Objective To investigate the expression and significance of growth-associated protein 43 (GAP-43) in the dorsal root ganglion (DRG) and intervertebral disc in the rat model of intervertebral disc inflammation. Methods A total of 103 adult male Sprague Dawley rats (weighing, 200-250 g) were randomly divided into the experimental group (n=48), the control group (n=48), and the blank control group (n=7). Fluoro-gold (F-G) as tracer was injected into the L5, 6 intervertebral disc of 3 groups; after 7 days of F-G injection, complete Freund’s adjuvant (50 µL) and the same volume of saline were injected in the experimental group (to prepare the model of intervertebral disc inflammation) and the control group, respectively, and the blank control group had no further treatment. After 1, 3, 7, and 14 days, T13-L6 DRG and L5, 6 intervertebral disc of experimental group and control group were harvested to detect the GAP-43 by using fluorescent immunohistochemistry, in situ hybridization, and RT-PCR. The DRG and intervertebral disc of blank control group were also harvested after 8 days of F-G injection. Results Fluorescent immunohistochemistry results showed that the number of F-G-labeled GAP-43 immunoreaction (GAP-43-IR) cells of the DRGs in the experimental group was significantly higher than that in the control group (P lt; 0.05) at 3 days, and no significant difference was found at the other time points (P gt; 0.05). There was no significant difference in the cross-sectional area of F-G-labeled GAP-43-IR cells between the experimental group and the control group at each time point (P gt; 0.05). The co-expression of GAP-43 with calcitonin gene-related peptide (CGRP) and isolectin B4 (IB4)-binding glycoprotein exhibited that the expression of CGRP was 91.4% ± 7.4% in the control group and was 87.6% ± 7.8% in the experimental group, showing no significant difference between 2 groups (P gt; 0.05). There was no IB4-binding glycoprotein expression in GAP-43-IR cells of the DRGs in 2 groups. The expressions of GAP-43, CGRP, and IB4-positive nerve fibers in the intervertebral disc exhibited that the GAP-43-IR nerve fibers in the experimental group were significantly more than that in the control group (P lt; 0.05), but no significant difference was found in the expression of CGRP between 2 groups (P gt; 0.05); and there was no IB4-binding glycoprotein expression in GAP-43-IR nerve fibers of the intervertebral disc in 2 group. In situ hybridization and RT-PCR detection showed that the positive expression cells ratio of GAP-43 mRNA and the level of GAP- 43 mRNA were significantly higher in the experimental group than in the control group at 1 day (P lt; 0.05), and no significant difference was found at the other time points (P gt; 0.05). Conclusion Intradiscal inflammatory environment may induce the expression of GAP-43, and potentially promote the nerve fiber ingrowth of rat.
Objective Bone marrow mesenchymal stem cells (BMSCs), as replacement cells of Schwann cells, can increase the effect of peripheral nerve repair. However, it has not yet reached any agreement to add the appropriate number of seeded cells in nerve scaffold. To investigate the effect of different number of BMSCs on the growth of rat dorsal root gangl ia(DRG). Methods Three 4-week-old Sprague Dawley (SD) rats (weighing 80-100 g) were selected to isolate BMSCs, whichwere cultured in vitro. Three 1- to 2-day-old SD rats (weighing 4-6 g) were selected to prepare DRG. BMSCs at passage 3 were used to prepare BMSCs-fibrin glue complex. According to different number of BMSCs at passage 3 in fibrin glue, experiment was divided into group A (1 × 103), group B (1 × 104), group C (1 × 105), and group D (0, blank control), and BMSCs were cocultured with rat DRG. The axon length of DRG, Schwann cell migration distance, and axon area index were quantitatively evaluated by morphology, neurofilament 200, and Schwann cells S-100 immunofluorescence staining after cultured for 48 hours. Results Some long cell processes formed in BMSCs at 48 hours; migration of Schwann cells and axons growth from the DRG were observed, growing in every direction. BMSCs in fibrin glue had the biological activity and could effect DRG growth. The axon length of DRG and Schwann cell migration distance in groups A, B, and C were significantly greater than those in group D (P lt; 0.05). The axon length of DRG and Schwann cell migration distance in group C were significantly less than those in group B (P lt; 0.05), but there was no significant difference between group A and group C, and between group A and group B (P gt; 0.05). The axon area index in groups A and B was significantly greater than that in group D (P lt; 0.05), but there was no significant difference between group C and group D (P gt; 0.05); there was no significant difference in groups A, B, and C (P gt; 0.05). Conclusion In vitro study on DRG culture experiments is an ideal objective neural model of nerve regeneration. The effect of different number of BMSCs in fibrin glue on the growth of DRG has dose-effect relationship. It can provide a theoretical basis for the appropriate choice of the BMSCs number for tissue engineered nerve.
Objective To establ ish the methods to get high activity, high purity, and adequate Schwann cells (SCs), and to provide sufficient seed cells for the peripheral nerve repair. Methods Six 5-day-old, male or female, Sprague Dawley rats were selected and the sciatic nerve (control group) and dorsal root gangl ion (DRG) (ex perimental group) were harvested.Then the sciatic nerves and DRG were digested by co-enzyme and dispersed by medium containing serum to isolate SCs. Freshlyisolated SCs from rats were cultured, purified and subcultured. The 1st generation of SCs were chosen to draw the growth curve of SCs by the counting method and to detect the prol iferation of SCs by MTT assay at 8 days of culture, the purity of SCs by immunocytochemistry of anti-S-100 and the brain-derived neurotrophic factor (BDNF) concentration by ELISA. Results A total of 36-43 DRGs could be obtained in each rat. The number of obtained single SC in experimental group [(7.5 ± 0.6）× 106] was significantly higher than that in control group [(3.5 ± 0.4）× 106 ] (t=13.175, P=0.000). SCs reached logarithm prol iferation phase at 3 days. With time, the cell number and the prol iferation absorbance (A) value of 2 groups all showed upward trend. The number and A value of experimental group were significantly higher than those of control group (P lt; 0.05). The SCs purity of experimental group (92.08% ± 3.45%) was significantly higher than that of control group (77.50% ± 3.57%) (t=6.689, P=0.001).The concentrations of BDNF at 3 days and 5 days in experimental group were significantly higher than those of control group (P lt; 0.05). Conclusion The sufficient amount, high purity, and viabil ity of SCs from DRGs can meet the needs of studies on peripheral nerve repairment.
Objective Native extracellular matrix (ECM) is comprised of a complex network of structural and regulatory proteins that are arrayed into a tissue-specific, biomechanically optimal, fibrous matrix. The multifunctional nature of the native ECM will need to be considered in the design and fabrication of tissue engineering scaffolds. To investigate the extraction techniques of naturally derived nerve ECM and the feasibil ity of nerve tissue engineering scaffold. Methods Ten fresh canine sciatic nerves were harvested; nerve ECM material was prepared by hypotonic freeze-thawing, mechanicalgrinding, and differential centrifugation. The ECM was observed by scanning electron microscope. Immunofluorescencestaining was performed to detect specific ECM proteins including collagen type I, laminin, and fibronectin. Total collagen and glycosaminoglycan (GAG) contents were assessed using biochemical assays. The degree of decellularization was evaluated with staining for nuclei using Hoechst33258. The dorsal root gangl ion and Schwann cells of rats were respectively seeded onto nerve tissue-specific ECM films. The biocompatibil ity was observed by specific antibodies for cell markers. Results Scanning electron microscope analysis revealed that nerve-derived ECM consisted of a nanofibrous structure, which diameter was 30-130 nm. Immunofluorescence staining confirmed that the nerve-derived ECM was made up of collagen type I, laminin, and fibronectin. The histological staining showed that the staining results of sirius red, Safranin O, and toluidine blue were positive. Hoechst33258 staining showed no DNA within the decellularized ECM. Those ECM films had good biocompatibil ity for dorsal root gangl ion and Schwann cells. The cotents of total collagen and GAG in the nerve-derived ECM were (114.88 ± 13.33) μg/ mg and (17.52 ± 2.34) μg/mg, showing significant difference in the content of total collagen (P lt; 0.01) and no significant difference in the content of GAG (P gt; 0.05) when compared with the contents of normal nerve tissue [(54.07 ± 5.06) μg/mg and (25.25 ± 1.56) μg/mg)]. The results of immunofluorescence staining were positive for neurofilament 200 after 7 days and for S100 after 2 days. Conclusion Nerve-derived ECM is rich in collagen type I, laminin, and fibronectin and has good biocompatibil ity, so it can be used as a nerve tissue engineering scaffold.
OBJECTIVE: To research the protective effect of Schwann cell and extracellular matrix (ECM) gel on neurons in dorsal root ganglion. METHODS: 1. Schwann cells were seeded into 30% ECM at 1 x 10(8)/ml and then implanted into PLA hollow fiber conduits to repair 10 mm length defects of rat sciatic nerve, and histological observation was taken at 8 and 12 weeks after operation. 2. To observe the survival of Schwann cells, Schwann cells labeled BrdU were seeded into 30% ECM at 1 x 10(8)/ml and then implanted into PLA hollow fiber conduits to repair 10 mm length defects of rat sciatic nerve. Histological observation and immunohistochemical method stained with BrdU were done at 3 and 6 weeks after operation. RESULTS: 1. When seeded into ECM gel and transplanted into rats, most of the Schwann cells survived to 3 weeks and a part of them survived up to 6 weeks. 2. The survival neuron ratios of Schwann cells with ECM gel group and ECM gel group were 83.5% and 81.3% respectively, and significantly higher than that of saline group (72.9%, P lt; 0.05). CONCLUSION: When seeded into ECM gel and transplanted into rats, most of the Schwann cells survive and protect 83.5% neurons in dorsal root ganglion from retrograde death.