Changes in the expression of stem cell markers in oral lichen planus and hyperkeratotic lesions

Selection signatures for local and regional adaptation in Chinese Mongolian horse breeds reveal candidate genes for hoof health

BACKGROUND

Thousands of years of natural and artificial selection since the domestication of the horse has shaped the distinctive genomes of Chinese Mongolian horse populations. Consequently, genomic signatures of selection can provide insights into the human-mediated selection history of specific traits and evolutionary adaptation to diverse environments. Here, we used genome-wide SNPs from five distinct Chinese Mongolian horse populations to identify genomic regions under selection for the population-specific traits, gait, black coat colour, and hoof quality. Other global breeds were used to identify regional-specific signatures of selection.

RESULTS

We first identified the most significant selection peak for the Wushen horse in the region on ECA23 harbouring DMRT3, the major gene for gait. We detected selection signatures encompassing several genes in the Baicha Iron Hoof horse that represent good biological candidates for hoof health, including the CSPG4, PEAK1, EXPH5, WWP2 and HAS3 genes. In addition, an analysis of regional subgroups (Asian compared to European) identified a single locus on ECA3 containing the ZFPM1 gene that is a marker of selection for the major domestication event leading to the DOM2 horse clade.

CONCLUSIONS

Genomic variation at these loci in the Baicha Iron Hoof may be leveraged in other horse populations to identify animals with superior hoof health or those at risk of hoof-related pathologies. The overlap between the selection signature in Asian horses with the DOM2 selection peak raises questions about the nature of horse domestication events, which may have involved a prehistoric clade other than DOM2 that has not yet been identified.

A systematic summary of survival and death signalling during the life of hair follicle stem cells

Hair follicle stem cells (HFSCs) are among the most widely available resources and most frequently approved model systems used for studying adult stem cells. HFSCs are particularly useful because of their self-renewal and differentiation properties. Additionally, the cyclic growth of hair follicles is driven by HFSCs. There are high expectations for the use of HFSCs as favourable systems for studying the molecular mechanisms that contribute to HFSC identification and can be applied to hair loss therapy, such as the activation or regeneration of hair follicles, and to the generation of hair using a tissue-engineering strategy. A variety of molecules are involved in the networks that critically regulate the fate of HFSCs, such as factors in hair follicle growth and development (in the Wnt pathway, Sonic hedgehog pathway, Notch pathway, and BMP pathway), and that suppress apoptotic cues (the apoptosis pathway). Here, we review the life cycle, biomarkers and functions of HFSCs, concluding with a summary of the signalling pathways involved in HFSC fate for promoting better understanding of the pathophysiological changes in the HFSC niche. Importantly, we highlight the potential mechanisms underlying the therapeutic targets involved in pathways associated with the treatment of hair loss and other disorders of skin and hair, including alopecia, skin cancer, skin inflammation, and skin wound healing.

Composition of hemidesmosomes in basal keratinocytes of normal buccal mucosa and oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease displaying ultrastructural disturbances in epithelial hemidesmosomes. The expression of several key hemidesmosomal components in OLP as well as in normal buccal mucosa is, however, unknown. The aim of the study was therefore to examine intracellular and extracellular components involved in hemidesmosomal attachment, in OLP (n = 20) and in normal buccal mucosa (n = 10), by immunofluorescence. In normal buccal mucosa, laminin-α3γ2, integrin-α6β4, CD151, collagen α-1(XVII) chain, and dystonin showed linear expression along the basal membrane, indicating the presence of type I hemidesmosomes. Plectin stained most epithelial cell membranes and remained unphosphorylated at S4642. In OLP, most hemidesmosomal molecules examined showed disturbed expression consisting of discontinuous increases, apicolateral location, and/or intracellular accumulation. Plectin showed S4642-phosphorylation at the basement membrane, and deposits of laminin-α3 and laminin-γ2 were found within the connective tissue. The disturbed expression of hemidesmosomal proteins in OLP indicates deficient attachment of the basal cell layer, which can contribute to detachment and cell death of basal keratinocytes seen in the disease.

Expression of keratin 15 in dentigerous cyst, odontogenic keratocyst and ameloblastoma

The etiology and pathogenesis of odontogenic lesions are poorly understood. Keratin 15 (K15) is a type I cytoskeletal protein that provides structural support to the cells and has been considered to be a stem cell marker. The aim of the present study was to evaluate the expression of K15 in the epithelial lining of dentigerous cysts (DCs), odontogenic keratocysts (OKCs) and ameloblastomas (ABs). The study included 41 samples of DCs (n=13), OKCs (n=12), and AB tissues (n=16). K15 protein expression was evaluated via immunohistochemistry and data were statistically analyzed using a Kruskal-Wallis test. K15 was expressed in the majority of the studied lesions with various distributions in the different study samples. The Kruskal-Wallis test revealed non-significant differences in the expression of K15 among the three odontogenic lesions (P=0.380). The present study confirmed the high expression of K15 in the different epithelial layers of DC, OKC and AB. This type of expression excludes the reliability of regarding K15 as a stem cell marker in DC, OKC and AB. However, K15 may reflect the abnormal differentiation of pathological epithelial cells in these lesions.

A novel NOTCH3 mutation identified in patients with oral cancer by whole exome sequencing

Oral cancer is a serious disease caused by environmental factors and/or susceptible genes. In the present study, in order to identify useful genetic biomarkers for cancer prediction and prevention, and for personalized treatment, we detected somatic mutations in 5 pairs of oral cancer tissues and blood samples using whole exome sequencing (WES). Finally, we confirmed a novel nonsense single-nucleotide polymorphism (SNP; chr19:15288426A>C) in the NOTCH3 gene with sanger sequencing, which resulted in a N1438T mutation in the protein sequence. Using multiple in silico analyses, this variant was found to mildly damaging effects on the NOTCH3 gene, which was supported by the results from analyses using PANTHER, SNAP and SNPs&GO. However, further analysis using Mutation Taster revealed that this SNP had a probability of 0.9997 to be 'disease causing'. In addition, we performed 3D structure simulation analysis and the results suggested that this variant had little effect on the solubility and hydrophobicity of the protein and thus on its function; however, it decreased the stability of the protein by increasing the total energy following minimization (-1,051.39 kcal/mol for the mutant and -1,229.84 kcal/mol for the native) and decreasing one stabilizing residue of the protein. Less stability of the N1438T mutant was also supported by analysis using I-Mutant with a DDG value of -1.67. Overall, the present study identified and confirmed a novel mutation in the NOTCH3 gene, which may decrease the stability of NOTCH3, and may thus prove to be helpful in cancer prognosis.

Salivary levels of interleukin-8 in oral lichen planus and diabetic patients: A biochemical study

BACKGROUND

This study aimed to assess the salivary levels of interleukin-8 (IL-8) in oral lichen planus (OLP) and diabetes mellitus (DM) patients, and OLP + DM patients in comparison with healthy individuals.

MATERIALS AND METHODS

This descriptive cross-sectional study was conducted on 75 patients (30 with OLP, 5 with both OLP and DM, 20 with DM and 20 healthy controls). The salivary levels of IL-8 and fasting blood sugar and 2-h postprandial blood glucose levels were measured in all the subjects. Data were analyzed with one-way ANOVA and post hoc least significant difference tests.

RESULTS

The mean salivary level of IL-8 was the highest in OLP + DM patients, followed by DM, OLP and control groups, respectively. Pair-wise comparisons of the groups revealed significant differences in the salivary levels of IL-8 between OLP and control, DM and control, also OLP + DM patients and control (P < 0.05).

CONCLUSION

The increasing salivary level of IL-8 in the control, OLP, DM, OLP + DM groups, respectively, indicates the role of this inflammatory cytokine in the pathogenesis of OLP and diabetes.

Systems Toxicology Assessment of the Biological Impact of a Candidate Modified Risk Tobacco Product on Human Organotypic Oral Epithelial Cultures

Cigarette smoke (CS) has been reported to increase predisposition to oral cancer and is also recognized as a risk factor for many conditions including periodontal diseases, gingivitis, and other benign mucosal disorders. Smoking cessation remains the most effective approach for minimizing the risk of smoking-related diseases. However, reduction of harmful constituents by heating rather than combusting tobacco, without modifying the amount of nicotine, is a promising new paradigm in harm reduction. In this study, we compared effects of exposure to aerosol derived from a candidate modified risk tobacco product, the tobacco heating system (THS) 2.2, with those of CS generated from the 3R4F reference cigarette. Human organotypic oral epithelial tissue cultures (EpiOral, MatTek Corporation) were exposed for 28 min to 3R4F CS or THS2.2 aerosol, both diluted with air to comparable nicotine concentrations (0.32 or 0.51 mg nicotine/L aerosol/CS for 3R4F and 0.31 or 0.46 mg/L for THS2.2). We also tested one higher concentration (1.09 mg/L) of THS2.2. A systems toxicology approach was employed combining cellular assays (i.e., cytotoxicity and cytochrome P450 activity assays), comprehensive molecular investigations of the buccal epithelial transcriptome (mRNA and miRNA) by means of computational network biology, measurements of secreted proinflammatory markers, and histopathological analysis. We observed that the impact of 3R4F CS was greater than THS2.2 aerosol in terms of cytotoxicity, morphological tissue alterations, and secretion of inflammatory mediators. Analysis of the transcriptomic changes in the exposed oral cultures revealed significant perturbations in various network models such as apoptosis, necroptosis, senescence, xenobiotic metabolism, oxidative stress, and nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) signaling. The stress responses following THS2.2 aerosol exposure were markedly decreased, and the exposed cultures recovered more completely compared with those exposed to 3R4F CS.

Serum level of Interleukin-8 in subjects with diabetes, diabetes plus oral lichen planus, and oral lichen planus: A biochemical study

BACKGROUND

Correlation between diabetes mellitus (DM) and oral lichen planus (OLP) seems probable. Since Interleukin-8 (IL-8) is an important inflammatory mediator involved in both conditions, this study aimed to measure and compare the serum level of IL-8 in DM, OLP, and DM + OLP patients in comparison with healthy individuals.

MATERIALS AND METHODS

This cross sectional study was conducted on 75 patients (30 OLP, 5 OLP and type II DM, 20 type II DM, and 20 healthy controls). Serum levels of IL-8, fasting blood sugar (FBS) and 2-h postprandial blood sugar were measured in the four groups. Data were analyzed using SPSS version 20 by one-way ANOVA and post_hocleast significant difference test.

RESULTS

Type II DM patients with OLP had the highest mean serum level of IL-8 followed by OLP, DM and control groups, respectively. Pairwise comparison of groups revealed significant differences in serum IL-8 between the control and OLP and also control and OLP+DM (P < 0.05) groups. No other significant differences were noted. The mean levels of FBS and 2-h postprandial blood sugar were the highest in OLP+DM patients followed by DM, OLP and control groups, respectively.

CONCLUSION

The ascending trend of serum level of IL-8 in the control, DM, OLP, and DM+OLP patients may indicate the role of this factor in the pathogenesis of DM and OLP. Moreover, it may play a synergistic role in patients suffering from both conditions.

Differential expression of stem cell-like proteins in normal, hyperplastic and dysplastic oral epithelium

Objective

The identification of stem cells (SC) remains challenging. In the human oral mucosal epithelium, these cells are believed to be in the basal layer (stem cell niche), but their exact location is unclear. The aim of this study was to examine the dysplastic oral epithelium for these SC-like proteins in order to assess their diagnostic value as biomarkers complementing the histological grading of dysplasia.

Material and Methods

Thirty oral epithelial dysplasia (OED), 25 oral lichen planus (OLP), 10 oral hyperkeratosis and 5 normal oral epithelium (OE) were immunohistochemically examined for four SC markers [integrin β1, neuron-glial-2 (NG2), notch 1 (N1) and keratin 15 (K15)].

Results

Three of four SC markers were heterogeneously detected in all samples. K15 overexpression in the lower two-thirds of severe OED suggests an expanded SC niche. Integrin β1 distribution pattern was not measurably different between OEDs and control. NG2 was almost negative to absent in all samples examined. N1 expression was weak and highly variable in normal and dysplastic epithelium, making it an unreliable epithelial stem cell marker.

Conclusions

Present findings suggest that these markers were unable to identify individual epithelial stem cells. Instead, subpopulations of cells, most probably stem cells and transit amplifying cells with stem cell-like properties were identified in the dysplastic oral epithelium. The characteristic expressions of K15 might be of diagnostic value for oral dysplasia and should be investigated further.

Dormancy activation mechanism of oral cavity cancer stem cells

Radiotherapy and chemotherapy are targeted primarily at rapidly proliferating cancer cells and are unable to eliminate cancer stem cells in the G0 phase. Thus, these treatments cannot prevent the recurrence and metastasis of cancer. Understanding the mechanisms by which cancer stem cells are maintained in the dormant G0 phase, and how they become active is key to developing new cancer therapies. The current study found that the anti-cancer drug 5-fluorouracil, acting on the oral squamous cell carcinoma KB cell line, selectively killed proliferating cells while sparing cells in the G0 phase. Bisulfite sequencing PCR showed that demethylation of the Sox2 promoter led to the expression of Sox2. This then resulted in the transformation of cancer stem cells from the G0 phase to the division stage and suggested that the transformation of cancer stem cells from the G0 phase to the division stage is closely related to an epigenetic modification of the cell.

Novel collagen membranes for the reconstruction of the corneal surface

No standardized biomaterial exists for the surgical treatment of persistent corneal erosions and ulcerations. We analyzed the suitability and biocompatibility of defined noncross-linked and UV/riboflavin cross-linked equine type I collagen membranes for the reconstruction of the corneal surface. Isolated human oral mucosa epithelial cells, a cell type in clinical use for the treatment of ocular surface diseases, were subcultivated on both types of membranes and examined concerning cell adhesion, proliferation, and differentiation. Biocompatibility was evaluated following superficial and intrastromal corneal transplantation in New Zealand white rabbits. In cell cultures all collagen membranes supported adhesion of oral mucosa epithelial cells leading to the formation of multilayered epithelial cell sheets. After intrastromal corneal implantation clinical signs of degradation were seen in all variants of collagen membranes, which was fastest in noncross-linked variants. The histological and ultrastructural level invasion of keratocytes and production of new collagen fibers inside the collagen membranes could be detected in noncross-linked variants. After superficial corneal implantation covering of the membranes by corneal epithelium over time was visible. Ultrastructural analysis showed a slower rate of degradation and less invading keratocytes in cross-linked variants compared with noncross-linked collagen membranes. Cross-linked and noncross-linked variants of the collagen membrane proofed to be suitable to serve as a carrier for epithelial stem cells in vitro and showed a high biocompatibility in vivo. These results indicate that the tested collagen membranes might be suitable for the reconstruction of the corneal surface in patients with nonhealing ulcerations. Whether membranes with faster or slower degradation properties are preferable for the treatment of persistent corneal ulcerations might depend on the underlying corneal pathology and the degree of concomitant inflammation.

Keratin k15 as a biomarker of epidermal stem cells

Keratin 15 (K15) is type I keratin protein co-expressed with the K5/K14 pair present in the basal keratinocytes of all stratified epithelia. Although it is a minor component of the cytoskeleton with a variable expression pattern, nonetheless its expression has been reported as a stem cell marker in the bulge of hair follicles. Conversely, suprabasal expression of K15 has also been reported in both normal and diseased tissues, which is inconsistent with its role as a stem cell marker. Our recently published work has given evidence of the molecular pathways that seem to control the expression of K15 in undifferentiated and differentiated cells. In this article, we have critically reviewed the published work to establish the reliability of K15 as an epidermal stem cell marker.

Applications of stem cells in interdisciplinary dentistry and beyond: an overview

In medicine stem cell–based treatments are being used in conditions like Parkinson's disease, neural degeneration following brain injury, cardiovascular diseases, diabetes, and autoimmune diseases. In dentistry, recent exciting discoveries have isolated dental stem cells from the pulp of the deciduous and permanent teeth, from the periodontal ligament, and an associated healthy tooth structure, to cure a number of diseases. The aim of the study was to review the applications of stem cells in various fields of dentistry, with emphasis on its banking, and to understand how dental stem cells can be used for regeneration of oral and non-oral tissues conversely. A Medline search was done including the international literature published between 1989 and 2011. It was restricted to English language articles and published work of past researchers including in vitro and in vivo studies. Google search on dental stem cell banking was also done. Our understanding of mesenchymal stem cells (MSC) in the tissue engineering of systemic, dental, oral, and craniofacial structures has advanced tremendously. Dental professionals have the opportunity to make their patients aware of these new sources of stem cells that can be stored for future use, as new therapies are developed for a range of diseases and injuries. Recent findings and scientific research articles support the use of MSC autologously within teeth and other accessible tissue harvested from oral cavity without immunorejection. A future development of the application of stem cells in interdisciplinary dentistry requires a comprehensive research program.

Oral epithelial stem cells in tissue maintenance and disease: the first steps in a long journey

The identification and characterization of stem cells is a major focus of developmental biology and regenerative medicine. The advent of genetic inducible fate mapping techniques has made it possible to precisely label specific cell populations and to follow their progeny over time. When combined with advanced mathematical and statistical methods, stem cell division dynamics can be studied in new and exciting ways. Despite advances in a number of tissues, relatively little attention has been paid to stem cells in the oral epithelium. This review will focus on current knowledge about adult oral epithelial stem cells, paradigms in other epithelial stem cell systems that could facilitate new discoveries in this area and the potential roles of epithelial stem cells in oral disease.

Multiple drug resistant, tumorigenic stem-like cells in oral cancer

An in vitro cell line model was established to exemplify tumor stem cell concept in oral cancer. We were able to identify CD147 expressing fractions in SCC172 OSCC cell line with differing Hoechst dye efflux activity and DNA content. In vivo tumorigenic assay revealed three fractions enriched with stem-like cells capable of undergoing mesenchymal transition and a non-tumorigenic fraction. The regeneration potential and transition of one fraction to other imitated the phenotypic switch and functional disparities evidenced during oral tumor progression. Knowledge of these additional stem-like subsets will improve understanding of stem cell based oral epithelial tumor progression from normal to malignant lesions.

Redefining the potential applications of dental stem cells: An asset for future

Recent exciting discoveries isolated dental stem cells from the pulp of the primary and permanent teeth, from the periodontal ligament, and from associated healthy tissues. Dental pulp stem cells (DPSCs) represent a kind of adult cell colony which has the potent capacity of self-renewing and multilineage differentiation. Stem cell-based tooth engineering is deemed as a promising approach to the making of a biological tooth (bio-tooth) or engineering of functional tooth structures. Dental professionals have the opportunity to make their patients aware of these new sources of stem cells that can be stored for future use as new therapies are developed for a range of diseases and injuries. The aim of this article is to review and understand how dental stem cells are being used for regeneration of oral and conversely nonoral tissues. A brief review on banking is also done for storing of these valuable stem cells for future use.

Two mechanisms regulate keratin K15 expression in keratinocytes: role of PKC/AP-1 and FOXM1 mediated signalling

Background

Keratin 15 (K15) is a type I keratin that is used as a marker of stem cells. Its expression is restricted to the basal layer of stratified epithelia, and the bulge in hair follicles. However, in certain clinical situations including oral lichen planus, K15 is induced in suprabasal layers, which is inconsistent with the role of a stem cell marker. This study provides insights into the mechanisms of K15 expression in the basal and differentiating keratinocytes.

Methodology/Principal Findings

Human keratinocytes were differentiated by three different methods; suspension in methylcellulose, high cell density and treatment with phorbol ester. The expression of mRNA was determined by quantitative PCR and protein by western blotting and immunostaining. Keratinocytes in suspension suppressed β1-integrin expression, induced differentiation-specific markers and K15, whereas FOXM1 (a cell cycle regulated protein) and K14 were downregulated. Rescuing β1-integrin by either fibronectin or the arginine-glycine-aspartate peptide suppressed K15 but induced K14 and FOXM1 expression. Specific inhibition of PKCδ, by siRNA, and AP-1 transcription factor, by TAM67 (dominant negative c-Jun), suppressed K15 expression, suggesting that PKC/AP-1 pathway plays a role in the differentiation-specific expression of K15. The basal cell-specific K15 expression may involve FOXM1 because ectopic expression of the latter is known to induce K15. Using chromatin immunoprecipitation, we have identified a single FOXM1 binding motif in the K15 promoter.

Conclusions/Significance

The data suggests that K15 is induced during terminal differentiation mediated by the down regulation of β1-integrin. However, this cannot be the mechanism of basal/stem cell-specific K15 expression in stratified epithelia, because basal keratinocytes do not undergo terminal differentiation. We propose that there are two mechanisms regulating K15 expression in stratified epithelia; differentiation-specific involving PKC/AP-1 pathway, and basal-specific mediated by FOXM1, and therefore the use of K15 expression as a marker of stem cells must be viewed with caution.

Adult human buccal epithelial stem cells: identification, ex-vivo expansion, and transplantation for corneal surface reconstruction

PURPOSE

To identify adult human buccal epithelial stem cells (SCs) on the basis of two parameters (high p63 expression and greater nucleus/cytoplasmic (N/C) ratio) and to evaluate clinical efficacy of ex-vivo expanded autologous epithelium in bilateral limbal SC-deficient (LSCD) patients.

METHODS

The epithelial cells were isolated from buccal biopsy and cultured on human amnion in culture inserts with 3T3 feeder layer. The SCs were identified on the basis of two-parameter analysis using confocal microscopy, surface markers, and colony-forming efficiency (CFE). The cultured epithelium was transplanted in 10 LSCD patients followed by penetrating keratoplasty in 4 patients. The clinical outcome was followed up to 3 years.

RESULTS

A distinct population (3.0±1.7%) of small cells expressing high levels of p63 with greater N/C ratio was observed in buccal epithelium. The N/C ratio was found to be more appropriate than cell diameter for two-parameter analysis. These cells located in the basal layer were negative for connexin-43 and positive for melanoma-associated chondroitin sulfate proteoglycan, containing holoclones with 0.2% CFE, thus representing the SC population. After transplantation of cultured epithelium with increased (sixfold) SC content, anatomical and visual improvement was observed at 13-34 months in 3/10 LSCD patients.

CONCLUSIONS

The two-parameter SC marker is useful to identify and quantify buccal epithelial SCs. The transplantation of bioengineered SC-rich buccal epithelium is a strategy for corneal surface reconstruction in bilateral LSCD. However, further studies are required to optimize the culture conditions and to look for other sources of adult SCs for better visual outcome.

Functional and clinical relevance of chondroitin sulfate proteoglycan 4

The lack of effective conventional therapies for the treatment of advanced stage melanoma has stimulated interest in the development of novel strategies for the management of patients with malignant melanoma. Among them, immunotherapy has attracted much attention because of the potential role played by immunological events in the clinical course of melanoma. For many years, T cell-based immunotherapy has been emphasized in part because of the disappointing results of the monoclonal antibody (mAb)-based clinical trials conducted in the early 1980s and in part because of the postulated major role played by T cells in tumor growth control. More recently, mAb-based therapies have gained in popularity given their clinical and commercial success for a variety of malignant diseases. As a result, there has been increased interest in identifying and characterizing antibody-defined melanoma antigens. Among them, the chondroitin sulfate proteoglycan 4 (CSPG4), also known as high molecular weight-melanoma associated antigen (HMW-MAA) or melanoma chondroitin sulfate proteoglycan (MCSP), has attracted much attention in recent years because of the growing experimental evidence that it fulfills two requirements for immunotherapy to be therapeutically effective: (1) targeting of cancer stem cells (CSC) and (2) development of combinatorial therapies to counteract the escape mechanisms driven by the genetic instability of tumor cells. With this in mind, in this chapter, we have reviewed recent information related to the distribution of CSPG4 on various types of tumors, including CSC, its expression on pericytes in the tumor microenvironment, its recognition by T cells, its role in cell biology as well as the potential mechanisms underlying the ability of CSPG4-specific immunity to control malignant cell growth.

The stem cell code in oral epithelial tumorigenesis: 'the cancer stem cell shift hypothesis'

Tumors of the oral cavity provide an ideal model to study various stages of epithelial tumor progression. A group of cancer cells termed cancer stem cells (CSCs) eludes therapy, persists and initiates recurrence augmenting malignant spread of the disease. Hitherto, accurate identification and separation of such minimal residual cells have proven futile due to lack of identifiable traits to single out these cells from the heterogeneous tumor bulk. In this review we have compiled comprehensive evidence from comparative phenotypic and genotypic studies on normal oral mucosa as well as tumors of different grades to elucidate that differential expression patterns of putative stem cells markers may identify 'minimal residual disease' in oral squamous cell carcinoma. We propose the "cancer stem cell shift hypothesis" to explain the exact identity and switch-over, tumor-promoting mechanisms adapted by putative CSCs with correlation to tumor staging.