Wild animals allow new insights into the skin microbiome
Research team at Kiel University describes differences in the bacterial colonization of the skin in house and laboratory mice as a basis for future improved dermatological models for the first time
In recent decades, the diversity of microbial colonization of the body has decreased significantly under the harmful influence of the western lifestyle. This ‘impoverished’ microbiome has led to a sharp increase in so-called environmental diseases in humans. These mostly inflammatory disease patterns often affect the skin, which as a barrier organ is in direct contact with the environment. There they appear for example as psoriasis or neurodermatitis. An important goal of microbiome research is therefore future therapeutic interventions to restore a healthy composition of the microbial colonization of the body and especially the skin. To this end, scientists often use the house mouse, which is similar to humans in its immune regulation as a model organism in order to first define such a healthy normal state of the microbiome as a starting point.
However, it is problematic that the microbial colonization of laboratory animals differs from that of their conspecifics living under natural conditions. In order to be able to make statements about possible general characteristics of the microbial composition, a research team from Kiel University (CAU) has now for the first time systematically compared the skin microbiome of house and laboratory mice. The researchers from the Evolutionary Medicine group led by Professor John Baines at the Institute of Experimental Medicine at the CAU were able to show that the general composition of microorganisms in wild animals and laboratory mice shows great similarities regardless of the radically different living conditions, which indicates a strong control of microbial colonization by the host organism. In detail, however, depending on the geographical origin, wild mice show a characteristic composition of the skin microbiome that differs from that of laboratory animals, especially within the bacterial genus Staphylococcus, and is significantly more diverse in wild animals. The Kiel researchers recently published their results in the journal The ISME Journal as part of the Collaborative Research Center (SFB) 1182 “Origin and Functioning of Metaorganisms”.
Global agreement of skin microbiomes
The skin forms a central physical and immunological barrier to shield the body from environmental influences. At the same time, this barrier layer represents a dynamic ecosystem, which is populated by a large variety of microbial symbionts. Which factors control the composition of this community is largely unknown so far. In order to understand the laws of this regulation, the study of wild organisms, which have to maintain a balanced microbiome in contact with changing environmental conditions, is particularly suitable. The Kiel research team therefore collected more than 200 wild mice in about 30 different rural locations in an area of 270 square kilometers in southwestern France. They took samples from the skin of their ears and compared them with material from laboratory mice from several different locations, all of which originated from hygienic laboratory environments.
The analysis of the microbial communities contained in these samples showed that despite drastic differences in environmental conditions, both wild and laboratory mice harbor similar compositions of microbes overall. “This global agreement suggests that despite a large pool of microorganisms in the environment that are likely to colonize the mice, it is mainly a relatively similar and stable composition of microorganisms that colonizes the skin of the animals,” emphasizes Dr. Meriem Belheouane, researcher in Baines’ research group. “This occurs independently of living conditions and is apparently subject to selection by the host life form, which provides a specific habitat tailored to a particular group of characteristic microbes,” the first author continues.
On the other hand, wild mice have a significantly higher proportion of unique components of the microbiome than laboratory mice. This indicates that these are specific microorganisms that depend on the geographical location, that only occur at a certain place and that take over certain functions within the microbiome. This influence of local location is also reflected in an increasing deviation of the microbiome composition with increasing distance between the habitats of wild mice.
Important model for the study of skin diseases
All in all, the work now presented provides an important basis for an improved understanding of the skin microbiome – in both healthy and diseased states. In particular, it enables more detailed insights into the formation of the microbial communities associated with the mice, especially by studying the differences between wild and laboratory mice. On this basis, it may be possible in the future to explain, among other things, why wild mice exhibit immune characteristics that are more similar to humans than those of laboratory animals. “Our observations could help to improve animal model systems for a better understanding of skin diseases”, emphasizes Baines, who is also a member of the board of directors of the Cluster of Excellence “Precision Medicine in Chronic Inflammation” (PMI). “The new findings can thus contribute to advancing biomedical skin research and represent a further step towards future therapeutic interventions based on the skin microbiome,” Baines continued.