  Tissue fibrosis is the phenomenon that a tissue has progressive deposition of
collagen fibers with age. Tissue fibrosis is associated with aging of most of
our organs, and it is the main pathology in arteriosclerosis, chronic
bronchitis/emphysema, and benign prostatic hyperplasia. The causes and
characteristics of fibrosis are analyzed with Misrepair mechanism, a mechanism
proposed in Misrepair-accumulation aging theory. Tissue fibrosis is known to be
a result of repairs of tissue by collagen fibers. A repair with collagen fibers
is a manner of "Misrepair". The collagen fibers are used for replacing dead
cells or disrupted extracellular matrixes (ECMs) including elastic fibers,
myofibers, and basement membrane. The progressive tissue fibrosis with age
manifests the essential role of Misrepair in aging, because it reveals three
facts: A. a process of Misrepair exists; B. Misrepairs are unavoidable; and C.
Misrepairs accumulate. As a result of accumulation of Misrepairs of tissue with
collagen fibers, tissue fibrosis is focalized and self-accelerating, appearing
as growing of spots of hyaline degeneration. Fibrosis results in stiffness or
atrophy of an organ and progressive failure of the organ. In arteriosclerosis,
the deposition of collagen fibers in arterial wall is for replacing disrupted
elastic fibers or myofibers, however results in hardness of the wall. Wrinkle
formation is part of skin fibrosis, and it may be a result of accumulation of
collagen fibers of different lengths. Senile hair-loss and hair-whitening are
probably consequence of dermal fibrosis. In conclusion, tissue fibrosis is a
result of accumulation of Misrepairs of tissue with collagen fibers, and the
phenomenon of fibrosis is a powerful proof for the central role of Misrepair in
aging.
