No abstract

In this study, a novel freeze-gelation method instead of the conventional freeze-drying method was used to fabricate porous chitosan/collagen-based composite scaffolds for skin-related tissue engineering applications. To improve the performance of chitosan/collagen composite scaffolds, we added 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and amino acids (including alanine, glycine, and glutamic acid) in the fabrication procedure of the composite scaffolds, in which amino acid molecules act as crosslinking bridges to enhance the EDC-mediated crosslinking. This novel combination enhanced the tensile strength of the scaffolds from 0.70 N/g for uncrosslinked scaffolds to 2.2 N/g for crosslinked ones; the crosslinked scaffolds also exhibited slower degradation rates. The hydrophilicity of the scaffolds was also significantly enhanced by the addition of amino acids to the scaffolds. Cell compatibility was demonstrated by the in vitro culture of human skin fibroblasts on the scaffolds. The fibroblasts attached and proliferated well on the chitosan/collagen composite scaffolds, especially the one with glutamic acid molecules as crosslinking bridges, whereas cells did not grow on the chitosan scaffolds. Our results suggest that the collagen-modified chitosan scaffolds with glutamic acid molecules as crosslinking bridges are very promising biomaterials for skin-related tissue engineering applications because of their enhanced tensile strength and improved cell compatibility with skin fibroblasts.

The aims of the present study were to fabricate a novel porous polylactic acid (PLLA) composite scaffold and evaluate the capacity of the scaffold in carrying recombinant bone morphogenetic protein 2 (rhBMP2) for engineering bone formation. The structures of the PLLA scaffolds were evaluated by SEM and the controlled release of rhBMP2 from the composite scaffolds was assayed by ELISA. Bone induction by the scaffolds loaded with or without rhBMP2 was performed in the calf muscle of twenty Wistar rats for 3, 7, 10, 14, and 28 days. Tissue specimens were examined by Masson's trichrome and von Kossa stainings, and immunohistochemistry of bone proteins. Our results indicated that a moderate foreign body reaction was found in control scaffolds, which lasted for 4 weeks. The addition of rhBMP2 to this novel scaffold dramatically alleviated the adverse responses to PLLA. Enhanced deposition of collagen matrix and endochondral formation were observed in rhBMP2-PLLA scaffolds at 7-10 days, compatible with an early release of rhBMP2 in the composite scaffolds. Bone sialoprotein and osteopontin were demonstrated simultaneously. Von Kossa staining was observed in the test group at 10-14 days. In conclusion, the PLLA scaffolds exhibited the capability of carrying rhBMP2 for inducing bone formation within 2 weeks. These results suggest that rhBMP2-PLLA scaffold may be applicable in tissue engineering.

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The incidence of exclusively epidural spinal arteriovenous malformation (EESAVM) is extremely low and there are only a few case-reports in literature. Early, correct recognition of the pathology is mandatory to halt the progression of the disease and minimize permanent spinal cord injury. This review depicts EESAVM's characteristics, from the aspect of pathophysiology, clinical presentation, treatment strategies, and outcome. EESAVMs are located entirely in the epidural space and fed by radicular vessels or segmental arteries. The nidus of EESAVM purely locates in the spinal epidural space. The drainage of nidus flows into the epidural venous plexus or intradural vein. The retrograde blood flow from the AVM results in a diminished intramedullary blood flow and symptoms due to spinal cord ischemia and myelopathy. There is no gender predilection (male 52.9%), age distribution by the time of diagnosis shows most cases are younger than 20-year (64.7%), most cases present as spontaneous epidural hematoma (64.7%), and the majority of those lesions are located on cervicothoracic junction or upper thoracic segment (75%). Generally, the clinical presentation of EESAVM is slighter than intradural/intramedullary AVMs. Unruptured EESAVM may symptomless, or present as protracted, progressive neurological decline. Ruptured EESAVM may present acute back or thoracic pain subsequently with paraplegia. Epidural haemorrhage is common and urgent condition for EESAVM. Up to now, spinal angiography remains the gold standard and the first choice for diagnosis and characterization of spinal vascular lesion. The best management for EESAVM is still surgical operation. Prompt diagnosis and emergency surgical treatment are crucial. Long-term functional prognosis of EESAVM is good, but delayed surgical operation leave residual symptoms.