microRNA-21 Contributes to Orthodontic Tooth Movement.

Area of Science:

• Biomedical Engineering
• Molecular Biology
• Orthodontics

Background:

• MicroRNAs are critical posttranscriptional regulators involved in bone remodeling.
• The role of microRNAs in responding to mechanical forces during orthodontic tooth movement (OTM) is largely unknown.
• microRNA-21 (miR-21) has shown potential in regulating osteogenesis and osteoclast differentiation.

Purpose of the Study:

• To investigate whether microRNAs respond to orthodontic forces and contribute to OTM.
• To elucidate the role of miR-21 in regulating alveolar bone remodeling during OTM.
• To explore the underlying molecular mechanisms of miR-21 in OTM.

Main Methods:

• Utilized miR-21 deficient (miR-21-/-) mice and wild-type littermates.
• Applied orthodontic force to induce tooth movement and analyzed alveolar bone changes.
• Investigated the expression of miR-21, programmed cell death 4 (Pdcd4), and C-fos.
• Examined OTM under conditions of lipopolysaccharide-induced periodontal inflammation.

Main Results:

• miR-21 expression responded to orthodontic force in a dose- and time-dependent manner.
• miR-21 deficiency inhibited OTM, reduced maxillary bone loss, and altered osteoblast and osteoclast activity.
• miR-21 regulates OTM by modulating Pdcd4 expression and subsequent C-fos activation.
• miR-21 deficiency blocked lipopolysaccharide-accelerated OTM and associated bone loss.

Conclusions:

• miR-21 is a critical regulator of alveolar bone remodeling during OTM.
• miR-21 influences osteoblastogenesis and osteoclastogenesis in response to mechanical force.
• The findings reveal a novel mechanism involving miR-21 in OTM, even in inflammatory conditions.