Martin Blaser, MD, director of New York University’s Human Microbiome Program, compares his work investigating the cutaneous, or skin, microbiome to exploring a new land.
“It’s like we’re looking at the map of Africa in the year 1800,” he said. “We knew what the outlines were but we didn’t know many of the details. That’s true about the skin microbiome in general and the skin microbiome in psoriasis.”
The foreign microorganisms that make up our microbiome account for 1 to 3 percent of our body mass — that’s between one-and-a-half and four-and-a-half pounds of bacteria in a 150-pound adult. These commensal and symbiotic bacteria are largely good for us; they keep our immune system, metabolism, and hormones in check.
In 2013, Dr. Blaser, author of Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues, published a study that decoded the microbial colonies living on the skin of people with psoriasis. The study was one facet of the massive Human Microbiome Project, a $157 million, five-year study funded by the National Institutes of Health.
“This was a study that was to begin filling in those details,” he said.
Dr. Blaser isn’t new to the work; in 2007, he and his team performed the first modern-era comparative study of the skin microbiome, in research funded by the Ellison Foundation.
“We found that there were some differences between the skin in people with psoriasis and people without,” he said.
His contribution to the Human Microbiome Project sought to characterize and compare the skin microbiome of people with psoriasis, people without psoriasis (the control), and people with psoriasis with “uninvolved skin,” he said.
According to his findings, “the taxonomic richness and evenness [of the microbiome] decreased in both lesion and unaffected communities compared to control” — in other words, even if the disease isn’t manifesting in plaques on the skin, something is still going on at the systemic level that’s wiping out friendly bacteria.
Today, Dr. Blaser is studying the relationship between gut microbiota and juvenile diabetes, also an autoimmune disease. While he hasn’t delved into the gut bacteria of psoriasis patients, he’s quick to note that "one of the ideas is that what’s going on in the gut is influencing the skin.”
As it turns out, psoriatic disease is never far from his mind.
“I have psoriasis, mostly involving fingers and ankles,” he said. “It’s mild and annoying but it hasn’t been a major medical problem. I’ve had it for decades, and my father had it, too.”
Jose Scher, MD, a rheumatologist who is also working out of NYU, has studied the gut microbiome of patients with psoriatic arthritis for years. In 2015, Dr. Scher and a team of 13 co-authors published a report that echoed Dr. Blaser’s findings for the Human Microbiome Project. Dr. Scher and his team found that decreased bacterial diversity in patients with psoriatic arthritis altered the intestinal microbiota in a way that resembles the microbial imbalance in inflammatory bowel disease, also an autoimmune disease.
Both psoriasis patients and psoriatic arthritis patients, according to Scher, show decreased levels of the bacteria Coprococcus. But the microbial diversity of psoriatic arthritis patients was further implicated, with lower levels of the bacteria Akkermansia and Ruminococcus — both also reduced in IBD — “suggesting a chronological loss of diversity that may correlate with the natural history of disease.”
Researchers are only beginning to understand how microbial imbalances could correlate to inflammation and chronic disease. What could work to restore the colonies of good bacteria in our guts and on our skin — from targeted probiotics to fecal transplants — marks the next journey in this new frontier.
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