High bacterial colonization and lipase activity in microcomedones

Abstract

Background:Although acne vulgaris has a multifactorial aetiology, comedogenesis and bacteria colonization of the pilosebaceous unit are known to play a major role in the onset of inflammatory acne lesions. However, many aspects remain poorly understood such as where and when is the early stage of the Propionibacterium acnes colonization in follicular unit? Our research aimed at providing a precise analysis of microcomedone's structure to better understand the interplay between Propionibacterium acnes and follicular units, and therefore, the role of its interplay in the formation of acne lesions.Methods: Microcomedones were sampled using cyanoacrylate skin surface stripping (CSSS). Their morphology was investigated with multiphoton imaging and their ultrastructure with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Bacterial lipase activity in the microcomedones was quantified using a dedicated enzymatic test as well as a Fourier Transform Infra-Red (FTIR) analysis. The porphyrin produced by bacteria was analysed with HPTLC and fluorescence spectroscopy. Results:The imaging analysis showed that microcomedones' structure resembles a pouch, whose interior is mostly composed of lipids with clusters of bacteria and whose outer shell is made up of corneocyte layers. The extensive bacteria colonization is clearly visible using TEM. Even after sampling, clear lipase activity was still seen in the microcomedone. A high correlation, r = .85, was observed between porphyrin content measured with HPTLC and with fluorescence spectroscopy. These observations show that microcomedones, which are generally barely visible clinically, already contain a bacterial colonization. K E Y W O R D SAcne vulgaris, electron microscopy, fluorescence, fourier transform infrared, hair follicle, Inflammation, multiphoton microscopy, Propionibacterium acnesThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Exploring the human hair follicle microbiome*

“…However, given the abundance of P. acnes in the human HF microbiome, it may be relevant for acne-related activities of monocyte-derived perifollicular macrophages that excessive skin colonization with certain P. acnes strains can increase TLR2-mediated monocyte secretion of IL-12 and IL-8, thus promoting an inflammatory response. [129][130][131] Retinoids and tetracyclines, two standard acne therapies, both modulate the skin microbiome, presumably causing a decrease in Propionibacteria and an increase in Staphylococci, Streptococci and overall species diversity. 132 However, a recent study has reported the opposite: a higher density of P. acnes and a decrease of Staphylococci and Enterococci in healthy controls compared with patients with acne.…”

“…However, given the abundance of P. acnes in the human HF microbiome, it may be relevant for acne‐related activities of monocyte‐derived perifollicular macrophages that excessive skin colonization with certain P. acnes strains can increase TLR2‐mediated monocyte secretion of IL‐12 and IL‐8, thus promoting an inflammatory response 129–131 …”

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

“…C. acnes macrocolonies of more than 1,000 bacterial cells can be observed in association with the follicular epithelium of the pilosebaceous unit; they are more often present in follicles from acneic skin biopsies than in follicles of individuals with healthy skin ( Jahns et al., 2012 ). High bacterial colonization of the follicles was recently also observed in transmission electron microscopy images of microcomedones ( Josse et al., 2020 ). As C. acnes growth and proliferation in the pilosebaceous unit is considered one of the factors that contributes to the etiology of acne, we first investigated the ability of strains belonging to phylotypes I and II to associate with HaCaT keratinocytes and SZ95 sebocytes.…”

Fostering a healthy culture: Biological relevance of in vitro and ex vivo skin models

“…Another common skin disorder ripe for in vitro modelling is acne vulgaris, where genetic predispositions, hormonal changes, stress and environmental factors lead to the formation of microcomedones, [65][66][67] many of which can become inflamed. 68…”

“…Another common skin disorder ripe for in vitro modelling is acne vulgaris , where genetic predispositions, hormonal changes, stress and environmental factors lead to the formation of microcomedones, 65‐67 many of which can become inflamed 68 . Inflammatory microcomedones are caused by hyperseborrhoea, where fatty acid composition of sebum becomes altered, leading to accumulation of peroxidized squalene and favouring expansion of C. acnes 66,69,70 .…”