Method to deliver molecules within embryonic stem cells improves differentiation

Todd McDevitt, an assistant professor in biomedical engineering at Georgia Tech, points to an aggregate of embryonic stem cells undergoing differentiation with blue-stained nuclei. He has developed a molecular delivery... Click here for more information.

Next, the researchers compared differentiation of untreated cells, cells mixed with empty microspheres, cells mixed with retinoic acid-loaded microspheres, and cells treated with soluble retinoic acid. Retinoic acid was chosen initially because it is a potent inducer of embryonic stem cell differentiation.

After ten days, approximately 90 percent of the embryoid bodies mixed with retinoic acid-loaded microspheres began to display the hollow structure signifying differentiation, compared to 6 percent of the untreated bodies, 10 percent of the bodies coated with soluble retinoic acid, and 30 percent of the bodies mixed with empty microspheres. In addition, thirty percent of the embryoid bodies mixed with retinoic acid-loaded microspheres were completely hollow in the center, compared to nearly zero percent for the other groups.

“These results suggest that if you can control the signaling by presenting molecules locally on the inside of the embryoid body from biodegradable microspheres, you can effectively change the course and synchrony of differentiation,” said McDevitt.

To examine the cells in more detail, McDevitt teamed with Georgia Tech School of Biology chair John McDonald and research scientist Nathan Bowen to conduct microarray gene expression studies to determine cell phenotype.

The results revealed enhanced expression of fibroblast growth factor 5 (FGF-5) – a marker for primitive ectoderm – in the embryoid bodies mixed with retinoic acid-loaded microspheres compared to the other treatment groups after 10 days. The researchers also confirmed increased or inhibited expression of many additional markers.

“The importance of these findings is that we’ve shown that biomaterial-based approaches to regulate stem cell microenvironments can significantly improve differentiation methods,” said McDevitt. “Our ultimate goal is to improve the efficiency of this differentiation process into specific cell types for cell replacement therapies.”