Researchers have long believed that\u00a0Propionibacterium acnes\u00a0causes acne. But these bacteria are plentiful on everyone\u2019s skin and yet not everyone gets acne, or experiences it to the same degree. Genetic sequencing recently revealed that not all\u00a0P. acnes\u00a0are the same \u2014 there are different strains, some of which are abundant in acne lesions and some that are never found there.
\nStill, acne research and therapeutic development have been hampered by the lack of an animal model that replicates the human condition. When administered to mice, for example,\u00a0P. acnes\u00a0don\u2019t cause long-term skin lesions and the mouse immune system rapidly clears away the bacteria. Now, however, researchers at University of California San Diego School of Medicine, Cedars-Sinai and UCLA have developed a new mouse model that closely resembles human acne by adding one new factor \u2014 a synthetic sebum, the waxy skin secretion that increases in human adolescence.
\nFor the first time, the model, described in a paper published March 7 in\u00a0JCI Insight, allowed the researchers to directly compare “good” (health-associated) and “bad” (acne-associated) strains of\u00a0P. acnesbacteria in a way that is more relevant to human acne than in previous attempts.
\n“Since we know exactly which genes differ between these strains, next we can pinpoint exactly what it is about the acne-associated strains that allows them to cause skin lesions,” said George Y. Liu, MD, PhD, professor and chief of the Division of Pediatric Infectious Diseases at UC San Diego School of Medicine. “And that information will help us develop new therapies that specifically block those acne-promoting factors, or tip the balance of a person\u2019s skin chemistry in favor of the healthy strains.”\u00a0
\nLiu was a faculty member at Cedars-Sinai at the time of the study.
\nLiu and team prepared synthetic sebum by following a recipe they found in a previous scientific study, a simple concoction of four ingredients \u2014 fatty acid, triglyceride, wax and squalene, a precursor compound to sterols, such as cholesterol and steroid hormones \u2014 in ratios that resemble human sebum. (Mice produce skin sebum, too, but its makeup is different.)
\n“When we started working with these bacteria and checked out the animal models others have been using over the years, we thought \u2018we\u2019ve got to come up with something better than this,\u2019” Liu said. “Acne typically occurs when a person hits their teenage years \u2026What\u2019s the difference between a child\u2019s skin and a teenager\u2019s skin? Increased sebum production. And we were surprised to find how such a simple addition made a big difference in our ability to study acne.”\u00a0
\nThe researchers inoculated mice with\u00a0P. acnes\u00a0and applied fresh sebum daily. Without the sebum, the mice had minimal lesions and the bacteria were rapidly cleared from the site of administration. With the sebum alone, there was no effect on the skin.
\nBut when Liu and team applied both sebum and acne-associated strains of\u00a0P. acnes, they saw what looked like human acne, and the bacteria survived for weeks. These\u00a0P. acnes\u00a0strains also caused inflammation in the skin, as measured by elevated levels of inflammatory molecules called cytokines.
\nThen the researchers tried the same with health-associated strains of\u00a0P. acnes\u00a0\u2014 strains that aren\u2019t found in human acne lesions. The same amount of bacteria was still present on the skin three days after inoculation, no matter the strain applied. But researchers could clearly see the differences between strains just by looking at the mice, Liu said. Lesions caused by acne-associated\u00a0P. acnes\u00a0strains scored approximately two times higher than lesions caused by health-associated strains in a measure that takes into account a lesion\u2019s size, redness, dryness and degree of skin sloughing.
\nUnlike people, the mice in these experiments were all genetically identical. Liu said that\u2019s important because it means that the differences in acne severity were due only to differences between the bacterial strains, not differences in the mice\u2019s innate ability to react to the bacteria.
\nNext, the team hopes to improve upon its acne mouse model so they can achieve similar results when the bacteria are applied topically rather than administered by injection under the skin. They also want to study the genes that are unique to acne-associated\u00a0P. acnes\u00a0strains and determine what it is about human sebum that promotes these strains.
\nLiu said this information could help the team better understand who is at increased risk for acne, and how to develop personalized therapies and vaccines that target the acne-promoting bacterial factors or sebum components.\u00a0
\nCo-authors of this study include: Stacey L. Kolar, Juan Torres, Xuemo Fan, Cedars-Sinai; Chih-Ming Tsai, Cedars-Sinai and UC San Diego; and Huiying Li, UCLA.
\nThis research was funded, in part, by the National Institutes of Health (R21AI103839, R01GM099530).<\/p>","protected":false},"excerpt":{"rendered":"
Researchers have long believed that\u00a0Propionibacterium acnes\u00a0causes acne. But these bacteria are plentiful on everyone\u2019s skin and yet not everyone gets acne, or experiences it to the same degree. Genetic sequencing recently revealed that not all\u00a0P. acnes\u00a0are the same \u2014 there are different strains, some of which are abundant in acne lesions and some that are […]<\/p>","protected":false},"author":726,"featured_media":280702,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"11560","_seopress_titles_title":"Proof of pimple: Mouse model validates how \u2018good\u2019 and \u2018bad\u2019 bacteria affect acne","_seopress_titles_desc":"","_seopress_robots_index":"","jnews-multi-image_gallery":[],"jnews_single_post":[],"jnews_primary_category":[],"jnews_social_meta":[],"jnews_override_counter":[],"footnotes":""},"categories":[12360,11560,11551],"tags":[],"class_list":["post-280726","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-duplicate","category-la-jolla-village-news","category-news"],"_links":{"self":[{"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/posts\/280726","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/users\/726"}],"replies":[{"embeddable":true,"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/comments?post=280726"}],"version-history":[{"count":0,"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/posts\/280726\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/media\/280702"}],"wp:attachment":[{"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/media?parent=280726"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/categories?post=280726"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/test.sdnews.com\/es\/wp-json\/wp\/v2\/tags?post=280726"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}