Microplastics are everywhere, both across nature and inside our bodies. And while evidence shows these synthetic particulates aren’t great for you, the medical community still isn’t entirely sure how the plastic specifically affects health, as well as its influence on preexisting conditions like an increased risk of heart attack or stroke. For the first time, however, experts succeeded in visually tracking the movement of microplastics through brain blood vessels in mice—and the pile-ups resembled a microscopic “car crash.”
The findings, published in the journal Science Advances by a team at Beijing’s Peking University, expand on existing research already showcasing microplastic’s potential neurotoxicity.
“Nanoscale plastics can breach the blood-brain barrier, [but] how [microplastics] cause brain functional irregularities remains unclear,” wrote the study’s authors.
Researchers relied on a fluorescence imaging technique known as two-photon microscopy to get a clearer look on ingested microplastic movements in real-time. In order to do so, however, they first needed to create a small, transparent window into the skulls of lab mice. They then trained the tool on the direct cranial opening after providing their test subjects with water mixed with tiny spheres of fluorescent polystyrene. Previous studies have recorded an estimated 12 nanograms of microplastics per milliliter of blood in humans, so researchers approximated a proportional amount of polystyrene to deliver to the mice. Still one of the most common plastics, polystyrene is found in many toys, packaging, and home appliances. From there, they waited and watched.
According to the study announcement, glowing cells began appearing in brain blood vessels around three hours later. Closer examination suggested they were a combination of neutrophils and phagocytes, two immune system cells responsible for eating harmful foreign objects. Some likely got stuck in the many curves of the smaller blood vessels around the brain’s cortex. But more plastic-laced cells also stacked “like a car crash,” explained Peking University biomedical researcher and study co-author, Haipeng Huang.
These pile-ups eventually resembled blood clots, similarly minimizing blood flow to the brain anywhere from days to weeks. While some of these microplastic-cell concentrations cleared over time, others were still discernible at the end of the four-week experiment.
Researchers cautioned in their study, however, that it is still “premature to directly apply this mechanism to human research systems.” They noted that humans and mice possess different immune, coagulation, cerebrovascular, and cardiovascular systems. The human body’s blood circulation volume is around 1,200 times larger, with wider vascular diameters that likely reduces the potential for microplastic obstructions.
At the same time, our narrowest capillary microvessels measure 8-10 nanometers—not far off from the 8-9 nanometer diameters in mice venous vessel terminal branches. Knowing this, some microplastic obstructions are “likely to have detrimental consequences for cardiovascular health and may result in more severe adverse effects, especially in patients with underlying conditions similar to myocardial infarction,” the researchers caution.
Nature noted that previous studies support the latest observations, particularly one that discovered “tiny, weathered plastic shards” in brain tissue, including blood vessel walls and immune cells, in human bodies donated to research. Experts hope their imagining approach will continue to be used to study how microplastics travel through the body, and what that means for long-term health.
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