Evaluation of mesenchymal stem cells’ bone repair capacity via osteogenic lineage differentiation in experimental nonunion fractures

Abstract

Background Nonunion of fractures is a major challenge in orthopedics and traumatology, especially with increasing high-energy injuries. Adipose-derived mesenchymal stem cells (ASCs) are a readily accessible source with strong osteogenic potential. This study compared the bone regenerative efficacy of undifferentiated ASCs versus their osteogenically pre-differentiated derivatives in a critical-size femoral nonunion model. Methods Eighteen male New Zealand White rabbits (n = 18), aged 3 months and weighing 2.94 ± 0.10 kg, were included. MSCs were isolated enzymatically from abdominal adipose tissue of three donor rabbits. At passage 3, cells were cultured either in basal medium (undifferentiated cohort) or osteogenic medium containing β-glycerophosphate, dexamethasone, and ascorbic acid for 4 weeks (differentiated cohort). 5-bromo-2′-deoxyuridine solution (BrdU) labeling was performed. In this randomized controlled in vivo study, a 5-mm mid-femoral defect was created and stabilized with angular-stable plating. In this randomized, controlled in vivo experimental study, on postoperative day 7 the animals were allocated to three groups (n = 5 per group): control (defect alone), undifferentiated mesenchymal stem cells, and differentiated mesenchymal stem cells. Radiographic assessment of bridging callus and cortical thickness index was performed at 4 and 6 weeks; serum total protein, calcium, and alkaline phosphatase were measured.