Two University researchers may have developed a new way to successfully cultivate stem cells by changing their direct environment rather than their biological properties.
Gary Smith, an associate professor in the department of obstetrics and gynecology, and Joerg Lahann, an associate professor in the chemical engineering department, recently led a team of researchers to develop a synthetic cell matrix to facilitate cell cultures and avoid contamination that could affect the function of growing stem cells.
First isolated in 1998, human embryonic stem cells have only been under the microscope for about 12 years. Smith said some aspects of hES cell growth, which make it better suited to research applications relative to mouse embryonic stem cells and human adult stem cells, remain a mystery.
“The actual requirements of the (hES) cell are not fully understood,” he said.
Smith added that he and Lahann grow the hES cells on synthetic polymer surfaces instead of the traditional gels made from ground-up animal cells or animal-derived fibroblasts, which are connective tissue cells that secrete extracellular matrices.
Smith referred to the animal-derived surfaces as “undefined” insoluble components, because the cell secretions and cell-to-cell interactions that occur among animal cells cause variability in the components of the surface.
“What (an undefined insoluble component) does is it causes … problems with not knowing exactly what is in the culture environment,” he said.
For instance, using mice skin cells to form the insoluble component can cause hES cells to take up the proteins from the mice cells, Smith said. This uptake of foreign biological matter, he added, makes it difficult to determine if apparent characteristics of hES cells are actually due to the mice cell proteins.
To avoid this type of uncertainty in the observed needs and behaviors of hES cells, Smith and Lahann are turning to artificial, or “defined,” surfaces.
“(Using a defined insoluble component) makes it much easier to test and define what are the requirements of hES cells and what actually regulates differentiation,” Smith said. “The long-term benefit is (that) removing undefined contaminates from hES cell growth is going to facilitate the ability to use hES cells in the future for clinical research.”
To test a defined insoluble component, Smith said he and his team allowed the cells to grow for seven days and then “passage” the cells to a new dish, where they grow for another seven days before repeating the process until the cultured cells cease to divide.
Smith said he and Lahann started with eight different test surfaces — three of which successfully anchored the cells. Cells from two of the three remaining cultures differentiated of their own accord, rendering the cultures useless for the purposes of hES cell research. The one test surface that the cells successfully attached to and grew on undifferentiated, Smith said, has supported cell growth for up to 40 passages.
Smith said the next step in their research, in addition to extending the growing period of the cells, is to derive their own line of hES cells. The current cells they use, he said, are all federally approved lines grown on fibroblasts — an undefined insoluble component.
Proposal 2, which was passed in November 2008 by Michigan voters, currently allows researchers to derive their own lines of hES cells under certain restrictions. Notably, the proposal mandates that the cells are created for the purpose of fertility treatment, that they are donated by the person seeking treatment and that they are either in excess or unsuitable for clinical use.
“Once we have the hES cell line that we have derived under fully-defined conditions, then we have something that has not ever been done before and then we can start testing if the cells that are derived and grown on an (animal-derived surface) are any different than the ones grown in a fully defined manner,” Smith said.
Smith stressed the importance of interdisciplinary research, saying that his research with Lahann could not have been accomplished without their combined knowledge in biology and chemical engineering.
“This is actually a perfect, perfect example of something that in my lab we could not have done alone … and something that in Lahann’s lab he could not have done alone. It really took a collaboration of different disciplines and different people and different ideas to make this work,” Smith said. “To me that’s the exciting part about it.”
Smith, Lahann and several co-authors wrote a paper on their research called “Synthetic polymer coatings for long-term growth of human embryonic stem cells,” which was published last month in the online journal Nature Biotechnology.