Biological Scaffolds for Regenerative Medicine

This chapter evaluates biological scaffold materials in comparison to conventional synthetic scaffold materials, with a focus on intact acellular extracellular matrix (ECM) scaffold materials. Collagens, glycosaminoglycans, chitosans, and other components of the extracellular matrix are used as implantable scaffold materials. Collagen is the most common and abundant naturally occurring scaffold material that can be extracted from various tissues such as tendons, ligaments, and other connective tissues, solubilized, and reconstituted into fibers of various geometries that could, in turn, be transformed into a variety of shapes and sizes to mimic body structures such as heart valves, blood vessels, and skin. Allogeneic and xenogeneic collagen is generally recognized as "self" tissue when used as a biological scaffold material regardless of its species of origin, and it is subjected to the fundamental biological processes of degradation and integration into adjacent host tissues when left in its native ultrastructure. Intact ECM could be isolated from a large variety of different tissues, including heart valves, blood vessels, skin, nerves, skeletal muscle, tendons, ligaments, small intestine, urinary bladder, and liver. These biological scaffolds could be harvested from several different species including tissues from human, porcine, bovine, and equine or from cells grown in vitro. ECM degradation leads to an initial decrease in overall strength during the early phase of in vivo remodeling, followed by an increase in strength due to the deposition of site-specific ECM and the formation of functional site-appropriate neotissue by infiltrating cells in response to their experienced mechanical stresses.