Bone Abstracts

The healing of skeletal fractures involves a cascade of overlapping cellular events. This study aims to deepen the understanding of molecular networks orchestrating these events.

Standard closed fracture in the left femur of male 8–10 weeks old C57BL/6N mice were analyzed at (day=D) D3, D7, D10, D14, D21 & D28 post fracture (N=5/time point). Total RNA was prepared for whole genome expression profiling using Illumina μ-array kit. Data normalization was performed using the “R” platform. The thresholds for filtering the differentially expressed (DE) genes were set at Fold-change≥|1| & P-value≤0.01. Functional enrichment analysis was performed using NCBI-DAVID and Cytoscape to identify genes of immune response, mitochondria, ribosome, angiogenesis, ossification and extracellular-matrix (ECM).

This study addresses the complexity of overlapping genes involved in the above mentioned biological processes during the different stages of healing. After gene ontology, 35 genes which were DE in more than one biological processes were further analyzed. As an overlapping gene between immune response, mitochondrion and angiogenesis: Glutathione Peroxidase-1 was DE at the early and later stages of healing to support the reactive oxygen species homeostasis. Similarly, the correlated gene between ossification and ribosome: Ubiquitin-B was DE during the early and later stages to control the osteoblast differentiation. However, the angiogenesis, ECM and ossification correlated gene: Matrix metallopeptidase-2 was DE until the endochondral ossification healing phase which plays a role in the remodeling of vasculature and encodes binding of collagens.

Currently, the detailed regulatory role of these genes and their involvement in different skeletal disorders are being investigated. However, the results indicate promising understanding of overlapping gene function between the cellular events.

Bone diseases or fractures leading to delayed or nun-union healing are often treated to enhance bone formation. Therefore, investigating gene expression overlapping -both chronologically and biologically- is crucial for the design of systemic or local therapeutic agents.