Cortical brain organoid slices (cBOS) for the study of human neural cells in minimal networks.

Brain organoids derived from human pluripotent stem cells are a promising tool for studying human neurodevelopment and related disorders. Here, we generated long-term cultures of cortical brain organoid slices (cBOS) grown at the air-liquid interphase from regionalized cortical organoids. We show that cBOS host mature neurons and astrocytes organized in complex architecture. Whole-cell patch-clamp demonstrated subthreshold synaptic inputs and action potential firing of neurons. Spontaneous intracellular calcium signals turned into synchronous large-scale oscillations upon combined disinhibition of NMDA receptors and blocking of GABAA receptors. Brief metabolic inhibition to mimic transient energy restriction in the ischemic brain induced reversible intracellular calcium loading of cBOS. Moreover, metabolic inhibition induced a reversible decline in neuronal ATP as revealed by ATeam1.03YEMK. Overall, cBOS provide a powerful platform to assess morphological and functional aspects of human neural cells in intact minimal networks and to address the pathways that drive cellular damage during brain ischemia.

Balancing neuronal activity to fight neurodevelopmental disorders.

In a recent study, Rylaarsdam and colleagues revealed that mutant PACS1 gene, which causes a rare neurodevelopmental syndrome, affects the firing ability of human neurons without dysregulating the cellular architecture of brain organoids. These findings suggest aberrant neuronal electrophysiology as a possible interventional target for pediatric diseases impairing brain development.

Localized calcium oxalate crystals in primary cutaneous aspergillosis.

Select Aspergillus species can produce oxalate as a fermentation byproduct, which may react with calcium ions to produce insoluble calcium oxalate crystals in tissues. These crystals are frequently associated with pulmonary Aspergillus infections, yet are rarely described in primary cutaneous aspergillosis. Herein, we report the presence of calcium oxalate crystals detected on cutaneous specimens from primary cutaneous Aspergillus niger and Aspergillus fumigatus infections in an immunocompromised, premature infant. No metabolic sources of oxalosis were found.

Rituximab and Omalizumab Combination Therapy for Bullous Pemphigoid.

This research letter reports on a case series of 10 patients with bullous pemphigoid treated with rituximab combined with omalizumab.

Subventricular zone cytogenesis provides trophic support for neural repair in a mouse model of stroke.

Stroke enhances proliferation of neural precursor cells within the subventricular zone (SVZ) and induces ectopic migration of newborn cells towards the site of injury. Here, we characterize the identity of cells arising from the SVZ after stroke and uncover a mechanism through which they facilitate neural repair and functional recovery. With genetic lineage tracing, we show that SVZ-derived cells that migrate towards cortical photothrombotic stroke in mice are predominantly undifferentiated precursors. We find that ablation of neural precursor cells or conditional knockout of VEGF impairs neuronal and vascular reparative responses and worsens recovery. Replacement of VEGF is sufficient to induce neural repair and recovery. We also provide evidence that CXCL12 from peri-infarct vasculature signals to CXCR4-expressing cells arising from the SVZ to direct their ectopic migration. These results support a model in which vasculature surrounding the site of injury attracts cells from the SVZ, and these cells subsequently provide trophic support that drives neural repair and recovery.

Development of a Skin-Directed Scoring System for Stevens-Johnson Syndrome and Epidermal Necrolysis: A Delphi Consensus Exercise.

Importance: Scoring systems for Stevens-Johnson syndrome and epidermal necrolysis (EN) only estimate patient prognosis and are weighted toward comorbidities and systemic features; morphologic terminology for EN lesions is inconsistent. Objectives: To establish consensus among expert dermatologists on EN terminology, morphologic progression, and most-affected sites, and to build a framework for developing a skin-directed scoring system for EN. Evidence Review: A Delphi consensus using the RAND/UCLA appropriateness criteria was initiated with a core group from the Society of Dermatology Hospitalists to establish agreement on the optimal design for an EN cutaneous scoring instrument, terminology, morphologic traits, and sites of involvement. Findings: In round 1, the 54 participating dermatology hospitalists reached consensus on all 49 statements (30 appropriate, 3 inappropriate, 16 uncertain). In round 2, they agreed on another 15 statements (8 appropriate, 7 uncertain). There was consistent agreement on the need for a skin-specific instrument; on the most-often affected skin sites (head and neck, chest, upper back, ocular mucosa, oral mucosa); and that blanching erythema, dusky erythema, targetoid erythema, vesicles/bullae, desquamation, and erosions comprise the morphologic traits of EN and can be consistently differentiated. Conclusions and Relevance: This consensus exercise confirmed the need for an EN skin-directed scoring system, nomenclature, and differentiation of specific morphologic traits, and identified the sites most affected. It also established a baseline consensus for a standardized EN instrument with consistent terminology.

Cell-Specific and Variant-Linked Alterations in Expression of ERAP1, ERAP2, and LNPEP Aminopeptidases in Psoriasis.

ERAP1, ERAP2, and LNPEP are aminopeptidases implicated in autoimmune pathophysiology. In this study, we show that ERAP2 is upregulated and ERAP1 is downregulated in patients with psoriasis who are homozygous for autoimmune-linked variants of ERAP. We also demonstrate that aminopeptidase expression is not uniform in the skin. Specifically, the intracellular antigen-processing aminopeptidases ERAP1 and ERAP2 are strongly expressed in basal and early spinous layer keratinocytes, whereas granular layer keratinocytes expressed predominantly LNPEP, an aminopeptidase specialized in the processing of extracellular antigens for presentation to T cells. In psoriasis, basal keratinocytes also expressed the T-cell- and monocyte-attracting chemokine, CCL2, and the T-cell-supporting cytokine, IL-15. In contrast, TGF-ß1 was the major cytokine expressed by healthy control basal keratinocytes. SFRP2-high dermal fibroblasts were also noted to have an ERAP2-high expression phenotype and elevated HLA-C. In psoriasis, the SFRP2-high fibroblast subpopulation also expressed elevated CXCL14. From these results, we postulate that (i) an increased ERAP2/ERAP1 ratio results in altered antigen processing, a potential mechanism by which ERAP risk alleles predispose individuals to autoimmunity; (ii) ERAP2-high expressing cells display a unique major histocompatibility complex-bound peptidome generated from intracellular antigens; and (iii) the granular layer peptidome is skewed toward extracellular antigens.

A review of topical probiotic therapy for atopic dermatitis.

Atopic dermatitis (AD) is a common, chronic skin disorder that is associated with dysbiosis of the skin microbiome along with an impaired skin barrier and abnormal immune signalling. Particularly, AD has been associated with increased abundance of Staphylococcus aureus and decreased overall bacterial diversity. Topical probiotic formulations are garnering further interest in the treatment of AD and may be derived from commensal bacteria found on healthy epithelium or from exogenous bacteria. Strains chosen for clinical trials have often demonstrated antimicrobial actions to S. aureus in vitro. Multiple randomized clinical trials with topical probiotics have resulted in significant improvements in clinical severity, decreased abundance of S. aureus in treated lesional skin and increased bacterial diversity. Side-effects from available studies have been minimal apart from one patient who developed a furuncle in the treatment area. Topical probiotics have been shown to be safe and potentially efficacious in AD; however, further research including larger, longer-term clinical trials need to be performed before topical probiotics should be recommended to patients.

Identifying a novel role for the master regulator Tal1 in the Endothelial to Hematopoietic Transition.

Progress in the generation of Hematopoietic Stem and Progenitor Cells (HSPCs) in vitro and ex vivo has been built on the knowledge of developmental hematopoiesis, underscoring the importance of understanding this process. HSPCs emerge within the embryonic vasculature through an Endothelial-to-Hematopoietic Transition (EHT). The transcriptional regulator Tal1 exerts essential functions in the earliest stages of blood development, but is considered dispensable for the EHT. Nevertheless, Tal1 is expressed with its binding partner Lmo2 and it homologous Lyl1 in endothelial and transitioning cells at the time of EHT. Here, we investigated the function of these genes using a mouse embryonic-stem cell (mESC)-based differentiation system to model hematopoietic development. We showed for the first time that the expression of TAL1 in endothelial cells is crucial to ensure the efficiency of the EHT process and a sustained hematopoietic output. Our findings uncover an important function of Tal1 during the EHT, thus filling the current gap in the knowledge of the role of this master gene throughout the whole process of hematopoietic development.

Proprotein convertase subtilisin/kexin type 9 is a psoriasis-susceptibility locus that is negatively related to IL36G.

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a posttranslational regulator of the LDL receptor (LDLR). Recent studies have proposed a role for PCSK9 in regulating immune responses. Using RNA-Seq-based variant discovery, we identified a possible psoriasis-susceptibility locus at 1p32.3, located within PCSK9 (rs662145 C > T). This finding was verified in independently acquired genomic and RNA-Seq data sets. Single-cell RNA-Seq (scRNA-Seq) identified keratinocytes as the primary source of PCSK9 in human skin. PCSK9 expression, however, was not uniform across keratinocyte subpopulations. scRNA-Seq and IHC demonstrated an epidermal gradient of PCSK9, with expression being highest in basal and early spinous layer keratinocytes and lowest in granular layer keratinocytes. IL36G expression followed the opposite pattern, with expression highest in granular layer keratinocytes. PCSK9 siRNA knockdown experiments confirmed this inverse relationship between PCSK9 and IL36G expression. Other immune genes were also linked to PCSK9 expression, including IL27RA, IL1RL1, ISG20, and STX3. In both cultured keratinocytes and nonlesional human skin, homozygosity for PCSK9 SNP rs662145 C > T was associated with lower PCSK9 expression and higher IL36G expression, when compared with heterozygous skin or cell lines. Together, these results support PCSK9 as a psoriasis-susceptibility locus and establish a putative link between PCSK9 and inflammatory cytokine expression.

Biogeographic and disease-specific alterations in epidermal lipid composition and single-cell analysis of acral keratinocytes.

The epidermis is the outermost layer of skin. Here, we used targeted lipid profiling to characterize the biogeographic alterations of human epidermal lipids across 12 anatomically distinct body sites, and we used single-cell RNA-Seq to compare keratinocyte gene expression at acral and nonacral sites. We demonstrate that acral skin has low expression of EOS acyl-ceramides and the genes involved in their synthesis, as well as low expression of genes involved in filaggrin and keratin citrullination (PADI1 and PADI3) and corneodesmosome degradation, changes that are consistent with increased corneocyte retention. Several overarching principles governing epidermal lipid expression were also noted. For example, there was a strong negative correlation between the expression of 18-carbon and 22-carbon sphingoid base ceramides. Disease-specific alterations in epidermal lipid gene expression and their corresponding alterations to the epidermal lipidome were characterized. Lipid biomarkers with diagnostic utility for inflammatory and precancerous conditions were identified, and a 2-analyte diagnostic model of psoriasis was constructed using a step-forward algorithm. Finally, gene coexpression analysis revealed a strong connection between lipid and immune gene expression. This work highlights (a) mechanisms by which the epidermis is uniquely adapted for the specific environmental insults encountered at different body surfaces and (b) how inflammation-associated alterations in gene expression affect the epidermal lipidome.

Real-world utilization of Delphi consensus diagnostic criteria for suspected pyoderma gangrenosum.

We found that the systematic use of Delphi consensus diagnostic criteria resulted in substantial changes in management patterns in cases of suspected pyoderma gangrenosum (PG), including a reduction in systemic corticosteroid use, and significantly improved clinical outcomes. This improvement may have resulted from a combination of reduced misdiagnosis, optimized management and reduced iatrogenic harm. Increased utilization of validated diagnostic criteria for PG could optimize provider heuristics, increase diagnostic accuracy, and optimize management and clinical outcomes.