Project description:Cell clones that lack P53 signaling occur frequently in ulcerative colitis (UC) and are considered drivers in UC-associated colorectal cancer. Trp53 mutant cells often display decreased P53 signaling and have previously been shown to outcompete wild type (WT) cells in a mouse model of colitis (DSS colitis), but not in healthy mice. However, the mechanism responsible for the observed context-dependent effects of P53 are not understood. Therefore, we aimed to explore this by studying the behavior of Trp53-deficient cells specifically in injured mucosa. We have developed murine and organoid-based models to study the context dependent role of Trp53 knock-out (KO). We use inducible KO systems in mouse models of DSS colitis to study the loss of Trp53 in the injury and regenerative state. Colon organoids are employed to recapitulate the in vivo findings in order to elucidate the pathways involved.
Project description:Mammalian skin wounds heal by forming fibrotic scars. We report that reindeer antler velvet exhibits regenerative wound healing, whereas identical injury to back skin forms scar. This regenerative capacity was retained following ectopic transplantation of velvet to scar-forming sites. Single-cell mRNA/ATAC-Sequencing revealed that while uninjured velvet fibroblasts resembled human fetal fibroblasts, back skin fibroblasts were enriched in pro-inflammatory features resembling adult human fibroblasts. Injury elicited site-specific immune polarization; back skin fibroblasts amplified the immune response, whereas velvet fibroblasts adopted an immunosuppressive state leading to restrained myeloid maturation and hastened immune resolution ultimately enabling myofibroblast reversion to a regeneration-competent state. Finally, regeneration was blunted following application of back skin associated immunostimulatory signals or inhibition of pro-regenerative factors secreted exclusive to velvet fibroblasts. This study highlights a unique model to interrogate mechanisms underlying divergent healing outcomes and nominates both decoupling of stromal-immune crosstalk and reinforcement of pro-regenerative fibroblast programs to mitigate scar.
Project description:The early phase of colonic epithelial wound healing involves cellular reprogramming to a fetal-like state and reorganization of discrete crypt units into merged wound channels. After re-epithelialization is complete, a latter phase restoring homeostatic signaling and crypt patterning must occur. However, the signals that mediate this regenerative transition are unknown. Here we show that injury-associated upregulation of a cytokine receptor, tumor necrosis factor (TNF) receptor 2 (R2, TNFR2, Tnfrsf1b), suppresses fetal-like signaling and promotes crypt production. We used tissue clearing and whole-mount imaging, RNA-Seq, and organoid cultures to characterize mice with a colonic epithelial-specific deletion of TNFR2. These mice exhibited increased crypt size and reduced fission in adult homeostasis and after colitis, abnormal persistence of fetal-like molecular markers in organoids and after injury, reduced terminal differentiation, and increased proliferative potential. These results demonstrate how epithelial cells can adapt to inflammatory cues to regulate wound healing morphogenesis and signaling.
Project description:Colonic epithelial repair is a key determinant of health. After injury, repair initiates through phenotypic reprogramming of wounded epithelium to a regenerative state permissive for the activation of alternative stem cell populations and healing. Although cytokine signals such as interferons may help induce regenerative reprogramming, the signals that modify this state as the wound resolves remain largely unknown. Here we examined whether cytokine signaling mediated by tumor necrosis factor receptor 2 (TNFR2) influenced the wound repair process. We examined mice with targeted deletion of the Tnfrsf1b (TNFR2) gene in intestinal/colonic epithelium (Vil1::Cre;Tnfr2-f/f) and compared their transcriptional profiles to control (Tnfr2-f/f) mice. We sorted EpCAM+ (epithelial) cells from Vil1::Cre;Tnfr2-f/f and control DSS-treated mice and performed bulk RNA-Seq. Comparison of transcript expression profile before and after DSS-induced colitis in control (Tnfr2-f/f) mice revealed upregulation of pathways associated with metabolic regulation, ribosomal function, oxidative stress, TNF signaling, and focal adhesions after DSS treatment. Pathway enrichment analysis demonstrated elevated regenerative (“fetal”) intestinal signaling, reduced inflammation, and increased proliferative signaling in Vil1::Cre;Tnfr2-f/f colonic epithelium after DSS treatment. The knockout epithelium also showed reduced expression of markers of differentiated colonic epithelium and elevated expression of progenitor cell signaling. Thus, the transcriptional data were consistent with increased regenerative signaling in TNFR2-knockout epithelium, suggesting that TNFR2 has a role in restraining the relatively undifferentiated regenerative state.
Project description:Background and aims: A coordinated stress and regenerative response is important following hepatocyte damage. Here, we investigate the phenotypes that result from genetic abrogation of individual components of the CHK2/ p53/ p21 pathway in a murine model of metabolic liver injury. Methods: NTBC was reduced or withdrawn in Fah / mice lacking Chk2, p53 or p21, and survival, tumor development, liver injury and regeneration were analyzed. Partial hepatectomies were performed and mice were challenged with the Fas-antibody Jo2. Results: In a model of metabolic liver injury, loss of p53, but not of Chk2, impairs the oxidative stress re-sponse and aggravates liver damage, indicative of a direct p53-dependent protective effect on hepatocytes. Cell cycle control during chronic liver injury critically depends on the presence of both p53 and its downstream effector p21. In p53-deficient hepatocytes, unchecked proliferation occurs despite a strong induction of p21, revealing a complex interdependency between p21 and p53. The increased regenerative potential in the absence of p53 cannot fully compensate the surplus injury and is not sufficient to promote survival. Despite the different phenotypes as-sociated with the loss of individual components of the DNA damage response, gene expression patterns are dominated by the severity of liver injury, but reflect distinct effects of p53 on prolif-eration and the anti-oxidative stress response. Conclusion: Characteristic phenotypes result from the genetic abrogation of individual components of the DNA damage response cascade in a liver injury model. The extent to which loss of gene function can be compensated, or affects injury and proliferation, depends on the level at which the cas-cade is interrupted.
Project description:Background and aims: A coordinated stress and regenerative response is important following hepatocyte damage. Here, we investigate the phenotypes that result from genetic abrogation of individual components of the CHK2/ p53/ p21 pathway in a murine model of metabolic liver injury. Methods: NTBC was reduced or withdrawn in FAH-/- mice lacking Chk2, p53 or p21, and survival, tumor development, liver injury and regeneration were analyzed. Partial hepatectomies were performed and mice were challenged with the Fas-antibody Jo2. Results: In a model of metabolic liver injury, loss of p53, but not of Chk2, impairs the oxidative stress re-sponse and aggravates liver damage, indicative of a direct p53-dependent protective effect on hepatocytes. Cell cycle control during chronic liver injury critically depends on the presence of both p53 and its downstream effector p21. In p53-deficient hepatocytes, unchecked proliferation occurs despite a strong induction of p21, revealing a complex interdependency between p21 and p53. The increased regenerative potential in the absence of p53 cannot fully compensate the surplus injury and is not sufficient to promote survival. Despite the different phenotypes as-sociated with the loss of individual components of the DNA damage response, gene expression patterns are dominated by the severity of liver injury, but reflect distinct effects of p53 on prolif-eration and the anti-oxidative stress response. Conclusion: Characteristic phenotypes result from the genetic abrogation of individual components of the DNA damage response cascade in a liver injury model. The extent to which loss of gene function can be compensated, or affects injury and proliferation, depends on the level at which the cas-cade is interrupted.
Project description:The developmental maturation of a neuron requires the completion of neuronal polarization preceding the formation of a synapse. Whether neuronal polarization marks the decline in growth competence in the injured mammalian adult nervous system remains elusive. Here we show that gene expression and epigenetic signatures associated with the regenerative growth ability of dorsal root ganglia (DRG) sensory neurons are lost during the transition from a non-polarized to a polarized state. The transcriptional co-factor Cited2 was found to be epigenetically upregulated in immature DRG and following a regenerative injury, but it remained unchanged by a non-regenerative spinal cord injury (SCI). Next, Cited2 was overexpressed in DRG neurons in a model of SCI in mice where it promoted sensory axon growth and reversed the gene expression signatures associated with neuronal maturation. Importantly, Cited2 expression stirred the maturation of DRG neurons towards a non-polarized state. Together, these data suggest that the transition from a non-polarized to a polarized state marks the reversible loss of the regenerative ability of a neuron, thus paving the way to targeted repair strategies relying on neuronal de-maturation.
Project description:Cell state (phenotypic) plasticity is a carefully regulated feature of adult epithelial cells that enables adaptive responses to injury, inflammation, and other forms of stress.Aberrant expansion of the normally restricted capability for cell state plasticity to escape terminal differentiation is a critical aspect of neoplasia. The nongenetic factors and specific programs that mediate aberrant cell state plasticity and impaired differentiationrequire deeper characterization to understand this elusive aspect ofcancer pathogenesis. Using genetically engineered andcarcinogen-induced murine models of intestinal neoplasia, wedemonstrate that impaired differentiation is a conserved eventpreceding cancer development. Single cell RNA-sequencing (scRNA-seq)of neoplastic intestinal lesions from both mouse models and a patientwith familial adenomatous polyposis revealed that cancer initiates byadopting an aberrant transcriptional state characterized bynonoverlapping expression of a regenerative pathway, marked by Ly6a(Sca-1), and a fetal intestinal program, positive for Tacstd2 (Trop2).Genetic inactivation of Sox9 prevented adenoma formation in ApcKOmice, obstructed emergence of aberrant regenerative and fetalintestinal programs, and restored multi-lineage differentiation byscRNA-seq. Expanded chromatin accessibility at regeneration and fetalgenes upon Apc inactivation was reduced by concomitant Sox9suppression. These studies indicate that aberrant cell stateplasticity mediated by unabated regenerative activity anddevelopmental reprogramming precedes cancer development.
Project description:Cell state (phenotypic) plasticity is a carefully regulated feature of adult epithelial cells that enables adaptive responses to injury, inflammation, and other forms of stress.Aberrant expansion of the normally restricted capability for cell state plasticity to escape terminal differentiation is a critical aspect of neoplasia. The nongenetic factors and specific programs that mediate aberrant cell state plasticity and impaired differentiationrequire deeper characterization to understand this elusive aspect ofcancer pathogenesis. Using genetically engineered andcarcinogen-induced murine models of intestinal neoplasia, wedemonstrate that impaired differentiation is a conserved eventpreceding cancer development. Single cell RNA-sequencing (scRNA-seq)of neoplastic intestinal lesions from both mouse models and a patientwith familial adenomatous polyposis revealed that cancer initiates byadopting an aberrant transcriptional state characterized bynonoverlapping expression of a regenerative pathway, marked by Ly6a(Sca-1), and a fetal intestinal program, positive for Tacstd2 (Trop2).Genetic inactivation of Sox9 prevented adenoma formation in ApcKOmice, obstructed emergence of aberrant regenerative and fetalintestinal programs, and restored multi-lineage differentiation byscRNA-seq. Expanded chromatin accessibility at regeneration and fetalgenes upon Apc inactivation was reduced by concomitant Sox9suppression. These studies indicate that aberrant cell stateplasticity mediated by unabated regenerative activity anddevelopmental reprogramming precedes cancer development.