Bcl-2 expression is essential for development and normal physiological properties of tooth hard tissue and saliva production

•Lack of Bcl-2 expression led to impaired production of enamel ACP crystals.•Germline deletion of Bcl-2 reduced the surface microhardness of enamel.•Bcl-2 expression is vitally important for SMG function and saliva production.•Lack of Bcl-2 expression was not compensated by expression of other Bcl-2 family members.

BackgroundApoptosis plays a fundamental role in appropriate tissue development and function. Although expression of Bcl-2 has been reported during tooth and submandibular gland (SMG) development, the physiological role Bcl-2 plays during these processes has not been addressed. This study was performed to evaluate the impact of Bcl-2 expression on the formation and properties of tooth hard tissue, and saliva production.MethodsTwenty-four mice (12 males and 12 females) were divided into three groups of eight (n=8): group A (Bcl-2 +/+), group B (Bcl-2 +/-), and group C (Bcl-2 -/-) and subjected to micro-CT analyses. The mineral content of first molars was analyzed by X-Ray diffraction (XRD) and scanning electron microscopy (SEM) color dot map. The surface microhardness was determined by Vickers test on labial surfaces of incisors. Saliva was collected from different groups of mice after subcutaneous injection of pilocarpine.ResultsSamples from Bcl-2 -/- mice showed significantly smaller micro-CT values, lower and poor crystallinity of hydroxyapatite (HA), and lowest surface micro hardness. SMG from Bcl-2 -/- mice showed remarkable reduction in size, consistent with reduced saliva accumulation.ConclusionsThe absence of Bcl-2 expression in SMG did not affect the expression of other Bcl-2 family members. Thus, Bcl-2 expression influence on the formation and properties of tooth hard tissue, and saliva accumulation.SignificanceBcl-2 expression has a significant impact on the mineralogical content of enamel crystals of tooth structure. Lack of Bcl-2 expression led to impaired production of enamel ACP crystals.