Adenovirus encoding BMP-7 immobilized on titanium surface exhibits local delivery ability and regulates osteoblast differentiation in vitro.

OBJECTIVE: The local delivery of growth factors such as bone morphogenetic protein-7 (BMP-7) into the tissues around dental implants may improve their osseointegration. We have designed a new method of attaching BMP-7 to a titanium surface and assessed both the retention of the BMP-7 and its effect on osteoblast differentiation. DESIGN: Adenoviral vector expressing BMP-7 was attached to dental titanium discs by hexon-specific antibodies in a type I collagen-avidin gel. FITC-labelled secondary antibody was used to measure the continuing adherence of the coating after repeated rinsing. Osteoblasts were harvested and seeded on the titanium discs. Gene transduction efficiency and targeting ability were assessed after 24h. Surface morphology was observed by SEM. Cell proliferation and alkaline phosphatase (ALP) activities were measured. RESULTS: The anti-adenohexon antibody adhered strongly to the collagen-avidin gels. BMP-7 gene expression was localized precisely to cells growing on the gels bound by the hexon-specific antibody. Osteoblasts on the titanium containing Ad-BMP-7 had a higher ALP activity than those without Ad-BMP-7. CONCLUSIONS: This study describes a novel technique for the precise attachment of BMP-7 to titanium surfaces. The process may enhance the osseointegration of dental implants.

hRpn13, a newly identified component of the 19S particle, regulates proliferation, differentiation, and function in the human osteoblast-like cell line MG63. [corrected].

The 26S proteasome is a key component of the ubiquitin-proteasome system, a process responsible for the majority of cellular protein degradation. The function of the proteasomal ubiquitin receptor hRpn13, a component of the 26S proteasome, is not completely understood. To investigate the role of hRpn13 in the ubiquitin-proteasome system in osteoblasts, the effects of suppressing and overexpressing the hRpn13 gene on proliferation, differentiation, and function of human osteoblast-like MG63 cells were examined. After knockdown of hRpn13 by small interfering RNA, changes in osteoblast proliferation were evaluated by methyl-thiazolyl-tetrazolium assay. There was an increase in markers for osteoblast proliferation, specifically alkaline phosphatase activity, and elevated protein levels of osteocalcin, proliferating cell nuclear antigen (PCNA), and ubiquitin. Furthermore, hRpn13 knockdown also resulted in a decrease in the ratio between the gene expressions of RANKL and OPG, key players in the pathogenesis of bone diseases that influence the normal balance between bone formation and resorption. In contrast, overexpression of hRpn13 inhibited the proliferation of MG63 cells, and decreased alkaline phosphatase activity as well as protein levels of osteocalcin, PCNA, and ubiquitin while the ratio of RANKL to OPG expression increased. To confirm the function of hRpn13 in the ubiquitin-proteasome pathway, osteoblast proliferation enhancement and ubiquitin accumulation after hRpn2 knockdown was assessed. The results suggest that overexpression of hRpn13 negatively influences proliferation and osteogenic differentiation in MG63 cells. The evidence implies that hRpn13 modulates the influence of osteoblasts on osteoclasts by controlling the stability of regulatory proteins in osteoblasts. In summary, overexpression of hRpn13 promoted the activity of the ubiquitin-proteasome system.

Flavokawain B induces apoptosis of human oral adenoid cystic cancer ACC-2 cells via up-regulation of Bim and down-regulation of Bcl-2 expression.

Novel effective drugs are still urgently needed in the prevention and treatment of oral adenoid cystic carcinoma (ACC). In this study, we have assessed the antitumor potential and molecular mechanisms of flavokawain B (FKB) as a kava chalcone on the ACC-2 cell line in vitro. The results demonstrated that FKB could significantly inhibit the cell proliferation of ACC-2 in a dose-dependent manner that was associated with induced apoptosis and cell cycle G2-M arrest, and the half maximal inhibitory concentration (IC50) of flavokawain-B treatment for 48 h was estimated to be 4.69 ± 0.43 µmol/L. Mechanistically, FKB could induce the release of cytochrome c from mitochondria into the cytosol, and activate the cleavage of caspase-3 and, eventually, the poly(ADP-ribose) polymerase (PARP), in a dose-dependent manner, leading to marked apoptotic effect of ACC-2 cells. The apoptotic action of FKB was associated with the increased expression of proapoptotic proteins: Bim, Bax, Bak and a decreased expression of antiapoptotic Bcl-2. Among them, Bim expression was significantly induced by FKB, and knockdown of Bim expression by short-hairpin RNAs attenuated the inhibitory effect induced by FKB on ACC-2 cells. These results suggest Bim may be one of the potential transcriptional targets, and suggests the potential usefulness of FKB for the prevention and treatment of ACC.

[Osteoblastic early attachment onto the surface of bioadhesive peptide modified pure titanium].

OBJECTIVE: To investigate the long-term integrity and the biological function of interface between the bioadhesive peptide modified implant surface and peri-implant tissue. METHODS: A short bioadhesive peptide containing Glycine-Tyrosine-Arginine-Glycine-Asparticacid-Serine (GYRGDS) sequence was immobilized onto the titanium implant surface by means of sol-gel coating technique and self-assembled monolayers (SAM). The chemical composition and organic functional groups on the titanium surfaces were characterized using XPS (X-ray photoelectron spectroscopy) and FTIR (Fourier transform infrared spectrometer). The adhesive strength and stability of osteoblasts on various implant surfaces were compared under flow condition. RESULTS: The results showed that alkali/hot water aging treatment could apparently improve the content of -OH functional groups of titanium surface. The chemical reactive Ti-O-Ti bonding at the surface of titanium played a vital role in inducing the formation of organosilane SAM. GYRGDS peptide can be covalently grafted onto the surface of titanium by SAM technique. The resistance of freshly adherent osteoblasts to detachment by flow was shear time dependent. When the four groups were compared under the same flow stress condition (2.05 Pa) at three specific time spans (30 min, 1 h, 2 h), the cells retention rates in GYRGDS-grafted groups were 93.0%, 54.4%, 34.4% respectively and were much higher than those in non-coated groups. CONCLUSIONS: It was suggested that GYRGDS might have positive effects on maintaining stability and adherence of cells onto the substrates under flow condition.

[Experimental study on the reconstruction of mandibular defects with sinboneHT bone replacement in rabbits].

OBJECTIVE: After sinboneHT bone replacement (SBR) was implanted in animals, to evaluate the biocompatibility of SBR and compounded in autogenetic bone in the proportion of one to one in order to prepare for the clinical applications in the future. METHODS: Bone defects of 10 mm x l0 mm x 2 mm was made at the mandibular of rabbits, then SBR with different granule diameter and autogenetic bone was compounded in the proportion of being applied in the left defects, while autogenetic bone was implanted in the right defects and nothing was used in the right reformed defects. Animals were sacrificed at 2, 4 and 8 weeks respectively. The biologic capacity was evaluated with anatomy, X-rays studies and histology. RESULTS: SBR has better biocompatibility, which can effectively accelerate the reconstruction of bone defects and help the new bone by being compounded with autogenetic bone. It provides the appropriate scaffold or template which would allow cellular infiltration, attachment and multiplication. CONCLUSION: SBR is a kind of bone substitute material with good biocompatibility. SBR compounded with self-bone has a better regeneration function.

The possible role of estrogen in the incidence of temporomandibular disorders.

Epidemiologic literatures suggest that temporomandibular joint disorders (TMD) are more prevalent in women than in men. It is affecting approximately 7-15% of the adult population in North America, and 80% of patients treated for TMD are women. The severity of symptoms is also related to the age of the patients. The gender and age distribution of TMD suggests a possible link between its pathogenesis and estrogen. It has been reported that estrogen could influence the development, restitution and metabolism of the temporomandibular joint and associated structures such as bone, cartilage and articular disc. Estrogen can also influence the regulative mechanism of pain. In this article, we will use the hypothesis that the overwhelming majority of patients treated for temporomandibular disorders are women and use the available literature to examine the role of estrogens in TMD.

[The effects of desensitizing bonding system for prevention of vital abutment hypersensitivity].

OBJECTIVE: To evaluate the effects of GLUMA desensitizing bonding system in desensitizing hypersensitivity of vital abutment. METHODS: 69 central incisors with vital pulp from 69 patients were randomly divided into A, B and C group. After tooth preparation, group A coated with primer after etching, group B coated with primer after etching cervical dentin only, and group C was control group without special treatment. The cold sensitivity of abutments was tested after coating with primer, after cementation of crown and three months later. Two fresh extracted caries and restoration-free middle incisor were prepared in routine way. The surface of specimen 1 was etched with conditioner and the control specimen 2 was prepared without any special surface treatment. Scanning electron microscope (SEM) observation was used to examine the details on dentin surface. RESULTS: In all three times of examination, the sensitivities of two experimental groups had been significantly reduced compared with the control group. Immediately after coating, group B were more sensitive than group A (P < 0.05). After cementation of crown and three months later, there was no statistically significant between group A and group B. SEM photomicrograph showed that the smear layer was removed from etched dentine surface with open dentinal tubules. CONCLUSION: Coating with GLUMA desensitizing bonding system could prevent hypersensitivity of vital abutment.

[Platelet-rich plasma made by a modified method promotes proliferation of rat osteoblast and human osteoblast in vitro].

OBJECTIVE: To study the effect of serum rich in growth factors (SRGF) derived from platelet-rich plasma (PRP) on the biological function of human and rat osteoblast. METHODS: PRP and platelet-poor plasma (PPP) obtained from healthy human and SD rat were activated by thrombin to get SRGF and serum poor in growth factors (SPGF). The level of TGF-beta1 and PDGF-AB in human-SRGF and SPGF were assayed by enzyme-linked immunoassay (ELISA). Rat and human osteoblast were cultured and identified. Rat osteoblasts were treated with 5% rat-SRGF, 5% rat-SPGF and serum-free F12 medium, respectively. And human osteoblast were treated with 5% human-SRGF, 5% human-SPGF and serum-free DMEM. Cellular mitogenic activity was evaluated by thiazolyl blue (MTT) colorimetric assay at 24, 48, 72 and 96 hours. RESULTS: The level of TGF-beta1 in human-SRGF was 307.67 +/- 35.57 ng/ml, and that of PDGF-AB was 52.76 +/- 7.89 ng/ml. The proliferation of rat and human osteoblast were promoted after treated with rat-SRGF and human-SRGF, respectively. In rat osteoblast groups, there were significant differences in absorbency between rat-SPGF group and rat-SRGF group at 48 and 96 hours (P < 0.05). In human osteoblast groups, the differences between human-SPGF group and human-SRGF group were significant at 48, 72 and 96 hours (P < 0.05). The proliferation of these two kinds of osteoblasts almost stopped in serum-free medium, and the differences in absorbency, compared with other groups, were significant (P < 0.05). CONCLUSION: High quality of PRP can be achieved by the improved method and SRGF is capable of up-regulating the proliferation of rat osteoblast and human osteoblast.

[Relationship between the infiltration arts and penetration depth of molten glass into aluminum oxide matrix].

OBJECTIVE: To explore the influences of infiltration time and temperature on the penetration depth of GI-II glass into alumina matrices, thus providing a theoretical basis for facilitating the clinical fabrication of all-ceramic restorations. METHODS: After preparing cuboid alumina specimens 7 x 7 x 5 mm3 in size, we carried out the infiltration firing procedure at 1100 degrees C for six different time duration (30, 60, 90, 120, 150, 180 minutes), and at five different temperatures (1060, 1080, 1100, 1120, 1140 degrees C) for 1 hour each. The penetration depth of glass into the alumina matrices was measured under a stereoscope with magnification of 10 times. RESULTS: The infiltration time duration and penetration depth were not linearly but exponentially related for both Vita and GI-II materials (r = 0.9886 for Vita and r = 0.9932 for GI-II). The regression equations were as follows: d2 = 0.1122t - 0.4955 (Vita) and d2 = 0.1638t + 0.5873 (GI-II). The temperature and depth were not linearly related either, with increased penetration speed under higher temperatures for GI-II material; the tendency for Vita material was just the opposite. CONCLUSION: At an infiltration temperature of 1100 degrees C, the molten infiltration time duration of GI-II glass could be reduced to 1 hour for copings and 3 hours for anterior bridge substructures due to its better infiltration ability.