The effects of mesenchymal stem cells at different stages of bone regeneration after tibia fracture modeling on chemical composition of humerus in rats
Aim of the study is to test the effects of fracture in the proximal portion of the tibia and injection of mesenchymal stem cells at different stages of bone regeneration on chemical composition of the humerus by means of one-way ANOVA. Material and methods. Fracture of the tibia was modeled in all 162 male reta selected for the experiment. Mesenchymal stem cells (5E6 cells per injection) were injected intravenously with the respect to bone regeneration terms. The animals were withdrawn from the experiment in 7, 15, 30, 60 and 90 days after respective injection. Humeri were burned at 450-500°C for 12 hours. 10 mg of bone ash was dissolved in 10 ml of 0.1N pure hydrochloric acid. This primary solution was diluted by redistillated water to reach 25 ml of volume. This in turn was used for absorption photometer Saturt-2 that worked in emission mode with propane flame. Also we used colorimetric Briggs method by means of photoclolrimeter KFK-3. These tests provided us with data on micro- and macroelemental composition of bone mineral. Results. Fracture modeling had a significant effect on chemical composition of humerus during the whole experiment. Injection of MSC 3 days after intervention also had a significant effect on composition of bone mineral from the 7<sup>th</sup> up to the 90<sup>th</sup> day of the experiment. Peak influence came by the 90<sup>th </sup>day of the experiment and was observed in Ca/P ratio (η<sup>2</sup> - 0,760). MSC injection on the 10<sup>th</sup> day after intervention also had a significant effect on micro- and macroelemental composition of bone mineral during the whole experiment. Again, maximum effect on Ca/P ratio was registered on the 90<sup>th</sup> day of the experiment. Analysis of MSC effects on the 15<sup>th</sup> and the 24<sup>th</sup> days of the experiment showed that significant values of the same ratio appear in the period from the 30<sup>th</sup> to the 90<sup>th</sup> days of the experiment. Injection of MSC on the 45<sup>th</sup> day had a significant effect only on macroelemental composition. Conclusion. Fracture modeling of tibia exerts a significant effect on chemical composition of the humerus. IV injections of MSC at different stages of bone regeneration reduce negative effects of fracture. Intensity of the influence depended on injection terms.