ANAHEIM, Calif. - Tissue engineering shop RegeneMed has developed a 3D liver tissue surrogate for ADME/Tox testing that can offer pharmaceutical companies long-term predictive cell life and human functionality, according to a company official.
Dawn Applegate, president and CEO of RegeneMed, discussed the Carlsbad, Calif.-based company’s hepatic model, which it launched in June, at the Society for Biomolecular Sciences’ Stem Cells and Primary Cells in Drug Discovery symposium, held here this week.
The technology promises an alternative to the current industry standard, which is to isolate live human or animal cells and grow them in a monolayer culture, where they only survive for a day or two. While it takes six to eight weeks for drug toxicity to manifest itself in the body, the short survival times for these cell culture systems demand that researchers instead provide six to eight times the toxic dose in order to assess toxicity.
Applegate said that RegeneMed’s approach enables researchers to dose cells over a longer period of time in order to more closely mimic human physiology.
“What we do instead is grow a liver surrogate in the lab in the same 96-well plates that are currently used for the hepatocyte monolayer systems,” said Applegate. “We then use a chronic dose of the drug candidate because these 3D cultures can be repeatedly dosed for weeks…or even months to get a typical chronic dose response.”
Applegate said that the liver tissue surrogate can be used to assess such drug safety parameters as chronic toxicity, drug clearance and bioavailability, chronic enzyme induction over time, and drug-drug interactions.
In addition, the results are highly reproducible, she said.
“We really believe that you’ve got to have all of the cells native to the tissue together in a microenvironment, not just one type of cell,” Applegate told CBA News in an interview following her presentation. All cell types native to a particular tissue drive its function, not just what Applegate referred to as the “worker bee” cells.
If these different types of cells are put together in a 3D, interconnecting porous structure, where they can co-locate, migrate, and be associated with the neighbors that they would have in vivo, they will not only grow and divide, but also express every native extracellular matrix protein and growth factor ex vivo and therefore reform that tissue ex vivo, Applegate said.
She explained that RegeneMed uses a uniform nylon scaffold, as opposed to collagen or Matrigel, which confine cells and do not allow them to migrate and associate with those cells they would associate with in vivo.
Stromal cells are isolated from a donor liver, Applegate said. These cells will expand and bank in 2D culture.
“You than feed those cells onto the 3D scaffold and you give them about a week to start forming the tissue,” said Applegate. “At that point, the parenchymal cells are isolated from a second donor liver and fed onto the growing stromal component.”
According to Applegate, the hepatocytes and progenitor cells fill in the mesh openings of the scaffold. They will not overgrow the scaffold, the hepatocytes will not overgrow the stromal cells, and the stromal cells will not overgrow the hepatocytes, as is sometimes seen in monolayer culture, she said.
“We really believe that you’ve got to have all the cells native to the tissue together in a microenvironment, not just one type of cell.”
Applegate added that the cells will take on the structure of whatever scaffold you give them, and they behave like adult cells at this phase. As long as they are kept fed, they will stay alive and functional up to 90 days in culture with standard toxicity and metabolic function.
“We can grow these in 96-well plates or 384-well plates as well as in ADME devices,” said Applegate.
The company is also able to use cryopreserved hepatocytes that are resurrected in its 3D systems, and has found that it can measure cellular function long-term in culture while using the same cells over and over during the course of several years, said Applegate.
“We are now looking at leveraging these into drug discovery,” she said, adding that the company has been working on this technology since the late 80s, but focused on therapeutic uses.
“What we have done over the past several years is develop 96-well transwell plates, so that pharma can have seamless integration into its standard workflow,” Applegate said. She said that the company decided to use transwell plates rather than 96-well plates so that cells can get diffusion on both sides.
Applegate said RenegeMed expects that cell line vendors could also save a lot of money with this technology because it can be used to regrow cryopreserved cells, meaning that all the cells harvested from a patient would be useful, not just a certain percentage of what has been frozen.
“Plus, think about the patient,” said Applegate. If all harvested cells are useful, one does not have to feel bad about donating because some of the cells may go to waste, she explained. “I feel like I am serving the patient better, because now I can use all of their cells.”
RegeneMed was founded in 2004, and received $2 million in angel funding and an $8 million Small Business Innovation Research grant from the National Institutes of Health. Applegate said that the company received $1 million of the angel funds in 2005 and another $1 million in 2007.
Applegate said that the funds came from an organization called Tech Coast Angels, who syndicated the company to Sierra Angels, Sacramento Angels, and the Vegas Valley Angels. “If you need more than $1 million, angels tend to syndicate you,” she explained.
“VCs are not terribly interested in helping companies find drugs or companies like us who are developing better tools to help find drugs,” Applegate said when asked about the possibility of future VC funding.
It will come back, however, Applegate said. VCs are cyclical.
“On top of it, RegeneMed’s technology is cell-based,” and VCs are somewhat wary of cell-based companies, said Applegate. “Ours is a living product. It has to be distributed living, and not many people have distribution structures that can handle that. It’s a very high-margin product, but it’s also a very high-cost product.”