Cell therapies for a range of serious conditions, including heart attacks, diabetes, and traumatic injuries, will be accelerated by research at Worcester Polytechnic Institute (WPI) that yielded a newly patented method of converting human skin cells into engines of wound healing and tissue regeneration.
The novel method, developed by WPI faculty members Raymond Page, PhD, professor of practice in biomedical engineering, and Tanja Dominko, PhD, DVM, associate professor of biology and biotechnology, is described in U.S. Patent number 9,290,740, titled "Use of basic fibroblast growth factor in the de-differentiation of animal connective tissue cells," which was issued on March 22, 2016. The technology enables adult human connective tissue fibroblasts (cells from skin or other tissues), which were previously thought to have a very limited lifespan outside of the body, to be cultured and replicated for long periods. It further causes those cells to express genes and proteins typically associated with stem cells, thereby demonstrating that the cells are in a less differentiated state. Notably, this technology works without inserting viruses or foreign genes into the cells.
"This method is already being adopted by some groups working in tissue regeneration and we look forward to seeing it used widely by companies and research teams developing cell therapies and cell- and tissue-based assays for many indications," Page said.
Inspired by the ability of many amphibians to regenerate limbs after traumatic injury, Page and Dominko study the molecular processes of embryonic development and cell differentiation to see if human cells can be coaxed to regenerate damaged tissues. "Our cells have the memory encoded in their DNA of how to create every tissue in the body," Dominko notes. "But unlike amphibians, humans and other mammals have lost the ability to regenerate as adults. Instead, we heal injuries with scar formation."
One of the most active areas of research and clinical development today, regenerative medicine seeks to reprogram cells to repair the body. Examples of regenerative development projects now under way around the world include inducing skin cells to become contractile cardiac cells to treat heart attack patients; establishing new insulin-producing beta cells to treat diabetes; and growing nerve cells and spinal cord tissues to reverse paralysis.
Early on, the field focused on embryonic stem cells because they are pluripotent, meaning they can grow into all of the tissues of an adult organism. That work yielded important basic science knowledge and remains a relevant area of study, but the consensus is that embryonic stem cells are not a suitable platform for clinical therapies. Focus has since shifted to reprograming adult cells, like skin cells, to a more pluripotent state. Called induced pluripotent stem cells (iPS), they were first created in 2007 by Shinya Yamanaka's team at Kyoto University in Japan, which inserted extra copies of four known stem cell genes into human skin cells. (Yamanaka shared the 2012 Nobel Prize in Physiology or Medicine for this work.)
While not limited by the ethical questions associated with embryonic stem cell research, iPS cells have significant clinical barriers, including the use of viruses to carry extra genes into the cells and the potential for the cells to be rejected by a patient's immune system or to grow out of control and cause tumors. The work by Dominko and Page takes a different approach by making cells "regeneration-competent" without adding genes or viruses. Their process cultures adult human skin cells in a low-oxygen environment with a naturally occurring protein called fibroblast growth factor 2 (FGF2). This method turns on stem cell genes OCT4, SOX2, and NANOG, which are already present in the skin cells, though in a dormant state, and enables the cells to multiply in a less differentiated state, similar to a stem-like progenitor cell. Dominko and Page first reported their method, and supporting data, in 2009 in the paper "Induction of Stem Cell Gene Expression in Adult Human Fibroblasts without Transgenes," published by the journal Cloning and Stem Cells. (Cloning, Stem Cells. 2009 Jul 21.)
"The standard approach then, and even today in many labs, is to culture cells in atmospheric oxygen, but that actually creates tremendous stress on the cells and changes how they react," Page said. "In our bodies, these cells are exposed to a much lower concentration of oxygen. So what we're doing is just creating a more natural environment for these cells, and that makes a major difference."
Furthermore, the newly patented culture method yields an exponentially larger number of regeneration-competent cells than was possible using previous culture systems. For example, with slight modifications, the team successfully applied this system to adult human skeletal muscle tissue, culturing cells in large numbers without losing their potential to differentiate into contracting skeletal muscle, thus maintaining regeneration competence. With previous culture methods, muscle-derived cells lose nearly all of their ability to become contractile cells after 20 or more- generations. With the method developed by Page and Dominko, however, cells from similar tissue can maintain regeneration competence for 70 generations or more. That increases the yield of regeneration-competent cells a trillion-fold over a typical cell culture process.
"The idea is to take a patient's own cells, and grow them under these conditions producing large numbers while maintaining regeneration competence, then return them to that patient as a therapy," Dominko said. "To make cell therapy a realistic clinical treatment, you need a large number of cells in a reasonable time frame, so increasing the yield from cell culture is vital."
Worcester Polytechnic Institute