CONCEPT
Synthesis of different approaches makes something unique.
The Challenge: To reconstruct the internal human body environment
We all began from a single fertilized egg, which grows to form the various organs that make up the human body, each with their own unique morphological patterns such as the tree-like branching patterns in the lungs and kidneys, or the finger-like villi in the intestines. Yet, despite their complex morphological patterns, the same pattern for each organ is reproduced in every healthy individual. This reproducibility is not solely due to the regulation of cell behaviour by genetic factors. Cells are also able to collectively communicate with each other and with their surroundings to create highly specific niches that contribute to the structure and function of each organ. Therefore, it is also necessary for us to clarify and understand the cell-cell and cell-environment communication, as well as the micro-environmental criteria that allow cells to flourish, so that we can apply various technology to design, control, and mimic these conditions to recreate complex organs outside of the body in the lab.
In our lab, we combine engineering, biology, and information technology to pursue our aim of establishing methodologies that enable us to control how cells grow, by 1) constructing an experimental platform that enables us to measure and control cellular microenvironment spatiotemporally, 2) mathematically expressing and understanding cellular self-organisation, and 3) tailoring the optimal culture conditions for each cell type based on feedback from the mathematical simulation.
Experimental Platform for Spatio-temporal Controlling and Sensing Cell Culture Environment
In the developmental process, communication between cells gives rise to the left-right, head-tail (anterior-posterior), and back-front (dorsal-ventral) axes of the body plan, which then dictate the direction of further development. In contrast, current cell culture methods are carried out by manual pipetting, and it is difficult for cells to form localised niches because the morphological factors in the medium are spread uniformly around the cells, giving them the same growth cues from all directions. To address this issue, we are constructing an experimental platform that will allow us to dynamically manipulate the three-dimensional (3D) culture space, by employing engineering methods such as photolithography, bio-printing, and microfluidic chips to control the localisation of cells and extracellular matrix (ECM) in 3D, as well as the concentration gradient of morphogenic factors.
In addition to controlling the culture microenvironment, we also need a way to measure the experimental results. Imaging, especially time-lapse imaging, can be used to glean a lot of information, such as tracking cell movement or changes in substrate viscosity. However, imaging millimetre-sized organoids in 3D is not easy, even with expensive microscopes such as two-photon or light sheet technology. To overcome this, we are aiming to develop a multi-scale measurement technology by taking the approach of expanding the capabilities of the culture device rather than that of the microscopy system itself. We had previously developed a culture cube device that enables 3D tissue samples to be imaged from multiple directions. As the fragile 3D tissue suspended in soft ECM substrate is contained within a polycarbonate cube frame with relatively rigid agarose gel walls, the samples can be safely transported and rotated without worrying about damaging the sample inside. By rotating and scanning the sample from multiple directions, high resolution imaging can be achieved even with low magnification lens.
Another advantage of the easy handling ability of the cube device is that multiple tissue samples can be cultured separately in individual cubes before integrating them together in microfluidic chips on demand, thus taking away the difficulties and stresses of culturing and managing different cell types in the same chip. The cube itself is a very simple device, but it can dramatically simplify and ease the handling of organoids, and we expect to expand its functions in combination with other technologies.
Analysing Self-organized Formation Mechanism from Cells to Tissue Pattern
When cells are cultured under homogeneous conditions in a dish, it is difficult to recognize the underlying rules governing cell behaviour because even small variations in the conditions of a cell’s vicinity (for example, distance between cells) can lead to differences in cell state and behaviour. This variation is exacerbated/greatly increased during the growth phase of a population of cells, which leads to major deterioration of the reproducibility of results. However, we believe that this variation can be suppressed by controlling the culture environment, and by systematically introducing perturbations to the culture environment, we can unravel the rules governing cell behaviour. For example, if a population of bronchial epithelial cells are seeded in a triangular shape in a dish under specific conditions, the cells will always initially move toward the apex of the triangle; on the other hand, if seeded in a circular shape, the cell population will rotate in the circle as a whole. This means that the direction of cell movement changes depending on the boundary conditions of the cell population. Then, what are the changes due to modifications in boundary conditions that affect cell behaviour? By pursuing these questions, we can understand the rules governing cellular behaviour in more detail.
