Peripheral Nerve Injury-Induced Astrocyte Activation in Spinal Ventral Horn Contributes to Nerve Regeneration.

Accumulating evidences suggest that peripheral nerve injury (PNI) may initiate astrocytic responses in the central nervous system (CNS). However, the response of astrocytes in the spinal ventral horn and its potential role in nerve regeneration after PNI remain unclear. Herein, we firstly illustrated that astrocytes in the spinal ventral horn were dramatically activated in the early stage following sciatic nerve injury, and these profiles were eliminated in the chronic stage. Additionally, we found that the expression of neurotrophins, including brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3), also accompanied with astrocyte activation. In comparison with the irreversible transected subjects, astrocyte activation and the neurotrophic upregulation in the early stage were more drastic in case the transected nerve was rebridged immediately after injury. Furthermore, administering fluorocitrate to inhibit astrocyte activation resulted in decreased neurotrophin expression in the spinal ventral horn and delayed axonal regeneration in the nerve as well as motor function recovery. Overall, the present study indicates that peripheral nerve injury can initiate astrocyte activation accompanied with neurotrophin upregulation in the spinal ventral horn. The above responses mainly occur in the early stage of PNI and may contribute to nerve regeneration and motor function recovery.

Corydalis decumbens Alleviates the Migration, Phagocytosis, and Inflammatory Response of Macrophages.

Background: The role of Corydalis decumbens (CD) in macrophage activation remains unclear, particularly in the Ras homolog family member A (RhoA) signaling pathway. Therefore, the present study aimed to investigate the effect of CD on the viability, proliferation, morphological changes, migration, phagocytosis, differentiation, and release of inflammatory factors and signaling pathways in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Methods: Cell counting kit-8 and water-soluble tetrazolium salt assays were used to evaluate the viability and proliferation of RAW264.7 macrophages. A transwell assay was examined to assess cell migration. The ingestion of lumisphere assay was employed to detect the phagocytic capacity of macrophages. Phalloidin staining was performed to observe morphological changes in the macrophages. An enzyme-linked immunosorbent assay was performed to quantify inflammation-related cytokines in cell culture supernatants. Cellular immunofluorescence and western blotting were adopted to show the expression of inflammation-related factors, biomarkers of M1/M2 subset macrophages, and factors of the RhoA signaling pathway. Results: We found that CD increased the viability and proliferation of RAW264.7 macrophages. CD also impaired the migration and phagocytic capacity of macrophages, induced anti-inflammatory M2 macrophage polarization, such as M2-like morphological changes, and upregulated M2 macrophage biomarkers and anti-inflammatory factors. We also observed that CD inactivated the RhoA signaling pathway. Conclusions: CD mediates the activation of LPS-stimulated macrophages, alleviates the inflammatory responses of macrophages, and activates related signaling pathways induced by LPS.

[Effect of early intervention of electroacupuncture on learning-memory ability and level of hippocampal phosphorylated Tau protein in SAMP8 mice].

OBJECTIVE: To explore the effect of early intervention electroacupuncture (EA) at "Baihui" (GV 20), "Dazhui" (GV 14) and "Shenshu" (BL 23) on the learning-memory ability and the expression of phosphorylated Tau protein in the hippocampus of SAMP8 mice, so as to provide reference for the intervening period of EA for Alzheimer's disease (AD). METHODS: A total of 36 3-month old SAMP8 mice were randomly divided into a model group, a 3-month-old EA group and a 9-month-old EA group, 12 mice in each group. Twelve normal SAMR1 mice with the same age were taken as the control group. The mice in the 3-month-old EA group and 9-month-old EA group were treated with EA at "Baihui" (GV 20), "Dazhui" (GV 14) and "Shenshu" (BL 23) separately 3 months old and 9 months old (continuous wave, 2 Hz, 1.5-2 mA), 20 min each time, once a day, 8 days as a course of treatment, with an interval of 2 days between courses, totally 3 courses of treatment were given. The mice sample in each group was collected at the age of 10 months after the learning-memory ability tested by Morris water maze. The expression of phosphorylated Tau protein in the hippocampus was detected by immunohistochemistry and Western blot, and the expression of Tau mRNA was detected by real-time PCR. RESULTS: Compared with the control group, in the model group, the escape latency was significantly increased (P<0.01), the time of stay in the original platform quadrant and the number of crossing the platform quadrant were reduced (P<0.01), and the expressions of phosphorylated Tau protein and Tau mRNA in hippocampus were increased (P<0.01). Compared with the model group, in the 3-month-old EA group and 9-month-old EA group, the escape latency was significantly reduced (P<0.05), the time of stay in the original platform quadrant and the number of crossing the platform quadrant were increased (P<0.05), and the expressions of phosphorylated Tau protein and Tau mRNA in hippocampus were reduced (P<0.05). Compared with the 9-month-old EA group, in the 3-month-old EA group, the escape latency was significantly reduced (P<0.05), the time of stay in the original platform quadrant and the number of crossing the platform quadrant were increased (P<0.05), and the expressions of phosphorylated Tau protein and Tau mRNA were reduced (P<0.01). CONCLUSION: The early EA intervention could more effectively improve the learning-memory ability and inhibit phosphorylation of Tau protein in the hippocampus of SAMP8 mice.

Electroacupuncture Improves Synaptic Function in SAMP8 Mice Probably via Inhibition of the AMPK/eEF2K/eEF2 Signaling Pathway.

Synaptic loss and dysfunction is associated with cognitive impairment in Alzheimer's disease (AD). Recent evidence indicates that the AMP-activated protein kinase (AMPK)/eukaryotic elongation factor-2 kinase (eEF2K)/eukaryotic elongation factor-2 (eEF2) pathway was implicated in synaptic plasticity in AD. Therapeutic strategies for AD treatment are currently limited. Here, we investigate the effects of electroacupuncture (EA) on synaptic function and the AMPK/eEF2K/eEF2 signaling pathway in male senescence-accelerated mouse-prone 8 (SAMP8) mice. Male 7-month-old SAMP8 and SAMR1 mice (senescence-accelerated mouse resistant 1) were randomly divided into 3 groups: SAMR1 control group (Rc), SAMP8 control group (Pc), and SAMP8 electroacupuncture group (Pe). The Pe group was treated with EA for 30 days. Transmission electron microscopy (TEM) was used to observe the structure of synapse. The protein and mRNA expression of synaptophysin (SYN) and postsynaptic density 95 (PSD95) was examined by immunohistochemistry, western blot, and real-time RT-PCR. The activity of AMPK and eEF2K was studied by western blot. Our results showed that EA ameliorated synaptic loss, increased the expression of SYN and PSD95, and inhibited AMPK activation and eEF2K activity. Collectively, these findings suggested that the mechanisms of EA improving synaptic function in AD may be associated with the inhibition of the AMPK/eEF2K/eEF2 signaling pathway.

Inhibition of RhoA-Subfamily GTPases Suppresses Schwann Cell Proliferation Through Regulating AKT Pathway Rather Than ROCK Pathway.

Inhibiting RhoA-subfamily GTPases by C3 transferase is widely recognized as a prospective strategy to enhance axonal regeneration. When C3 transferase is administered for treating the injured peripheral nerves, Schwann cells (SCs, important glial cells in peripheral nerve) are inevitably impacted and therefore SC bioeffects on nerve regeneration might be influenced. However, the potential role of C3 transferase on SCs remains elusive. Assessed by cell counting, EdU and water-soluble tetrazolium salt-1 (WST-1) assays as well as western blotting with PCNA antibody, herein we first found that CT04 (a cell permeable C3 transferase) treatment could significantly suppress SC proliferation. Unexpectedly, using Y27632 to inhibit ROCK (the well-accepted downstream signal molecule of RhoA subfamily) did not impact SC proliferation. Further studies indicated that CT04 could inactivate AKT pathway by altering the expression levels of phosphorylated AKT (p-AKT), PI3K and PTEN, while activating AKT pathway by IGF-1 or SC79 could reverse the inhibitory effect of CT04 on SC proliferation. Based on present data, we concluded that inhibition of RhoA-subfamily GTPases could suppress SC proliferation, and this effect is independent of conventional ROCK pathway but involves inactivation of AKT pathway.

Lentivirus-Mediated RNA Interference Targeting RhoA Slacks the Migration, Proliferation, and Myelin Formation of Schwann Cells.

RhoA, a member of Rho GTPases family, is known to play an important role in remodeling actin cytoskeleton. During the development of the peripheral nervous system (PNS), Schwann cells undergo proliferation, migration, and radial sorting and finally wrap the related axons compactly to form myelin sheath. All these processes involve actin cytoskeletal remodeling. However, the role of RhoA on Schwann cell during development is still unclear. To address this question, we first used a lentiviral vector-mediated short hairpin (sh) RNA targeting RhoA to knock down the expression of RhoA in the cultured Schwann cells in vitro. Effects of RhoA on Schwann cell proliferation and migration were examined by BrdU assay and transwell assay, respectively. Results of the present study indicated that downregulated RhoA expression in cultured Schwann cells significantly slacked the cells' capabilities of migration and proliferation. Then, we investigated the role of RhoA in the developing rat sciatic nerves. Immunohistology and Western blotting showed that RhoA was mainly expressed in Schwann cells in the sciatic nerves and was peaked at 2 weeks postnatal then kept in low level up to 8 weeks. In the subjected rats whose sciatic nerves were microinjected with lentiviral vectors at postnatal 3 days, we found that the lentiviruses mainly transfected Schwann cells, and the RhoA expression in the transfected Schwann cells was significantly knocked down. Four weeks after lentivirus microinjection, immunohistology and transmission electron microscopy illustrated that RhoA knockdown resulted in hypomyelination and significant decrease of the thickness of myelin in the transfected area. Overall data of current study suggested that RhoA plays a critical role in Schwann cell biology and is essential for myelination in developing peripheral nerve.

Tissue engineering with peripheral blood-derived mesenchymal stem cells promotes the regeneration of injured peripheral nerves.

Peripheral nerve injury repair can be enhanced by Schwann cell (SC) transplantation, but clinical applications are limited by the lack of a cell source. Thus, alternative systems for generating SCs are desired. Herein, we found the peripheral blood-derived mesenchymal stem cells (PBMSCs) could be induced into SC like cells with expressing SC-specific markers (S100, P75NTR and CNPase) and functional factors (NGF, NT-3, c-Fos, and Krox20). When the induced PBMSCs (iPBMSCs) were transplanted into crushed rat sciatic nerves, they functioned as SCs by wrapping the injured axons and expressing myelin specific marker of MBP. Furthermore, iPBMSCs seeded in an artificial nerve conduit to bridge a 10-mm defect in a sciatic nerve achieved significant nerve regeneration outcomes, including axonal regeneration and remyelination, nerve conduction recovery, and restoration of motor function, and attenuated myoatrophy and neuromuscular junction degeneration in the target muscle. Overall, the data from this study indicated that PBMSCs can transdifferentiate towards SC-like cells and have potential as grafting cells for nerve tissue engineering.

Osteogenesis of peripheral blood mesenchymal stem cells in self assembling peptide nanofiber for healing critical size calvarial bony defect.

Peripheral blood mesenchymal stem cells (PBMSCs) may be easily harvested from patients, permitting autologous grafts for bone tissue engineering in the future. However, the PBMSC's capabilities of survival, osteogenesis and production of new bone matrix in the defect area are still unclear. Herein, PBMSCs were seeded into a nanofiber scaffold of self-assembling peptide (SAP) and cultured in osteogenic medium. The results indicated SAP can serve as a promising scaffold for PBMSCs survival and osteogenic differentiation in 3D conditions. Furthermore, the SAP seeded with the induced PBMSCs was splinted by two membranes of poly(lactic)-glycolic acid (PLGA) to fabricate a composited scaffold which was then used to repair a critical-size calvarial bone defect model in rat. Twelve weeks later the defect healing and mineralization were assessed by H&E staining and microcomputerized tomography (micro-CT). The osteogenesis and new bone formation of grafted cells in the scaffold were evaluated by immunohistochemistry. To our knowledge this is the first report with solid evidence demonstrating PBMSCs can survive in the bone defect area and directly contribute to new bone formation. Moreover, the present data also indicated the tissue engineering with PBMSCs/SAP/PLGA scaffold can serve as a novel prospective strategy for healing large size cranial defects.

Nanofiber scaffolds for treatment of spinal cord injury.

Spinal cord injury (SCI) is a common neurologic disorder that results in loss of sensory function and mobility. It is well documented that tissue engineering is a potential therapeutic strategy for treatment of SCI. In this connection, various biomaterials have been explored to meet the needs of SCI tissue engineering and these include natural materials, synthetic biodegradable polymers and synthetic non- degradable polymers. Nanofiber scaffolds are newly emerging biomaterials that have been widely utilized in tissue engineering recently. In comparison to the traditional biomaterials, nanofibers have advantages in topography and porosity, thus mimicking the naturally occurring extracellular matrix. Besides, they exhibit excellent biocompatibility with low immunogenicity, and furthermore they are endowed with properties that help to bridge the lesion cavity or gap, and serve as an effective delivery system for graft cells or therapeutic drugs. This review summarizes some of the unique properties of nanofiber scaffolds which are critical to their potential application in treatment of injured spinal cord.

A novel artificial nerve graft for repairing long-distance sciatic nerve defects: a self-assembling peptide nanofiber scaffold-containing poly(lactic-co-glycolic acid) conduit.

In this study, we developed a novel artificial nerve graft termed self-assembling peptide nanofiber scaffold (SAPNS)-containing poly(lactic-co-glycolic acid) (PLGA) conduit (SPC) and used it to bridge a 10-mm-long sciatic nerve defect in the rat. Retrograde tracing, behavioral testing and histomorphometric analyses showed that compared with the empty PLGA conduit implantation group, the SPC implantation group had a larger number of growing and extending axons, a markedly increased diameter of regenerated axons and a greater thickness of the myelin sheath in the conduit. Furthermore, there was an increase in the size of the neuromuscular junction and myofiber diameter in the target muscle. These findings suggest that the novel artificial SPC nerve graft can promote axonal regeneration and remyelination in the transected peripheral nerve and can be used for repairing peripheral nerve injury.