Stem cells are unspecialized and clonogenic cells that can differentiate
into multiple types of differentiated cells of one or all three
primitive embryonic germ layers (the ectoderm, mesoderm, and
endoderm) in response to appropriate signals depending on their
potency. The observation that stem cells constitute the building blocks
for organ development and tissue repair, has led to animmense growth
of their applications to regenerativemedicine (3). However, before the
anticipated therapeutic potential of stem cells translates into bedside