Living cells cool much more slowly than our current understanding of heat conduction, according to new research from the University of Tokyo. The researchers used two techniques: high-speed temperature mapping and artificial heating to observe how heat is dissipated from liquid-filled artificial sacs (liposomes) that are similar in size to living cells.
Although heat dissipated rapidly from the artificial liposomes as expected, other biomolecules within the cells significantly slowed down the cooling of the cells. Understanding the processes behind the slowing of heat dissipation within cells could influence how conditions associated with changes in body temperature are treated, such as epilepsy, inflammation, and cancer.
Are you a little hot or cool as a cucumber? Your body’s internal temperature is a byproduct of all the work your cells do to help you live, move, and thrive. More recently, researchers discovered that spontaneous heat generation within cells can vary by as much as 1 to 2 degrees Celsius and appears to play an important role in driving important cell-based activities and functions. This has so far included turning neural stem cells into neurons and a heat shock response that protects stressed cells from damage.
Since our cells are mostly sacs of jelly-like liquid, it is not unreasonable to think that the heat they produce behaves according to typical physical laws that apply to all liquids. However, a paper published in 2012 revealed the world’s first map of temperature distribution inside cells and a surprising fact.
Our results showed that there is a large gap between the “laws of physics” and the “reality of life” in terms of how temperature inside cells changes. We wanted to resolve this paradox ourselves and discovered that cells are highly specialized environments that handle heat in very specific ways.
Koki Okabe Senior author and specially appointed associate professor, Graduate School of Pharmaceutical Sciences, The University of Tokyo
The research team used an ultra-sensitive microscope (called a fast fluorescence lifetime imaging microscope) and a custom-built thermometer to map temperature changes in detail in real time. After heating part of the cell with an infrared laser, the cooling process was monitored with millisecond precision. The research team performed the same test on liquid sacs (liposomes) that resemble artificial cells. We then compared the temperature changes within the cells and liposomes to model-based predictions.
According to conventional physics, heat should spread (diffuse) out of a fluid very quickly, and the researchers confirmed that this also happens in liposomes. However, they found that heat tends to “stay” inside cells. Diffusion was not only slow but also dependent on where it was heated within the cell and on the surrounding molecules. From their observations, they concluded that the slow rate of change was an inherent property of the cells and not a side effect of the research method.
“The phenomenon of ‘no heat spreading’ is an unprecedented phenomenon, and we cannot rely on existing textbooks to decipher the physical mechanisms behind what we see. This phenomenon completely overturns our conventional understanding,” Professor Okabe says.
Next, the researchers want to dig deeper into the mechanisms behind this slow heat transfer. “We believe that this trapped heat is not just a waste product, but acts as a concentrated energy source to power cellular functions,” Okabe explained. “By redefining heat as an ‘active signal’ that cells use to regulate themselves, rather than just a byproduct, we hope to unlock new ways to understand life and develop innovative treatments.”
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Reference magazines:
Masaki Takarada others (2026). Non-diffusive slow heat dissipation causes localized high temperatures in living cells. nature communications. DOI: 10.1038/s41467-026-71878-y. https://www.nature.com/articles/s41467-026-71878-y.
