Bone Tissue Engineering Constructs Based on Starch Scaffolds and Bone Marrow Cells Cultured in a Flow Perfusion Bioreactor

The differentiation of human adipose-derived stem cells (hASCs) into osteoblasts is promoted by low amplitude, high frequency vibration treatment

Several studies have demonstrated that tissue culture conditions influence the differentiation of human adipose-derived stem cells (hASCs). Recently, studies performed on SAOS-2 and bone marrow stromal cells (BMSCs) have shown the effectiveness of high frequency vibration treatment on cell differentiation to osteoblasts. The aim of this study was to evaluate the effects of low amplitude, high frequency vibrations on the differentiation of hASCs toward bone tissue. In view of this goal, hASCs were cultured in proliferative or osteogenic media and stimulated daily at 30Hz for 45min for 28days. The state of calcification of the extracellular matrix was determined using the alizarin assay, while the expression of extracellular matrix and associated mRNA was determined by ELISA assays and quantitative RT-PCR (qRT-PCR). The results showed the osteogenic effect of high frequency vibration treatment in the early stages of hASC differentiation (after 14 and 21days). On the contrary, no additional significant differences were observed after 28days cell culture. Transmission Electron Microscopy (TEM) images performed on 21day samples showed evidence of structured collagen fibers in the treated samples. All together, these results demonstrate the effectiveness of high frequency vibration treatment on hASC differentiation toward osteoblasts.

Tubular perfusion system for the long-term dynamic culture of human mesenchymal stem cells

In vitro culture techniques must be improved to increase the feasibility of cell-based tissue engineering strategies. To enhance nutrient transport we have developed a novel bioreactor, the tubular perfusion system (TPS), to culture human mesenchymal stem cells (hMSCs) in three-dimensional scaffolds. This system utilizes an elegant design to create a more effective environment for cell culture. In our design, hMSCs in the TPS bioreactor are encapsulated in alginate beads that are tightly packed in a tubular growth chamber. The medium is perfused by a peristaltic pump through the growth chamber and around the tightly packed scaffolds enhancing nutrient transfer while exposing the cells to shear stress. Results demonstrate that bioreactor culture supports early osteoblastic differentiation of hMSCs as shown by alkaline phosphatase gene expression. After 14 and 28 days of culture significant increases in the gene expression levels of osteocalcin, osteopontin, and bone morphogenetic protein-2 were observed with bioreactor culture, and expression of these markers was shown to increase with media flow rate. These results demonstrate the TPS bioreactor as an effective means to culture hMSCs and provide insight to the effect of long-term shear stresses on differentiating hMSCs.

Effects of low-amplitude, high-frequency vibrations on proliferation and differentiation of SAOS-2 human osteogenic cell line

The aim of the work was to understand the consequences of low-amplitude, high-frequency vibrations on proliferation and differentiation of SAOS-2 cells (sarcoma osteogenetic), an osteoblastic and tumorigenic cell line. We realized a bioreactor composed of an eccentric motor that produces a displacement of 11 mm at frequencies between 1 and 120 Hz on a plate connected to the motor. The cultures of SAOS-2 cells were fixed on the plate, and the linear acceleration provoked by the motor to the cultures was measured. We used 30 Hz as stimulating frequency after a preliminary test on the effect of different frequencies on differentiation of cells. Afterward, SAOS-2 cells were stimulated with 30 Hz for different durations, every day for 4 days. The expression of some genes involved in the differentiation process was analyzed first with a reverse transcriptase-polymerase chain reaction and afterward with a real-time polymerase chain reaction on the most expressed genes. Moreover, the proliferation of cells was evaluated. The results suggest a strong increase in the expression of the genes involved in tissue differentiation in the treated groups with respect to the controls. On the other hand, the proliferation seems to be slowed down, so probably the acceleration perceived by the mechanosensors of the cells changes the cellular cycle by blocking the duplication to early differentiate toward bone tissue.

Fabrication of a RP-Based Biomimetic Grafting Material for Bone Tissue Engineering

Three-dimensional (3D) highly porous poly (DL-lactic-co-glycolic acid)/tricalcium phosphate (PLGA/TCP) scaffolds were fabricated using a rapid prototyping technique (RP). The biopolymer carriers (4mm×4mm×4mm) subsequently were coated with collagen type I (Col) to produce PLGA/TCP/Col composites and utilized as an extracellular matrix for a cell-based strategy of bone tissue engineering. Autologous bone marrow stromal cells (BMSCs) harvested from New Zealand white rabbits were cultured under an osteogenic condition (BMSCs-OB) followed by seeding into the structural highly porous PLGA/TCP/Col composites (i.e. PLGA/TCP/Col/BMSCs-OB). Scanning electron microscopy observation found that the RP-based scaffolds had appropriate microstructure, controlled interconnectivity and high porosity. Modification of the scaffolds with collagen type I (PLGA/TCP/Col) essentially increased the affinity of the carriers to seeding cells, and PLGA/TCP/Col composites were well biocompatible with BMSCs-OB. The PLGA/TCP/Col/BMSCs-OB constructs were then subcutaneously implanted in the back of rabbits compared to controls with autologous BMSCs suspension and carriers alone. As a result, histological new bone formation was observed only in the experimental group with PLGA/TCP/Col/BMSCs-OB constructs 8 weeks after implantation. In the control group with scaffold alone only biodegradation of the carriers was found. Therefore, these results validate our bio-manufacturing methods for a new bone graft substitute.

Natural-origin polymers as carriers and scaffolds for biomolecules and cell delivery in tissue engineering applications

The present paper intends to overview a wide range of natural-origin polymers with special focus on proteins and polysaccharides (the systems more inspired on the extracellular matrix) that are being used in research, or might be potentially useful as carriers systems for active biomolecules or as cell carriers with application in the tissue engineering field targeting several biological tissues. The combination of both applications into a single material has proven to be very challenging though. The paper presents also some examples of commercially available natural-origin polymers with applications in research or in clinical use in several applications. As it is recognized, this class of polymers is being widely used due to their similarities with the extracellular matrix, high chemical versatility, typically good biological performance and inherent cellular interaction and, also very significant, the cell or enzyme-controlled degradability. These biocharacteristics classify the natural-origin polymers as one of the most attractive options to be used in the tissue engineering field and drug delivery applications.

Three dimensional MEMS microfluidic perfusion system for thick brain slice cultures

In vitro tissue culture models are often benchmarked by their ability to replicate in vivo function. One of the limitations of in vitro systems is the difficulty in preserving an orchestrated cell population, especially for generating three-dimensional tissue equivalents. For example, tissue-engineering applications involve large high-density constructs, requiring a perfusing system that is able to apply adequate oxygen and nutrients to the interior region of the tissue. This is particularly true with respect to thick tissue sections harvested for in vitro culture. We have fabricated a microneedle-based perfusion device for high-cell-density in vitro tissue culture from SU-8 photosensitive epoxy and suitable post-processing. The device was tested for its ability to improve viability in slices of harvested brain tissue. This model was chosen due to its acute sensitivity to disruptions in its nutrient supply. Improved viability was visible in the short term as assessed via live-dead discriminating fluorescent staining and confocal microscopy. This perfusion system opens up many possibilities for both neurobiological as well as other culture systems.