Evidence for Bicarbonate Secretion by Ameloblasts in a Novel Cellular Model.

Area of Science:

• Cell Biology
• Biochemistry
• Dental Enamel Research

Background:

• Amelogenesis involves proton generation, necessitating bicarbonate (HCO3-) transport for neutralization.
• Ameloblasts are suspected to transport HCO3-, but direct functional evidence was lacking.
• Understanding HCO3- transport is crucial for enamel development and health.

Purpose of the Study:

• To investigate the functional evidence of HCO3- transport in ameloblasts.
• To establish and validate a polarized cell culture model for studying ameloblast transport.
• To elucidate the mechanism and regulation of HCO3- secretion during amelogenesis.

Main Methods:

• Development of a 2D polarized HAT-7 rat ameloblast cell line culture system on Transwell filters.
• Measurement of transepithelial electrical resistance to assess barrier integrity.
• Analysis of tight junction and transporter protein expression using RT-PCR.
• Assessment of intracellular pH regulation and HCO3- transport via microfluorometry.
• Stimulation of transport using Ca2+ and cAMP-mobilizing agents.

Main Results:

• HAT-7 cells formed polarized epithelial layers with functional tight junctions (Claudin-1, -4, -8).
• Cells exhibited polarized HCO3- transport, with basolateral uptake sensitive to Na+ withdrawal, acetazolamide, and H2DIDS.
• Transepithelial HCO3- transport significantly increased upon stimulation with Ca2+ and cAMP.
• The HAT-7 cell line demonstrated vectorial, regulated basolateral-to-apical bicarbonate transport.

Conclusions:

• The HAT-7 cell line serves as a validated functional model for studying ameloblast electrolyte transport.
• Evidence supports regulated, vectorial HCO3- transport in ameloblasts, crucial for enamel mineralization.
• This model facilitates further research into the mechanisms of enamel formation and related disorders.