How to generate specific cell types for in-vitro model?
Author: Lam Lam
In ASCTN, we are all working on using cellular or animal models for studying disease mechanisms of neurodegenerative diseases and developing novel therapeutics to treat these diseases. In the previous post, Ines explained the importance of in-vitro models and how the architecture of the in-vitro models can be improved to mimic the actual human brain for drug testing. Here, I am going to explain how we can generate the basic component of an in-vitro model – i.e. the cell type we are interested in – from pluripotent stem cells, which can then be used to develop an in-vitro model.
Pluripotent stem cells are cells that are capable of self-renewal (i.e. they can replicate themselves infinitely). More importantly, they can differentiate into any other cell types - for example, neurons, blood cells, skin cells etc. - when appropriate signals are given. Cell signaling refers to the system cells use to talk to each other. It is tightly regulated during development, where it’s responsible for directing differentiation into appropriate cell types at the correct time and also in the intended location. With the understanding of cell signaling during foetal development, we can alter the signals by adding various compounds to the culture medium to mimic the microenvironment in a developing foetus, hence driving the cells to differentiate into the specific cell types we desire.
However, the cell signaling mechanism is a complicated process. Instead of a simple "on-and-off" or "all-or-nothing" system, it works as a gradient. A signaling pathway often has multiple effects, depending on the strength of the signal. Moreover, there are numerous pathways which cross talk with one another. Therefore, understanding the interactions between each pathway and finding the strength of each signal at the appropriate time is critical for driving a successful targeted differentiation.
My project is focused on developing a protocol that can efficiently drive pluripotent stem cells to differentiate into medium spiny neurons - a type of neuron that is vulnerable in Huntington’s disease. As there are too many signaling pathways involved during the various stages of brain development, testing each protocol individually with different targets will be time consuming and labour intensive. Therefore, I will be using CombiCult® technology to do a high-throughput screen for the best protocol. It is a technology which will allow us to test up to 100,000 different combinations of in parallel. Here is a video showing how CombiCult® works.
A list of compounds targeting different pathways involved during the development of the brain will be screened by CombiCult®, and the combinations of compounds that give the best outcome will be identified. It is hoped that we can use the identified protocol to generate medium spiny neurons from pluripotent stem cells, and use them as in-vitro model for studying Huntington’s disease and drug screening, or even novel cell-based therapeutics to treat the disease.