Skeletal Stem Cells - Engineered Bone: Tissue Engineering Intelligence Unit - page 16

Figure 1. Bone formation in 8 week old transplants of SSCs from human bone marrow (A) and guinea pig
blood (B). Human transplant (A) was demineralized, embedded in paraffin and sections were stained with
hematoxylin and eosin; guinea pig transplant (B) was undemineralized, embedded in glycol methacrylate
and sections were stained with Goldner's modified trichrome. Bone (b) is deposited on the surfaces of
hydrohyapatite/tricalcium phosphate ceramic vehicle particles (v) by mature osteoblasts (black arrows). In
undemineralized sections (B), bone (green) can be distinguished from osteoid (red, red arrow). A fully
functional hematopoietic marrow (hp) is formed adjacent to the new bone; it is complete with megakaryo-
cytes (yellow arrows) and adipocytes (a). To view color figure, please go to http://www.eurekah.com/
eurekahlogin.php?chapid=1916&bookid=132&catid=58.
while 12 (35.3%) formed less abundant bone without hematopoiesis. 43 These data demon-
strate that while SSCs are clonogenic, and proliferate extensively, only a subset of CFU-Fs
giving rise to SSCs are multi-potential and have the ability to differentiate along several direc-
tions, including bone and hematopoiesis-supportive stroma with associated adipocytes.
In vivo transplantation assays not only reveal general directions into which a SSC popula-
tion can or cannot differentiate but are a far more sensitive tool able to uncover subtle
differences between differentiation abilities of skeletogenic precursor populations. Upon