Retinoic Acid Excess Impairs Amelogenesis Inducing Enamel Defects

Area of Science:

• Developmental Biology
• Oral Biology
• Toxicology

Background:

• Amelogenesis imperfecta (AI) and acquired enamel defects stem from issues in enamel matrix protein deposition, mineralization, or degradation.
• Environmental and nutritional factors may exacerbate enamel defects, prompting investigation into the role of retinoic acid (RA).

Purpose of the Study:

• To investigate if excess retinoic acid (RA) exposure during critical fetal development stages can cause enamel defects.
• To identify molecular mechanisms by which RA affects enamel and bone formation.

Main Methods:

• Pregnant mice were supplemented with RA, and offspring were assessed for enamel and bone abnormalities.
• Quantitative real-time PCR and RNA sequencing (RNA-seq) were used to analyze gene expression in developing teeth.
• Key genes involved in enamel formation (e.g., ENAM, AMBN) and bone development (e.g., RUNX2) were examined.

Main Results:

• RA supplementation during embryonic development (E12.5-E16.5) resulted in severe enamel defects in adult mice.
• RA excess significantly reduced mRNA levels of enamel matrix proteins (ENAM, AMBN, ODAM) and affected bone mineralization and craniofacial ossification.
• RNA-seq revealed perturbations in bone growth factors, extracellular matrix, and calcium homeostasis, with reduced expression of RUNX2 and AI-associated genes.

Conclusions:

• Elevated RA signaling during fetal stages adversely affects dental cell lineages, leading to impaired enamel protein production.
• This impairment results in permanent enamel alterations, suggesting a potential environmental contribution to AI-like phenotypes.
• RA acts as a teratogen affecting tooth and bone development through disruption of key regulatory pathways.