  We recently introduced Misrepair-accumulation theory as an interpretation on
aging mechanism. For better understanding this theory, we discuss here in more
details the new concept of Misrepair and the concept of accumulation of
Misrepairs. I. Aging takes place uniquely on the systems that have a
well-defined structure: an organization of its sub-structures. Aging of a
non-living system is a result of accumulation of injuries (damage) of its
structure. II. A generalized concept of Misrepair is important for reaching to
a unified understanding of aging changes. In the situation of a severe injury,
incorrect repair is a repair essential for maintaining structural integrity for
increasing the surviving chance of an organism. With the same mechanism as that
in "Misrepair of DNA" , the term of "Misrepair" can be used for describing all
kinds of incorrect repairs on different types of living structures, including
molecules, cells and tissues. A new concept of Misrepair is therefore proposed
and defined as incorrect reconstruction of an injured living structure.
Misrepair mechanism is beneficial for the survival of an organism, and it is
essential for the survival of a species. III. Alteration of structure made by
Misrepair is irreversible; therefore Misrepairs accumulate and disorganize
gradually a structure, which appears as aging of it. Accumulation of Misrepairs
takes place on molecular, cellular and tissue levels respectively: on tissue
level, it appears as disorganization of cells and extracellular matrixes
(ECMs); on cellular level, it appears as deformation of cytoskeleton and change
of cell shape; and on DNA, it appears as accumulation of DNA mutations and
alteration of DNA sequence. An essential change in aging of an organism is an
irreversible change of the spatial relationship between cells/ECMs in a tissue.
In conclusion, aging of an organism is a result of accumulation of Misrepairs
on tissue level.
