Silk Fibroin Scaffolds Promote Formation of theEx VivoNiche for Salivary Gland Epithelial Cell Growth, Matrix Formation, and Retention of Differentiated Function

Abstract

Salivary gland hypofunction often results from a number of causes, including the use of various medications, radiation for head and neck tumors, autoimmune diseases, diabetes, and aging. Since treatments for this condition are lacking and adult salivary glands have little regenerative capacity, there is a need for cell-based therapies to restore salivary gland function. Development of these treatment strategies requires the establishment of a system that is capable of replicating the salivary gland cell "niche" to support the proliferation and differentiation of salivary gland progenitor cells. In this study, a culture system using three-dimensional silk fibroin scaffolds (SFS) and primary salivary gland epithelial cells (pSGECs) from rat submandibular (SM) gland and parotid gland (PG) was established and characterized. pSGECs grown on SFS, but not tissue culture plastic (TCP), formed aggregates of cells with morphological features resembling secretory acini. High levels of amylase were released into the media by both cell types after extended periods in culture on SFS. Remarkably, cultures of PG-derived cells on SFS, but not SM cells, responded to isoproterenol, a β-adrenergic receptor agonist, with increased enzyme release. This behavior mimics that of the salivary glands in vivo. Decellularized extracellular matrix (ECM) formed by pSGECs in culture on SFS contained type IV collagen, a major component of the basement membrane. These results demonstrate that pSGECs grown on SFS, but not TCP, retain important functional and structural features of differentiated salivary glands and produce an ECM that mimics the native salivary gland cell niche. These results demonstrate that SFS has potential as a scaffold for creating the salivary gland cell niche in vitro and may provide an approach for inducing multipotent stem cells to provide therapeutically meaningful numbers of salivary gland progenitor cells for regenerating these tissues in patients.

Encapsulation of primary salivary gland cells in enzymatically degradable poly(ethylene glycol) hydrogels promotes acinar cell characteristics

“…These soluble factors could be explored as a means to restore Mist1 expression in vitro . Supplementation of ascorbic acid in cultures of primary SMGs on silk fibroin hydrogels resulted in increased secretory granule formation, although Mist1 expression was not examined [80]. …”

Organotypic Spheroid Culture to Mimic Radiation-Induced Salivary Hypofunction

“…In recent years, organotypic culture models have been developed to better mimic in vivo structural and physiologic conditions. In these models, cells grow in a 3D fashion within or on 3D-forming matrices (Chan et al 2012; Pradhan-Bhatt et al 2013; Shubin et al 2015; Zhang et al 2015). In the present study, the SG cells cultured on the ECM matrix, Matrigel, showed organization into 3D spheroids, while 2D cultured cells formed flat spreading monolayers, consistent with previous studies (Joraku et al 2007; Pradhan et al 2009; Maria et al 2011).…”

Biomaterials-based strategies for salivary gland tissue regeneration

“…Porous membranes or scaffolds of relatively hydrophobic polymers, such as poly(vinylidene fluoride) (PVDF) or silk fibroin, are more supportive of cell growth 19 and phenotype retention 20 than flat substrates. Fibronectin-coated silk fibroin scaffolds supported the development of aggregates that resemble the secretory acini morphologically and functionally.…”