Leah A. Vardy

Background: Melasma treatment remains challenging with variable response to conventional lightening agents. Polyamine inhibition via ornithine decarboxylase 1 (ODC1) may offer an alternative approach, with eflornithine hydrochloride being an established ODC1 inhibitor. Objectives: To compare the efficacy and safety of eflornithine hydrochloride 13% cream versus standard hydroquinone 2% cream for melasma treatment. Methods: A randomized, double‐blinded, split‐face–controlled pilot trial was conducted over 3 months with 20 patients (16 female, mean age 54). Efficacy was assessed via modified Melasma Area and Severity Index (mMASI), Mexameter measurements, physician assessments, and patient satisfaction scores. Results: Both treatment groups showed improvements in mMASI scores and Mexameter measurements (erythema and melanin). No significant differences were found between treatment groups when comparing unit differences or fold changes. Only one patient reported mild irritation from eflornithine. Patient self‐assessments trended higher for eflornithine without reaching statistical significance. Conclusion: Eflornithine hydrochloride 13% cream demonstrates comparable efficacy to hydroquinone 2% cream with a favorable safety profile, presenting a promising alternative for melasma treatment. Trial Registration: ClinicalTrials.gov identifier: NCT06957834

Background: Arginase 1 (ARG1) is an enzyme expressed by keratinocytes that drives several functions linked to skin barrier function. However, the mechanisms underpinning keratinocyte ARG1 function in barrier homeostasis have not been fully elucidated. Atopic dermatitis (AD) is linked to impaired skin barrier via altered keratinocyte differentiation and susceptibility to infection. Objectives: To investigate the role of ARG1 in keratinocyte differentiation and antimicrobial responses. Methods: In vitro two-dimensional differentiation assays using ARG knockdown or ARG inhibited keratinocytes were used to explore the function of ARG1 in keratinocyte differentiation and barrier formation. ARG1 was also assessed in an ex vivo model of AD. Results: ARG1 was strongly expressed in the apical layers of human skin, corresponding to high ARG1 expression in late differentiated ­keratinocytes. ARG was downregulated in an ex vivo AD model relative to control, suggesting that altered ARG1 is clinically relevant. ARG1 ­inhibition in keratinocytes led to a significant decrease in the late differentiation markers filaggrin, involucrin and loricrin, and significant downregulation of antimicrobial peptides (AMPs), lipocalin 2, kallikreins and small proline-rich proteins. ARG forms part of the urea cycle and the action of ARG on L-arginine causes the production of L-ornithine and urea. In turn, L-ornithine is catabolized for putrescine production. Supplementation with ARG products, putrescine and urea could rescue late keratinocyte differentiation and AMP expression in ARG-deficient cells. Conclusions: ARG1 activity plays a major role in keratinocyte differentiation and AMP production. ARG1 is downregulated in an AD model, and in cell systems its function can be rescued by the ARG1 downstream products putrescine and urea. Manipulation of the ARG1 pathway may have the potential to be used for the management of skin conditions such as AD.

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Current methods for determining RNA structure with short-read sequencing cannot capture most differences between distinct transcript isoforms. Here we present RNA structure analysis using nanopore sequencing (PORE-cupine), which combines structure probing using chemical modifications with direct long-read RNA sequencing and machine learning to detect secondary structures in cellular RNAs. PORE-cupine also captures global structural features, such as RNA-binding-protein binding sites and reactivity differences at single-nucleotide variants. We show that shared sequences in different transcript isoforms of the same gene can fold into different structures, highlighting the importance of long-read sequencing for obtaining phase information. We also demonstrate that structural differences between transcript isoforms of the same gene lead to differences in translation efficiency. By revealing isoform-specific RNA structure, PORE-cupine will deepen understanding of the role of structures in controlling gene regulation.

The study of skin pigmentation requires determining the rate of melanin production in melanocytes and quantifying the rate of melanosome transfer to keratinocytes. Here, we describe a method to quantify melanosome transfer using immunofluorescence microscopy coupled with automated image analysis of in vitro human melanocytes and keratinocytes in co-culture. In this method, the number of melanin capped keratinocyte nuclei is quantified.