Recombinant equine growth hormone administration: effects on synovial fluid biomarkers and cartilage metabolism in horses.

This study sought to understand the effects of administering recombinant equine growth hormone (reGH) on joint metabolism in horses, and it yielded results suggesting that this method might be a good way of delivering IGF-1 to joints for cartilage repair initiatives without causing osteoarthritis.

Study Design and Methods

• In this experiment, six mature horses received daily doses of 20 micrograms/kg bodyweight of reGH via intramuscular injection for a duration of 8 weeks. Three other horses served as controls, receiving injections of sterile water.
• To monitor changes in the levels of growth hormone (GH) and insulin-like growth factor 1 (IGF-1), serum and synovial fluid samples were collected at designated checkpoints; weeks 6, 8, 11, and 16.
• Articular cartilage, crucial for the proper functioning of joints, was harvested at week 16 and was analyzed using Western analysis. This was done to assess its molecular composition, specifically by using monoclonal antibodies BC-13, BC-4, 8-A-4, and CH-3.

Findings

• The study reveals that concentrations of IGF-1 in serum and synovial fluid were significantly higher in the group of horses that received reGH, verified at 6 and 8 weeks into the study. This suggests that the administration of reGH can directly influence the amount of IGF-1 in a horse’s system.
• The concentrations of glycosaminoglycan, a constituent of joint cartilage, were significantly lower in the synovial fluid of reGH treated horses than in those from the control group. This suggests that reGH may have a role in controlling the metabolism of proteoglycans, a class of proteins that includes glycosaminoglycans, in vertebrate cartilage.
• However, the administration of reGH did not result in any noticeable alterations in the fluid content of the 3B3(-) epitope or aggrecan metabolite, nor in the catabolites of aggrecan or link protein within the cartilage. These are changes that might typically associate with the onset of osteoarthritis.

Conclusions

• Overall, the study indicates that the intramuscular delivery of reGH could be a more efficient method of delivering IGF-1 to joints for the purpose of cartilage resurfacing initiatives.
• Importantly, the study found no indications of the development of osteoarthritis due to the administration of reGH, suggesting that this could be a safe method to stimulate cartilage repair in horses.