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Radboud University, 05 juli 2023, Promotores : Bogaard, E.H.J. van den, Schalkwijk, J. Co-promotores : Zeeuwen, P.L.J.M., Jansen, P.A.M., Contains fulltext : 293834.pdf (Publisher’s version ) (Closed access)

Item does not contain fulltext, In atopic dermatitis (AD), chronic skin inflammation is associated with skin barrier defects and skin microbiome dysbiosis including a lower abundance of Gram-positive anaerobic cocci (GPACs). We here report that, through secreted soluble factors, GPAC rapidly and directly induced epidermal host-defense molecules in cultured human keratinocytes and indirectly via immune-cell activation and cytokines derived thereof. Host-derived antimicrobial peptides known to limit the growth of Staphylococcus aureus-a skin pathogen involved in AD pathology-were strongly upregulated by GPAC-induced signaling through aryl hydrocarbon receptor (AHR)-independent mechanisms, with a concomitant AHR-dependent induction of epidermal differentiation genes and control of pro-inflammatory gene expression in organotypic human epidermis. By these modes of operandi, GPAC may act as an "alarm signal" and protect the skin from pathogenic colonization and infection in the event of skin barrier disruption. Fostering growth or survival of GPAC may be starting point for microbiome-targeted therapeutics in AD.

Contains fulltext : 294910.pdf (Publisher’s version ) (Open Access)

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Contains fulltext : 249501.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 251157.pdf (Publisher’s version ) (Open Access), Late cornified envelope proteins are predominantly expressed in the skin and other cornified epithelia. On the basis of sequence similarity, this 18-member homologous gene family has been subdivided into six groups. The LCE3 proteins have been the focus of dermatological research because the combined deletion of LCE3B and LCE3C genes (LCE3B/C-del) is a risk factor for psoriasis. We previously reported that LCE3B/C-del increases the expression of the LCE3A gene and that LCE3 proteins exert antibacterial activity. In this study, we analyzed the antimicrobial properties of other family members and the role of LCE3B/C-del in the modulation of microbiota composition of the skin and oral cavity. Differences in killing efficiency and specificity between the late cornified envelope proteins and their target microbes were found, and the amino acid content rather than the order of the well-conserved central domain of the LCE3A protein was found responsible for its antibacterial activity. In vivo, LCE3B/C-del correlated with a higher beta-diversity in the skin and oral microbiota. From these results, we conclude that all late cornified envelope proteins possess antimicrobial activity. Tissue-specific and genotype-dependent antimicrobial protein profiles impact skin and oral microbiota composition, which could direct toward LCE3B/C-del‒associated dysbiosis and a possible role for microbiota in the pathophysiology of psoriasis.

Contains fulltext : 251703.pdf (Publisher’s version ) (Open Access)

Radboud University, 08 december 2021, Promotores : Sauerwein, R.W., Schalkwijk, J. Co-promotor : Kooij, T.W.A., Contains fulltext : 240243.pdf (Publisher’s version ) (Open Access)

29 maart 2021, Contains fulltext : 235970.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 229256.pdf (Publisher’s version ) (Open Access), In biomedical research, cell culture contamination is one of the main culprits of experimental failure. Contamination sources and concomitant remedies are numerous and challenging to manage. We herein describe two cases of uncommon contamination of cell cultures that we encountered, and the successful determination and eradication strategies. The first case describes the infection with human adenovirus C that originated from pharyngeal tonsils used for isolation of primary tonsillar epithelial cells. It is known that viral contamination of in vitro cell cultures can occur symptomless and is therefore difficult to identify. The contamination was pervasive and persistent, as it was widely spread in flow cabinets and apparatus, and has caused a serious delay to our research projects and the inevitable loss of valuable (patient-derived) cell sources. Eradication was successful by formalin gas sterilization of the flow cabinet and elimination of all infected cell lines from our biobank after PCR-guided determination. Secondly, we encountered a spore-forming bacterium, namely Brevibacillus brevis, in our cell culture facility. This bacterium originated from contaminated tap water pipes and spread via regular aseptic culture techniques due to survival of the bacterial spores in 70% ethanol. B brevis overgrew the cultures within a few days after seeding of the primary cells. Chlorine solution effectively killed this spore-forming bacterium. Both cases of contamination were identified using DNA sequencing which enabled the deployment of targeted aseptic techniques for the elimination of the persistent contamination.

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Contains fulltext : 216697.pdf (publisher's version ) (Closed access)

Contains fulltext : 229323.pdf (publisher's version ) (Open Access), Microbiota live in a closely regulated interaction with their environment, and vice versa. The presence and absence of microbial entities is greatly influenced by features of the niche in which they thrive. Characteristic of this phenomenon is that different human skin sites harbor niche-specific communities of microbes. Microbial diversity is considerable, and the current challenge lies in determining which microbes and (corresponding) functionality are of importance to a given ecological niche. Furthermore, as there is increasing evidence of microbial involvement in health and disease, the need arises to fundamentally understand microbiome processes for application in health care, nutrition and personal care products (e.g. diet, cosmetics, probiotics). This review provides a current overview of state-of-the-art sequencing-based techniques and corresponding data analysis methodology for profiling of complex microbial communities. Furthermore, we also summarize the existing knowledge regarding cutaneous microbiota and their human host for a wide range of skin diseases.

Contains fulltext : 220729.pdf (publisher's version ) (Open Access), The tumour microenvironment (TME) forms a major obstacle in effective cancer treatment and for clinical success of immunotherapy. Conventional co-cultures have shed light onto multiple aspects of cancer immunobiology, but they are limited by the lack of physiological complexity. We develop a human organotypic skin melanoma culture (OMC) that allows real-time study of host-malignant cell interactions within a multicellular tissue architecture. By co-culturing decellularized dermis with keratinocytes, fibroblasts and immune cells in the presence of melanoma cells, we generate a reconstructed TME that closely resembles tumour growth as observed in human lesions and supports cell survival and function. We demonstrate that the OMC is suitable and outperforms conventional 2D co-cultures for the study of TME-imprinting mechanisms. Within the OMC, we observe the tumour-driven conversion of cDC2s into CD14(+) DCs, characterized by an immunosuppressive phenotype. The OMC provides a valuable approach to study how a TME affects the immune system.

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