Differentiation of mouse embryonic stem cells into dental epithelial-like cells induced by ameloblasts serum-free conditioned medium.

Embryonic stem cells (ESCs) possess an intrinsic self-renewal ability and can differentiate into numerous types of functional tissue cells; however, whether ESCs can differentiate toward the odontogenic lineage is still unknown. In this study, we developed an efficient culture strategy to induce the differentiation of murine ESCs (mESCs) into dental epithelial cells. By culturing mESCs in ameloblasts serum-free conditioned medium (ASF-CM), we could induce their differentiation toward dental epithelial cell lineages; however, similar experiments with the tooth germ cell-conditioned medium (TGC-CM) did not yield effective results. After culturing the cells for 14days in the differentiation-inducing media, the expression of ameloblast-specific proteins such as cytokeratin (CK)14, ameloblastin (AMBN), and amelogenin (AMGN) was markedly higher in mESCs obtained with embryoid body (EB) formation than in mESCs obtained without EB formation. We observed that immunocompromised mice implanted with induced murine EBs (mEBs) showed tissue regenerative capacity and produced odontogenic epithelial-like structures, whereas those implanted with mSCE monolayer cells mainly formed connective tissues. Thus, for the first time, we report that ASF-CM provides a suitable microenvironment for inducing mESC differentiation along the odontogenic epithelial cell lineage. This result has important implications for tooth tissue engineering.

Refining androstenedione and bisnorcholenaldehyde from mother liquor of phytosterol fermentation using macroporous resin column chromatography followed by crystallization.

Androstenedione is an androgen and intermediate in the biosynthesis of most adrenocortical, anabolic, sex and synthetic steroids, such as canrenone, eplerenone, norethindrone and spironolactone. Bisnorcholenaldehyde is an important intermediate in the synthesis of progesterone. This study established an androstenedione and bisnorcholenaldehyde separation method that used a macroporous adsorption resin and an ethanol-water mixture as eluent. The adsorption properties of 12 non-polar or weakly polar macroporous adsorption resins were compared, and three resins exhibited a high adsorption capacity and high desorption rate for both androstenedione and bisnorcholenaldehyde. The three resins were then compared using column chromatography, and one resin was selected and parameters (flow rate, resin size, ethanol concentration and volume) of chromatography were optimized to obtain high purity and recovery. Chromatography eluate was concentrated, dissolved in suitable solvent and crystallized at an optimal temperature to obtain a high purity of both androstenedione and bisnorcholenaldehyde from the same starting material. The levels of androstenedione and bisnorcholenaldehyde in the raw material were 39.78% and 19.15%, respectively. After preparative separation and enrichment by resin column chromatography and crystallization, the purity of androstenedione and bisnorcholenaldehyde was 94.3% and 98.6%, respectively, with their recovery yields of 66.8% and 57.9%, respectively. In addition, the resin maintained over 90% separation efficiency for 5 cycles of adsorption. These results indicated that the combination of macroporous resin chromatography followed by crystallization provide a simple, effective, environmentally friendly and low-cost method for the simultaneous purification of androstenedione and bisnorcholenaldehyde.

Synthesis and cellular biocompatibility of two kinds of HAP with different nanocrystal morphology.

Two kinds of hydroxyapatite (HA) with different nanocrystal morphology were obtained via a simple aqueous precipitation method under different reactants molar ratios. Under Ca/P molar ratio of 1.67/1, rod-like crystal was produced, while under Ca/P molar ratio of 1.80/1, spherical crystal was produced. The spherical crystal was 40-60 nm in diameter, while the rod-like crystal was 40-55 nm in diameter and 79-100 nm in length. The influence of HA nanocrystal morphology on osteoblasts growth was assayed by MTT method and SEM. The results indicated that there was a significantly higher absorbency value on the surface of HA with spherical crystal in MTT assay than the latter. In the process of SEM observation, it is found that osteoblasts spread out a large quantity of nano-filopodias on spherical crystal surface, thus exhibiting much more active cell morphology. In conclusion, HA with spherical nanocrystal showed more favorable properties than that with rod-like one for osteoblasts.

Natural mineralized scaffolds promote the dentinogenic potential of dental pulp stem cells via the mitogen-activated protein kinase signaling pathway.

The selection of a suitable scaffold material is important for dentin tissue regeneration, as the characteristics of biomaterials can potentially influence cell proliferation and differentiation. We compared the effects of different scaffolds on dentin regeneration based on dental pulp stem cells (DPSCs) and investigated the regulatory mechanisms of odontogenic differentiation of DPSCs by these scaffolds. Five different scaffolds were tested: demineralized dentin matrix (DDM), ceramic bovine bone (CBB), small intestinal submucosa (SIS), poly-L-lactate-co-glycolate, and collagen-chondroitin sulfate-hyaluronic acid. DPSCs cultured on DDM and CBB exhibited higher levels of alkaline phosphatase (ALP) activity and mRNA expression of bone sialoprotein, osteocalcin, dentin sialophosphoprotein (DSPP), and dentin matrix protein-1 (DMP-1) than those cultured on the other three scaffolds. Further, the phosphorylation levels of mitogen-activated protein kinase (MAPK) ERK1/2 and p38 in DPSCs cultured on DDM and CBB were also significantly enhanced compared with the other three scaffolds, and their inhibitors significantly inhibited odontogenic differentiation as assessed by ALP activity and mRNA expression of DSPP and DMP-1. The implantation experiment confirmed these results and showed a large amount of regular-shaped dentin-pulp complex tissues, including dentin, predentin, and odontoblasts only in the DDM and CBB groups. The results indicated that natural mineralized scaffolds (DDM and CBB) have potential as attractive scaffolds for dentin tissue-engineering-promoted odontogenic differentiation of DPSCs through the MAPK signaling pathway.

[Orthodontic retention and adjustment of the occlusion after orthognathic surgery].

OBJECTIVE: To investigate the orthodontic retention and adjustment of the occlusion after orthognathic surgery. METHODS: 18 patients were divided into three groups. Group I: Cases with skeletal Class I bimaxillary protrusion treated by subapical osteotomy; Group II: Cases with skeletal Class II mandibular retrusion treated by sagittal split mandibular advancement surgery; Group III: Cases with skeletal Class III treated by Le Fort I osteotomy on maxilla and sagittal split osteotomy on mandible. There were 6 patients in each group. Three kinds of orthodontic elastic tractions were used based on different categories of malocclusion and different types of operation. RESULTS: 18 patients attained functional occlusion after the orthodontic occlusion adjustment. There was no relapse and malocclusion by surgery. CONCLUSION: Intermaxillary elastics based on different categories of occlusion and different kinds of surgery can improve the occlusion after orthognathic surgery and attatin the functional occlusion.

[Stress on class tunnel restorations of the first mandibular molar].

PURPOSE: To study the effect on the stress and deformation of the first mandibular molar when the ridge thickness of Class tunnel restorations changes. METHODS: Six kinds of Class tunnel restorations of the first mandibular molar were prepared,the ridge thickness were 1.5, 2.0 or 2.5 mm, the lateral cavity of the molar was oval or round in shape. The cavities were filled with composite resin. The stresses and deformations were imitated and analyzed by using three-dimensional finite element method with ANSYS 9.0, after vertical and lateral pressures were exerted. RESULTS: Among the 6 restorations, when the ridge thickness of Class tunnel restorations was no less than 2 mm, the stresses were well-distributed, and the directions of stresses on the ridge were the same. There was no difference between round and oval-shaped cavities of Class tunnel in their stress and deformation. CONCLUSION: The ridge thickness of Class tunnel restorations of the mandibular molar is effective and reliable when it's not less than 2 mm.