Organoids: Mini Organs Transforming Modern
Medicine and Research
By Alicia Ho
Edited by Margherita Sparaco
PSCs are, as the name suggests, pluripotent: they can differentiate into almost any cell type except the extra-embryonic tissues( the placenta, amniotic sac and other tissues needed for foetal development), allowing more complex structures to be built. They divide rapidly— so rapidly they can form teratomas— and need very precise conditions, because they lack a natural“ blueprint” for differentiation. ESCs come from embryos donated through IVF; iPSCs are made by reprogramming differentiated adult somatic cells back to a pluripotent state.
An organoid is a miniaturised, simplified version of an organ grown in three dimensions. It mimics the key functional and structural complexity of that organ— enough to carry out real cell functions such as nutrient absorption and cell communication. Organoids are built from stem cells that differentiate into the specialised cell types found in the organ they imitate.
Which stem cells are organoids built from?
They fall into two groups: pluripotent stem cells( PSCs)— which include embryonic stem cells( ESCs) and induced pluripotent stem cells( iPSCs)— and tissue-derived stem cells( TSCs).
TSCs are what iPSCs were before that reprogramming: taken from adult tissue and multipotent, meaning they can only form the cell types of a single tissue. They are limited in structural complexity and lack multi-tissue interactions, but because they preserve a patient’ s own mutations and genetic traits, they are well suited to personalised use. They are also easier to grow, since fewer artificial growth factors are needed.
How are organoids grown?
After ESCs are extracted from an embryo, and iPSCs and TSCs from adult cells, the next major step is growing these stem cells into organoids inside an artificial extracellular matrix( ECM). Scientists commonly use Matrigel, which mimics the real ECM found in our organs and contains various proteins( such as laminin and collagen IV) and growth factors.
CATALYST 5