Zoledronic Acid-Treated Rats Show Altered Jaw Histology and Gene Expression in Nonexposed Medication-Related Osteonecrosis of the Jaws

Abstract

Background

Diagnosis and management of medication-related osteonecrosis of the jaws (MRONJ) prior to clinical exposure induced by trauma may lead to improved patient management. Currently, few studies have examined early histologic and molecular MRONJ-related changes in the jaws.

Purpose

This study aimed to identify histological and gene expression changes in the maxilla and mandible of Sprague-Dawley (SD) rats after zoledronic acid (ZA) treatment.

Study Design, Setting, and Sample

This was an in vivo animal study. The experiments were conducted in the laboratory at the Stomatology Hospital of Tianjin Medical University. A total of 12 SD rats were included.

Predictor Variable

The predictor variable was ZA exposure. Twelve SD rats were divided into 2 groups: experimental (n = 6) and control (n = 6), and they were intraperitoneally injected with ZA and saline, respectively.

Main Outcome Variable

The outcome variables were histological and molecular changes. The maxilla, mandible, and ilium bone tissue samples were examined using Masson's trichrome and hematoxylin-eosin staining. Gene expression changes were identified using transcriptome sequencing, the Kyoto encyclopedia of genes and genomes, and gene interactome network analysis. The key changes were validated using the quantitative real-time polymerase chain reaction and immunohistochemistry.

Covariates

None.

Analyses

The t-test, χ² test, and Fisher's exact probability method were used for statistical analyses using the Statistical Package for the Social Sciences software (version 26.0).

Results

All animals remained healthy during the experiments. Histological staining revealed that the percentage of empty bone lacunae in the maxilla and mandible was significantly higher than that in the ilium (P < .01). In total, 552 genes were screened using transcriptome sequencing. The sonic hedgehog (Shh) signaling pathway was highly enriched. The key gene for the Shh interaction was distal-less homeobox 5. The Shh, distal-less homeobox 5, and bone morphogenetic protein 2 genes and protein expression levels in the maxilla and mandible were higher in the experimental group than in the control group (P < .05).

Conclusion and Relevance

MRONJ-induced osteonecrosis and gene expression changes precede trauma-induced clinical changes in the SD rat model. These findings may provide additional support for timely and clinically early diagnosis and intervention.