Distinct Variations in Gene Expression and Cell Composition across Lichen Planus Subtypes.

Lichen planus (LP) is a highly prevalent inflammatory skin disease. While various clinical subtypes have been defined, detailed comparisons of these variants are lacking. This study aimed to elucidate differences in gene expression and cellular composition across LP subtypes. Lesional skin biopsies from 28 LP patients (classical, oral, genital, and lichen planopilaris) and seven non-diseased skin controls (NDC) were analyzed. Gene expression profiling of 730 inflammation-related genes was conducted using NanoString. Immune cell compositions were assessed by multiplex immunohistochemistry. Gene expression profiles revealed unique inflammatory signatures for each LP subtype. Lichen planopilaris exhibited the most divergence, with downregulated gene expression and upregulation of complement pathway genes (C5-7), along with elevated M2 macrophages. Oral and genital LP demonstrated similar profiles with strong upregulation of TNF-related and Toll-like receptor-associated genes. Oral LP showed the highest upregulation of cytotoxicity-associated genes, as well as high numbers of CD8+ IL-17A+ (Tc17) cells (8.02%). Interferon gene signatures were strongly upregulated in oral and classical LP. The study highlights distinct differences in inflammatory gene expression and cell composition across LP subtypes, emphasizing the need for tailored therapeutic approaches.

YAP1 Expression in Lichen Planus and Squamous Cell Carcinoma: Role in Disease Pathogenesis and Potential Therapeutic Target.

BACKGROUND: Lichen planus (LP), especially oral type, reported a potential risk of malignant transformation to squamous cell carcinoma (SCC). Yes-Associated Protein (YAP1), a key component of the Hippo pathway, acts as a transcription cofactor regulating expression of genes involved in cell proliferation, apoptosis, and migration. Therefore, it has been implicated in carcinogenesis of a wide variety of human cancers. OBJECTIVES: To study YAP1 expression in LP and SCC in comparison to normal control (NC) specimens. PATIENTS AND METHODS: This study was conducted on 50 NC specimens, 50 LP specimens, and 50 SCC specimens. They were categorized into 2 main groups; cutaneous (25 NC, 25 LP, 25 SCC), and oral (25 NC, 25 LP, 25 SCC). All specimens were examined for YAP1 antibody expression by immunohistochemistry and YAP1 mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: In both cutaneous and oral groups; significant upregulation of YAP1 expressions was observed in SCC specimens followed by LP and then NC specimens in the same sequence. Its expression in SCC was found to be significantly higher in poorly and moderately differentiated types than well differentiated types. CONCLUSION: YAP1 may have a potential role in the pathogenesis of LP and oncogenesis and progression of SCC. Moreover, it could be considered as a novel therapeutic target for such cases.

Evaluation of correlation between transcription factors and IL-17 in oral and cutaneous lichen planus lesions and Leukocytes.

BACKGROUND: Lichen planus (LP) is a chronic autoimmune disease with different clinical subtypes including cutaneous LP (CLP) and oral LP (OLP). We aimed to compare mRNA expression of RORγt and IL-17 in paraffin-embedded blocks of OLP and CLP lesions with normal oral mucosa (NOM), and also its correlation with hematologic parameters. MATERIALS & METHODS: This study included 89 paraffin-embedded blocks contain OLP (44 cases), CLP (45 cases) and NOM from the archive of Mashhad University of Medical Sciences, Mashhad, Iran. The expression of RORγt and IL-17 was evaluated by Real-time RT-PCR method. The result was compared to Leukocyte counts and the other hematological parameters of studied patients. RESULTS: The results of our study showed IL-17 and RORγt expression in OLP lesions were significantly higher than CLP and NOM groups (P = 0.001). Although we found high expression of RORγt and IL-17 in erosive OLP in compared to classic OLP lesion, but this increment was not significant for IL-17 (P = 0.26) and RORγt (P = 0.14). Further, Leukocyte and monocyte counts were substantially high in OLP group in compared to the CLP and NOM groups (P < 0.05). CONCLUSIONS: We concluded that increased expression of RORγt and IL-17 in LP lesions could play role in the pathogenesis of LP. As well, higher expression of RORγt and IL-17 in oral LP more than cutaneous LP might be associated with difference in clinical behavior of the two types of disease and role of these factors in premalignant behavior of OLP lesions.

Possible Relation between Vitamin D and Interleukin-17 in the Pathogenesis of Lichen Planus.

BACKGROUND: Lichen planus (LP) is a chronic autoimmune inflammatory mucocutaneous disease. Interleukin (IL)-17 is the signature cytokine of T-helper 17 cells, involved in the aetiology of many autoimmune and inflammatory disorders. Vitamin D has an immune-regulatory role and suppresses IL-17 production via direct transcriptional inhibition of IL-17 gene expression. OBJECTIVE: To explore the relationship of IL-17 and vitamin D levels with LP, and the possible inter-relationship between IL-17 and vitamin D. METHODS: The study enrolled 30 patients with LP and 30 healthy controls. Blood samples and skin biopsies were taken from all participants for evaluation of serum vitamin D, and serum and tissue IL-17 levels using enzyme-linked immunosorbent assay (ELISA). RESULTS: Patients had significantly higher serum and tissue IL-17 (p < 0.001 for both), as well as significantly lower serum vitamin D levels and more deficient patterns of vitamin D status than controls (p < 0.001 for both). In the patient group, there was a statistically significant positive correlation between extent of the disease and serum IL-17. There was no direct statistical correlation between IL-17 levels and serum vitamin D in either patients or controls. CONCLUSION: This study confirms a previously suggested role of IL-17 in the pathogenesis of LP and suggests its relation to the extent and severity of the disease. We also found an association between vitamin D deficiency and LP. However, a direct relationship between IL-17 and vitamin D deficiency could not be clarified.

"Normal-appearing" scalp areas are also affected in lichen planopilaris and frontal fibrosing alopecia: An observational histopathologic study of 40 patients.

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are lymphocyte-mediated scarring alopecias which clinically affect primarily the anterior and mid-scalp. However, unaffected scalp areas have not yet been investigated in a systemic manner. In this study, we assessed histopathologic changes in affected and unaffected scalp in both diseases and healthy control subjects and compared these findings with clinical signs and scalp symptoms. We have demonstrated that "normal-appearing" scalp that is devoid of clinical lesions of LPP and FFA showed lymphocytic perifollicular inflammation around the isthmus/infundibulum areas in 65% of biopsy specimens, perifollicular fibrosis in 15% and mucin deposits in 7.5% of the cases. None of these findings were found in control samples. No direct correlation was found between the degree of histopathological inflammation, scalp symptoms and clinical lesions in the corresponding affected scalp areas. This preliminary study suggests that both diseases may be more generalized processes which affect the scalp and therefore need systemic or total scalp therapy.

A proposed mechanism for central centrifugal cicatricial alopecia.

Central centrifugal cicatricial alopecia (CCCA) has an unknown mechanism. Analyzing other scarring diseases (lichen planopilaris, fibrotic kidney disease and scleroderma) may help to clarify the mechanism of scarring in CCCA. These diseases were chosen for comparison due to either their location of disease (skin or scalp specifically), or prominence in patients of African descent. Genetics, possible triggers, an autoimmune lymphocytic response, and epithelial to mesenchymal transition are potentially involved. Possible common pathways in scarring diseases and a better understanding of the CCCA mechanism will lead to further research into the pathogenesis and potential treatments of CCCA.

IL-17-positive mast cell infiltration in the lesional skin of lichen planopilaris: Possible role of mast cells in inducing inflammation and dermal fibrosis in cicatricial alopecia.

Lichen planopilaris (LPP) is a primary cicatricial alopecia characterized by the infiltration of lymphocytes in the upper portion of hair follicles. Inflammation around the bulge region of hair follicles induces destruction of hair follicle stem cells and tissue fibrosis, resulting in permanent hair loss. Treatment is still challenging, and the precise pathophysiology of this disorder is unknown. To clarify the pathogenesis of LPP, we performed histological and immunohistochemical analysis on specimens obtained from LPP patients. Formalin-fixed and paraffin-embedded samples were evaluated by staining with haematoxylin and eosin (HE), toluidine blue stain, immunohistochemistry and immunofluorescence. The immunohistochemical analysis demonstrated that CD4-positive T cells preferentially infiltrated into the follicular infundibulum in the LPP lesions. Toluidine blue stain detected a large number of mast cells in the inflammatory lesions of LPP. Interestingly, immunohistochemical analysis demonstrated that the mast cells harboured IL-17A- and IL-23-producing activity and expressed the IL-23 receptor. The number of IL-17A-positive mast cells was significantly higher in the LPP lesions than in normal scalp. Moreover, the IL-17 receptor was expressed exclusively in the follicular epithelial cells in the LPP lesions. These results suggested that mast cells infiltrating hair follicles might play a role in the pathogenesis of LPP via the IL-23/IL-17 axis.

PPAR-γ signalling as a key mediator of human hair follicle physiology and pathology.

Peroxisome proliferator-activated receptors (PPARs) are abundantly expressed in human skin, with PPAR-γ being the most intensively investigated isoform. In various ex vivo and in vivo models, PPAR-γ-mediated signalling has recently surfaced as an essential element of hair follicle (HF) development, growth and stem cell biology. Moreover, the availability of novel, topically applicable PPAR-γ modulators with a favourable toxicological profile has extended the range of potential applications in clinical dermatology. In this review, we synthesize where this field currently stands and sketch promising future research avenues, focussing on the role of PPAR-γ-mediated signalling in the biology and pathology of human scalp HFs, with special emphasis on scarring alopecias such as lichen planopilaris and frontal fibrosing alopecia as model human epithelial stem cell diseases. In particular, we discuss whether and how pharmacological modulation of PPAR-γ signalling may be employed for the management of hair growth disorders, for example, in scarring alopecia (by reducing HF inflammation as well as by promoting the survival and suppressing pathological epithelial-mesenchymal transition of keratin 15 + epithelial stem cells in the bulge) and in hirsutism/hypertrichosis (by promoting catagen development). Moreover, we explore the potential role of PPAR-γ in androgenetic alopecia, HF energy metabolism and HF ageing, and consider clinical perspectives that emanate from the limited data available on this so far. As this field of translational human hair research is still in its infancy, many open questions exist, for which we briefly delineate selected experimental approaches that promise to generate instructive answers in the near future.

Lichen planus: altered AIM2 and NLRP1 expression in skin lesions and defective activation in peripheral blood mononuclear cells.

BACKGROUND: Lichen planus (LP) is an inflammatory skin disease with unknown aetiology. Activation by pathogen-associated molecular patterns or environmental stimuli may activate some components of inflammasomes that contribute to the inflammatory process in LP lesions. AIM: To characterize the inflammasomes in skin lesions and peripheral blood mononuclear cells (PBMCs) of patients with LP under Toll-like receptor (TLR) activation. METHODS: In total, 15 patients with LP and 14 healthy controls (HCs) were enrolled in the study. Inflammasome expression in skin was evaluated by real-time PCR and immunohistochemistry, while ELISA was used to assess the production of interleukin (IL)-1ß by PBMCs under stimulation with TLR4 and TLR7/TLR8 agonists and adenosine triphosphate (ATP). RESULTS: Compared with the levels in HC samples, increased expression of the inflammasome AIM2 was verified in both epidermal and dermal sections of LP skin lesions, whereas NLRP1 and IL-ß expression levels were enhanced in the dermis. LP skin lesion samples exhibited higher AIM2 transcript levels, similar NLRP1 levels and lower pro-IL-1ß mRNA levels compared with HC samples. We verified that, compared with PBMCs from HC subjects, PBMCs from patients with LP produced similar amounts of IL-1ß after induction by TLR4 agonists but lower IL-1ß levels after induction by TLR7/TLR8 agonists, regardless of the addition of ATP. CONCLUSION: Alterations in innate immunity, such as inflammasome component expression in skin lesions and PBMCs, were observed in patients with LP. Further investigations of dysfunctional inflammasome activation and the chronic inflammatory status of LP are required.

Dynamic thiol/disulfide homeostasis in patients with lichen planus.

OBJECTIVE: Lichen planus (LP) is an autoimmune inflammatory disease of the mucocutaneous tissue, whose exact pathological course remains unclear. Abnormal thiol/disulfide homeostasis has been postulated to be responsible for a number of diseases predominated by chronic inflammation. To be able to contribute complicated and unclear pathogenesis of LP, we aimed to investigate dynamic thiol/disulfide homeostasis in patients with LP, using an original automated method developed by Erel and Neselioglu in this study. METHODS: The study group consisted of 81 unrelated patients with LP and 80 unrelated healthy controls with no LP lesions in their personal history or on clinical examination. Thiol/disulphide homeostasis tests have been measured with a novel automatic spectrophotometric method developed and the results have been compared statistically. RESULTS: Native thiol and total thiol levels were found as significantly higher in patients with LP than the control group (P = 0.026 and 0.035, respectively). There was no significant difference between the disulfide levels of the patients with LP and the control group. CONCLUSIONS: We provide evidence that that thiol/disulphide homeostasis impaired in favor of thiol levels in LP patients compared to the control group based on the data of our study. To the best of our knowledge, the present study is the first examination on the correlation between thiol and disulfide homeostasis in patients with LP.

C-Jun expression in lichen planus, psoriasis, and cutaneous squamous cell carcinoma, an immunohistochemical study.

The AP-1 transcription factor complex is a key player in regulating inflammatory processes, cell proliferation, differentiation, and cell transformation. The aim of the present study is to investigate C-Jun (one of AP-1complex) expression and its proliferative role in skin samples of lichen planus, psoriasis as common inflammatory skin diseases and squamous cell carcinoma using immunohistochemical method. The present study was carried out on skin biopsies of 15 psoriatic patients, 15 lichen planus patients, 15 SCC, and 15 normal skin biopsies. Nuclear expression of C-Jun was detected in basal and few suprabasal layers of epidermis of normal skin. C-Jun was expressed in the whole epidermal layers of both psoriasis (14/15) and lichen planus (15/15) in addition to its expression in lymphocytic infiltrate in the latter in about half of cases (8/15). C-Jun was also expressed in 93.3% (14/15) of SCC in a percentage lower than that of psoriasis, lichen planus, and normal skin. The percentage of C-Jun expression in SCC was significantly associated with an early stage (p = 0.000), free surgical margins (p = 0.022), and small tumour size (p = 0.003). CONCLUSIONS: The marked reduction of C-Jun in SCC in comparison to normal skin and inflammatory skin dermatoses may refer to its tumour suppressor activity. C-Jun expression in SCC carries favourable prognosis. Absence of significant association between C-Jun and Ki-67 either in SCC or inflammatory skin diseases indicates that it does not affect proliferative capacity of cells.

Increased expression of p16 in both oral and genital lichen planus.

BACKGROUND: Lichen Planus, LP, is an inflammatory disease of possible autoimmune origin affecting mainly oral and genital mucosa and skin. According to the WHO oral LP is considered a potentially malignant disorders. The p16 tumour suppressor protein can act as an inhibitor of cyclin dependent kinases 4 and 6 and thus down regulate cell cycle progression. Since the discovery of p16 several studies have evaluated its expression in various forms of human cancers. The aim of this study was to evaluate and compare the expression of p16 in oral and genital LP and corresponding healthy mucosa. MATERIAL AND METHODS: A total of 76 cases of oral LP (OLP), 34 cases of genital LP (GLP), 12 cases of healthy oral and 9 cases of healthy genital mucosa were analysed by the use of immunohistochemistry. RESULTS: Data showed p16 to be highly expressed in both oral and genital LP, higher than in oral (p=0.000), and genital controls (p=0.002). CONCLUSIONS: Results suggest that the over-expression of p16 seen in LP play a part in the histopathology of the disease.

Tnfa signaling through tnfr2 protects skin against oxidative stress-induced inflammation.

TNFα overexpression has been associated with several chronic inflammatory diseases, including psoriasis, lichen planus, rheumatoid arthritis, and inflammatory bowel disease. Paradoxically, numerous studies have reported new-onset psoriasis and lichen planus following TNFα antagonist therapy. Here, we show that genetic inhibition of Tnfa and Tnfr2 in zebrafish results in the mobilization of neutrophils to the skin. Using combinations of fluorescent reporter transgenes, fluorescence microscopy, and flow cytometry, we identified the local production of dual oxidase 1 (Duox1)-derived H2O2 by Tnfa- and Tnfr2-deficient keratinocytes as a trigger for the activation of the master inflammation transcription factor NF-κB, which then promotes the induction of genes encoding pro-inflammatory molecules. In addition, pharmacological inhibition of Duox1 completely abrogated skin inflammation, placing Duox1-derived H2O2 upstream of this positive feedback inflammatory loop. Strikingly, DUOX1 was drastically induced in the skin lesions of psoriasis and lichen planus patients. These results reveal a crucial role for TNFα/TNFR2 axis in the protection of the skin against DUOX1-mediated oxidative stress and could establish new therapeutic targets for skin inflammatory disorders.

MicroRNAs in cutaneous lichen planus.

Lichen planus (LP) is a chronic, inflammatory, papulosquamous, autoimmune disease. The pathogenesis of LP appears to be complex, with interactions between genetic, environmental and lifestyle factors. MicroRNAs (miRNAs) are short RNAs encoded in both protein coding and noncoding areas of the genome, and have been found to be involved in the pathogenesis of some inflammatory skin diseases. The aim of this study was to map the levels of miRNA (miR-)-203 and miR-125b in cutaneous LP to evaluate their possible role in the pathogenesis of the disease. In total, 40 patients with classic cutaneous LP and 40 age- and sex- matched healthy controls (HCs) were enrolled in this study. Punch biopsies (4 mm) were taken from cutaneous LP lesions of patients and from normal skin of HCs. miRNA-203 and miRNA-125b mRNA expression was estimated by reverse transcription PCR. Our analysis revealed a significantly (P < 0.001 for both) lower expression of both miR-203 and miR-125b mRNA in the LP than in the HC biopsies. No relationship was found between expression of miR-203 or miR-125b and either age, sex, presence of mucosal lesions or positivity for HCV antibodies. miR-125b and miR-203 could be involved in the pathogenesis of cutaneous LP.

Distinct interferon-gamma and interleukin-9 expression in cutaneous and oral lichen planus.

BACKGROUND: Cutaneous (CLP) and oral lichen planus (OLP) as the main subtypes of lichen planus (LP) present with different clinical manifestation and disease course, although their histopathologic features such as the band-like lymphocyte infiltrate and keratinocyte apoptosis are similar. So far, the underlying cellular and molecular mechanisms remain poorly understood. OBJECTIVE: The aim of this study was to characterize and compare the in situ cellular infiltrates, cytokine expression profiles and apoptosis markers in CLP and OLP. METHODS: Using immunofluorescence staining and laser scanning microscopy, we evaluated the cellular infiltrate (CD1a, CD3, CD4, CD8, CD21, CD57, CD123), cytokine expression (interleukin (IL)-1, IL-6, IL-9, IL-10, IL-17, IL-22, IL-23, tumour necrosis factor-α, transforming growth factor-ß, interferon (IFN)-γ), and apoptosis markers (Fas, Fas ligand, cleaved caspase-3, TUNEL) of 21 anonymized biopsy specimens of LP (11 CLP, 10 OLP). RESULTS: Among infiltrating cells mainly T cells and natural killer (NK) cells as well as plasmacytoid dendritic cells (DC) were observed. A predominance of CD8+ T cells was noted in OLP. In both CLP and OLP, T helper (Th)1, Th9, Th17, and Th22-type cytokines were expressed. The expression of IL-9, IFN-γ and IL-22 was higher in CLP compared to that of OLP (P = 0.0165; P = 0.0016; P = 0.052 respectively). Expression of Fas and Fas ligand as well as cleaved caspase-3-positive cells was observed in the epithelium of all LP samples. CONCLUSIONS: The cell and cytokine patterns of CLP and OLP were partially distinct and generally resembled those reported for autoimmune diseases. The presence of CD8+ and NK cells as well as Fas/Fas ligand expression suggested that various pathways involved in keratinocyte apoptosis are relevant for LP. These results might help to establish targeted therapies for LP.

CLA and CD62E expression in oral lichen planus lesions.

OBJECTIVE: There are few reports on the migration of CLA+ T cells through E-selectin in cutaneous lichen planus, with only one study on oral lichen planus (OLP). This study aimed to analyze CLA expression and assess whether there is a correlation with E-selectin (CD62E) in OLP lesions. MATERIAL AND METHODS: Biopsies were performed on 11 patients including two areas: one without clinical and histopathological features of OLP [perilesional group (PLG)] and the other with clinical and histopathological features of OLP [OLP group (OLPG)]. The specimens obtained were divided into two: One was fixed in formalin for routine analysis (H&E), and the other was frozen for CD3, CD4, CD8, CLA, and CD62E immunofluorescence markers. RESULTS: More CD4+ (median 1409, range 860-2519), CD8+ (median 1568, range 654-3258), and CLA+ T cells (median 958, range 453-2198) and higher CD62E expression (median 37, range 27-85) were identified in OLPG (P = 0.003; P = 0.003; P = 0.004; P = 0.003, respectively) than those in PLG. The median prevalence analysis was also significantly higher for CLA+CD8+ T cells in OLPG (OLPG = 39.4%, range 18.4-64.2; PLG = 29.4%, range 12.1-47.1) (P = 0.026). None of the correlations between CD3+ or CLA+ T cells and CD62E in OLPG and in PLG were significant. CONCLUSION: The significant presence of CLA+ T cells and E-selectin expressions in the OLPG suggests their involvement in the etiopathogenesis of OLP; however, only a weak correlation between CLA+ T cells and E-selectin was observed.

Up-regulation of Proinflammatory Genes and Cytokines Induced by S100A8 in CD8+ T Cells in Lichen Planus.

Lichen planus (LP) is a chronic inflammatory mucocutaneous disease. The inflammatory status of LP may be related to S100A8 (myeloid-related protein 8; MRP8) activation of cytotoxic cells. The aims of this study were to evaluate S100A8 expression in skin lesions and the in vitro effects of S100A8 on CD8+ T cells and natural killer (NK) cells in LP. Increased levels of S100A8/S100A9 were detected in the skin lesions as well as in the sera of subjects with LP. S100A8 expression induced an increased cytotoxic response by peripheral blood CD8+CD107a+ T cells as well as by NK CD56bright cells in patients with LP. Increased expression of interleukin (IL)-1ß, tumour necrosis factor (TNF) and IL-6 in the CD8+ T cells of patients with LP was induced by S100A8, in contrast to the control group that produced IL- 10 and interferon (IFN) type I genes. These data suggest that, in individuals with LP, S100A8 may exert distinct immunomodulatory and cytotoxicity functions.

The Use of Anti-Keratin 903 Antibodies to Visualize Colloid Bodies and Diagnose Lichen Planopilaris.

Cytokeratins are a major component of colloid bodies that are essentially diagnostic of lichen planopilaris (LPP). Here, the authors assess the ability of the cytokeratin 903 antibody (CK-903) to stain colloid bodies and differentiate LPP from other histologically similar appearing primary cicatricial alopecias. A retrospective review of all specimens submitted to the dermatopathology department over a 2-year window identified 18 cases of LPP and 20 cases of histologically similar appearing entities (discoid lupus erythematosus or central centrifugal cicatricial alopecia) through a combination of H&E, elastic van gieson, and periodic acid-schiff stains. All 38 samples were then prospectively stained with CK-903. Colloid bodies were identifiable in 3 of the 18 LPP cases based on H&E alone but were seen in 9 of 18 cases when CK-903 was used. There were no cases where colloid bodies were seen on H&E but not subsequently identified with CK-903. Additionally, there was no CK-903 staining in any of the 20 cases of similar appearing entities except 1 case of discoid lupus erythematosus, which is known to occasionally show colloid bodies. The authors conclude that CK-903 is a useful adjunctive tool that will allow for a quicker, less costly, and more accurate diagnosis of LPP given its ability identify colloid bodies even in the setting of significant inflammation and fibrosis and its advantages over direct immunofluorescence of low cost, short preparation time, and lack of need for a specialized fluorescent microscope.