Our first step was to show that restorative growth occurs in an organ-instrinc manner and is independent from signals or forces coming from adjacent tissues. To do this we perturbed the size of the spinal cord specifically and showed that it is able to recover. To further validate this conclusion, we wanted to test if restorative growth can also occur in vitro in neural tube organoids. In order to do this, we established a new spinal cord organoid system. This system differs from previous systems, because it is simplified (a two-dimensional layer of cells, rather than a 3D structure), it is initialized in a geometrically controlled manner, which makes it reproducible and quantifiable, and grows over time, which allows us to study growth control quantitatively. We are currently using this system to further investigate restorative growth and the underlying mechanisms.
Our approach involves a combination of in vitro and in vivo assays. We are testing the roles of specific morphogen signaling pathways both in embryos, as well as in organoids. This work is still ongoing.
In addition, we developed new experimental approaches and computational tools to study the mechanical properties of the tissue. In particular, we used very sparse labelling of individual cells and tracked how the daughter cells are distributed in space in the developing spinal cord epithelium. These experiments showed that daughter cells were more spread at early developmental stages. We developed a computational cell based model of the tissue to analyze these data. Our analysis showed that the tissue material properties change over time. Importantly, the tools that we developed can now be applied in the context of restorative growth, to understand the role of mechanical properties in controlling tissue growth.
