Unbiased gene expression analysis of the delayed fracture healing observed in Zucker diabetic fatty rats

Aims Impaired fracture repair in patients with type 2 diabetes mellitus (T2DM) is not fully under-stood. In this study, we aimed to characterize the local changes in gene expression (GE) as-sociated with diabetic fracture. We used an unbiased approach to compare GE in the fracture callus of Zucker diabetic fatty (ZDF) rats relative to wild -type (WT) littermates at three weeks following femoral osteotomy. Methods Zucker rats, WT and homozygous for leptin receptor mutation (ZDF), were fed a moderately high -fat diet to induce T2DM only in the ZDF animals. At ten weeks of age, open femoral fractures were simulated using a unilateral osteotomy stabilized with an external fixator. At three weeks post-surgery, the fractured femur from each animal was retrieved for analy-sis. Callus formation and the extent of healing were assessed by radiograph and histology. Bone tissue was processed for total RNA extraction and messenger RNA (mRNA) sequencing (mRNA-Seq).Results Radiographs and histology demonstrated impaired fracture healing in ZDF rats with incom-plete bony bridge formation and an influx of intramedullary inflammatory tissue. In compar-ison, near-complete bridging between cortices was observed in Sham WT animals. Of 13,160 genes, mRNA- Seq analysis identified 13 that were differentially expressed in ZDF rat callus, using a false discovery rate (FDR) threshold of 10%. Seven genes were upregulated with high confidence (FDR = 0.05) in ZDF fracture callus, most with known roles in inflammation.Conclusion These findings suggest that elevated or prolonged inflammation contributes to delayed frac -ture healing in T2DM. The identified genes may be used as biomarkers to monitor and treat delayed fracture healing in diabetic patients.

Automated summary

This study found that impaired fracture healing in patients with type 2 diabetes mellitus (T2DM) may be due to elevated or prolonged inflammation. Gene expression analysis revealed several upregulated genes associated with inflammation in the fracture callus of T2DM rats. These identified genes may serve as biomarkers for monitoring and treating delayed fracture healing in diabetic patients.