Introduction: Due to the characteristics of head bones, its injuries often end up being of a critical size which are impossible to close by spontaneous regeneration. Therefore it is necessary to resort to structures made either of poly(methylmethacrylate) or of steel or titanium alloys to seal the cavity. An alternative would be to implement tissue engineering techniques that could achieved a true healing in this type of defects, through bone regeneration, combining strategies such as scaffolding and bone cell culture leading to a three-dimensional scaffold containing elements of the extracellular bone matrix produced by the patient own cells. Materials and Methods: Rigid (melt molding) and flexible (electrospinning technique) scaffolds were made of polylactic acid and chitosan, then osteoblasts in osteogenic medium were seeded and cultured for 15 days, incubation cabin with 5% CO2. Circumferential bilateral 5 mm defects were created on the right and left side of the parietal bone of adult Wistar rats, followed by scaffold implantation on the right side while the left side was left empty, as a control. After three months the samples were recovered and analyzed by histochemical and immunohistochemical techniques as well as scanning electron microscopy. Elemental analysis was performed on both the scaffold bone interface and the surface of the scaffold. In this study, approved by the Universidad del Valle animal ethics committee, we will evaluate the viability of using bioactivated polymer scaffolds in regeneration of critical size defects. Studies of the bone-scaffold interface and the presence of cells and elements of bone extracellular matrix on the implant surface and in the pores of the scaffold will be described. Results and Discussion: It was observed that in the implanted defects the scaffolds were biointegrated to the surrounding bone with the proliferation of numerous cells, fibers and calcium deposits in the interface, in the surface, and in the open pores, (Image 1 - 3). In the control defects only fibers and very little ossification process were observed, Calcium, phosphorus, magnesium, silicon and sulfur were found by the elemental analysis. The hypothesis was tested by the Mann-Whitney method, with a level of statistical significance for type Ⅰ error equal to or less than 0.05. Although the critical size defects are considered difficult or impossible of spontaneous healing by bone regeneration, the samples cultured with osteoblasts were colonized by these cells when the implanted scaffolds contained elements of the extracellular matrix such as collagen fibers and proteoglycans that somehow facilitated cell colonization in vivo and the formation and mineralization of new extracellular matrix. Conclusions: Statistically significant differences between the healing of experimental and control defects were found; scaffold biointegration as well as abundant cell incorporation into their extracellular matrix was observed which are indicative of bone regeneration.
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