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. 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 grow in response to stretching has been exploited in reconstructive surgery1. Although the response of epidermal cells to stretching has been studied in vitro2,3, it remains unclear how mechanical forces affect their behaviour in vivo. Here we develop a mouse model in which the consequences of stretching on skin epidermis can be studied at single-cell resolution. Using a multidisciplinary approach that combines clonal analysis with quantitative modelling and single-cell RNA sequencing, we show that stretching induces skin expansion by creating 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 step-by-step mechanisms that control stretch-mediated tissue expansion at single-cell resolution in vivo.
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:Context: Increased uterine stretch appears to increase the risk of preterm labour, but the mechanism is unknown. Objectives: To identify a targetable mechanism mediating the effect of stretch on human myometrium. Design: Myometrial explants, prepared from biopsies obtained at elective caesarean delivery, were either studied acutely, or were maintained in prolonged culture (up to 65 h) under tension with either a 0.6 g or 2.4 g mass, and compared using in vitro contractility, whole genome array, and qRT-PCR. Results: Increased stretch for 24 or 65 h increased potassium-induced and oxytocin-induced contractility. Gene array identified 62 differentially expressed transcripts after 65 h exposure to increased stretch. Two probes for gastrin-releasing peptide (GRP), a known stimulatory agonist of smooth muscle, were among the top five up-regulated by stretch (3.4-fold and 2.0-fold). Up-regulation of GRP by stretch was confirmed in a separate series of 10 samples using qRT-PCR (2.8-fold, P = 0.01). GRP stimulated contractions acutely when added to freshly obtained myometrial strips in 3 out of 9 cases, but Western blot demonstrated expression of the GRP receptor in 9 out of 9 cases. Prolonged incubation of stretched explants in the GRP antagonists PD-176252 or RC-3095 (65 and 24 h respectively) significantly reduced potassium chloride and oxytocin-induced contractility. Conclusion: Stretch of human myometrium increases contractility and stimulates the expression of a known smooth muscle stimulatory agonist, GRP. Incubation of myometrium in GRP receptor antagonists ameliorates the effect of stretch. GRP may be a target for novel therapies to reduce the risk of preterm birth in multiple pregnancy.
Project description:Mechanical stress is a potent regulator of cell growth, contractility and gene regulation. Abnormal uterine distension during pregnancy increases the risk of preterm birth and likely activates crosstalk between multiple signaling networks with protein phosphorylation playing a critical role. Telomerized human uterine smooth muscle cells were exposed to 18% biaxial stretch for 5 min and the phosphoproteome was probed by mass spectrometry. We observed specific phospho-activation of mitogen activated protein kinase at threonine 183 and tyrosine 185, myosin regulatory light chain 9 at threonine 19, and heat shock protein 27 at serine 82. Our analysis revealed protein phosphorylation changes in signaling pathways related to actin cytoskeleton remodeling, activation of the focal adhesion kinase pathway, smooth muscle contraction and mechanistic target of rapamycin activation. These data point to potential mechanistic links between stretch-induced phosphorylation and development of the contractile phenotype in myometrial cells.
Project description:The development of meter-long axons within the nervous system is a remarkable, yet unresolved biological process. The most widely studied aspects of neuronal growth focus on the extension and chemotropism of growth cones. However, over the course of organismal development, short axons elongate up to one meter in length with the systemic expansion of mitotic tissues. The preeminent regulatory mechanism for such synchronized growth between the nervous system and the tissues it spans, is the biomechanical stretch of axons, a known stimulus of axon growth. Here, we reveal the transcriptional profile of stretch-mediated axon growth as found using embryonic rat dorsal root ganglia neurons stretch-grown in vitro.
Project description:Context: Increased uterine stretch appears to increase the risk of preterm labour, but the mechanism is unknown. Objectives: To identify a targetable mechanism mediating the effect of stretch on human myometrium. Design: Myometrial explants, prepared from biopsies obtained at elective caesarean delivery, were either studied acutely, or were maintained in prolonged culture (up to 65 h) under tension with either a 0.6 g or 2.4 g mass, and compared using in vitro contractility, whole genome array, and qRT-PCR. Results: Increased stretch for 24 or 65 h increased potassium-induced and oxytocin-induced contractility. Gene array identified 62 differentially expressed transcripts after 65 h exposure to increased stretch. Two probes for gastrin-releasing peptide (GRP), a known stimulatory agonist of smooth muscle, were among the top five up-regulated by stretch (3.4-fold and 2.0-fold). Up-regulation of GRP by stretch was confirmed in a separate series of 10 samples using qRT-PCR (2.8-fold, P = 0.01). GRP stimulated contractions acutely when added to freshly obtained myometrial strips in 3 out of 9 cases, but Western blot demonstrated expression of the GRP receptor in 9 out of 9 cases. Prolonged incubation of stretched explants in the GRP antagonists PD-176252 or RC-3095 (65 and 24 h respectively) significantly reduced potassium chloride and oxytocin-induced contractility. Conclusion: Stretch of human myometrium increases contractility and stimulates the expression of a known smooth muscle stimulatory agonist, GRP. Incubation of myometrium in GRP receptor antagonists ameliorates the effect of stretch. GRP may be a target for novel therapies to reduce the risk of preterm birth in multiple pregnancy. 9 paired samples of human myometrium cultured under low (0.6g) or high (2.4g) tension
Project description:The goal of this study was to examine the effect of the major axis of biaxial mechanical stretch on cardiac myocyte gene expression and to identify the signaling pathways and transcription factors regulating these changes. Neonatal cardiac myocytes were cultured on a micropatterned substrate, and the primary stretch axis was applied either parallel or transverse to the myofibril direction. RNA sequencing was conducted to study whole genomic expression changes after acute cardiac myocyte stretch. The results showed a more robust gene response to longitudinal than to transverse stretch. After 30 minutes of stretch, 53 and 168 genes were considered differentially expressed (DE) from transverse and longitudinal stretch, respectively. After 4 hours, the number of DE genes increased to 795 in longitudinal stretch while it decreased to 35 in transverse stretch. Gene ontology term (GO) analysis indicated enrichment of TF activity and protein kinase activity by both stretch axes; whereas longitudinal but not transverse stretch caused expression of genes involved in sarcomere organization and cytoskeletal protein binding.