient (Mdk^?/?) mice after freezing injury. In the Mdk^?/? mice, a regenerative delay was observed, preceded by a decelerated Wallerian degeneration (WD). The relative wet weight of the soleus muscle slowly declined, and recovery was delayed compared with that in the Mdk^+/+ mice. In the regenerating nerve, unmyelinated axons were unevenly distributed, and some axons contained myelin‐like, concentrically lamellated bodies. In the endplates of soleus muscles, nerve terminals containing synaptic vesicles disappeared in both mice. In Mdk^?/? mice, the appearance of nerve terminals was delayed in synaptic vesicles of terminal buttons after injury. The recovery of evoked electromyogram was delayed in Mdk^?/? mice compared with Mdk^+/+ mice. Our results suggested a delay in axonal degeneration and regeneration in Mdk^?/? mice compared with Mdk^+/+ mice, and the delayed regeneration was associated with a delayed recovery of motor function. These findings show that a lack of MK following peripheral nerve injury is a critical factor in degeneration and regeneration, and manipulation of the supply of MK may offer interesting therapeutic options for the treatment of peripheral nerve damage. © 2009 Wiley‐Liss, Inc.     

Exogenous platelet-derived growth factor improves neurovascular unit recovery after spinal cord injury

The blood-spinal cord barrier plays a vital role in recovery after spinal cord injury. The neurovascular unit concept emphasizes the relationship between nerves and vessels in the brain, while the effect of the blood-spinal cord barrier on the neurovascular unit is rarely reported in spinal cord injury studies. Mouse models of spinal cord injury were established by heavy object impact and then immediately injected with plateletderived growth factor(80 μg/kg) at the injury site. Our results showed that after platelet-derived growth factor administration, spinal cord injury, neuronal apoptosis, and blood-spinal cord barrier permeability were reduced, excessive astrocyte proliferation and the autophagyrelated apoptosis signaling pathway were inhibited, collagen synthesis was increased, and mouse locomotor function was improved. In vitro, human umbilical vein endothelial cells were established by exposure to 200 μM H_2O_2. At 2 hours prior to injury, in vitro cell models were treated with 5 ng/mL platelet-derived growth factor. Our results showed that expression of blood-spinal cord barrier-related proteins, including Occludin, Claudin 5, and β-catenin, was significantly decreased and autophagy was significantly reduced. Additionally, the protective effects of platelet-derived growth factor could be reversed by intraperitoneal injection of 80 mg/kg chloroquine, an autophagy inhibitor, for 3 successive days prior to spinal cord injury. Our findings suggest that platelet-derived growth factor can promote endothelial cell repair by regulating autophagy, improve the function of the blood-spinal cord barrier, and promote the recovery of locomotor function post-spinal cord injury. Approval for animal experiments was obtained from the Animal Ethics Committee, Wenzhou Medical University, China(approval No. wydw2018-0043) in July 2018.     

Study on molecular mechanism for improving neural regeneration after repair of sciatic nerve defect in rat by acellular nerve allograft

Objective: Discuss the molecular mechanism for improving neural regeneration after repair of sciatic nerve defect in rat by acellular nerve allograft (ANA). Methods: Randomly divide 36 Wistar rats into six groups as normal control group, autografting group, and bridging groups of 2, 4, 8, 12 weeks, six rats for each group. Observe the expression of brain‐derived neurotrophic factor (BDNF) in L₄ spinal cord and anterior tibial muscle at the injury site, calcitonin gene‐related peptide (CGRP) protein as well as mRNA, respectively. 12w after operation, histopathological observation was performed. Results: 2w after ANA bridging the sciatic nerve defect in rats, it was observed that the expression level of BDNF in spinal cord at the injury site and CGRP protein increased, reaching the peak level at 4w, lasting till 8w, then decreased but still significantly higher than that in normal control group at 12w, and was not significantly different compared with that in autografting group. However, the expression level of BDNF in anterior tibial muscle decreased gradually within the initial 4w, then increased progressively, reaching normal level at 12w, and was not significantly different compared with that in autografting group. The expression of BDNF mRNA and CGRPmRNA was essentially the same. 12w after operation, there was nerve regeneration in bridging group of 12w and autografting group. Conclusions: ANA possessed fine histocompatibility, and might substitute autograft to repair long‐segment defect of sciatic nerve in rats. This action might be related to upregulation of protein and mRNA expression for BDNF and CGRP in spinal cord. Synapse, 2012. © 2011 Wiley Periodicals, Inc.     

Human umbilical cord blood-derived mesenchymal stem cells promote regeneration of crush-injured rat sciatic nerves

Several studies have demonstrated that human umbilical cord blood-derived mesenchymal stem cells can promote neural regeneration following brain injury. However, the therapeutic effects of human umbilical cord blood-derived mesenchymal stem cells in guiding peripheral nerve regeneration remain poorly understood. This study was designed to investigate the effects of human umbilical cord blood-derived mesenchymal stem cells on neural regeneration using a rat sciatic nerve crush injury model. Human umbilical cord blood-derived mesenchymal stem cells (1 × 10 6 ) or a PBS control were injected into the crush-injured segment of the sciatic nerve. Four weeks after cell injection, brain-derived neurotrophic factor and tyrosine kinase receptor B mRNA expression at the lesion site was increased in comparison to control. Furthermore, sciatic function index, Fluoro Gold-labeled neuron counts and axon density were also significantly increased when compared with control. Our results indicate that human umbilical cord blood-derived mesenchymal stem cells promote the functional recovery of crush-injured sciatic nerves.     

Repair of peripheral nerve defects with chemically extracted acellular nerve allografts loaded with neurotrophic factors-transfected bone marrow mesenchymal stem cells

Chemically extracted acellular nerve allografts loaded with brain-derived neurotrophic factor-transfected or ciliary neurotrophic factor-transfected bone marrow mesenchymal stem cells have been shown to repair sciatic nerve injury better than chemically extracted acellular nerve allografts alone, or chemically extracted acellular nerve allografts loaded with bone marrow mesenchymal stem cells. We hypothesized that these allografts compounded with both brain-derived neurotrophic factor- and ciliary neurotrophic factor-transfected bone marrow mesenchymal stem cells may demonstrate even better effects in the repair of peripheral nerve injury. We cultured bone marrow mesenchymal stem cells expressing brain-derived neurotrophic factor and/or ciliary neurotrophic factor and used them to treat sciatic nerve injury in rats. We observed an increase in sciatic functional index, triceps wet weight recovery rate, myelin thickness, number of myelinated nerve fibers, amplitude of motor-evoked potentials and nerve conduction velocity, and a shortened latency of motor-evoked potentials when allografts loaded with both neurotrophic factors were used, compared with allografts loaded with just one factor. Thus, the combination of both brain-derived neurotrophic factor and ciliary neurotrophic factor-transfected bone marrow mesenchymal stem cells can greatly improve nerve injury.     

Brain-derived neurotrophic factor expression in dorsal root ganglion neurons in response to reanastomosis of the distal stoma after nerve grafting

Studies have shown that retreatment of the distal stoma after nerve grafting can stimulate nerve regeneration. The present study attempted to verify the effects of reanastomosis of the distal stoma, after nerve grafting, on nerve regeneration by assessing brain-derived neurotrophic factor expression in 2-month-old rats. Results showed that brain-derived neurotrophic factor expression in L 2-4 dorsal root ganglia began to increase 3 days after autologous nerve grafting post sciatic nerve injury, peaked at 14 days, decreased at 28 days, and reached similar levels to the sham-surgery group at 56 days. Brain-derived neurotrophic factor expression in L 2-4 dorsal root ganglia began to increase 3 days after reanastomosis of the distal stoma, 59 days after autologous nerve grafting post sciatic nerve injury, significantly increased at 63 days, peaked at 70 days, and gradually decreased thereafter, but remained higher compared with the sham-surgery group up to 112 days. The results of this study indicate that reanastomosis of the distal stoma after orthotopic nerve grafting stimulated brain-derived neurotrophic factor expression in L 2-4 dorsal root ganglia.