Stem cell research and clinical development in tendon repair.

Stem cells are one of the most fascinating areas in regenerative medicine today. They play a crucial role in development and regeneration and are defined as cells that continuously reproduce themselves while maintaining the ability to differentiate into various cell types. Stem cells are found at all developmental stages, from embryonic stem cells (ESCs) which differentiate into all cell types, to adult stem cells (ASCs) which are responsible for tissue regeneration. Studies using animal models have shown promising results following cell therapy for induced injury in musculoskeletal system, including tendon healing, but the results can be variable. Alternative sources for cell therapy in tendon pathology may include ESCs, ASCs (bone marrow, adipose tissue or tendon derived stem cells) or induced pluripotent stem cells (iPSCs). While ethical and safety concerns currently forbid clinical application of ESCs and iPSCs, initial clinical trials with ASCs are promising.