Researchers can now visualize osmotic pressure in living tissue

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In order to survive, organisms must control the pressure inside them, from the single-cell level to tissues and organs. Measuring these pressures in living cells and tissues in physiological conditions is a challenge.

In research that has its origin at UC Santa Barbara, scientists now at the Cluster of Excellence Physics of Life (PoL) at the Technical University in Dresden (TU Dresden), Germany, report in the journal Nature Communications a new technique to ‘visualize’ these pressures as organisms develop. These measurements can help understand how cells and tissues survive under pressure, and reveal how problems in regulating pressures lead to disease.

When molecules dissolved in water are separated into different compartments, water has the tendency to flow from one compartment to another to equilibrate their concentrations, a process known as osmosis. If some molecules cannot cross the membrane that separates them, a pressure imbalance — osmotic pressure — builds up between compartments. This principle is the basis for many technical applications, such as the desalination of seawater or the development of moisturizing creams. It turns out that maintaining a healthy functioning organism makes the list, too.

Our cells are constantly moving molecules in and out to prevent the pressure build-up from crushing them. To do so, they use molecular pumps that allow them to keep the pressure in check. This osmotic pressure affects many aspects of cells’ lives and even sets their size.

When cells team up to build our tissues and organs, they, too, face a pressure problem: Our vascular system, or organs such as the pancreas or liver, contain fluid-filled cavities known as lumens that are essential for their function. If cells fail to control osmotic pressure, these lumens may collapse or explode, 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’ the osmotic pressure in live tissues. But unfortunately, this was not possible.

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