Date of Award

1-1-2018

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Biological Sciences

Content Description

1 online resource (xii, 140 pages) : color illustrations.

Dissertation/Thesis Chair

Melinda Larsen

Committee Members

Prashanth Rangan, Cara Pager, James Castracane, Yubing Xie

Keywords

Epithelial cells, Mesenchyme, Submandibular gland, Salivary glands, Nanobiotechnology

Subject Categories

Biology

Abstract

Current treatments for patients suffering from salivary hypofunction are insufficient and there is clinical need for regenerating the damaged tissue and restoring function of the gland. Reconstruction of 3D architecture is essential for stimulating secretory differentiation of epithelial progenitor cells in the salivary gland, which involves input from extracellular matrix and basement membrane as well as heterotypic cell interactions. However, the specific requirements for differentiation of secretory progenitor cells in salivary glands remain unclear. To determine what mechanisms and factors are required to promote proacinar differentiation, we isolated primary epithelial cells from embryonic day 16 (E16) submandibular salivary gland (SMG) that are highly enriched in the progenitor population Kit. By culturing E16 primary salivary gland epithelial cells, we demonstrated the requirement for basement membrane, soluble factors, and mesenchymal cells in supporting the proacinar phenotype. Basement membrane extracts prevented an EMT transition of cultured epithelial cells but did not promote expression of the proacinar marker, AQP5. E16 primary salivary mesenchyme also prevented EMT and additionally supported expression of AQP5 in co-culture, with a requirement for fibroblast growth factor 2 (FGF2) expression by the mesenchyme. Soluble factors secreted by the native mesenchyme were insufficient to support proacinar marker expression. Exogenous FGF2 but not EGF sustained proacinar phenotype in 3D salivary organoids in the presence but not in the absence of basement membrane extract and mesenchymal cells. Nanofiber scaffolds have been created to mimic the in vivo structure of the extracellular matrix (ECM). We have shown that the nanofiber scaffolds support the epithelial and proacinar phenotype in SMG organoids. These studies demonstrate a requirement for a complex microenvironment including mesenchymal signals and basement membrane to support proacinar secretory cell function and suggest that inclusion of mesenchyme capable of promoting secretory cell differentiation is necessary for elaboration of complex salivary organoids and potentially restoring gland function by in vivo transplantation.

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