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Scientists have found that smoking causes changes in human lungs that can make breathing more physically difficult over time. A recent study revealed that lung tissue from smokers becomes stiffer and less flexible, resembling scarred lungs affected by fibrosis.
The research, conducted at the University of California, Riverside, was published in the Journal of the Royal Society Interface.
Lungs are primarily composed of soft tissue called parenchyma, which acts like a flexible sponge that stretches and relaxes with each breath. In healthy lungs, this tissue expands easily, allowing oxygen to enter the bloodstream and carbon dioxide to exit efficiently.
While smoking harms many parts of the respiratory system, researchers aimed to understand exactly how it alters the physical mechanics of lung tissue itself. To do this, they collected lung samples from human donors—either for transplantation or scientific research—and cut small pieces to test how they behaved when stretched.
Unlike previous studies that stretched tissue in just one direction or relied heavily on animal models like mice, this study employed experiments that stretched lung samples simultaneously in multiple directions. This approach more accurately mimics the natural expansion of lungs during breathing.
The differences between smoker and non-smoker lung tissues were quite apparent. Tissue from smokers resisted stretching much more, indicating increased stiffness and reduced elasticity. The behavior of this tissue resembled lungs affected by fibrosis, a condition characterized by scar tissue buildup that makes breathing increasingly difficult.
When lungs lose their flexibility, the body has to work harder to breathe. Over time, this can lead to reduced oxygen supply and increased fatigue in the respiratory system.
Mona Eskandari, the lead researcher, pointed out that understanding the true mechanics of lung tissue is essential, as lungs do not stretch uniformly in real life. The study also uncovered that even within a healthy lung, mechanical properties vary across different regions.
Specifically, tissue from the upper parts of the lungs was generally stiffer than that from the lower areas. The researchers believe gravity might influence this, as humans spend most of their lives upright, causing different parts of the lungs to experience varying physical forces over many years.
This discovery could help explain why certain lung injuries develop unevenly. For instance, some patients on ventilators may experience damage in specific lung regions due to overstretching. The study suggests that some areas naturally tolerate stress less effectively than others.
Additionally, the researchers measured how much energy the lungs lose during repeated stretching. Human lung tissue lost more energy than what is typically seen in mice, which could explain why animal models don’t always accurately predict human lung behavior.
This finding is particularly relevant as scientists develop advanced computer models—referred to as “digital twin” lungs—that simulate breathing, disease progression, and treatment responses. If these models rely mainly on animal data, they might not fully capture human lung mechanics.
The team also found early signs suggesting lungs may stiffen naturally with age, although more research is needed to confirm this. A drawback of the study was the limited number of healthy donor lungs available, making extensive testing challenging. Nonetheless, the researchers believe this represents one of the most detailed analyses of human lung tissue to date.
The insights gained could improve medical technologies like ventilators, surgical planning tools, and computer simulations used to study lung diseases. The research was carried out in Eskandari’s biomechanics laboratory, known as the bMECH lab, which focuses on understanding how biological tissues move and respond to mechanical forces.
Overall, this study offers a clearer picture of how smoking physically impacts the lungs. An important strength is that it used actual human tissue rather than relying primarily on animal models. The findings could guide future innovations in treatment and device development for lung health.
However, further studies with larger sample sizes are essential to fully unravel how smoking, aging, and lung diseases influence lung mechanics over time. For those interested in lung health, exploring topics like COPD-friendly foods, the potential role of vitamins C and E in lung cancer prevention, and dietary choices that benefit lung function could be valuable.
Source: University of California, Riverside.
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