While stem cells are heavily involved in homeostasis, growth and repair of many tissues [34], they may also contribute to some forms of tendinopathy by creating ectopic tissue inside the tendon [35].Our RT-PCR analyses demonstrated that the cells from the peritenon had significantly higher expressions of the following genes: CD45, CD90, CD105, and Oct-4 compared to the cells from the tendon core. This evidence concerns the gene POU5F1 and disease of the tendon.