AUTHOR=Spittaels Karl-Jan , Ongena Ruben , Zouboulis Christos C. , Crabbé Aurélie , Coenye Tom 

TITLE=Cutibacterium acnes Phylotype I and II Strains Interact Differently With Human Skin Cells

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2020.575164

DOI=10.3389/fcimb.2020.575164

ISSN=2235-2988

ABSTRACT=<p>Acne vulgaris is one of the most common skin disorders and affects the pilosebaceous units. Although the exact pathogenesis of acne is still unknown, <italic>Cutibacterium acnes</italic> (formerly known as <italic>Propionibacterium acnes</italic>) is considered one of the key contributing factors. In fact, a significant association exists between <italic>C. acnes</italic> strains belonging to phylotype I and acne. However, there is still heavy debate on the exact role of <italic>C. acnes</italic> in acne and its behavior in the pilosebaceous unit, and more specifically its interactions with the human skin cells. In this study, key elements of the host-pathogen interaction were studied for a collection of <italic>C. acnes</italic> strains, belonging to phylotype I and II, including association with HaCaT keratinocytes and SZ95 sebocytes, the effect of <italic>C. acnes</italic> on keratinocyte tight junctions in a HaCaT monoculture and in an additional keratinocyte-sebocyte co-culture model, and <italic>C. acnes</italic> invasion through the keratinocyte cell layer. Our data showed association of all <italic>C. acnes</italic> strains to both skin cell lines, with a significantly higher association of type I strains compared to type II strains. Microscopic imaging and western blot analysis of the tight junction protein ZO-1, together with transepithelial electrical resistance (TEER) measurements revealed an initial induction of keratinocyte tight junctions after 24 h infection but a degradation after 48 h, demonstrating a decline in cell lining integrity during infection. Subsequently, <italic>C. acnes</italic> was able to invade after 48 h of infection, although invasion frequency was significantly higher for type II strains compared to type I strains.</p>