TGFB1 and disease of the tendon: Our data provide evidence for mechanisms by which mast cells could contribute to the development of tendinopathy, including a transforming growth factor beta (TGFβ)-dependent upregulation of cyclooxygenase (COX)-2, a reduction of COL1A1 mRNA and type I procollagen protein levels in tenocytes, and a matrix metalloproteinases (MMP)-dependent increase in collagen remodeling activity.