Amnion derived stem cell therapy is very popular currently.
Amnion is the inner layer of the placenta which is harvested at the time of C-section. Amnion is derived from the mother, not the newborn child, so it has no ethical considerations.
The amniotic membrane contains numerous growth factors and stem cells which can aid in healing of multiple tissues including cartilage, tendon and ligament, nerve and skin.
It is used in wound healing as well as repairing tendons because it has shown to enhance healing and reduce scarring during the healing process.