Influence of growth hormone on the mandibular condylar cartilage of rats

Growth hormone (GH) stimulates mandibular growth but its effect on the mandibular condylar cartilage is not well. understood. Objective: This study was designed to understand the influence of GH on mitotic activity and on chondrocytes maturation. The effect of GH on cartilage thickness was also determined. Design: An animal model witt differences in GH status was determined by comparing mutant Lewis dwarf rats with reduced pituitary GH synthesis (dwarf), with normal rats and dwarf animals treated with GH. Six dwarf rats were injected with GH for 6 days, while other six normal rats and six dwarf rats composed other two groups. Mandibular condylar tissues were processed and stained for Herovici's stain and immunohistochemistry, for proliferating cell nuclear antigen (PCNA) and alkaline phosphatase (ALP). Measurements of cartilage thickness as well as the numbers of immunopositive cells for each antibody were analysed by one-way analysis of variance. Results: Cartilage thickness was significantly reduced in the dwarf animals treated with GH. PCNA expression was significant lower in the dwarf rats, but significantly increased when these animals were treated with GH. ALP expression was significant higher in the dwarf animals, while it was significantly reduced in the dwarf animals treated with GH. Conclusions: The results from this study showed that GH stimulates mitotic activity and delays cartilage cells maturation in the mandibular condyte. This effect at the cellular Level may produce changes in the cartilage thickness. (C) 2004 Elsevier Ltd. All rights reserved