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Introduction: Bioengineered 3D cancer models allow the deconstruction of the tumour microenvironment in vitro to recreate the dynamic interactions between its extracellular and intracellular components. These bioengineered systems strongly rely on Matrigel, an undefined animal-derived matrix, to support the growth of cancer spheroids and organoids [1]. Despite its wide usage, Matrigel has poor mechanical properties and a high batch-to-batch variation, which do not capture the biomechanics of solid tumours and limit experimental reproducibility. Nanocellulose is a low-cost, sustainable and biocompatible alternative biomaterial with promising applications as hydrogel and 3D gastrointestinal organoid models [2]. In this study, collagen-nanocellulose hydrogels are used as a defined matrix of controllable stiffness to mimic elements of pancreatic tumour tissues and promote the formation of cancer spheroids.
Methodology: Nanocellulose hydrogels were synthesized by TEMPO-periodate mediated oxidation of Eucalyptus Kraft pulp suspensions and blended with bovine type I collagen solution [3]. Human pancreatic cancer cells (e.g. PANC-1, MIA PaCa-2) together with cancer-associated fibroblasts and myeloid cells were grown encapsulated in collagen-nanocellulose hydrogels for 14 days. Triple cultures were treated with the anti-cancer compound triptolide and the chemotherapeutics gemcitabine and paclitaxel. Metabolic activity and matrix stiffness were measured by Prestoblue assays and rheology.
Results: Blending of 0.2% type I collagen fibrils with 0.1% and 0.2% cellulose nanofibres formed a matrix of controllable stiffness, with a Young’s modulus ranging from 647 ± 69 to 1,189 ± 234 Pa. Pancreatic cancer cells formed spheroids of 90 ± 30 µm diameter. Cell-containing matrices reached a Young’s modulus of 3,303 ± 226 Pa, which resembles the lower profile of pancreatic cancer tissues [4]. Treatment with triptolide, gemcitabine and paclitaxel reduced the cell viability of triple cultures by 45 ± 2%. The exposure to all three drugs combined reduced the Young's modulus of the MIA PaCa-2 triple cultures by 42 ± 2%, whereas the stiffness of those containing PANC-1 cells decreased only by 8 ± 3%
Conclusion: The mechanical properties of collagen-nanocellulose matrices are controlled by varying the concentration of cellulose nanofibres. The incorporation of pancreatic cancer and stromal cells into the biomimetic hydrogels demonstrates the importance of the cellular elements for matrix stiffening. Drug treatments modulate the mechanical properties of this 3D cancer model, resulting in differential cell responses. Collagen-nanocellulose stands as an alternative matrix to Matrigel to recreate the tumour microenvironment and support the growth of cancer spheroids, as well as to screen novel or improved treatments.
References:
[1] Tomás-Bort E, Kieler M, Sharma S, et al. 3D approaches to model the tumor microenvironment of pancreatic cancer. Theranostics. 2020 10:5074–89.
[2] Curvello R, Kerr G, Micati DJ, et al. Engineered Plant-Based Nanocellulose Hydrogel for Small Intestinal Organoid Growth. Adv Sci. 2020 Nov 20;8(1):2002135.
[3] Curvello R, Kast V, Abuwarwar MH, Fletcher AL, Garnier G, Loessner D. 3D Collagen-Nanocellulose Matrices Model the Tumour Microenvironment of Pancreatic Cancer. Front Digit Health. 2021 Jul 26;3:704584.
[4] Rubiano A, Delitto D, Han S, et al. Viscoelastic properties of human pancreatic tumors and in vitro constructs to mimic mechanical properties. Acta Biomater. (2018) 67:331-340.
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