Purpose:Distraction osteogenesis is one of the most popular treatment modality in the correction of congenital craniofacial anomalies. Despite its great advantages, long treatment periods, fibrous union  or even non-union of the bone  are possible draw backs of this technique. Various attempts have been made to accelerate callus formation and shorten the consolidation period including stem cells (1).In this study mesenchymal stem cells and osteoblast- like cells were used for  acceleration of  bone maturation in rat mandibular distraction osteogenesis model. We aimed to determine the effect of stem cells treatment on accelatration of bone formation and compare the result of  two different  stem cells treatment.

Methods:

Thirty Sprague-Dawley rats were used.  Following  the vertical osteotomy on the right hemimandible, a custom-made distraction device was applied(2). After a 3-days latency period, the mandibles were distracted at a rate of 0,25 mm/day for 6 days (total 3mm). Allogenic bone –morrow derived mesenchymal stem cells and osteoblast- like cells were cultured to  a population of 10⁶ in 0.3 ml. End of the activation period rats were randomly  divided into 3 groups (n=10). The rats in group 1 (control group) had physiological saline injection. The rats  in group 2 and 3, had  mesenchymal stem cells and osteoblast-like cells injection into the  distraction gap, respectively (Figure-1). The distracted areas were evaluated by radiographic, scintigraphic, histomorphometric analysis at 2^nd and 4^th week(end) of the consolidation period (2). 

Results:

Radiographic evaluation indicated a significant  bony union of distraction regenerate in treatment  groups compared with  control group at 2^nd week of consolidation. Histomorphometric analysis demonstrated that new bone formation was  significantly greater in stem cells  injected groups when compared that of control group at 2^nd and 4^th week of consolidation period (Figure-2-3). Scintigraphic mean uptake ratios were significantly lower in stem cells  injected groups  compared with the control group at 2^nd and 4^th week of consolidation (Figure-4-5). No statistically significant difference  observed between the stem cell treatment groups. 

Conclusions:

The results show that both transplantation of mesenchymal stem cells and osteoblast-like cells promotes maturity of regenerated bone at  2^nd and 4^th week of consolidation period. It appears that no need to differentiate the mesencymal stem celll to the osteoblast-like cells for acceleration of bone formation.

References:

1.            Cetrulo CL Jr, Knox KR, Brown DJ. et al. Stem cells and distraction osteogenesis endothelial progenitor cells home to the ischemic generate in activation and consolidation.Plast and Reconstr Surg 2005 Sep 15;116(4):1053-64.

2.            Eski M., Ilgan S., Cil Y., Sengezer M., Ozcan A., Yapici K. Assessment of distraction regenerate using quantitative bone sintigraphy, Annals of Plastic Surgery  58 (3): 328-34, 2007.

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