Theoretical Analysis of Bone Tissue Engineering Strategies Using Autologous Stem Cells and Bioscaffolds for Critical-Size Defect Repair in Nigerian Veterinary Clinical Models

Critical-size bone defects resulting from trauma, tumor resection, and osteomyelitis represent a major reconstructive challenge in veterinary surgical practice, and conventional autograft and allograft approaches are limited by donor site morbidity and availability constraints in Nigerian clinical settings. This doctoral study develops a theoretical framework and conducts preliminary experimental evaluation of autologous mesenchymal stem cell-seeded hydroxyapatite-collagen composite bioscaffolds for critical-size bone defect repair using an ovine model at the University of Ibadan veterinary research facility, South West Nigeria, between 2021 and 2024. Ovine mesenchymal stem cells were isolated from bone marrow aspirates, culture-expanded, characterized by flow cytometry, and assessed for osteogenic differentiation capacity. A 25 mm critical-size defect was created in the tibia of 24 sheep assigned to four treatment groups. Histomorphometric, micro-computed tomographic, and mechanical strength assessments were performed at 8 and 16 weeks. Scaffolds seeded with osteogenically induced mesenchymal stem cells achieved the highest bone defect fill percentage at 16 weeks at 73% compared to 41% in scaffold-alone controls. New bone formation with organized lamellar architecture was confirmed histologically in stem cell-seeded groups. Vascular invasion was significantly greater in stem cell-seeded constructs. This study provides the first theoretical and empirical foundation for autologous stem cell-based bone tissue engineering in a large animal Nigerian veterinary model, advancing the field toward clinically translatable reconstructive orthopedic applications. Keywords: bone tissue engineering, mesenchymal stem cells, bioscaffold, critical-size defect, regenerative surgery.