Repair of Critical-Sized Rat Calvarial Defects With Three-Dimensional Hydroxyapatite-Gelatin Scaffolds and Bone Marrow Stromal Stem Cells.

Introduction: The repair of critical-sized defects (CSDs) are one of the most challenging orthopedic problems and the attempts for development of an ideal scaffold for treatment of large bone defect are ongoing.

Aim: The aim of this study was the effectiveness of hydroxyapatite-gelatin seeded with bone marrow stromal cells construct for healing of critical-sized bone defect in vivo.

Material and Methods: In this experimental study, the bone marrow stromal cells (BMSCs) were isolated by flushing method. For in vitro study, the cells were seeded on the scaffold and the cell viability as well as cytotoxicity were tested by MTT and LDH specific activity. The scaffold-cell construct was implanted into the critical-sized bone defect created in calvaria of Wistar male rats.15 rats were randomly divided into 3 groups (n=5), group 1 (control group): Injury without transplantation, group 2: implanted with hydroxyapatite-gelatin scaffold, group 3: hydroxyapatite-gelatin scaffold seeded with BMSCs. At different days post-implantation, the implanted site was collected and the bone healing was evaluated through H&E and Masson's Trichrome staining. ANOVA and paired t-test were used for data comparison and P<0.05 was considered significant.

Results: The results of MTT showed that the scaffold has no toxic effects on stromal cells. The first signs of ossification in hydroxyapatite-gelatin with BMSCs cells group appeared in the first week. However, in the fourth week, ossification was completed and the scaffold remaining was found as embedded islands in the spongy bone tissue. The greatest number of lymphocytes in the experimental group was observed after one week of planting scaffold.

Conclusion: Hydroxyapatite-gelatin scaffold coated with BMSCs cells has a potential role in the healing process of bone and would be a possible new therapeutic strategy to repair extensive bone lesions.