Our Tainted Food Supply: Its Lasting Effects on Stem Cells May Explain Declines in Sperm Counts

Spermatozoons, floating to ovuleIn the science fiction film, Children of Men, humans in the year 2027 face extinction due to decades of infertility. This premise doesn’t seem all that far-fetched when you consider studies in the U.S., Japan, and Europe over the past two decades that point to declining sperm counts. A 2013 study, for instance, that followed 26,000 French men for 17 years reported a 32% drop in sperm counts. And a study of 5000 Danish men with a median age of 19 found 40% had sperm counts corresponding to infertility or decreased fertility.

So what’s going on here? One line of evidence blames exposure to chemicals that leach into our food and water supply. A possible culprit is the much-despised Bisphenol-A, or BPA, a man-made chemical found in plastic bottles, the inner linings of canned food and even receipt paper used at your local grocery store. BPA is known as a hormone disruptor because it interferes with normal hormone activity in the body by mimicking the female hormone estrogen. Lab animals exposed to low levels of BPA have shown increased incidence of certain cancers, neurological problems, diabetes, obesity, female reproduction problems and, yes, decreased sperm counts.

BPA_shutterstock_243369064Data published last week in PLOS Genetics appears to have pinpointed the link between BPA and decreased sperm counts: stem cells. Specifically the so-called spermatogonial stem cells that give rise to sperm. In the Washington State University study, the research team gave newborn male mice daily oral doses of BPA for about two weeks. The chemical exposure negatively affected this spermatogonial stem cell population by disrupting the processing of the cells’ DNA and, in turn, the development of fully mature sperm. The team got similar results replacing BPA with synthetic estrogen found in birth control pills. This form of estrogen is also known to contaminate our water supply even after sewage treatment.

A surprising and even scary twist to these results is that the brief exposure of BPA or estrogen in the newborn male mice permanently changed their stem cells. The team confirmed this observation by transplanting the spermatogonial stem cells from BPA-exposed mice into the testes of mice that never received BPA. In this case, these mice still exhibited reduced sperm production. As senior author Nancy Hunt points out in an interview with Scientific American, the exposure to these chemicals:

“is not simply affecting sperm being produced now, but impacting the stem cell population, and that will affect sperm produced throughout the lifetime.”

It’s remains debatable whether the detectable BPA or estrogen levels in our food and water supply is high enough to actually cause health problems in humans. In 2013 the Food and Drug Administration (FDA) downplayed possible worries on its website:

“Is BPA safe? Yes. Based on FDA’s ongoing safety review of scientific evidence, the available information continues to support the safety of BPA for the currently approved uses in food containers and packaging.”

Still, this recent study and others like it certainly warrant further investigation. University of Missouri scientist Frederick vom Saal, who was not part of the study, put it this way in his interview with Scientific American:

“It’s important in future studies to see if the stem cell changes from exposure are passed to future generations… Since most people are consistently exposed to BPA and other estrogenic compounds, each generation could have it a bit worse.”

Stem cell stories that caught our eye: fingering chemical cancer cause, treating leukemia and getting better ID on cells

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Stem cells model environmental damage. Using human embryonic stem cells to generate prostate tissue in mice, a team at the University of Illinois has shown how the endocrine-disrupting chemical BPA can lead to prostate cancer. They implanted the cells, derived from human stem cells, along with supportive rodent cells in mice and then fed the mice a diet with low levels of BPA. As the cells matured into prostate tissue in the animals the chemical seemed to reprogram the cells in a manner that raises the risk for cancer. The team reported its work at the annual meeting of the Endocrine Society in Chicago this week and the association’s press release was picked up by Bio-Medicine.

Protecting stem cell “home” may be new therapy. A Spanish team has discovered that certain rare leukemias, known as myeloproliferative disorders, seem to be triggered by damage to the area where stem cells hang out in our bone marrow known as the stem cell niche. Normally the niche controls the behavior of blood-forming stem cells but when it gets inflamed that control breaks down the team reported in the journal Nature. But there is good news, they tested a currently available drug in an animal model and it seemed to reverse the damage to the niche and return normal stem cell controls. ScienceDaily ran a story about the work.

Clever trick could make stem cell frequent fliers. Researchers often share stem cells with colleagues around the world by freezing them first. But in some uses, it would be better if the cells could be shipped in living cultures. That usually requires some sort of electrical motor to agitate the vials to keep the cells from clumping, but airlines don’t allow running electric motors in cargo on planes. So a group of engineering students at the University of California, San Diego, has taken cues from old pendulum clocks and developed a spring powered motor that can keep the cells agitated. As our field gets ready to commercialize cell products, there may be times this could help centralize mass production of cells for shipping. Medical Design Technology explained the students’ project.

Getting a better ID on the “other” bone marrow stem cell. Most people know that our bone marrow has blood-forming stem cells, but it also has mesenchymal stem cells (MSCs). Those cells can form bone, cartilage and fat and release proteins that seem to direct the work of other stem cells. Those skills have led to more than 200 clinical trials investigating the potential of MSCs to treat many diseases. But those trials have often produced results that are hard to interpret, and many researchers in the field say part of the problem comes from our inability to accurately identify true MSCs resulting in most clinical trials using a mixed population of cells. Now one of the leaders in the field, Sean Morrison at the University of Texas Southwest Medical Center, reports that his team has found a reliable marker for MSCs known as leptin receptor. His current work was in mice, but if it can be duplicated with human cells, it could increase the chances for valuable data coming from MSC trials.

Don Gibbons