Scientists and engineers will have have to develop ways to grow complex three-dimensional structures in large volumes and at costs that won't bankrupt health care systems before they can realize the dream of using stem cells to create replacements for worn out organs and battle damaged body parts.
Researchers are now reporting advances in these areas by using gelatin-based microparticles to deliver growth factors to specific areas of embryoid bodies, aggregates of differentiating stem cells. The localized delivery technique provides spatial control of cell differentiation within the cultures, potentially enabling the creation of complex three-dimensional tissues. The local control also dramatically reduces the amount of growth factor required, an important cost consideration for manufacturing stem cells for therapeutic applications.
The microparticle technique, which was demonstrated in pluripotent mouse embryonic cells, also offers better control over the kinetics of cell differentiation by delivering molecules that can either promote or inhibit the process. Based on research sponsored by the National Institutes of Health and the National Science Foundation, the developments were reported online July 1 in the journal Biomaterials
and were presented at the 11th Annual International Society for Stem Cell Research meeting held in Boston June 12-15, 2013 .
"By trapping these growth factors within microparticle materials first, we are concentrating the signal they provide to the stem cells," said Todd McDevitt, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "We can then put the microparticle materials physically inside the multicellular aggregate system that we use for differentiation of the stem cells. We have good evidence that this technique can work, and that we can use it to provide advantages in several different areas."
The differentiation of stem cells is largely controlled by external cues, including morphogenic growth factors, in the three-dimensional environment that surrounds the cells. Most stem cell researchers currently deliver the growth factors into liquid solutions surrounding the stem cell cultures with a goal of creating homogenous cultures of cells. Delivering the growth factors from microparticles, however, provides better control of the spatial and temporal presentation of the molecules that govern the growth and differentiation of the stem cells, potentially allowing formation of heterogeneous structures formed from different cells.