Developing New Organoid Systems and the Potential Impact of the Technology, PhD
Dr. Spence earned his PhD from Miami University, USA. He Subsequently worked as a Research Fellow under Dr. James Wells at Cincinnati Children's Hospital. He is currently an Associate Professor at the University of Michigan in Ann Arbor. His lab focuses on using an understanding of developmental biology to inform development of in vitro model systems, and use of these systems to investigate tissue development and the physiology of immature tissues.
Please share a little bit about how you decided to pursue scientific research originally and the path you've taken to your research group today.
I started out as a biology major at Canisius College in Buffalo, NY, where I fell in love with research during my undergrad. I decided at that point that I would pursue science as a career and moved on to graduate school. I joined a relatively small PhD program at Miami University in Oxford, Ohio, because I really fell in love with the lab of my PhD advisor Katia del Rio-Tsonis. Her lab studies regeneration using non-traditional model systems like the newt and the axolotl; my PhD project was using chick embryos to investigate retina regeneration. The idea was that if we could unlock some of the answers in these model systems then we might gain insight into regeneration and repair in humans.
That really piqued a broad and deep interest in stem cell and regenerative biology, which ultimately catapulted me into my post-doc at Jim Wells’ lab at Cincinnati Children’s Hospital. When I joined the Wells lab, he was still mostly using model organisms to study these important fundamental questions about embryo development. So it was the questions that drove me in, but the opportunity to apply those principles to a human system and try to create human tissues in a dish was the whole package. It satisfied an ability to continue curiosity-driven research about embryonic development and also merge that with my stem cell biology and regenerative biology background.
What areas of research are you focused on now?
We’ve uncovered this idea that the tissues that we are generating in vitro, these organoids, are immature until we transplant them into mice. I think one of the outstanding issues for the whole field, not just for organoid scientists, is understanding how to continue to mature tissues in vitro. We've been able to identify some major differences in intestinal tissue since we have the ability to transplant the organoids in mice after we’ve grown them in vitro and then really look and see the differences between the mature and immature tissues. So we have some ongoing projects really trying to understand what the major drivers of these differences are in maturation in the tissue culture dish versus when you transplant the organoids into a mouse.
We are also broadly interested in using the in vitro models, without transplanting them, to understand tissue development and understand the biology of the immature tissue in a given context. For example, intestinal organoids have an immature intestinal epithelium similar to a fetal epithelium; one of the questions that we’re interested in is using organoids to model exposure of an immature tissue to microbes, as in necrotizing enterocolitis, to try and further understand the disease mechanisms.
Can you comment on some of the biggest challenges that you’ve faced in developing this system?
I think the biggest difficulty for us initially was generating the starting material, the spheroids that we embed into the 3D-matrix that then give rise to organoids. We noticed that some of our cultures would spontaneously give rise to these 3D spheres that we could use for our experiments and some of them wouldn’t. And so we spent a significant amount of time determining that the density of the starting culture conditions is really critical for the efficient differentiation all the way from start to finish. Once we were able to efficiently control the starting densities of our culture in order to control the efficiency of the downstream differentiation, the spheroids would develop much more robustly and with more reproducibility. Once we were able to take those spheroids and embed them into the 3D-matrix, and in our case we mostly used Matrigel, at that point there weren’t a lot of technical challenges. And I should highlight that it was really the growth conditions that were defined by Toshi Sato and Hans Clevers a couple of years before we published our manuscript; our work was really dependent on their huge hurdle in the field of being able to grow intestinal stem cells and intestinal crypts into 3D-structures that really facilitated our work. So I think that probably a lot of the technical limitations that we would have had were solved by the landmark paper from that group.
In your opinion, what will be the biggest advance from this work on organoids?
Oh boy, that's a tough one. I mean, personally, I just see so many different uses for these model systems. I tend to try to think about how these tools might be used in the next ten years to really further our understanding of human development and human disease. And so, I think that they may be great platforms for things like pre-clinical drug screening, but really I think the sky’s the limit in terms of the use of these different model systems. Again, I think they just need to be implemented in the correct context. I guess I don't have a clear answer of what the greatest use or implementation of these models will be but I think that there's a lot of potential there that's still untapped.
- Dye BR et al. (2016) How to Grow a Lung: Applying Principles of Developmental Biology to Generate Lung Lineages from Human Pluripotent Stem Cells. Curr Pathobiol Rep 4(2): 47–57
- Dye BR et al. (2016) A bioengineered niche promotes in vivo engraftment and maturation of pluripotent stem cell derived human lung organoids. Elife 5
- Dedhia PH et al. (2016) Organoid Models of Human Gastrointestinal Development and Disease. Gastroenterology 150(5): 1098–1112
- Aurora M & Spence JR. (2016) hPSC-derived lung and intestinal organoids as models of human fetal tissue. Dev Biol 420(2): 230–238
- Finkbeiner SR et al. (2015) Transcriptome-wide Analysis Reveals Hallmarks of Human Intestine Development and Maturation In Vitro and In Vivo. Stem cell reports 4(6): 1140–1155
- Finkbeiner SR et al. (2015) Generation of tissue-engineered small intestine using embryonic stem cell-derived human intestinal organoids. Biol Open 4(11): 1462–72
- Dye BR et al. (2015) In vitro generation of human pluripotent stem cell derived lung organoids. Elife 4
- Spence JR et al. (2011) Directed differentiation of human pluripotent stem cells into intestinal tissue in vitro. Nature 470(7332): 105–109