The Hippo-YAP Signaling as Guardian in the Pool of Intestinal Stem Cells

Ion Transport Basis of Diarrhea, Paneth Cell Metaplasia, and Upregulation of Mechanosensory Pathway in Anti-CD40 Colitis Mice

BACKGROUND

Anti-Cluster of differentiation (CD)-40-induced colitis, driven by innate inflammatory responses in the intestine, is a potent animal model exhibiting IBD pathophysiology including diarrhea. However, the ion transport basis of diarrhea and some key mucosal pathways (Paneth cells, stem cell niche, and mechanosensory) in this model have not been investigated.

METHODS

Mucosal scrapings and intestinal tissue from control and CD40 antibody (150 µg) treated Rag2-/- mice were examined for gut inflammation, Paneth cell numbers, expression of key transporters, tight/adherens junction proteins, stem cell niche, and mechanosensory pathway via hematoxylin and eosin staining, quantitative polymerase chain reaction, and western blotting.

RESULTS

Compared with control, anti-CD40 antibody treatment resulted in a significant loss of body weight (P < .05) and diarrhea at day 3 postinjection. Distal colonic tissues of anti-CD40 mice exhibited increased inflammatory infiltrates, higher claudin-2 expression, and appearance of Paneth cell-like structures indicative of Paneth cell metaplasia. Significantly reduced expression (P < .005) of downregulated in adenoma (key Cl- transporter), P-glycoprotein/multidrug resistantance-1 (MDR1, xenobiotic transporter), and adherens junction protein E-cadherin (~2-fold P < .05) was also observed in the colon of anti-CD40 colitis mice. Interestingly, there were also marked alterations in the stem cell markers and upregulation of the mechanosensory YAP-TAZ pathway, suggesting the activation of alternate regeneration pathway post-tissue injury in this model.

CONCLUSION

Our data demonstrate that the anti-CD40 colitis model shows key features of IBD observed in the human disease, hence making it a suitable model to investigate the pathophysiology of ulcerative colitis (UC).

GPR137 inactivates Hippo signaling to promote gastric cancer cell malignancy

As the fifth most common cancer in the world, gastric cancer (GC) ranks as the third major cause of cancer-related death globally. Although surgical resection and chemotherapy still remains the mainstay of potentially curative treatment for GC, chemotherapy resistance and adverse side effects limit their clinical applications. Thus, further investigation of the mechanisms of carcinogenesis in GC and discovery of novel biomarkers is of great concern. We herein report that the elevated expression of GPR137 is correlated with GC. Overexpression of GPR137 potentiates human gastric cancer AGS cell malignancy, including proliferation, migration, invasion, colony formation and xenograft growth in nude mice in vivo, whereas knockout of GPR137 by CRISPR/Cas9 gene editing exerts the opposite effects. Mechanistically, GPR137 could bind to MST, the upstream kinases in Hippo pathway, which disrupts the association of MST with LATS, subsequently activating the transcriptional co-activators, YAP and TAZ, and thereby triggering the target transcription and the alterations in GC cell biological actions consequently. Therefore, our findings may provide with the evidence of developing a potentially novel treatment method with specific target for GC.

CRISPR-cas9 screening identified lethal genes enriched in Hippo kinase pathway and of predictive significance in primary low-grade glioma

BACKGROUND

Low-grade gliomas (LGG) are a type of brain tumor that can be lethal, and it is essential to identify genes that are correlated with patient prognosis. In this study, we aimed to use CRISPR-cas9 screening data to identify key signaling pathways and develop a genetic signature associated with high-risk, low-grade glioma patients.

METHODS

The study used CRISPR-cas9 screening data to identify essential genes correlated with cell survival in LGG. We used RNA-seq data to identify differentially expressed genes (DEGs) related to cell viability. Moreover, we used the least absolute shrinkage and selection operator (LASSO) method to construct a genetic signature for predicting overall survival in patients. We performed enrichment analysis to identify pathways mediated by DEGs, overlapping genes, and genes shared in the Weighted correlation network analysis (WGCNA). Finally, the study used western blot, qRT-PCR, and IHC to detect the expression of hub genes from signature in clinical samples.

RESULTS

The study identified 145 overexpressed oncogenes in low-grade gliomas using the TCGA database. These genes were intersected with lethal genes identified in the CRISPR-cas9 screening data from Depmap database, which are enriched in Hippo pathways. A total of 19 genes were used to construct a genetic signature, and the Hippo signaling pathway was found to be the predominantly enriched pathway. The signature effectively distinguished between low- and high-risk patients, with high-risk patients showing a shorter overall survival duration. Differences in hub gene expression were found in different clinical samples, with the protein and mRNA expression of REP65 being significantly up-regulated in tumor cells. The study suggests that the Hippo signaling pathway may be a critical regulator of viability and tumor proliferation and therefore is an innovative new target for treating cancerous brain tumors, including low-grade gliomas.

CONCLUSION

Our study identified a novel genetic signature associated with high-risk, LGG patients. We found that the Hippo signaling pathway was significantly enriched in this signature, indicating that it may be a critical regulator of tumor viability and proliferation in LGG. Targeting the Hippo pathway could be an innovative new strategy for treating LGG.

Potential Effect of Glutamine in the Improvement of Intestinal Stem Cell Proliferation and the Alleviation of Burn-Induced Intestinal Injury via Activating YAP: A Preliminary Study

Burn injury is a common form of traumatic injury that leads to high mortality worldwide. A severe burn injury usually induces gut barrier dysfunction, partially resulting from the impairment in the proliferation and self-renewal of intestinal stem cells (ISCs) post burns. As a main energy substance of small intestinal enterocytes, glutamine (Gln) is important for intestinal cell viability and growth, while its roles in ISCs-induced regeneration after burns are still unclear. To demonstrate the potential effects of Gln in improving ISCs proliferation and alleviating burn-induced intestinal injury, in this study, we verified that Gln significantly alleviated small intestine injury in burned mice model. It showed that Gln could significantly decrease the ferroptosis of crypt cells in the ileum, promote the proliferation of ISCs, and repair the crypt. These effects of Gln were also confirmed in the mouse small intestine organoids model. Further research found that Yes-associated protein (YAP) is suppressed after burn injury, and Gln could improve cell proliferation and accelerate the renewal of the damaged intestinal mucosal barrier after burns by activating YAP. YAP is closely associated with the changes in intestinal stem cell proliferation after burn injury and could be served as a potential target for severe burns.

Treatment of ulcerative colitis with Wu-Mei-Wan by inhibiting intestinal inflammatory response and repairing damaged intestinal mucosa

BACKGROUND

Wu-Mei-Wan (WMW), a traditional Chinese medicine, has been applied in the treatment of gastrointestinal diseases with long-term diarrhea and mucopurulent bloody stool as the main symptoms since ancient times. Studies have shown that WMW inhibits intestinal inflammation, repairs damaged intestinal mucosa, resists colon necrosis, and resists intestinal fibrosis. However, the specific mechanism of action is not yet clear.

OBJECTIVE

Ulcerative colitis (UC), an intestinal disease with intestinal inflammation and injury as the main pathological manifestations, is one of the high-risk factors for colon cancer. Inhibiting the inflammatory response and promoting colonic epithelial repair are critical to the treatment of UC. However, there is still a lack of remedies with satisfactory curative effects. In this study, the role of WMW in dextran sulfate sodium (DSS)-induced colitis in mice and its related mechanisms are discussed from two aspects: intestinal inflammation and tissue repair.

METHODS

DSS was used to induce colitis in mice and the therapeutic effect of WMW was analyzed by disease activity score, histopathological score, colon length measurement, serum cytokine detection, and flow cytometry. Macrophage activation and colonic stem cell proliferation were observed by immunohistochemistry. The expression of critical molecules in macrophage activation and colonic stem cell proliferation signaling pathways in colon tissue was detected with immunohistochemistry, immunofluorescence staining, RT-qPCR, and Western blot.

RESULTS

WMW could significantly alleviate DSS-induced colitis. We showed that WMW could reduce disease activity, reduce pathological scores, limit weight loss, inhibit colon shortening, inhibit inflammatory factor secretion, attenuate inflammatory response, and promote the repair of damaged colonic epithelium. WMW inhibited the activation of colonic macrophages, and its mechanism might be inhibiting the Notch/NF-κB/NLRP3 pathway; WMW promoted the proliferation of colonic stem cells, and its mechanism was associated with the regulation of the Hippo/YAP signaling pathway.

CONCLUSION

The results of this study suggested that WMW could treat UC via a mechanism that inhibited the intestinal inflammatory response and repaired damaged intestinal mucosa.

Regulation of homeostasis and regeneration in the adult intestinal epithelium by the TGF-β superfamily

The delicate balance between the homeostatic maintenance and regenerative capacity of the intestine makes this a fascinating tissue of study. The intestinal epithelium undergoes continuous homeostatic renewal but is also exposed to a diverse array of stresses that can range from physiological processes such as digestion, to exposure to infectious agents, drugs, radiation therapy, and inflammatory stimuli. The intestinal epithelium has thus evolved to efficiently maintain and reinstate proper barrier function that is essential for intestinal integrity and function. Factors governing homeostatic epithelial turnover are well described, however, the dynamic regenerative mechanisms that occur following injury are the subject of intense ongoing investigations. The TGF-β superfamily is a key regulator of both homeostatic renewal and regenerative processes of the intestine. Here we review the roles of TGF-β and BMP on the adult intestinal epithelium during self-renewal and injury to provide a framework for understanding how this major family of morphogens can tip the scale between intestinal health and disease. This article is protected by copyright. All rights reserved.

An in vitro chronic damage model impairs inflammatory and regenerative responses in human colonoid monolayers

Acute damage to the intestinal epithelium can be repaired via de-differentiation of mature intestinal epithelial cells (IECs) to a stem-like state, but there is a lack of knowledge on how intestinal stem cells function after chronic injury, such as in inflammatory bowel disease (IBD). We developed a chronic-injury model in human colonoid monolayers by repeated rounds of air-liquid interface and submerged culture. We use this model to understand how chronic intestinal damage affects the ability of IECs to (1) respond to microbial stimulation, using the Toll-like receptor 5 (TLR5) agonist FliC and (2) regenerate and protect the epithelium from further damage. Repeated rounds of damage impair the ability of IECs to regrow and respond to TLR stimulation. We also identify mRNA expression and DNA methylation changes in genes associated with IBD and colon cancer. This methodology results in a human model of recurrent IEC injury like that which occurs in IBD.

The hippo pathway orchestrates cytoskeletal organisation during intervertebral disc degeneration

Yes-associated protein (YAP) activity responded to physical and mechanical cues such as extracellular matrix (ECM), cell density and the mechanical regulation of YAP controlled cellular proliferation and inhibition of apoptotic signals. The intervertebral disc (IVD) comprises a heterogeneous population of cells, including those of the nucleus pulposus (NP) and annulus fibrosus (AF), which are diverse in phenotype, partly due to the different ECM and mechanical loads they experience. How do IVD cells sense microenvironment and what is the relationship between YAP and cytoskeleton in the process of intervertebral disc degeneration (IDD) are not well understood. First, Hippo pathway and cytoskeleton organisation were assessed in the NP and AF of immature (4 weeks), mature (14 weeks), aged (50 weeks), and degenerated (14 weeks, 4 weeks after annulus puncture) IVDs. Second, to assess the effect of ECM composition and cell density on cytoskeleton and YAP levels, we seeded cells at different densities on three types of ECM. In this study, YAP and F-actin activity decreased gradually with age in natural IDD. Hippo signalling was suppressed in the early stages of disc injury, demonstrating the potential for endogenous repair, but this repair did not prevent further disc degeneration. β-tubulin and vimentin filaments provide the cell with its shape and its elastic properties in resisting mechanical forces. The Hippo pathway and cytoskeleton were shown to be regulated by cell density and the ECM composition.