Vascular and hollow organs

One approach to the tissue engineering of vascular structures is to develop in vitro conditions in order ultimately to fabricate functional vascular tissues before final implantation. The majority of current tissue engineering approaches involves the use of exogenous scaffolds, made of synthetic polymers, protein hydrogels, crosslinked proteins, or decellularized native tissues (Stegemann et al, 2007). Creating a bioreactor that can produce cylindrical vascular grafts could essentially remove manual rolling steps, therefore eliminating the time it takes to produce these grafts and contamination risks. The influence of mechanical stimulation on cell populations not only helps maintain the specific cellular phenotype but also plays a significant role during differentiation and maturation of plastic cells. This is particularly true of tissue-engineered vascular tissue, where in vivo shear forces at the blood interface help maintain the function of the endothelium.

Bioreactors play an important role in tissue engineering, because the fluid flow in bioreactors can enhance nutrient mass transfer and stimulate cell proliferation and matrix secretion. By moving cells between liquid (medium) and gaseous (air) phases, bioreactors for trachea tissue engineering provide an environment for better attachment of implanted cells to the constructs and matrix formation for engineering larger tracheal segments.

The trachea is an ideal model for early clinical translation of bioreactor-based tissue-engineering technology: it is a relatively simple conduit without intrinsic motility and there is a clear clinical need for large airway grafts. Key requirements of a tracheal bioreactor are (a) the provision of different culture conditions on either side of the organwall, and (b) the need for adequate mass transport of gases and nutrients within a construct that has to be more than 4 cm long to be clinically useful.

References:

P Macchiarini, P Jungebluth, T Go, M A Asnaghi, L E Rees, T A Cogan, A Dodson, J Martorell, S Bellini, P P Parnigotto, S C Dickinson, A P Hollander, S Mantero, M T Conconi, M A Birchall. Clinical transplantation of a tissue-engineered airway. Lancet 2008;372(9655):2023–30.

M A Asnaghi, P Jungebluth, M T Raimondi, S C Dickinson, L E Rees, T Go, T A Cogan, A Dodson, P P Parnigotto, A P Hollander, M A Birchall, M T Conconi, P Macchiarini, S Mantero. A double-chamber rotating bioreactor for the development of tissue-engineered hollow organs: From concept to clinical trial. Biomaterials 30 (2009) 5260–5269.

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