Q How can we use stem cells to build tissues and organs?
— Michael Treiman
A Dave Vereide, regenerative biology group at the Morgridge Institute for Research:
There are two major properties of a stem cell: potency and self-renewal.
By potency, we mean a cell’s ability to give rise to specialized cells. Some stem cells are more potent than others, but at the very top of the hierarchy are the so-called “pluripotent” stem cells, which can give rise to everything.
Self-renewal, on the other hand, refers to the ability of the stem cell to regenerate itself. All of us walk around with stem cells that repopulate our blood and our muscle tissue and our skin tissue. We’re in a constant state of renewal.
So how do we make tissues and organs from stem cells? The trick is to understand the signals that tell a stem cell how to give rise to all the different cell types within that tissue.
To get at that requires a lot of trial and error because there’s no manual that tells us how to go from a stem cell to particular tissue or how to go from a stem cell to a particular organ.
The biggest challenge right now is that we can push a stem cell to be a particular type of cell, but in a tissue there are multiple cells. And an organ like your heart or brain isn’t just made of one cell type; it’s made of many cell types working together.
How we structure an organ to have all that cellular diversity is still largely unknown.
Learning how to tweak the system so you get just the right ratios of different cell types that then engage together to form a really functional and useful tissue will be a key next step.