Appendix K. 
323 
Muscle contains satellite cells that normally participate in 
replacement of myoblasts and myofibers. There are also indications 
that muscle additionally may harbor other stem cells, either as 
hematopoietic migrants from bone marrow and peripheral blood, or 
as intrinsic stem cells of muscle tissue. Muscle appears to contain a 
side population of stem cells, as seen in bone marrow and liver, with 
the ability to regenerate muscle tissue. Muscle derived stem cells 
have been clonally isolated and used to enhance muscle and bone 
regeneration in animals. An isolated population of muscle-derived 
stem cells has also been sho'wn to participate in muscle regeneration 
in a mouse model of muscular dystrophy. Stimulation of muscle 
regeneration from muscle-derived stem cells, as observed in other 
tissues, is greatly increased after injury of the tissue. An 
interesting use of muscle-derived stem cells has been the 
regeneration and strengthening of bladder in a rat model of 
incontinence.^^® Because of the similar nature of muscle cells 
between skeletal muscle and heart muscle, muscle-derived stem 
cells have also been proposed for use in repairing cardiac damage, 
with evidence that mechanical beating is necessary for full 
differentiation of skeletal muscle stem cells into cardiomyocytes.^®° 
At least one group has used skeletal muscle cells for clinical 
application to repair cardiac damage in a patient, v\hth positive 
results. 
LIVER STEM CELLS 
As noted before, there are similarities between liver and 
pancreas which could facilitate interconversion of cells between the 
two tissues. This concept has been demonstrated using genetic 
engineering to add a pancreatic development gene to hver cells, 
converting hver to pancreas. Rat hver stem cells have been 
converted in vitro into insulin-secreting pancreatic ceUs.^^ When 
transplanted into immundeficient mice which are a model for 
diabetes, the converted hver stem ceUs were able to reverse 
hyperglycemia in the mice. One other interesting observation 
regarding hver stem cells has been the possible formation of 
myocytes in the heart by hver stem cells. A clonal ceU line derived 
from adult male rat hver and geneticahy tagged was injected into 
female rats, and marked, Y-chromosome bearing myocytes were 
identified in the host hearts after six weeks. 
PANCREATIC STEM CELLS 
PRE -PUBLICATION VERSION 
