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Tissue engineering has the potential to provide cartilaginous constructs capable of restoring the normal function of native articular cartilage following joint injury or degradation. One approach to functional tissue engineering of cartilage involves the in vitro cultivation of tissue constructs by using: (i) chondrogenic cells that can be selected, expanded, and transfected to overexpress the genes of interest, (ii) scaffolds that provide a defined three-dimensional structure for tissue development and biodegrade at a controlled rate. Understanding the functional potential of the cells and the signaling mechanisms underlying their differentiation should lead to innovative protocols for clinical orthopaedic interventions. A large number of growth factors and hormones have been implicated in the regulation of chondrocyte biology, relatively little is known about the intracellular signaling pathways involved. We have tried to define the roles of specific TGF- dependent signaling pathways involved in the regulation of chondrogenesis from human mesenchymal stem cells. Chondrogenesis induced by TGF-beta3 in alginate bead system was confirmed by examining cartilage specific type II collagen expression and aggrecan, whereas type I collagen expression was not affected by TGF-beta3. Type II collagen mRNA expression was expressed strongly during chondrogenesis and MEK inhibition (U0126) resulted in complete down-regulation of type II collagen. In contrast, aggrecan expression was detected in same level by treatment of U0126. These results strongly suggest that the ERK signaling cascade is involved in TGF-beta3 induced-chondrogenesis signaling pathways and a role of its pathway is necessary over a longer period to promote type II collagen expression. However, their end product properties in vivo have not been well known. In this study, an articular cartilage from chondrogenic MSCs with PLGA scaffolds (75:25 and 65:35) were made and analyzed its biochemical, histological and mechanical properties in vitro and in vivo. And also, we evaluated the cartilage formation in vivo through the injection of cell-thermosensitive gel complex, a newly developed injectable material. At 12 weeks after PLGA scaffolds containing chondrogenic MSCs transplantation, the separated rabbit distal femur showed a good gross articular cartilage appearance in the transplanted site. In indentation test, compare to the native articular cartilage, the engineered cartilage from two types of (75:25 and 65:35) achieved up to 30-60% in mechanical stiffness. And also, a new model for cartilage formation in bladder, at 14 weeks after injection, we could find out mass formation in the submucosal area grossly. H&E staining, alcian blue staining and other special staining confirmed the chondrogenic differentiation in the mass. These cell therapy technologies can provide the possibility of clinical applications for vesicoureteral reflux and reflux esophagitis, and urinary incontinence as well as articular cartilage regeneration.

The purpose of this study is to determine the efficacy of bioactive calcium phosphate obtained from porcine cancellous bone for the treatment of bone defects and nonunion. Porcine cancellous bone blocks were heat treated at 1300 degrees C for 2 h. The chemical composition, calcium-to-phosphate ratio, and microstructure of the porcine bone blocks were examined. For in vivo implantation, bone defects were created on the anteromedial aspect of the proximal tibia in seven beagle dogs and the xenograft bone blocks were placed into these defects. Plain radiographs were taken at 2-week intervals for roentgenographic evaluation. At 12 weeks, the specimens were stained with hematoxylin and eosin (H&E). The composition and morphology of heat-treated porcine cancellous bone were found to be similar to heat-treated human cancellous bone. Radiographs showed union between the host bone/bone-block interfaces. At 12 weeks, uniform and substantial new bone formation was observed. It is concluded that heat-treated porcine cancellous bone demonstrated effective osteoconductivity. This high-temperature heat-treatment technique has several advantages, including decreased risk of disease transmission and immunoreactivity, while also offering excellent biocompatibility.

Chondrogenesis involves the recruitment of mesenchymal cells to differentiate into chondroblasts, and also the cells must synthesize a cartilage-specific extracellular matrix. There were two representative culture systems that promoted the chondrogenic differentiation of human mesenchymal stem cells. These systems were adaptations of the "pellet" culture system, which was originally described as a method for preventing the phenotypic modulation of chondrocytes, and the "alginate bead" culture system, which was used to maintain encapsulated cells at their differentiated phenotype over time, and also it was used to maintain the cells' proteoglycan synthesis at a rate similar to that of primary chondrocytes. We performed test on the differences of phenotypic characterization with the two methods of differentiating human mesenchymal stem cells into chondrocytes. The typical gene for articular cartilage, collagen type II, was more strongly expressed in the "alginate bead" system than in the "pellet" culture system, in addition, specific gene for hypertrophic cartilage, collagen type X, was more rapidly expressed in the "pellet" system than in "alginate bead" culture system. Therefore, the "alginate bead" culture system is a more phenotypical, practical and appropriate system to differentiate human mesenchymal stem cells into articular chondrocytes than the "pellet" culture system.