A new scaffold enriched of mesenchymal stem cells for the treatment of bone defects

Background The repair of large bone defects remains a major clinical orthopedic challenge. The engineering of bone tissue and use of mesenchymal stem cells (MSCs) offer new therapeutic strategies to aid musculoskeletal healing. The delivery of viable stem cells to site of bone defect is an important area of biomedical research. Objectives The aim of this study was to evaluate the regeneration of bone as well as the local tolerance of a new scaffold composed by polycaprolactone-tricalcium phosphate loaded or not with mesenchymal stem cells. Matherials and methods In the first experiment we evaluated the in vivo local tolerance and the ectopic bone formation in mice (nod/scid) implanting the scaffold loaded or non-loaded with stem cells and using hydroxyapatite scaffold as control. Histological evaluation was performed at 8 and 12 weeks from the implantation. In the second experiment we focused on the osteointegration capability of this scaffold enriched or non-enriched autologous stem cells (expanded in bioreactor) in rabbit. The protocol consists of 5 experimental groups of animals (adult New Zealand white rabbit), all with a single implant site per animal. Each leg will be x-rayed in the immediate postoperative time and then every 4 weeks for a total of 4 radiographs for each animal. Histological evaluation was performed at 8 and 12 weeks from the implantation. In the last experiment we evaluated osteointegration and local tolerance of this scaffold enriched or not of autologous stem cells (expanded in vitro in bioreactor) in sheep. The protocol consist of 2 groups of 7 experimental animals each one. Conventional x-ray, micro-CT and histological evaluations were done. Result The scaffold composite by PCL/TCP investigated in this study showed a good behavior in vivo. In fact, none of the samples analyzed in this study induced even a minimal inflammatory reaction in mice, rabbit, and sheep models. Moreover PCL/TCP scaffold showed good vascularization and osteointergration in all specimens when implanted in bone defect. Conclusions In the present study the bioabsorbable PCL/TCP scaffold enriched of MSC shows to promote new bone formation and to be well tolerated by host (no inflammatory reaction was seen). More studies are needed to confirm these results.