Repair of critical size bone defects with porous poly [D,L-lactide]/nacre nanocomposite hollow scaffold

To generate a novel porous poly[D,Llactide]/nacre nanocomposite hollow scaffold. This study was performed in the Department of Spine Surgery, Southern Medical University, Guangzhou, China from September 2010 to September 2011. Nacre nanoparticles were prepared using a physical process and identified by x-ray diffraction and transmission electron microscopy, to generate a novel scaffold though the salt leaching processing technique. The morphology and structure properties of this scaffold were further investigated under scanning electron microscope and mechanical property testing. Additionally, the biological characteristics were evaluated by cell culture experiments in vitro. Thirty-six rabbits were randomly divided into 3 groups. The defects were implanted with/without poly[D,L-lactide]/nacre scaffold or poly[D,L-lactide] scaffold. The results were assessed by radiographs and bone mineral density to monitor bone repairing. The nacre nanoparticles were spherical in shape, with a diameter range from 45-95 nm. The scaffolds possessed an interconnected porous structure with an average pore size of 322.5 +/- 50.8 micro m, and exhibited a high porosity [82.5 +/- 0.8%], as well as good compressive strength of 4.5 +/- 0.25 Mpa. Primary biocompatibility experiments in vitro showed that cells adhered and proliferated well on the scaffolds. The animal study further demonstrated that the scaffolds could repair the critical size segmental bone defects in 12 weeks. Newly established scaffolds may serve as a promising biomaterial for bone tissue engineering.

Phenotypic Characterization of Ligamentum Flavum Cells from Patients with Ossification of Ligamentum Flavum

PURPOSE: The objective of this study was to determine the phenotypic characterization of ligamentum flavum cells from patients with ossification of the ligamentum flavum (OLF). MATERIALS AND METHODS: Ligamentum flavum tissues were harvested from OLF and non-OLF patients during surgery. OLF and non-OLF cells were isolated from explant cultures. Cultured cells were analyzed using immunofluorescence staining and reverse transcription-polymerase chain reaction. RESULTS: OLF cells exhibited various appearances compared with the typical fibroblast-like morphology of non-OLF cells. Expressions of collagen type I and collagen type III were observed in OLF and non-OLF cells. OLF cells uniquely expressed osteocalcin, which is a marker for osteoblasts, and collagen type II which is a marker for chondrocytes, whereas they were negative in non-OLF cells. CONCLUSION: These findings indicate that OLF cells have phenotypic characterization of osteoblasts and chondrocytes which could play a role in the pathophysiology of OLF.

Overexpression of transforming growth factor-beta1 in degenerative ligamentum flavum / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the role of transforming growth factor (TGF)-beta1 in degeneration of the ligamentum flavum in the lumbar spine.</p><p><b>METHODS</b>The degenerative ligamentum flavum was obtained during surgery from 8 patients with lumbar spinal stenosis (mean age 58.6 years), and 8 young patients (mean age 24.2 years) with acute lumbar disc herniation were included as normal controls. The thickness of the ligamentum flavum was measured on preoperative magnetic resonance images, and the mRNA expressions of type-I collagen and TGF-beta1 in the ligamentum flavum were detected using reverse transcriptase-polymerase chain reaction. The protein expression and localization of TGF-beta1 were investigated by Western blotting and immunohistochemical staining, respectively.</p><p><b>RESULTS</b>The thickness of the ligamentum flavum were 4.70-/+0.40 mm in the degenerative group and 2.50-/+0.36 mm in the control group, showing significant difference between the two groups (P<0.001). The type-I collagen mRNA expression in the degenerative group was significantly higher than that in the control group (P=0.007). The mRNA and protein expressions of TGF-beta1 were significantly higher in the degenerative group than in the control group (P=0.008 and 0.004, respectively). Immunohistochemistry showed that TGF protein was localized in the fibroblasts within the ligamentum flavum.</p><p><b>CONCLUSION</b>Degenerative ligamentum flavum shows hypertrophy and fibrosis, and TGF-beta1 overexpression may be associated with in the development and progression of ligamentum flavum degeneration in the lumbar spine.</p>

Leptin expression by heterotopic ossification-isolated tissue in rats with Achilles' tenotomy

To set up heterotopic ossification [HO] models according to McClure and determine whether leptin messenger ribonucleic acid [mRNA] and protein are expressed in HO-isolated tissue. This study was performed in the Department of Spine and Orthopedics, Southern Medical University, Guangzhou, China from November 2007 to June 2008. Thirty-six male rats were randomly divided into sham, partial achilles' tenotomy [PAT], and achilles' tenotomy [AT] groups, with 12 rats in each group. X-ray and histological examination were carried out to ensure the formation of HO at 5 and 10 weeks after operation. Specimens from achilles tendons and surrounding tissue were taken and processed. Meanwhile, the expression of leptin mRNA [5 and 10 weeks] and protein [10 weeks] in achilles tendons and the surrounding tissue were examined respectively using reverse transcription-polymerase chain reaction assay and immunohistochemical methods. There were no leptin mRNA and protein expression in the sham and a weak expression in the PAT of Achilles tendons and surrounding tissue, whereas there was strong expression in the AT group. Leptin is involved in the formation of HO, its mechanisms is related to induction of bone formation and maturation through a series of cellular events, including: proliferation/differentiation of many kinds of cells, collagen synthesis, mineralization, and vascularization of the extracellular matrix