Stem Cells

Stem cells are the building blocks of the embryo and they allow the phenomenal gain in size and complexity that accompanies early development. Stem cells are very much dependent on their environment to maintain the stem cell phenotype and easily begin to differentiate into adult cell types when removed from the stem cell niche. Stem cells have the property of plasticity that allows them to respond to different signals in different environments. Some types of stem cells are found in the adult, most often in tissues that constantly regenerate, such as blood and skin and intestinal epithelia. Other tissues that were, until recently, thought not to regenerate have been found to have small numbers of stem or progenitor cells that replace the functional cells slowly, such as bone, heart, and brain. The presence of at least some adult stem cells in all tissues suggests that we must understand their in vivo role and use them to facilitate better and complete tissue regeneration.