Análise quantitativa dos níveis de cálcio, Colagenase A e B durante o reparo ósseo em calvárias de ratos sob o modelo experimental de defeito ósseo

Abstract

Bone is a special tissue with a high mineral content and performs various functions in the body, such as calcium reserves, protection of vital structures and muscles lever during the movement. Bone constantly undergoes remodeling processes, which keeps its functional structure and repair small fractures that commonly occur due to the stress of continuous use. The repair system works perfectly synchronized by the cells that produce bone components and resorbing cells, allowing the perfect tissue organization. This maintenance system depends on the interaction between these cells and the signals sent by mediators and modulators. Several proteins operate to induce bone formation, but also to facilitate the reconstruction. Among these proteins are the BMPs, which have great osteoinductive potential, and MMPs that act at different stages of construction and maintenance of this tissue. Particularly BMP-2 has shown significant potential in terms of induction and its recombinant form, rhBMP-2, produced by recombinant engineering, has been released for clinical use and commercialization. In relation to MMPs, there are important functions of MMP-2 and MMP-9 in this tissue. First, structuring the matrix and modulating the resorption during inflammatory processes inherent to repair; second, acting at early to later stages, produced mainly by osteoclasts and used during bone remodeling. However, this repair capacity is limited and large bone defects require a lot of strength of the body, may leading to a bone repair not well structured. Thus, several proposed techniques to stimulate the development and use of bone grafts were effective to provide a framework for growth, facilitating the implementation of new bone and protecting the defect bed throughout the extended recovery period. This study focused on three different types of bone graft (autologous, homologous and heterologous) and their association with rhBMP-2 protein, evaluating the biochemical aspects according to the amount of MMP-2 and MMP-9 in two different periods of time. In general, it was found that firstly, there is an increased production of MMP-2, and MMP-9 levels remain relatively constant in both considered periods of time. The autologous graft presented the best results followed by homologous and heterologous, respectively; however the addition of rhBMP-2 in these grafts did not seem to influence the MMP-2 and MMP-9 levels, in both periods of time. The calcium dosage revealed more mineralization at the autologous and homologous groups, the other groups, besides having lower calcium levels, decreased these levels at the second period of this experiment.