Adult stem cells have been suggested to have remarkable plasticity and transdifferentiation ability. This plasticity has raised the hope that adult stem cells could become a universal source of stem cells for tissue/organ repair. MSCs can be isolated from various tissues like bone marrow, gut, lungs, liver, blood, adipose tissue, umbilical cord Wharton jelly, dental pulp, amniotic fluid, and so forth. Mesenchymal stem cells (MSCs) have the ability to form bone, cartilage, adipose tissue, skeletal muscle, cardiac muscle, liver, neuron-like, skin, pancreatic islets, endothelial cells, intestine, renal, epithelial, and germ cells. More importantly, MSCs can be given across allogeneic barrier.

Similarly testicular spermatogonial stem cells (SSCs) have been reported to be the only cells in the body which can be reprogrammed to pluripotent state and grow into ES-like colonies. This knowledge on adult stem cells forms the focus on this special issue.

The main focus of this special issue will be on findings supporting this and also on various possibilities that exist which may explain this remarkable ability of adult stem cells. It is hoped that through this special issue, greater clarity of thought for researchers across the world would emerge. Potential topics include, but are not limited to:

• Pluripotent characteristics of MSCs
• Pluripotent characteristics of SSCs
• Mechanisms underlying transdifferentiation ability of ASCs
• Concept of dedifferentiation and transdifferentiation
• In vitro differentiation of MSCs into three germ layers

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