Effect Of Hypobaric Hypoxia Environment On Bone Healing And Its Transcriptomic Analysis By RNA-seq

BackgroundBecause of its special political,social,economic,military functions,high altitude has been highly valued by many countries.As a consequence of the globalization process recently,human migration has accelerated.The unique position of the high altitude region is becoming more and more important.Thus high altitude medicine has considerable developed.The traditional high altitude medicine was focused on the influence on respiratory,cardiovascular and blood system caused by high altitude environment.In recent years,a large number of literatures have pointed out that the osteogenesis in high altitude is different from that in plain area.However,the influence of high altitude environment on bone tissue is still controversial,and the mechanism is unknown.ObjectiveTo observe the effect of high altitude environment on normal bone tissue and bone repair capacity and provide the gene profiling of bone tissue in the rats which are treated in hypoxia environment by RNA-sequencing(RNA-seq)analysis.Aim to elucidate the mechanism and provide possible preventive strategies.Methods1.The adult rats were housed in hypobaric hypoxia chamber or normoxia room respectively for 21 days.Comparising the pathological changes of body weight and haematological values of the rats in both groups.The micro structure,histology and biomechanical properties of femurs were observed.2.Total RNA was extracted from the femurs of rats in both groups,and an RNA-seq analysis was performed.The Gene Ontology(GO)analysis was used to uncover the biological functions of the differentially expressed genes(DEGs).The Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway enrichment analysis was used to find out the related signal pathways.3.After establishing the reproducible animal model of bone defect,we put the rats into the hypobaric hypoxia chamber or normoxia room conditions for 21 days.Then the repair ability of the rats in two groups was compared by micro-CT,histochemical staining and biomechanical properties.4.Collect the middle femur including callus tissue of the two groups.Total RNA was extracted from bone tissue.Then RNA sequencing was performed to screen the DEGs of the groups.The GO analysis and KEGG pathway enrichment were used to generate a comprehensive view of the mechanisms involved.Results1.After the 21-d treatment,the variation of body weights and haematological values confirmed that the simulative hypobaric hypoxia environment was effective,and the rats in the HX group had physiologically adapted to it.The micro-CT realistic 3D images and the histological observation showed that the HX group exhibited less trabecular bone in the distal metaphysis of their femurs.The biomechanical properties of the femoral diaphysis were impaired by the hypobaric hypoxic environment.2.There were a total of 846 significantly DEGs in the two groups,including 289 upregulated and 557 downregulated in the HX group.The DEGs were categorized into 293 functional categories by GO analysis.The KEGG pathway analysis suggested 17 significant signal pathways.3.We established an animal model which had a standard bone defect and proved to be reproducible.After the treatment of 21 days,the filling bone callus in the bone defect was less in the hypoxia group,and most of them was new bone and cartilage.In contrast,the normoxic group has more mature callus.There was no significant difference in the biomechanics between the two groups.4.We found 2999 DEGs in the two groups.1359 genes were upregulated and 1640 were downregulated in the hypoxia group.GO analysis showed 310 functional categories.40 significant signal pathways were identified by the KEGG analysis.Conclusions1.The hypobaric hypoxia environment negatively influenced bone strength and quality in rats.2.There were a total of 846 DEGs in the bone tissue of the two groups,and they were enriched in 17 significant signal pathways.3.The animal model we established had a standard bone defect and proved to be reproducible.4.The hypobaric hypoxia environment impaired the repair of the bone defect.5.The hypobaric hypoxia environment induced 2999 DEGs in the callus of the bone defect and 40 significant signal pathways were enriched.