A new 3D method of culturing embryonic stem cells has been developed by a team of researchers from the Molecular, Cellular and Developmental Biology and Chemistry and Biochemistry departments of the University of California Santa Barbara.
The team uses near-infrared (NIR) light to control gene expression using synthetic RNA (siRNA) attached to hollow gold nanoshells in a thermoreversible hydrogel, which serves as the 3D scaffold.
NIR light penetrates up to 10cm deep and can be highly focused on specific sections of the hydrogel scaffold. The light releases the siRNA from the gold nanoshells, starting gene silencing activity. The team was able to target specific cells in the 3D scaffold and discriminate from neighboring cells using a two-photon microscope. The team demonstrate the 3D release of siRNA and gene silencing in selected cells using the novel technique.
The new technique gives the researchers ‘unprecedented’ spatiotemporal control of the entire cell, or parts of it, allowing them to differentiate stem cells along a specific gene pathway. Irradiation with light had no effect on the rate of cell growth, the technique did not cause cell damage and there was no difference in viability after irradiation.
The team is using the new technique to generate an optic cup for retinal tissue growth in vitro, although the light-patterned RNA interference technique has a myriad of applications. The researchers explained that their two-photon excitation approach could also be combined with in vivo imaging to allow it to be used for investigating developmental processes in vivo.
Co-author of the paper, Demosthenes Morales, said “One reason we’re very interested in spatiotemporal control is because these cells, when they’re growing and developing, don’t always communicate the same way,” explaining that “being able to control that communication on which cell differentiates into which cell type will help us to be able to control tissue formation.”
The study – Light-Patterned RNA Interference of 3D-Cultured Human Embryonic Stem Cells – has recently been published in the journal Advanced Materials.