Biomedical Engineering Reference
In-Depth Information
et al. 2010; Song et al. 2010). In contrast, the emphasis in this volume is mostly on
models of
irreversible
injury, i.e., injuries which do not regenerate spontaneously.
Two conditions stand out in such a comparison between amphibians and adult
mammals. The adult mammal offers close access to the clinical goal which fre-
quently focuses on treatment of irreversible injury; the amphibian models of revers-
ible injury are remote from this clinical reality. Furthermore, when working with
the adult mammal, the investigator is rewarded with a rich selection of experimental
conditions for the study of both negative control (repair from irreversible healing)
and its positive counterpart (induced regeneration by reversible healing) in the same
anatomical location of a given species. It follows that study of irreversible injury
in the adult mammal emerges clearly as the basic experimental paradigm for ex-
perimental studies of induced regeneration that also lead most efficiently to clinical
applications.
1.6
Selection Among Mammalian Models of Organ Injury
The lion's share of hard, quantitative evidence for induced regeneration in the
adult mammal is found in studies of skin and peripheral nerve regeneration where
standardized animal models and sophisticated methodology have long been in use.
Selection of skin wounds and peripheral nerve wounds for study of regeneration
has been deliberately made in this volume in order to take advantage of the large
amount of data on healing of these two organs. The available data can then be used
to derive baseline information for use in new developments and in several other
organs. The author is also mostly familiar with studies of skin and peripheral nerve
regeneration based on animal models and clinical applications in these two organs.
Skin wound healing in the adult mammal has been the classical paradigm of
organ repair throughout history (Majno 1982). Skin is the first line of defense of
the organism to exogenous insults; consequently, skin is the organ that is most often
injured, either accidentally, as in a cut or a burn, or intentionally, as part of surgical
operations on the internal organs. Being exposed to direct view, the healing of skin
is also easier to study than is healing of internal organs. Consequently, references to
“wound healing” in the literature usually imply studies of skin wounds, and “scar”
typically refers to scar in skin. Studies of skin wound healing in the mammalian
fetus have likewise fashioned a paradigm for spontaneous organ regeneration (Mast
et al. 1992a; Stocum 1995; Colwell et al. 2005). Because of the wealth of reports in
the literature concerned with skin wound healing (Peacock and Van Winkle 1976;
Clark and Henson 1988; Mast 1992; Clark 1996b; Kim et al. 2009; Cherubino et al.
2011; Hassan et al. 2014), the skin wound healing paradigm forms an invaluable
source of information on the macroscopic as well as molecular biological phenom-
ena that comprise repair and suggest experimental approaches toward regeneration.
Another well-known paradigm of wound healing, studied about as frequently
as skin, is peripheral nerve healing in adult mammals, often following complete
transection (Lundborg 1987; Madison et al. 1992; Valentini 1995; Fu and Gordon
1997; Sanapanich et al. 2002; Dahlin et al. 2007). The data are somewhat more
