Periodontitis is a complex infectious disease with various causes and contributing factors [16]. An increasing number of studies are now being conducted on the diagnosis and treatment of periodontitis. However, due to the limited understanding of the pathogenesis of periodontitis, the prognosis of patients with periodontitis remains poor. MicroRNAs are a family of endogenous, non-coding, small RNA molecules that play important roles in regulating gene expression at the post-transcriptional level [17]. Recently, microarray technology has been used to reveal thousands of gene changes in the development of various diseases.
The expression of miRNA can be modulated by transcription factors [18, 19], and thus, we identified those that could potentially regulate candidate DEMis in periodontitis. Egr-1, a zinc finger transcription factor [20], was predicted to account for the highest percentage of downregulated DEMis. Trabandt et al. showed that Egr-1 plays a crucial role in cellular proliferation and collagenase expression in in vivo gingival and periodontal tissue destruction [21]. Shi et al. found that curcumin promotes osteogenic differentiation of human periodontal ligament stem cells by inducing EGR1 expression [22].
We reconstructed an miRNA-mRNA regulatory network comprising 32 mRNAs and 6 miRNAs. We also calculated the degree, closeness, and betweenness of the genes in the network. The top 10 nodes included hsa-miR-203, hsa-miR-671-5p, hsa-miR-223, hsa-miR-486-5p, hsa-miR-1246, ENTPD1, CXCL8, BTG2, SEL1L3, and DNAJB9. Among the ten hub genes, hsa-miR-203 showed a significant inverse correlation with CXCL8, BTG2, SEL1L3, and DNAJB9 expression, which are believed to play critical roles in the development and pathological mechanisms of periodontitis.
MicroRNA-203 was first identified in the pathogenesis of psoriasis and is involved in various physiological and pathological processes [23]. Zhang et al. demonstrated that miR-203 overexpression suppresses TRAF6-induced IL-β, IL-6, and TNF-α activation in human renal mesangial cells and proximal tubular cell line cells [24]. A recent study showed that miR-203 protects against microglia-mediated brain injury by targeting the protein MyD88 to modulate the inflammatory response [25]. Furthermore, Wang et al. showed that miR-203 inhibits inflammation to alleviate myocardial ischemia-reperfusion injury [26].
CXCL8, BTG2, and DNAJB9 were selected as key genes in the miRNA-mRNA network. CXCL8, a potent neutrophil chemoattractant and activator, plays a crucial role in the progression of chronic periodontitis [27]. It causes the destruction of periodontium via accumulation and degranulation of neutrophils [28, 29]. Moreover, CXCL8 significantly upregulates elastase release by neutrophils, which contributes to the progression of human chronic periodontitis [30]. BTG2, also known as pheochromocytoma cell 3 or tetradecanoyl phorbol acetate-inducible sequence, belongs to the antiproliferative (APRO) gene family [31]. Previous studies have reported that BTG2 expression is positively correlated with development, particularly with terminal differentiation [32, 33]. Normally, DNAJB9 is localised to the endoplasmic reticulum and protects cells from stress-mediated apoptosis [34]. Nasr et al. identified DNAJB9 as a specific immunohistochemical marker for fibrillary glomerulonephritis [35], and its role in the diagnosis and treatment of periodontitis needs to be further elucidated.
KEGG pathway analysis showed that mRNAs in the regulatory network were mainly enriched in the IL-17 signalling pathway. In previous studies, the activation of the IL-17 signalling pathway has been shown to be associated with periodontitis. A study performed by Satoru showed that IL-17A may promote the progression of periodontitis through pro-inflammatory cytokine production [36]. Moreover, IL-17 is essential for the maintenance of bone mass as it orchestrates osteoclast differentiation and activation [37]. Inana revealed that IL-17 inhibited both the proliferation and migration of periodontal ligament mesenchymal stem cells and decreased their osteogenic differentiation by activating ERK1/2 and JNK mitogen-activated protein kinases [38]. Therefore, inhibition of the IL-17 signalling pathway may be a therapeutic strategy for periodontitis.
Although we constructed the potential miRNA–mRNA regulatory network by integrating multiple microarray datasets for the first time, our study is limited by the fact that predictions were made based on public databases; further in vivo and in vitro studies are required to validate our findings.