Structural and Morphometric Comparison of Lower Incisors in PACAP-Deficient and Wild-Type Mice

Area of Science:

• Neuroscience
• Developmental Biology
• Biomineralization

Background:

• Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide vital for nervous system development and function.
• PACAP-expressing nerve fibers are present in dental pulp, suggesting a role in tooth development.
• Previous studies indicated PACAP deficiency affects molar morphology in young mice.

Purpose of the Study:

• To investigate the role of PACAP in the morphometric and structural development of adult mouse incisors.
• To compare incisor development in wild-type and PACAP-deficient mice using advanced imaging and spectroscopic techniques.

Main Methods:

• Micro-computed tomography (micro-CT) was used for morphometric analysis and hard tissue density measurements of mandibles and incisors.
• Raman microscopy was employed for structural examination of thin sections of the mandible, focusing on dentin and enamel.
• Quantitative analysis of incisor size, pulp-to-dentin volume ratio, and mineral density was performed.

Main Results:

• PACAP-deficient mice exhibited significantly smaller incisors and a reduced relative pulp volume compared to wild-type mice.
• Dentin in PACAP-deficient mice showed reduced calcium hydroxyapatite density and increased carbonate/phosphate ratio, indicating higher intracrystalline disorder.
• Raman microscopy revealed no structural differences in enamel but highlighted significant alterations in dentin structure, including reduced structural diversity.

Conclusions:

• PACAP plays a critical role in regulating tooth morphogenesis, dentin, and enamel mineralization.
• PACAP deficiency leads to impaired incisor development and altered dentin structural integrity.
• Further research is needed to elucidate the molecular mechanisms underlying PACAP's influence on tooth development.