Metabolic rewiring in skin epidermis drives tolerance to oncogenic mutations.

Skin epithelial stem cells correct aberrancies induced by oncogenic mutations. Oncogenes invoke different strategies of epithelial tolerance; while wild-type cells outcompete β-catenin-gain-of-function (βcatGOF) cells, Hras cells outcompete wild-type cells. Here we ask how metabolic states change as wild-type stem cells interface with mutant cells and drive different cell-competition outcomes.

Oncogenic Kras induces spatiotemporally specific tissue deformation through converting pulsatile into sustained ERK activation.

Tissue regeneration and maintenance rely on coordinated stem cell behaviours. This orchestration can be impaired by oncogenic mutations leading to cancer. However, it is largely unclear how oncogenes perturb stem cells' orchestration to disrupt tissue.

Organ function is preserved despite reorganization of niche architecture in the hair follicle.

The ability of stem cells to build and replenish tissues depends on support from their niche. Although niche architecture varies across organs, its functional importance is unclear. During hair follicle growth, multipotent epithelial progenitors build hair via crosstalk with their remodeling fibroblast niche, the dermal papilla, providing a powerful model to functionally interrogate niche architecture.

Injury prevents Ras mutant cell expansion in mosaic skin.

Healthy skin is a mosaic of wild-type and mutant clones. Although injury can cooperate with mutated Ras family proteins to promote tumorigenesis, the consequences in genetically mosaic skin are unknown. Here we show that after injury, wild-type cells suppress aberrant growth induced by oncogenic Ras.

Mechanisms of skin vascular maturation and maintenance captured by longitudinal imaging of live mice.

A functional network of blood vessels is essential for organ growth and homeostasis, yet how the vasculature matures and maintains homeostasis remains elusive in live mice. By longitudinally tracking the same neonatal endothelial cells (ECs) over days to weeks, we found that capillary plexus expansion is driven by vessel regression to optimize network perfusion. Neonatal ECs rearrange positions to evenly distribute throughout the developing plexus and become positionally stable in adulthood.

Cell cycle controls long-range calcium signaling in the regenerating epidermis.

Skin homeostasis is maintained by stem cells, which must communicate to balance their regenerative behaviors. Yet, how adult stem cells signal across regenerative tissue remains unknown due to challenges in studying signaling dynamics in live mice. We combined live imaging in the mouse basal stem cell layer with machine learning tools to analyze patterns of Ca2+ signaling.

Skin-resident immune cells actively coordinate their distribution with epidermal cells during homeostasis.

Organs consist of multiple cell types that ensure proper architecture and function. How different cell types coexist and interact to maintain their homeostasis in vivo remains elusive. The skin epidermis comprises mostly epithelial cells, but also harbours Langerhans cells (LCs) and dendritic epidermal T cells (DETCs).

Hair follicle regeneration suppresses Ras-driven oncogenic growth.

Mutations associated with tumor development in certain tissues can be nontumorigenic in others, yet the mechanisms underlying these different outcomes remains poorly understood. To address this, we targeted an activating Hras mutation to hair follicle stem cells and discovered that Hras mutant cells outcompete wild-type neighbors yet are integrated into clinically normal skin hair follicles. In contrast, targeting the Hras mutation to the upper noncycling region of the skin epithelium leads to benign outgrowths.

In vivo dynamics of T cells and their interactions with dendritic cells in mouse cutaneous graft-versus-host disease.

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in allogeneic hematopoietic stem cell transplantation (alloSCT). By static microscopy, cutaneous GVHD lesions contain a mix of T cells and myeloid cells. We used 2-photon intravital microscopy to investigate the dynamics of CD4 and CD8 T cells and donor dendritic cells (DCs) in cutaneous GVHD lesions in an MHC-matched, multiple minor histocompatibility antigen-mismatched (miHA) model.

Correction of aberrant growth preserves tissue homeostasis.

Cells in healthy tissues acquire mutations with surprising frequency. Many of these mutations are associated with abnormal cellular behaviours such as differentiation defects and hyperproliferation, yet fail to produce macroscopically detectable phenotypes. It is currently unclear how the tissue remains phenotypically normal, despite the presence of these mutant cells.

Differential requirements for myeloid leukemia IFN-γ conditioning determine graft-versus-leukemia resistance and sensitivity.

The graft-versus-leukemia (GVL) effect in allogeneic hematopoietic stem cell transplantation (alloSCT) is potent against chronic phase chronic myelogenous leukemia (CP-CML), but blast crisis CML (BC-CML) and acute myeloid leukemias (AML) are GVL resistant. To understand GVL resistance, we studied GVL against mouse models of CP-CML, BC-CML, and AML generated by the transduction of mouse BM with fusion cDNAs derived from human leukemias. Prior work has shown that CD4+ T cell-mediated GVL against CP-CML and BC-CML required intact leukemia MHCII; however, stem cells from both leukemias were MHCII negative.

Profound depletion of host conventional dendritic cells, plasmacytoid dendritic cells, and B cells does not prevent graft-versus-host disease induction.

The efficacy of allogeneic hematopoietic stem cell transplantation is limited by graft-versus-host disease (GVHD). Host hematopoietic APCs are important initiators of GVHD, making them logical targets for GVHD prevention. Conventional dendritic cells (DCs) are key APCs for T cell responses in other models of T cell immunity, and they are sufficient for GVHD induction.

Mechanisms of antigen presentation to T cells in murine graft-versus-host disease: cross-presentation and the appearance of cross-presentation.

Recipient antigen-presenting cells (APCs) initiate GVHD by directly presenting host minor histocompatibility antigens (miHAs) to donor CD8 cells. However, later after transplantation, host APCs are replaced by donor APCs, and if pathogenic CD8 cells continue to require APC stimulation, then donor APCs must cross-present host miHAs. Consistent with this, CD8-mediated GVHD is reduced when donor APCs are MHC class I(-).

Memory T cells from minor histocompatibility antigen-vaccinated and virus-immune donors improve GVL and immune reconstitution.

Donor T cells contribute to the success of allogeneic hematopoietic stem cell transplantation (alloSCT). Alloreactive donor T cells attack leukemia cells, mediating the GVL effect. Donor T cells, including the memory T cells (T(M)) that are generated after infection, also promote immune reconstitution.

Graft-versus-leukemia (GVL) against mouse blast-crisis chronic myelogenous leukemia (BC-CML) and chronic-phase chronic myelogenous leukemia (CP-CML): shared mechanisms of T cell killing, but programmed death ligands render CP-CML and not BC-CML GVL resistant.

Graft-versus-leukemia (GVL) against chronic-phase chronic myelogenous leukemia (CP-CML) is potent, but it is less efficacious against acute leukemias and blast-crisis chronic myelogenous leukemia (BC-CML). The mechanisms underlying GVL resistance are unknown. Previously, we found that alloreactive T cell targeting of GVL-sensitive bcr-abl-induced mouse CP-CML (mCP-CML) required TCR-MHC interactions and that multiple and redundant killing mechanisms were in play.

Graft-versus-host disease is independent of innate signaling pathways triggered by pathogens in host hematopoietic cells.

Graft-versus-host disease (GVHD) is initiated by APCs that prime alloreactive donor T cells. In antipathogen responses, Ag-bearing APCs receive signals through pattern-recognition receptors, including TLRs, which induce the expression of costimulatory molecules and production of inflammatory cytokines, which in turn mold the adaptive T cell response. However, in allogeneic hematopoietic stem cell transplantation (alloSCT), there is no specific pathogen, alloantigen is ubiquitous, and signals that induce APC maturation are undefined.

Langerhans cells are not required for graft-versus-host disease.

Graft-versus-host disease (GVHD) is initiated and maintained by antigen-presenting cells (APCs) that prime alloreactive donor T cells. APCs are therefore attractive targets for GVHD prevention and treatment. APCs are diverse in phenotype and function, making understanding how APC subsets contribute to GVHD necessary for the development of APC-targeted therapies.

Recipient B cells are not required for graft-versus-host disease induction.

Recipient antigen presenting cells (APCs) are required for CD8-mediated graft-versus-host disease (GVHD), and have an important and nonredundant role in CD4-mediated GVHD in mouse major histocompatibility complex-matched allogeneic bone marrow transplantation (alloBMT). However, the precise roles of specific recipient APCs-dendritic cells, macrophages, and B cells-are not well defined. If recipient B cells are important APCs they could be depleted with rituximab, an anti-CD20 monoclonal antibody.

Central memory CD8+ T cells induce graft-versus-host disease and mediate graft-versus-leukemia.

In allogeneic hemopoietic stem cell transplantation, mature donor alphabeta T cells in the allograft promote T cell reconstitution in the recipient and mediate the graft-vs-leukemia (GVL) effect. Unfortunately, donor T cells can attack nonmalignant host tissues and cause graft-vs-host disease (GVHD). It has previously been shown that effector memory T cells not primed to alloantigen do not cause GVHD yet transfer functional T cell memory and mediate GVL.

MyD88-dependent, superoxide-initiated inflammation is necessary for flow-mediated inward remodeling of conduit arteries.

Vascular remodeling normalizes abnormal hemodynamic stresses through structural changes affecting vessel size and wall thickness. We investigated the role of inflammation in flow-mediated vascular remodeling using a murine model of partial outflow reduction without flow cessation or neointima formation. Common carotid arteries decreased in size after ipsilateral external carotid artery ligation in wild-type mice, but not in myeloid differentiation protein-88 (MyD88)-deficient mice.

Characterization of a novel gain of function glucocorticoid receptor knock-in mouse.

Glucocorticoids (GCs) exert profound influences on many physiologic functions by virtue of their diverse roles in growth, development, and maintenance of homeostasis. We previously created a novel gain of function in the human glucocorticoid receptor (hGR), hGRM604L, which is active at GC concentrations 5-10-fold lower than wild-type GR. To gain a greater insight into GC physiology in vivo, we inserted this mutant GR (GRM610L in mice) into mice via homologous recombination.

CD8+ but not CD4+ T cells require cognate interactions with target tissues to mediate GVHD across only minor H antigens, whereas both CD4+ and CD8+ T cells require direct leukemic contact to mediate GVL.

Whether T-cell antigen receptors (TCR) on donor T cells require direct interactions with major histocompatibility complex class I or class II (MHCI/MHCII) molecules on target cells to mediate graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) is a fundamental question in allogeneic stem-cell transplantation (alloSCT). In MHC-mismatched mouse models, these contacts were not required for GVHD. However, this conclusion may not apply to MHC-matched, multiple minor histocompatibility antigen-mismatched alloSCT, the most common type performed clinically.

Effector memory CD4+ T cells mediate graft-versus-leukemia without inducing graft-versus-host disease.

Much of the efficacy of allogeneic hematopoietic stem cell transplantation (alloSCT) in curing hematologic malignancies is due to a graft-versus-leukemia (GVL) effect mediated by donor T cells that recognize recipient alloantigens on leukemic cells. Donor T cells are also important for reconstituting immunity in the recipient. Unfortunately, donor T cells can attack nonmalignant host tissues and cause graft-versus-host disease (GVHD).