When Engineering Meets Biology: Taking 3D Cell Culture to the Next Level

3D bioprinting is a revolutionary technique, combining the principles of 3D printing with cell culture. A key benefit of the technique is the ability to reproduce some unique features found in the geometry of natural tissues, along with the cell-cell relationships that drive function. One application of this is to create physiologically relevant cell models for in vitro drug testing, however, it also has the potential for the generation of complex organs, which could be used for in vivo implantation, sparking significant interest in the topic.

Originating from the conceptual merging of research performed by Professor Gabor Forgacs, University of Missouri, and Dr. Thomas Boland, Clemson University, a pioneering early-stage medical research company - Organovo - was born, which set out to develop a viable 3D fabrication technology. Currently running the research and technology development efforts is Sharon Presnell, Chief Scientific Officer of Organovo, and also the president of subsidiary company Samsara in her ‘not-so-spare time’. In this interview, Sharon explains some of the unique features and applications of the technology, as well as how Transwell^® permeable supports are making her groundbreaking work possible.

SS: What inspired you to work in tissue engineering?

SP: I like things that are multidisciplinary. My first job in industry was with a very engineering-heavy company with a lot of polymer chemistry, media formulation, and that type of thing. I was a pure biologist when I walked in the door and then my eyes were opened to all the chemistry, physics, and other elements that go into the products that I was using every day - it was an awakening of sorts. As a result, everything I’ve done since has been an intersection of engineering, chemistry, biology, even statistics, and designing things a little bit more mathematically than most card-carrying biologists would care to do. In the field of tissue engineering, you can no longer achieve the real game changing advances by only working in one area. We’ve had to develop some really challenging applications and, in doing so, it created the pressure to evolve the platform to address the unknown needs on the biology side, versus the engineering side. As a result, there’s been a lovely co-evolution, that has enabled us to develop a balanced approach to new tissue design and helped us advance our hardware and software to match the applications.

SS: How does the technology work?

SP: We typically take primary human cells and formulate them into bio-inks, some of which may be 100% cellular. Other bio-inks may have components added in to them to provide stiffness or other favorable attributes. When we are working with biomaterials, we aim to use fugitive biomaterial that will disappear quickly after printing to encourage the cell-cell relationship versus the cell-material relationships, which is one of the fundamental philosophies of our platform. Typically, we work with mediums that are at least 30% cellular, all the way up to 100% cellular, even at the time of their printing, which is an important part of our platform.

The printer itself, the software, and all the drivers themselves are all proprietary systems developed in-house. For any of the tissues that we make, we often use at least two or three different materials laid down independently, which gives us a lot of flexibility in the number of components and architectures that we can make. This allows for patterning of different cells types in all three directions — x, y and z — and that’s the unique advantage of bioprinting over other typical 3D cell culture strategies that use scaffolds or hydrogels. We can print a full plate of tissue, such as liver, in a 24-well Transwell insert within 60 minutes, so the printing process is a relatively fast and efficient procedure.

SS: How are Transwell permeable supports from Corning Life Sciences helping your work?

SP: They are essential! It is a logistical nightmare to think that you could have architected tissues, with all the geometry built into them, just floating around in a media bath. That is why we print the tissue onto Transwell permeable supports, it enables us to anchor the tissue. We run complex studies that span as long as a month at a time, adding various compounds and performing low-dose and long-term exposure protocols, so it would be terrible if we lost our orientation of the tissues. Corning has got a good repertoire of products with diverse types of surfaces, pore sizes, and coatings, giving us a range of options to pick from, which is ideal because not all tissues are created equally. An advantage of the Transwell insert is that the tissue can be fed from all directions thanks to the membrane’s pores. We’re making things that are pretty big by in vitro standards and so it’s important for them to have nutrient access from the bottom as well as the top. Our work would simply not be possible without the Transwell permeable supports. From our very first experiments, we have been working with Transwell membranes and I don’t anticipate that changing.

SS: How important is collaboration?

SP: We’re still a small company so there are a lot of things we’re interested in, but the only thing we’ve really talked about publicly is the liver. Collaboration is a really nice way to branch out our expertise on the R&D side. When we’re doing the exploratory work, it’s always very helpful to have people with a very deep knowledge of what we are trying to look at.

We have a very nice collaborative relationship with Professor Melissa Little from the Murdoch Children’s Research Institute in Australia, who has one of our bioprinting platforms in her lab. We have been working with her for a couple of years now and have made some real progress in the area of kidney generation. We also have a great relationship with the National Eye Institute looking at the tissue at the back of the eye and so it’s a way for us to explore different areas without going too deep in our own R&D for a company of our size.

We have several versions of our printing platforms, which we may offer to researchers, depending on their kind of application. We will place the instrument, providing them with the training and support they need to be successful in their application and if they develop new technologies or applications, we have the option to bring them back in-house for further development and commercialization.

Corning has also been great to work with in terms of flexibility and helping attain our special needs. We are currently collaborating with our partners at Corning to develop a Transwell tray to improve ease-of-use and streamline our tissue manufacturing process. It has been a pleasure to work so productively and collaboratively with the team at Corning. It’s always good to have partners like that.

SS: What do you see for the future of your research?

SP: Currently, we’re focusing on developing really robust applications around the tissues we make, so, with the example of liver, we have a pretty good handle on what that tissue can provide in the way of toxicology testing. We have shown that we can take these tissues and perturb them in certain types of ways, causing them to develop biomarkers and histological features that are aligned with certain disease states, such as fibrosis.

Where I would love to see us progress to, as a field, is developing more ways to get information out of the 3D systems that are efficient. By broadening our understanding, we can find out how to make the tissue more like a natural model tissue. Another advancement that would take our tissues to the next level of functionality would be the development of fluid and flow systems around the tissues. This would help us add a layer of physiological relevance to our tissues, allowing them a way to connect with each other. I think it would be wildly cool to have a liver and kidney that could talk to each other!