Growing stem cells efficiently and preventing contamination is a major stumbling block in developing them for therapeutic applications. Still these days, animal byproducts are used in Petri dishes that grow stem cells, leading to infection that may trigger an immune response once these cells are transplanted into the body. To overcome this issue, researchers at University of Washington in Seattle have developed a 3 dimensional structure to serve as a nesting site for stem cells to comfortably grow and propagate.
Zhang’s [Miqin Zhang, UW professor of materials science and engineering] cylindrical scaffold is made of chitosan, found in the shells of crustaceans, and alginate, a gelatinous substance found in algae. Chitosan and alginate have a structure similar to the matrix that surrounds cells in the body, to which cells can attach. Different processing techniques can make the scaffold out of interconnected pores of almost any size, Zhang said.
Researchers first seeded the scaffold with 500,000 embryonic stem cells, and after 21 days the scaffold was completely saturated. The cells infiltrated the structure, Zhang added, unlike other materials where cells often grow only on the surface.
To retrieve the cells, researchers immersed the scaffold in a mild solution. The structure is biodegradable and so dissolved to release the stem cells. One also could implant the stem cell-covered scaffold directly into the body.
Analysis of gene activity and testing in the lab and in mice showed that the new stem cells retained the same properties as their predecessors.
Other researcher groups are also looking for alternatives to feeder layers. The leading contenders are scaffolds coated with custom proteins designed to mimic the key properties of the animal cells in the feeder layer. Such products are expensive and difficult to produce in a consistent manner, Zhang said. The proteins also get used up in a few days and have to be replaced, making them costly and time-consuming for everyday use.
“Our scaffold is made of natural materials that are already FDA-approved for food and biomedical applications. Also, these materials are unlimited, and the cost is cheap,” she said.
Press release: 3-D scaffold provides clean, biodegradable structure for stem cell growth …
Abstract in Biomaterials: Feeder-free self-renewal of human embryonic stemnext term cells in 3D porous natural polymer scaffolds
Images: Top: The UW’s biodegradable scaffold was built as a cylinder which was then cut into dime-sized slices. Bottom: A magnified view of the scaffold shows the pores, each about a tenth of a millimeter wide, where stem cells can grow.