Cells in three dimensions interact with neighboring cells through chemical messaging, and reprise physiological events much more faithfully. 3D cell culture has advanced partly in the form of 3D suspended cultures – spheroids and organoids. With its growing popularity, the terms “spheroid” and “organoid” have been used interchangeably; however, the differences between these culture types are significant.
Spheroids and organoids both contain multiple cells, typically suspended within a droplet or microwell. Spheroids are simple clusters of broad-ranging cells collected and cultured from various tissues, for example, from an organ or, by way of a biopsy, from a diseased tissue or tumor. Spheroids contain a representative sampling of the tissue’s cell types, usually without selection or curation for specific cells. Sometimes the sample contains one cell type, sometimes more than one. Spheroids are known for being easier to work with, as they do not require physical scaffolding to form. This, of course, can have its downsides. Spheroids are simpler models that do not self-organize or have polarity and are thus not always representative of the more complex in vivo environment.
Organoids are complex clusters of organ-specific cells designed to mimic the original tissue such as the skin, stomach, liver, or bladder. Unlike spheroids formed from tissue samples containing any number and type of mature cells, organoids arise from tissue-specific stem cells, or progenitor cells, harvested from various organs, such as the brain or liver. Organoids can also be produced from induced pluripotent stem cells. Once provided with an appropriate extracellular matrix and treated with biochemical stimuli (specific for the eventual target cells and the tissue of interest), these progenitor cells expand, differentiate, and self-assemble into microscopic cultures that recapitulate one or more critical aspects of the original tissue.
Conventional 2D cell culture lacks in structure, function, dimensionality, cellular diversity, and cell-cell interactions making living tissue unique. Conducted in petri dishes, such preclinical strategies are unable to replicate the in vivo conditions 3D cell culture provides. With further research, this emerging technology has the potential to mitigate the losses, fiscal or otherwise, brought upon pharmaceutical companies due to drug development failures and their respective causes.
