Growth hormone stimulates the growth of mouse neonatal condylar cartilage in vitro.

This study used an organ culture system of neonatal condylar cartilage to study the in vitro effects of recombinant human growth hormone on the growth of cartilage and its inherent cell populations: progenitor cells, chondroblasts and early hypertrophic chondrocytes. Growth hormone at a dose of 2.5 nmol/l enhanced the overall growth of cartilage explant and stimulated the differentiation of its cells. Hence, growth hormone-treated explants revealed a substantial increase in the number of chondroblasts and young hypertrophic chondrocytes. Along with its effects upon cartilage the hormone also stimulated new bone formation adjacent to mineralized hypertrophic chondrocytes. These results provide support to the notion that growth hormone stimulates cartilage growth which in turn is followed by endochondral ossification. In spite of its in vitro effect it is not as yet clear whether the effect of growth hormone is indeed a direct one or is mediated via the local production of IGF-I.