Method to deliver molecules within embryonic stem cells improves diffe...(chanism of presentation. The researc...)

The research team which also includes graduate students Richard Carpenedo and Andrs Bratt-Leal and undergraduate students Ross Marklein and Scott Seaman fabricated biodegradable polymer microspheres that could contain growth factors, proteins or other small molecules.

McDevitts team tested the impact of the poly(lactic-co-glycolic acid) (PLGA) microspheres on embryonic stem cell differentiation under different conditions by varying the microsphere-to-cell ratio and speed at which the aggregate cells were mixed with the microspheres. They also included a fluorescent dye in the microspheres so the degree of incorporation of the microspheres within the embryoid bodies could be assessed using fluorescent microscopy and spectroscopy.

The results revealed that the microspheres were incorporated into embryoid bodies under a variety of mixing conditions, but that slower rotary speeds and higher microsphere-to-cell ratios resulted in a greater degree of incorporation.

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 in
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