For a long time, shaping living matter has been one of the great challenges of science. Not because there is a lack of tools, but because biological tissues are not passive materials: they grow, they reorganize, they generate their own forces. Trying to shape them is, in a way, negotiating with something that has its own dynamics.
Now, an international team led by the Institute of Bioengineering of Catalonia, together with the Universitat Politècnica de Catalunya, the International Center for Numerical Methods in Engineering (CIMNE) and the European Molecular Biology Laboratory, has taken a step that until recently seemed closer to science fiction than to engineering: creating living tissues capable of changing shape in a programmed manner. The advance, published in Science, It demonstrates something fundamental: it is not necessary to sculpt a fabric from the outside. It is enough to organize it from within.
The key lies in a seemingly simple idea: controlling the orientation of cells. But that simplicity is deceptive. In biological tissues, cells are not arranged randomly. Many of them, especially the elongated ones, tend to align like fibers in a fabric. This behavior is known as nematic order, a concept borrowed from materials physics. However, that order is never perfect. Sometimes it breaks at specific points, generating what scientists call topological defects, small regions where the alignment is disorganized. Far from being minor imperfections, these defects act as centers of force: places where the tissue pushes, contracts or folds.
That’s where innovation comes in. The team managed to not only observe these defects, but also decide where they appear. “The key is that we can decide where these defects will be and, therefore, where the forces will be generated within the tissue.”explains Pau Guillamat, leader of the study.
To achieve this, the scientists designed surfaces with chemical micropatterns, as if drawing an almost invisible map. They used proteins that attract cells to draw lines on which they adhere, surrounded by areas where they cannot attach. The result is that the cells align themselves following that pattern, as if they obeyed a “choreography.”. And that choreography matters. Because, as Guillamat summarizes, “the orientation of the cells controls the forces, and the forces can control the generation of a three-dimensional shape.”
The decisive experiment came later. As long as the tissue remains attached to the surface, those internal forces are contained, as if trapped. But when Guillamat’s team frees him (that is, when they take him off) something unexpected and, at the same time, deeply logical happens: the tissue deforms. It folds, contracts, takes on a new shape. Not at random, but following the pattern that had been previously programmed.
The analogy is almost domestic. “It is like an elastic sheet stretched and fixed at the edges. While clamped, it does not deform; but when released, it adopts a new geometry determined by internal tensions,” adds Guillamat. In the case of tissue, these tensions do not come from outside, but from the activity of the cells themselves.
To understand and predict this behavior, the team also developed theoretical models and simulations. This is where the work led by Marino Arroyo, an expert in environmental engineering, comes into play, which allowed establishing a quantitative relationship between the cell orientation pattern and the final shape of the tissue. “Our models have allowed us to identify the mechanism by which cell orientation leads to three-dimensional folding – says Arroyo -. And, in addition, they provide a quantitative relationship between pattern and shape.”
It is, in essence, a language. A way to translate cellular organization into geometry. For Xavier Trepat, co-author of the study, the advance has a clear meaning: “We are showing that we can design the shape a living tissue will take simply by controlling how its cells orient themselves“The important word here is “design.” Because it implies going from observing biology to beginning to direct it.
The implications are enormous. In tissue engineering, it could allow the creation of three-dimensional structures without the need for artificial scaffolds, allowing the material itself to organize itself. In biohybrid robotics, opens the door to systems that move thanks to living tissues that act as actuators. And in the design of smart materials, it suggests the possibility of living surfaces capable of changing shape (and perhaps even function) in response to stimuli.
“These systems They can be considered living materials that generate programmable forces and shapesand that can also integrate information and respond intelligently – concludes Guillamat -. “It is a perfect tool to understand how cellular orientation patterns influence the mechanics and evolution of complex tissues.”
Ultimately, what this study suggests is a change in focus. For decades, engineering has attempted to impose forms on living matter. Now start learning something different: how to whisper instructions to her so that she can shape herself.