RESUMEN
OBJECTIVE: To investigate the in vivo degradation and histocompatibility of modified chitosan based on conductive composite nerve conduit, so as to provide a new scaffold material for the construction of tissue engineered nerve. METHODS: The nano polypyrrole (PPy) was synthesized by microemulsion polymerization, blended with chitosan, and then formed conduit by injecting the mixed solution into a customized conduit formation model. After freeze-drying and deacidification, the nano PPy/chitosan composite conduit (CP conduit) was prepared. Then the CP conduits with different acetyl degree were resulted undergoing varying acetylation for 30, 60, and 90 minutes (CAP1, CAP2, CAP3 conduits). Fourier infrared absorption spectrum and scanning electron microscopy (SEM) were used to identify the conduits. And the conductivity was measured by four-probe conductometer. The above conduits were implanted after the subcutaneous fascial tunnels were made symmetrically on both sides of the back of 30 female Sprague Dawley rats. At 2, 4, 6, 8, 10, and 12 weeks after operation, the morphology, the microstructure, and the degradation rate were observed and measured to assess the in vivo degradation of conduits. HE staining and anti-macrophage immunofluorescence staining were performed to observe the histocompatibility in vivo. RESULTS: The characteristic peaks of the amide â ¡ band around 1 562 cm -1 appeared after being acetylated, indicating that the acetylation modification of chitosan was successful. There was no significant difference in conductivity between conduits ( P>0.05). SEM observation showed that the surfaces of the conduits in all groups were similar with relatively smooth surface and compact structure. After the conduits were implanted into the rats, with the extension of time, all conduits were collapsed, especially on the CAP3 conduit. All conduits had different degrees of mass loss, and the higher the degree of acetylation, the greater the mass change ( P<0.05). SEM observation showed that there were more pores at 12 weeks after implantation, and the pores showed an increasing trend as the degree of acetylation increased. Histological observation showed that there were more macrophages and lymphocytes infiltration in each group at the early stage. With the extension of implantation time, lymphocytes decreased, fibroblasts increased, and collagen fibers proliferated significantly. CONCLUSION: The modified chitosan basedon conductive composite nerve conduit made of nano-PPy/chitosan composite with different acetylation degrees has good biocompatibility, conductivity, and biodegradability correlated with acetylation degree in vivo, which provide a new scaffold material for the construction of tissue engineered nerve.
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Quitosano , Animales , Femenino , Histocompatibilidad , Regeneración Nerviosa , Ratas , Ratas Sprague-Dawley , Nervio CiáticoRESUMEN
Objective: To prepare nano polypyrrole (PPy)/chitin composite membrane and observe their biocompatibility. Methods: The nano PPy was synthesized by microemulsion polymerization, blended with chitosan and then formed membranes. The membranes were then modified by acetylation to get the experimental membranes (nano PPy/chitin composite membranes, group A). The chitosan membranes (group B) and chitin ones (group C) modified by acetylation acted as control. Scanning electron microscopy and FT-IR spectra were used to identify the nano PPy and the membranes of each group. And the conductivity of membranes of each group was measured. Schwann cells were co-cultured in vitro with each group membranes to observe the biocompatibility by inverted microscope observing, living cell staining, cell counting, and immunofluorescence staining. The lysozyme solution was used to evaluate the degradation of the membranes in vitro. Results: The FT-IR spectra showed that the characteristic vibrational absorption peaks of C=C from nano PPy appeared at 1 543.4 cm -1 and 1 458.4 cm -1. Scanning electron microscopy observation revealed that the size of nano PPy particles was about 100-200 nm. The nano PPy particles were synthesized. It was successful to turn chitosan to chitin by the acetylation, which was investigated by FT-IR analysis of membranes in groups A and C. The characteristic peaks of the amide â ¡ band around 1 562 cm -1 appeared after acetylated modification. Conductivity test showed that the conductivity of membranes in group A was about (1.259 2±0.005 7)×10 -3 S/cm, while the conductivity of the membranes in groups B and C was not detected. The nano PPy particles uniformly distributed on the surface of membranes in group A were observed by scanning electron microscope; the membranes in control groups were smooth. As a result, the nano PPy/chitin composite membranes with electrical conductivity were obtained. The cultured Schwann cells were found to survive with good function by fluorescein diacetate live cell staining, soluble protein-100 immunofluorescence staining, and inverted microscope observing. The cell counting showed that the proliferation of Schwann cells after 2 days and 4 days of group A was more than that of the two control groups, and the differences were significant ( P<0.05). It indicated that the nano PPy/chitin composite membranes had better ability of adhesion and proliferation than those of chitosan and chitin membranes. The degradation of membranes in vitro showed that the degradation rates of membranes in groups A and C were significantly higher than those in group B at all time points ( P<0.05). In a word, the degradation performance of the membranes modified by acetylation was better than that of chitosan membranes under the same condition. Conclusion: The nano PPy and chitosan can be blended and modified by acetylation successfully. Nano PPy/chitin composite membranes had electrical conductivity, degradability, and good biocompatibility in vitro.
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Quitina , Polímeros , Pirroles , Quitosano , Ensayo de Materiales , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Objective: To explore the effect of short-term low-frequency electrical stimulation (SLES) during operation on nerve regeneration in delayed peripheral nerve injury with long gap. Methods: Thirty female adult Sprague Dawley rats, weighing 160-180 g, were used to prepare 13-mm defect model by trimming the nerve stumps. Then all rats were randomly divided into 2 groups, 15 rats in each group. After nerve defect was bridged by the contralateral normal sciatic nerve, SLES was applied in the experimental group, but was not in the control group. The spinal cords and dorsal root ganglions (DRGs) were harvested to carry out immunofluorescence histochemistry double staining for growth-associated proteins 43 (GAP-43) and brain-derived neurotrophic factor (BDNF) at 1, 2, and 7 days after repair. Fluorogold (FG) retrograde tracing was performed at 3 months after repair. The mid-portion regenerated segments were harvested to perform Meyer's trichrome staining, immunofluorescence double staining for neurofilament (NF) and soluble protein 100 (S-100) on the transversely or longitudinal sections at 3 months after repair. The segment of the distal sciatic nerve trunk was harvested for electron microscopy and morphometric analyses to measure the diameter of the myelinated axons, thickness of myelin sheaths, the G ratio, and the density of the myelinated nerve fibers. The gastrocnemius muscles of the operated sides were harvested to measure the relative wet weight ratios. Karnovsky-Root cholinesterase staining of the motor endplate was carried out. Results: In the experimental group, the expressions of GAP-43 and BDNF were higher than those in the control group at 1 and 2 days after repair. The number of labeled neurons in the anterior horn of gray matter in the spinal cord and DRGs at the operated side from the experimental group was more than that from the control group. Meyer's trichrome staining, immunofluorescence double staining, and the electron microscopy observation showed that the regenerated nerves were observed to develop better in the experimental group than the control group. The relative wet weight ratio of experimental group was significantly higher than that of the control group ( t=4.633, P=0.000). The size and the shape of the motor endplates in the experimental group were better than those in the control group. Conclusion: SLES can promote the regeneration ability of the short-term (1 month) delayed nerve injury with long gap to a certain extent.
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Estimulación Eléctrica , Regeneración Nerviosa , Nervio Ciático/crecimiento & desarrollo , Animales , Axones , Femenino , Distribución Aleatoria , Ratas , Ratas Sprague-DawleyRESUMEN
Unsatisfactory efficacy of clinical cure for long-term delayed injuries and other disadvantages such as the low regeneration rate and speed of axotomized neurons and the questionable reinnervation ability of atrophic target organ lead to inaction to the long-term delayed injuries. Here we attempted to use autologous nerve to bridge a long-term delayed 10-mm defect in SD rats based on some previous positive messages of basic and clinical research. In this study, for experimental groups, the rat sciatic nerve had been transected leaving a 10-mm defect, which was maintained for 3 or 6 months before implantation with the autologous graft. The non-grafted animals served as negative control. Measuring with electrophysiological and histological techniques, we find: (1) A number of long-term axotomized neurons survived and sustained certain degree of axonal regenerative capacity; (2) A few denervated Schwann cells survived and retained their ability to provide trophic support and myelinate axons in at least 6 months; (3) the chronically denervated muscle can partially be reinnervated by regenerated axons. But the quantity and the quality of the regenerated nerve fibers and the reinnervated muscle fibers were all poor. Thus these observations provide new positive morphological proof of nerve regeneration after long-term defects and further studies will be needed to increase the survival rate and the regenerative speed of long-term chronic axotomized neurons, enhance the support provided by denervated distal stumps and protect the target muscle.
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Regeneración Nerviosa , Nervio Ciático/trasplante , Neuropatía Ciática/patología , Neuropatía Ciática/cirugía , Animales , Femenino , Regeneración Nerviosa/fisiología , Ratas , Ratas Sprague-Dawley , Factores de Tiempo , Trasplante Autólogo/métodosRESUMEN
The glycemia-sensitive neurons of the ventromedial hypothalamic nucleus (VMN) have traditionally been implicated in feeding regulation. Some studies reported that the neuronal activity of the VMN could be modulated by inputs from the gastric vagal afferent, and the cerebellum might participate in regulating non-somatic visceral activities via the cerebellohypothalamic projections. The present study was therefore undertaken to investigate whether the inputs from the gastric vagal nerves and the cerebellar interpositus nucleus (IN) could reach and converge onto single VMN neurons, especially those glycemia-sensitive ones. Among recorded 283 VMN neurons, 187 (66.1%) and 139 (49.1%) responded to the gastric vagal and the cerebellar IN stimulations, respectively. Within the VMN neurons that were responsive to either of the gastric vagal or cerebellar IN stimulation, 91 responded to both of the stimuli, suggesting a convergence of gastric vagal and cerebellar inputs on the cells. When the gastric vagal nerves and cerebellar IN were stimulated simultaneously, a summation of the responses could be observed (n = 22). Moreover, of the 91 cells that responded to both of the gastric vagal and cerebellar IN stimuli, 61 (67.0%) were identified to be glycemia-sensitive neurons. These results demonstrate that the visceral signals conveyed by the gastric vagal afferents and the somatic information forwarded by the cerebellar IN could converge onto single VMN neurons, especially the glycemia-sensitive neurons. And the findings suggest that an integration of the somatic-visceral response related to the food intake could take place in the VMN and the cerebellum might actively participate in the short-term feeding regulation through the cerebellohypothalamic projections.