Expression patterns of miR-34b, miR-34c, and miR-141 during aging and mechanical force application in periodontal ligament cells

Abstract

Background and Objective: Age changes as well as mechanotransduction events in periodontal ligament (PDL) cells influence the outcome of mechanical forces as well as physiologic homeostasis in a larger way. Numerous studies have reported changes in inflammatory marker levels as well as cellular density as age advances with PDL fibroblasts as model. MicroRNAs (miRNAs) regulate messenger RNAs in either up regulating or down regulating protein synthesis and forms the determinant of cellular function as well as maintenance of tissue homeostasis. No studies till now have utilized in vivo PDL cell model for assessing miRNA levels as age advances and to study their response to mechanical force application. This study forms the first of its kind and evaluated the expression pattern of three miRNAs - miR-34b, miR-34c, and miR-141 - in aging PDL cells as well as with orthodontic force application. Materials and Methods: Twelve subjects were recruited and divided into three groups and subjected to mechanical force application. First premolar teeth designated for extraction were selected as specimens from the first three groups (Groups A-C). Mechanical force was applied to first premolar teeth designated for therapeutic extraction as part of orthodontic treatment for 21 days in the fourth group (Group D). All teeth were carefully extracted, and PDL from middle third of the root was scraped with a scalpel. Cells isolated from aged as well as mechanical force applied human premolar teeth were subjected to reverse transcriptase polymerase chain reaction, miRNA analysis, and quantification with ImageJ software. Results: Age-dependent changes in miRNA - looking at the expression bands, miR-141 showed significant change in the Group C specimens when compared to other two groups. The expression of miR-34b and miR-34c showed a steady increase as age advanced with Group C values being significantly different statistically from Groups A and B. Mechanical force application induced significant changes in miRNA expression - miR-141 showed statistically significant elevation in its expression once the PDL fibroblasts are subjected to mechanical force application. There is decrease in expression levels of miR-34b and miR-34c. Hence, it is elucidated that elevated miR-141 expression indicative of oxidative stress the cells might be undergoing and suggestive of initiation of DNA damaging effects. Conclusions: The present study could demonstrate that, as age advances, there is an elevated expression of all the miRNAs indicating its role in physiologic maintenance of cellular integrity, tumor suppressive properties, and cellular senescence. miR-141 expression is elevated in PDL fibroblasts subjected to mechanical force application indicative of oxidative stress, the cells might be undergoing and suggestive of initiation of DNA damaging effects.