Tissue engineering is a new and exciting technique which has the potential to create tissues and organs de novo. It involves the in vitro seeding and attachment of human cells onto a scaffold. These cells then proliferate, migrate and differentiate into the specific tissue while secreting the extracellular matrix components required to create the tissue. It is evident, therefore, that the choice of scaffold is crucial to enable the cells to behave in the required manner to produce tissues and organs of the desired shape and size. Current scaffolds, made by conventional scaffold fabrication techniques, are generally foams of synthetic polymers. The cells do not necessarily recognise such surfaces, and most importantly cells cannot migrate more than 500µm from the surface. The lack of oxygen and nutrient supply governs this depth. Solid freeform fabrication (SFF) uses layer-manufacturing strategies to create physical objects directly from computer-generated models. It can improve current scaffold design by controlling scaffold parameters such as pore size, porosity and pore distribution, as well as incorporating an artificial vascular system, thereby increasing the mass transport of oxygen and nutrients into the interior of the scaffold and supporting cellular growth in that region. Several SFF systems have produced tissue-engineering scaffolds with this concept in mind, which will be the main focus of this review. We are developing scaffolds from collagen and with an internal vascular architecture using SFF. Collagen has major advantages as it provides a favourable surface for cellular attachment. The vascular system allows for the supply of nutrients and oxygen throughout the scaffold. The future of tissue engineering scaffolds is intertwined with SFF technologies.

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Making tissue engineering scaffolds work. Review: the application of solid freeform fabrication technology to the production of tissue engineering scaffolds.

Osteoinduction of bone grafting materials for bone repair and regeneration.

Novel collagen scaffolds with predefined internal morphology made by solid freeform fabrication

Recurrent Aphthous Stomatitis

Metal oxides based electrochemical pH sensors: Current progress and future perspectives

The objective of this study was to address the hypothesis that changes in extracellular pH alter collagen gene expression, collagen synthesis, and alkaline phospha- tase activity in bone marrow stromal cells (BMSCs). Poten- tial effects of pH on cell function are of particular impor- tance for tissue engineering because considerable effort is being placed on engineering biodegradable polymers that may generate a local acidic microenvironment on degrada- tion. Human and murine single-cell marrow suspensions were plated at a density o f2×1 0 4 cells/cm 2 . After 7 days in culture, the pH of the culture medium was adjusted to one of six ranges: 7.8, 7.5.-7.7, 7.2-7.4, 6.9-7.1, 6.6-6.8, or 6.5. After 48 h of exposure to an altered pH, alkaline phospha- tase activity and collagen synthesis decreased significantly with decreasing pH. This decrease was two-to threefold as pH decreased from 7.5 to 6.6. In contrast, 1(I) procollagen mRNA levels increased two- to threefold as pH was de- creased. The trend in osteocalcin mRNA expression was op- posite to that of collagen. Small shifts in extracellular pH led to significant changes in the ability of BMSCs to express markers of the osteoblast phenotype. These pH effects po- tentially relate to the microenvironment supplied by a tis- sue-engineering scaffold and suggest that degrading poly- mer scaffolds may influence the biologic activity of the cells in the immediate environment. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res 60: 292-299, 2002; DOI 10.1002/ jbm.10050

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Effects of pH on human bone marrow stromal cells in vitro: Implications for tissue engineering of bone

This article presents an unusual case of major recurrent aphthous stomatitis that was refractory to multiple topical and systemic immunosuppressive therapies. Ultimately, thalidomide was selected despite its well-recognized adverse potential, and was successful in producing remission of ulcers. Strict clinical protocols were followed for this therapy in collaboration with numerous medical providers. This case illustrates the ability of multiple oral health and medical providers to collaborate in the diagnosis, management, and follow-up of a patient with an oral vesiculoerosive disease.

Mojgan Sarmadi

Papers

Effects of pH on human bone marrow stromal cells in vitro: Implications for tissue engineering of bone

Refractory major aphthous stomatitis managed with systemic immunosuppressants: a case report.