Probes for INS

Hemodynamic forces play an essential epigenetic role in heart valve development, but how they do so is not known. Here, we show that the shear-responsive transcription factor KLF2 is required in endocardial cells to regulate the mesenchymal cell responses that remodel cardiac cushions to mature valves. Endocardial Klf2 deficiency results in defective valve formation associated with loss of Wnt9b expression and reduced canonical WNT signaling in neighboring mesenchymal cells, a phenotype reproduced by endocardial-specific loss of Wnt9b. Studies in zebrafish embryos reveal that wnt9b expression is similarly restricted to the endocardial cells overlying the developing heart valves and is dependent upon both hemodynamic shear forces and klf2a expression. These studies identify KLF2-WNT9B signaling as a conserved molecular mechanism by which fluid forces sensed by endothelial cells direct the complex cellular process of heart valve development and suggest that congenital valve defects may arise due to subtle defects in this mechanotransduction pathway.

Recently three different cyclin-dependent kinase 4 and 6 (CDK4/6) dual inhibitors were approved for the treatment of breast cancer (palbociclib, ribociclib and abemaciclib), all of which offer comparable therapeutic benefits. Their safety profiles however are different. For example, neutropenia is observed at varying incidences in patients treated with these drugs; however it is the most common adverse event for palbociclib and ribociclib, whereas diarrhea is the most common adverse event observed in patients treated with abemaciclib. In order to understand the mechanism of diarrhea observed with these drugs and in an effort to guide the development of safer drugs, we compared the effects of oral administration of palbociclib, ribociclib and abemaciclib on the gastrointestinal tract of rats using doses intended to produce comparable CDK4/6 inhibition. Rats administered abemaciclib, but not palbociclib or ribociclib, had fecal alterations, unique histopathological findings and distinctive changes in intestinal gene expression. Morphologic changes in the intestine were characterized by proliferation of crypt cells, loss of goblet cells, poorly differentiated and degenerating enterocytes with loss of microvilli and mucosal inflammation. In the jejunum of abemaciclib-treated rats, down-regulation of enterocyte membrane transporters and up-regulation of genes associated with cell proliferation were observed, consistent with activation of the Wnt pathway and downstream transcriptional regulation. Among these CDK4/6 inhibitors, intestinal toxicity was unique to rats treated with abemaciclib, suggesting a mechanism of toxicity not due to primary pharmacology (CDK4/6 inhibition), but to activity at secondary pharmacological targets.

Postnatal liver development is characterized by hepatocyte growth, proliferation and functional maturation. Notably, canonical Wnt signaling in hepatocytes has been identified as an important regulator of final adult liver size and metabolic liver zonation. The cellular origin of Wnt ligands responsible for homeostatic liver/body weight ratio remained unclear, which was also attributable to a lack of suitable endothelial Cre driver mice. To comprehensively analyze the effects of hepatic angiocrine Wnt signaling on liver development and metabolic functions, we used endothelial subtype-specific Stab2-Cre driver mice to delete Wls from hepatic endothelial cells (HEC). The resultant Stab2-Cretg/wt;Wlsfl/fl (Wls-HECKO) mice were viable but showed a significantly reduced liver/body weight ratio. Specifically, ablation of angiocrine Wnt signaling impaired metabolic zonation in the liver, as shown by loss of pericentral, β-catenin-dependent target genes such as Glutamine Synthase (Glul), RhBg, Axin2 and CYP2E1 as well as by extended expression of periportal genes such as Arginase 1 (Arg1). Furthermore, endothelial subtype-specific expression of a c-terminally YFP-tagged Wls fusion protein in Wls-HECKO mice (Stab2-Cretg/wt ;Wlsfl/fl;Rosa26:Wls-YFPfl/wt [Wls-rescue]) restored metabolic liver zonation. Interestingly, lipid metabolism was altered in Wls-HECKO miceexhibiting significantly reduced plasma cholesterol levels, while maintaining normal plasma triglyceride and blood glucose concentrations. On the contrary, zonal expression of Endomucin, LYVE1 and other markers of HEC heterogeneity were not altered in Wls-HECKO livers.

In the healthy adult liver, most hepatocytes proliferate minimally. However, upon physical or chemical injury to the liver, hepatocytes proliferate extensively in vivo under the direction of multiple extracellular cues, including Wnt and pro-inflammatory signals. Currently, liver organoids can be generated readily in vitro from bile-duct epithelial cells, but not hepatocytes. Here, we show that TNFα, an injury-induced inflammatory cytokine, promotes the expansion of hepatocytes in 3D culture and enables serial passaging and long-term culture for more than 6 months. Single-cell RNA sequencing reveals broad expression of hepatocyte markers. Strikingly, in vitro-expanded hepatocytes engrafted, and significantly repopulated, the injured livers of Fah −/− mice. We anticipate that tissue repair signals can be harnessed to promote the expansion of otherwise hard-to-culture cell-types, with broad implications.

Hair growth disorders often carry a major psychological burden. Therefore, more effective human hair growth-modulatory agents urgently need to be developed. Here, we used the hypertrichosis-inducing immunosuppressant, Cyclosporine A (CsA), as a lead compound to identify new hair growth-promoting molecular targets. Through microarray analysis we identified the Wnt inhibitor, secreted frizzled related protein 1 (SFRP1), as being down-regulated in the dermal papilla (DP) of CsA-treated human scalp hair follicles (HFs) ex vivo. Therefore, we further investigated the function of SFRP1 using a pharmacological approach and found that SFRP1 regulates intrafollicular canonical Wnt/β-catenin activity through inhibition of Wnt ligands in the human hair bulb. Conversely, inhibiting SFRP1 activity through the SFRP1 antagonist, WAY-316606, enhanced hair shaft production, hair shaft keratin expression, and inhibited spontaneous HF regression (catagen) ex vivo. Collectively, these data (a) identify Wnt signalling as a novel, non-immune-inhibitory CsA target; (b) introduce SFRP1 as a physiologically important regulator of canonical β-catenin activity in a human (mini-)organ; and (c) demonstrate WAY-316606 to be a promising new promoter of human hair growth. Since inhibiting SFRP1 only facilitates Wnt signalling through ligands that are already present, this 'ligand-limited' therapeutic strategy for promoting human hair growth may circumvent potential oncological risks associated with chronic Wnt over-activation.

In humans, the endometrium, the uterine mucosal lining, undergoes dynamic changes throughout the menstrual cycle and pregnancy. Despite the importance of the endometrium as the site of implantation and nutritional support for the conceptus, there are no long-term culture systems that recapitulate endometrial function in vitro. We adapted conditions used to establish human adult stem-cell-derived organoid cultures to generate three-dimensional cultures of normal and decidualized human endometrium. These organoids expand long-term, are genetically stable and differentiate following treatment with reproductive hormones. Single cells from both endometrium and decidua can generate a fully functional organoid. Transcript analysis confirmed great similarity between organoids and the primary tissue of origin. On exposure to pregnancy signals, endometrial organoids develop characteristics of early pregnancy. We also derived organoids from malignant endometrium, and so provide a foundation to study common diseases, such as endometriosis and endometrial cancer, as well as the physiology of early gestation.

Alveoli, the lung's respiratory units, are tiny sacs where oxygen enters the bloodstream. They are lined by flat AT1 cells, which mediate gas exchange, and AT2 cells, which secret surfactant. Rare AT2s also function as alveolar stem cells. We show that AT2 lung stem cells display active Wnt signaling and many of them are near single, Wnt-expressing fibroblasts. Blocking Wnt secretion depletes these stem cells. Daughter cells leaving the Wnt niche transdifferentiate into AT1s: maintaining Wnt signaling prevents transdifferentiation whereas abrogating Wnt signaling promotes it. Injury induces AT2 autocrine Wnts, recruiting 'bulk' AT2s as progenitors. Thus, individual AT2 stem cells reside in single cell fibroblast niches providing juxtacrine Wnts that maintain them, whereas injury induces autocrine Wnts that transiently expand the progenitor pool. This simple niche maintains the gas exchange surface, and is coopted in cancer.