Tissue Engineering

Abstract

The concept of tissue engineering (TE) was born when Vacanti and Langer suggested that living cells may form in vitro , at appropriate conditions, structures identical with those they form in live bodies. Tissue engineering is a fast growing branch of biomedical engineering. It currently consists of several branches. Seeding and culturing cells on scaffolds, which imitate extracellular matrix (ECM), is the basis of the most commonly used method. Scaffolds are prepared from various natural and synthetic polymers. Another variant of TE involves injection of gels that form scaffolds in situ . Acellular scaffolds may also be inserted in vivo . They mobilize cells from the adjacent tissues, from circulating body fluids, or stem cell sources. The above mentioned methods eliminate the in vitro stage of TE procedures. Another branch of TE is called cell‐sheet engineering (CSE). It involves culturing cell sheets on a surface of a polymer, whose structure undergoes sudden transition at a certain critical temperature ( T tr ). Cells are cultured at T > T tr . However, when a sheet is formed it separates spontaneously from the supporting surface when the temperature is decreased < T tr . Sheets thus formed can be harvested without damaging cell–cell or cell–ECM interactions. The CSE is particularly suitable for TE of liver and heart, since they consist of cells loosely associated with ECM. Materials used for formation of scaffolds and methods used for their preparation are described in some detail. Techniques, eg, rapid prototyping (RP) and photopattering, are discussed. Inverse RP, as well as the engineering of scaffolds surfaces, is also mentioned. The operation mechanism of various bioreactors for TE and their effect on the properties of the engineered tissues are reviewed.