Genome Wide Pathway Analysis of Diabetes Effect on Osseous Healing

Aim: To characterise the effect of experimental diabetes on the gene profiles expressed at different stages of intramembranous bone healing.

Materials & Methods: Eighteen Wistar male rats were allocated in three experimental groups: 1) uncontrolled, streptozotocin induced, experimental diabetes; 2) insulin controlled experimental diabetes; 3) healthy controls. Critical size calvarial defects were created in each parietal bone and treated with intracranial and extracranial placement of ePTFE membranes. RNA isolated from tissue samples obtained following 7 and 15 days of healing, was hybridised to Affymetrix 230 2.0 GeneChips. Differential gene expression between experimental groups was statistically tested, using the Linear Models (LIMMA) Bioconductor test. Pathway and Gene Ontology analyses were conducted using GenMAPP for identification of global biological trends in gene expression data.

Results: Experimental diabetes was associated with upregulation of genes involved in the MAPK signalling, IL-4, IL-6 and adipogenesis pathways at 7 days of healing (z-score>2). The α6β4integrin and TNFa-NF-kB pathways were under-expressed in the diabetic versus the healthy group at 15 days of healing (z-score>2). The diabetic status further correlated with significantly decreased expression of genes involved in osteoblast differentiation, ossification and bone mineralisation, such as BMP4, thyroid hormone receptor, TGFb binding protein and CD276 antigen (p<0.05). Significantly enriched pathways in insulin controlled diabetes included the MAPK signalling, cytokines and inflammatory response, IL-1, IL-6, adipogenesis, integrin mediated cell adhesion and cytoplasmic ribosomal proteins (z-score>2).

Conclusion: Genome-wide expression profiling revealed transcriptomic variation and perturbed pathways in intramembranous bone healing depending on the metabolic status. The data provide suggestions on the molecular pathogenesis of diabetes impaired osseous healing.