Effect of Astragalus membranaceus in rats on peripheral nerve regeneration: in vitro and in vivo studies.

BACKGROUND: This study provides in vitro and in vivo evaluation of Astragalus membranaceus (AM) on peripheral nerve regeneration. METHODS: In the in vitro study, we analyzed the effects of AM on cell differentiation and neurite outgrowth by using a PC12 cell model. In the in vivo study, silicone rubber chambers filled with the AM water extract were used to bridge a 10-mm sciatic nerve defect in rats. RESULTS: We found that the AM water extract caused a marked enhancement of the nerve growth factor-mediated neurite outgrowth and the expression of growth-associated protein 43 from PC12 cells. Animals from the groups treated with the AM for 8 weeks had a relatively more mature structure with larger mean values of myelinated axon number, endoneurial area, and total nerve area when compared with those in the controls receiving the saline only. CONCLUSION: These results suggest that the silicone rubber tubes present a good framework for the nerve fibers to regenerate across the gap, and the AM extract can be a potential nerve growth-promoting factor, being salutary in aiding the growth of axons in the peripheral nerve.

Use of electrical stimulation at different current levels to promote recovery after peripheral nerve injury in rats.

BACKGROUND: Electrical stimulation of damaged peripheral nerve may aid regeneration. METHODS: A 10-mm gap was made in rat sciatic nerve by suturing the stumps into silicone rubber tubes. A control group received no stimulation. To determine whether 2 Hz of percutaneous electrical stimulation at 1 mA, 2 mA, or 4 mA augments regeneration between the proximal and distal nerve stumps. RESULTS: The groups receiving electrical treatment had larger mean values of axon number, endoneurial area, total nerve area, blood vessel number, and blood vessel area compared with the controls. In addition, the group receiving electrical stimulation, especially at 1 mA had significantly shorter latency, larger amplitude, larger area of the evoked muscle action potentials and faster conduction velocity compared with the controls. However, electrical stimulation at 4 mA provoked adverse responses to the function recovery of regenerated nerves in the kinematic gait analysis. CONCLUSION: Indeed, the electrical stimulation appears to have a detrimental effect on the regeneration process. It could promote the growth of regenerating nerves; however, excessive direct current could be repulsive to regrowing fibers. This reveals the importance for physical therapists using safe stimulus protocols for rehabilitation purposes.

Enhancement of AG1024-induced H9c2 cardiomyoblast cell apoptosis via the interaction of IGF2R with Galpha proteins and its downstream PKA and PLC-beta modulators by IGF-II.

Our previous studies found that insulin-like growth factor-I receptor (IGF1R) signaling blockade caused cardiac hypertrophy, and that apoptosis is required for upregulating the IGF-II and the IGF-II/ mannose 6-phosphate receptor (IGF2R) gene. However, the role of IGF-II in the regulation of cell apoptosis through IGF2R is little known. In this study, we hypothesized that IGF-II may induce cell apoptosis through IGF2R but is dependent on IGF1R activity. Western blots and TUNEL assay revealed that in the presence of IGF1R, exogenous IGF-II acts, like IGF-I, would increase phospho-Akt through IGF1R, but does not affect the caspase 3 activation and apoptotic induction in H9c2 cardiomyoblast cells. Conversely, AG1024, an inhibitor of IGF1R activity, causes cell apoptosis, and the treatment with IGF-II further enhances this process, implying that it occurs through IGF2R. Moreover, immunoprecipitation assay revealed that treatment with IGF-II could enhance the interaction of IGF2R with Galphai and Galphaq but reduce its binding with Galphas, resulting in the reduction of phospho-PKA and the activation of PLC-beta. Taken together, these data provide new insight into the dual role of IGF-II in the control of IGF1R dependent cell apoptosis and involved activation of IGF2R signaling. Improving IGF1R activity and suppressing IGF2R may be a good strategy to prevent the progression of heart disease with cardiomyocyte apoptosis.

Highly permeable genipin-cross-linked gelatin conduits enhance peripheral nerve regeneration.

Here we have evaluated peripheral nerve regeneration with a porous biodegradable nerve conduit (PGGC), which was made from genipin-cross-linked gelatin. To examine the effect of pores, nonporous genipin-cross-linked gelatin conduit (GGC) was considered as the control. Both the PGGC and the GGC were dark blue in appearance with a concentric and round lumina. The PGGC featured an outer surface with pores of variable size homogeneously traversing, and a partially fenestrated inner surface connected by an open trabecular meshwork. The GGC had a rough outer surface whereas its inner lumen was smooth. Both PGGCs and GGCs had similar hydrophilicity on condition of the same material and cross-linking degree. The porosity of PGGCs and GGCs was 90.8 +/- 0.9% and 24.3 +/- 2.9%, respectively. The maximum tensile force of the GGCs (0.12 +/- 0.06 kN) exceeded that of the PGGCs (0.03 +/- 0.01 kN), but the PGGCs had a higher swelling ratio than GGCs at 0.5, 1, 3, 6, 12, 24, 48, 60, 72, and 84 h after soaking in deionized water. Cytotoxic testing revealed the soaking solutions of both of the tube composites would not produce cytotoxicity to cocultured Schwann cells. After subcutaneous implantation on the dorsal side of the rat, the PGGC was degraded completely after 12 weeks of implantation whereas a thin tissue capsule was formed encapsulating the partially degraded GGC. Biodegradability of both of the tube groups and their effectiveness as a guidance channel were examined as they were used to repair a 10 mm gap in the rat sciatic nerve. As a result, fragmentation of the GGC was still seen after 12 weeks of implantation, yet the PGGC had been completely degraded. Histological observation showed that numerous myelinated axons had crossed over the gap region in the PGGCs after 8 weeks of implantation despite only few myelinated axons and unmyelinated axons mostly surrounded by Schwann cells seen in the GGCs. In addition, the regenerated nerves in the PGGCs presented a significantly higher nerve conductive velocity than those in the GGCs (P < 0.05). Thus, the PGGCs can not only offer effective aids for regenerating nerves but also accelerate favorable nerve functional recovery compared with the GGCs.

Proliferation- and migration-enhancing effects of ginseng and ginsenoside Rg1 through IGF-I- and FGF-2-signaling pathways on RSC96 Schwann cells.

The aim of the present study is to evaluate the proliferation- and migration-enhancing effects of ginseng and its component, ginsenoside (Rg1) on RSC96 Schwann cells. We investigated the molecular signaling pathways, which include: (1) survival signaling, IGFs-IGFIR-Akt-Bcl2 and proliferative signaling, cell cycle factors and mitogen-activated protein kinase (MAPK) pathways, (2) migrating and anti-scar signaling, FGF-2-uPA-MMPs.We treated RSC96 cells with different concentrations (100, 200, 300, 400, 500 microg ml(-1)) of ginseng and its constituent, Rg1 (5, 10, 15, 20, 25 microg ml(-1)). We observed a proliferative effect in a dose-dependent manner by PCNA western blotting assay, MTT assay, and wound healing test. Furthermore, we also found in the results of western blotting assay, ginseng and Rg1 enhance protein expression of IGF-I pathway regulators, cell cycle controlling proteins, and MAPK signaling pathways to promote the cell proliferation. In addition, ginseng and Rg1 also stimulated the FGF-2-uPA-MMP 9 migrating pathway to enhance the migration of RSC96 Schwann cells. Using MAPK chemical inhibitors, U0126, SB203580, and SP600125, the proliferative effects of ginseng and Rg1 on RSC96 cells were identified to be MAPK signaling-dependent. On the basis of the results, applying appropriate doses of ginseng and Rg1 with biomedical materials would be a potential approach for enhancing neuron regeneration.

Evaluation of a multi-layer microbraided polylactic acid fiber-reinforced conduit for peripheral nerve regeneration.

We evaluated peripheral nerve regeneration using a biodegradable multi-layer microbraided polylactic acid (PLA) fiber-reinforced conduit. Biodegradability of the PLA conduit and its effectiveness as a guidance channel were examined as it was used to repair a 10 mm gap in the rat sciatic nerve. As a result, tube fragmentation was not obvious and successful regeneration through the gap occurred in all the conduits at 8 weeks after operation. These results indicate the superiority of the PLA materials and suggest that the multi-layer microbraided PLA fiber-reinforced conduits provide a promising tool for neuro-regeneration.

Effects of electrical stimulation at different frequencies on regeneration of transected peripheral nerve.

BACKGROUND: Electrical stimulation of damaged peripheral nerve may aid regeneration. OBJECTIVE: The purpose of this study was to determine whether 1 mA of percutaneous electrical stimulation at 1, 2, 20, or 200 Hz augments regeneration between the proximal and distal nerve stumps. METHODS: A10-mm gap was made in rat sciatic nerve by suturing the stumps into silicone rubber tubes. A control group received no stimulation. Starting 1 week after transection, electrical stimulation was applied between the cathode placed at the distal stump and the anode at the proximal stump every other day for 6 weeks. RESULTS: Higher frequency stimulation led to less regeneration compared to lower frequencies. Quantitative histology of the successfully regenerated nerves revealed that the groups receiving electrical treatment, especially at 2 Hz, had a more mature structure with a smaller cross-sectional area, more myelinated fibers, higher axon density, and higher ratio of blood vessel to total nerve area compared with the controls. Electrophysiology showed significantly shorter latency, longer duration, and faster conduction velocity. CONCLUSION: Electrical stimulation can have either a positive or negative impact on peripheral nerve regeneration. Clinical trials that combine stimulation with rehabilitation must determine the parameters that are most likely to be safe and effective.

IGF-II/mannose 6-phosphate receptor activation induces metalloproteinase-9 matrix activity and increases plasminogen activator expression in H9c2 cardiomyoblast cells.

The IGF-II/mannose 6-phosphate receptor (IGF2R) function in extracellular matrix (ECM) remodeling is known to occur as a result of transforming growth factor-beta (TGF-beta) activation and plasmin in the proteolytic cleavage level caused by the interaction between latent TGF-beta and urokinase plasminogen activator receptor (uPAR) respectively. In one of our previous studies, we found IGF-II and IGF2R dose-dependently correlated with the progression of pathological hypertrophy remodeling following complete abdominal aorta ligation. However, how this IGF2R signaling pathway responds specifically to IGF-II and regulates the myocardial ECM remodeling process is unclear. We found that IGF2R was aberrantly expressed in myocardial infarction scars. The matrix metalloproteinase-9 (MMP-9) zymographic activity was elevated in H9c2 cardiomyoblast cells treated with IGF-II, but not IGF-I. Treatment with Leu27IGF-II, an IGF2R specifically binding IGF-II analog, resulted in significant time-dependent increases in the MMP-9, tissue-type plasminogen activator (tPA), and urokinase plasminogen activator (uPA); and a reduction in the tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) protein expression. Furthermore, IGF2R expression inhibition by siRNA blocked the IGF-II-induced MMP-9 activity. We hypothesize that after IGF-II is bound with IGF2R, the resulting signal disrupts the balance in the MMP-9/TIMP-2 expression level and increases plasminogen activator (PAs) expression involved in the development of myocardial remodeling. If so, IGF2R signaling inhibition may have potential use in the development of therapies preventing heart fibrosis progression.

Influence of cross-linking degree of a biodegradable genipin-cross-linked gelatin guide on peripheral nerve regeneration.

We evaluated peripheral nerve regeneration using biodegradable genipin-cross-linked gelatin nerve conduits (GGCs) with three different cross-linking degrees, 24, 36 and 51%. Biocompatibility and biodegradability of the GGC and its efficiency as a guidance channel were examined based on the repair process of a 10-mm gap in the rat sciatic nerve. From this pilot study we concluded that GGCs with a mean cross-linking degree of 36% can ensure nerve regeneration with a more mature structure, as demonstrated by better developed epineural and perineural organisation and axonal development, as well as better-recovered electrophysiology with a relatively positive sciatic functional index and a shorter latency of the muscle action potential curve. Regenerated nerves in the GGCs with mean cross-linking degrees of 24 and 51% were less favourable, due to irritation caused by degradation material and compression by the remaining tube walls, respectively.

Ameliorating effect of emodin, a constitute of Polygonatum multiflorum, on cycloheximide-induced impairment of memory consolidation in rats.

The aim of the present study was intended to investigate the ameliorating effects of emodin on memory consolidation via cholinergic, serotonergic and GABAergic neuronal systems in rats. First, we evaluated the ameliorating effects of emodin on cycloheximide (CXM)-induced impairment of passive avoidance response in rats. Secondly, we clarified the role of cholinergic, serotonergic or GABAergic system on the ameliorating effect of emodin by using 5-HT1A receptor partial agonist, 5-HT2 receptor antagonist, GABAB agonist, GABAA antagonist and muscarinic receptor antagonist. Emodin protected the rat from CXM-induced memory consolidation impairment. The beneficial effect of emodin on CXM-induced memory consolidation impairment was amplified by 8-OH-DPAT (5-HT1A receptor partial agonist) and ritanserin (5-HT2 receptor antagonist), but reduced by scopolamine. These results suggested that the beneficial effect of emodin on CXM-induced memory consolidation impairment was amplified by serotonergic 5-HT1A-receptor partial agonist and 5-HT2 receptor antagonist but reduced by muscarinic receptor antagonist.

Synergistic effect of ginger and nifedipine on human platelet aggregation: a study in hypertensive patients and normal volunteers.

In this study, we evaluated the synergistic effect of ginger and nifedipine on anti-platelet aggregation in normal human volunteers and hypertensive patients. The results showed that the percentage of platelet aggregation induced by collagen, ADP and epinephrine in hypertensive patients was larger than that in normal volunteers. Either aspirin or ginger could potentiate the anti-platelet aggregation effect of nifedipine in normal volunteer and hypertensive patients. These results suggested that ginger and nifedipine possessed synergistic effect on anti-platelet aggregation. A combination of 1 g ginger with 10 mg nifedipine per day could be valuable for cardiovascular and cerebrovascular complication due to platelet aggregation.

Locally administered nerve growth factor suppresses ginsenoside Rb1-enhanced peripheral nerve regeneration.

A high-dose of nerve growth factor (NGF) mixed with ginsenoside Rb1 (GRb1) was encapsulated by collagen and placed in silicone rubber chambers, which were used to repair dissected Sprague-Dawley rat sciatic nerves with 15 mm gaps. Six weeks after surgery, no axons or Schwann cells were seen in these chambers. By comparison, nerves treated with collagen-GRb1 alone had regenerated axons and Schwann cells in their endoneurial areas. We suggest that excessive NGF may not promote but, rather, suppress developing nerves.