Biomaterials and bone grafts, with the ability of stimulating tissue growth and bone consolidation, have been emerging as very promising strategies to treat bone fractures. Despite its well-known positive effects of biosilicate (BS) on osteogenesis, its use as bone grafts in critical situations such as bone defects of high dimensions or in non-consolidated fractures may not be sufficient to stimulate tissue repair. Consequently, several approaches have been explored to improve the bioactivity of BS. A promising strategy to reach this aim is the inclusion of an organic part, such as collagen, in order to mimic bone structure. Thus, the present study investigated the biological effects of marine spongin (SPG)-enriched BS composites on the process of healing, using a critical experimental model of cranial bone defect in rats. Histopathological and immunohistochemistry analyzes were performed after two and six weeks of implantation to investigate the effects of the material on bone repair (supplemental material-graphical abstract). Histological analysis demonstrated that for both BS and BS/SPG, similar findings were observed, with signs of material degradation, the presence of granulation tissue along the defect area and newly formed bone into the area of the defect. Additionally, histomorphometry showed that the control group presented higher values for Ob.S/BS (%) and for N.Ob/T.Ar (mm2) (six weeks post-surgery) compared to BS/SPG and higher values of N.Ob/T.Ar (mm2) compared to BS (two weeks post-surgery). Moreover, BS showed higher values for OV/TV (%) compared to BS/SPG (six weeks post-surgery). Also, VEGF immunohistochemistry was increased for BS (two weeks post-surgery) and for BS/SPG (six weeks) compared to CG. TGFb immunostaining was higher for BS compared to CG. The results of this study demonstrated that the BS and BS/SPG scaffolds were biocompatible and able to support bone formation in a critical bone defect in rats. Moreover, an increased VEGF immunostaining was observed in BS/SPG.
This study evaluated the physicochemical and morphological properties of a marine sponge protein extract (PE) using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), analysis of mass loss and pH and in vitro and in vivo. Scanning electron microscopy showed that PE fibers present a granular aspect and irregular structure and the element carbon followed by oxygen was detected in the EDS analysis. Moreover, a 29% of mass loss was observed after 14 days and the pH slightly modified after 14 days. Cell viability of fibroblast cells (L929) of control and PE at a concentration of 25% demonstrated higher values compared to the groups. Osteoblast cell viability of PE at 25 and 50% was significantly higher. Comet assay on day 1 showed higher values for PE at 25%. In addition, in vivo experiments demonstrated that in the treated animals, the bone defects were filled with biomaterial particles, granulation tissue and some areas of newly formed bone. Furthermore, similar immunoexpression of Runx-2 and Cox-2 was observed. Taken together, all results suggest that PE is biocompatible, present non-citotoxicity in the in vitro studies (at the lower concentration) and in the in vivo studies and it can be considered as an alternative source of collagen for tissue engineering proposals.
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