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Plucked hair follicles from patients with Chronic Discoid Lupus Erythematosus (CDLE) display a disease-specific genomic molecular signature

Both psoriasis and cutaneous lupus erythematosus (CLE) are chronic immunological inflammatory conditions that affect both skin and joints and are well recognised to significantly impact the quality of life of patients. Although clinical symptoms of both conditions are similar, lupus can have more serious complications. Early diagnosis and treatments are crucial in managing the disease and preventing more severe clinical symptoms such as scarring, irreversible hair loss or organ failure.

Currently, when faced with clinical symptoms of scarring alopecia in patients suffering from inflammatory disorders, the standard diagnostic pathway involves a scalp biopsy followed by histopathological and immunohistological assessment. These assessments are invasive, time-consuming and expensive, requiring a specialist set up of trained clinical staff and equipment.

In this report, the authors aimed to determine if plucked hair follicles (HFs), containing living epithelial cells, from lupus and psoriatic patients can offer a non-invasive approach to diagnosing inflammatory scalp lesions.

HFs from patients previously diagnosed with chronic discoid lupus erythematosus (both lesional and non-lesional areas of the scalp), psoriasis and healthy controls were plucked. 4-5 anagen hairs from each patient containing visible hair bulbs were mechanically extracted and immediately immersed in OCT solution. Good quality RNA was successfully extracted from frozen OCT sections and samples were subjected to genomic analysis to establish whether a specific gene profile could be identified that could serve as diagnostic tool for disease classification.

At least 100ng of total RNA was used as an input for microarray analysis using the Affymetrix Human Gene 2.0 ST Array platform and differentially expressed genes, with FC >1.5, between matched lesional and non-lesional CDLE together with healthy donors were compared.

Analysis showed substantial upregulation of Interferon (IFN)-stimulated genes (ISGs), pMx1, IFI6, BST2, OAS2 and CXCL10 in lesional samples compared to matched non-lesional and healthy patients.

β2M, complement factor 3 (C3) and genes involved in apoptotic cell death (OAS2 and XAF1) were also upregulated in CDLE lesional samples compared to non-lesional and controls.

However, the pattern of differential expression between lesional and non-lesional CDLE was the same as the DE pattern in non-lesional versus healthy samples with the exception of CXCL9 and β2M (involved CD8+ T-cell responses) which were upregulated in non-lesional CDLE.

Microarray results were confirmed by RT-qPCR on the same individual samples used in array analysis but included samples from patients with active scalp psoriasis.

Consistent with the array data, expression of a panel of previously identified ISGs, β2M and C3 were significantly higher in lesional CDLE as compared with psoriasis or healthy samples. Again, no significant differences in ISGs between non-lesional and healthy samples were detected. However, bone morphogenetic protein 2 (BMP2) and kinase insert domain receptor (KDR) which encodes for vascular endothelial growth factor receptor 2 (VEGF2) were markedly upregulated in psoriatic samples in comparison to CDLE samples.

In summary, in this pilot study the authors showed that a disease-specific gene signature can be obtained from plucked HFs. This offers a promising, non-invasive, easy to perform approach with advantages over the use of skin biopsies. The results not only allow quick and precise identification and classification of the lupus disease but also shed light on the biological mechanism of the disorder. The strong upregulation of ISGs, apoptosis, complement and MHC I related genes, which are a hallmark of the immunopathology of CDLE, suggest irreversible damage to the stem cell niche in lupus, which in healthy patients is protected from inflammatory challenges from CD8+ cytotoxic T cells. In addition, downregulation of BMP and KDR leads to an impaired tissue repair response most likely contributing atrophic scarring seen in CDLE patients.

This research shows that using plucked HFs followed by transcriptomic analysis of disease specific genes has the potential to save cost and avoid invasive biopsies. It enables increased precision of disease classification and offers a significant advantage for research into the pathophysiology of scarring alopecia by allowing repeated sampling in the context of environmental challenges (e.g. UV) or therapeutic interventions.

Reference

Mahammad Shalbaf et al., 2019. Plucked hair follicles from patients with chronic discoid lupus erythematosus show a disease-specific molecular signature. Lupus Science and Medicine 6

https://doi.org/10.1136/lupus-2019-000328

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