Change of the number of mesenchymal stem cells in peripheral blood of rats after fracture

[Objective]To compare the number of mesenchymal stem cells(MSCs) in the peripheral blood(PB) of rats after fracture at different time points with non-fractured control and evaluate the biological features of MSCs from PB and bone marrow(BM).[Method]SD rats were randomly divided into 4 groups:control group,groups of fracture for 1,3,7 d,n=20.At day 1,3,7 after fracture,PB was collected from heart of rats in each groups.MSCs were harvested from PB by density gradient centrifugation.The number of the colony forming unit-fibroblasts(CFU-Fs) was counted when peripheral blood mononuclear cells were cultured at 14d.MSCs were analyzed with a monoclonal antibody panel:CD44,CD90,CD34,CD45 by flow cytometry.Multipotent differentiation was identified through osteogenic and adipogenic induction.[Result]The primary MSCs from PB formed colonies.Significant differences in colony numbers of MSCs were found between fracture groups and control group,among which the largest number of colonies were formed by group of fracture at 3 d(P0.01)(27.25-11.52 CFU-Fs/culture vs 2.80-3.96 CFU-Fs/culture).PB derived MSCs were similar to BMderived MSCs,except for a small population(20%) of CD34 cells among MSCs from PB.Twenty-eight days after osteogenic induction of MSCs,calcium deposition was detected by Alizarin Red,21 days after adipogenic differentiation,lipid droplets were detected by oil red.[Conclusion]PB derived MSCs cultured in vitro can differentiate into osteoblasts and adipocytes.Peripheral blood of rats after fracture has more cells with MSC phenotypes than blood from the non-fractured control.MSCs may be involved in fracture repair.