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Monitoring Stem Cell Research 
used in a mouse model of Duchenne muscular dystrophy to test their 
ability to repair damaged muscle. Stem cells injected into the 
bloodstream could engraft and incorporate into muscle, taking on a 
muscle phenotype, and with evidence of muscle repair.^^^ 
HEART 
Beltrami et aJ. analyzed the hearts of post-mortem patients 
who succumbed 4-12 days after heart attack, and found evidence of 
dividing myocytes in the human heart. While it is unclear from the 
study whether the cells were originally cardiomyocytes or were other 
stem cells which had homed to damaged heart tissue, such as bone 
marrow stem cells, the evidence indicated dividing cells v\hthin the 
heart.^“ 
CARTILAGE 
Human cartilage biopsies placed into culture show apparent 
dedifferentiation into primitive chondrocytes with mesenchymal 
stem cell appearance. These chondrocytes have been used for 
transplants to repair articular cartilage damage, and in treatment of 
children with osteogenesis imperfecta. 
THYMIC PROGENITORS 
Bennett et al. have reported the isolation of thymic epithelial 
progenitor cells. Ectopic grafting (under the kidney capsule) of the 
cells into mice allowed production of all thymic epithelial cell types, 
as well as attraction of homing T lymphocytes. In separate 
experiments. Gill et al. also isolated a putative thymic progenitor cell 
from mice and were able to use these cells to reform miniature 
thymuses when the cells were transplanted under mouse kidney 
capsule. 
DENTAL PULP STEM CELLS 
Stem cells have been isolated from human adult dental pulp 
that could be clonally propagated and proliferated rapidly. Though 
there were some similarities with bone marrow mesenchymal stem 
cells, when injected into immunodeficient mice the adult dental pulp 
stem cells formed primarily dentin-like structures surrounded by 
pulpy interstitial tissue. Human baby teeth have also been identified 
as a source of stem cells, designated SHED cells (Stem cells from 
Human Exfoliated Deciduous teeth ). In vitro, SHED cells could 
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