Shiu, J;Zhang, L;Lentsch, G;Flesher, JL;Jin, S;Polleys, CM;Jo, SJ;Mizzoni, C;Mobasher, P;Kwan, J;Rius-Diaz, F;Tromberg, BJ;Georgakoudi, I;Nie, Q;Balu, M;Ganesan, AK;
PMID: 35653192 | DOI: 10.1172/jci.insight.154585
Vitiligo is an autoimmune skin disease characterized by the destruction of melanocytes by autoreactive CD8+ T cells. Melanocyte destruction in active vitiligo is mediated by CD8+ T cells but why white patches in stable disease persist is poorly understood. The interaction between immune cells, melanocytes, and keratinocytes in situ in human skin has been difficult to study due to the lack of proper tools. We combine non-invasive multiphoton microscopy (MPM) imaging and single-cell RNA sequencing (scRNA-seq) to identify subpopulations of keratinocytes in stable vitiligo patients. We show that, as compared to non-lesional skin, these keratinocytes are enriched in lesional vitiligo skin and shift their energy utilization towards oxidative phosphorylation. Systematic investigation of cell-cell communication networks show that this small population of keratinocyte secrete CXCL9 and CXCL10 to potentially drive vitiligo persistence. Pseudotemporal dynamics analyses predict an alternative differentiation trajectory that generates this new population of keratinocytes in vitiligo skin. Further MPM imaging of patients undergoing punch grafting treatment showed that keratinocytes favoring oxidative phosphorylation persist in non-responders but normalize in responders. In summary, we couple advanced imaging with transcriptomics and bioinformatics to discover cell-cell communication networks and keratinocyte cell states that can perpetuate inflammation and prevent repigmentation.
Cold Spring Harbor perspectives in biology
Ganier, C;Rognoni, E;Goss, G;Lynch, M;Watt, FM;
PMID: 35667795 | DOI: 10.1101/cshperspect.a041238
Fibroblasts are the main cell type in the dermis. They are responsible for the synthesis and deposition of structural proteins such as collagen and elastin, which are integrated into the extracellular matrix (ECM). Mouse and human studies using flow cytometry, cell culture, skin reconstitution, and lineage tracing experiments have shown the existence of different subpopulations of fibroblasts, including papillary fibroblasts, reticular fibroblasts, and fibroblasts comprising the dermal papilla at the base of the hair follicle. In recent years, the technological advances in single-cell sequencing have allowed researchers to study the repertoire of cells present in full-thickness skin including the dermis. Multiple groups have confirmed that distinct fibroblast populations can be identified in mouse and human dermis on the basis of differences in the transcriptional profile. Here, we discuss the current state of knowledge regarding dermal fibroblast heterogeneity in healthy mouse and human skin, highlighting the similarities and differences between mouse and human fibroblast subpopulations. We also discuss how fibroblast heterogeneity may provide insights into physiological wound healing and its dysfunction in pathological states such as hypertrophic and keloid scars.
Journal of molecular medicine (Berlin, Germany)
Sych, K;Nold, SP;Pfeilschifter, J;Vutukuri, R;Meisterknecht, J;Wittig, I;Frank, S;Goren, I;
PMID: 36633604 | DOI: 10.1007/s00109-022-02280-6
An injured skin is rapidly restored in a manner of wound healing. We have previously shown that intact insulin signaling and glucose uptake are fundamental to proper wound closure. Consequently, under exacerbated inflammation, compromised insulin action and glucose uptake lead to impaired healing. However, in spite of the increased attention to cell metabolism during tissue regeneration, metabolic mediators that govern cellular and physiological processes throughout skin repair remained largely elusive. Through assessment of mRNA using real-time PCR and protein blot analysis, we report that healing of cutaneous wounds comprise a boosted expression of genes involved in glycolysis, oxidative phosphorylation, pentose phosphate shunt, and glutamine anaplerosis. We further focused on the functional role of pyruvate kinase M (PKM) isoenzymes that catalyze the final and rate-limiting step of glycolysis. Whereas the expression of the metabolic constitutively active Pkm1 isozyme remained almost unchanged, Pkm2 is augmented during the inflammatory phase of healing. The immunohistochemistry and RNA in situ hybridization analysis showed a confined Pkm2 expression to keratinocytes of the hyperproliferative epithelium and, to a lesser extent, infiltrating neutrophils and monocytes as well as later on in macrophages. Notably, the expression of Pkm2 in keratinocytes facing the wound bed side colocalized with VEGF expression. The in vitro knockdown of PKM2 in HaCaT keratinocytes using small interfering (si) RNA confirmed an acute role for PKM2 in facilitating the complete induction of VEGF mRNA and protein expression in keratinocytes; this function is mainly HIF-1α independent. KEY MESSAGES: • Wound healing involves activation of glycolysis, oxidative phosphorylation, pentos-phosphate shunt, and replenishment of tri-carboxylic acid (TCA) cycle through glutamine anaplerosis. • The pyruvate kinase M2 (PKM2) isoform is upregulated during the inflammatory phase of cutaneous healing, mainly in keratinocytes of hyperproliferative epithelia. • In vivo, the expression of VEGF in wound keratinocytes is colocalized with PKM2. • PKM2 is required for full induction of VEGF in HaCaT keratinocytes in vitro.
Vu, R;Jin, S;Sun, P;Haensel, D;Nguyen, QH;Dragan, M;Kessenbrock, K;Nie, Q;Dai, X;
PMID: 35926463 | DOI: 10.1016/j.celrep.2022.111155
Delayed and often impaired wound healing in the elderly presents major medical and socioeconomic challenges. A comprehensive understanding of the cellular/molecular changes that shape complex cell-cell communications in aged skin wounds is lacking. Here, we use single-cell RNA sequencing to define the epithelial, fibroblast, immune cell types, and encompassing heterogeneities in young and aged skin during homeostasis and identify major changes in cell compositions, kinetics, and molecular profiles during wound healing. Our comparative study uncovers a more pronounced inflammatory phenotype in aged skin wounds, featuring neutrophil persistence and higher abundance of an inflammatory/glycolytic Arg1Hi macrophage subset that is more likely to signal to fibroblasts via interleukin (IL)-1 than in young counterparts. We predict systems-level differences in the number, strength, route, and signaling mediators of putative cell-cell communications in young and aged skin wounds. Our study exposes numerous cellular/molecular targets for functional interrogation and provides a hypothesis-generating resource for future wound healing studies.
Houser, A;Kazmi, A;Nair, A;Ji, A;
| DOI: 10.1016/j.xjidi.2023.100198
The development of multi-omic profiling tools has rapidly expanded in recent years, along with their use in profiling skin tissues in various contexts, including dermatologic diseases. Among these tools, single-cell RNA-sequencing (scRNA-seq) and spatial transcriptomics (ST) have emerged as widely adopted and powerful assays for elucidating key cellular components and their spatial arrangement within skin disease. Here, we review recent biological insights gained from the use of scRNA-seq and ST, and the advantages of combining both, for profiling skin disease, including aberrant wound healing, inflammatory skin diseases, and cancer. We discuss the role of scRNA-seq and ST for improving skin disease treatments and moving towards the goal of achieving precision medicine in dermatology, whereby patients can be optimally matched to treatments that maximize therapeutic response.
Journal of the American Academy of Dermatology
Singh, K;Valido, K;Swallow, M;Okifo, KO;Wang, A;Cohen, JM;Damsky, W;
PMID: 36780951 | DOI: 10.1016/j.jaad.2022.12.052
Dupilumab has revolutionized the treatment of atopic dermatitis. However, not all patients respond optimally, and this may relate to underlying molecular heterogeneity. Nevertheless, clinically useful and accessible methods to assess such heterogeneity have not been developed.We assessed whether cytokine staining and/or histologic features correlate with clinical response to dupilumab in patients with eczematous dermatitis.We retrospectively analyzed biopsies from 61 patients with eczematous dermatitis treated with dupilumab (90.2% met Hanifin-Rajka criteria for atopic dermatitis). RNA in situ hybridization was used to measure markers of type 2 (interleukin [IL]4, IL13), type 1 (interferon gamma) and type 3 (IL17A, IL17F, IL22) inflammation. Histologic features were also assessed. Patterns were compared among complete (n = 16), partial (n = 37), and nonresponders (n = 8) to dupilumab.We found that increased IL13 expression was associated with optimal response to dupilumab. In contrast, nonresponders tended to express less IL13 and relatively greater levels of type 1 and 3 cytokines. In addition, certain histologic features tended to correlate with improved response to dupilumab.Retrospective approach and small size of the nonresponder group.Cytokine RNA in situ hybridization may aid in treatment selection for eczematous disorders. Moreover, personalization of treatment selection for inflammatory skin diseases may be possible.
Wiedemann, J;Billi, A;Bocci, F;Kashgari, G;Xing, E;Tsoi, L;Meller, L;Swindell, W;Wasikowski, R;Xing, X;Ma, F;Gharaee-Kermani, M;Kahlenberg, J;Harms, P;Maverakis, E;Nie, Q;Gudjonsson, J;Andersen, B;
| DOI: 10.1016/j.celrep.2023.111994
Palmoplantar skin is structurally and functionally unique, but the transcriptional programs driving this specialization are unclear. Here, we use bulk and single-cell RNA sequencing of human palm, sole, and hip skin to describe the distinguishing characteristics of palmoplantar and non-palmoplantar skin while also uncovering differences between palmar and plantar sites. Our approach reveals an altered immune environment in palmoplantar skin, with downregulation of diverse immunological processes and decreased immune cell populations. Further, we identify specific fibroblast populations that appear to orchestrate key differences in cell-cell communication in palm, sole, and hip. Dedicated keratinocyte analysis highlights major differences in basal cell fraction among the three sites and demonstrates the existence of two spinous keratinocyte populations constituting parallel, site-selective epidermal differentiation trajectories. In summary, this deep characterization of highly adapted palmoplantar skin contributes key insights into the fundamental biology of human skin and provides a valuable data resource for further investigation.
Segaud, J;Yao, W;Marschall, P;Daubeuf, F;Lehalle, C;German, B;Meyer, P;Hener, P;Hugel, C;Flatter, E;Guivarch, M;Clauss, L;Martin, SF;Oulad-Abdelghani, M;Li, M;
PMID: 36050303 | DOI: 10.1038/s41467-022-32196-1
Atopic diseases, including atopic dermatitis (AD) and asthma, affect a large proportion of the population, with increasing prevalence worldwide. AD often precedes the development of asthma, known as the atopic march. Allergen sensitization developed through the barrier-defective skin of AD has been recognized to be a critical step leading to asthma, in which thymic stromal lymphopoietin (TSLP) was previously shown to be critical. In this study, using a laser-assistant microporation system to disrupt targeted skin layers for generating micropores at a precise anatomic depth of mouse skin, we model allergen exposure superficially or deeply in the skin, leading to epicutaneous sensitization or dermacutaneous sensitization that is associated with a different cytokine microenvironment. Our work shows a differential requirement for TSLP in these two contexts, and identifies an important function for IL-1β, which is independent of TSLP, in promoting allergen sensitization and subsequent allergic asthma.
American journal of medical genetics. Part A
Atzmony, L;Ugwu, N;Bercovitch, LG;Robinson-Bostom, L;Ko, CJ;Myung, P;Choate, KA;
PMID: 35972041 | DOI: 10.1002/ajmg.a.62951
Basaloid follicular hamartomas (BFH) are benign small basaloid skin tumors that can present as solitary or multiple lesions. Congenital BFH lesions arranged in a segmental distribution have been described, suggesting they derive from a somatic post-zygotic mutational event. Previously, BFH were described in Happle-Tinschert syndrome, which results from a post-zygotic SMO variant and is characterized by segmental BFH with variable involvement of the teeth, skeleton, and central nervous system. Here, we describe two patients with isolated segmental BFH and no systemic involvement. Paired whole exome sequencing of BFH and normal tissue revealed a pathogenic SMO c.1234 C>T, p.L412F variant restricted to BFH tissue. We characterized the proliferation index and expression of Hedgehog and Wnt/beta-catenin pathway related proteins in segmental BFH compared to sporadic basal cell carcinomas (BCCs) and found that segmental BFH had a lower proliferation index. Although segmental BFH expressed a similar level of Gli-1 compared to BCCs, levels of LEF-1 and SOX-9 expression in BFH were weaker for both and patchier for LEF-1. Our results show that a somatic SMO activating variant causes segmental BFH. Since these patients are prone to developing BCCs, differences in SOX9, LEF1, and Ki-67 expression can help distinguish between these two basaloid lesions.
Cold Spring Harbor Perspectives in Biology
Vu, R;Dragan, M;Sun, P;Werner, S;Dai, X;
| DOI: 10.1101/cshperspect.a041237
Epithelial and endothelial cells possess the inherent plasticity to undergo morphological, cellular, and molecular changes leading to their resemblance of mesenchymal cells. A prevailing notion has been that cutaneous wound reepithelialization involves partial epithelial-to-mesenchymal transition (EMT) of wound-edge epidermal cells to enable their transition from a stationary state to a migratory state. In this review, we reflect on past findings that led to this notion and discuss recent studies that suggest a refined view, focusing predominantly on in vivo results using mammalian excisional wound models. We highlight the concept of epithelial-mesenchymal plasticity (EMP), which emphasizes a reversible conversion of epithelial cells across multiple intermediate states within the epithelial-mesenchymal spectrum, and discuss the critical importance of restricting EMT for effective wound reepithelialization. We also outline the current state of knowledge on EMP in pathological wound healing, and on endothelial-to-mesenchymal transition (EndMT), a process similar to EMT, as a possible mechanism contributing to wound fibrosis and scar formation. Harnessing epithelial/endothelial-mesenchymal plasticity may unravel opportunities for developing new therapeutics to treat human wound healing pathologies.
Science translational medicine
Chavarria-Smith, J;Chiu, CPC;Jackman, JK;Yin, J;Zhang, J;Hackney, JA;Lin, WY;Tyagi, T;Sun, Y;Tao, J;Dunlap, D;Morton, WD;Ghodge, SV;Maun, HR;Li, H;Hernandez-Barry, H;Loyet, KM;Chen, E;Liu, J;Tam, C;Yaspan, BL;Cai, H;Balazs, M;Arron, JR;Li, J;Wittwer, AJ;Pappu, R;Austin, CD;Lee, WP;Lazarus, RA;Sudhamsu, J;Koerber, JT;Yi, T;
PMID: 36516271 | DOI: 10.1126/scitranslmed.abp9159
The epidermis is a barrier that prevents water loss while keeping harmful substances from penetrating the host. The impermeable cornified layer of the stratum corneum is maintained by balancing continuous turnover driven by epidermal basal cell proliferation, suprabasal cell differentiation, and corneal shedding. The epidermal desquamation process is tightly regulated by balance of the activities of serine proteases of the Kallikrein-related peptidases (KLK) family and their cognate inhibitor lymphoepithelial Kazal type-related inhibitor (LEKTI), which is encoded by the serine peptidase inhibitor Kazal type 5 gene. Imbalance of proteolytic activity caused by a deficiency of LEKTI leads to excessive desquamation due to increased activities of KLK5, KLK7, and KLK14 and results in Netherton syndrome (NS), a debilitating condition with an unmet clinical need. Increased activity of KLKs may also be pathological in other dermatoses such as atopic dermatitis (AD). Here, we describe the discovery of inhibitory antibodies against murine KLK5 and KLK7 that could compensate for the deficiency of LEKTI in NS. These antibodies are protective in mouse models of NS and AD and, when combined, promote improved skin barrier integrity and reduced inflammation. To translate these findings, we engineered a humanized bispecific antibody capable of potent inhibition of human KLK5 and KLK7. A crystal structure of KLK5 bound to the inhibitory Fab revealed that the antibody binds distal to its active site and uses a relatively unappreciated allosteric inhibition mechanism. Treatment with the bispecific anti-KLK5/7 antibody represents a promising therapy for clinical development in NS and other inflammatory dermatoses.
Ricardo-Gonzalez, RR;Kotas, ME;O'Leary, CE;Singh, K;Damsky, W;Liao, C;Arouge, E;Tenvooren, I;Marquez, DM;Schroeder, AW;Cohen, JN;Fassett, MS;Lee, J;Daniel, SG;Bittinger, K;Díaz, RE;Fraser, JS;Ali, N;Ansel, KM;Spitzer, MH;Liang, HE;Locksley, RM;
PMID: 36044899 | DOI: 10.1016/j.immuni.2022.08.001
Demodex mites are commensal parasites of hair follicles (HFs). Normally asymptomatic, inflammatory outgrowth of mites can accompany malnutrition, immune dysfunction, and aging, but mechanisms restricting Demodex outgrowth are not defined. Here, we show that control of mite HF colonization in mice required group 2 innate lymphoid cells (ILC2s), interleukin-13 (IL-13), and its receptor, IL-4Ra-IL-13Ra1. HF-associated ILC2s elaborated IL-13 that attenuated HFs and epithelial proliferation at anagen onset; in their absence, Demodex colonization led to increased epithelial proliferation and replacement of gene programs for repair by aberrant inflammation, leading to the loss of barrier function and HF exhaustion. Humans with rhinophymatous acne rosacea, an inflammatory condition associated with Demodex, had increased HF inflammation with decreased type 2 cytokines, consistent with the inverse relationship seen in mice. Our studies uncover a key role for skin ILC2s and IL-13, which comprise an immune checkpoint that sustains cutaneous integrity and restricts pathologic infestation by colonizing HF mites.