AnIn VitroCulture System for Long-Term Expansion of Epithelial and Mesenchymal Salivary Gland Cells: Role of TGF-β1 in Salivary Gland Epithelial and Mesenchymal Differentiation

Abstract

Despite a pivotal role in salivary gland development, homeostasis, and disease, the role of salivary gland mesenchyme is not well understood. In this study, we used theCol1a1-GFPmouse model to characterize the salivary gland mesenchymein vitroandin vivo. TheCol1a1-GFPtransgene was exclusively expressed in the salivary gland mesenchyme.Ex vivoculture of mixed salivary gland cells in DMEM plus serum medium allowed long-term expansion of salivary gland epithelial and mesenchymal cells. The role of TGF-β1 in salivary gland development and disease is complex. Therefore, we used thisin vitroculture system to study the effects of TGF-β1 on salivary gland cell differentiation. TGF-β1 induced the expression of collagen, and inhibited the formation of acini-like structures in close proximity to mesenchymal cells, which adapted a fibroblastic phenotype. In contrast, TGF-βR1 inhibition increased acini genes and fibroblast growth factors (Fgf-7andFgf-10), decreased collagen and induced formation of larger, mature acini-like structures. Thus, inhibition of TGF-βsignaling may be beneficial for salivary gland differentiation; however, due to differential effects of TGF-β1 in salivary gland epithelial versus mesenchymal cells, selective inhibition is desirable. In conclusion, this mixed salivary gland cell culture system can be used to study epithelial-mesenchymal interactions and the effects of differentiating inducers and inhibitors.