| Objective: In order to promote the osteogenesis and sclerosis during distraction osteogenesis,a high-purity magnesium pin was applied to the rat femur distraction osteogenesis model.The effects of high-purity magnesium on distraction osteogenesis of femur were studied by imaging,histology,and biomechanics.Potential mechanisms were detected using PCR-array and verified using Western Blot and histology.Therefore,it provides a cost-effective auxiliary treatment method for distraction osteogenesis in the clinic.Method: A high-purity magnesium pin having a diameter of 1 mm and a length of 5 mm was prepared.The rat femur distraction osteogenesis model was made and randomly divided into three groups:(1)High-purity magnesium group;(2)Stainless steel group;(3)Control group.Distraction osteogenesis was divided into 3 phases: the latency period of 7 days after surgery;the active distraction period of 2 weeks,during which gradual distraction was initiated at a rate of 0.25 mm/12 h(total 7 mm);and the consolidation period of 6 weeks.At the 3rd,6th,and 9th week after operation,samples were taken for micro-CT examination,histology,and immunohistochemistry.Continuous X-ray examinations were performed after anesthesia at 3,5,7,and 9 weeks after the three groups in the 9th week.Biomechanical tests were performed on tissues at the 9th week after surgery.After the operation,the tissues in the middle stage of consolidation(week 6)were analyzed by PCR-array to explore the underlying mechanism,and Western Blot detection and immunohistochemical verification were used.Results:(1)Successfully prepared high-purity magnesium pins with a diameter of 1mm and a length of 5mm.(2)The rat femur Distraction Osteogenesis model was successfully made.(3)The impact test results showed no significant difference between the three groups after the end of the distraction phase,but as the consolidation progressed,the highpurity magnesium group showed a faster mineralization rate.(4)Histological test results showed that there was a large amount of cartilage-like tissue in the stretch section after the end of the stretch in the three groups,and there was no significant difference.During the consolidation process,the high-purity magnesium group showed a faster hardening speed and basically completed the hardening process in the ninth week.In the stainless steel and control group,there was uncured completed cartilage tissue at the ninth week.(5)The biomechanical test is that at week 9 the ultimate load and fracture energy of the high-purity magnesium group are better than those of the other two groups.(6)The results of immunohistochemistry revealed that the CD31-positive vessels in the high-purity magnesium group were higher than those in the two control groups throughout the consolidation period.OCN-positive cells were higher in the 6th week than the two control groups,and there was a significant difference between the 3rd week and the 9th week.The angiogenesis-related PCR-array results showed that the expression of HL/ HIF-1α / VEGF pathway was increased in the high-purity magnesium group.(8)Western Blot validation results showed that the protein expression of VEGF and HIF-1α were higher than those of the control groups at three time points.VHL protein expression gradually decreased from 3 to 9 weeks.(9)Immunohistochemical results showed that qualitative immunostaining cells of VEGF and HIF-1α increased significantly,while VHL antibodies showed a significant decrease.Conclusion:(1)High-purity magnesium pins has the effect of promoting new bone sclerosis in the process of femoral distraction osteogenesis.(2)High-purity magnesium pins can be angiogenic during the distraction osteogenesis process.(3)High-purity magnesium promotes vascularization of rat femurs through the VHL / HIF-1α / VEGF pathway,further promoting distraction osteogenesis.In summary,the application of high-purity magnesium in the clinic can shorten the time for patients to carry an external fixator after distraction osteogenesis,and it is expected that the method of distraction osteogenesis for the treatment of bone defects will be more widely used,which has certain practical value. |
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