Abstract
Demineralized bone matrix (DBM) is widely used for bone regeneration. Since DBM is prepared in powder form its handling properties are not optimal and limit the clinical use of this material. Various synthetic and biological carriers have been used to enhance the DBM handling. In this study we evaluated the effect of gamma irradiation on the physical-chemical properties of Pluronic and on bone morphogenetic proteins (BMPs) amount in DBM samples. In vivo studies were carried out to investigate the effect on bone regeneration of a gamma irradiated DBM-Pluronic F127 (DBM-PF127) composite implanted in the femur of rats. Gamma irradiation effects (25 kGy) on physical-chemical properties of Pluronic F127 were investigated by rheological and infrared analysis. The BMP-2/BMP-7 amount after DBM irradiation was evaluated by ELISA. Bone regeneration capacity of DBM-PF127 containing 40% (w/w) of DBM was investigated in transcortical holes created in the femoral diaphysis of Wistar rat. Bone porosity, repaired bone volume and tissue organization were evaluated at 15, 30 and 90 days by Micro-CT and histological analysis. The results showed that gamma irradiation did not induce significant modification on physical-chemical properties of Pluronic, while a decrease in BMP-2/BMP-7 amount was evidenced in sterilized DBM. Micro-CT and histological evaluation at day 15 post-implantation revealed an interconnected trabeculae network in medullar cavity and cellular infiltration and vascularization of DBM-PF127 residue. In contrast a large rate of not connected trabeculae was observed in Pluronic filled and unfilled defects. At 30 and 90 days the DBM-PF127 samples shown comparable results in term of density and thickness of the new formed tissue respect to unfilled defect. In conclusion a gamma irradiated DBM-PF127 composite, although it may have undergone a significant decrease in the concentration of BMPs, was able to maintains bone regeneration capability.
Highlights
Bone tissue has an excellent ability of regeneration in healthy individuals
The results showed that gamma irradiation did not induce significant modification on physical-chemical properties of Pluronic, while a decrease in bone morphogenetic proteins (BMPs)-2/BMP-7 amount was evidenced in sterilized Demineralized bone matrix (DBM)
No significant change in the sol-gel transition temperature was observed between a 20% (w/v) Pluronic F127 solution gamma irradiated with a dose of 25 kGy and not irradiated samples (Fig 3)
Summary
Bone tissue has an excellent ability of regeneration in healthy individuals. The use of autologous bone graft prevents implant rejection and disease transmission, but its disadvantages such as extensive surgery, limited graft quantity, donor site pain and morbidity has led to the development of graft substitutes for bone healing [1,2]. Excellent substitute requires being porous, osteoinductive, osteoconductive with a resorption rate that allows the bone healing process at the implanted site and a mechanical strength that maintains bone functionality. Demineralized bone matrix (DBM), obtained by removing the mineral component from bone tissue with preservation of proteins content including bone morphogenetic proteins (BMPs), represents a valid alternative to the autograft use [3,4]. Difficulties with handling and its tendency to migrate from graft site, are clinical problems associated with the use of powdered or particulate forms of DBM [5]
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