Biomedical Engineering Reference
In-Depth Information
2
Nonregenerative Tissues
2.1
Certain Tissues in an Organ Regenerate Spontaneously
Experiments in induced tissue or organ regeneration clearly require an appropriate
selection, both of exogenous reactants and of the assays that define the products.
Less obvious, though equally important, is the need to make a rational choice of
the experimental volume for the intended study of regeneration. Criteria for such
choices will be discussed in the present chapter as well as in the next. In this chap-
ter we will discuss a fundamental characteristic of specific tissues that need to be
deleted in order to generate the experimental volume in a study of induced regen-
eration. This characteristic is the intrinsic inability of these tissues to regenerate
spontaneously.
In the preceding chapter we found out that certain types of tissues sustain revers-
ible injury whereas other tissues are injured irreversibly. In this chapter we will
distinguish between the two kinds. Clearly, in studies of induced regeneration, the
investigator seeks to focus on tissues that do not regenerate spontaneously (nonre-
generative tissues). While spontaneously regenerating tissues (regenerative tissues)
can be restored without help from the investigator, nonregenerative tissues must be
induced to regenerate and form the critical objective of such experimental study.
Such tissues must be carefully deleted from the defect; if not, their residual pres-
ence will lead to the erroneous conclusion that regeneration has been induced. On
the other hand, tissues that regenerate spontaneously in the defect are expected to
be present at the end of the healing process irrespective of whether the study has led
to repair or regeneration. The distinction between regenerative and nonregenera-
tive tissues appears to be relatively sharp. It is discussed in detail further using four
well-known experimental paradigms, two each from the literature of wound healing
in skin and peripheral nerves. The literature of induced regeneration for these two
organs is currently richer than for other organs.
