Spheroid models are the current standard in 3D liver hepatotoxicity drug testing due to their simplicity and limited cost. They also effectively mimic some aspects of cancer tumours, in particular the presence of a hypoxic core.
That same hypoxic core is however a challenge for the quantitative analysis of these models. As spheroids grow over a certain size (~300 µm), they compact in the centre resulting in a region where no nutrients or oxygen can reach. This means that reagents for imaging or biochemical assays are also unable to reach these cells resulting in a loss of information or requiring the samples to be lysed thus losing three-dimensional information. As the spheroid grows, the hypoxic core also expands making assessment of toxicity of drugs difficult, especially over time, as large amounts of necrosis and apoptosis are already present.
Growing cells on porous scaffolds offer a potential solution to these problems. We compare one type of scaffold (randomly orientated electrospun Mimetix® Poly-L-lactic acid) with spheroids. The 4 µm diameter fibres create pore sizes of 15-30 µm giving the scaffold an overall porosity of 80%, allowing nutrients, reagents and gases better penetration to the cells in 3D. These scaffolds should produce healthier and more informative models whilst being able to grow for longer periods without the formation of extensive hypoxic or necrotic regions.
Studying the levels of hypoxia and apoptosis across these two models along with functional readouts, including albumin production and viability, will allow us a better evaluation of the two different cultures and which, if any, enables better predictivity of the toxicity of drugs and other compounds.