Tuning Hydrogel Properties to Promote the Assembly of Salivary Gland Spheroids in 3D

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• 作者：Tugba Ozdemir ; Eric W. Fowler ; Shuang Liu ; Daniel A. Harrington ; Robert L. Witt ; Mary C. Farach-Carson ; Swati Pradhan-Bhatt ; Xinqiao Jia
• 刊名：ACS Biomaterials Science & Engineering
• 出版年：2016
• 出版时间：December 12, 2016
• 年：2016
• 卷：2
• 期：12
• 页码：2217-2230
• 全文大小：928K
• ISSN：2373-9878

文摘

Current treatments for chronic xerostomia, or “dry mouth”, do not offer long-term therapeutic benefits for head and neck cancer survivors previously treated with curative radiation. Toward the goal of creating tissue-engineered constructs for the restoration of salivary gland functions, we developed new hyaluronic acid (HA)-based hydrogels using thiolated HA (HA-SH) and acrylated HA (HA-AES) with a significant molecular weight mismatch. Four hydrogel formulations with varying HA concentration (1–2.4 wt %), thiol/acrylate ratios (2/1 to 36/1) and elastic moduli (G′: 35 to 1897 Pa, 2 h post-mixing) were investigated. In our system, the thiol/acrylate reaction was initiated rapidly upon mixing of HA-SH/HA-AES to establish thioether cross-links with neighboring ester groups, and spontaneous sulfhydryl oxidation occurred slowly over several days to install a secondary network. The concurrent reactions cooperatively create a cell-permissive network to allow for cell expansion and aggregation. Multicellular spheroids formed readily from a robust ductal epithelial cell line (Madin-Darby Canine Kidney, MDCK cells) in all hydrogel formulations investigated. Primary salivary human stem/progenitor cells (hS/PCs), on the other hand, are sensitive to the synthetic extracellular environment, and organized acini-like structures with an average diameter of 50 μm were obtained only in gels with G′ ≤ 216 Pa and a thiol/acrylate ratio ≥18. The spheroid size and size distribution were dependent on the HA content in the hydrogel. Cells in hS/PC spheroids formed tight junctions (occludin), remained viable and proliferative, secreted structural proteins (collagen IV and laminin) found in the basement membrane, and maintained key stem/progenitor markers. We conclude that incorporation of time-dependent, dynamic features into a covalently cross-linked HA network produces an adaptable hydrogel framework that promotes hS/PC assembly and supports early aspects of salivary morphogenesis, key to the reconstitution of a fully functional implantable salivary gland.