presented at the annual meeting of the Society for Investigative Dermatology.
There have been reports of gut microbiome dysbiosis associated with autoimmune diseases such as rheumatoid arthritis, diabetes, and celiac disease. “It is now clear that these events not just shape the immune response in the gut, but also distant sites and immune-privileged organs,” Tanya Sezin, a doctor of natural science from the University of Lübeck (Germany) and Columbia University, New York, said in her presentation.
Whether the gut microbiome may also play a role as an environmental factor in alopecia areata, another T-cell–mediated autoimmune disease for which there are few available treatment options, is being evaluated at the Christiano Laboratory at Columbia University, Dr. Sezin noted. “Much of the difficulty underlying the lack of an effective treatment has been the incomplete understanding of the pathogenesis of AA.”
She also referred to several case reports describing hair growth in patients who received fecal microbiota transplantation (FMT), including a 20-year-old with alopecia universalis, who experienced hair growth after receiving FMT for Crohn’s disease.
Dr. Sezin and colleagues at the lab first performed a study in mice to test whether the gut microbiome was involved in the pathogenesis of AA. Mice given an antibiotic cocktail of ampicillin, neomycin, and vancomycin prior to or at the time of a skin graft taken from a mouse model of AA to induce AA were protected from hair loss, while mice given the antibiotic cocktail after skin grafting were not protected from hair loss.
“16S rRNA sequencing analysis of the gut microbiota revealed a significant shift in gut microbiome composition in animals treated with antibiotics and protected from hair loss, as reflected by significant changes in alpha and beta diversity,” Dr. Sezin explained. “In AA mice, we also observed differential abundance of families from the Bacteroidetes and Firmicutes phyla.” Specifically, Lactobacillus murinus and Muribaculum intestinale were overrepresented in mice with AA.
The investigators then performed 16S rRNA sequencing on 26 patients with AA, who stopped treatment for 30 days beforehand, and 9 participants who did not have AA as controls. “Though we did not observe difference in alpha and beta diversity, we see changes in the relative abundance of several families belonging to the Firmicutes phyla,” in patients with AA, Dr. Sezin said.
In another cohort of 30 patients with AA and 20 participants without AA, who stopped treatment before the study, Dr. Sezin and colleagues found “differences in the relative abundance of members of the Firmicutes and Bacteroides phyla,” including Bacteroides caccae, Prevotella copri, Syntrophomonas wolfei, Blautia wexlerae, and Eubacterium eligens, she said. “Consistent with our findings, there are previous reports in the literature showing gut dysbiosis in several other autoimmune diseases associated with differential regulation of some of the top species we have identified.”
Dr. Sezin said her group is recruiting patients for a clinical trial evaluating FMT in patients with AA. “We plan to study the association between changes in the gut microbiome and immune cell composition in AA patients undergoing FMT,” she said. “Additionally, functional studies in mice are also currently [being conducted] to further pinpoint the contribution of gut microbiome to the pathogenesis of AA.”
When asked during the discussion session if there was any relationship between the skin microbiome and AA, Dr. Sezin said there was no connection found in mice studies, which she and her colleagues are investigating further. “In the human samples, we are currently recruiting more patients and healthy controls to try to get a better understanding of whether we see differences in the skin microbiome,” she added.
Dr. Sezin explained that how the gut microbiota “is really remediated in alopecia areata” is not well understood. “We think that it is possible that we see intestinal permeability in the gut due to the gut dysbiosis that we see in alopecia areata patients, and this might lead to systemic distribution of bacteria, which might cross-react or present cross reactivity with the antigens” identified in AA, which is also being investigated, she said.
FMT not a ‘simple fix’ for AA
Leslie Castelo-Soccio, MD, PhD, a dermatologist at the Children’s Hospital of Philadelphia, who was not involved with the research, said in an interview that the findings presented by Dr. Sezin show how AA shares similarities with other autoimmune diseases. “It does highlight how important the gut microbiome is to human disease, and that differences in relative abundance of bacteria play one part as a trigger in a genetically susceptible person.”
However, while some autoimmune diseases have a big difference in alpha and beta diversity, for example, “this has not been seen in people with alopecia areata,” Dr. Castelo-Soccio pointed out. “The differences are more subtle in terms of amounts of certain bacteria,” she said, noting that, in this study, the biggest differences were seen in the studies of mice.
Dr. Castelo-Soccio also said there may be also be differences in the gut microbiome in children and adults. “The gut microbiome shifts in very early childhood from a very diverse microbiome to a more ‘adult microbiome’ around age 4, which is the age we see the first peak of many autoimmune diseases, including alopecia areata. I think microbiome work in humans needs to focus on this transition point.”
As for the clinical trial at Columbia that is evaluating FMT in patients with AA, Dr. Castelo-Soccio said she is excited. “There is much to learn about fecal transplant for all diseases and about the role of the gut microbiome and environment. Most of what we know for fecal transplant centers on its use for Clostridium difficile infections.”
Patients and their families have been asking about the potential for FMT in alopecia area, Dr. Castelo-Soccio said, but some believe it is a “simple fix” when the reality is much more complex.
“When I speak to patients and families about this, I explain that currently the ‘active ingredient’ in fecal transplants is not definitively established. In any one donor, the community of bacteria is highly variable and can be from batch to batch. While the short-term risks are relatively low – cramping, diarrhea, discomfort, mode of delivery – there are reports of transmission of infectious bacteria from donors like [Escherichia] coli, which have led to severe infections.”
Long-term safety and durability of effects are also unclear, “so we do not know if a patient receiving one [FMT] will need many in the future. We do not know how changing the microbiome could affect the transplant recipient in terms of noninfectious diseases/disorders. We are learning about the role of microbiome in obesity, insulin resistance, mood disorders. We could be ‘fixing’ one trigger of alopecia but setting up [the] patient for other noninfectious conditions,” Dr. Castelo-Soccio said.
Dr. Sezin and Dr. Castelo-Soccio reported no relevant financial disclosures.