126 
Monitoring Stem Cell Research 
pie laboratories around the world.* There is great interest in 
understanding the properties of these cells because they hold 
out the promise of being able to be differentiated into a large 
number of different cell types for possible cell therapies, as 
contrasted with the more limited number of cell types avail- 
able by differentiation of specific adult stem cell preparations. 
As of July 2003, 12 ESC preparations (up from 2 such prepara- 
tions a year earlier) out of a total of 78 “eligible” preparations 
of human ESCs were available for shipment to recipients of 
U.S. federal research grants.^ The review by Ludwig and 
Thomson^ lists more than 40 peer-reviewed human ESC pri- 
mary research papers that have been published since the ini- 
tial publication in 1998. 
Although isolated from different blastocyst-stage human 
embryos in laboratories in different parts of the world, ESCs 
have a number of properties in common. These include the 
presence of common cell surface antigens (recognized by bind- 
ing of specific antibodies), expression of the enzymes alkaline 
phosphatase and telomerase, and production of a common 
gene-regulating transcription factor known as Oct-4. At least 
12 different preparations of ESCs have been expanded by 
growth in vitro, firozen and stored at low temperature, and at 
least partially characterized.^^ Some of these ESC preparations 
have been “single-cell cloned." 
Human ESCs have been differentiated in vitro into neural 
(neurons, astrocytes, and oligodendrocytes), cardiac (synchro- 
nously contracting cardiomvocvtes ). endothelial (blood ves- 
sels), hematopoietic (multiple blood cell lineages), hepatocyte 
(liver cell), and troohoblast (placenta ) lineages.^ In the case of 
neural and cardiac lineages, similar results have been ob- 
tained in different laboratories using different preparations of 
ESCs, thus fulfilling the “reproducible results” criterion de- 
scribed above. For other lineages, the results described have 
not yet been reproduced in another laboratory. 
* According to published reports, laboratories in Australia, Britain, China, 
India, Iran, Israel, Japan, Korea, Singapore, Sweden and the United States 
have isolated ESC preparations. 
^ For current information on available and eligible ESC preparations see: 
http://stemcells.nih.gov/registry/index.asp. 
PRE-PUBLICATION VERSION 
