Human gingival mucosal keratinocytes exhibiting anchorage-independent growth express increased inducible nitric oxide synthase: regulation by MAP kinases

Molecular Research on Oral Diseases and Related Biomaterials: A Journey from Oral Cell Models to Advanced Regenerative Perspectives

Oral diseases such as gingivitis, periodontitis, and oral cancer affect millions of people worldwide. Much research has been conducted to understand the pathogenetic mechanisms of these diseases and translate this knowledge into therapeutics. This review aims to take the reader on a journey from the initial molecular discoveries to complex regenerative issues in oral medicine. For this, a semi-systematic literature search was carried out in Medline and Web of Science databases to retrieve the primary literature describing oral cell models and biomaterial applications in oral regenerative medicine. First, an in vitro cell model of gingival keratinocytes is discussed, which illustrates patho- and physiologic principles in the context of oral epithelial homeostasis and carcinogenesis and represents a cellular tool to understand biomaterial-based approaches for periodontal tissue regeneration. Consequently, a layered gradient nonwoven (LGN) is described, which demonstrates that the key features of biomaterials serve as candidates for oral tissue regeneration. LGN supports proper tissue formation and obeys the important principles for molecular mechanotransduction. Furthermore, current biomaterial-based tissue regeneration trends, including polymer modifications, cell-based treatments, antimicrobial peptides and optogenetics, are introduced to represent the full spectrum of current approaches to oral disease mitigation and prevention. Altogether, this review is a foray through established and new concepts in oral regenerative medicine and illustrates the process of knowledge translation from basic molecular and cell biological research to future clinical applications.

Demethoxycurcumin from Curcuma longa rhizome suppresses iNOS induction in an in vitro inflamed human intestinal mucosa model

BACKGROUND

It is known that inducible nitric oxide synthase (iNOS)/nitric oxide (NO) plays an integral role during intestinal inflammation, an important factor for colon cancer development. Natural compounds from Curcuma longa L. (Zingiberaceae) have long been a potential source of bioactive materials with various beneficial biological functions. Among them, a major active curcuminoid, demethoxycurcumin (DMC) has been shown to possess anti-inflammatory properties in lipopolysaccharide (LPS)-activated macrophages or microglia cells. However, the role of DMC on iNOS expression and NO production in an in vitro inflamed human intestinal mucosa model has not yet been elucidated. This study concerned inhibitory effects on iNOS expression and NO production of DMC in inflamed human intestinal Caco-2 cells. An in vitro model was generated and inhibitory effects on NO production of DMC at 65 μM for 24-96 h were assessed by monitoring nitrite levels. Expression of iNOS mRNA and protein was also investigated. DMC significantly decreased NO secretion by 35-41% in our inflamed cell model. Decrease in NO production by DMC was concomitant with down-regulation of iNOS at mRNA and protein levels compared to proinflammatory cytokine cocktail and LPS-treated controls. Mechanism of action of DMC may be partly due to its potent inhibition of the iNOS pathway. Our findings suggest that DMC may have potential as a therapeutic agent against inflammation-related diseases, especially in the gut.

Study designs to investigate Nox1 acceleration of neoplastic progression in immortalized human epithelial cells by selection of differentiation resistant cells

To investigate the role of NADPH oxidase homolog Nox1 at an early step of cell transformation, we utilized human gingival mucosal keratinocytes immortalized by E6/E7 of human papillomavirus (HPV) type 16 (GM16) to generate progenitor cell lines either by chronic ethanol exposure or overexpression with Nox1. Among several cobblestone epithelial cell lines obtained, two distinctive spindle cell lines - FIB and NuB1 cells were more progressively transformed exhibiting tubulogenesis and anchorage-independent growth associated with increased invasiveness. These spindle cells acquired molecular markers of epithelial mesenchymal transition (EMT) including mesenchymal vimentin and simple cytokeratins (CK) 8 and 18 as well as myogenic alpha-smooth muscle actin and caldesmon. By overexpression and knockdown experiments, we showed that Nox1 on a post-translational level regulated the stability of CK18 in an ROS-, phosphorylation- and PKCepilon-dependent manner. PKCepilon may thus be used as a therapeutic target for EMT inhibition. Taken together, Nox1 accelerates neoplastic progression by regulating structural intermediate filaments leading to EMT of immortalized human gingival epithelial cells.

Discrimination of epithelium-like and fibroblast-like phenotypes derived from ethanol-treated immortalised human gingival keratinocytes in epithelial equivalents

Ethanol treatment of immortalised human gingival keratinocytes (IHGK) yields in an epithelium-like (EPI) and fibroblast-like (FIB) phenotype. With respect to the stratified gingival epithelium, putative structural and molecular differences assigning cells to these phenotypes have not, to date, been analysed in a three-dimensional tissue/epithelial context. Therefore, we generated epithelial equivalents (EEs) in organotypic co-cultures of IHGK, EPI and FIB cells for 1 and 2 weeks and conducted protein and gene expression studies on the EEs for epithelial biomarkers including keratin K14, integrin subunits alpha6 and beta1, E-cadherin, and mesenchymal vimentin. As in the EEs of IHGK and EPI, indirect immunofluorescence revealed continuous expression of beta1 integrin in EEs of FIB cells. However, FIB cells exhibited a significant down-regulation in K14 and integrin alpha6 protein and a loss of E-cadherin at week 2, whereas vimentin was increased. FIB EEs were devoid of transcripts for E-cadherin at both time points, although transcription of the other genes remained constant in all phenotypes. Thus, the FIB phenotype exhibited a poor epithelial structure coinciding with disturbances in the expression of epithelial biomarkers and the persistence of mesenchymal vimentin. Transcription analysis revealed post-transcriptional regulation of vimentin in IHGK and EPI and of K14 and alpha6 in FIB cells. Our findings indicate that differences in the epithelial integrity and expression of molecules in EEs allow for the discrimination of EPI and FIB cells. This suggests that FIB cells share features of epithelial-mesenchymal transition and reflect a more progressive stage in epithelial cell transformation.