Microfluidics Based Spatial Stimulation of Stem Cells

Adult brain contains stem cells that are able to generate the brain's three major cell types—astrocytes and oligodendrocytes, which are non-neuronal cells, and neurons, or nerve cells. Radial glia are neuroepithelial stem cells that guide neural cell migration away from ventricular zones and become lineage restricted during development before they differentiate into more mature cell types in the CNS. It has been suggested that subpopulations of radial glial neural stem cells are temporally and spatially regulated during CNS development by gradients of soluble factors. During forebrain development, dorsal and ventral regions secrete different factors including bone-morphogenetic protein (BMP) and leukemia inhibitory factor (LIF), which are likely to establish gradients that modulate cell proliferation and differentiation. Microfabrication may offer advantages for studying stem cell biology because it can provide a microenvironment mimicking the stem cell niche. To further investigate the mechanism of differentiation, IGERT Trainees in the J. Zahn and M. Yarmush (BME) laboratories will fabricate and employ a microfluidic gradient generator to localize growth factors and then test in the Grumet (CDB) laboratory whether secreted factors that are present during rat forebrain development affect lineage restriction of radial glia. The device design of interest has two independent inlets, in which gradients of individual soluble factors, such as BMP or LIF, as well as combinations of these factors can be generated (Fig. 6).

Fig. 6. Microfluidic device showing cell culture chambers and the gradient generators (top).  Each device has two inlet ports and one outlet port. Neural stem cells (radial glia) after seeding in the device can experience different concentrations of growth factors (bottom).  Regions with BMP exposure caused more elongation than those with LIF exposure