Plucked hair follicles from patients with chronic discoid lupus erythematosus show a disease-specific molecular signature

Emerging concepts of type I interferons in SLE pathogenesis and therapy

Type I interferons have been suspected for decades to have a crucial role in the pathogenesis of systemic lupus erythematosus (SLE). Evidence has now overturned several long-held assumptions about how type I interferons are regulated and cause pathological conditions, providing a new view of SLE pathogenesis that resolves longstanding clinical dilemmas. This evidence includes data on interferons in relation to genetic predisposition and epigenetic regulation. Importantly, data are now available on the role of interferons in the early phases of the disease and the importance of non-haematopoietic cellular sources of type I interferons, such as keratinocytes, renal tubular cells, glial cells and synovial stromal cells, as well as local responses to type I interferons within these tissues. These local effects are found not only in inflamed target organs in established SLE, but also in histologically normal skin during asymptomatic preclinical phases, suggesting a role in disease initiation. In terms of clinical application, evidence relating to biomarkers to characterize the type I interferon system is complex, and, notably, interferon-blocking therapies are now licensed for the treatment of SLE. Collectively, the available data enable us to propose a model of disease pathogenesis that invokes the unique value of interferon-targeted therapies. Accordingly, future approaches in SLE involving disease reclassification and preventative strategies in preclinical phases should be investigated.

The Genetic Landscape of Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune connective tissue disease that can exist as a disease entity or within the context of systemic lupus erythematosus (SLE). Over the years, efforts to elucidate the genetic underpinnings of CLE and SLE have yielded a wealth of information. This review examines prior studies investigating the genetics of CLE at the DNA and RNA level and identifies future research areas. In this literature review, we examined the English language literature captured within the MEDLINE and Embase databases using pre-defined search terms. First, we surveyed studies investigating various DNA studies of CLE. We identified three predominant areas of focus in HLA profiling, complement deficiencies, and genetic polymorphisms. An increased frequency of HLA-B8 has been strongly linked to CLE. In addition, multiple genes responsible for mediating innate immune response, cell growth, apoptosis, and interferon response confer a higher risk of developing CLE, specifically TREX1 and SAMHD1. There was a strong association between C2 complement deficiency and CLE. Second, we reviewed literature studying aberrations in the transcriptomes of patients with CLE. We reviewed genetic aberrations initiated by environmental insults, and we examined the interplay of dysregulated inflammatory, apoptotic, and fibrotic pathways in the context of the pathomechanism of CLE. These current learnings will serve as the foundation for further advances in integrating personalized medicine into the care of patients with CLE.

Applying Early Intervention Strategies to Autoimmune Skin Diseases. Is the Window of Opportunity Preclinical? A Dermato-Rheumatology Perspective

Many inflammatory skin diseases exhibit a chronic course with unsatisfactory long-term outcomes. Insights into early intervention approaches in other autoimmune contexts could improve the trajectory of lifelong diseases in terms of sustained remission or minimal disease activity, reduced requirement for therapy and medical resource use, and improved QoL. In both rheumatoid arthritis (RA) and psoriatic arthritis (PsA), we have learned that the timing and intensity of early interventions can influence later outcomes. Investigation into early RA, PsA, and systemic lupus erythematosus has shown that the optimal window of opportunity may even extend into asymptomatic preclinical phases of diseases. Notably, early and preclinical diseases may have pathogenic mechanisms and therapeutic targets that differ from those of the established disease. In this paper, we review the literature on these insights and discuss how similar research and therapeutic strategies may be investigated in cutaneous autoimmunity. We highlight the contribution of skin-resident cells to diseases that were previously thought to be initiated in the primary and secondary lymphoid organs of the immune system. We focus on two dermato‒rheumatology conditions-lupus and psoriasis-which share the commonality that effective early cutaneous disease therapy may have far-reaching implications on abrogating potentially severe systemic disease.

E-Cadherin Expression and Blunted Interferon Response in Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive neoplasm derived from plasmacytoid dendritic cells (pDCs). In this study, we investigated by immunohistochemical analysis the expression of E-cadherin (EC) on pDCs in reactive lymph nodes and tonsils, bone marrow, and in BPDCN. We compared the expression of EC in BPDCN to that in leukemia cutis (LC) and cutaneous lupus erythematosus (CLE), the latter typically featuring pDC activation. In BPDCN, we also assessed the immunomodulatory activity of malignant pDCs through the expression of several type I interferon (IFN-I) signaling effectors and downstream targets, PD-L1/CD274, and determined the extent of tumor infiltration by CD8-expressing T cells. In reactive lymph nodes and tonsils, pDCs expressed EC, whereas no reactivity was observed in bone marrow pDCs. BPDCN showed EC expression in the malignant pDCs in the vast majority of cutaneous (31/33 cases, 94%), nodal, and spleen localizations (3/3 cases, 100%), whereas it was more variable in the bone marrow (5/13, 38,5%), where tumor cells expressed EC similarly to the skin counterpart in 4 cases and differently in other 4. Notably, EC was undetectable in LC (n=30) and in juxta-epidermal pDCs in CLE (n=31). Contrary to CLE showing robust expression of IFN-I-induced proteins MX1 and ISG5 in 20/23 cases (87%), and STAT1 phosphorylation, BPDCN biopsies showed inconsistent levels of these proteins in most cases (85%). Expression of IFN-I-induced genes, IFI27, IFIT1, ISG15, RSAD2, and SIGLEC1, was also significantly (P<0.05) lower in BPDCN as compared with CLE. In BPDCN, a significantly blunted IFN-I response correlated with a poor CD8+T-cell infiltration and the lack of PD-L1/CD274 expression by the tumor cells. This study identifies EC as a novel pDC marker of diagnostic relevance in BPDCN. The results propose a scenario whereby malignant pDCs through EC-driven signaling promote the blunting of IFN-I signaling and, thereby, the establishment of a poorly immunogenic tumor microenvironment.

NKG2D and its ligands as cytotoxic factors in cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune skin disorder that is characterized by an anti-epidermal lymphocytic infiltrate invading the dermo-epidermal junction, causing an interface dermatitis (ID). Pathogenesis of CLE has been linked to activation of innate immunity. NKG2D is an innate immune receptor on NK cells and distinct T-cell populations. The NKG2D ligands MHC class I polypeptide-related sequence A and B (MICA, MICB) have been associated to CLE susceptibility. Our gene microarray analyses of chronic discoid lupus erythematosus (CDLE) skin lesions, separated in epidermal, junctional and dermal skin areas via laser microdissection, revealed a high expression of NKG2D in the lymphocytic infiltrate and led us to further investigate the role of NKG2D in CLE. Pathway analyses showed a strong "interferon (IFN) signature" and vast activation of innate immune response pathways (TLR, RIG-I, cytosolic DNA sensing, JAK/STAT) in CDLE, that expressed the high NKG2D signal. Immunohistochemistry (IHC) confirmed the presence of NKG2D and its ligand MICB in CDLE and subacute cutaneous lupus erythematosus (SCLE) lesions. Finally, HaCaT cells were stimulated with nucleic acids and extracted RNA was sequenced with Illumina HiSeq and showed that stressed keratinocytes express typical NKG2D ligands MICA/B and ULBP2. This study provides first evidence that NKG2D is present in CDLE and SCLE skin lesions and could be relevant for cytotoxicity in IFN-driven skin lesions with upregulated innate immune response pathways present in CLE. It could furthermore play a role in CLE inflammation promoted by keratinocytes under cell stress.

RNA tape sampling in cutaneous lupus erythematosus discriminates affected from unaffected and healthy volunteer skin

Objective

Punch biopsy, a standard diagnostic procedure for patients with cutaneous lupus erythematosus (CLE) carries an infection risk, is invasive, uncomfortable and potentially scarring, and impedes patient recruitment in clinical trials. Non-invasive tape sampling is an alternative that could enable serial evaluation of specific lesions. This cross-sectional pilot research study evaluated the use of a non-invasive adhesive tape device to collect messenger RNA (mRNA) from the skin surface of participants with CLE and healthy volunteers (HVs) and investigated its feasibility to detect biologically meaningful differences between samples collected from participants with CLE and samples from HVs.

Methods

Affected and unaffected skin tape samples and simultaneous punch biopsies were collected from 10 participants with CLE. Unaffected skin tape and punch biopsies were collected from 10 HVs. Paired samples were tested using quantitative PCR for a candidate immune gene panel and semi-quantitative immunohistochemistry for hallmark CLE proteins.

Results

mRNA collected using the tape device was of sufficient quality for amplification of 94 candidate immune genes. Among these, we found an interferon (IFN)-dominant gene cluster that differentiated CLE-affected from HV (23-fold change; p<0.001) and CLE-unaffected skin (sevenfold change; p=0.002), respectively. We found a CLE-associated gene cluster that differentiated CLE-affected from HV (fourfold change; p=0.005) and CLE-unaffected skin (fourfold change; p=0.012), respectively. Spearman’s correlation between per cent area myxovirus 1 protein immunoreactivity and IFN-dominant mRNA gene cluster expression was highly significant (dermis, rho=0.86, p<0.001). In total, skin tape-derived RNA expression comprising both IFN-dominant and CLE-associated gene clusters correlated with per cent area immunoreactivity of some hallmark CLE-associated proteins in punch biopsies from the same lesions.

Conclusions

A non-invasive tape RNA collection technique is a potential tool for repeated skin biomarker measures throughout a clinical trial.

A novel TRAF3IP2 variant causing familial scarring alopecia with mixed features of discoid lupus erythematosus and folliculitis decalvans

Discoid lupus erythematosus (DLE) is an autoimmune disorder with a poorly defined etiology. Despite epidemiologic gender and ethnic biases, a clear genetic basis for DLE remains elusive. In this study, we used exome and RNA sequencing technologies to characterize a consanguineous Lebanese family with four affected individuals who presented with classical scalp DLE and generalized folliculitis. Our results unraveled a novel biallelic variant c.1313C > A leading to a missense substitution p.(Thr438Asn) in TRAF3IP2(NM_147200.3). Expression studies in cultured cells revealed mis-localization of the mutated protein. Functional characterization of the mutated protein showed significant reduction in the physical interaction with the interleukin 17-A receptor (IL17RA), while interaction with TRAF6 was unaffected. By conducting a differential genome-wide transcriptomics analysis between affected and non-affected individuals, we showed that the hair follicle differentiation pathway is drastically suppressed, whereas cytokine and inflammation responses are significantly upregulated. Furthermore, our results were highly concordant with molecular signatures in patients with DLE from a public dataset. In conclusion, this is the first report on a new putative role for TRAF3IP2 in the etiology of DLE. The identified molecular features associated with this gene could pave the way for better DLE-targeted treatment.

The pathogenesis of systemic lupus erythematosus: Harnessing big data to understand the molecular basis of lupus

Systemic lupus erythematosus (SLE) is a chronic, systemic autoimmune disease that causes damage to multiple organ systems. Despite decades of research and available murine models that capture some aspects of the human disease, new treatments for SLE lag behind other autoimmune diseases such as Rheumatoid Arthritis and Crohn's disease. Big data genomic assays have transformed our understanding of SLE by providing important insights into the molecular heterogeneity of this multigenic disease. Gene wide association studies have demonstrated more than 100 risk loci, supporting a model of multiple genetic hits increasing SLE risk in a non-linear fashion, and providing evidence of ancestral diversity in susceptibility loci. Epigenetic studies to determine the role of methylation, acetylation and non-coding RNAs have provided new understanding of the modulation of gene expression in SLE patients and identified new drug targets and biomarkers for SLE. Gene expression profiling has led to a greater understanding of the role of myeloid cells in the pathogenesis of SLE, confirmed roles for T and B cells in SLE, promoted clinical trials based on the prominent interferon signature found in SLE patients, and identified candidate biomarkers and cellular signatures to further drug development and drug repurposing. Gene expression studies are advancing our understanding of the underlying molecular heterogeneity in SLE and providing hope that patient stratification will expedite new therapies based on personal molecular signatures. Although big data analyses present unique interpretation challenges, both computationally and biologically, advances in machine learning applications may facilitate the ability to predict changes in SLE disease activity and optimize therapeutic strategies.

Non-invasive Approaches for the Diagnosis of Autoimmune/Autoinflammatory Skin Diseases-A Focus on Psoriasis and Lupus erythematosus

The traditional diagnostic gold standard for inflammatory skin lesions of unclear etiology is dermato-histopathology. As this approach requires an invasive skin biopsy, biopsy processing and analysis by specialized histologists, it is a resource intensive approach requiring trained healthcare professionals. In many health care settings access to this diagnostic approach can be difficult and outside emergency cases will usually take several weeks. This scenario leads to delayed or inappropriate treatment given to patients. With dramatically increased sensitivity of a range of analysis systems including mass spectrometry, high sensitivity, multiplex ELISA based systems and PCR approaches we are now able to "measure" samples with unprecedented sensitivity and accuracy. Other important developments include the long-term monitoring of parameters using microneedle approaches and the improvement in imaging systems such as optical coherence tomography. In this review we will focus on recent achievements regarding measurements from non-invasive sampling, in particular from plucked hair and skin tape-strips which seem well suited for the diagnosis of lupus erythematosus and psoriatic inflammation, respectively. While these approaches will not replace clinical observation-they can contribute to improved subgroup diagnosis, stratified therapeutic approaches and have great potential for providing molecular and mechanistic insight in to inflammatory skin diseases.