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

This study aims to evaluate the effects of local adipose stem cell injection on non-union and diabetic non-union of rat femurs.

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 (κ) B (RANK), receptor activator of nuclear factor-κ 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.

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.

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.