Effect of autologous mesenchymal stem cells on biological healing of allografts in critical-sized tibial defects simulated in adult rabbits.

INTRODUCTION This study evaluated the effect of autologous bone marrow derived adult Mesenchymal Stem Cells (MSCs) on the biological healing of weight bearing diaphyseal bone allograft in the tibia of adult rabbits. MATERIALS AND METHODS Forty Adult New Zealand White Rabbits divided into 3 groups (Autograft, Allograft or Allograft impregnated with MSCs) with 12 rabbits in each group were used for the study. A 1.5 cm of cortical bone segment was excised from the rabbit's right tibia. The segment was replaced by an Autograft, Allograft or Allograft loaded with MSCs, depending on which group the rabbit was assigned. Internal fixation was performed using a 9-hole Mini-compression Plate and Cerclage Wires. Rabbits were sacrificed at end of observation periods of 12, 16 and 24 weeks. Specimens procured were assessed clinically and radiologically and fixed in 10% buffered formalin. For each specimen, 5 μm undecalcified sections were cut and stained with Von Kossa and Toluidine Blue stains. Histomorphometery was then performed. RESULTS Our study showed that addition of autologous MSCs to diaphyseal allograft segments enhances and accelerates not just the union at host graft junctions and also the biological incorporation of the allograft segment as shown by Resorption Index, New-Bone Formation Index and Osteocyte Index. CONCLUSIONS The addition of autologous MSCs to deep frozen cortical allograft segments improved the host - allograft union rate and biological incorporation of diaphyseal allografts as shown by resorption activity, new bone formation and osteocyte cell counts.