Key Engineering Materials Vols. 330-332

Abstract: This study was to determine the ectopic osteogenic ability of BMSCs in combination with a scaffolding material comprising hydroxyapatite and β-tricalcium phosphate matrix (HA/β-TCP). BMSCs were obtained from the SD rats and induced to osteogenesis. Then these induced cells were seeded into HA/β-TCP and the constructs were auto-implanted subcutaneously for up to 12 weeks. Histological analysis, immunostaing, RT-PCR and transmission electron microscopy of the retrieved specimens at various intervals showed obvious trends of ectopic bone formation with obvious alteration of cellular phenotype.

Abstract: The morphology, functions, and gene expression of blood cells and vessels, especially endothelial cells may be modulated by complex hemodynamic forces, as well as by chemical stimulation. Various models have been designed to simulate either the effects of blood flow or the chemical environment on these cells in an effort to understand their response. In this study, a double-layer flow chamber was developed to deliver different flow shear stress and to offer chemical factors, for mimicing the characteristics of both mechanic and chemical stimuli as in vivo conditions. The upper layer of the flow chamber is a main testing chamber (MTC), structured as a quadrate lumen, in which endothelial cells are seeded on the basal plane. The mechanical properties of cells exposed to flow shear stress can be recorded in real-time. The lower layer is a supplementary testing chamber (STC), which provides chemical stimuli. A partition microfiltration membrane exists between the two layers. The flow relationship among variables, such as the velocity, the shear stress, and the pressure distribution of the flowing in the chamber are achieved by using the nondimensional technique and the method of Bessel function of imaginary argument according to Navier-Stokes equations.

Abstract: We hybridized calcium phosphate (CaP) with human semitendinosus and gracilis (ST/G) tendon grafts using an alternate soaking process. To evaluate quantitatively and histologically assess the CaP hybridized human ST/G tendon grafts, we classified them into three groups according to their soaking time – number of soaking cycle: 30 sec – 20 cycles (Group A), 1 min – 15 cycles (Group B), 3 min – 5 cycles (Group C). The tendon grafts were divided into three parts: tibial end (TE), femoral end (FE) and intra-articular (IA) portion. TE was secured using the Krackow technique with No. 2 nonabsorbable sutures, and an Endobutton-CL (Smith & Nephew, USA) was passed through the looped FE, as performed clinically. Then, the IA portion was covered with the sleeve of a rubber glove to prevent CaP hybridization. More soaking cycles induced greater deposition of CaP in the tendon grafts when the total soaking time was the same. Covering the IA portion with a rubber sleeve prevented of CaP deposition. A large amount of CaP in TE was deposited because suture holes increased the total contact area with the solutions.

Abstract: The purpose of this study was to develop a feasible approach for repairing periodontal bone defects with the in vivo tissue engineering bone incorporated with bioabsorbable PLA membrane and to provide evidences for the clinical application. Osteoinductive HA/β-TCP sintered at 1100°C were implanted in the femur medial muscles in the hind legs of three dogs. Four weeks after implantation, the in vivo tissue engineering (TE) bone was explanted. Meanwhile, artificial periodontal bone defects of 8mm×6mm were performed on the buccal side of 4th premolar and 1st molar of mandible bilaterally, with the exposure of dental roots. The defects were treated as follows: (1) in vivo TE bone and PLA membrane; (2) HA/β-TCP ceramics and PLA membrane; (3) PLA membrane only; (4) empty control. At the 2, 4, 8 weeks post-transplantation, the dogs were sacrificed. The specimen were harvested and evaluated by gross inspection, dental radiography, SPECT (99mTC-MDP) and histological observation by MPIA2500. The results showed that more mature osseointegration was found in the group 1. We presumed that the in vivo TE bone graft could enhance the reparation of periodontal bone defects.

Abstract: The purpose of this study is to study the proliferous effect of mandibular condylar chondrocytes given static tension-stress and/or transforming growth factor-β1 (TGF-β1) in vitro. The fourth-passage condylar chondrocytes were harvested for this study, and a pulsatile cellular mechanical system was used to apply stress on cells. The proliferous effect of condylar chondrocytes given continuous static tension-stress and/or TGF-β1 were examined by using flow cytometry. The experiment was divided into two parts. The first part was divided into 20 groups according to different TGF-β1 dosage (0ng/ml, 0.1ng/ml, 1ng/ml and 10ng/ml) for 0, 6, 12, 18 and 24 hours respectively. The second part was divided into eight groups under continuous static tension-stress (0 or 5kPa) and different TGF-β1 dosage (0ng/ml, 0.1ng/ml, 1ng/ml, 10ng/ml) for 12 hours. Experimental data was analyzed with repeated interclass analysis of variance The results showed that chondrocytes which were cultured under different TGF-β1dose combined with 5kPa static tension-stress had multi-horn morphological characters, including a great quantity of chondrocytes with division growth.TGF-β1 had a mitogenic effect on rat mandibular condyle chondrocytes at the concentrations of 0.1 , 1 and 10ng/ml , and the mitogenic effect of TGF-β1 to condylar chondrocytes were demonstrated after 12 to 18 hours, and the peak of mitogenic effects appeared at the 18th hour (P <0.05) . The most active mitogenesis happened in the group whose chondrocytes was under continuous static tension-stress (5kPa) combined with TGF-β1. These results proved that mechanical stimulus and TGF-β1 in vitro could influence and regulate the growth of condylar chondrocytes.

Abstract: Calcium phosphate ceramics are widely used as bone substitutes since they are biocompatible and bioactive. Given that their chemical composition is close to natural bone, calcium phosphate ceramics are promising bone substitute materials in orthopaedics, maxillofacial surgery and dentistry. Hydroxyapatite (HA) and tricalcium phosphate (TCP) are the most commonly used calcium phosphates, because their calcium/phosphorus (Ca/P) ratios are close to that of natural bone and they are relatively stable in physiological environment. Furthermore, other critical parameters must be accomplished when designing a biomaterial for bone regeneration, namely: pore size, shape and interconnectivity [1]. Porosity is one of the most important factors since it influences the adhesion, migration nutrient supply and ultimately, proliferation of mesenchymal stem cells. In this study, HA scaffolds with controlled porosity were obtained and their capacity to support human and rat mesenchymal stem cells attachment and proliferation was evaluated.

Abstract: We have designed a new four-point bending system by combination of integrate circuit and beam-deflection theory, and conducted a series of experiments concerning cell morphology and proliferation. The system was proved to be able to supply the cultured anchorage-dependent cells with cyclic uniaxial stretching strain and compressive stress easily, precisely and effectively.

Abstract: Basic fibroblast growth factor (bFGF) has been shown to maintain the osteogenicity of bone marrow derived mesenchymal stem cell (MSCs) in vitro. This study was to investigate whether bFGF with osteogenic supplements could enhance bone formation of posterior spinal fusion. Rabbit bone marrow derived mesenchymal stem cells were selected by adherence on plastic culture-ware. The MSCs were exposed to dexamethasone with (bFGF group, n=6) or without bFGF (OS group, n=6). Treated cells of two groups were seeded on β-tricalcium phosphate ceramics for one day and then implanted onto L5 and L6 transverse processes of the same animal in posterior spinal fusion without decortication. The ceramics acted as control (n=6). Three fluorochromes were injected sequentially as tetracycline at week 2, xylenol orange at week 4 and calcein at week 6. The spinal segments were harvested at week 7. The bone mineral content (BMC) and volume of transverse processes was measured by peripheral quantitative computed tomography. The specimens were underwent undecalcified histology. The mineralization process was examined by fluorescent microscopy. The BMC of transverse processes in OS group was 16% greater than bFGF and control group significantly. The volume of transverse process in OS and bFGF group was significantly greater than control group by 54% and 46% respectively. The volume of transverse processes in OS group was 6% greater than bFGF group though not statistically significant. In histology, newly formed bone grew from two processes towards each other resulting in a relatively short gap distance in OS and bFGF group while less regenerated bone was observed in the control group. At the mineralization front, calcein which was injected into animal at week 6, was predominately labeled in bFGF group. In OS group, both xylenol orange (at week 4) and calcein labeled were found. In conclusion, mesenchymal stem cells pre-exposed to bFGF were not found to give additional enhancement effect on bone formation in the posterior spinal fusion model.

Abstract: This study focused on in vivo osteogenic capability of bone marrow mesenchymal stem cells (MSCs) seeded on ceramic scaffold. Human MSCs from a single donor were seeded on hydroxyapatite porous ceramic (HAP) and were induced to the osteogenic lineage during in vitro culture condition, then the MSCs/HAP composites were implanted subcutaneously into immunodeficient rats. The cellular activities of the composites were assayed in order to evaluate the distribution and differentiation capability of seeded MSCs before and after implantation. These results showed that the new bone, after implantation, was derived from the donor MSCs, which adhered to the surface of the ceramics pore areas during in vitro culture. Therefore, the engrafted donor cells proliferated and showed continuous osteogenic differentiation within the recipients. Consequently, our study demonstrates the usefulness of MSCs/HAP composites for clinical applications.

Abstract: The cartilage tissue engineering is an inspiring and profitable way for the reconstruction of cartilage defects, but it has been hampered by two large obstacles: how to get qualified seed cells and credible scaffold. This study aimed to evaluate the chondrogenic potential of rat bone marrow stromal cells (BMSCs) by loading them on alginate gel. In this study, the compounds of SD rat BMSCs and alginate gel were injected on the dorsum of rats subcutaneously. The implantations were harvested and examined by histological and immunohistochemical examination, in situ hybridization and transmission electron microscopy at different time points after the operations. The results showed that the compounds of BMSCs and alginate gel are promising for cartilage tissue engineering applications.