Técnicas de imagen aplicadas al estudio de la regeneración ósea y del efecto de la deferoxamina en un modelo in vivo de ratas Wistar

Laburpena

Bone regeneration is a research field of increasing interest due to the physical and emotional implications that total or partial bone resection have in patients who suffered traumas, tumors or bone infections. There are indications in the literature that deferoxamine, iron chelator, used in ferric intoxications among others, could have an effect on bone regeneration by activating the HIF-1? pathway. Furthermore, imaging techniques are developing at high pace, enabling more precise and more sensitive ways to study bone regeneration. Computed microtomography (microCT) is a valuable non-invasive method that combines the study of anatomical and functional data at the same time, allowing enhanced characterization and localization of bone lesions. The scanning microscope (SEM-EDX) makes it possible to obtain very detailed images of each bone's defect as well as carry out a microanalysis of the fundamental elements in the bone formation such as calcium, phosphorus and oxygen. OBJECTIVES: This study will be targeting two aspects. On one hand, it will qualitatively assess the suitability of different imaging techniques (photography, X-ray radiography, microCT and EDX) in the study of bone regeneration. On the other hand, it will quantitatively study the effect of DFO as a possible activator in the formation of new bone in critical size defects in a rodent model in vivo. MATERIALS AND METHODS: In this work, Wistar rats were divided into two groups: one that was treated with DFO for three weeks and another one for six weeks. Two defects of 3 mm were made in the calvaria of each rat, one control with a collagen sponge and another with a collagen sponge and DFO. At first, suitability qualitative comparison of photography, X-ray radiography, microCT and SEM-EDX was performed. Subsequently, microCT and SEM-EDX were used to carry out a quantitative analysis of regenerated bone and to assess its quality. Hence, microCT was used for its capacity to provide the percentage of new formed bone as well as the breakdown percentage of every bone type. SEM-EDX was rather used to measure the percentage of oxygen and the Ca/P ratio. RESULTS: Qualitatively, only microCT allowed us to see differences in bone regeneration when comparing defects treated with DFO to control at both 3 weeks and 6 weeks. With all techniques, bone resorption was observed at 6 weeks of treatment. Quantitatively, using microCT, bone growth percentages were higher in defects treated with DFO both at 3 and 6 weeks compared to controls. However, the percentage of bone formed is greater at 3 weeks compared to 6 weeks in DFO defects. Higher quality bone percentage was found in the group treated with DFO at 6 weeks. Using SEM-EDX, we found no differences in the percentage of oxygen between DFO and control groups neither at 3 nor at 6 weeks. However, oxygen percentage was greater at 6 weeks than at 3 weeks. The Ca/P ratio indicated that the quality of the new formed bone formed was getting greater as time goes by. DISCUSSION AND CONCLUSIONS: Although the SEM-EDX allowed us to see smaller structures, only microCT was complete enough for the study of bone regeneration. Other techniques (photography, X-Ray radiography) can be used to complement the assessment provided by microCT and SEM-EDX but can't substitute them. DFO had a positive effect on bone formation at 3 weeks and an inhibitory effect at 6 weeks. However, the quality of the bone formed is greater as time goes by.