Kukla, D. | Search bioRxiv

bioRxiv2020

Primary Human Hepatocytes Maintain Long-term Functions in Porous Silk Scaffolds Containing Extracellular Matrix Proteins

The shortage of donor organs for transplantation has prompted the development of alternative implantable human liver tissues; however, the need for a clinically viable liver tissue that can be fabricated using physiologically-relevant primary human hepatocytes (PHHs) is unmet. Purified silk proteins provide desirable features for generating implantable tissues, such as sustainable sourcing from insects/arachnids, biocompatibility, tunable mechanical properties and degradation rates, and low immunogenicity upon implantation; however, the utility of such scaffolds to generate human liver tissues using PHHs remains unclear. Here, we show that the incorporation of type I collagen during the fabrication and/or autoclaving of silk scaffolds was necessary to enable robust PHH attachment/function. Scaffolds with small pores (73 +/- 25 {micro}m) promoted higher PHH functions than large pores (235 +/- 84 {micro}m). Further incorporation of growth-arrested 3T3-J2 fibroblasts into scaffolds enhanced PHH functions up to 5-fold for 5 months in culture, an unprecedented longevity, and functions were better retained than 2D configurations. Lastly, encapsulating PHHs within Matrigel while housed in the silk/collagen scaffold led to higher functions than Matrigel or silk/collagen alone. In conclusion, porous silk scaffolds are useful for generating long-term PHH +/- fibroblast tissues which may ultimately find applications in regenerative medicine and drug development.

bioengineering↗

bioRxiv2019

Microscale Collagen and Fibroblast Interactions Enhance Primary Human Hepatocyte Functions in 3-Dimensional Models

Human liver models that are 3-dimensional (3D) in architecture are proving to be indispensable for diverse applications, including compound metabolism and toxicity screening during preclinical drug development, to model human liver diseases for the discovery of novel therapeutics, and for cell-based therapies in the clinic; however, further development of such models is needed to maintain high levels of primary human hepatocyte (PHH) functions for weeks to months in vitro. Therefore, here we determined how microscale 3D collagen-I presentation and fibroblast interaction could affect the long-term functions of PHHs. High-throughput droplet microfluidics was utilized to rapidly generate reproducibly-sized (~300 m diameter) microtissues containing PHHs encapsulated in collagen-I +/- supportive fibroblasts, namely 3T3-J2 murine embryonic fibroblasts or primary human hepatic stellate cells (HSCs); self-assembled spheroids and bulk collagen gels (macrogels) containing PHHs served as gold-standard controls. Hepatic functions (e.g. albumin and cytochrome-P450 or CYP activities) and gene expression were subsequently measured for up to 6 weeks. We found that collagen-based 3D microtissues rescued PHH functions within static multi-well plates at 2- to 30-fold higher levels than self-assembled spheroids or macrogels. Further coating of PHH microtissues with 3T3-J2s led to higher hepatic functions than when the two cell types were either coencapsulated together or when HSCs were used for the coating instead. Additionally, the 3T3-J2-coated PHH microtissues displayed 6+ weeks of relatively stable hepatic gene expression and function at levels similar to freshly thawed PHHs. Lastly, microtissues responded in a clinically-relevant manner to drug-mediated CYP induction or hepatotoxicity. In conclusion, fibroblast-coated collagen microtissues containing PHHs display hepatic functions for 6+ weeks without any fluid perfusion at higher levels than spheroids and macrogels, and such microtissues can be used to assess drug-mediated CYP induction and hepatotoxicity. Ultimately, microtissues may find broader utility for modeling liver diseases and as building blocks for cell-based therapies.

bioengineering↗