title: The influence of biomechanical parameters on the expression of VEGF and endostatin in the bone and joint system.
abstract: Many degenerative processes in the skeletal system are induced by mechanical overload. Osteoarthritis and spontaneous tendon ruptures are two examples of mechanically influenced diseases. Incubator-housed compression apparatuses and cyclic strain chambers are adequate models to investigate the cellular processes. Recent studies have shown that growth factors are involved in the transduction pathways of mechanical overload leading to tissue degradation. Vascular endothelial growth factor (VEGF) is a dimerized, 45 kDa peptide that normally attracts endothelial cells in wound healing. VEGF can be detected in the superficial zone of the tibial plateau in osteoarthritic (OA) patients with degenerative changes but not in healthy articular cartilage. Blood vessels are only rarely observed in OA cartilage suggesting that there are other roles for VEGF in cartilage. VEGF is also detectable in ruptured but not in normal tendons. The mechanically induced expression of VEGF in avascular tissues like articular cartilage or fibrocartilage of contact areas from gliding tendons initiates degenerative processes. Chondrocytes from OA cartilage also express the VEGF receptor 2. In vitro assays have shown that VEGF binds the VEGFR-2 leading to a phosphorylation of MAP kinases (ERK1/2) with subsequent transcription factor accumulation (activator protein 1 = AP-1). One of the antagonists of VEGF is endostatin. Endostatin, a fragment of collagen type XVIII, is expressed in avascular tissues and has the potency to decrease VEGF induced effects (ERK1/2 phosphorylation). The increase in matrix metalloproteinase (MMP) production and the decrease in tissue inhibitor metalloproteinase (TIMP) synthesis is a result of the signal transduction cascade activation. MMPs participate in the degradation processes of osteoarthritis whereas TIMPs are inhibitors of the MMPs. Taken together mechanically induced VEGF is involved in the destruction and endostatin in the maintenance of avascular tissues of the bone and joint system.
authors.affiliation: Department of Anatomy, Christian-Albrechts University, Olshausenstrasse 40, 24098 Kiel, Germany. t.pufe@anat.uni-kiel.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Pufe
authors.forename: Bodo
authors.initials: B
authors.lastname: Kurz
authors.forename: Wolf
authors.initials: W
authors.lastname: Petersen
authors.forename: Deike
authors.initials: D
authors.lastname: Varoga
authors.forename: Rolf
authors.initials: R
authors.lastname: Mentlein
authors.forename: Svea
authors.initials: S
authors.lastname: Kulow
authors.forename: Angelika
authors.initials: A
authors.lastname: Lemke
authors.forename: Bernhard
authors.initials: B
authors.lastname: Tillmann
mesh_terms: D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000502:physiology*; D002356:Cartilage / Q000502:physiology*; D019902:Chondrocytes / Q000502:physiology; D043169:Endostatins / Q000378:metabolism*; D006801:Humans; D007596:Joints / Q000502:physiology*; D010003:Osteoarthritis / Q000503:physiopathology; D013710:Tendons / Q000473:pathology / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D014945:Wound Healing
chemical_list: D043169:Endostatins; D042461:Vascular Endothelial Growth Factor A