Aggregatibacter actinomycetemcomitans Biofilm Reduces Gingival Epithelial Cell Keratin Expression in an Organotypic Gingival Tissue Culture Model

Abstract

Epithelial cells express keratins, which are essential for the structural integrity and mechanical strength of the cells. In the junctional epithelium (JE) of the tooth, keratins such as K16, K18, and K19, are expressed, which is typical for non-differentiated and rapidly dividing cells. The expression of K17, K4, and K13 keratins can be induced by injury, bacterial irritation, smoking, and inflammation. In addition, these keratins can be found in the sulcular epithelium and in the JE. Our aim was to estimate the changes in K4, K13, K17, and K19 expression in gingival epithelial cells exposed to Aggregatibacter actinomycetemcomitans. An organotypic gingival mucosa and biofilm co-culture was used as a model system. The effect of the biofilm after 24 h was assessed using immunohistochemistry. The structure of the epithelium was also studied with transmission electron microscopy (TEM). The expression of K17 and K19, as well as total keratin expression, decreased in the suprabasal layers of epithelium, which were in close contact with the A. actinomycetemcomitans biofilm. The effect on keratin expression was biofilm specific. The expression of K4 and K13 was low in all of the tested conditions. When stimulated with the A. actinomycetemcomitans biofilm, the epithelial contact site displayed a thick necrotic layer on the top of the epithelium. The A. actinomycetemcomitans biofilm released vesicles, which were found in close contact with the epithelium. After A. actinomycetemcomitans irritation, gingival epithelial cells may lose their resistance and become more vulnerable to bacterial infection.

Editorial Comments to the Special Issue: “Aggregatibacter actinomycetemcomitans—Gram-Negative Bacterial Pathogen”

“…Their data demonstrate that toxin-induced apoptosis is dependent upon increased levels of specific intracellular signaling, and conclude that that the ability of CDT to impair lymphocyte proliferation and promote cell death therefore compromises the host response to CDT-producing organisms. The effect of A. actinomycetemcomitans on epithelial cells has also been examined in a paper of this Special Issue [ 13 ]. Beklen and collaborators show that A. actinomycetemcomitans biofilms release outer membrane vesicles, which can be found in close contact with the epithelium.…”

Stable reconstructed human gingiva–microbe interaction model: Differential response to commensals and pathogens

“…Literature reviews describing work from other groups show that the few studies performed mainly report RHG exposed to a single- or dual-species of oral bacteria for maximally 48 hours ( Dongari-Bagtzoglou and Kashleva, 2006 ; Tabatabaei et al., 2020 ). Most of these reports described a disrupted tissue integrity, decreased viability and increase in apoptosis of host tissues within 48 hours ( Andrian et al., 2004 ; Gursoy et al., 2010 ; de Carvalho Dias et al., 2018 ; Morse et al., 2018 ; Beklen et al., 2019 ). One report described a model where a multi-species biofilm was co-incubated with RHG for 3 days without affecting the viability of RHG ( De Ryck et al., 2014 ).…”

The Three-Dimensional In Vitro Cell Culture Models in the Study of Oral Cancer Immune Microenvironment

“…Various types of cells were used as host cell sources in 3D oral host-microbe interaction models, including cancer cell lines [195,196], immortalized cell lines [197,198], and primary cells [186,199]. Studies utilizing these different cell sources showed similar outcomes when exposed to specific microbes, such as Candida albicans, in terms of tissue histology, Lactate dehydrogenase (LDH release), Human beta-defensin-2 (hBD2) expression, and secretions of TNF-α, IL-1β, and CXCL-8 [200].…”

“…Another study suggested a slightly higher invasion of Porphyromonas gingivalis occurred in 3D models using the H357 cell line (Human oral squamous cell carcinoma) compared to primary keratinocytes, but the difference was not significant [201]. Various types of cells were used as host cell sources in 3D oral host-microbe interaction models, including cancer cell lines [195,196], immortalized cell lines [197,198], and primary cells [186,199]. Studies utilizing these different cell sources showed similar outcomes when exposed to specific microbes, such as Candida albicans, in terms of tissue histology, Lactate dehydrogenase (LDH release), Human beta-defensin-2 (hBD2) expression, and secretions of TNF-α, IL-1β, and CXCL-8 [200].…”