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Monitoring Stem Cell Research 
a degree of reprogramming is likely a protected (stem) cell in vivo, as 
telomere length of MAPC from younger and older donors is similar, 
and significantly longer than what is found in hematopoietic cells 
from the same donor. The fact that MAPC can be isolated from 
multiple tissues might argue that stem cells from each tissue might 
be able to be reprogrammed. However, as was indicated above, the 
studies in which different organs were used as the initiating cell 
population for generation of MAPC did not purify tissue specific cells 
or stem cells. Therefore, an alternative explanation is that the same 
cells isolated from bone marrow that can give rise to MAPC in 
culture might circulate, and be collected from other organs. However, 
we have until now been unsuccessful in isolating MAPC from blood 
or from umbilical cord blood, arguing against this phenomenon. 
Finally, cells selected from the different organs could be the same 
cells resident in multiple organs, such as MSC that are present in 
different locations, or cells associated with tissues present in all 
organs such as for instance blood vessels. Studies are ongoing to 
determine which of these many possibilities is correct. 
CONCLUSION: 
We believe that MAPC would have clinical relevance 
whether they exist in vivo, or are created in vitro. However, 
understanding the nature of the cell will have impact on how one 
would approach their clinical use. If they exist in vivo, it will be 
important to learn where they are located, and to determine whether 
their migration, expansion and differentiation in a tissue specific 
manner can be induced and controlled in vivo. If they are a culture 
creation, understanding the mechanism underlying the 
reprogramming event will be important as that might allow this 
phenomenon to happen on a more routine and controlled basis. 
Either way, a long road lies ahead before MAPC might be 
applicable in clinical trials. Hurdles to be overcome include 
development of robust culture systems that will allow 
automatization. Like of other stem cells, including ES cells, we will 
need to determine in preclinical models whether undifferentiated vs. 
lineage committed vs. terminally differentiated cells should be used 
to treat a variety of disorders. If lineage committed or terminally 
differentiated cells will be needed, robust clinical scale 
differentiation cultures will need to be developed. Furthermore, 
studies will need to be performed to demonstrate whether 
potentially contaminating undifferentiated MAPC will interfere with 
engraftment, and / or differentiate inappropriately in vivo. Likewise, 
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