ABSTRACT
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4. A period of time in a bioreactor culture to stimulate the initial regenerative process 5. Implantation to promote maturation of the tissue, with the ultimate goal of generat-
ing a functional tissue or organ
Of course, there are variations along this theme with many dierent strategies employed depending upon the target tissue for regeneration, the approach taken by the research laboratory, and the nal delivery mode of such therapy in the clinic. For example, the desired cell type (stem, progenitor, or dierentiated) can be directly implanted into an individual and tissue regeneration occurs in the body, as in the approach taken to treat ischemic heart disease (Wu et al. 2011). Alternatively, the cells can be seeded onto a scaold, which could be naturally occurring, for example, decellularized organ tissue (Badylak et al. 2009, 2012; Song and Ott 2011) or synthetic organ tissue (Kim et al. 2011; Williams 2009), and then implanted into the body. A period of construct growth and maturation in a bioreactor prior to implantation also may be required (Asnaghi et al. 2009; Ellis et al. 2005), which could include stimulating cell behavior, for example, by applying mechanical force (Chen and Hu 2006; Gandaglia et al. 2011). Acellular approaches (i.e., implanting a scaold alone to allow host tissue ingress) are also being explored as such materials negate the complex regulatory and logistical issues associated with delivering cells or tissues to the body. Such materials oen include growth factors to encourage and support tissue formation by cells that populate the scaold from the surrounding tissue following implantation (Sarkanen et al. 2012).
