Healing of Experimentally Created Non-Union of Femur in Rats Using Bone Precursor Cells from Mesenchymal Stem Cells (MSCs).

Background and objective: Around 20% of fractures have impaired or no healing. Many procedures have been tried with varying success. The objective of this study is to assess effect of osteoblast transplant (obtained after proliferation and differentiation of MSCs of bone marrow aspirate) in healing of experimentally created non-union of femur in rats.

Methods: Non-Union of femur were created in Sprague-Dawley rats weighing 200-250 grams. In 20 rats, Femur fracture was surgically created in 20 rats and 2 mm of the periosteum was cauterized on each side of the fracture and this created a non-union in 8 weeks. In 10 animals bone marrow was aspirated from the femoral shaft using 24-gauge butterfly needle and injected in special media. The two groups 10 each were marked and animals were kept in the similar surroundings. After radiological confirmation of non-union at 8 weeks, an injection containing 1 x 10 (6) osteoblasts cells (1 million cells) dissolved in 200 microliters of balanced salt solution was injected at the nonunion site. In the control group of 10 rats 1 ml of normal saline was injected. In 5 animals of each group the fracture was fixed using 1 mm kirschner wire and the other 5 were treated without fixation. After 8 weeks of implantation the animals were radiographed and euthanized. The hind legs were disarticulated from the hip joints, specimens were stored in 2% formalin and histological evaluation was performed.

Results: There were no deaths in both the groups and there was one superficial infection in the control group. Eight weeks post implantation of the BM-MSCs derived osteoblasts, all the fractures of the study group united with robust mineralization and new bone formation confirmed by radiograph and histopathology. In the control group there was no healing and the histopathology showed full of fibrous tissue with cartilage cells lining the fracture site.

Conclusions: In conclusion, our results indicate that implant of BM-MSCs derived osteo-progenitor cells at the non-union efficiently induces a complete union. We believe a similar study should be carried out in a larger animal before any human trials.