Human articular chondrocytes express functional leptin receptors

The effects of leptin hormone are mediated by interactions with several phy siological regulatory systems and the cytokine network, and by targeting ce lls directly. The leptin receptor is a member of the class I cytokine recep tor family, and its signal transduction. resembles that induced by many cyt okines. We demonstrated that serially cultured human articular chondrocytes possess the leptin receptor (Ob-R), and that this receptor was present on chondrocytes in native human cartilage. In cultured chondrocytes we detecte d mRNA for the functional isoform of leptin receptor (Ob-Rb or Ob-R-L), and it was revealed that ligand binding resulted in phosphorylation of signal transducers and activators of transcription, namely STAT1 and STAT5. Chondr ocytes stimulated with leptin exhibited an increased proliferation and an e nhanced synthesis of extracellular matrix (proteoglycans and collagen). The se results indicate that leptin affects cartilage generation directly, whic h is a novel role for leptin in skeletal growth and development. (C) 2001 A cademic Press.