Biomedical Engineering Reference
In-Depth Information
silicone tube turns out to be not only a device for containment but also a marginal
reactant which induces a modest amount of regeneration as well (Fields and Ellis-
man 1986a, b). When the silicone tube is replaced by a porous collagen tube with
specific structure, a large additional increase in regenerative activity takes place
(Chamberlain et al. 1998b). These results clearly suggest that the device chosen for
containment must be carefully controlled in each case for its own potential activity
as a reactant for inducing regeneration.
3.7
The Anatomically Well-Defined Defect
We summarize the discussion in this chapter by describing the appropriate experi-
mental volume for study of regeneration. We recommend a fresh wound generated
by mechanical excision of tissue, free of nonregenerative tissue but including the
wound exudate, large enough to include reagents and contain products, and located
in an anatomically well-bounded site inside the reference organ.
Systematic use of all criteria described above leads to description of an anatomi-
cally well-defined wound, suitable for study of induced regeneration in the adult.
A suitable wound in the study of skin regeneration is the dermis-free defect (full-
thickness excisional skin wound; Fig.
3.1
, bottom right); in the peripheral nerve,
it is the completely transected nerve trunk (Fig.
3.2
, middle). Although they have
several uses in a clinical setting, neither the incised or partial-thickness skin wound
nor the hemisectioned nerve trunk are appropriate wounds for such an experimental
study; they will not be discussed further.
Use of the term “defect” instead of “wound” will indicate an anatomically well-
defined wound. In later chapters, data from the literature on induced regeneration of
skin (Chap. 5) and peripheral nerves (Chap. 6) are selected using this criterion. Such
a selection of studies in the literature has the effect of sparing the reader from the
need to understand and factor the effect of differences in anatomical details among
experimental wounds used by various investigators; instead, the reader's attention
can hopefully be focused almost entirely on the reactants used and the outcome
obtained.
3.8
Widely Used Animal Models for Studies of Regeneration
We identified earlier the dermis-free wound and the fully transected nerve trunk as
appropriate defects for study of induced regeneration. We now describe the most
frequently used animal models for study of these defects.
Studies of skin wounds have focused on rectangular full-thickness skin defects
in rodents ever since the pioneering studies of wound healing in animals (Carrel and
Hartmann 1916). Later studies established the standards for studies of skin wound
healing (Billingham and Medawar 1951, 1955). Other authors, especially since the
1970s, have favored the swine (porcine) model over rodent models as being more
similar to the human in skin anatomy and wound-healing behavior (Hartwell 1955;
