Mechanisms associated to the periodontal disease-induced alveolar bone loss in spontaneously hypertensive rats: Role of the renin-angiotensin system and microRNAs

Author(s)

Victor Gustavo Balera Brito

• Document type: Doctoral Thesis
• Press: Araçatuba. 2023-07-07.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araçatuba
• Defense date: 2023-06-23
• Advisor: Sandra Helena Penha de Oliveira

Abstract

Periodontal disease (PD) is a prevalent inflammatory disorder affecting the teeth' supporting and protective tissues. Due to its high prevalence, it is often associated with other comorbidities such as hypertension, which can contribute to its progression. The spontaneously hypertensive rat (SHR) is a model that exhibits similarities to essential hypertension in humans, as well as intrinsic bone impairment and increased alveolar bone loss associated with PD. Therefore, the aim of this study was to investigate two mechanisms, the renin-angiotensin system (RAS) and microRNA (miRNA) expression, to better understand the increased alveolar bone loss induced by PD in this model. Male Wistar and SHR rats at 10 weeks of age were used, and PD was induced by bilateral ligature placement on the lower first molars and maintained for 15 days. To evaluate the involvement of the RAS, the animals were treated with telmisartan (10 mg/kg/day), and we analyzed the alveolar bone architecture (micro-CT), RAS component expression (RT-qPCR and IHC-P), bone formation, remodeling, and resorption markers expression (RT-qPCR), and the production of inflammatory mediators in the mandible (ELISA). A microarray assay was used to investigate the differential expression of miRNAs associated with PD, followed by bioinformatics analysis to identify potential regulated pathways. The results showed that the SHR rat exhibited greater alveolar bone loss than the normotensive Wistar rat, partially prevented by telmisartan treatment. We observed a reduction in osteoclast markers, associated with decreased production of inflammatory mediators, inhibition of the angiotensin II type 1 receptor (Agtr1), and increased expression of the type 2 receptor (Agt2r) in the telmisartan-treated animals. However, we found that the modulation of RAS components was similar between Wistar and SHR rats, which did not explain the observed differences between the models. Interestingly, microarray analysis revealed a distinct profile of miRNAs related to immune response and bone metabolism in SHR rats, as well as differentially modulated miRNAs between the models that were not previously associated with periodontal homeostasis or disorders. In summary, we demonstrated that RAS components significantly contribute to alveolar bone loss but do not fully explain the increased progression observed in SHR rats. However, the differential modulation of miRNAs in hypertensive animals suggests their involvement in these differences, highlighting potential therapeutic targets for PD and other bone disorders as well, which may be of interest for guiding future research. In this context, from the differentially expressed miRNAs in PD, we selected a miRNA of interest, miR-127-3p, which presents a conserved sequences among multiple species (including rats, mice, and humans) and which role in osteogenesis has not been fully elucidated. We demonstrated an inhibitory effect of miR-127-3p on the osteogenic differentiation of human osteoprogenitor cells (bone marrow-derived mesenchymal stromal cells) through in vitro overexpression using a miRNA mimic. Further studies are needed to confirm an in vivo effect, but our results contribute to understanding the function of miR-127-3p in bone biology. Funding: CAPES (code 001), FAPESP (2015/03965-2, 2018/23676-3, and 2021/09597-6). (AU)

• FAPESP's process: 18/23676-3 - MicroRNAs role in bone impairment induced by periodontal disease and the local renin-angiotensin system in spontaneous hypertensive rats
• Grantee: Victor Gustavo Balera Brito
• Support Opportunities: Scholarships in Brazil - Doctorate