Liquid in a petri dish

Organoids – what on earth are they?

Organoids are new to me. I knew of them as a theoretical concept but didn’t know that they had been given a name of their own. With thanks to the Edexcel Examination Board and the publication of the scientific article for use with A Level Biology Paper 3 this year, I’ve been on a journey of discovery in the organoid world.

Tissue culture has been with us a long time. A suspension of cells in a medium that gives them the best opportunity to divide by mitosis and produce a clone, a large number of identical cells. Think of a bowl of dirty washing up water left in the sink overnight. Food scrapings from the plates and a nice, warm, kitchen. All the right conditions for bacteria to multiply and so by morning, the few original bacteria have become a thriving mass in a bacterial soup. This is tissue culture in a most primitive form.

The next step along the tissue culture pathway is the use of stem cells, undifferentiated cells that have not yet become specialised for a particular task by switching certain genes on and other off. The newly fertilised embryo is a ball of undifferentiated cells – but those cells have the ability to produce all of the tissues and organs needed to create a functioning organism. Stem cells in tissue culture can be manipulated not only to divide, but to become very specific cell types. It is this phenomenon that provides the basis of growing replacement tissue for repair or transplantation.

Organoids take the process yet another step closer to spare part surgery. An organoid is a miniature, simplified version of an organ. They are being grown in laboratories in culture, not as single cells but as three-dimensional entities with structures and characteristics of the very organs that they mimic. Growing cells in 3D allows them to create tiny structures that are able to differentiate into more than one type of cell, and so they really do represent mini organs rather than tissue. Another bonus is that diseased organoids can be grown from diseased cells, and these can be used to monitor drug interactions with a human model rather than an animal model or a cell line.

However, the ethics of organoids remain complicated. While it may be ethically acceptable to continue research on human, self generating tissue, there is a question mark hanging over the ability to differentiate embryonic structures too closely aligned to a developing human foetus.

As yet, organoids have not had much exposure outside of the scientific community. Looking at the recent literature, this is changing and organoids will be part of our everyday language.