Biology Forums - Study Force

It is my understanding that stem cells are kept in just about every tissue type in case repair work needs to be done. And yet with age our supply decreases. If we could create stem cells either inside the body or outside then inject into the body what decides if it will try to form specific tissue right away versus stow away until it is needed in the future?

Certainly you'd need to inject them at a specific site, it wouldn't just randomly be injected into one's arm. Thus, stem cells injected into a specific organ, for example, would take the lead of the already differentiated cells there through the interaction of cell receptors (assuming).

But what about stem cells that are stored that aren't prompted yet to become anything? That must be signaled to change type? Like I think adult stem cells divide so that one copy specializes while the other copy goes back into storage for later?

From when I was in university, we learned that even adult stem cells aren't a blank slate like embryonic stem cells are, where they can be converted into any cell type. Thus, embryonic cells are pluripotent, while adult stem cells are only multipotent. That is, there is still a degree of differentiation, and that's why they have a more limited ability to give rise to various cells of the body.

However, emerging evidence which is still very new suggests that adult stem cells may be able to create various types of cells. For instance, bone marrow stem cells or adipose-derived stem cells in adults may be able to create bone or heart muscle cells; I'm not sure the details of how this is done, but relating back to your other thread, it may have to do with methylation being "washed away" by injecting them with specified transcription factors.