Having demonstrated that tumor microtissues can be created and assayed in high-throughput fashion, Dr. Kelm’s team is now working toward additional scaffold-free models for the four main organs of toxicology research: brain, heart, kidney, and liver. In each case, models will be considered valid if they can perform tissue-specific functions.
For tumors, these functions include expression of cell-surface receptors and formation of extracellular matrix (ECM), said Dr. Kelm.
“For the liver, it’s the metabolic capacity and detoxification capacity of the hepatocytes, as demonstrated for InSphero’s recently launched rat and human liver microtissue models. Similarly, for the kidney cells, you would look primarily at the transporters of the epithelial cells. The heart is one of the easiest tissues to assess—you look at the contraction of the tissue over time.”
Stefan Przyborski, Ph.D., CSO of Reinnervate, addressed the topic of scaffolds for 3D cultures. His research, like that of Dr. Kelm, grew out of concerns that cells grown as a monolayer did not behave like cells in vivo. Not only do these cells become unnaturally elongated and flattened, they are under stress and have limited potential for cell-cell interactions.
Reinnervate aims to facilitate growth of cultures in 3D with a scaffolding material that it calls alvetex®. Alvetex is made from polystyrene, as is 2D cell culture plasticware, but comes as a highly porous 200-micron-thick membrane into which cells can grow and maintain their natural 3D structure.
“Alvetex polystyrene scaffold simply provides cells with a support structure that allows them to move inside and to continue to grow, while not allowing them to flatten out, as would happen in a traditional 2D culture setting,” according to Dr. Przyborski.
“Many cells find the alvetex scaffold environment very suitable, and start to lay down their own ECM proteins as they would in vivo. For some cell types, like primary hepatocytes, there may need to be an ECM coating on the alvetex scaffold to help establish the 3D culture.”