An immunohistochemical atlas of necroptotic pathway expression.

Necroptosis is a lytic form of regulated cell death reported to contribute to inflammatory diseases of the gut, skin and lung, as well as ischemic-reperfusion injuries of the kidney, heart and brain. However, precise identification of the cells and tissues that undergo necroptotic cell death in vivo has proven challenging in the absence of robust protocols for immunohistochemical detection. Here, we provide automated immunohistochemistry protocols to detect core necroptosis regulators - Caspase-8, RIPK1, RIPK3 and MLKL - in formalin-fixed mouse and human tissues. We observed surprising heterogeneity in protein expression within tissues, whereby short-lived immune barrier cells were replete with necroptotic effectors, whereas long-lived cells lacked RIPK3 or MLKL expression. Local changes in the expression of necroptotic effectors occurred in response to insults such as inflammation, dysbiosis or immune challenge, consistent with necroptosis being dysregulated in disease contexts. These methods will facilitate the precise localisation and evaluation of necroptotic signaling in vivo.

Hypomorphic and dominant-negative impact of truncated SOX9 dysregulates Hedgehog-Wnt signaling, causing campomelia.

Haploinsufficiency for SOX9, the master chondrogenesis transcription factor, can underlie campomelic dysplasia (CD), an autosomal dominant skeletal malformation syndrome, because heterozygous Sox9 null mice recapitulate the bent limb (campomelia) and some other phenotypes associated with CD. However, in vitro cell assays suggest haploinsufficiency may not apply for certain mutations, notably those that truncate the protein, but in these cases in vivo evidence is lacking and underlying mechanisms are unknown. Here, using conditional mouse mutants, we compared the impact of a heterozygous Sox9 null mutation (Sox9+/-) with the Sox9+/Y440X CD mutation that truncates the C-terminal transactivation domain but spares the DNA-binding domain. While some Sox9+/Y440X mice survived, all Sox9+/- mice died perinatally. However, the skeletal defects were more severe and IHH signaling in developing limb cartilage was significantly enhanced in Sox9+/Y440X compared with Sox9+/-. Activating Sox9Y440X specifically in the chondrocyte-osteoblast lineage caused milder campomelia, and revealed cell- and noncell autonomous mechanisms acting on chondrocyte differentiation and osteogenesis in the perichondrium. Transcriptome analyses of developing Sox9+/Y440X limbs revealed dysregulated expression of genes for the extracellular matrix, as well as changes consistent with aberrant WNT and HH signaling. SOX9Y440X failed to interact with ß-catenin and was unable to suppress transactivation of Ihh in cell-based assays. We propose enhanced HH signaling in the adjacent perichondrium induces asymmetrically localized excessive perichondrial osteogenesis resulting in campomelia. Our study implicates combined haploinsufficiency/hypomorphic and dominant-negative actions of SOX9Y440X, cell-autonomous and noncell autonomous mechanisms, and dysregulated WNT and HH signaling, as the cause of human campomelia.

Mammary tumour cells remodel the bone marrow vascular microenvironment to support metastasis.

Bone marrow is a preferred metastatic site for multiple solid tumours and is associated with poor prognosis and significant morbidity. Accumulating evidence indicates that cancer cells colonise specialised niches within the bone marrow to support their long-term propagation, but the precise location and mechanisms that mediate niche interactions are unknown. Using breast cancer as a model of solid tumour metastasis to the bone marrow, we applied large-scale quantitative three-dimensional imaging to characterise temporal changes in the bone marrow microenvironment during disease progression. We show that mouse mammary tumour cells preferentially home to a pre-existing metaphyseal domain enriched for type H vessels. Metastatic lesion outgrowth rapidly remodelled the local vasculature through extensive sprouting to establish a tumour-supportive microenvironment. The evolution of this tumour microenvironment reflects direct remodelling of the vascular endothelium through tumour-derived granulocyte-colony stimulating factor (G-CSF) in a hematopoietic cell-independent manner. Therapeutic targeting of the metastatic niche by blocking G-CSF receptor inhibited pathological blood vessel remodelling and reduced bone metastasis burden. These findings elucidate a mechanism of 'host' microenvironment hijacking by mammary tumour cells to subvert the local microvasculature to form a specialised, pro-tumorigenic niche.

Terminal ileum is the most sensitive site for the histologic diagnosis of grade 4 graft-versus-host disease (GvHD) in the lower GI tract and is a harbinger of poor outcome.

The site of the gastrointestinal (GI) tract where biopsies are most likely to be diagnostic of graft-versus-host disease (GvHD) remains controversial. Recent reports have indicated that biopsies from the rectosigmoid have sufficient sensitivity and specificity for diagnosing GI GvHD and can be obtained via a less invasive flexible sigmoidoscopy procedure. While GvHD histologic grades 1-3 have little correlation with patients' symptoms and overall clinical grade, histologic grade 4 GvHD does correlate with severe clinical presentation and a poor prognosis. We examined cases of lower GI biopsies obtained via a complete colonoscopy with ileal intubation for the evaluation of GvHD within a 2-year period from patients who underwent stem cell transplantation. In our study cohort, grade 4 GvHD was significantly more likely to be identified in a terminal ileum biopsy than in a biopsy from another site in the lower GI tract. Significantly, 5 of 6 patients with histologic grade 4 GvHD diagnosed on ileal biopsies died from complication of severe GI GvHD. Given the poor prognosis of histologic grade 4 GvHD in the terminal ileum, the detection of this finding may serve to inform clinicians that escalation or modification of treatment may need to be considered. Furthermore, our findings suggest that terminal ileal biopsies may help to increase sensitivity for identifying patients at high risk for poor outcome of GvHD.

Topography, morphology, and etiology of lymphocytic gastritis: a single institution experience.

Lymphocytic gastritis (LG) is an uncommon reaction pattern of gastric injury characterized by intraepithelial lymphocytosis of the surface foveolar epithelium and chronic inflammation in the lamina propria. It most commonly occurs in association with gluten-sensitive enteropathy, Helicobacter pylori gastritis, non-steroidal anti-inflammatory drugs, and microscopic colitis. While the topography of LG has been described in gluten-sensitive enteropathy and H. pylori infection, no definite morphologic features have been used to further subcategorize LG based on possible etiologies. Furthermore, new immunotherapy agents have been associated with lymphocytic infiltrate in the gastrointestinal tract, but their association with LG has not been reported. Cases of LG were collected from our institution in the period between August 2011 and September 2017. The topography of LG and morphologic features such as glandular microabscesses, intestinal metaplasia, lymphoid aggregates, surface vs pit distribution of lymphocytes, and number of intraepithelial lymphocytes per 100 epithelial cells were assessed for each case using the updated Sydney System where applicable. Twenty-seven cases of LG were identified in the recent 6-year period at our institution. Gluten-sensitive enteropathy is the main reported cause of LG followed by NSAID injury. Cases of LG associated with gluten-sensitive enteropathy are antral predominant, those associated with H. pylori are body predominant, and those occurring in the setting of NSAID injury show pangastritis. Glandular microabscesses are observed in all cases of LG associated with H. pylori, and not in the setting of GSE or NSAID injury. In addition, a case of LG associated with melanoma immunotherapy has been identified. Topography and morphology of lymphocytic gastritis may point to the cause of injury, allowing for proper treatment of the underlying disease.

Mechanistic insights into skeletal development gained from genetic disorders.

A complex cascade of highly regulated processes of cell fate determination, differentiation, proliferation and transdifferentiation dictate the patterning, morphogenesis and growth of the vertebrate skeleton, perturbation of which results in malformation. In humans over 450 different dysplasias involving the skeletal system constitute a significant fraction of documented Mendelian disorders. The combination of clinical, phenotypic characterization of rare human skeletal dysmorphologies, the discovery of causative mutations and functional validation in animal models has contributed enormously to the understanding of molecular control of skeletal development. These studies revealed a myriad of genes and pathways, such as WNT, Hedgehog (HH), planar cell polarity and primary cilia, as key regulators for skeletal patterning, growth and homeostasis. The generation of mouse models recapitulating human congenital skeletal dysplasia has provided mechanistic insights into the diverse pathologies caused by single gene mutations, integrated action of developmental pathways such as WNT and HH and the role of stress responses. Technological developments in whole genome and exome sequencing have accelerated the discovery of disease-causing mutations and are changing approaches for diagnosis. The discovery that non-coding variants and disorganization of the 3D genome are associated with limb patterning disorders has revealed an additional level of complexity in the regulatory framework of skeletal development and disease mechanisms. This chapter focuses on a selection of human skeletal pathologies which illustrate how new findings about the coding and noncoding genome, combined with functional modeling, are contributing to deeper understanding of skeletal development, mechanisms of disease, with therapeutic potential for chondrodysplasias.

Lymphocytic gastritis induced by pembrolizumab in a patient with metastatic melanoma.

Immune checkpoint inhibitors such as programmed cell death-1 inhibitor pembrolizumab have been shown to be effective in metastatic malignancies such as advanced melanoma. Immune-related adverse effects on multiple organs have been described, such as colitis, skin rash, and hypothyroidism. We present the case of a 44-year-old man with advanced melanoma and recurrent lung metastases who developed symptoms of dyspepsia and gastroesophageal reflux disease after 1 month of therapy with pembrolizumab. Gastric biopsy showed histologic features consistent with lymphocytic gastritis, which was absent on a biopsy 2 months before initiation of therapy. Lymphocytic infiltrates likely secondary to increased autoimmunity after use of immunotherapy have been observed in the colon; however, such histologic findings in the upper gastrointestinal tract have yet to be described. Here, we present a case of lymphocytic gastritis in a patient treated with pembrolizumab, suggesting a new manifestation of toxicity.

Cation and voltage dependence of lidocaine inhibition of the hyperpolarization-activated cyclic nucleotide-gated HCN1 channel.

Lidocaine is known to inhibit the hyperpolarization-activated mixed cation current (Ih) in cardiac myocytes and neurons, as well in cells transfected with cloned Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels. However, the molecular mechanism of Ih inhibition by this drug has been limitedly explored. Here, we show that inhibition of Ih by lidocaine, recorded from Chinese hamster ovary (CHO) cells expressing the HCN1 channel, reached a steady state within one minute and was reversible. Lidocaine inhibition of Ih was greater at less negative voltages and smaller current amplitudes whereas the voltage-dependence of Ih activation was unchanged. Lidocaine inhibition of Ih measured at -130 mV (a voltage at which Ih is fully activated) was reduced, and Ih amplitude was increased, when the concentration of extracellular potassium was raised to 60 mM from 5.4 mM. By contrast, neither Ih inhibition by the drug nor Ih amplitude at +30 mV (following a test voltage-pulse to -130 mV) were affected by this rise in extracellular potassium. Together, these data indicate that lidocaine inhibition of Ih involves a mechanism which is antagonized by hyperpolarizing voltages and current flow.

Chromatin remodeling, DNA damage repair and aging.

Cells are constantly exposed to a variety of environmental and endogenous conditions causing DNA damage, which is detected and repaired by conserved DNA repair pathways to maintain genomic integrity. Chromatin remodeling is critical in this process, as the organization of eukaryotic DNA into compact chromatin presents a natural barrier to all DNA-related events. Studies on human premature aging syndromes together with normal aging have suggested that accumulated damages might lead to exhaustion of resources that are required for physiological functions and thus accelerate aging. In this manuscript, combining the present understandings and latest findings, we focus mainly on discussing the role of chromatin remodeling in the repair of DNA double-strand breaks (DSBs) and regulation of aging.