Mucin-coating technologies for protection and reduced aggregation of cellular production systems.

Optimization of host-cell production systems with improved yield and production reliability is desired to meet the increasing demand for biologics with complex posttranslational modifications. Aggregation of suspension-adapted mammalian cells remains a significant problem that can limit the cellular density and per volume yield of bioreactors. Here, we propose a genetically encoded technology that directs the synthesis of antiadhesive and protective coatings on the cellular surface. Inspired by the natural ability of mucin glycoproteins to resist cellular adhesion and hydrate and protect cell and tissue surfaces, we genetically encode new cell-surface coatings through the fusion of engineered mucin domains to synthetic transmembrane anchors. Combined with appropriate expression systems, the mucin-coating technology directs the assembly of thick, highly hydrated barriers to strongly mitigate cell aggregation and protect cells in suspension against fluid shear stresses. The coating technology is demonstrated on suspension-adapted human 293-F cells, which resist clumping even in media formulations that otherwise would induce extreme cell aggregation and show improved performance over a commercially available anticlumping agent. The stable biopolymer coatings do not show deleterious effects on cell proliferation rate, efficiency of transient transfection with complementary DNAs, or recombinant protein expression. Overall, our mucin-coating technology and engineered cell lines have the potential to improve the single-cell growth and viability of suspended cells in bioreactors.

Stable recombinant production of codon-scrambled lubricin and mucin in human cells.

Widespread therapeutic and commercial interest in recombinant mucin technology has emerged due to the unique ability of mucin glycoproteins to hydrate, protect, and lubricate biological surfaces. However, recombinant production of the large, highly repetitive domains that are characteristic of mucins remains a challenge in biomanufacturing likely due, at least in part, to the inherent instability of DNA repeats in the cellular genome. To overcome this challenge, we exploit codon redundancy to encode desired mucin polypeptides with minimal nucleotide repetition. The codon-scrambling strategy was applied to generate synonymous genes, or "synDNAs," for two mucins of commercial interest: lubricin and mucin 1. Stable, long-term recombinant production in suspension-adapted human 293-F cells was demonstrated for the synonymous lubricin complementary DNA (cDNA), which we refer to as SynLubricin. Under optimal conditions, a 293-F subpopulation produced recombinant SynLubricin at more than 200 mg/L of media and was stable throughout 2 months of continuous culture. Functionality tests confirmed that the recombinant lubricin could effectively inhibit cell adhesion and lubricate cartilage explants. Together, our work provides a viable workflow for cDNA design and stable mucin production in mammalian host production systems.

Genetically Encoded Toolbox for Glycocalyx Engineering: Tunable Control of Cell Adhesion, Survival, and Cancer Cell Behaviors.

The glycocalyx is a coating of protein and sugar on the surface of all living cells. Dramatic perturbations to the composition and structure of the glycocalyx are frequently observed in aggressive cancers. However, tools to experimentally mimic and model the cancer-specific glycocalyx remain limited. Here, we develop a genetically encoded toolkit to engineer the chemical and physical structure of the cellular glycocalyx. By manipulating the glycocalyx structure, we are able to switch the adhesive state of cells from strongly adherent to fully detached. Surprisingly, we find that a thick and dense glycocalyx with high O-glycan content promotes cell survival even in a suspended state, characteristic of circulating tumor cells during metastatic dissemination. Our data suggest that glycocalyx-mediated survival is largely independent of receptor tyrosine kinase and mitogen activated kinase signaling. While anchorage is still required for proliferation, we find that cells with a thick glycocalyx can dynamically attach to a matrix scaffold, undergo cellular division, and quickly disassociate again into a suspended state. Together, our technology provides a needed toolkit for engineering the glycocalyx in glycobiology and cancer research.