Effects of different dosage of dexamethasone on behavioral, electrophysiological, and histomorphological recovery in a chronic sciatic nerve compression model.

OBJECTIVE: To investigate the effects of different doses of topical dexamethasone (Dex) on sciatic nerves with simulated compressive neuropathy. METHODS: Thirty-two Wistar rats were divided into four groups of 8: Sham group: no compression of the sciatic nerve + no treatment; Saline: chronic compression of the left sciatic nerve for 4 weeks + saline; 0.8% Dex: chronic compression + 0.8 mg of Dex; 3.2% Dex: chronic compression + 3.2 mg of Dex. Two sponge strips soaked with saline or Dex were placed under and over the nerve for 30 min in both Dex groups. Mixed-nerve-elicited somatosensory evoked potentials (M-SSEPs) and compound muscle action potentials (CMAPs) were measured to verify the compressive neuropathy in post-treatment follow-up. Behavioral observations of thermal hyperalgesia tests were quantified before electrophysiological examinations. Treated and contralateral nerves were harvested for histomorphological analysis. RESULTS: M-SSEP and CMAP amplitudes significantly decreased and latencies were significantly prolonged on postcompression thermal hyperalgesia tests. Rats in both Dex groups showed significant improvement in both sensory and motor conductive values and in neurological function, as well as increased mean myelin diameter on the final histomorphological examination. For rats in the saline group, these parameters showed incomplete recovery compared with the Sham group and the precompression baseline. Moreover, the changes after Dex treatment were not dose-dependent. CONCLUSIONS: Topical Dex reversed electrophysiological, behavioral, and structural changes in chronically compressed sciatic nerves. Differences between the beneficial effects of high-dose and low-dose Dex were nonsignificant.

Neocartilage formation from mesenchymal stem cells grown in type II collagen-hyaluronan composite scaffolds.

Three-dimensional (3D) collagen type II-hyaluronan (HA) composite scaffolds (CII-HA) which mimics the extracellular environment of natural cartilage were fabricated in this study. Rheological measurements demonstrated that the incorporation of HA increased the compression modulus of the scaffolds. An initial in vitro evaluation showed that scaffolds seeded with porcine chondrocytes formed cartilaginous-like tissue after 8 weeks, and HA functioned to promote the growth of chondrocytes into scaffolds. Placenta-derived multipotent cells (PDMC) and gingival fibroblasts (GF) were seeded on tissue culture polystyrene (TCPS), CII-HA films, and small intestinal submucosa (SIS) sheets for comparing their chondrogenesis differentiation potentials with those of adipose-derived adult stem cells (ADAS) and bone marrow-derived mesenchymal stem cells (BMSC). Among different cells, PDMC showed the greatest chondrogenic differentiation potential on both CII-HA films and SIS sheets upon TGF-ß3 induction, followed by GF. This was evidenced by the up-regulation of chondrogenic genes (Sox9, aggrecan, and collagen type II), which was not observed for cells grown on TCPS. This finding suggested the essential role of substrate materials in the chondrogenic differentiation of PDMC and GF. Neocartilage formation was more obvious in both PDMC and GF cells plated on CII-HA composite scaffolds vs. 8-layer SIS at 28 days in vitro. Finally, implantation of PDMC/CII-HA constructs into NOD-SCID mice confirmed the formation of tissue-engineered cartilage in vivo.

Intra-articular injections of sodium hyaluronate (Hyalgan®) in osteoarthritis of the knee. a randomized, controlled, double-blind, multicenter trial in the Asian population.

BACKGROUND: The efficacy and tolerability of 500-730 kDa sodium hyaluronate (Hyalgan®) for treatment of osteoarthritis (OA) pain has been established in clinical trials, but few data are available in the Asian population. We conducted a randomized, double-blind, multicenter, placebo-controlled study to evaluate the efficacy and tolerability of this preparation in a Taiwanese population. METHODS: Two hundred patients with mild to moderate OA of the knee were randomized to receive five weekly intra-articular injections of sodium hyaluronate or placebo. The primary efficacy outcome was the change from baseline to Week 25 in patients' evaluation of pain using a 100-mm visual analog scale (VAS) during the 50-foot walking test. Additional outcomes included Western Ontario and McMaster Universities (WOMAC) scores, time on the 50-foot walking test, patient's and investigator's subjective assessment of effectiveness, acetaminophen consumption, and the amounts of synovial fluid. RESULTS: The Hyalgan® treatment group showed a significantly greater improvement from baseline to Week 25 in VAS pain on the 50-foot walking test than the placebo group (p = 0.0020). The Hyalgan® group revealed significant improvements from baseline to week 25 in WOMAC pain and function score than the placebo group (p = 0.005 and 0.0038, respectively) Other outcomes, such as time on the 50-foot walking test and subjective assessment of effectiveness, did not show any significant difference between groups. Both groups were safe and well tolerated. CONCLUSIONS: The present study suggests that five weekly intra-articular injections of sodium hyaluronate are well tolerated, can provide sustained relief of pain, and can improve function in Asian patients with osteoarthritis of the knee. TRIAL REGISTRATION: Therapeutic study, Level I-1a (randomized controlled trial with a significant difference).

Cytotoxicity and immunological response of gold and silver nanoparticles of different sizes.

The immunological response of macrophages to physically produced pure Au and Ag nanoparticles (NPs) (in three different sizes) is investigated in vitro. The treatment of either type of NP at > or =10 ppm dramatically decreases the population and increases the size of the macrophages. Both NPs enter the cells but only AuNPs (especially those with smaller diamter) up-regulate the expressions of proinflammatory genes interlukin-1 (IL-1), interlukin-6 (IL-6), and tumor necrosis factor (TNF-alpha). Transmission electron microscopy images show that AuNPs and AgNPs are both trapped in vesicles in the cytoplasma, but only AuNPs are organized into a circular pattern. It is speculated that part of the negatively charged AuNPs might adsorb serum protein and enter cells via the more complicated endocytotic pathway, which results in higher cytotoxicity and immunological response of AuNPs as compared to AgNPS.

Evaluation of chondrocyte growth in the highly porous scaffolds made by fused deposition manufacturing (FDM) filled with type II collagen.

Highly porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds for cartilage tissue engineering were fabricated in this study using the fused deposition manufacturing (FDM) process and were further modified by type II collagen. The average molecular weight of PLGA decreased to about 60% of the original value after the melt-extrusion process. Type II collagen exhibited sponge-like structure and filled the macroporous FDM scaffolds. An increase of the fiber spacing resulted in an increase of the porosity. The storage modulus of FDM scaffolds with a large fiber spacing was comparable to that of the native porcine articular cartilage. Although the FDM hybrid scaffolds were swollen in various extents after 28 days of in vitro culture, the seeded chondrocytes were well distributed in the interior of the scaffolds with a large fiber spacing and neocartilage was formed around the scaffolds. The study also suggested that a low processing temperature may be required to produce PLGA precision scaffolds using FDM.

Heterobifunctional poly(ethylene glycol)-tethered bone morphogenetic protein-2-stimulated bone marrow mesenchymal stromal cell differentiation and osteogenesis.

We describe a biomimetic mode of insoluble signaling stimulation to provide target delivery of bone morphogenetic protein-2 (BMP-2), with the aim of prolonging the retention of BMP-2 use in bone tissue engineering and to enable its localized release in response to cellular activity. In our novel localization process, we used heterobifunctional acrylate-N-hydroxysuccinimide poly(ethylene glycol) (PEG) as a spacer to tether BMP-2 onto a poly(lactide-co-glycolide) scaffold. Use of PEG-tethered BMP-2 was feasible because BMP-2 retained its activity after covalent conjugation. The PEG-tethered BMP-2 conjugate sustained stimulation and retained its mitogenic activity, notably affecting pluripotent stem cell proliferation and differentiation. We seeded the scaffolds with bone marrow-derived mesenchymal stromal cells as progenitor cells to evaluate their morphology and phenotypic expression. We also created bilateral, full-thickness cranial defects in rabbits to investigate the osteogenic effect of cultured mesenchymal stromal cells on bone regeneration in vivo. Histomorphometry and histology demonstrated that the PEG-tethered BMP-2 conjugate enhanced de novo bone formation after surgery. Our work revealed the potential for biomimetic surface engineering by entrapping signaling growth factor to stimulate osteogenesis. Our technique may provide a new platform for bone-engineered stem cell therapies.

The response of articular chondrocytes to type II collagen-Au nanocomposites.

The nanocomposites (denoted "CII-Au") of porcine type II collagen (CII) with 0.05, 0.1, 0.5, 1, or 2.5% (wt/wt) Au nanoparticles ( approximately 5 nm) were fabricated for potential use in cartilage tissue engineering. Au formed clusters on the surface of all nanocomposites and appeared to distribute along the collagen fibrils inside the matrix. The addition of Au at low concentrations (< or =0.5%) increased the modulus and viscosity, as well as the free radical-scavenging ability. These effects decreased at higher concentrations of Au. The chondrocytes on CII-Au became spindle-like with lamellipodia formation. Cell proliferation on CII-Au 0.1% was promoted. Nitric oxide (NO) in the culture medium was reduced by CII-Au 0.05% and CII-Au 0.1%. Type I collagen, aggrecan, and Sox 9 gene expressions increased with an increased Au content, but slightly decreased at 2.5% Au. There was no significant difference in the CII gene expression. The cellular uptake of Au was observed but less than that which occurred when 10 ppm of Au was added in culture medium. Chondrocytes cultured with < or =10 ppm of Au nanoparticles showed neither cytotoxicity nor change in gene expression. Au at an appropriate amount could be well dispersed in CII, and enhanced the material modulus, antioxidant effect, as well as the chondrocyte growth and matrix production.

Evaluation of the growth of chondrocytes and osteoblasts seeded into precision scaffolds fabricated by fused deposition manufacturing.

In this study, fused deposition manufacturing (FDM) was utilized to fabricate the precision scaffolds for cartilage and bone regeneration. Cell seeding into such scaffolds was evaluated. For poly(D,l-lactide) (PLA) scaffolds used for cartilage regeneration, the structure with larger inner space, four direction stacking (4D) and small interval of fibers were better. Chondrocyte proliferated well with matrix accumulation in precision scaffolds coated with type II collagen at 4 weeks of in vitro culture. The seeding efficiency of osteoblasts in most polycaprolactone (PCL) scaffolds used for bone regeneration could arrive 50% of original cell seeding density, and the amount of cells in scaffolds increased to double fold after 2 weeks of in vitro culture. The histological cross-section also revealed proliferation and mineralization of osteoblasts among the PCL fibers. The results indicated that the highly porous and interconnected structure of precision scaffolds could benefit cell ingrowth.

Targeted delivery system for juxtacrine signaling growth factor based on rhBMP-2-mediated carrier-protein conjugation.

We propose a model of artificial juxtacrine signaling for the controlled release of recombinant human bone morphogenetic protein-2 (rhBMP-2) suitable for guided bone regeneration. A porous three-dimensional scaffold of poly-(lactide-co-glycolide) was fabricated by means of gel molding and particulate leaching. Collagen immobilization onto the scaffold surface was produced by performing photo-induced graft polymerization of acrylic acid, and rhBMP-2 was tethered to the collagenous surface by covalent conjugation. On pharmacokinetic analysis, in vitro enzyme-linked immunosorbent and alkaline phosphatase assays revealed sustained, slow release of rhBMP-2 over 28 days, with a cumulative release of one third of the initial load diffusing out of the scaffold. Conjugation of rhBMP-2 inhibited the free lateral diffusion and internalization of the activated complex of rhBMP-2 and the bone morphogenetic protein receptor. Osteoprogenitor cells were used as bone precursors to determine the expression of biosignaling growth factor in regulating cell proliferation and differentiation. To identify the phenotype of cells seeded on the rhBMP-2-conjugated scaffold, cellular activity was evaluated with scanning electron microscopy and with viability, histological, and immunohistochemical testing. The rhBMP-2-conjugated scaffold prolonged stimulation of intracellular signal proteins in cells. Enhancement of cell growth and differentiation was considered a consequence of juxtacrine signaling transduction. Animal studies of rhBMP-2-containing filling implants showed evidence of resorption and de novo bone formation. The present study revealed the potential of biomimetic constructs with co-immobilized adhesion and growth factors to induce osteoinduction and osteogenesis. Such constructs may be useful as synthetic bone-graft materials in orthopaedic tissue engineering.

The effect of ultrasound stimulation versus bioreactors on neocartilage formation in tissue engineering scaffolds seeded with human chondrocytes in vitro.

Pulsed ultrasound (1 MHz, 67 mW/cm(2) Ispta, and 10 min/day) promoted cell proliferation and matrix deposition in low-density 2D ( approximately 6 x 10(3)cells/cm(2)) as well as 3D ( approximately 4 x 10(6)cells/cm(3)) chondrocyte cultures. The beneficial effect of ultrasound on neocartilage formation only last 28 days, shorter than that of bioreactors.

Influence of temperature and gonadal steroids on the ontogenetic expression of brain serotonin 1A and 1D receptors during the critical period of sexual differentiation in tilapia, Oreochromis mossambicus.

cDNA sequences of serotonin (5-hydroxytryptamine, 5-HT) 1A and 1D receptors were cloned from the tilapia, Oreochromis mossambicus, brain. The influence of both gonadal steroids and temperature on the ontogenetic expression of brain 5-HT1A and 5-HT1D receptors from days 5 to 15 post-hatch, a critical period of sexual differentiation, was investigated using quantitative real-time reverse transcription-polymerase chain reaction. Neither estrogen nor methyltestosterone had an effect on the ontogenetic expression of 5-HT1A or 5-HT1D receptors. Between days 5 and 10 post-hatch, a critical period for low-temperature-induced feminization, we found no significant difference in the ontogenetic expression of 5-HT1A between exposure to low and elevated temperature. A similar result was found for 5-HT1D. Between days 10 and 15 post-hatch, a critical period for elevated-temperature-induced masculinization, the ontogenetic expression of neither brain 5-HT1A nor 5-HT1D was altered by exposure to elevated temperature. These results suggest that neither brain 5-HT1A nor 5-HT1D plays a critical role in either gonadal steroid- or temperature-induced sexual differentiation.

Effects of photoperiod on the development of the central glutamate system in tilapia, Oreochromis mossambicus.

The effect of photoperiod (light/dark cycle) on the development of the central glutamate system was investigated in tilapia, Oreochromis mossambicus. Tilapia, at 0, 5, and 10 days posthatching were respectively divided into three equal groups to be kept in different photoperiods: 12/12 h, 24/0 h (full day), and 0/24 h (full night). Neither the full-day nor the full-night photoperiod showed any influence on the development of the central glutamate system, including glutamate content and mRNA expression of glutamate receptor 3 alpha, in the developing tilapia brain. These results suggest that neither constant light nor dark photoperiods affected the influence of the central glutamate system on brain sex differentiation in tilapia during the early developing period.

Photoperiod affects the development of central neurotransmitter systems of tilapia, Oreochromis mossambicus.

The effects of photoperiod on the development of central neurotransmitters were investigated with tilapia, Oreochromis mossambicus. Zero-day-old (the hatching day) tilapia were raised in three different photoperiods (light/dark cycle): 12/1, 24/0, and 0/24 h, respectively. On the 5th day, brain serotonin (5-HT), norepinephrine (NE), gamma-aminobutyric acid (GABA), and glutamate (Glu) contents were quantified by a high-performance liquid chromatograph with electrochemical detection. Similar experiments were performed on the 5-, 10-, 15-, 20-, and 25-day-olds. These results showed that the photoperiod influenced both brain NE and GABA contents during its respective restricted period, before days 10 posthatching. Brain 5-HT content was influenced, either facilitated or suppressed according to the developing stage, whereas, brain Glu content was not altered by the different photoperiod exposure throughout the present studies.

The effect of an RGD-containing fusion protein CBD-RGD in promoting cellular adhesion.

The effect of a recombinant RGD (arginine-glycine-aspartic acid)-containing fusion protein, cellulose-binding domain (CBD)-RGD, on the cellular adhesion to a biomedical polyurethane (PU) was evaluated. A series of different cell lines, as well as freshly harvested animal cells, were grown on the PU surfaces with or without CBD-RGD, in serum or serum-free media. The results showed that the enhancement of cellular attachment by CBD-RGD varied with cell types. This is believed to be a result of the unique integrin receptors on each type of cell surface. The existence of certain divalent ions (Mg2+ and Mn2+) may increase the efficacy of the CBD-RGD, in a cell type-dependent manner. The fusion protein was also found to inhibit the platelet activation. The effect of CBD-RGD was further examined in two other substrate materials, poly(L-lactide) (PLLA) and poly(lactide-co-glycolide) (PLGA). The effect on cellular adhesion correlated with the amount of CBD-RGD physically adsorbed on the material surface.

Real-time electrochemical recording of dopamine release under optogenetic stimulation.

Dopaminergic PC12 cells can synthesize and release dopamine, providing a good cellular model for investigating dopamine regulation. Optogenetic stimulation of channelrhodopsin-2 provides high spatial and temporal precision for selective stimulation as a powerful neuromodulation tool for neuroscience studies. The aim of this study is to measure dopamine release from dopaminergic PC12 cells under optogenetic stimulation using electrochemical recording of self-assembled monolayers modified microelectrode with amperometric measurement in real time. The activation of PC12 cells under various optogenetic stimulation schemes are characterized by measuring single-cell Ca(2+) imaging. After 10 seconds of optogenetic stimulation, the evoked intracellular Ca(2+) level and dopamine current of channelrhodopsin-2-transfected PC12 cells were 1.6- and 3.5-fold higher than those of the control cells. The optogenetic stimulation effects on Ca(2+) influx and dopamine release were 81% and 63% inhibition by using a Ca(2+) channel antagonist Nifedipine. The results indicate that optogenetic stimulation can evoke voltage-gated Ca(2+) channel-dependent dopamine exocytosis from PC12 cells in a cell specific, temporally precise and dose-dependent manner. This proposed dopamine recording system can be developed to be a good cell model for dopamine regulation and drug screening in vitro, or dopaminergic cell implantation therapy in vivo using optogenetic stimulation in a precise and convenient way.

In vitro and in vivo evaluation of chitosan-gelatin scaffolds for cartilage tissue engineering.

Chitosan-gelatin polyelectrolyte complexes were fabricated and evaluated as tissue engineering scaffolds for cartilage regeneration in vitro and in vivo. The crosslinker for the gelatin component was selected among glutaraldehyde, bisepoxy, and a water-soluble carbodiimide (WSC) based upon the proliferation of chondrocytes on the crosslinked gelatin. WSC was found to be the most suitable crosslinker. Complex scaffolds made from chitosan and gelatin with a component ratio equal to one possessed the proper degradation rate and mechanical stability in vitro. Chondrocytes were able to proliferate well and secrete abundant extracellular matrix in the chitosan-gelatin (1:1) complex scaffolds crosslinked by WSC (C1G1WSC) compared to the non-crosslinked scaffolds. Implantation of chondrocytes-seeded scaffolds in the defects of rabbit articular cartilage confirmed that C1G1WSC promoted the cartilage regeneration. The neotissue formed the histological feature of tide line and lacunae in 6.5 months. The amount of glycosaminoglycans in C1G1WSC constructs (0.187±0.095 µg/mg tissue) harvested from the animals after 6.5 months was 14 wt.% of that in normal cartilage (1.329±0.660 µg/mg tissue). The average compressive modulus of regenerated tissue at 6.5 months was about 0.539 MPa, which approached to that of normal cartilage (0.735 MPa), while that in the blank control (3.881 MPa) was much higher and typical for fibrous tissue. Type II collagen expression in C1G1WSC constructs was similarly intense as that in the normal hyaline cartilage. According to the above results, the use of C1G1WSC scaffolds may enhance the cartilage regeneration in vitro and in vivo.

Bioengineered periosteal progenitor cell sheets to enhance tendon-bone healing in a bone tunnel.

BACKGROUND: Tendon-bone tunnel healing is crucial for long term success in anterior cruciate ligament (ACL) reconstruction. The periosteum contains osteochondral progenitor cells that can differentiate into osteoblasts and chondroblasts during tendon-bone healing. We developed a scaffold-free method using polymerized fibrin-coated dishes to make functional periosteal progenitor cell (PPC) sheets. Bioengineered PPC sheets for enhancing tendon-bone healing were evaluated in an extra-articular bone tunnel model in rabbit. METHODS: PPC derived from rabbit tibia periosteum, cultivated on polymerized fibrin-coated dishes and harvested as PPC sheet. A confocal microscopy assay was used to evaluate the morphology of PPC sheets. PPC sheets as a periosteum to wrap around hamstring tendon grafts were pulled into a 3-mm diameter bone tunnel of tibia, and compared with a tendon graft without PPC sheets treatment. Rabbits were sacrificed at 4 and 8 weeks postoperatively for biochemical as-say and histological assay to demonstrate the enhancement of PPC sheets in tendon-bone healing. RESULTS: PPC spread deposit on fibrin on the dish surface with continuous monolayer PPC was ob-served. Histological staining revealed that PPC sheets enhance collagen and glycosaminoglycans deposition with fibrocartilage formation in the tendon-bone junction at 4 weeks. Collagen fiber with fibrocartilage formation at tendon-bone junction was also found at 8 weeks. Matured fibrocartilage and dense collagen fiber were formed at the tendon-bone interface at 8 weeks by Masson trichrome and Safranin-O staining. CONCLUSIONS: Periosteal progenitor cell monolayer maintains the differentiated capacity and osteochondral potential in order to promote fibrocartilage formation in tendon-bone junction. Bioengineered PPC sheets can offer a new feasible therapeutic strategy of a novel approach to enhance tendon-bone junction healing.

Intraoperative use of somatosensory-evoked potential in monitoring nerve roots.

Different intraoperative neuromonitoring modalities (mixed-nerve somatosensory-evoked potential [M-SSEP], dermatomal somatosensory-evoked potential [D-SSEP], compound motor-evoked potential [CMEP], electromyography [EMG], and the Hoffmann reflex [H-reflex]) have been developed for early detection of nerve root injury, for timely revision, and for damage reduction. In this study, we discuss the advantages and disadvantages of M-SSEP and D-SSEP by reviewing experimental evidence from animal models and clinical practice.

Anti-arthritic effects of magnolol in human interleukin 1ß-stimulated fibroblast-like synoviocytes and in a rat arthritis model.

Fibroblast-like synoviocytes (FLS) play an important role in the pathologic processes of destructive arthritis by producing a number of catabolic cytokines and metalloproteinases (MMPs). The expression of these mediators is controlled at the transcriptional level. The purposes of this study were to evaluate the anti-arthritic effects of magnolol (5,5'-Diallyl-biphenyl-2,2'-diol), the major bioactive component of the bark of Magnolia officinalis, by examining its inhibitory effects on inflammatory mediator secretion and the NF-κB and AP-1 activation pathways and to investigate its therapeutic effects on the development of arthritis in a rat model. The in vitro anti-arthritic activity of magnolol was tested on interleukin (IL)-1ß-stimulated FLS by measuring levels of IL-6, cyclooxygenase-2, prostaglandin E(2), and matrix metalloproteinases (MMPs) by ELISA and RT-PCR. Further studies on how magnolol inhibits IL-1ß-stimulated cytokine expression were performed using Western blots, reporter gene assay, electrophoretic mobility shift assay, and confocal microscope analysis. The in vivo anti-arthritic effects of magnolol were evaluated in a Mycobacterium butyricum-induced arthritis model in rats. Magnolol markedly inhibited IL-1ß (10 ng/mL)-induced cytokine expression in a concentration-dependent manner (2.5-25 µg/mL). In clarifying the mechanisms involved, magnolol was found to inhibit the IL-1ß-induced activation of the IKK/IκB/NF-κB and MAPKs pathways by suppressing the nuclear translocation and DNA binding activity of both transcription factors. In the animal model, magnolol (100 mg/kg) significantly inhibited paw swelling and reduced serum cytokine levels. Our results demonstrate that magnolol inhibits the development of arthritis, suggesting that it might provide a new therapeutic approach to inflammatory arthritis diseases.

Delayed granulocyte colony-stimulating factor treatment promotes functional recovery in rats with severe contusive spinal cord injury.

STUDY DESIGN: We used a severe contusive spinal cord injury (SCI) model and electrophysiologic, motor functional, immunohistochemical, and electron microscopic examinations to analyze the neuroprotective effects of delayed granulocyte colony-stimulating factor (G-CSF) treatment. OBJECTIVE: To determine the neuroprotective effects of delayed G-CSF treatment using multimodality evaluations after severe contusive SCI in rats. SUMMARY OF BACKGROUND DATA: Despite some reports that G-CSF treatment in the acute stage of different central nervous system injury models was neuroprotective, it has not been determined whether delayed G-CSF treatment can promote neural recovery in severe contusive SCI. METHODS: Rats with severe contusive SCI were divided into 2 groups: G-CSF group rats were given serial subcutaneous injections of G-CSF, and control group rats (controls) were given only saline injections on postcontusion days 9 to 13. Using the Basso-Beattie-Bresnahan scale and cortical somatosensory evoked potentials, we recorded functional evaluations weekly. The spinal cords were harvested for protein and immunohistochemical analysis, and for electron microscopy examination. RESULTS: The preserved spinal cord area was larger in G-CSF group rats than in control group rats. Both sensory and motor functions improved after G-CSF treatment. Detachment and disruption of the myelin sheets in the myelinated axons were significantly decreased, and axons sprouted and regenerated. There were fewer microglia and macrophages in the G-CSF group than in the control group. The levels of brain-derived neurotrophic factor were comparable between the 2 groups. CONCLUSION: Delayed G-CSF treatment at the subacute stage of severe contusive SCI promoted spinal cord preservation and improved functional outcomes. The mechanism of G-CSF's protection may be related in part to attenuating the infiltration of microglia and macrophages.