Abstract
BackgroundMetastasis is a complex process which is difficult to study and model. Experimental ingenuity is therefore essential when seeking to elucidate the biological mechanisms involved.Typically, in vitro models of metastasis have been overly simplistic, lacking the characteristic elements of the tumour microenvironment, whereas in vivo models are expensive, requiring specialist resources. Here we propose a pipeline approach for the study of cell migration and colonization, two critical steps in the metastatic cascade.MethodsWe used a range of extracellular matrix derived contexts to facilitate a progressive approach to the observation and quantification of cell behaviour in 2D, 3D and at border zones between dimensions. At the simplest level, cells were set onto collagen-coated plastic or encapsulated within a collagen matrix. To enhance this, a collagen compression technique provided a stiffened, denser substrate which could be used as a 2D surface or to encapsulate cells. Decellularized tissue from the chorioallantoic membrane of the developing chicken embryo was used to provide a more structured, biologically relevant extracellular matrix-based context in which cell behaviour could then be compared with its in vivo counterpart.ResultsCell behaviour could be observed and quantified within each context using standard laboratory techniques of microscopy and immunostaining, affording the opportunity for comparison and contrast of behaviour across the whole range of contexts. In particular, the temporal constraints of the in vivo CAM were removed when cells were cultured on the decellularized CAM, allowing for much longer-term cell colonization and cell-cell interaction.ConclusionsTogether the assays within this pipeline provide the opportunity for the study of cell behaviour in a replicable way across multiple environments. The assays can be set up and analysed using easily available resources and standard laboratory equipment. We believe this offers the potential for the detailed study of cell migration and colonization of tissue, essential steps in the metastatic cascade. Also, we propose that the pipeline could be used in the wider arena of cell culture in general with the increasingly more complex contexts allowing cell behaviours and interactions to be explored in a stepwise fashion in an integrated way.
Highlights
Metastasis is a complex process which is difficult to study and model
Based on a biomaterials approach, here we propose a set of in vitro assays of increasing complexity which were used in comparison with a well characterized in vivo assay, the chicken chorioallantoic membrane (CAM) assay, for the study of cell migration and colonization in a 3D tissue context [12,13,14]
The main constituent of extracellular matrix (ECM) as a starting point, we have developed a set of assays which build on the existing assays used in the field to provide a pipeline for the comparison and contrast of cell behaviours in increasingly complex ECM based 3D environments
Summary
Metastasis is a complex process which is difficult to study and model. Experimental ingenuity is essential when seeking to elucidate the biological mechanisms involved. Metastasis is, a complex, multi-stage process which due to its temporal and unpredictable nature is difficult to study. The outward spread of cancer from a tumour occurs in several stages: cellular escape, invasion, intravasation, extravasation, seeding and colonization at distant sites [1, 2]. Both in vitro and in vivo experimental models have been used to gain further insight into metastatic mechanisms. Models of metastasis need to reflect the complexity of the tumour microenvironment, the conduits involved in the metastatic processes and the tissue architecture and features of sites of metastatic seeding and colonization. Better models will enable a more detailed understanding of the processes involved and provide improved opportunities for the testing of candidate molecules before drugs trials
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