Bone augmentation after ectopic implantation of a cell-free collagen-hydroxyapatite scaffold in the mouse

The bone grafting is the classical way to treat large bone defects. Among the available techniques,autologous bone grafting is still the most used but, however, it can cause complications such asinfection and donor site morbidity. Alternative and innovative methods rely on the development ofbiomaterials mimicking the structure and properties of natural bone. In this study, we characterizeda cell-free scaffold, which was subcutaneously implanted in mice and then analyzed both in vivo andex vivo after 1, 2, 4, 8 and 16 weeks, respectively. Two types of biomaterials, made of either collagenalone or collagen plus magnesium-enriched hydroxyapatite have been used. The results indicate thatbone augmentation and angiogenesis could spontaneously occur into the biomaterial, probably bythe recruitment of host cells, and that the composition of the scaffolds is crucial. In particular, thebiomaterial more closely mimicking the native bone drives the process of bone augmentation moreefficiently. Gene expression analysis and immunohistochemistry demonstrate the expression of typicalmarkers of osteogenesis by the host cells populating the scaffold. Our data suggest that this biomaterialcould represent a promising tool for the reconstruction of large bone defects, without using exogenousliving cells or growth factors.