IMPE Abstracts

Osteogenesis imperfecta (OI) is a genetic disease characterized by alterations in type I collagen, which determine a broad spectrum of clinical alterations. Although there is no specific treatment, drugs of the bisphosphonate class are used with the aim of improving bone quality with a reduction in fracture events and a gain in quality of life. In Brazil, current protocols use pamidronate, a second-generation bisphosphonate. The use of zoledronic acid, a third-generation bisphosphonate, has similar safety and effects, with the advantage of reducing hospital stay. The RANK ligand (RANKL) is the main player in osteoclast differentiation, in which IGF-1 also participates through interaction with its specific type 1 receptor (IGF1R). However, there are no studies comparing treatment with bisphosphonates regarding their impact on the IGF system, the RANK ligand and growth determinants. This study aimed to evaluate the mRNA expressions of IGF1R and RANKL, and the serum concentrations of IGF-1 and IGFBP-3 and bone markers, in patients with OI using bisphosphonates and to compare these parameters in groups of patients using pamidronate with those on zoledronic acid. Twenty-one patients diagnosed with OI were studied in a longitudinal model. Participants were randomized into two groups: group A in use of pamidronate and group B in which pamidronate was switched to zoledronic acid. These were followed up longitudinally to assess the influence of pamidronate and zoledronic acid in one and two cycles of medications. When evaluating the influence of a cycle of different medications, there were no significant differences in the variations in the means of the variables between the treatment groups. In the evaluation of two medication cycles, there was a significant difference in the variations of the means of the variables in the analysis of IGF1R, with an increase in expression in the group treated with zoledronic acid. Whereas RANKL expressions, serum concentrations of IGF-1 or IGFBP-3 are normal and similar in both pamidronate and zoledronic acid subjects. In conclusion, the data suggest that there is an increase in IGF1R expression after two cycles of zoledronic acid treatment in children previously treated with pamidronate. However, further studies are needed to assess the impact of this finding.