Growth Plate and Cellular Growth

The growth plate is a highly organized cartilage structure with a complex cellular biology. Studies have been limited by the relative lack of relevant experimental models. Thanks to new technologies, e.g. targeted deletions of genes, knowledge is rapidly expanding. The first paper selected representing the mechanism of the year describes how estradiol can rescue skeletal growth during GH resistance through a novel mechanism of targeted GH receptor-independent stimulation of IGF-I synthesis in the liver. Under new paradigms, we chose a paper showing that the skeletal effects of estrogen are mediated by opposing actions of classical and non-classical estrogen receptor pathways. In addition, two papers were selected to demonstrate contrasting skeletal phenotypes in mice with mutations in thyroid hormone receptoror . The possibility of modulating proteins and genes involved in angiogenesis gives new hope for therapeutic intervention of different growth disorders. Concepts revised or re-centered are represented by three reports focusing on the regulation of growth plate chondrocyte differentiation. Important observation for clinical practice is represented by a report demonstrating that hypophosphatemia may lead to rickets by impairing caspasemediated apoptosis of hypertrophic chondrocytes. Three different papers were selected describing new mechanisms involved in the normal development of the growth plate. The section new genes includes a paper confirming the genetic linkage of human height to two regions, 9q22 and Xq24. The review of the year entitled ‘Fate of the hypertrophic chondrocyte: microenvironmental perspectives on apoptosis and survival in the epiphyseal growth plate’ presents a new concept: hypertrophic cells die through the induction of autophagy. Finally, we selected two papers supplying some food for thought.