Avaliação da associação de fibrina rica em plaquetas e enxerto xenógeno na reparo ósseo de defeitos criticos em calvárias de ratos tratados com ácido zoledrônico

Abstract

Bone is a dynamic tissue that presents important self-regenerative capacity, mediated by viable bone cells, adequate vascularity and growth factors. Nevertheless, in cases of congenital malformation, defects due trauma or tumor resection, and extensive craniofacial defects, where this bone capacity it is exceeded, biomaterial are often needed in order to support complete bone repair. Among the most used biomaterials in the clinical practice, Bio-Oss has stood out as a gold-standard bone substitute, despite having only an osteoconductor characteristics. Therefore, in situations where bone metabolism is compromised, as in patients under bisphosphonate therapy, becomes interesting the combination of xenogenous bone graft with biological amplifiers, such as growth factors. In this context, highlights platelet-rich fibrin (PRF), an immunological complex rich in platelets, leukocytes and growth factors embedded in a fibrin scaffold, that in spite of being well-known osteoinductor, still needs studies about its clinical efficacy in tissue regeneration, which led us to investigate the effect of the association between PRF and Bio-Oss on bone repair during bisphosphonate therapy. So, the aim of this work was to evaluate the effect of the association between PRF and Bio-Oss (BO) on bone remodeling in critical size-defect in rat calvaria treated with zoledronic acid (ZA). For this 36 Wistar male rats (Rattus norvegicus), weighing 300 g, were used. Twenty-four rats received previously ZA in single dose of 120 μg/kg, via s.c., similar to an osteoporosis treatment in humans. Seven days later, they were subjected to a surgery to create an 8 mm critical size defect in rat calvaria, and then, were divided into the following groups (n=6 animals/group) according to the treatment: ZA – did not receive bone graft; BO – had the defect filled with 0,04 ml of Bio-Oss; PRF - had the defect filled with 0,04 ml of PRF; BO+PRF - had the defect filled with BO and PRF. The animals of control group (C) (n=6) received saline solution and did not have the defect filled with any graft. All defects were recovered with a collagen membrane before suture. In addition, it was used 6 animals for blood donation in order to obtain the allogenic PRF. After 12 weeks, all animals were euthanized and calvaria was removed and submitted to histological and histomorphometric analyses. Data obtained were analyzed by GraphPad Prisma 8.3 software and were presented as mean±S.E.M using ANOVA followed by Tukey. The animals that received only ZA did not keep the calvaria anatomy, moreover they presented reduction of 34% on osteoblast, 79% on osteoclast, 77% on blood vessel counts and 35% reduction of total collagen, marked by reduction on type I collagen when compared to control (p<0,05). The treatment with Bio-Oss despite keeping the dimensional structure of the tissue, was not able to reverse the deleterious effect of ZA over bone cells and vessels. Meanwhile, the treatment with PRF caused increase of 37% on osteoblast, 72% on osteoclast, 74% on blood vessels counts and 39% of total collagen marked by increase of type I collagen (p<0,05). The association of BO+PRF still, showed better repair aspect, maintaining the tissue architecture. In this group (BO+PRF), BO particles were in smaller size with greater bone formation between these particles, or with fissure particles filled with bone tissue. In this way, we can conclude that the use of PRF associated to Bio-Oss can support the repair process by stimulation of bone remodeling, promoting angiogenesis, stimulating collagen production, keeping tissue anatomy and mitigating the negative effects on bone caused by zoledronic acid, suggesting that this association can be an important tool to the treatment of critical bone defects in patients using bisphosphonates.