Cytocompatibility and biocompatibility of nanostructured carbonated hydroxyapatite spheres for bone repair

ABSTRACT Objective The aim of this study was to investigate the in vitro and in vivo biological responses to nanostructured carbonated hydroxyapatite/calcium alginate (CHA) microspheres used for alveolar bone repair, compared to sintered hydroxyapatite (HA). Material and Methods The maxillary central incisors of 45 Wistar rats were extracted, and the dental sockets were filled with HA, CHA, and blood clot (control group) (n=5/period/group). After 7, 21 and 42 days, the samples of bone with the biomaterials were obtained for histological and histomorphometric analysis, and the plasma levels of RANKL and OPG were determined via immunoassay. Statistical analysis was performed by Two-Way ANOVA with post-hoc Tukey test at 95% level of significance. Results The CHA and HA microspheres were cytocompatible with both human and murine cells on an in vitro assay. Histological analysis showed the time-dependent increase of newly formed bone in control group characterized by an intense osteoblast activity. In HA and CHA groups, the presence of a slight granulation reaction around the spheres was observed after seven days, which was reduced by the 42nd day. A considerable amount of newly formed bone was observed surrounding the CHA spheres and the biomaterials particles at 42-day time point compared with HA. Histomorphometric analysis showed a significant increase of newly formed bone in CHA group compared with HA after 21 and 42 days from surgery, moreover, CHA showed almost 2-fold greater biosorption than HA at 42 days (two-way ANOVA, p<0.05) indicating greater biosorption. An increase in the RANKL/OPG ratio was observed in the CHA group on the 7th day. Conclusion CHA spheres were osteoconductive and presented earlier biosorption, inducing early increases in the levels of proteins involved in resorption.

Are skeletally mature female rats a suitable model to study osteoporosis? / Ratas esqueleticamente maduras são um modelo satisfatório para estudar osteoporose?

OBJECTIVE: To analyze if female Wistar rats at 56 weeks of age are a suitable model to study osteoporosis. MATERIALS AND METHODS: Female rats with 6 and 36 weeks of age (n = 8 per group) were kept over a 20-week period and fed a diet for mature rodents complete in terms of Ca, phosphorous, and vitamin D. Excised femurs were measured for bone mass using dual-energy x-ray absorptiometry, morphometry, and biomechanical properties. The following serum mar-kers of bone metabolism were analyzed: parathyroid hormone (PTH), osteocalcin (OC), osteoprotegerin (OPG), receptor activator of nuclear factor Κappa B ligand (RANKL), C-terminal peptides of type I collagen (CTX-I), total calcium, and alkaline phosphatase (ALP) activity. RESULTS: Rats at 56 weeks of age showed important bone metabolism differences when compared with the younger group, such as, highest diaphysis energy to failure, lowest levels of OC, CTX-I, and ALP, and elevated PTH, even with adequate dietary Ca. CONCLUSION: Rats at 26-week-old rats may be too young to study age-related bone loss, whereas the 56-week-old rats may be good models to represent the early stages of age-related changes in bone metabolism.

OBJETIVO: Avaliar se ratas Wistar com 56 semanas de idade são um modelo satisfatório para estudar osteoporose. MATERIAIS E MÉTODOS: Ratas com 6 e 36 semanas de idade (n = 8 por grupo) foram criadas por um período de 20 semanas e alimentadas com dieta completa em Ca, fósforo e vitamina D para ratas adultas. Os fêmures foram analisados quanto à massa óssea pela técnica de absortiometria por dupla fonte de raios-X, morfometria e propriedades biomecânicas; os marcadores séricos do metabolismo ósseo analisados foram paratormônio (PTH), osteocalcina (OC), osteoprotegerina (OPG), fator receptor ativador nuclear Κappa B ligante (RANKL), peptídeos C-terminal de colágeno tipo I (CTX-I), cálcio total e atividade da fosfatase alcalina (FA). RESULTADOS: As ratas com 56 semanas de vida apresentaram uma importante diferença no metabolismo ósseo quando comparadas ao grupo das ratas jovens, como, por exemplo, maior energia para quebrar a diáfise do fêmur, menores níveis de OC, CTX-I e ALP e maiores níveis de PTH mesmo com dieta adequada em cálcio. CONCLUSÃO: As ratas com 26 semanas de vida podem ser consideradas muito jovens para estudar a perda óssea relacionada à idade, porém, as ratas com 56 semanas de vida podem representar um bom modelo dos estágios iniciais das alterações associadas à idade no metabolismo ósseo.