Transforming growth factor-β isoform expression in chronic achilles tendinopathy and their effects on tendon cell populations

The TGF-β family is a group of multifunctional growth factors whose effects on cells and tissues are extremely varied depending on cell and tissue type. The role that specific isoforms of TGF-β play in the wound healing process is of particular interest, the formation of scar tissue having been associated with TGF-β1 and TGF-β2. When tendon heals, there is generally a partial loss of function due to the formation of a scar and adhesion of this scar tissue to the surrounding tendon sheath. TGF-β is known to regulate cellular proliferation, collagen production and metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) synthesis, all of which have been associated with, and are thought to be altered in, the development and progression of tendinitis and tendon healing. The role that each TGF-β isoform plays in the healing process of damaged tendon is still not fully understood. Having recently obtained a source of human tissue from mid-stage, chronic degenerate tendon lesions our aims were to investigate the expression of TGF-β1 and β2 in human tendon and examine the effect of the two isoforms on different human tendon cell populations.