Basal Cells Research Articles

DEHP (di(2-ethylhexyl)phthalate) stimulates skin pigmentation by perturbing cytoskeletal homeostasis.

Phthalates are extensively employed plasticizers crucial for conferring flexibility and plasticity to polyvinyl chloride. Phthalates, including DEHP (di(2-ethylhexyl)phthalate), present in diverse products, have been identified in fine dust and are capable of infiltrating the body, potentially posing health hazards. Importantly, melanocytes, existing at the basal layer of the epidermis, are susceptible to toxic substances. In our study, we employed the 3D human pigmented epidermis model, MelanoDerm™, along with the B16F10 murine melanoma cell line, to examine the influence of DEHP exposure on melanocytes. The exposure to low concentrations of DEHP (~ 5μM), resulted in the extension of melanocyte dendrites, indicating the stimulation of melanocytes. Analysis of gene expression and protein profiles unveiled the up-regulation of MITF, Arpc2, and TRP1 genes subsequent to DEHP exposure, indicating alterations in cytoskeletal and melanosome-related genetic and protein components in melanocytes. Notably, increased pigmentation was observed in MelanoDerm™ following DEHP exposure. DEHP-stimulated reactive oxygen species generation appeared to be involved in these events since the antioxidant, ascorbic acid attenuated ROS generation and MITF upregulation. Collectively, our study demonstrated that DEHP exposure can induce cytoskeletal disturbance and skin pigmentation through oxidative stress.

Unveiling the Potential of Ultrasonic-Assisted Ethanol Extract from Sargassum horneri in Inhibiting Tyrosinase Activity and Melanin Production in B16F10 Murine Melanocytes.

Melanogenesis, regulated by genetic, hormonal, and environmental factors, occurs in melanocytes in the basal layer of the epidermis. Dysregulation of this process can lead to various skin disorders, such as hyperpigmentation and hypopigmentation. Therefore, the present study investigated the effect of ultrasonic-assisted ethanol extract (SHUE) from Sargassum horneri (S. horneri), brown seaweed against melanogenesis in α-melanocyte-stimulating hormone (MSH)-stimulated B16F10 murine melanocytes. Firstly, yield and proximate compositional analysis of the samples were conducted. The effect of SHUE on cell viability has been evaluated by using 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. After that, the melanin content and cellular tyrosinase activity in α-MSH-stimulated B16F10 murine melanocytes were examined. Western blot analysis was carried out to investigate the protein expression levels of microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 (TRP1), and tyrosinase-related protein-2 (TRP2). In addition, the effect of extracellular signal-regulated kinase (ERK) on the melanogenesis process was assessed via Western blotting. As per the analysis, SHUE contained the highest average yield on a dry basis at 28.70 ± 3.21%. The findings showed that SHUE reduced the melanin content and cellular tyrosinase activity in α-MSH-stimulated B16F10 murine melanocytes. Additionally, the expression levels of MITF, TRP1, and TRP2 protein were significantly downregulated by SHUE treatment in α-MSH-stimulated B16F10 murine melanocytes. Moreover, SHUE upregulated the phosphorylation of ERK and AKT in α-MSH-stimulated B16F10 murine melanocytes. In addition, experiments conducted using the ERK inhibitor (PD98059) revealed that the activity of SHUE depends on the ERK signaling cascade. These results suggest that SHUE has an anti-melanogenic effect and can be used as a material in the formulation of cosmetics related to whitening and lightening.

Abstract PR001: TRIM29 is required for basal bladder cancer invasive progression

Abstract TRIM29 (Tripartite Motif 29) also known ATDC, is an E3 ubiquitin ligase frequently upregulated in muscle-invasive bladder cancer (MIBC). We have previously shown TRIM29 global overexpression in a genetically engineered mouse model (GEMM) is sufficient to ` bladder cancer development and progression to MIBC. Other studies strongly suggest cytokeratin-5/14 (Krt5+/Krt14+) expressing basal-stem progenitor cells in the urothelium are the cells of origin for MIBC in mice. We therefore hypothesized that Trim29 expression in Krt5+ basal urothelial cells is required for development of MIBC in mice. To test this, we generated a GEMM harboring a Trim29 conditional KO allele and tamoxifen responsive Cre under control of the bovine Krt5promoter. Exposure of Krt5-CreERT2 Trim29flox/flox mice to tamoxifen resulted in activation of Cre and loss of Trim29 expression only in the Krt5+ basal urothelium. To induce bladder tumorigenesis, we utilized the urothelial specific carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in drinking water at 0.05%. After 6 months, tumor invasion was staged by a genitourinary pathologist based on depth of invasion: T1 (stromal invasive), T2 (muscle invasive) and T3 (deep muscle/peri-vesicular invasion). In agreement with previous studies, BBN exposure resulted in loss of Krt5-negative intermediate and superficial cells, and expansion of Krt5+/Krt14+ basal cells across the urothelium. In combination with a tamoxifen treatment this led to total Trim29 KO in the urothelium. All male Trim29 WT mice exposed to BBN developed Trim29+ bladder tumors, >50% of which demonstrated extensive progression to muscle-invasion (57% n=23). In contrast, only 16% of mice with Trim29 loss in Krt5+ basal cells developed MIBC (n=18). As an E3 ubiquitin ligase TRIM29 is known to target immune adaptor molecules, notably the stimulator of interferon genes (STING), for proteasomal degradation. We hypothesized TRIM29 targets STING during invasive progression and supports the establishment of an immune-privileged niche at the bladder cancer invasive front. We find TRIM29 expression in human bladder tissues is upregulated in the urothelium under stress and in MIBC tumors. In mice, BBN exposure upregulated Trim29 expression in the bladder urothelium which correlated with low urothelial Sting. In contrast, Krt5+ Trim29 loss resulted in significantly elevated Sting in the bladder urothelium. Multiplex immunofluorescence imaging and immunotyping of Trim29 KO mouse tissues revealed peritumoral enrichment of CD4+ and CD8+ T cells, CD206+ immunosuppressive macrophages, and CD4+FoxP3+ regulatory T cells. Taken together, these results suggest that TRIM29-mediated downregulation of STING in the bladder urothelium results in decreased immune surveillance at the tumor-stromal interface which expedites invasion and tumor burden. Citation Format: Alan Kelleher, Luke Broses, Yin Wang, Marian Henderson, Mark Day, Aaron Udager, Phillip Palmbos. TRIM29 is required for basal bladder cancer invasive progression [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr PR001.

Immediate but Temporal Response: The Role of Distal Epithelial Cells in Wound Healing.

Efficient oral mucosal wound healing requires coordinated responses from epithelial progenitor cells, yet their spatiotemporal recruitment and activation remain unclear. Using a mouse model of palatal mucosal wound healing, we investigated the dynamics of epithelial cells during this process. Proliferation analysis revealed that, in addition to the expected proliferation center near the wound edge, distal cell populations rapidly activated post-injury by elevating their mitotic activity. These distal cells displayed predominant lateral expansion in the basal layer, suggesting roles beyond just tissue renewal. However, while proximal proliferation center cells sustained heightened proliferation until re-epithelialization was completed, distal cells restored basal turnover rates before wound closure, indicating temporally confined contributions. Lineage tracing of Wnt-responsive epithelial cells showed remarkable clone expansion in basal layers both proximally and distally after wounding, contrasting with gradual clone expansion in homeostasis. Although prioritizing tissue repair, epithelial progenitor cells maintained differentiation programs and barrier functions, with the exception of the leading edge. At the leading edge, we found accelerated cell turnover, but the differentiation program was suspended. In summary, our findings uncovered that oral wound re-epithelialization involves two phases: an initial widespread response with proliferation of proximal and distal cells, followed by proliferation confined to the wound proximal region. Uncovering these stage-specific healing mechanisms provides insights for developing targeted therapeutic strategies to improve wound care.

P31 Modelling epidermal melanocytes behaviour during plaque psoriasis resolution

Abstract Introduction and aims Melanocytes in the human epidermis exist in the stratum basale at a ratio of 1 melanocyte to approximately 10 keratinocytes. They do not divide, even upon ultraviolet radiation stimulation, and do not appear to apoptose. In psoriasis, this melanocyte/keratinocyte ratio is retained, despite the enormous keratinocyte hyperplasia, inferring a commensurate expansion in melanocyte number. Therefore, here we investigate whether melanocyte number is altered following the reduction of keratinocytes upon treatment of psoriasis plaques with biologic therapy. Methods Matching lesional and nonlesional epidermis sets of patients (n = 4) at day 0 and after 4 and 12 weeks of treatment were compared with healthy controls. To assess the presence of apoptotic melanocytes, the terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay was performed. Immunohistochemistry with microphthalmia-associated transcription factor (melanocyte marker) and Ki-67 (proliferation marker) was used to assess melanocyte proliferation. Finally, melanocyte number per mm of basal layer and melanocyte/keratinocyte ratio were estimated by image analysis using ImageJ. Results Proliferating melanocytes were detected in nonlesional and lesional samples and in resolving plaques after 4 and 12 weeks of treatment but not in healthy epidermis. Melanocyte number per mm of basal layer was significantly higher in nonlesional than lesional sections compared with healthy controls (P < 0.01) suggesting that melanocyte expansion already occurs prior to lesion establishment, revealing early melanocyte deregulation. After 4 and 12 weeks of treatment the number of melanocytes in lesional and nonlesional sections was still significantly higher than controls (P < 0.05) and had not returned to normal despite the dramatic reduction in keratinocytes. The TUNEL assay did not detect evidence of melanocyte apoptosis. Conclusions This study shows that rare melanocyte proliferation occurs in nonlesional psoriasis skin and in resolving lesional skin. Given our inability to detect apoptotic melanocytes, it remains unclear how melanocyte numbers return to normal after plaque resolution These unique findings support a role for melanocytes in psoriasis pathogenesis and encourage further investigation.

Abstract A016: NRF2 activation promotes a fitness disadvantage in normal urothelium and drives a basal-like phenotype

Abstract Introduction: Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that plays a key role in protecting cells from oxidative stress. NRF2 is negatively controlled by Kelch-like ECH-associated protein 1 (KEAP1), which facilitates NRF2 ubiquitination and proteosomal degradation under homeostatic conditions. NRF2 activating mutations occur at a frequency of 5.9% in muscle-invasive bladder cancer (MIBC). However, the role of NRF2 in MIBC has not been fully understood. The aim of this study is to clarify how NRF2 affect to the normal epithelial cells and the tumor cells in bladder. Methods: We used genetically engineered mice (GEM) with a Cre inducible Nrf2 activating mutation (LSL-Nrf2-E79Q). To evaluate how Nrf2 affects the tumorigenesis process in vivo, the N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) was administered to Upk3a-CreERT2; LSL-Nrf2-E79Q/+ (UN) mice. We also established normal urothelial organoids and BBN tumor derived organoids from wild-type (WT) and Krt5-CreERT2; LSL-Nrf2-E79Q/+ (K5N) mice for ex vivo study. To induce overexpression of NRF2, we utilized KI696 (KEAP1-NRF2 inhibitor) as a pharmacological agent and performed NAD/NADH assay to quantify the reductive stress. Additionally, we performed single cell RNA sequencing (scRNA-seq) with WT, UN and K5N mice bladder to identify the effect of Nrf2E79Q on the normal epithelial cells. Results: In BBN induced tumor model in vivo, UN mice did not differ in time to tumor development from the control WT mice. Furthermore, UN tumors had lost the post-recombination allele of LSL-Nrf2-E79Q in genomic PCR, meaning cells expressing Nrf2E79Q are selected against during the process. In ex vivo study, KI696 induced reductive stress in both WT normal urothelial organoids and BBN tumor derived organoids, but inhibited cell proliferation only in normal urothelial organoids. In K5N organoids, Nrf2E79Q activation enhanced relative mRNA expression of a number of basal related genes. In addition to that, vehicle organoids in differentiation media showed phenotypic differentiation, whereas those treated with tamoxifen did not demonstrate phenotypic signs of differentiation suggesting Nrf2 activation promotes a basal-like phenotype. Furthermore, we annotated three clusters in mice bladder epithelial cells as luminal, intermediate and basal using scRNA-seq and looked at their proportion among WT, UN and K5N mice. We found that the percentage of luminal cells was decreased and intermediate and basal cells increased in both UN and K5N mice compared to WT mice. This indicated that Nrf2E79Q promotes disadvantage in luminal cells in UN mice, whereas it contributes to the increase in intermediate and basal cells in K5N mice. Conclusion: These results suggested that Nrf2E79Q promotes a fitness disadvantage in normal mice urothelium. Furthermore, Nrf2E79Q inhibits differentiation of K5N organoids and drives a basal-like phenotype in GEM models. Further investigation is needed to clarify the mechanism of NRF2 activating mutation contributing the tumorigenesis in bladder. Citation Format: Akihiro Hamada, Yuki Kita, Di Wu, Mi Zhou, Sean Clark-Garvey, Andrew Gdowski, Michael Sturdivant, Wolfgang Beckabir, Elliott Drew Toomer, Emily Kounlavong, Lucia Lim, Kathryn Gessner, Jeffrey Damrauer, William Kim. NRF2 activation promotes a fitness disadvantage in normal urothelium and drives a basal-like phenotype [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr A016.

Abstract B019: Identification of gene signatures predictive of response to Ad-IFNα/Syn3 in bladder cancer

Abstract Introduction: Interferon α gene therapy (Ad-IFNα/Syn3) is FDA approved for treatment of BCG-unresponsive non-muscle invasive bladder cancer. Ad-IFNα/Syn3 is a non-replicating adenovirus that when transduced into target tissues, produces IFNa2b protein with anti-tumor activity. In the phase 3 multicenter trial, 45.5% of patients with carcinoma-in-situ and 60% of those with Ta/T1 disease who had a complete response to Ad-IFNα/Syn3 at 3 months remained recurrence free at 12 months. Targeting mechanisms of resistance and identifying predictive biomarkers to improve patient selection and overall response rates is a top priority. Towards this, we treated 29 human bladder cancer cell lines with Ad-IFNα/Syn3 and assessed their responses to therapy. We identified sensitive and resistant cell lines and gene signatures predictive of response. Methods: Human bladder cancer cell lines were grown in MEM supplemented with 10% FBS in 96-well plate. After overnight attachment, these were treated with Ad-IFNα/Syn3 (MOI 1000) and cell titre glow assay was performed 72h post-treatment. Cells were also seeded in 6-well plates. and after 24h cell-free supernatants were collected for ELISA and cells were collected for RNA isolation using RNAqueous Total RNA Isolation kit (Thermo Fisher). RNA quality was assessed using Tapestation. RNAseq analysis was carried out using Ion proton Sequencer. Ingenuity pathway analysis (IPA) and gene set enrichment were performed on the sequencing data for the cell lines. ELISA was used to measure IFNα and IL6 protein levels in cell free supernatants. We also tested organoids developed from bladder cancer patients to test drug efficacy and identify gene signatures. Results: Out of the 29 cell lines, we identified that sensitivity to Ad-IFNα/Syn3 was pronounced in luminal cells (8/13 luminal cell lines). Most basal cells were either resistant (>70% viability) or only moderately sensitive to Ad-IFNα/Syn3 (between 70-40% viability) when compared to control. We selected 7 cell lines for sequencing and ELISA measurements: luminal cell lines BV, UC6, Rt4V6 and UC5, and basal cell lines ScaBER, HT1197, and T24. All cell lines mentioned above could be successfully transduced by the adenoviral vector as measured by increased expression of IFNα protein in the cell-free supernatants. Ad-IFNα/Syn3-sensitive luminal cell lines at baseline had lower IFNα and IFNγ scores when compared to resistant basal cell lines. We identified several cell-death pathways enriched in treated cells that were sensitive to Ad-IFNα/Syn3. IL6 measurements in cell free supernatants revealed increased expression of IL6 after treatment in sensitive cells. However, in resistant cells IL6 expression was either high at baseline (ScaBER) or both undetectable at baseline and after treatment (UC5). Conclusion: Our results suggest that the luminal cell lines are more sensitive to Ad-IFNα/Syn3 and that high baseline expression of IFNα and IFNγ in basal cell lines contributes to resistance. IL6 levels are also predictive of response to Ad-IFNα/Syn3. Citation Format: Morgan E. Pierce, Alexis R. Steinmetz, Aruna Nannapaneni, Tanner S. Miest, David J. McConkey, Sharada Mokkapati, Colin P.N. Dinney. Identification of gene signatures predictive of response to Ad-IFNα/Syn3 in bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr B019.

Recent advances in the study of the structure and function of the epididymis

Testicular sperm maturation is critical for establishing male fertility. Spermatozoa undergo remodeling of sperm proteins and changes in lipid and ribonucleic acid composition during transport in the epididymal ducts, which play an important role in sperm maturation. The anatomy, epithelial cell types, physiological functions, and epigenetic inheritance of the epididymis are explored, and recent findings in epididymal research are analyzed. Suggesting possible directions for future research on the epididymis. Using the keywords “epididymis”, “sperm”, and “sperm maturation”, a search of the epididymis was performed through databases and official websites of journals related to reproduction. The epididymis was searched in databases and on the official websites of journals related to reproduction. This review introduces the characteristics of the epididymis, as well as the biological functions of cell types such as principal cells, clear cells, and basal cells, providing a detailed description of the overall physiological functions of the epididymis. It highlights current research hotspots in the field of epididymis, including single-cell analysis, epigenetics, and extracellular vesicles, aiming to offer a comprehensive understanding for beginners. The review emphasizes the importance of the epididymis, its impact on sperm maturation and subsequent embryo development, and how it advances research on epididymal diseases while providing new directions for the study and treatment strategies of infertility.

O01 Mapping the cellular and molecular dynamics of mouse and human hair follicles reveals mechanisms of hair growth

Abstract Introduction and aims Tissue homeostasis in continuously renewing organs, such as the skin, rely on orchestrated cellular and molecular dynamics. The hair follicle (HF) is characterized by distinct keratinocytes organized in transcriptionally and functionally distinct concentric HF layers. The anagen progenitor cells (also called germinative layer cells) are located juxtaposed to the dermal papilla and give rise to each of the differentiated layers. Despite this well-known high level of organization and cell-lineage separation, it is still unclear how the germinative layer cells coordinate hair growth and commit to specific lineages. Methods Here, we employed single-cell RNA sequencing, single-molecule mRNA fluorescence in situ hybridization and in vivo lineage tracing to show how the matrix progenitor cells commit and contribute to the HF lineages depending on their position. Furthermore, we developed a four-dimensional live imaging system of the human HF to construct a global map of single-cell dynamics. Results We show that the HF progenitors dynamically relocate in a conveyor-belt-like movement, switch their lineage fate and gradually restrict their potential. This spatiotemporal cell choreography is characterized by a gradual change of expression from Lgr5 in the lower proximal cup, through Dcn, Id3 and Msx1 in the central part, to distal Lef1 expression where the medulla lineage starts. Detailed in situ mRNA staining and mouse clonal lineage tracing show the transcriptional changes and gradual lineage restriction of matrix progenitors in the spatial context. Combining human HF imaging with fluid dynamics theories, we uncovered a spiral-like downward movement of outer root sheath cells, feeding the germinative layer stem cells, and revealed a pulling force induced by the outer root sheath cells as a critical driver for hair growth. Conclusions Taken together, our study uncovered how HF progenitor cells progress in a conveyor-belt-like manner through several transcriptional states and discovered new cellular and molecular mechanisms regulating hair formation.

Abstract IA001: Cellular and molecular underpinnings of field cancerization and progression to invasive carcinoma in bladder cancer

Abstract Two major concerns in clinical management of bladder cancer are: (i) the high frequency of recurrence; and (ii) the morbidity and mortality associated with progression to invasive disease (invasive urothelial carcinoma, IUC). To gain a better understanding of these issues we have used the murine BBN (N-butyl-N-(4-hydroxylbutyl) nitrosamine) experimental model of bladder cancer, as well as tissue samples from normal human bladders and from bladders of patients at various stages of bladder cancer formation and progression. We have documented in the BBN model a CIS-like stage, prior to invasion, in which clonal expansion from a single cell occupies a significant fraction of the urothelium. With this experimental murine model alongside observations from patient samples and data from The Cancer Genome Atlas (TCGA), we have ascertained that a key event in progression of pre-invasive to invasive carcinoma is the silencing of the Sonic hedgehog (Shh) member of the Hedgehog gene family. Silencing-associated invasion appears due to the loss of SHH-induced differentiation signals, which when present slow growth and block invasion. Despite the consistent loss of SHH expression in invasive murine and human bladder cancers, however, TCGA data show few if any mutations in the SHH gene of IUC cells. Instead, our studies of patient samples and cancer-derived cell lines reveal that the loss of SHH expression is due to tighter chromosomal packaging and reduced accessibility of a bladder-specific enhancer located ~200 kb upstream of the SHH transcription start site. We have found that inhibitors of certain chromatin-modifying enzymes, including an FDA-approved drug, are capable of re-activating SHH expression, and are testing the possibility that these drugs may block or reverse invasion of urothelial carcinoma. The high frequency of bladder cancer recurrence is thought to result from field cancerization, that is, an increased probability of new cancer formation in apparent normal urothelium, even after successful resection of the primary tumor. To understand the basis for this field effect, we compared apparent normal urothelium from cancer patients to truly normal urothelium from bladders never affected by malignancy. We found that apparent normal samples display a dramatically increased basal character in transcriptomic assays, using as a metric of basalization an index constructed from single cell RNA-seq analysis of normal urothelium. We and others have demonstrated previously by lineage tracing and cell ablation studies in the BBN model that IUC arises from basal stem cells of the urothelium. The basalization of urothelium distant from the primary tumor that we observe thus may account for the increased probability of cancer formation in the apparent normal urothelium of bladder cancer patients. We have found that several FDA-approved antagonists of EGF signaling can reverse this basalization in the mouse BBN model as well as in organoid culture, and that these drugs dramatically reduce the formation of tumors following BBN exposure. Citation Format: Philip A. Beachy, Kris B. Prado, Aaron M. Kershner, Karim Mrouj, Bernard M. Kiss, Hua Dong, Ozgu Aydogdu, Ye Tian, Joseph C. Liao. Cellular and molecular underpinnings of field cancerization and progression to invasive carcinoma in bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr IA001.

O19 Improvement of a junctional epidermolysis bullosa mouse model

Abstract Introduction and aims Junctional epidermolysis bullosa (JEB) is the most severe of the epidermolysis bullosa (EB) disorders and is caused by mutations in genes encoding the skin basement membrane proteins laminin 332, type XVII collagen or integrin α6β4. Affected individuals experience blistering from birth leading to scarring, granulation tissue and susceptibility to infection. In JEB, generalized severe, there is 50% mortality in the first 2 years of life, often owing to failure to thrive or overwhelming infection. A number of animal models for JEB exist; however, because of severe blistering on the entire surface of the skin, these mice die soon after birth, reducing their experimental utility. In 2017, the first adult inducible knockout mouse model of JEB was published. In this mouse model, the disruption of the Lama3 gene is specifically induced in epidermal basal keratinocytes after birth. These mice remain viable, which allows us to study the longer-term consequences of the loss of laminin α3. However, the mice did not develop the severe phenotype observed in patients with JEB. Methods We have optimized this previously published methodology of a conditional knockout JEB mouse model (Lama3flx/flxK14CreERT) to now include more regular tamoxifen injections, which Results in a more controlled and severe phenotype of JEB. Results Widespread skin blistering develops after 12 weeks of tamoxifen treatment with an impaired skin barrier (transepidermal water loss) and a loss of epidermal lipids. Immunofluorescent staining was conducted to assess skin differentiation (K14, transglutaminase 1, loricrin), proliferation (Ki67), basement membrane proteins (laminin α3, laminin β3, laminin γ2, collagen VII) and immune markers (F4/80, Ly6-G/C, CD3, CD79). Conclusions These mice recapitulate all key features of human JEB with loss of laminin α3 at the basement membrane, epidermal thickening and visible blisters. This allows us to delve deeper into the functional and downstream pathways affected by the loss of laminin α3 and discover why the prognosis of patients with JEB is so severe.

P16 Fibroblast signalling crosstalk drives junctional epidermolysis bullosa disease progression

Abstract Introduction and aims Junctional epidermolysis bullosa (JEB) is a devastating hereditary skin disorder characterized by severe fragility of skin and mucus membrane, emerges as blistering with little or no trauma. The major classification of JEB includes JEB intermediate and JEB severe; the latter is the most common subtype, which is the result of loss of function mutations in the skin basement membrane protein laminin-332. Lacking this protein impairs basement membrane adhesion of epidermal keratinocytes and leads to deregulated epidermal–dermal crosstalk. The skin dermis is composed of multiple fibroblast subpopulations with different functions in skin homeostasis and repair; however, their specific involvement in skin diseases is largely unknown. Here, we investigate how fibroblast subpopulations, namely papillary and reticular fibroblasts, impact JEB disease progression and skin regeneration. Methods Three-dimensional (3D) organotypic (OT) combining healthy (control) and diseased (JEB) keratinocytes cells with distinct fibroblast subpopulations from different anatomical sites were developed and analysed by immunohistochemistry and RNA-Seq. Results JEB OTs with papillary fibroblasts showed increased epidermal growth, invagination of basal layer and deregulated differentiation compared with reticular fibroblasts. RNA-Seq analysis revealed altered activity in key signalling including immune, cytokine, gap junction, mitogen-activated protein kinase and remodelling of keratinization and ECM proteins, particularly in JEB OT cultured with papillary fibroblast. JEB OTs and cells also demonstrated variation in cell proliferation and activation of transforming growth factor-β1 and immune cell signalling. Currently, we are targeting identified signalling pathways in our two-dimensional and 3D cell culture models and identifying druggable targets, before testing selected candidates in our JEB mouse disease model for further preclinical validation. Conclusions By dissecting the pathological signalling interactions between keratinocytes and distinct fibroblast subpopulations, our goal is to identify new therapeutic target to improve the skin health and regeneration in patients with JEB.

P05 The aryl hydrocarbon receptor pathway is dysfunctional in atopic dermatitis

Abstract Introduction and aims Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by epidermal barrier disruption and type-2 immune dysregulation. While treatment has improved with targeted biologics, clinical response varies, highlighting the need for additional therapeutic strategies. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor and environmental sensor, which maintains skin barrier integrity and homeostasis by reducing inflammation. Upon activation, AHR induces the expression of CYP1A1, a biomarker of pathway activation and critical for AHR ligand metabolism. Tapinarof, a topical AHR agonist, is approved for psoriasis and is effective in phase III clinical trials in AD, highlighting the importance of this pathway in inflammatory skin disease. Nevertheless, AHR expression is increased in AD skin, leading to the hypothesis that the pathway is dysregulated, thus not exerting its anti-inflammatory effect. Methods Here we begin to perform a global investigation of the AHR pathway in AD. We measured AHR and CYP1A1 mRNA expression by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) in healthy and AD skin, with spatial mRNA expression assessed by RNAscope. We also investigated AHR mRNA expression in interleukin (IL)-4 stimulated (100 ng mL−1) normal human epidermal keratinocytes (NHEKs) using qRT-PCR. Results We found that AHR mRNA is significantly upregulated in lesional AD (n = 6) compared with healthy skin (n = 9; P < 0.05), whereas CYP1A1 mRNA expression shows a downward trend in lesional AD compared with healthy skin (P = 0.063). The AHR expression pattern differs in lesional AD (n = 7) compared with healthy skin (n = 8), with AHR localizing in the epidermal basal layer. Finally, IL-4 significantly upregulated AHR mRNA (n = 4 wells; P < 0.001) expression in NHEKs compared with unstimulated cells. Conclusions Overall, our data have uncovered a dysfunctional AHR pathway in AD, with increased AHR expression, possibly driven by the AD inflammatory milieu, but reduced pathway activation. Further investigations are required to fully dissect this pathway and maximize its potential as a therapeutic target for AD.

Jag1/2 maintain esophageal homeostasis and suppress foregut tumorigenesis by restricting the basal progenitor cell pool

Basal progenitor cells are crucial for maintaining foregut (the esophagus and forestomach) homeostasis. When their function is dysregulated, it can promote inflammation and tumorigenesis. However, the mechanisms underlying these processes remain largely unclear. Here, we employ genetic mouse models to reveal that Jag1/2 regulate esophageal homeostasis and foregut tumorigenesis by modulating the function of basal progenitor cells. Deletion of Jag1/2 in mice disrupts esophageal and forestomach epithelial homeostasis. Mechanistically, Jag1/2 deficiency impairs activation of Notch signaling, leading to reduced squamous epithelial differentiation and expansion of basal progenitor cells. Moreover, Jag1/2 deficiency exacerbates the deoxycholic acid (DCA)-induced squamous epithelial injury and accelerates the initiation of squamous cell carcinoma (SCC) in the forestomach. Importantly, expression levels of JAG1/2 are lower in the early stages of human esophageal squamous cell carcinoma (ESCC) carcinogenesis. Collectively, our study demonstrates that Jag1/2 are important for maintaining esophageal and forestomach homeostasis and the onset of foregut SCC.

KRT5 in-frame deletion in a family of German Shepherd dogs with split paw pad disease resembling localized epidermolysis bullosa simplex in human patients.

Split paw pad disease is a scarcely defined phenotype characterized by skin lesions on the paw pads of dogs. We studied a family of German Shepherd dogs, in which four dogs developed intermittent paw pad lesions and lameness. The paw pads of two of the affected dogs were biopsied and demonstrated cleft formation in the stratum spinosum and stratum corneum, the outermost layers of the epidermis. Whole genome sequencing data from an affected dog revealed a private heterozygous 18 bp in frame deletion in the KRT5 gene. The deletion NM_001346035.1:c.988_1005del or NP_001332964.1:p.(Asn330_Asp335del) is predicted to lead to a loss of six amino acids in the L12 linker domain of the encoded keratin 5. KRT5 variants in human patients lead to various subtypes of epidermolysis bullosa simplex (EBS). Localized EBS is the mildest of the KRT5-related human diseases and may be caused by variants affecting the L12 linker domain of keratin 5. We therefore think that the detected KRT5 deletion in dogs represents a candidate causal variant for the observed skin lesions in dogs. However, while the clinical phenotype of KRT5-mutant dogs of this study closely resembles human patients with localized EBS, there are differences in the histopathology. EBS is defined by cleft formation within the basal layer of the epidermis while the cleft formation in the dogs described herein occurred in the outermost layers, a hallmark of split paw pad disease. Our study provides a basis for further studies into the exact relation of split paw pad disease and EBS.

Cell-Autonomous and Non-Cell-Autonomous Mechanisms Concomitantly Regulate the Early Developmental Pattern in the Kelp Saccharina latissima Embryo.

Brown algae are multicellular organisms that have evolved independently from plants and animals. Knowledge of the mechanisms involved in their embryogenesis is available only for the Fucus, Dictyota, and Ectocarpus, which are brown algae belonging to three different orders. Here, we address the control of cell growth and cell division orientation in the embryo of Saccharina latissima, a brown alga belonging to the order Laminariales, which grows as a stack of cells through transverse cell divisions until growth is initiated along the perpendicular axis. Using laser ablation, we show that apical and basal cells have different functions in the embryogenesis of this alga, with the apical cell being involved mainly in growth and basal cells controlling the orientation of cell division by inhibiting longitudinal cell division and thereby the widening of the embryo. These functions were observed in the very early development before the embryo reached the 8-cell stage. In addition, the growth of the apical and basal regions appears to be cell-autonomous, because there was no compensation for the loss of a significant part of the embryo upon laser ablation, resulting in smaller and less elongated embryos compared with intact embryos. In contrast, the orientation of cell division in the apical region of the embryo appears to be controlled by the basal cell only, which suggests a polarised, non-cell-autonomous mechanism. Altogether, our results shed light on the early mechanisms of growth rate and growth orientation at the onset of the embryogenesis of Saccharina, in which non-cell-specific cell-autonomous and cell-specific non-cell-autonomous processes are involved. This complex control differs from the mechanisms described in the other brown algal embryos, in which the establishment of embryo polarity depends on environmental cues.

Volatile Organic Compounds in Cellular Headspace after Hyperbaric Oxygen Exposure: An In Vitro Pilot Study.

Volatile organic compounds (VOCs) might be associated with pulmonary oxygen toxicity (POT). This pilot study aims to identify VOCs linked to oxidative stress employing an in vitro model of alveolar basal epithelial cells exposed to hyperbaric and hyperoxic conditions. In addition, the feasibility of this in vitro model for POT biomarker research was evaluated. The hyperbaric exposure protocol, similar to the U.S. Navy Treatment Table 6, was conducted on human alveolar basal epithelial cells, and the headspace VOCs were analyzed using gas chromatography-mass spectrometry. Three compounds (nonane [p = 0.005], octanal [p = 0.009], and decane [p = 0.018]), of which nonane and decane were also identified in a previous in vivo study with similar hyperbaric exposure, varied significantly between the intervention group which was exposed to 100% oxygen and the control group which was exposed to compressed air. VOC signal intensities were lower in the intervention group, but cellular stress markers (IL8 and LDH) confirmed increased stress and injury in the intervention group. Despite the observed reductions in compound expression, the model holds promise for POT biomarker exploration, emphasizing the need for further investigation into the complex relationship between VOCs and oxidative stress.

Pulse Dosing Vismodegib Therapy as an Effective Treatment of Basal Cell Carcinoma: A Case Report

Basal cell carcinoma (BCC) is a common nonmelanoma skin cancer, frequently present on the face and head. BCC is linked to the Sonic Hedgehog (Shh) signaling pathway. Mutations within the Shh signaling pathway, involving the activation of the ligand-independent pathway by the Smoothened (Smo) protein, can lead to unregulated proliferation of basal cells, resulting in BCC. Vismodegib, a hedgehog pathway inhibitor, is a chemotherapy drug approved for targeting the Shh signaling pathway. We herein report a presentation of nodular BCC in a Caucasian female who was treated with Vismodegib. This case highlights the effectiveness of pulse dosing treatment to minimize side effects.

Efficacy and Safety of Asparagusic Acid against Echinococcus multilocularis In Vitro and in a Murine Infection Model.

Alveolar echinococcosis (AE) stands as a perilous zoonotic affliction caused by the larvae of Echinococcus multilocularis. There is an imperative need to explore novel therapeutic agents or lead compounds for the treatment of AE. Asparagusic acid, characterized by its low toxicity and possessing antimicrobial, antioxidant, and anti-parasitic attributes, emerges as a promising candidate. The aim of this study was to investigate the in vivo and in vitro efficacy of asparagusic acid against E. multilocularis. Morphological observations, scanning electron microscopy, ROS assays, mitochondrial membrane potential assays, and Western blot were used to evaluate the in vitro effects of asparagusic acid on protoscoleces. The effects of asparagusic acid on vesicles were assessed via PGI release, γ-GGT release, and transmission electron microscopy observations. CellTiter-Glo assays, Caspase3 activity assays, flow cytometry, and Western blot were used for an evaluation of the effect of asparaginic acid on the proliferation and apoptosis of germinal cells. The in vivo efficacy of asparagusic acid was evaluated in a murine AE model. Asparagusic acid exhibited a pronounced killing effect on the protoscoleces post-treatment. Following an intervention with asparagusic acid, there was an increase in ROS levels and a decline in mitochondrial membrane potential in the protoscolex. Moreover, asparagusic acid treatment resulted in the upregulation of PGI and γ-GGT release in metacestode vesicles, concomitant with the inhibition of germinal cell viability. Furthermore, asparagusic acid led to an enhanced relative expression of Caspase3 in the culture supernatant of both the protoscoleces and germinal cells, accompanied by an increase in the proportion of apoptotic germinal cells. Notably, asparagusic acid induced an augmentation in Bax and Caspase3 protein expression while reducing Bcl2 protein expression in both the protoscoleces and germinal cells. In vitro cytotoxicity assessments demonstrated the low toxicity of asparagusic acid towards normal human hepatocytes and HFF cells. Additionally, in vivo experiments revealed that asparagusic acid administration at doses of 10 mg/kg and 40 mg/kg significantly reduced metacestode wet weight. A histopathological analysis displayed the disruption of the germinal layer structure within lesions post-asparagusic acid treatment, alongside the preservation of laminated layer structures. Transmission electron microscopy further revealed mitochondrial swelling and heightened cell necrosis subsequent to the asparagusic acid treatment. Furthermore, asparagusic acid promoted Caspase3 and Bax protein expression while decreasing Bcl2 protein expression in perilesional tissues. Subsequently, it inhibited the expression of Ki67, MMP2, and MMP9 proteins in the perilesional tissues and curbed the activation of the PI3K/Akt signaling pathway within the lesion-host microenvironmental tissues. Asparagusic acid demonstrated a pronounced killing effect on E. multilocularis, suggesting its potential as a promising therapeutic agent for the management of AE.

Developmental events in the mandibular salivary gland of Indian sheep (Ovis aries): Morphological and histochemical studies.

At 22nd day of fetal development, the primordial anlage of mandibular gland was first noticed as a solid epithelial bud from oral epithelium. The terminal buds were arranged in the form of clusters with undifferentiated epithelial cells and terminated in a bulb like structure in 28-day-old fetus. The lumenization and branching of the main cord was noticed at 35th day. The primary septa, which divide the glandular mass into lobes was observed from 53rd day onwards which resulted in the formation of distinct lobulation at 58th day. At 61st day, the capsule formation was initiated by the aggregation of mesenchymal tissue. The terminal tubules differentiated to form the secretory end pieces and the tubular portion leads to the formation of intercalated and striated ducts at 98th day. Predominantly mucous types of acinar cells were seen from 108th day onwards. The number of lobules increased with steep increase in parenchyma from 128th day onwards. Micrometrical studies revealed that the mean diameter of acinar cells and all ducts was increased with the advancement of age and the significant differences were observed between groups. Localization of acidic and neutral mucopolysaccharides was observed in mucous cells and goblet cells. RESEARCH HIGHLIGHTS: The primordial anlage of mandibular salivary gland was seen at 22nd day. Lobulation of gland was appeared at 53rd day of development, however; it was completed at 58th day. At 98th day, the terminal tubules differentiated to form the secretory end pieces. The parenchyma of the gland showed predominantly mucous type of cells from 108th day onwards. Myoepithelial cells were first appeared as flattened basal cells initially around the developing acinar cells at 132nd day. Localization of acidic as well as neutral mucopolysaccharides was observed in mucous cells and goblet cells. Fine lipid droplets were observed in intralobular as well as interlobular connective tissue, however; phospholipids were observed in the cell membrane of secretory cells and ducts.