Project description:The hair follicle stem cell niche is an immune-privileged microenvironment, characterized by reduced antigen presentation, thus shielding against permanent immune-mediated tissue damage. In this study, we demonstrated the protective role of hair follicle-specific epidermal growth factor receptor (EGFR) against scarring hair follicle destruction. Mechanistically, disruption of EGFR signalling generated a cell-intrinsic hypersensitivity within the JAK-STAT1 pathway, which, synergistically with interferon gamma expressing CD8 T-cell and NK-cell-mediated inflammation, compromised the stem cell niche. Hair follicle-specific genetic depletion of either JAK1/2 or STAT1 or therapeutic inhibition of JAK1/2 ameliorated the inflammation, restored skin barrier function and activated the residual stem cells to resume hair growth in mouse models of epidermal and hair follicle-specific EGFR deletion. Skin biopsies from EGFR inhibitor-treated and cicatricial alopecia patients indicated active STAT1 signalling and interferon target expression. Notably, a case study of folliculitis decalvans, characterized by progressive hair loss, scaling and perifollicular erythema, demonstrated successful treatment with JAK1/2 inhibition. Our findings offer molecular insights and present a mechanism-based therapeutic strategy for addressing chronic folliculitis associated with EGFR-inhibitor anti-cancer therapy and cicatricial alopecia.
Project description:The hair follicle stem cell niche is an immune-privileged microenvironment, characterized by reduced antigen presentation, thus shielding against permanent immune-mediated tissue damage. In this study, we demonstrated the protective role of hair follicle-specific epidermal growth factor receptor (EGFR) against scarring hair follicle destruction. Mechanistically, disruption of EGFR signalling generated a cell-intrinsic hypersensitivity within the JAK-STAT1 pathway, which, synergistically with interferon gamma expressing CD8 T-cell and NK-cell-mediated inflammation, compromised the stem cell niche. Hair follicle-specific genetic depletion of either JAK1/2 or STAT1 or therapeutic inhibition of JAK1/2 ameliorated the inflammation, restored skin barrier function and activated the residual stem cells to resume hair growth in mouse models of epidermal and hair follicle-specific EGFR deletion. Skin biopsies from EGFR inhibitor-treated and cicatricial alopecia patients indicated active STAT1 signalling and interferon target expression. Notably, a case study of folliculitis decalvans, characterized by progressive hair loss, scaling and perifollicular erythema, demonstrated successful treatment with JAK1/2 inhibition. Our findings offer molecular insights and present a mechanism-based therapeutic strategy for addressing chronic folliculitis associated with EGFR-inhibitor anti-cancer therapy and cicatricial alopecia.
Project description:The hair follicle stem cell niche is an immune-privileged microenvironment, characterized by reduced antigen presentation, thus shielding against permanent immune-mediated tissue damage. In this study, we demonstrated the protective role of hair follicle-specific epidermal growth factor receptor (EGFR) against scarring hair follicle destruction. Mechanistically, disruption of EGFR signalling generated a cell-intrinsic hypersensitivity within the JAK-STAT1 pathway, which, synergistically with interferon gamma expressing CD8 T-cell and NK-cell-mediated inflammation, compromised the stem cell niche. Hair follicle-specific genetic depletion of either JAK1/2 or STAT1 or therapeutic inhibition of JAK1/2 ameliorated the inflammation, restored skin barrier function and activated the residual stem cells to resume hair growth in mouse models of epidermal and hair follicle-specific EGFR deletion. Skin biopsies from EGFR inhibitor-treated and cicatricial alopecia patients revealed an active JAK-STAT1 signalling signature along with up-regulation of antigen presentation and down-regulation of key components of the EGFR pathway. Our findings offer molecular insights and highlight a mechanism-based therapeutic strategy for addressing chronic folliculitis associated with EGFR-inhibitor anti-cancer therapy and cicatricial alopecia.
Project description:Autoimmune alopecia is a prevalent, highly morbid disease. The inflammatory pathways causing hair loss are not well characterized. We profiled two tissue microarrays comparing healthy skin to scarring alopecia and alopecia areata via spatial transcriptomics to analyze the genes and pathways dysregulated in autoimmune alopecia in direct proximity to the hair follicle.
Project description:Scarring alopecia consists of a collection of disorders characterized by destruction of hair follicles, replacement with fibrous scar tissue, and irreversible hair loss. Alopecia affects men and women worldwide and can be a significant source of psychological stress and depression for affected individuals. The purpose of this study was to explore metabolic profiles in scalp tissue samples from normal control subjects (n=6) and in matched samples obtained from affected (n=12) and unaffected (n=12) areas of the scalp in patients with lymphocytic Frontal Fibrosing Alopecia (FFA). Frontal fibrosing alopecia results from destruction of hair follicles by an inflammatory lymphocytic infiltrate that is localized around the upper portion of the hair follicle.
Project description:JAK inhibition by means of clinically available pan JAK inhibitors has recently demonstrated great efficacy in both restoring hair growth and resolving inflammation in the skin of patients with Alopecia Areata (AA). These effects are dose dependent and mainly efficacious at ranges close to a questionable risk profile. Given the great responses to JAK inhibition and the current lack of efficacious treatments in AA, it is exciting to explore the possibilities to separate the beneficial and adverse effects in order to provide a successful treatment option for these patients where the medical need is still vastly unmet. Selective JAK1 inhibition mainly affects genes downstream of STAT1, STAT3 & STAT6 in human immune cells. Importantly, pathways like T-cell differentiation and lymphopoiesis are less affected by the selective JAK1 inhibitor versus less specific JAK inhibitors like tofacitinib and ruxolitinib. These findings indicate that it is feasible to develop more selective and specific JAK1 inhibitors that are as efficacious as pan-JAK inhibitors but with a better safety profile as systemic exposure is mandatory for efficacy in this disease.
Project description:STAT1 is an important regulator of NK cell maturation and cytotoxicity. Although the consequences of Stat1-deficiency have been described in detail the underlying molecular functions of STAT1 in NK cells are only partially understood. Here we describe a novel non-canonical role of STAT1 that was unmasked in NK cells expressing Stat1-Y701F. This mutation prevents JAK-dependent phosphorylation, subsequent nuclear translocation and cytokine-induced transcriptional activity. As expected Stat1-Y701F mice displayed impaired NK cell maturation comparable to Stat1-/- animals. In contrast Stat1-Y701F NK cells exerted a significantly enhanced cytotoxicity in vitro and in vivo suggesting a so-far unknown cytoplasmic function. Using immunofluorescence technology we uncovered the recruitment of STAT1 to the immunological synapse during NK cell killing. A Stat1ind mouse expressing FLAG-tagged STAT1α was used to study the STAT1α interactome in NK cells. Mass spectrometry revealed that STAT1 directly binds proteins involved in cell junction formation and proteins associated to membrane or membrane-bound vesicles. We propose a novel function for STAT1 in the immunological synapse of NK cells regulating tumor surveillance and cytotoxicity.