Article
Differential expression of mitochondrial and ribosomal genes during fracture healing in mouse
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Published: | October 23, 2017 |
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Objectives: Fracture healing involves a series of consecutive overlapping cellular events. This study aims to unravel the importance of mitochondrial and ribosomal genes during fracture healing process.
Methods: A closed standard mid diaphyseal fracture in the left femur of 8 weeks old C57BL/6N male mice were analyzed at (day = D) D3, D7, D10, D14, D21& D28 post fracture (N = 5 / time point). Total RNA was isolated to perform whole genome expression profiling using Illumina µ-array kit. "R" language was used for data normalization and statistical analysis. Differentially expressed genes (DEGs) were obtained using threshold of fold-change (FC) ≥ |2| and p-value ≤ 0.01. Gene ontology analysis was performed using NCBI-DAVID to identify mitochondrial and ribosomal genes. Cytoscape and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to perform the regulatory network and pathway analysis. Furthermore, DEGs were mapped with human skeletal disorders.
Results and Conclusion: Despite the importance of biological processes like angiogenesis, ossification, extracellular matrix (ECM), immune response behind the fracture healing process, very little is known about the importance of mitochondrial and ribosomal genes during different stages of healing. This study mainly addresses the DEGs involved in mitochondrial and ribosomal activity. Gene ontology analysis showed the presence of angiogenesis, ossification, ECM, immune response, mitochondrial and ribosomal activity. 115 genes were significantly upregulated and 275 genes were significantly downregulated in at least one time point. Mitochondrial and ribosomal genes are crucial for energy metabolism and protein synthesis respectively. Mitochondrial genes were significantly downregulated at all time points. Ribosomal genes were significantly downregulated only at D3 and D7. Genes like 3-Oxoacid CoA - transferase 1 (Oxct1), Nucleophosmin (Npm1), and Electron transfer flavoprotein alpha subunit (Etfa) was significantly downregulated during early stage of fracture healing. Oxct1 plays a key role in ketone body catabolism. Npm1 gene is involved in cell proliferation activity and mutation results in myeloid leukemia. Etfa gene serves as an electron acceptor during energy metabolism and respiratory electron transport. Currently, the detailed and regulatory role of mitochondrial and ribosomal genes during Wnt and MAPK pathways are being investigated. However, the results indicate regulatory role of mitochondrion and ribosome during fracture healing process.
Bone diseases or fractures leading to delayed or nun-union healing are often treated to enhance bone formation. Therefore, biological investigation of gene expression is important to design systemic or local therapeutic agents.