Stem cells are providing insight into embryo development and offer new approaches to clinical and therapeutic research.
In part this progress arises from ‘directed differentiation’ – artificially controlling the types of cells produced from stem cells.
We have developed methods for the directed differentiation of mouse and human embryonic stem cells into cells of the spinal cord and paraxial mesoderm (the tissue that generates muscle and bone that is normally found adjacent to the spinal cord).
During normal embryo development, spinal cord and paraxial mesoderm arise from a shared group of precursors known as neuromesodermal progenitors (NMPs). We found that the same combination of signals to which NMPs are exposed to in embryos can be used to generate NMPs from mouse and human pluripotent stem cells. Similar to NMPs in vivo, the in vitro derived NMPs co-express the neural factor Sox2 and the mesodermal factor Brachyury and can be guided into differentiating into either neural or paraxial mesoderm tissue.
The neural cells produced from in vitro NMPs have spinal cord but not anterior neural identity and can differentiate into spinal cord motor neurons. The data illustrate how mimicking normal embryonic development allows the generation of specific cell types from ES cells. We are taking advantage of this system to investigate NMPs.
We would like to understand how NMPs make the decision between spinal cord and mesoderm and how spinal cord identity is controlled in differentiating cells. In addition this approach provides excellent imaging opportunities to study Shh signalling and gene regulation at single cell resolution.
To complement the stem cell approaches we are developing microfluidic devices that are capable of mimicking the spatial and temporal molecular gradients found in vivo during tissue development. These devices allow the establishment and maintenance of simultaneous opposing and/or orthogonal gradients of developmental morphogens.
Initial proof of concept studies indicate that the devices are able to maintain the differentiation of ES cells for multiple days and to direct the differentiation of spatially discreet domains of motor neurons, similar to that found in the developing spinal cord.
Combining stem cell differentiation with microfluidic device technology has the potential to provide an in vitro experimental paradigm of tissue development.