Tendon Vasculature in Health and Disease

Tendons, unlike highly vascularized tissues, do not necessarily benefit from neovascularization after injury. Instead, increased vascularization is associated with degeneration, as healthy tendons are poorly vascularized. In healthy adult tendons, cells produce the antiangiogenic factor endostatin in response to physiological mechanical load, limiting neo-angiogenesis. Stem/progenitor cells within tendons may contribute to both tendon maintenance and disease by differentiating into various cell types or producing trophic factors.

• 1
  Tendons have a more complex vascular network than previously believed, with vessels entering from musculo-tendineous junctions, bone insertion sites, and the paratenon.
• 2
  The proangiogenic protein vascular endothelial growth factor (VEGF) is highly expressed in fetal and injured tendons, but low in intact adult tendons.
• 3
  Lymphatic vessels play a crucial role in tissue repair and inflammation, but their role in tendon disease has been largely neglected.