Change Of The Number Of Mesenchymal Stem Cells In Peripheral Blood Of Sprague-Dawley Rats During The Process Of Femur Distraction Osteogenesis

Objective:To establish a SD rat unilateral femur DO model using a mini distractor.To explore the number of mesenchymal stem cells(MSCs)in the peripheral blood(PB)of SD rat after latency period at different time points.In this study,we tested the hypothesis that in response to the gradual distraction stresses,there is a systemic mobilization of MSCs to "help" to achieve bone regeneration.The aims of this study were to explore the mechanism of DO and provide new strategy for shortening the treatment time of DO.Methods:Seventy-two SD rats were randomly divided into 3 groups(n=24),twenty of them were used to create the DO model.In this study,we establish a SD rat unilateral femur DO model.Twenty-four(A group)male SD rats underwent the left femur mini distractor implantation surgery.After a latency period of 5 days,gradual distraction was performed at a rate of 0.125mm twice a day for 16 days.At day 1,3,7,16after latency period,PB was collected from heart of rats in each groups.MSCs were harvested from PB by density gradient centrifugation.MSCs were analyzed with a monoclonal antibody panel:CD105,CD34,CD45 by flow cytometry.Twenty-four(B group)male SD rats underwent the left femur mini distractor implantation surgery.After a latency period of 5 days,SD rats were not limb lengthening after femur osteotomy.At day 1,3,7,16after latency period,PB was collected from heart of rats.MSCs were analyzed by flow cytometry.Blank control group(C group),not underwent the left femur mini distractor implantation surgery.At the same time points,MSCs were analyzed by flow cytometry.To evaluate the number of mesenchymal stem cells(MSCs)in the peripheral blood(PB)of SD rat after latency period at different time points.Results:All the animals tolerated the experimental procedure well.The left femur of all Tw-enty-four(A group)rats were lengthened successfully,and the distractors were fairly stable.At 8 weeks after consolidation period,the new bone tissue was close to normal bone tissue in the X-ray examination.Flow cytometry identified that cell surface markers CD105(+),CD34(-)and CD45(-).The number of peripheral blood mesenchymal stem cells in group A was significantly increased.The number of peripheral blood mesenchymal stem cellsn group B increased,but over time,the number gradually decreased.In group C,mesenchymal stem cells were not detected in circulating peripheral blood.Conclusion:The mini distractor was easy to operate and meet the requirements of the rat unilateral femur distraction osteogenesis.This rat femur DO model has superb feasibility and reproducibility,and can provide a favorable platform for further molecular and genetic study on DO.The number of MSCs in the peripheral blood was significantly increased during the distraction osteogenesis.But the laboratory flow cytometry has limited precision and the number of experimental studies of animals is less,the results still need further research.