Bones regeneration with adult stem cells: Animal model

Objectives: Stem cells have widely shown to be able to calcificate both in vitro and in vivo when implanted under the skin and if conveniently differentiated. However nowadays, in scientific literature a study on their efficiency in the osseous regeneration does not exist yet, thus this aspect was investigated in this work. Materials and methods: 10 White Rabbit New Zealand were submitted to a first surgical procedure, which consisted in a sampling of interscapular adipose tissue, from which some adult stem cells were isolated, expanded and differentiated towards the osteogenic line. In a second surgical procedure 5 different defects on esch animal’s calvarium were created, which had a 0.6cm diameter and were 0.2cm deep (this measures were measured by an appropriate caliper). 4 defects were regenerated using 2 different custom-made scaffolds produced by Geistlich®, with and without the aid of stem cells. After the insertion, the site was covered with a collagen membrane fixed by 5 modified titan pins. The defect in the front was left empty on purpose as an internal control for each animal. These animals were sacrificed in pairs, respectively after 2, 4, 6, 8, 10 weeks. The samples were analyzed by MicroCT analysis using a synchrotron light, through the attainment of 1200 slices for each sample. Once slices were binarizated through an Otsu algorithm, stereologic parameters were calculated and, after that, each sample was submitted to histologic analysis. Results: Histological analysis: Regeneration occurred in an optimal way in each sample treated with scaffolds. The use of adult stem cells combined with scaffolds, seemed to accelerate some steps of the normal osseous regeneration: in fact we assisted to a precocious new deposition and calcification of the extra-cellular matrix and to a colonisation of the osteocyte-lacking areas present in the bovine bone. Only the non-regenerated defect showed a deficit in the calcification of the sample up to the 10th week. MicroCT analysis: A similar behaviour for all the analyzed samples was observed: the quantity of new bone (higher gray levels) showed a tendency to increase with the age of the animals. When comparing the histograms obtained for both Bioss and Bioss with stem cells, the quantity of new bone for the Bioss+stem cells samples was higher than for the Bioss alone ones, when age was considered. The same conclusion was obtained by the histological analysis. Conclusions: Further studies on this subject will individuate the best biomaterial to sustain the potential shown by these cells and will quantify their effective contribution to regeneration.