Growth factor expression in cartilage wound healing: temporal and spatial immunolocalization in a rabbit auricular cartilage wound model

Objective The ability of cartilage to regenerate following injury is limited, potentially leading to osteoarthritis. Integrative cartilage repair, necessary for durable restoration of cartilage lesions, can be regarded as a wound healing process. Little is known about the effects of growth factors regulating acute cartilage wound healingin vivo . In this study the temporal expression patterns of growth factors and proteoglycan content in cartilage wound edges in vivo were studied. Design Cartilage wounds were created in rabbit ear cartilage using a 6mm biopsy punch. Specimens were subsequently harvested 1, 3, 7, 14 and 28 days after surgery. Paraffin sections were thionin stained to visualize proteoglycan loss and replacement. Immunohistochemical staining of TGFβ1, TGFβ3, IGF-1, IGF-II and FGF-2 was used to define growth factor expression at the cartilage wound sites. Results Almost no effect of cartilage wounding was observed one day after surgery. A decrease of proteoglycan content, with a maximal loss at day 7, and a subsequent restoration was observed at the wound edges. Growth factor expression increased simultaneously. Maximal immunostaining for IGF1, IGFII, FGF2 and TGF-beta3 was observed at day 7, followed by a gradual decrease. Increased expression of TGFβ1 lasted from day 3 until day 14. Conclusion We have demonstrated the ability of chondrocytes to increase growth factor expression and to restore the rapid decrease in proteoglycan content in the initial phase following acute wounding. A temporal increase in intracellular growth factor expression suggests an autocrine and/or paracrine metabolic stimulation, which can be regarded a sign of chondrocytes repair capacity.