Can injection of adipose stem cells to non-union zone increase bone union? Experimental rat study

OBJECTIVES: This study aims to evaluate the effects of local adipose stem cell injection on non-union and diabetic non-union of rat femurs. MATERIALS AND METHODS: Forty-eight female Wistar albino rats (weighing mean 200 g and aged 8 weeks) were used in this study. The rats were divided into six groups. Group 1 was chosen as a reference for receptor activator of nuclear factor-kappa (k) B (RANK), receptor activator of nuclear factor-k B ligand (RANKL) and osteoprotegerin (OPG) genes and no femur osteotomy was performed in this group. Group 2 underwent femur osteotomy, the osteotomy was fixed with a 1.5 mm K-wire as retrograde from the knee joint, and no gap was left in the osteotomy line. In order to induce non-union, femurs underwent osteotomy fixed with K-wires in groups 3, 4, 5 and 6. In addition, the osteotomy line was measured as 1.8 mm gap with electronic calipers and the gap was fixed with U staple. Before osteotomy, streptozocin was injected intraperitoneally at a dose of 60 mg/kg in 0.1 mol/L citrate buffer solution (Ph 4.4) in groups 4 and 6, in order to induce diabetes mellitus. Left femur anteroposterior and lateral X-rays were taken 10 weeks after the operation and the union in group 2 and non-union in groups 3, 4, 5, and 6 were confirmed. To see if injection of adipose stem cells into the non-union site increases bone union, 2 mL 0.9% sodium chloride (NaCl) in groups 3 and 4 and 2×106 adipose stem cell in groups 5 and 6 were locally injected into the non-union area with fluoroscopy. Femur X-rays were taken eight weeks after the injection and all rats were sacrificed. Femurs of rats were removed for histopathological and gene expression evaluation. RESULTS: There were significant differences between the groups injected 0.9% NaCI and adipose stem cells in terms of bone healing according to radiological and histopathological evaluations (p<0.05). No statistically significant difference was observed between the groups in terms of gene expression levels. CONCLUSION: According to the results of our study, local adipose stem cell injection has positive radiological and histopathological effects in diabetic and non-diabetic femoral non-unions, independently of RANK, RANKL, or OPG gene expression pathways.