Multi-species oral biofilm promotes reconstructed human gingiva epithelial barrier function

Abstract

Since the oral mucosa is continuously exposed to abundant microbes, one of its most important defense features is a highly proliferative, thick, stratified epithelium. The cellular mechanisms responsible for this are still unknown. The aim of this study was to determine whether multi-species oral biofilm contribute to the extensive stratification and primed antimicrobial defense in epithelium. Two in vitro models were used: 3D reconstructed human gingiva (RHG) and oral bacteria representative of multi-species commensal biofilm. The organotypic RHG consists of a reconstructed stratified gingiva epithelium on a gingiva fibroblast populated hydrogel (lamina propria). Biofilm was cultured from healthy human saliva, and consists of typical commensal genera Granulicatella and major oral microbiota genera Veillonella and Streptococcus. Biofilm was applied topically to RHG and host–microbiome interactions were studied over 7 days. Compared to unexposed RHG, biofilm exposed RHG showed increased epithelial thickness, more organized stratification and increased keratinocyte proliferation. Furthermore biofilm exposure increased production of RHG anti-microbial proteins Elafin, HBD2 and HBD3 but not HBD1, adrenomedullin or cathelicidin LL-37. Inflammatory and antimicrobial cytokine secretion (IL-6, CXCL8, CXCL1, CCL20) showed an immediate and sustained increase. In conclusion, exposure of RHG to commensal oral biofilm actively contributes to RHG epithelial barrier function.

Biology of soft tissue repair: gingival epithelium in wound healing and attachment to the tooth and abutment surface

“…Taken together, these data suggest that oral mucosa epithelium is intrinsically primed to repair through different mechanisms from that observed in skin, but the large number of epithelial cell layers characteristic of many types of oral mucosa subject to extreme mechanical load and pathogen exposure is most probably regulated by extrinsic factors in the microenvironment. Indeed, Shang et al (2018) have recently shown that commensal oral biofilm has a beneficial influence on oral mucosa barrier function by increasing keratinocyte proliferation, stratification and expression of host-defence proteins.…”

“…, when comparing oral commensal and pathogenic biofilms, observed that the pathogenic biofilm supresses the innate immune response (inflammatory cytokine release), suggesting that an early immune evasion is taking place in the organotypic gingival mucosa tissue equivalents. Furthermore, Shang et al (2018), using gingival tissue equivalents, showed that a commensal multi-species oral biofilm promotes an organised epithelial stratification and oral barrier function by increasing epithelial cell layers' number, cell proliferation and expression of host anti-microbial protein expression [elafin, human beta defensin (HBD) 2 and HBD3).…”

Nanoparticles for the Treatment of Oral Biofilms: Current State, Mechanisms, Influencing Factors, and Prospects

“…The formation of oral biofilms can provide protected microenvironments for microbial communities at different colonization sites, along with the establishment of an oral microecology. It is undeniable that both a stable ecological environment and the diversity of oral microecology have positive effects on maintaining oral health and oral mucosal barriers, and reach a symbiotic relation with the host. When examining any antibacterial material for the control of oral biofilm‐related diseases, it is important to focus on its possible effects on oral microecology, and to eliminate one‐sided thinking that only focuses on its antibacterial properties.…”

“…When studying the antioral biofilm properties of nanoparticles, it is not advisable to ignore the possible adverse effects on oral microecology and only examine the ability to kill bacteria. Studies have shown that microbial communities in the oral cavity may have a beneficial effect on oral mucosal barriers . At the same time, the diversity of an oral biofilm microecology has a positive effect on maintaining oral health.…”

“…A multispecies model simply mixes a variety of bacteria together, but the arrangement is not orderly . A mixed‐species model ignores the effect of differences between in vitro biofilm carrier materials and in situ substrates in the oral cavity on biofilm performance. In addition, the repeatability of these methods is poor because the oral environment varies between individuals, and these differences are difficult to control using models .…”