New technique helps ‘visualize’ osmotic pressure within living embryonic tissues

To survive, organisms must regulate their internal pressures, from the single-cell level to tissues and organs. Measuring these stresses in living cells and tissues under physiological conditions is a challenge.

The research, which originated at UC Santa Barbara, is now reported by scientists at the Technical University of Dresden (TU Dresden), Germany’s cluster of excellence Physics of Life (PoL), in the journal Nature communication A new technique to ‘visualize’ these stresses as organisms develop. These measurements can help understand how cells and tissues survive under stress and reveal how problems in stress regulation lead to disease.

When molecules dissolved in water are partitioned, the water tends to flow from one compartment to another to adjust the concentration, a process known as osmosis. If some molecules cannot cross the membrane that separates them, a pressure imbalance -; Absorption pressure -; Compartments are created. This principle is the basis of many technological applications, such as the desalination of sea water or the development of moisturizing creams. It appears that maintaining a healthy functioning organism makes the list.

Our cells are constantly moving molecules in and out so that pressure doesn’t build up to crush them. To do this, they use molecular pumps that allow them to control pressure. This osmotic pressure affects many aspects of cell life and even determines their size.

When cells group together to form our tissues and organs, they also face a pressing problem: our vascular systems, or organs like the pancreas or liver, have fluid-filled cavities known as lumens that are essential for their function. If cells fail to regulate osmotic pressure, these lumens can collapse or burst, with potentially catastrophic consequences for the organ. To understand how cells regulate pressure in these tissues or how they fail to do so in disease, it is essential to measure and ‘see’ osmotic pressure in living tissues. But unfortunately, it was not possible.

Until now.

Led by former UCSB professor Otger Kamps, who is now chair of tissue dynamics at TU Dresden and currently managing director of PoL, the scientists developed a novel technique to measure osmotic pressure in living cells and tissues using special droplets. Double emulsions. For this pressure sensor, they introduced a water droplet into an oil droplet that allowed water to flow through. When these “double-droplets” are exposed to salt solutions of different concentrations, water flows from the inner water droplet and changes its volume, until the pressures are adjusted. Researchers have shown that osmotic pressure can be measured simply by examining droplet size. They then applied these double-droplets to living cells and tissues using glass microcapillaries to reveal their osmotic pressure.

It turns out that cells in animal tissues have the same osmotic pressure as plant cells, but unlike plants, they must maintain constant equilibrium with their environment to avoid bursting, because they don’t have strong cell walls.”

Otger Campus, former UCSB professor

With this simple concept, this innovative method now allows scientists to “see” osmotic pressure in a wide range of settings. “We know that a number of physical processes affect how our bodies function,” Campus said. “In particular, osmotic pressure is known to play a fundamental role in organ formation during embryogenesis and in the maintenance of healthy adult organs. With this new technique, we can now study how osmotic pressure directly affects all these processes in living tissue.”

Beyond providing insight into biological processes and the physical principles that govern life, this method holds promising industrial and medical applications, including skin hydration monitoring, cream or food properties, and diagnosis of osmotic pressure imbalance diseases, such as cardiovascular disease or tumors. The technique is currently patented by UC Santa Being issued by Barbara, where she performed her research before joining the campus TU Dresden.

The campus lab previously developed unique techniques to measure additional physical properties using tiny energy and tiny single droplets created inside cells and tissues. Antoine Vian, lead author of the work and an expert in microfluidics, emphasized the technology that enables the creation of double-emulsion droplets, stressing their key role.

“Double-emulsions are very versatile, with many applications in science and technology,” he said. “Single droplets can deform, but are incompressible and do not allow pressure measurements. In contrast, double emulsion droplets can change shape and can be used as osmotic pressure sensors. Their use in living systems will certainly enable new and exciting discoveries.”