Effects of extracellular calcium on the growth-differentiation switch in immortalized keratinocyte HaCaT cells compared with normal human keratinocytes

Novel 3D printed polysaccharide-based materials with prebiotic activity for potential treatment of diaper rash

Diaper rash, mainly occurring as erythema and itching in the diaper area, causes considerable distress to infants and toddlers. Increasing evidence suggests that an unequal distribution of microorganisms on the skin contributes to the development of diaper dermatitis. Probiotic bacteria, like Staphylococcus epidermidis, are crucial for maintaining a healthy balance in the skin's microbiome, among others, through their fermentative metabolites, such as short-chain fatty acids. Using a defined prebiotic as a carbon source (e.g., as part of the diaper formulation) can selectively trigger the fermentation of probiotic bacteria. A proper material choice can reduce diaper rash incidence by diminishing the skin exposure to wetness and faeces. Using 3D printing, we fabricated carbon-rich materials for the top sheet layer of baby diapers that enhance the probiotic activity of S. epidermidis. The developed materials' printability, chemical composition, swelling ability, and degradation rate were analysed. In addition, microbiological tests evaluated their potential as a source of in situ short-chain fatty acid production. Finally, biocompatibility testing with skin cells evaluated their safety for potential use as part of diapers. The results demonstrate a cost-effective approach for producing novel materials that can tailor the ecological balance of the skin microflora and help treat diaper rash.

PRSS3/mesotrypsin as a putative regulator of the biophysical characteristics of epidermal keratinocytes in superficial layers

Mesotrypsin, encoded by the PRSS3 gene, is a distinctive trypsin isoform renowned for its exceptional resistance to traditional trypsin inhibitors and unique substrate specificity. Within the skin epidermis, this protein primarily expresses in the upper layers of the stratified epidermis and plays a crucial role in processing pro-filaggrin (Pro-FLG). Although prior studies have partially elucidated its functions using primary cultured keratinocytes, challenges persist due to these cells' differentiation-activated cell death program. In the present study, HaCaT keratinocytes, characterized by minimal endogenous mesotrypsin expression and sustained proliferation in differentiated states, were utilized to further scrutinize the function of mesotrypsin. Despite the ready degradation of the intact form of active mesotrypsin in these cells, fusion with Venus, flanked by a peptide linker, enables evasion from the protein elimination machinery, thus facilitating activation of the Pro-FLG processing system. Inducing Venus-mesotrypsin expression in the cells resulted in a flattened phenotype and reduced proliferative capacity. Moreover, these cells displayed altered F-actin assembly, enhanced E-cadherin adhesive activity, and facilitated tight junction formation without overtly influencing epidermal differentiation. These findings underscore mesotrypsin's potentially pivotal role in shaping the characteristic cellular morphology of upper epidermal layers.

TASL mediates keratinocyte differentiation by regulating intracellular calcium levels and lysosomal function

Maintaining epidermal homeostasis relies on a tightly organized process of proliferation and differentiation of keratinocytes. While past studies have primarily focused on calcium regulation in keratinocyte differentiation, recent research has shed light on the crucial role of lysosome dysfunction in this process. TLR adaptor interacting with SLC15A4 on the lysosome (TASL) plays a role in regulating pH within the endo-lysosome. However, the specific role of TASL in keratinocyte differentiation and its potential impact on proliferation remains elusive. In our study, we discovered that TASL deficiency hinders the proliferation and migration of keratinocytes by inducing G1/S cell cycle arrest. Also, TASL deficiency disrupts proper differentiation process in TASL knockout human keratinocyte cell line (HaCaT) by affecting lysosomal function. Additionally, our research into calcium-induced differentiation showed that TASL deficiency affects calcium modulation, which is essential for keratinocyte regulation. These findings unveil a novel role of TASL in the proliferation and differentiation of keratinocytes, providing new insights into the intricate regulatory mechanisms of keratinocyte biology.

The decline in cellular iron is crucial for differentiation in keratinocytes

Iron is a vital metal for most biological functions in tissues, and its concentration is exquisitely regulated at the cellular level. During the process of differentiation, keratinocytes in the epidermis undergo a noticeable reduction in iron content. Conversely, psoriatic lesions, characterized by disruptions in epidermal differentiation, frequently reveal an excessive accumulation of iron within keratinocytes that have undergone differentiation. In this study, we clarified the significance of attenuated cellular iron content in the intricate course of epidermal differentiation. We illustrated this phenomenon through the utilization of hinokitiol, an iron chelator derived from the heartwood of Taiwanese hinoki, which forcibly delivers iron into cells independent of the intrinsic iron-regulation systems. While primary cultured keratinocytes readily succumbed to necrotic cell death by this iron chelator, mild administration of the hinokitiol-iron complex modestly disrupts the process of differentiation in these cells. Notably, keratinocyte model cells HaCaT and anaplastic skin rudiments exhibit remarkable resilience against the cytotoxic impact of hinokitiol, and the potent artificial influx of iron explains a suppressive effect selectively on epidermal differentiation. Moreover, the augmentation of iron content induced by the overexpression of divalent metal transporter 1 culminates in the inhibition of differentiation in HaCaT cells. Consequently, the diminution in cellular iron content emerges as an important determinant influencing the trajectory of keratinocyte differentiation.

The GRHL3-regulated long non-coding RNA lnc-DC modulates keratinocytes differentiation by interacting with IGF2BP2 and up-regulating ZNF750

BACKGROUND

Aberrant keratinocytes differentiation has been demonstrated to be associated with a number of skin diseases. The roles of lncRNAs in keratinocytes differentiation remain to be largely unknown.

OBJECTIVE

Here we aim to investigate the role of lnc-DC in regulating epidermal keratinocytes differentiation.

METHODS

Expression of lnc-DC in the skin was queried in AnnoLnc and verified by FISH. The lncRNA expression profiles during keratinocytes differentiation were reanalyzed and verified by qPCR and FISH. Gene knock-down and over-expression were used to explore the role of lnc-DC in keratinocytes differentiation. The downstream target of lnc-DC was screened by whole transcriptome sequencing. CUT&RUN assay and siRNAs transfection was used to reveal the regulatory effect of GRHL3 on lnc-DC. The mechanism of lnc-DC regulating ZNF750 was revealed by RIP assay and RNA stability assay.

RESULTS

Lnc-DC was biasedly expressed in skin and up-regulated during epidermal keratinocytes differentiation. Knockdown lnc-DC repressed epidermal keratinocytes differentiation while over-express lnc-DC showed the opposite effect. GRHL3, a well-known transcription factor regulating keratinocytes differentiation, could bind to the promoter of lnc-DC and regulate its expression. By whole transcriptome sequencing, we identified that ZNF750 was a downstream target of lnc-DC during keratinocytes differentiation. Mechanistically, lnc-DC interacted with RNA binding protein IGF2BP2 to stabilize ZNF750 mRNA and up- regulated its downstream targets TINCR and KLF4.

CONCLUSION

Our study revealed the novel role of GRHL3/lnc-DC/ZNF750 axis in regulating epidermal keratinocytes differentiation, which may provide new therapeutic targets of aberrant keratinocytes differentiation related skin diseases.

CAMSAP3, a microtubule orientation regulator, plays a vital role in manifesting differentiation-dependent characteristics in keratinocytes

Microtubules constitute pivotal structural elements integral to cellular architecture and physiological functionality. Within the epidermis of the skin, microtubules undergo a noteworthy transition in orientation, shifting from centrosomal to non-centrosomal configurations during the processes of differentiation and stratification. This transition aligns with a discernible increase in the expression of CAMSAP3, a protein that binds to the minus end of microtubules, thereby regulating their orientation. In this study, we identified microtubule-bound CAMSAP3 within HaCaT keratinocytes, revealing an upregulation during the mitotic phase and accumulation at the intercellular bridge during cytokinesis. Building upon this observation, we scrutinized cellular responses upon a tetracycline/doxycycline-inducible CAMSAP3 expression in CAMSAP3-deficient HaCaT cells. Remarkably, CAMSAP3 deficiency induced shifts in microtubule orientation, resulting in cell cycle exit and delayed cytokinesis in a subset of the cells. Furthermore, our inquiry unveiled that CAMSAP3 deficiency adversely impacted the formation and stability of Adherens Junctions and Tight Junctions. In contrast, these perturbations were rectified upon the re-expression of CAMSAP3, underscoring the pivotal role of CAMSAP3 in manifesting differentiation-dependent characteristics in stratified keratinocytes. These observations emphasize the significance of CAMSAP3 in maintaining epidermal homeostasis.

Quantitative Analysis and Molecular Docking Simulation of Flavonols from Eruca sativa Mill. and Their Effect on Skin Barrier Function

Eruca sativa is a commonly used edible plant in Italian cuisine. E. sativa 70% ethanol extract (ES) was fractionated with five organic solvents, including n-hexane (EHex), chloroform (ECHCl3), ethyl acetate (EEA), n-butyl alcohol (EBuOH), and water (EDW). Ethyl acetate fraction (EEA) had the highest antioxidant activity, which was correlated with the total polyphenol and flavonoid content. ES and EEA acted as PPAR-α ligands by PPAR-α competitive binding assay. EEA significantly increased cornified envelope formation as a keratinocyte terminal differentiation marker in HaCaT cells. Further, it significantly reduced nitric oxide and pro-inflammatory cytokines (IL-6 and TNF-α) in lipopolysaccharide-stimulated RAW 264.7 cells. The main flavonol forms detected in high amounts from EEA are mono-and di-glycoside of each aglycone. The main flavonol form of EEA is the mono-glycoside of each aglycone detected, and the most abundant flavonol mono-glycoside is kaempferol 3-glucoside 7.4%, followed by quercetin-3-glucoside 2.3% and isorhamnetin 3-glucoside 1.4%. Flavonol mono-glycosides were shown to be a potent PPAR-α ligand using molecular docking simulation and showed the inhibition of nitric oxide. These results suggest that the flavonol composition of E. sativa is suitable for use in improving skin barrier function and inflammation in skin disorders, such as atopic dermatitis.

Different immortalized keratinocyte cell lines display distinct capabilities to differentiate and reconstitute an epidermis in vitro

Dermatological research relies on the availability of suitable models that most accurately reflect the in vivo situation. Primary keratinocytes obtained from skin reduction surgeries are not only limited by availability but have a short lifespan and show donor-specific variations, which hamper the understanding of general mechanisms. The spontaneously immortalized keratinocyte cell line HaCaT displays chromosomal aberrations and is known to differentiate in an abnormal manner. To overcome these issues, we validated different engineered immortalized cell lines created from primary human keratinocytes (NHK) as model systems to study epidermal function. Cell lines either immortalized by the expression of SV40 large T antigen and hTERT (NHK-SV/TERT) or by transduction with HPV E6/E7 (NHK-E6/E7) were analysed for their growth and differentiation behaviour using 2D and 3D culture systems and compared to primary keratinocytes. Both cell lines displayed a robust proliferative behaviour but were still sensitive to contact inhibition. NHK-E6/E7 could be driven into differentiation by Ca2+ switch, while NHK-SV/TERT needed withdrawal from any proliferative signal to initiate a delayed onset of differentiation. In 3D epidermal models both cell lines were able to reconstitute a stratified epidermis and functional epidermal barrier. However, only NHK-E6/E7 showed a degree of epidermal maturation and stratification that was comparable to primary keratinocytes.

Glycyrol Prevents the Progression of Psoriasis-like Skin Inflammation via Immunosuppressive and Anti-Inflammatory Actions

Glycyrol (GC) is one natural active product. Imiquimod-induced psoriasis-like Balb/c mouse models were established. The model mice were intraperitoneally injected with cyclosporine A (CsA) and GC for 8 days followed by a series of biological detections. GC had little toxicity according to the levels of peripheral blood cells, hemoglobin, blood urea nitrogen (BUN), and serum creatinine (CRE), while CsA significantly increased the levels of BUN and CRE. GC decreased the splenic index and reduced the expressions of IL-6, IL-23, and CXCL-3 in the model mice and IL-6, CXCL-1, and CXCL-2 in the inflammatory HaCaT cells. The half inhibition concentration (IC50) of GC on HaCaT cells was 29.72 μmol/L, resulting in improved apoptosis, enhanced expressions of p21, BAX, and BIK, and reduced expressions of BCL-2. GC is an immunosuppressive agent against psoriasis-like symptoms by anti-inflammatory effects, which provides a strategy for the discovery of anti-psoriatic natural products.

Distinct signatures on d-galactose-induced aging and preventive/protective potency of two low-dose vitamin D supplementation regimens on working memory, muscular damage, cardiac and cerebral oxidative stress, and SIRT1 and calstabin2 downregulation

Chronic administration of d-galactose (d-gal) in rodents reproduces the overproduction of reactive oxygen species of physiological aging. The present research shows for the first time distinct signatures on d-gal-induced aging (500 mg/kg, 6 weeks) and the preventive and protective potential of two vitamin D (50 IU) supplementation regimens (pre-induction and simultaneous, respectively) in two vital organs (heart and brain). d-gal-induced notorious alterations in working memory, a strong increase in brain malondialdehyde (MDA) oxidative levels, and strong downregulation of sirtuin 1 (SIRT1) in the heart and hippocampus and of calstabin2 in the heart. Cardiac and brain superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic antioxidant capacities were damaged, brain calstabin2 was downregulated, and neuropathology was observed. Heart damage also included a moderate increase in MDA levels, serologic lactate dehydrogenase (LDH), total creatine kinase (CK) activities, and histopathological alterations. The used dose of vitamin D was enough to prevent cognitive impairment, avoid muscular damage, hamper cardiac and cerebral oxidative stress, and SIRT1 and calstabin2 downregulation. Most importantly, the potencies of the two preventive schedules depended on the tissue and level of study. The pre-induction schedule prevented d-gal-induced aging by 1 order of magnitude higher than simultaneous administration in all the variables studied except for SIRT1, whose strong downregulation induced by d-gal was equally prevented by both schedules. The benefits of vitamin D for oxidative stress were stronger in the brain than in the heart. Brain MDA levels were more sensitive to damage, while SOD and GPx antioxidant enzymatic activities were in the heart. In this order, the magnitude of SOD, MDA, and GPx oxidative stress markers was sensitive to prevention. In summary, the results unveiled distinct aging induction, preventive signatures, and sensitivity of markers depending on different levels of study and tissues, which are relevant from a mechanistic view and in the design of targeted interventions.

Role of syntaxin3 an apical polarity protein in poorly polarized keratinocytes: regulation of asymmetric barrier formations in the skin epidermis

The skin epidermis exhibits an asymmetric structure composed of multilayered keratinocytes and those in the outer layers form two-way physical barriers, cornified cell envelope (CCE), and tight junctions (TJs). While undifferentiated keratinocytes in the basal layer continuously deliver daughter cells outward, which undergo successive differentiation with losing their polarized characteristics, they retain the expression of several polarity proteins. In the present study, we revealed that the t-SNARE protein syntaxin3, a critical element for the formation of the apical compartment in simple epithelial cells, is required to confer the ability to organize the physical barriers on "poorly polarized" keratinocytes in epidermal outer layers. HaCaT keratinocytes with genetic ablation of syntaxin3 readily succumbed to hydrogen peroxide-induced cell death. Additionally, they lost the ability to organize TJ and CCE structures, accompanied by notable downregulation of transglutaminase1 and caspase14 (a cornification regulator) expression. These syntaxin3-knockout cells appeared to restore oxidative stress tolerance and functional TJ formation ability, in response to the inducible re-expression of exogenous syntaxin3. While plausible mechanisms underlying these phenomena remain unclear, syntaxin3, an apical polarity protein in the simple epithelia, has emerged as a potentially crucial element for barrier formation in poorly polarized keratinocytes in polarized epidermal tissue.

Salicylic Acid Release from Syndiotactic Polystyrene Staple Fibers

Films and fibers of syndiotactic polystyrene (sPS), being amorphous or exhibiting nanoporous crystalline (NC) or dense crystalline phases, were loaded with salicylic acid (SA), a relevant non-volatile antimicrobial molecule. In the first section of the paper, sPS/SA co-crystalline (CC) δ form is characterized, mainly by wide angle X-ray diffraction (WAXD) patterns and polarized Fourier transform infrared (FTIR) spectra. The formation of sPS/SA δ CC phases allows the preparation of sPS fibers even with a high content of the antibacterial guest, which is also retained after repeated washing procedures at 65 °C. A preparation procedure starting from amorphous fibers is particularly appropriate because involves a direct formation of the CC δ form and a simultaneous axial orientation. The possibility of tuning drug amount and release kinetics, by simply selecting suitable crystalline phases of a commercially available polymer, makes sPS fibers possibly useful for many applications. In particular, fibers with δ CC forms, which retain SA molecules in their crystalline phases, could be useful for antimicrobial textiles and fabrics. Fibers with the dense γ form which easily release SA molecules, because they are only included in their amorphous phases, could be used for promising SA-based preparations for antibacterial purposes in food processing and preservation and public health. Finally, using a cell-based assay system and antibacterial tests, we investigated the cellular activity, toxicity and antimicrobial properties of amorphous, δ CC forms and dense γ form of sPS fibers loaded with different contents of SA.

Involvement of CacyBP/SIP in differentiation and the immune response of HaCaT keratinocytes

CacyBP/SIP is a multifunctional protein present in various cells and tissues. However, its expression and role in the epidermis has not been explored so far. In this work, using RT-qPCR, Western blot analysis and three-dimensional (3D) organotypic cultures of HaCaT keratinocytes we show that CacyBP/SIP is present in the epidermis. To investigate the possible role of CacyBP/SIP in keratinocytes we obtained CacyBP/SIP knockdown cells and studied the effect of CacyBP/SIP deficiency on their differentiation and response to viral infection. We found that CacyBP/SIP knockdown results in reduced expression of epidermal differentiation markers in both undifferentiated and differentiated HaCaT cells. Since epidermis is engaged in immune defense, the impact of CacyBP/SIP knockdown on this process was also analyzed. By applying RT-qPCR and Western blot it was found that poly(I:C), a synthetic analog of double-stranded RNA that mimics viral infection, stimulated the expression of genes involved in antiviral response, such as IFIT1, IFIT2 and OASL. Interestingly, following poly(I:C) stimulation, the level of expression of these genes was significantly lower in cells with CacyBP/SIP knockdown than control ones. Since the signaling pathway mediating cellular responses to viral infection involves, among others, the STAT1 transcription factor, we measured its activity using luciferase assay and found that it was lower in CacyBP/SIP knockdown HaCaT cells. Altogether, the presented results indicate that CacyBP/SIP promotes epidermal differentiation and might be involved in response of the skin cells to viral infection.

The role of cytokines/chemokines in an aging skin immune microenvironment

Reversing or slowing down the skin aging process is one of the most intriguing areas of focus across the social and scientific communities around the world. While aging is considered a universal and inevitable natural process of physiological decline, the aging of the skin is the most apparent visual representation of an individual's health. Aging skin may be objectively defined by epidermal thinning; increased transepidermal water loss; decreased cutaneous barrier function; loss of elasticity, laxity, and textured appearance; and gradual deterioration of the epidermal immune environment. As the largest structure of the immune system and of the body as a whole, the skin is the most vulnerable barrier of defense against the environment. The skin reflects an individual's exposures, lifestyle habits, and overall health. From an immunological perspective, cytokines and chemokines act as a central character in the communicating of the immunity in skin aging. These cell signaling proteins serve as the intercellular communication link. This review aims to elucidate how cell-cell crosstalk through cytokines and chemokines, and the interplay between host cells, infiltrating immune cells, and exogenous factors contribute to the overall aging skin.

Cyclic-di-GMP stimulates keratinocyte innate immune responses and attenuates methicillin-resistant Staphylococcus aureus colonization in a murine skin wound infection model

Background

Staphylococcus aureus is a leading cause for morbidity and mortality associated with skin and burn wound infections. Therapeutic options for methicillin-resistant S. aureus (MRSA) have dwindled and therefore alternative treatments are urgently needed. In this study, the immuno-stimulating and anti-MRSA effects of cyclic di-guanosine monophosphate (c-di-GMP), a uniquely bacterial second messenger and immuno-modulator, were investigated in HaCaT human epidermal keratinocytes and a murine skin wound infection model.

Results

Stimulation of HaCaT cells with 125 μM c-di-GMP for 12 h prior to MRSA challenge resulted in a 20-fold reduction in bacterial colonization compared with untreated control cells, which was not the result of a direct c-di-GMP toxic effect, since bacterial viability was not affected by this dose in the absence of HaCaT cells. C-di-GMP-stimulated or MRSA-challenged HaCaT cells displayed enhanced secretion of the antimicrobial peptides human β-defensin 1 (hBD-1), hBD-2, hBD-3 and LL-37, but for hBD1 and LL-37 the responses were additive in a c-di-GMP-dose-dependent manner. Secretion of the chemokines CXCL1 and CXCL8 was also elevated after stimulation of HaCaT cells with lower c-di-GMP doses and peaked at a dose of 5 μM. Finally, pre-treatment of mice with a 200 nmol dose of c-di-GMP 24 h before a challenge with MRSA in skin wound infection model resulted in a major reduction (up to 1,100-fold by day 2) in bacterial CFU counts recovered from challenged skin tissue sections compared PBS-treated control animals. Tissue sections displayed inflammatory cell infiltration and enhanced neutrophil influx in the c-di-GMP pre-treated animals, which might account for the reduced ability of MRSA to colonize c-di-GMP pre-treated mice.

Conclusions

These results demonstrate that c-di-GMP is a potent immuno-modulator that can stimulate anti-MRSA immune responses in vivo and might therefore be a suitable alternative prophylactic or therapeutic agent for MRSA skin or burn wound infections.

The Comparison of the Efficiency of Emodin and Aloe-Emodin in Photodynamic Therapy

Skin cancer (melanoma and non-melanoma) is the most frequent type of malignancy in the Caucasian population. Photodynamic therapy (PDT) as an interesting and unique strategy may potentially boost standard therapeutic approaches. In the present study, the potential of emodin and aloe-emodin as photosensitizers in photodynamic therapy has been investigated. The conducted research presents for the first-time comparison of the phototoxic and anti-cancerous effects of emodin and aloe-emodin on skin cancer cell lines, including SCC-25 representing cutaneous squamous cell carcinoma, MUG-Mel2 representing a melanoma cell line, and normal human keratinocytes HaCaT representing control normal skin cells. To assess the effectiveness of emodin and aloe-emodin as a photosensitizer in PDT on different skin cell lines, we performed MTT assay measuring cytotoxicity of natural compounds, cellular uptake, apoptosis with flow cytometry, and a wound-healing assay. Although emodin and aloe-emodin are isomers and differ only in the position of one hydroxyl group, our phototoxicity and apoptosis detection results show that both substances affect skin cancer cells (SSC-25 squamous cell carcinoma and MUG-Mel2 melanoma) and normal keratinocytes (HaCaT cell line) in other ways. In conclusion, our study provides evidence suggesting that emodin and aloe-emodin mediated PDT exhibits the potential for clinical development as a new effective and safe photosensitizer to treat skin cancer.

Activation and Migration of Human Skeletal Muscle Stem Cells In Vitro Differently Rely on Calcium Signals

Muscle regeneration is essential for proper muscle homeostasis and relies primarily on muscle stem cells (MuSC). MuSC are maintained quiescent in their niche and can be activated following muscle injury. Using an in vitro model of primary human quiescent MuSC (called reserve cells, RC), we analyzed their Ca²⁺ response following their activation by fetal calf serum and assessed the role of Ca²⁺ in the processes of RC activation and migration. The results showed that RC displayed a high response heterogeneity in a cell-dependent manner following serum stimulation. Most of these responses relied on inositol 1,4,5-trisphosphate (IP₃)-dependent Ca²⁺ release associated with Ca²⁺ influx, partly due to store-operated calcium entry. Our study further found that blocking the IP₃ production, Ca²⁺ influx, or both did not prevent the activation of RC. Intra- or extracellular Ca²⁺ chelation did not impede RC activation. However, their migration potential depended on Ca²⁺ responses displayed upon stimulation, and Ca²⁺ blockers inhibited their movement. We conclude that the two major steps of muscle regeneration, namely the activation and migration of MuSC, differently rely on Ca²⁺ signals.

Pitfalls in the Application of Dispase-Based Keratinocyte Dissociation Assay for In Vitro Analysis of Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a chronic, life-altering autoimmune disease due to the production of anti-desmoglein antibodies causing the loss of cell–cell adhesion in keratinocytes (acantholysis) and blister formation in both skin and mucous membranes. The dispase-based keratinocyte dissociation assay (DDA) is the method of choice to examine the pathogenic effect of antibodies and additional co-stimuli on cell adhesion in vitro. Despite its widespread use, there is a high variability of experimental conditions, leading to inconsistent results. In this paper, we identify and discuss pitfalls in the application of DDA, including generation of a monolayer with optimized density, appropriate culturing conditions to obtain said monolayer, application of mechanical stress in a standardized manner, and performing consistent data processing. Importantly, we describe a detailed protocol for a successful and reliable DDA and the respective ideal conditions for three different types of human keratinocytes: (1) primary keratinocytes, (2) the HaCaT spontaneously immortalized keratinocyte cell line, and (3) the recently characterized HaSKpw spontaneously immortalized keratinocyte cell line. Our study provides detailed protocols which guarantee intra- and inter-experimental comparability of DDA.

Konjac Ceramide (kCer)-Mediated Signal Transduction of the Sema3A Pathway Promotes HaCaT Keratinocyte Differentiation

Simple Summary

Konjac ceramide (kCer) is a unique molecular species of plant-type ceramide, and is a potential Sema3A-like ligand of Nrp1. kCer suppresses histamine-stimulated cell migration of HaCaT keratinocytes. This effect of kCer is not due to histamine-activated GPCRs, but rather to Sema3A-Nrp1 receptor binding. The present study focused on the ability of kCer to induce cell differentiation, in addition to its anti-migratory effects. We demonstrated that the effects of kCer on cell migration and cell differentiation are perpetuated by a cascade of crosstalk between pathways downstream of Nrp1 and GPCR in HaCaT cells.

Abstract

Histamines suppress epidermal keratinocyte differentiation. Previously, we reported that konjac ceramide (kCer) suppresses histamine-stimulated cell migration of HaCaT keratinocytes. kCer specifically binds to Nrp1 and does not interact with histamine receptors. The signaling mechanism of kCer in HaCaT cells is also controlled by an intracellular signaling cascade activated by the Sema3A-Nrp1 pathway. In the present study, we demonstrated that kCer treatment induced HaCaT keratinocyte differentiation after migration of immature cells. kCer-induced HaCaT cell differentiation was accompanied by some features of keratinocyte differentiation markers. kCer induced activating phosphorylation of p38MAPK and c-Fos, which increased the protein levels of involucrin that was the latter differentiation marker. In addition, we demonstrated that the effects of both kCer and histamines are regulated by an intracellular mechanism of Rac1 activation/RhoA inhibition downstream of the Sema3A/Nrp1 receptor and histamine/GPCR pathways. In summary, the effects of kCer on cell migration and cell differentiation are regulated by cascade crosstalk between downstream Nrp1 and histamine-GPCR pathways in HaCaT cells.

Dermal exposure to cobalt studied in vitro in keratinocytes - effects of cobalt exposure on inflammasome activated cytokines, and mRNA response

BACKGROUND

Cobalt is a dermal sensitizer, and keratinocytes respond to cobalt exposure by releasing proinflammatory mediators, regulating the immune response.

OBJECTIVE

To determine the effect of cobalt on the inflammasome associated cytokine- and gene expression in cultured human keratinocytes (HaCaT). Cultivation in low- or high calcium conditions model separate differentiation states of keratinocytes in the skin.

METHOD

HaCaT cells in two different states of differentiation were exposed to cobalt chloride and caspase-1 activity as well as the production of IL-1β, IL-18 and gene expression of IL1B, IL18, NLRP3, CASP1, and PYCARD was quantified.

RESULTS

High cobalt chloride exposure mediated significant increase in caspase-1 activity, cytokine levels, and IL1B and NLRP3 expression with a corresponding regulatory decrease for CASP1 and PYCARD expression. No difference between high- and low calcium culturing conditions modelling differentiation states was detected.

CONCLUSIONS

Our data suggest that HaCaT cells respond with inflammmasome associated activity upon cobalt exposure in a concentration-dependent manner. These mechanisms could be of importance for the understanding of the pathophysiology behind allergic sensitization to dermal cobalt exposure.

Dose- and time-dependent changes in viability and IL-6, CXCL8 and CCL2 production by HaCaT-cells exposed to cobalt. Effects of high and low calcium growth conditions

Background

Sensitization requires exposure to an allergen with subsequent production of a “danger “signal. In the skin, keratinocytes are the main producers of these signals.

Objective

To compare dose- and time-effects of cobalt on the viability of and cytokine release from HaCaT cells cultured at low or high calcium.

Method

To model two separate states of differentiation of keratinocytes, HaCaT cells were cultured under low or high calcium conditions. HaCaT were exposed to different concentrations of cobalt chloride (10 μm to 5 mM) over time (30 minutes– 48 hours). Cell viability was measured with the Cell-Titer Blue Viability assay. Cytokine production was measured using a bead-based immunoassay and flow cytometry. Gene expression was quantified using qPCR. Data was analyzed by ANOVA and linear mixed model.

Results

Viability of the cells was dose- and time-dependent. A linear mixed statistical model showed that cobalt exposure induces increase in IL-6, CXCL8 and CCL2 production over time and whereas increase of IL-6 and a decrease of CCL2 was associated with increasing cobalt chloride concentrations. When comparing the cells incubated under high and low calcium conditions, the more differentiated cells in the high concentration were found to exert a stronger response in terms of IL-6 release.

Conclusions

Our data suggest that cobalt chloride triggered an alarm system in HaCaT cells, and proinflammatory cytokines/chemokines were secreted in a dose- and time-dependent manner. When high and low calcium incubations were compared, the difference was seen only for IL-6. These findings indicate that the effect of cobalt chloride on cell toxicity occurs throughout the living epidermis.

Porphyrins produced by acneic Cutibacterium acnes strains activate the inflammasome by inducing K+ leakage

Some Cutibacterium acnes subgroups dominate on healthy skin, whereas others are frequently acne associated. Here we provide mechanistic insights into this difference, using an anaerobic keratinocyte-sebocyte-C. acnes co-culture model. An acneic C. acnes strain as well as its porphyrins activates NRLP3 inflammasome assembly, whereas this was not observed with a non-acneic strain. Low levels of intracellular K⁺ in keratinocytes stimulated with extracted porphyrins or infected with the acneic strain were observed, identifying porphyrin-induced K⁺ leakage as trigger for inflammasome activation. Using a panel of C. acnes strains, we found that porphyrin production and IL-1β release are correlated and are higher in acneic strains. This demonstrates that the latter produce more porphyrins, which interact with the keratinocyte cell membrane, leading to K⁺ leakage, NLRP3 inflammasome activation, and IL-1β release and provides an explanation for the observation that some C. acnes strains are associated with healthy skin, whereas others dominate in acneic skin.

•

We developed an anaerobic keratinocyte-sebocyte-C. acnes co-culture model

•

Acneic C. acnes strains and their porphyrins activate NRLP3 inflammasome assembly

•

Activation of the NRLP3 inflammasome is not observed in non-acneic strains

•

Porphyrins from acneic C. acnes activate the inflammasome by inducing K⁺ leakage

The Comparison of In Vitro Photosensitizing Efficacy of Curcumin-Loaded Liposomes Following Photodynamic Therapy on Melanoma MUG-Mel2, Squamous Cell Carcinoma SCC-25, and Normal Keratinocyte HaCaT Cells

The research focused on the investigation of curcumin encapsulated in hydrogenated soy phosphatidylcholine liposomes and its increased photoactive properties in photodynamic therapy (PDT). The goal of this study was two-fold: to emphasize the role of a natural photoactive plant-based derivative in the liposomal formulation as an easily bioavailable, alternative photosensitizer (PS) for the use in PDT of skin malignancies. Furthermore, the goal includes to prove the decreased cytotoxicity of phototoxic agents loaded in liposomes toward normal skin cells. Research was conducted on melanoma (MugMel2), squamous cell carcinoma (SCC-25), and normal human keratinocytes (HaCaT) cell lines. The assessment of viability with MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) evaluated cell death after exposure to blue light irradiation after 4 h of pre-incubation with free and encapsulated curcumin. Additionally, the wound healing assay, flow cytometry, and immunocytochemistry to detect apoptosis were performed. The malignant cells revealed increased phototoxicity after the therapy in comparison to normal cells. Moreover, liposome curcumin-based photodynamic therapy showed an increased ratio of apoptotic and necrotic cells. The study also demonstrated that nanocurcumin significantly decreased malignant cell motility following PDT treatment. Acquired results suggest that liposomal formulation of a poor soluble natural compound may improve photosensitizing properties of curcumin-mediated PDT treatment in skin cancers and reduce toxicity in normal keratinocytes.

Hybrid 3D Printing of Advanced Hydrogel-Based Wound Dressings with Tailorable Properties

Despite the extensive utilization of polysaccharide hydrogels in regenerative medicine, current fabrication methods fail to produce mechanically stable scaffolds using only hydrogels. The recently developed hybrid extrusion-based bioprinting process promises to resolve these current issues by facilitating the simultaneous printing of stiff thermoplastic polymers and softer hydrogels at different temperatures. Using layer-by-layer deposition, mechanically advantageous scaffolds can be produced by integrating the softer hydrogel matrix into a stiffer synthetic framework. This work demonstrates the fabrication of hybrid hydrogel-thermoplastic polymer scaffolds with tunable structural and chemical properties for applications in tissue engineering and regenerative medicine. Through an alternating deposition of polycaprolactone and alginate/carboxymethylcellulose gel strands, scaffolds with the desired architecture (e.g., filament thickness, pore size, macro-/microporosity), and rheological characteristics (e.g., swelling capacity, degradation rate, and wettability) were prepared. The hybrid fabrication approach allows the fine-tuning of wettability (approx. 50–75°), swelling (approx. 0–20× increased mass), degradability (approx. 2–30+ days), and mechanical strength (approx. 0.2–11 MPa) in the range between pure hydrogels and pure thermoplastic polymers, while providing a gradient of surface properties and good biocompatibility. The controlled degradability and permeability of the hydrogel component may also enable controlled drug delivery. Our work shows that the novel hybrid hydrogel-thermoplastic scaffolds with adjustable characteristics have immense potential for tissue engineering and can serve as templates for developing novel wound dressings.

Profilin-1; a novel regulator of DNA damage response and repair machinery in keratinocytes

Profilin-1 (PFN1) regulates actin polymerization and cytoskeletal growth. Despite the essential roles of PFN1 in cell integration, its subcellular function in keratinocyte has not been elucidated yet. Here we characterize the specific regulation of PFN1 in DNA damage response and repair machinery. PFN1 depletion accelerated DNA damage-mediated apoptosis exhibiting PTEN loss of function instigated by increased phosphorylated inactivation followed by high levels of AKT activation. PFN1 changed its predominant cytoplasmic localization to the nucleus upon DNA damage and subsequently restored the cytoplasmic compartment during the recovery time. Even though γH2AX was recruited at the sites of DNA double strand breaks in response to DNA damage, PFN1-deficient cells failed to recruit DNA repair factors, whereas control cells exhibited significant increases of these genes. Additionally, PFN1 depletion resulted in disruption of PTEN-AKT cascade upon DNA damage and CHK1-mediated cell cycle arrest was not recovered even after the recovery time exhibiting γH2AX accumulation. This might suggest PFN1 roles in regulating DNA damage response and repair machinery to protect cells from DNA damage. Future studies addressing the crosstalk and regulation of PTEN-related DNA damage sensing and repair pathway choice by PFN1 may further aid to identify new mechanistic insights for various DNA repair disorders.

Effect of SUV39H1 Histone Methyltransferase Knockout on Expression of Differentiation-Associated Genes in HaCaT Keratinocytes

Keratinocytes undergo a complex differentiation process, coupled with extensive changes in gene expression through which they acquire distinctive features indispensable for cells that form the external body barrier—epidermis. Disturbed epidermal differentiation gives rise to multiple skin diseases. The involvement of epigenetic factors, such as DNA methylation or histone modifications, in the regulation of epidermal gene expression and differentiation has not been fully recognized yet. In this work we performed a CRISPR/Cas9-mediated knockout of SUV39H1, a gene-encoding H3K9 histone methyltransferase, in HaCaT cells that originate from spontaneously immortalized human keratinocytes and examined changes in the expression of selected differentiation-specific genes located in the epidermal differentiation complex (EDC) and other genomic locations by RT-qPCR. The studied genes revealed a diverse differentiation state-dependent or -independent response to a lower level of H3K9 methylation. We also show, by means of chromatin immunoprecipitation, that the expression of genes in the LCE1 subcluster of EDC was regulated by the extent of trimethylation of lysine 9 in histone H3 bound to their promoters. Changes in gene expression were accompanied by changes in HaCaT cell morphology and adhesion.

A Single-Cell Transcriptomic Atlas of Human Skin Aging

Skin undergoes constant self-renewal, and its functional decline is a visible consequence of aging. Understanding human skin aging requires in-depth knowledge of the molecular and functional properties of various skin cell types. We performed single-cell RNA sequencing of human eyelid skin from healthy individuals across different ages and identified eleven canonical cell types, as well as six subpopulations of basal cells. Further analysis revealed progressive accumulation of photoaging-related changes and increased chronic inflammation with age. Transcriptional factors involved in the developmental process underwent early-onset decline during aging. Furthermore, inhibition of key transcription factors HES1 in fibroblasts and KLF6 in keratinocytes not only compromised cell proliferation, but also increased inflammation and cellular senescence during aging. Lastly, we found that genetic activation of HES1 or pharmacological treatment with quercetin alleviated cellular senescence of dermal fibroblasts. These findings provide a single-cell molecular framework of human skin aging, providing a rich resource for developing therapeutic strategies against aging-related skin disorders.

Cutibacterium acnes Phylotype I and II Strains Interact Differently With Human Skin Cells

Acne vulgaris is one of the most common skin disorders and affects the pilosebaceous units. Although the exact pathogenesis of acne is still unknown, Cutibacterium acnes (formerly known as Propionibacterium acnes) is considered one of the key contributing factors. In fact, a significant association exists between C. acnes strains belonging to phylotype I and acne. However, there is still heavy debate on the exact role of C. acnes in acne and its behavior in the pilosebaceous unit, and more specifically its interactions with the human skin cells. In this study, key elements of the host-pathogen interaction were studied for a collection of C. acnes strains, belonging to phylotype I and II, including association with HaCaT keratinocytes and SZ95 sebocytes, the effect of C. acnes on keratinocyte tight junctions in a HaCaT monoculture and in an additional keratinocyte-sebocyte co-culture model, and C. acnes invasion through the keratinocyte cell layer. Our data showed association of all C. acnes strains to both skin cell lines, with a significantly higher association of type I strains compared to type II strains. Microscopic imaging and western blot analysis of the tight junction protein ZO-1, together with transepithelial electrical resistance (TEER) measurements revealed an initial induction of keratinocyte tight junctions after 24 h infection but a degradation after 48 h, demonstrating a decline in cell lining integrity during infection. Subsequently, C. acnes was able to invade after 48 h of infection, although invasion frequency was significantly higher for type II strains compared to type I strains.

Optimization of human papillomavirus-based pseudovirus techniques for efficient gene transfer

Human papillomavirus (HPV) L1 and L2 capsid proteins self-assemble into virions capable of efficiently packaging either its 8 kilobase genome or non-viral DNA. The ability of HPV capsids to package non-viral DNA makes these a useful tool for delivering plasmids to study proteins of interest in a variety of cell types. We describe optimization of current methods and present new protocols for using HPV capsids to deliver non-viral DNA thereby providing an alternative to DNA transfection. Using keratinocyte generated extracellular matrices can enhance infection efficiency in keratinocytes, hepatocytes and neuronal cells. Furthermore, we describe a suspension-based efficient technique for infecting different cell types.

Reduced serum methods for contact-based coculture of human dermal fibroblasts and epidermal keratinocytes

Direct contact-based coculture of human dermal fibroblasts and epidermal keratinocytes has been a long-standing and challenging issue owing to different serum and growth factor requirements of the two cell types. Existing protocols employ high serum concentrations (up to 10% fetal bovine serum), complex feeder systems and a range of supplemental factors. These approaches are technically demanding and labor intensive, and pose scientific and ethical limitations associated with the high concentrations of animal serum. On the other hand, serum-free conditions often fail to support the proliferation of one or both cell types when they are cultured together. We have developed two reduced serum approaches (1-2% serum) that support the contact-based coculture of human dermal fibroblasts and immortalized keratinocytes and enable the study of cell migration and wound closure.

Cultivation of Hair Matrix Cells from Cashmere Goat Skins and Exemplified Applications

Simple Summary

A large scale of sequencing data pertaining to cashmere growth on cashmere goats have not been cost-effectively used due to the lack of in vitro cellular models, especially for hair matrix cells (HMCs)—the precursors of hair-forming keratinocytes, causing an enormous waste of data resources. Herein, we successfully isolated and cultivated previously unreported HMCs from cashmere goat skins and identified them morphologically and molecularly via their distinct appearance and signature genes’ expression from spatially adjacent dermal papilla cells. Through monitoring the effects of calcium and all-trans retinoic acid on HMCs using various biological techniques, we displayed that the cells are useful models to explore unsolved issues in hair fiber growth on goats. Therefore, our present success paves the road for further utilizing currently deposited data to unveil the secrets of cashmere growth and, ultimately, improve the quantity and quality of animal fibers.

Abstract

A functional interpretation of filtered candidates and predicted regulatory pathways related to cashmere growth from sequencing trials needs available cell models, especially for hair matrix cells (HMCs), whose continual proliferation and differentiation result in rapid hair growth. To fulfill such goals, we herein obtained primary goat HMCs via a microdissection-based method; optimized the selection of the culture medium and coating substances for better cell maintenance; and exemplified their usefulness through examining the effects of calcium and all-trans retinoic acid (ATRA) on cells using immunoblotting, flow cytometry, and other techniques. As a result, we successfully acquired primary and passaged goat HMCs with typical keratinocyte morphology. Calcium-free RPMI (Roswell Park Memorial Institute) 1640 and MEM (minimum Eagle’s medium) outperformed normal DMEM/F12 (Dulbecco’s modified Eagle’s medium/Nutrient Mixture F-12) on long-term cell maintenance, whereas serum-free media K-SFM and EpiLife failed to support cell growth. HMCs differed molecularly and morphologically from their neighbor dermal papilla cells on expressions of feature genes, such as HOXC13, and on characteristic keratinocyte-like appearances versus fibroblast shapes, respectively. Higher calcium concentrations significantly stimulated the expression of the genes (e.g., KRT1 and IVL) involved in keratinocyte differentiation and, promoted cell proliferation. Moreover, 10⁻⁵ M ATRA obviously boosted goat HMC expansions and changed their cell cycle distributions compared to the controls. Our study shines a light on researches exploring the mechanisms underlying the growth of cashmere.

Monitoring calcium-induced epidermal differentiation in vitro using multiphoton microscopy

SIGNIFICANCE

Research in tissue engineering and in vitro organ formation has recently intensified. To assess tissue morphology, the method of choice today is restricted primarily to histology. Thus novel tools are required to enable noninvasive, and preferably label-free, three-dimensional imaging that is more compatible with futuristic organ-on-a-chip models.

AIM

We investigate the potential for using multiphoton microscopy (MPM) as a label-free in vitro approach to monitor calcium-induced epidermal differentiation.

APPROACH

In vitro epidermis was cultured at the air-liquid interface in varying calcium concentrations. Morphology and tissue architecture were investigated using MPM based on visualizing cellular autofluorescence.

RESULTS

Distinct morphologies corresponding to epidermal differentiation were observed. In addition, Ca2  +  -induced effects could be distinguished based on the architectural differences in stratification in the tissue cultures.

CONCLUSIONS

Our study shows that MPM based on cellular autofluorescence enables visualization of Ca2  +  -induced differentiation in epidermal skin models in vitro. The technique has potential to be further adapted as a noninvasive, label-free, and real-time tool to monitor tissue regeneration and organ formation in vitro.

Synthetic Hydroxyapatite Inhibits Bisphosphonate Toxicity to the Oral Mucosa In Vitro

Medication-related osteonecrosis of the jaw (MRONJ) is a side effect of bisphosphonate therapy, characterised by exposed necrotic bone. The soft tissues of the oral mucosa no longer provide a protective barrier and MRONJ patients experience pain, infections and difficulties eating. We hypothesised that hydroxyapatite (Ca₅(PO₄)₃(OH)) could reduce bisphosphonate concentrations and protect the oral mucosa by exploiting bisphosphonate's calcium binding affinity. The effect of zoledronic acid (ZA) and pamidronic acid (PA) on the metabolism of oral fibroblasts, oral keratinocytes and three-dimensional oral mucosa models was investigated and then repeated in the presence of hydroxyapatite granules. Without hydroxyapatite, ZA and PA significantly reduced the metabolic activity of oral cells in a dose-dependent manner. Both drugs reduced epithelial thickness and 30 µM ZA resulted in loss of the epithelium. Hydroxyapatite granules had a protective effect on oral cells, with metabolic activity retained. Oral mucosa models retained their multi-layered epithelium when treated with ZA in the presence of hydroxyapatite granules and metabolic activity was comparable to controls. These results demonstrate hydroxyapatite granules protected oral soft tissues from damage caused by bisphosphonate exposure. Porous hydroxyapatite granules are currently used for socket preservation and this data suggests their potential to prevent MRONJ in at-risk patients.

Aging-associated alterations in epidermal function and their clinical significance

Chronologically-aged skin displays multiple functional changes in both the dermis and the epidermis. It appears that epidermal dysfunction, compromised permeability homeostasis, reduced stratum corneum hydration and elevated skin surface pH predispose to the development of aging-associated cutaneous and extracutaneous disorders. Improvements in epidermal function have been shown to be an effective alternative therapy in the prevention and treatment of some aging-associated cutaneous disorders, including eczematous dermatitis, pruritus, and xerosis. Recent studies demonstrated that epidermal dysfunction leads to the development of chronic, low-grade systemic inflammation, termed ‘inflammaging,’ which is linked to the development of aging-associated systemic disorders. Thus, correction of epidermal dysfunction could comprise a novel strategy in the prevention and treatment of aging-associated systemic disorders as well. In this review, we summarize aging-associated alterations in epidermal function, their underlying mechanisms, and their clinical significance. Regimens to improve epidermal function in the elderly are also discussed.

Restoration of calcium-induced differentiation potential and tight junction formation in HaCaT keratinocytes by functional attenuation of overexpressed high mobility group box-1 protein

HaCaT cells have been widely used as undifferentiated epidermal keratinocytes, since these non-tumorigenic cells can be readily maintained in conventional medium and partly retain epidermal differentiation potential upon stimulation with high concentration of calcium. In contrast to primary epidermal keratinocytes, however, these cells never form tight junction (TJ), a specific structure in highly differentiated keratinocytes, solely by the differentiation stimulation. Here, we show that HaCaT cells secrete a considerable amount of high mobility group box-1 protein (HMGB1), one of major inflammatory mediator, which appeared to be responsible, at least in part, for such aberrant differentiation response. So far, inhibition of c-Jun N-terminal kinase (JNK) in high calcium medium has been supposed to be the only way to induce TJ formations in HaCaT cells; however, SP600125, a potent inhibitor of JNK showed cytostatic effects and clearly attenuated epidermal differentiation and stratification. In contrast, dipotassium glycyrrhizate (GK2), a soluble analogue of HMGB1-blocker Glycyrrhizin, down-regulated interferon-β, a typical inflammatory cytokine induced by secreted HMGB1, and accelerated differentiation responses to the calcium treatment in these cells. In addition, GK2-treatmenrt resulted in the formation of double cell layers in cultured HaCaT cells, where the stratified upper cells transiently accumulated TJ proteins at the cell-cell contact sites. These results highlight the importance of attenuation of secreted HMGB1-signals in cultured HaCaT cells for studies of functional keratinocytes.

In Vitro Expansion of Keratinocytes on Human Dermal Fibroblast-Derived Matrix Retains Their Stem-Like Characteristics

The long-term expansion of keratinocytes under conditions that avoid xenogeneic components (i.e. animal serum- and feeder cell-free) generally causes diminished proliferation and increased terminal differentiation. Here we present a culture system free of xenogeneic components that retains the self-renewal capacity of primary human keratinocytes. In vivo the extracellular matrix (ECM) of the tissue microenvironment has a major influence on a cell’s fate. We used ECM from human dermal fibroblasts, cultured under macromolecular crowding conditions to facilitate matrix deposition and organisation, in a xenogeneic-free keratinocyte expansion protocol. Phospholipase A₂ decellularisation produced ECM whose components resembled the core matrix composition of natural dermis by proteome analyses. Keratinocytes proliferated rapidly on these matrices, retained their small size, expressed p63, lacked keratin 10 and rarely expressed keratin 16. The colony forming efficiency of these keratinocytes was enhanced over that of keratinocytes grown on collagen I, indicating that dermal fibroblast-derived matrices maintain the in vitro expansion of keratinocytes in a stem-like state. Keratinocyte sheets formed on such matrices were multi-layered with superior strength and stability compared to the single-layered sheets formed on collagen I. Thus, keratinocytes expanded using our xenogeneic-free protocol retained a stem-like state, but when triggered by confluence and calcium concentration, they stratified to produce epidermal sheets with a potential clinical use.

Fucoidan from Undaria pinnatifida Ameliorates Epidermal Barrier Disruption via Keratinocyte Differentiation and CaSR Level Regulation

The epidermal barrier acts as a line of defense against external agents as well as helps to maintain body homeostasis. The calcium concentration gradient across the epidermal barrier is closely related to the proliferation and differentiation of keratinocytes (KCs), and the regulation of these two processes is the key to the repair of epidermal barrier disruption. In the present study, we found that fucoidan from Undaria pinnatifida (UPF) could promote the repair of epidermal barrier disruption in mice. The mechanistic study demonstrated that UPF could promote HaCaT cell differentiation under low calcium condition by up-regulating the expression of calcium-sensing receptor (CaSR), which could then lead to the activation of the Catenin/PLCγ1 pathway. Further, UPF could increase the expression of CaSR through activate the ERK and p38 pathway. These findings reveal the molecular mechanism of UPF in the repair of the epidermal barrier and provide a basis for the development of UPF into an agent for the repair of epidermal barrier repair.

Establishment of Nrf2-deficient HaCaT and immortalized primary human foreskin keratinocytes and characterization of their responses to ROS-induced cytotoxicity

Nuclear factor erythroid 2-like 2 (Nrf2) is a key transcription factor responsible for the induction of cytoprotective genes when a cell is exposed to reactive oxygen species (ROS). Insufficient ROS neutralization has been associated with undesirable changes in the skin caused by age and disease. In order to mimic the pathological conditions of these oxidative stress-induced skin disorders, we established Nrf2-deficient HaCaT and immortalized human foreskin keratinocyte (iHFK) cell lines via lentiviral transduction of Nrf2-targeting short-hairpin RNAs. Their transcriptional, as well as translational blockage of Nrf2 expression, was verified by using a proteasomal inhibitor (MG132) and well-known Nrf2 activator (α-lipoic acid (ALA)). Reduced expression of NADPH dehydrogenase quinone 1 (NQO-1) and heme oxygenase 1 (HO-1) genes, which are well-characterized downstream targets of Nrf2-mediated transactivation, was also confirmed by using ALA and another Nrf2 activator, marliolide. In general, iHFK cells displayed more enhanced cytotoxicity to menadione, a ROS-generating reference compound, than HaCaT cells. In addition, the Nrf2 deficiency highly potentiated the cytotoxic effects of menadione in both HaCaT and iHFK cells. Interestingly, pretreatment of either ALA or marliolide conferred protection against the ROS induction and the subsequent development of cytotoxicity by menadione in both HaCaT and iHFK cells regardless of the Nrf2 status. These data suggest a possibility for activation of Nrf2-independent ROS detoxification pathways by either ALA or marliolide. These newly established Nrf2-deficient HaCaT and iHFK cell lines should be useful as a highly ROS-sensitive damaged skin model for the study of age-dependent cellular changes in an in vitro setting.

Significance of Cytokeratin-1 Single-Nucleotide Polymorphism and Protein Level in Susceptibility to Vocal Leukoplakia and Laryngeal Squamous Cell Carcinoma

OBJECTIVE

To investigate the association between the cytokeratin (CK)-1 single-nucleotide polymorphism (SNP), the protein level of CK-1 and the risk of vocal leukoplakia and laryngeal squamous cell carcinoma (LSCC).

METHODS

In this case-control study, 155 patients with vocal leukoplakia, 323 patients with LSCC, and 266 healthy controls were genotyped for the CK-1 (SNP RS14024) gene using pyrosequencing. The protein expression level of CK-1 was analyzed in vocal leukoplakia, LSCC, and vocal polyp patients by immunohistochemistry (IHC).

RESULTS

Of the CK-1 RS14024 polymorphism, the heterozygote AG and homozygote GG genotype exhibited a significantly increased risk of LSCC (AG: OR = 2.16, p = 0.014; GG: OR = 2.15, p = 0.018) compared to normal controls. A higher protein expression level of CK-1 was detected in patients with LSCC compared to vocal leukoplakia and polyps (both p < 0.001), and a significant increasing trend of CK-1 protein expression level from mild-moderate dysplasia to moderate-severe dysplasia in vocal leukoplakia patients was also observed (p = 0.006).

CONCLUSIONS

This study demonstrates that the CK-1 SNP and high protein expression levels are associated with vocal leukoplakia and LSCC and promote the transformation from vocal leukoplakia to LSCC in a Chinese Han population.

Lysosome Alterations in the Human Epithelial Cell Line HaCaT and Skin Specimens: Relevance to Psoriasis

Despite the constantly updated knowledge regarding the alterations occurring in the cells of patients with psoriasis, the status and the role of the lysosome, a control center of cell metabolism, remain to be elucidated. The architecture of the epidermis is largely regulated by the action of lysosomes, possibly activating signaling pathways in the cellular crosstalk of keratinocytes-epidermal cells-with infiltrating immune cells. Thus, in the present study, lysosome alterations were examined in vitro and in situ using a two-dimensional (2D) keratinocyte model of HaCaT cells with "psoriasis-like" inflammation and skin specimens, respectively. Specific fluorescence and immunohistochemical staining showed an augmented level of acidic organelles in response to keratinocyte activation (mimicking a psoriatic condition while maintaining the membrane integrity of these structures) as compared with the control, similar to that seen in skin samples taken from patients. Interestingly, patients with the most pronounced PASI (Psoriasis Area and Severity Index), BSA (Body Surface Area), and DLQI (Dermatology Life Quality Index) scores suffered a high incidence of positive lysosomal-associated membrane protein 1 (LAMP1) expression. Moreover, it was found that the gene deregulation pattern was comparable in lesioned (PP) and non-lesioned (PN) patient-derived skin tissue, which may indicate that these alterations occur prior to the onset of the characteristic phenotype of the disease. Changes in the activity of genes encoding the microphthalmia family (MiT family) of transcription factors and mammalian target of rapamycin complex 1 (MTORC1) were also observed in the in vitro psoriasis model, indicating that the biogenesis pathway of this arm is inhibited. Interestingly, in contrast to the keratinocytes of HaCaT with "psoriasis-like" inflammation, LAMP1 was up-regulated in both PP and PN skin, which can be a potential sign of an alternative mechanism of lysosome formation. Defining the molecular profile of psoriasis in the context of "the awesome lysosome" is not only interesting, but also desired; therefore, it is believed that this paper will serve to encourage other researchers to conduct further studies on this subject.

Mammalian cell viability on hydrophobic and superhydrophobic fabrics

Surface properties like hydrophobicity and morphology of the substrate are essential for cell proliferation affecting its growth, survival and also for its communication with other cells on fabrics. The combination of low surface energy and a specific surface morphology (micro/nano-roughness) leads to significantly less wettable surfaces, known as superhydrophobic characterized by high contact angle above 150° and a very small hysteresis. Such high water repellent coatings feature small area available to be exploited in many applications where interactions with aqueous environment are strongly to be avoided. In this work, the authors have investigated the influence of coating polyester fabric at different degree of hydrophobicity by mixed organic-inorganic coating with moderated to highly water repellence. Depending on the coating composition and structure, the hydrophobicity of the fabric can be finely modulated by an easy-to-prepare method applicable to commercial, low cost fabric substrates providing advanced performance. In vitro experiments have been performed in order to establish the influence of surface modification on adhesion of representative model mammalian cell lines such as 3T3 fibroblasts, HaCaT keratinocytes and HeLa epithelial carcinoma cells. The obtained results suggested that, in addition to the chemistry and morphology of the coating, the characteristics of the substrate are important parameters on the final cell viabilities.

A three-dimensional human skin model to evaluate the inhibition of Staphylococcus aureus by antimicrobial peptide-functionalized silver carbon nanotubes

Objective

To investigate the toxicity and antibacterial application of antimicrobial peptide-functionalized silver-coated carbon nanotubes against Staphylococcus infection using a full thickness human three-dimensional skin model.

Materials and methods

The three-dimensional skin formation on the scaffolds was characterized by electron microscopy and investigation of several skin cell markers by real time–reverse transcriptase polymerase chain reaction. Functionalized silver-coated carbon nanotubes were prepared using carboxylated silver-coated carbon nanotubes with antimicrobial peptides such as TP359, TP226 and TP557. Following the characterization and toxicity evaluation, the antibacterial activity of functionalized silver-coated carbon nanotubes against Staphylococcus aureus was investigated using a bacterial enumeration assay and scanning electron microscopy. For this purpose, a scar on the human three-dimensional skin grown on Alvetex scaffold using keratinocytes and fibroblasts cells was created by taking precaution not to break the scaffold beneath, followed by incubation with 5 µg/mL of functionalized silver-coated carbon nanotubes re-suspended in minimum essential medium for 2 h. Post 2-h incubation, 200 µL of minimum essential medium containing 1 × 104 colony forming units of Staphylococcus aureus were incubated for 2 h. After incubation with bacteria, the colony forming unit/gram (cfu/g) of skin tissue were counted using the plate count assay and the samples were processed for scanning electron microscopy analysis.

Results

MTT assay revealed no toxicity of functionalized silver-coated carbon nanotubes to the skin cells such as keratinocytes and fibroblasts at 5 µg/mL with 98% cell viability. The bacterial count increased from 104 to 108 cfu/g in the non-treated skin model, whereas skin treated with functionalized silver-coated carbon nanotubes showed only a small increase from 104 to 105 cfu/g (1000-fold viable cfu difference). Scanning electron microscopy analysis showed the presence of Staphylococcus aureus on the non-treated skin as opposed to the treated skin.

Conclusion

Thus, our results showed that functionalized silver-coated carbon nanotubes are not only non-toxic, but also help reduce the infection due to their antibacterial activity. These findings will aid in the development of novel antibacterial skin substitutes.

Keratinocyte differentiation induces APOBEC3A, 3B, and mitochondrial DNA hypermutation

Mitochondrial DNA (mtDNA) mutations are found in many types of cancers and suspected to be involved in carcinogenesis, although the mechanism has not been elucidated. In this study, we report that consecutive C-to-T mutations (hypermutations), a unique feature of mutations induced by APOBECs, are found in mtDNA from cervical dysplasia and oropharyngeal cancers. In vitro, we found that APOBEC3A (A3A) and 3B (A3B) expression, as well as mtDNA hypermutation, were induced in a cervical dysplastic cell line W12 when cultured in a differentiating condition. The ectopic expression of A3A or A3B was sufficient to hypermutate mtDNA. Fractionation of W12 cell lysates and immunocytochemical analysis revealed that A3A and A3B could be contained in mitochondrion. These results suggest that mtDNA hypermutation is induced upon keratinocyte differentiation, and shed light on its molecular mechanism, which involves A3s. The possible involvement of mtDNA hypermutations in carcinogenesis is also discussed.

Neurotensin, substance P, and insulin enhance cell migration

Neurotensin, substance P, and insulin have been demonstrated to improve wound healing in vivo. However, the mechanism behind their effect is still not fully understood. This study investigates the effects leading to enhanced scratch closure by these peptides in vitro. The skin keratinocyte cell line, HaCaT, was used to test scratch closure effects of the peptides and alterations of cytokine levels. HUVEC cells were used to test the angiogenic effect of the peptides. Furthermore, clinical isolates of Staphylococcus lugdunensis were used to examine the potential antimicrobial activity of each peptide. Our results demonstrate that neurotensin, substance P, and insulin had significant migratory effects in scratch assays were neurotensin had the lowest effect. Furthermore, we investigated use of the peptides in combination. When substance P was used in combination with neurotensin, the cell migratory capacity was decreased, and the peptides showed a negative correlation (r = -0.298, P < .001). Neurotensin and insulin significantly increased levels of monocyte chemoattractant protein-1 (P < .001) secreted from white blood cells, whereas substance P showed a tendency. Interestingly, neurotensin increased the level of monocyte chemoattractant protein-1 significantly compared to substance P (P < .01). Additionally, the peptides decreased TNFα mRNA levels (P < .001) in HaCaT cells, whereas only neurotensin and insulin decreased IL-8 mRNA (P < .001) but had no significant effect on IL-6 mRNA levels. Surprisingly, substance P increased IL-6 mRNA 9-fold (P < .001). Furthermore, we demonstrate that the peptides increased angiogenesis in the HUVEC cells (P < .001). Finally, S. lugdunensis isolates were not susceptible to the peptides. We demonstrate that the peptides worked differently on HaCaT cells, but substance P acted differently than neurotensin on cytokine levels expression as well as on migration of HaCaT cells. On the contrary, neurotensin and insulin worked similarly. All of these aspects are crucial for proper wound healing, and the results suggest multiple mechanisms for wound-healing properties of these peptides.

Inhibitory effects of TGP on KGF‑induced hyperproliferation of HaCaT cells via suppression of the p38 MAPK/NF‑κB p65 pathway

Psoriasis is a chronic inflammatory skin disease, primarily caused by overgrowth and abnormal differentiation of epidermal keratinocytes. Studies have suggested that keratinocyte growth factor (KGF) may be involved in the regulation of differentiation and development of keratinocytes. Total glucosides of peony (TGP) have been widely used for the treatment of psoriasis. The present study aimed to determine whether the therapeutic effect of TGP on psoriasis is mediated by modulation of the p38 mitogen‑activated protein kinase (p38 MAPK)/nuclear factor (NF)‑κB p65 signaling pathways. Cell proliferation was evaluated by CCK‑8 and cell cycle was assessed by flow cytometry assay. Protein and mRNA expression of genes were determined by western blot and reverse transcription‑quantitative polymerase chain reaction, respectively. The results of the present study demonstrated that KGF can promote proliferation of HaCaT cells in a dose‑dependent manner. In addition, it was demonstrated that TGP may suppress the hyperproliferation of HaCaT cells stimulated by KGF by inducing arrest of the cell cycle at the G1 phase. The expression levels of the proinflammatory cytokines interleukin (IL)‑22 and vascular endothelial growth factor (VEGF) were markedly elevated in cells treated with KGF, whereas they were downregulated in cells treated with TGP. Furthermore, combination treatments with p38 MAPK inhibitor SB203580 and KGF, or TGP and KGF suppressed the mRNA and protein expression levels of IL‑22 and VEGF, compared with cells treated with KGF alone. Furthermore, the expression profiles of phosphorylated‑p38 MAPK and NF‑κB p65 were similar to those of IL‑22 and VEGF. The results of the present study suggested that the therapeutic effect of TGP on psoriasis may be mediated by modulation of the p38 MAPK/NF‑κB p65 signaling pathway. The results of the present study contribute to the understanding of the role of TGP in the treatment of psoriasis. The present study provides insights suggesting that p38 MAPK may be a novel regulatory signaling pathway for the treatment of psoriasis.

Respective optimal calcium concentrations for proliferation on type I collagen fibrils in two keratinocyte line cells, HaCaT and FEPE1L-8

Keratinocyte line cells HaCaT and FEPE1L-8 are used for skin model with type I collagen fibrils (gels). For this purpose, not only differentiation but also regulation of proliferation on type I collagen gels by exogenous calcium concentration is important. When exogenous calcium concentration is low, primary keratinocyte proliferation is repressed and eventually cells are induced to apoptosis on type I collagen gels. The apoptosis induced on type I collagen gels is suppressed by increasing calcium concentration in the medium. That is, higher exogenous calcium concentration is necessary for primary keratinocyte survival on type I collagen gels than for that on dish surface culture. Meanwhile much higher exogenous calcium causes cell differentiation and inhibition of proliferation. The optimal calcium concentrations for proliferation on type I collagen gels have not been clarified in keratinocyte line cells. HaCaT cells have a unique calcium sensitivity in comparison with primary keratinocytes, whereas FEPE1L-8 cells have a similar sensitivity to primary keratinocytes. In this study, we compared the effect of calcium concentrations on proliferation of HaCaT and FEPE1L-8 cells on type I collagen gels. On type I collagen gels, both line cells required higher calcium concentrations for proliferation than on dish surface. HaCaT cells proliferated better in a wider range of calcium concentrations than FEPE1L-8 cells.