As the name suggests adult stem cells are found throughout
the adult body occupying their own little environments called stem cell niches.
A stem cell niche is a highly controlled environment that’s designed to stop
stem cells differentiating into other cell types, maintain a population of stem
cells and also allow a response to injury via endogenous signalling. A common
example of a stem cell niche can be found within bone where haematopoietic stem
cells and mesenchymal stem cells (Image) reside. Adult stem cells are far more ethically
acceptable than using human embryonic stem cells but unfortunately are more
limited in their use.
Human embryonic stem cells can differentiate into any body cell
whereas adult stem cells are restricted to a few differentiation pathways each (Multipotent)
depending on the starting stem cell, for example, mesenchymal stem cells have a
tri-lineage differentiation ability where they can give rise to only osteogenic
(bone), chondrogenic (cartilage) and adipogenic (fat) tissues. However the
abilities and identity of mesenchymal stem cells is still a matter of debate
between biomedical scientists.
Adult stem cells are usually autologous (donated and
received by the same individual) so no immune rejection occurs however a major
limitation of adult stem cells is a marked decline in population with age, therefore
as an individual ages less stem cells are available for collection in a
clinical setting. Currently they have been used to treat many diseases with
some success such as the use of mesenchymal stem cells given intravenously to
treat myocardial infarction but their potential is yet to be realised.
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