Mechanisms of stretch-mediated skin expansion at single cell resolution [array]
Ontology highlight
ABSTRACT: The ability of the skin to expand in response to stretching has, for decades, been exploited in reconstructive surgery. Several studies have investigated the response of stretching epidermal cells in vitro. However, it remains unclear how mechanical forces affect epidermal stem cell behaviour in vivo. Here, we develop a mouse model in which the temporal consequences of the stretching the skin epidermis can be studied. Using a multidisciplinary approach that combines clonal analysis and mathematical modelling, we show that mechanical force induces skin expansion by promoting the renewal of epidermal stem cells. This occurs through a structured response in which cell fates are coordinated locally by stem cells that switch between states primed for renewal or differentiation. Transcriptional and chromatin profiling identifies the gene regulatory networks modulated by mechanical force. Using a combination of pharmacological inhibition and several conditional gene loss-of-function mouse mutants, we dissect the signalling pathways that control force-mediated tissue expansion. We used microarray to molecularly profile basal cells isolated from the interfolliular epidermis during force-mediated tissue expansion and after 12-O-Tetradecanoylphorbol-13-acetate (TPA) tretment.
Project description:The ability of the skin to expand in response to stretching has, for decades, been exploited in reconstructive surgery. Several studies have investigated the response of stretching epidermal cells in vitro. However, it remains unclear how mechanical forces affect epidermal stem cell behaviour in vivo. Here, we develop a mouse model in which the temporal consequences of the stretching the skin epidermis can be studied. Using a multidisciplinary approach that combines clonal analysis and mathematical modelling, we show that mechanical force induces skin expansion by promoting the renewal of epidermal stem cells. This occurs through a structured response in which cell fates are coordinated locally by stem cells that switch between states primed for renewal or differentiation. Transcriptional and chromatin profiling identifies the gene regulatory networks modulated by mechanical force. Using a combination of pharmacological inhibition and several conditional gene loss-of-function mouse mutants, we dissect the signalling pathways that control force-mediated tissue expansion.
Project description:The ability of the skin to grow in response to stretching has, for decades, been exploited in reconstructive surgery. The response of epidermal cells to stretching has been studied in vitro. However, it remains unclear how mechanical forces affect epidermal cell behaviour in vivo. Here, we develop a mouse model in which the consequences of stretching on skin epidermis can be studied. Using a multidisciplinary approach that combines clonal analysis with quantitative modelling and single-cell RNA-seq, we show that stretching induces skin expansion by a transient bias in the renewal activity of epidermal stem cells, while a second subpopulation of basal progenitors remains committed to differentiation. Transcriptional and chromatin profiling identifies how cell states and gene regulatory networks are modulated by stretching. Using pharmacological inhibitors and mouse mutants, we define the mechanisms that control stretch-mediated tissue expansion.
Project description:Mammalian epidermal stem cells maintain homeostasis of skin epidermis and contribute to its regeneration throughout adult life. While two-dimensional mouse epidermal stem cell cultures have been established decades ago, a long-term, feeder cell- and serum-free culture system recapitulating murine epidermal architecture has not been available. Here we describe an epidermal organoid culture system that allows long-term, genetically stable expansion of adult epidermal stem cells. Our epidermal expansion media combines atypically high calcium concentrations, activation of cyclic AMP, FGF and R-spondin signaling with inhibition of BMP signaling. Organoids are established robustly from adult mouse skin and expand over at least 6 months, while maintaining the basal-apical organization of the mouse interfollicular epidermis. The system represents a powerful tool to study epidermal homeostasis and disease in vitro.
Project description:The skin expansion technique is widely applied in Plastic and Reconstructive Surgeries. Skin expansion induces skin growth and is an ideal approach for large-scale skin deformity reconstruction. However, the capacity for skin expansion is limited and searching for ways to enhance the expansion efficiency is a challenge. In this experiment, we aimed to explore the possible mechanism of skin expansion, and to find a potential therapeutic target on promoting skin growth.
Project description:The skin epidermis is a highly compartmentalised tissue consisting of a cornifying epithelium called the interfollicular epidermis (IFE) and associated hair follicles (HFs). Several stem cell populations have been described that mark specific sub compartments in the skin but none of them is IFE-specific. Here we identify Troy as a marker of IFE and HF infundibulum basal layer cells in embryonic and adult human and mouse epidermis. Genetic lineage-tracing experiments demonstrate that Troy-expressing basal cells contribute to long-term renewal of all layers of the cornifying epithelium. Single-cell transcriptomics and organoid assays of Troy-expressing cells as well as their progeny confirmed stem cell identity as well as the ability to generate differentiating daughter cells. In conclusion, we define Troy as a marker of epidermal basal cells that govern interfollicular epidermal renewal and cornification.
Project description:Uniquely among mammalian organs, skin is capable of dramatic size change in adults, yet the mechanisms underlying this striking capacity are unclear. Here, we utilize a system of controlled tissue expansion in mice to uncover cellular and molecular determinants of skin growth. Through machine learning-guided three-dimensional tissue reconstruction, we capture morphometric changes in growing skin. We find that most growth is driven by the proliferation of the epidermis in response to mechanical tension, with more limited changes in dermal and subdermal compartments. Epidermal growth is achieved through preferential activation and differentiation of not Lgr5+, but instead Lgr6+ stem cells of the interfollicular epidermis, driven in part by the Hippo pathway. By single-cell RNA sequencing, we uncover further changes in mechanosensitive and metabolic pathways underlying growth control in the skin. These studies point to therapeutic strategies to enhance skin growth and establish a platform for understanding organ size dynamics in adult mammals.
Project description:Uniquely among mammalian organs, skin is capable of dramatic size change in adults, yet the mechanisms underlying this striking capacity are unclear. Here, we utilize a system of controlled tissue expansion in mice to uncover cellular and molecular determinants of skin growth. Through machine learning-guided three-dimensional tissue reconstruction, we capture morphometric changes in growing skin. We find that most growth is driven by the proliferation of the epidermis in response to mechanical tension, with more limited changes in dermal and subdermal compartments. Epidermal growth is achieved through preferential activation and differentiation of not Lgr5+, but instead Lgr6+ stem cells of the interfollicular epidermis, driven in part by the Hippo pathway. By single-cell RNA sequencing, we uncover further changes in mechanosensitive and metabolic pathways underlying growth control in the skin. These studies point to therapeutic strategies to enhance skin growth and establish a platform for understanding organ size dynamics in adult mammals.
Project description:Psoriasis vulgaris is a chronic inflammatory skin disease which tends to affect the extensor surface of the body. IL-17A and IL-23 antagonists are currently the main and powerful therapeutic choices but the skin areas which are subject to stretching, namely knees, elbows and the lower back, are often reluctant to treatments. ; Hence, we hypothesize that stretching has a dominant effect on psoriasis development. First, we found that, in imiquimod-treated psoriasis-like mouse model, mechanical stretch promotes a significant increase in clinical severity, epidermal thickness, and inflammatory cell infiltration of psoriasis. Transcriptomics profiling revealed that Il6 and Il1b genes are significantly upregulated and play a major role in the activation and recruitment of neutrophils, macrophages, and T cells in stretching group. Upstream analysis further identifies NF-κB as a critical transcription factor to drive pro-inflammatory cytokine expression during stretch application. Immunofluorescence staining confirmed the increased expression of IL-1β and IL-6. In summary, our findings uncover that the mechanical biology contributes to psoriasis progression mainly through enhancing the production of IL-1β and IL-6.
Project description:Despite the strong need for the large-scale generation of human epidermal cells for cell therapy of extensive and severe skin injury, tissue-engineered skin construction and dermatological investigation, the effectiveness of current culture methods is limited and have yet to meet the huge demands sufficiently. Here, we report the establishment of a simple and robust 3D culture system using chemical defined, serum-free medium supplemented with small molecules and growth factors, tailored for human epidermal organoids generation and expansion. The conditions allowed 10,000-fold expansion of the primary epidermal cells within 6 weeks, with the cell architecture and gene expression preserved. We further noticed that only Integrin α6-positive basal stem cells freshly isolated from human epidermis could form expandable epidermal organoids. The epidermal cells inside of the organoids also have the potential to reconstruct multi-layered human epidermis equivalents under classical air-liquid interface condition. Remarkably, the epidermal organoids enable to model the anthropophilic and epidermis-restricted Trichophyton Rubrum infection. This model faithfully mimics and reflects the clinical pathological reactions of reinforced physical barrier by promoting keratinocytes differentiation and accelerated formation of the stratum corneum for adaptation and resistance to infection. Furthermore, the infection model also suggested that constraining host IL-1 signaling may underline the high degree of adaptation of Trichophyton Rubrum to human skin, and the tendency to be chronic and recurrent infection. Thus, human epidermal organoids present a powerful platform for modeling human dermatology, skin tissue engineering and cell therapy.