Saliva plays an important role in maintaining oral hygiene, buffering, digestive, antibacterial, immunological functions in addition to keeping the oral cavity moist, and thereby it contributes disease prevention and health maintenance. Xerostomia is caused by decreased saliva secretion due to aging, medication, or after radiotherapy and leads to the decrease of oral functions including difficulty in chewing and swallowing. Therefore, xerostomia is a factor to be considered in the diagnosis of oral frailty for healthy life expectancy in a super-aged society.
During salivary gland development, parasympathetic ganglia in glands control the branching morphogenesis of the salivary gland epithelium. Acetylcholine, a parasympathetic neurotransmitter, activates muscarinic acetylcholine receptors and M3 muscarinic receptor subtype is important for the salivary secretion. We found M1 muscarinic receptor subtype was predominantly expressed in the salivary gland epithelium compared with other subtypes of muscarinic/nicotinic receptors during salivary gland organogenesis. 
In this presentation, we will introduce the molecular mechanism of M1 muscarinic receptor subtype during mouse submandibular gland development and discuss strategies for functional organ regeneration based on our research.