Peptide gels of fully-defined composition and mechanics for probing cell-cell and cell-matrix interactions in vitro

J.C Ashworth,J.L Thompson,J.R James,C.E Slater,S Pijuan-Galitó,K Lis-Slimak,R.J Holley,K.A Meade,A Thompson,K.P Arkill,M Tassieri,A.J Wright,G Farnie,C.L.R Merry

doi:10.1016/j.matbio.2019.06.009

J.C Ashworth, J.L Thompson + Show 12 more

Open Access

https://doi.org/10.1016/j.matbio.2019.06.009

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Abstract

Current materials used for in vitro 3D cell culture are often limited by their poor similarity to human tissue, batch-to-batch variability and complexity of composition and manufacture. Here, we present a “blank slate” culture environment based on a self-assembling peptide gel free from matrix motifs. The gel can be customised by incorporating matrix components selected to match the target tissue, with independent control of mechanical properties. Therefore the matrix components are restricted to those specifically added, or those synthesised by encapsulated cells. The flexible 3D culture platform provides full control over biochemical and physical properties, allowing the impact of biochemical composition and tissue mechanics to be separately evaluated in vitro. Here, we demonstrate that the peptide gels support the growth of a range of cells including human induced pluripotent stem cells and human cancer cell lines. Furthermore, we present proof-of-concept that the peptide gels can be used to build disease-relevant models. Controlling the peptide gelator concentration allows peptide gel stiffness to be matched to normal breast (<1 kPa) or breast tumour tissue (>1 kPa), with higher stiffness favouring the viability of breast cancer cells over normal breast cells. In parallel, the peptide gels may be modified with matrix components relevant to human breast, such as collagen I and hyaluronan. The choice and concentration of these additions affect the size, shape and organisation of breast epithelial cell structures formed in co-culture with fibroblasts. This system therefore provides a means of unravelling the individual influences of matrix, mechanical properties and cell-cell interactions in cancer and other diseases.

Highlights

In many research areas, but in cancer research and disease modelling, there is an increasing emphasis on the use of biomaterials to grow cells in 3D [1,2,3]
The first stage is to create a matrix-free precursor by peptide dissolution in water. This precursor contains no organic components other than the octapeptide gelator FEFEFKFK, the concentration of which will determine the stiffness of the final peptide gel
The peptide itself is commercially available from several suppliers, and importantly we have verified that our fabrication method is effective for peptide preparations obtained from different companies

Summary

Introduction

But in cancer research and disease modelling, there is an increasing emphasis on the use of biomaterials to grow cells in 3D [1,2,3]. It is well-understood that culturing most cells on 2D surfaces results in inferior physiological conditions affecting cell morphology, phenotype and cell-matrix interactions [4,5,6]. There is a growing body of literature focussed on the development of biomaterials as biomimetic culture platforms, to produce more tissue-realistic cell behaviour in vitro. The major hurdle still to be overcome is the provision of a system that is both highly tunable and reproducible in composition and mechanical properties

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