Lysophosphatidic acid induces YAP-promoted proliferation of human corneal endothelial cells via PI3K and ROCK pathways

Corneal Endothelial Morphology and Ocular Biometric Indexes in Premature Children With and Without Retinopathy of Prematurity

Purpose

The purpose of this study was to analyze human corneal endothelial cells (HCECs) morphology and ocular biometrics in premature (PM) children with or without retinopathy of prematurity (ROP).

Methods

Retrospective data on patient demographics, HCECs status, and ocular biometrics with at least 2 visits between 2016 and 2021 were reviewed. The main outcomes were endothelial cell density (ECD), coefficient of variation (CV), hexagonal cell ratio (HEX), central corneal thickness (CCT), axial length, anterior chamber depth, keratometry, corneal diameter, pupil diameter, and refraction status. Generalized estimating equation was used to evaluate the differences between PM no-ROP and ROP groups. We also analyzed the trend of ECD, CV, HEX, and CCT change with age between groups.

Results

The study included 173 PM patients without ROP and 139 patients with ROP. A total of 666 and 544 measurements were recorded in the PM no-ROP and ROP groups, respectively. The ROP group had higher spherical power, myopic spherical equivalent (SE), and steeper steep keratometry (K; P < 0.05). The ROP group had higher CV (P = 0.0144), lower HEX (P = 0.0012) and thicker CCT (P = 0.0035). In the HCECs parameters, the ROP group had slower ECD decrement (P < 0.0001), faster CV decrement (P = 0.0060), and faster HEX increment (P = 0.0001). A difference in corneal morphology changes between the ROP and PM no-ROP groups were prominent in patients with lower gestational age (GA) in the subgroup analysis.

Conclusions

Worse HCECs morphology and higher myopic status were initially observed in patients with prior ROP but not in PM patients with no-ROP. ECD and HCECs morphology improved with age, especially in patients with low GA.

Squishy matters - Corneal mechanobiology in health and disease

The cornea, as a dynamic and responsive tissue, constantly interacts with mechanical forces in order to maintain its structural integrity, barrier function, transparency and refractive power. Cells within the cornea sense and respond to various mechanical forces that fundamentally regulate their morphology and fate in development, homeostasis and pathophysiology. Corneal cells also dynamically regulate their extracellular matrix (ECM) with ensuing cell-ECM crosstalk as the matrix serves as a dynamic signaling reservoir providing biophysical and biochemical cues to corneal cells. Here we provide an overview of mechanotransduction signaling pathways then delve into the recent advances in corneal mechanobiology, focusing on the interplay between mechanical forces and responses of the corneal epithelial, stromal, and endothelial cells. We also identify species-specific differences in corneal biomechanics and mechanotransduction to facilitate identification of optimal animal models to study corneal wound healing, disease, and novel therapeutic interventions. Finally, we identify key knowledge gaps and therapeutic opportunities in corneal mechanobiology that are pressing for the research community to address especially pertinent within the domains of limbal stem cell deficiency, keratoconus and Fuchs' endothelial corneal dystrophy. By furthering our understanding corneal mechanobiology, we can contextualize discoveries regarding corneal diseases as well as innovative treatments for them.

Corneal endothelial cells and acoustic cavitation in phacoemulsification

Postoperative complications of phacoemulsification, such as corneal edema caused by human corneal endothelial cell (CEC) injury, are still a matter of concern. Although several factors are known to cause CEC damage, the influence of ultrasound on the formation of free radicals during surgery should be considered. Ultrasound in aqueous humor induces cavitation and promotes the formation of hydroxyl radicals or reactive oxygen species (ROS). ROS-induced apoptosis and autophagy in phacoemulsification have been suggested to significantly promote CEC injury. CEC cannot regenerate after injury, and measures must be taken to prevent the loss of CEC after phacoemulsification or other CEC injuries. Antioxidants can reduce the oxidative stress injury of CEC during phacoemulsification. Evidence from rabbit eye studies shows that ascorbic acid infusion during operation or local application of ascorbic acid during phacoemulsification has a protective effect by scavenging free radicals or reducing oxidative stress. Both in experiments and clinical practice, hydrogen dissolved in the irrigating solution can also prevent CEC damage during phacoemulsification surgery. Astaxanthin (AST) can inhibit oxidative damage, thereby protecting different cells from most pathological conditions, such as myocardial cells, luteinized granulosa cells of the ovary, umbilical vascular endothelial cells, and human retina pigment epithelium cell line (ARPE-19). However, existing research has not focused on the application of AST to prevent oxidative stress during phacoemulsification, and the related mechanisms need to be studied. The Rho related helical coil kinase inhibitor Y-27632 can inhibit CEC apoptosis after phacoemulsification. Rigorous experiments are required to confirm whether its effect is realized through improving the ROS clearance ability of CEC.

Roles of interfacial water states on advanced biomedical material design

When biomedical materials come into contact with body fluids, the first reaction that occurs on the material surface is hydration; proteins are then adsorbed and denatured on the hydrated material surface. The amount and degree of denaturation of adsorbed proteins affect subsequent cell behavior, including cell adhesion, migration, proliferation, and differentiation. Biomolecules are important for understanding the interactions and biological reactions of biomedical materials to elucidate the role of hydration in biomedical materials and their interaction partners. Analysis of the water states of hydrated materials is complicated and remains controversial; however, knowledge about interfacial water is useful for the design and development of advanced biomaterials. Herein, we summarize recent findings on the hydration of synthetic polymers, supramolecular materials, inorganic materials, proteins, and lipid membranes. Furthermore, we present recent advances in our understanding of the classification of interfacial water and advanced polymer biomaterials, based on the intermediate water concept.

RGMa Participates in the Blood-Brain Barrier Dysfunction Through BMP/BMPR/YAP Signaling in Multiple Sclerosis

The infiltration of inflammatory cells into the central nervous system (CNS) through the dysfunctional blood–brain barrier (BBB) was critical in the early stages of MS. However, the mechanisms underlying BBB dysfunction remain unknown. Repulsive guidance molecule-a (RGMa) is involved in the pathogenesis of multiple sclerosis (MS), but its role needs to be further explored. This study aimed to evaluate whether RMGa regulates BBB permeability in endothelial cells and MS, and if so, what mechanism may be involved. We created an experimental autoimmune encephalomyelitis (EAE) model in C57BL/6 mice and a human brain microvascular endothelial cell (HBMEC) culture. The permeability of the BBB is measured in response to various interventions. Our results showed that RGMa is expressed in the endothelial cells in HBMECs and EAE mice. RGMa and its signaling counterpart, bone morphogenetic protein 2 (BMP2)/bone morphogenetic protein receptor type II (BMPRII), were gradually increased as the disease progressed. Moreover, as EAE progressed and the BBB was disrupted, the downstream effector, yes-associated protein (YAP), as well as the tight junctional proteins zonula occludens 1 (ZO-1) and claudin-5, decreased significantly. The permeability assay revealed that lentivirus-induced RGMa overexpression in HBMECs caused a significant breakdown of the BBB, whereas RGMa knockdown significantly strengthens the integrity of the BBB. Furthermore, specifically activating BMPR II or inhibiting YAP based on RGMa knockdown results in a significant decrease of ZO-1 and claudin-5 in vitro. On the contrary, inhibition of BMPR II or activation of YAP after upregulating RGMa prevents the downregulation of ZO-1 and claudin-5 in HBMECs. In addition, serum-soluble RGMa (sRGMa) levels were significantly higher in MS patients, particularly in MS patients with Gd⁺ lesions, indicating that the BBB has been disrupted. In conclusion, this study shows that RGMa causes BBB dysfunction in endothelial cells via BMP2/BMPR II/YAP, resulting in BBB integrity disruption in MS and that it could be a novel therapeutic target for BBB permeability in MS.

CHIR99021 balance TGFβ1 induced human corneal endothelial-to-mesenchymal transition to favor corneal endothelial cell proliferation

Corneal endothelial cells (CECs) play a major role in the maintenance of stromal hydration via the barrier and pump function for clear vision. Adult CEC cannot regenerate after injury. CECs cultured in vitro can undergo mitosis but may undergo corneal endothelial-to-mesenchymal transition (EnMT) and lose their endothelial characteristics. In this study, we examined the effects of CHIR99201 on transforming growth factor beta-1(TGFβ1)-induced EnMT in human CEC (hCECs) lines. CHIR99021 kept hCECs in the hexagonal shape and could downregulate the EnMT markers alpha-smooth muscle actin (α-SMA) and fibronectin (FN1), meanwhile maintained the hCECs function markers Na⁺/K⁺-ATPase and zonula occludens-1 (ZO-1) at levels comparable to those in the normal control. Interestingly, we found that the combination of CHIR99021 and TGFβ1 at appropriate concentrations would significantly promote the proliferation and migration of hCECs. These effects may be related to the inhibition of RhoA or Rac1, as well as the activation of Wnt and Erk pathway, with a calcium homeostasis. Our findings indicate that CHIR99021 inhibit EnMT and that the combination of CHIR99021 and TGFβ1 may provide new ideas for corneal endothelial regeneration and wound healing.

Modulation of Biological Responses of Tumor Cells Adhered to Poly(2-methoxyethyl acrylate) with Increasing Cell Viability under Serum-Free Conditions

Circulating tumor cells in body fluids are important biomarkers in cancer diagnosis. The culture of tumor cells isolated from body fluids can provide intrinsic information about tumors and can be used to screen for the best anticancer drugs. However, the culture of primary tumor cells has been hindered by their low viability and difficulties in recapitulating the phenotype of primary tumors in in vitro culture. The culture of tumor cells under serum-free conditions is one of the methodologies to maintain the phenotype and genotype of primary tumors. Poly(2-methoxyethyl acrylate) (PMEA)-coated substrates have been investigated to prolong the proliferation of tumor cells under serum-free conditions. In this study, we investigated the detailed behavior and the mechanism of the increase in tumor cell viability after adherence to PMEA substrates. The blebbing formation of tumor cells on PMEA was attributed not to apoptosis but to the low adhesion strength of cells on PMEA. Moreover, blebbing tumor cells showed amoeboid movement and formed clusters with other cells via N-cadherin, leading to an increase in tumor cell viability. Furthermore, the behaviors of tumor cells adhered to PMEA under serum-free conditions were involved in the activation of the PI3K and Rho-associated protein kinase pathways. Thus, we propose that PMEA would be suitable for the development of devices to cultivate primary tumor cells under serum-free conditions for the label-free diagnosis of cancer.

Use of biomaterials in corneal endothelial repair

Human corneal endothelium (HCE) is a single layer of hexagonal cells that lines the posterior surface of the cornea. It forms the barrier that separates the aqueous humor from the rest of the corneal layers (stroma and epithelium layer). This layer plays a fundamental role in maintaining the hydration and transparency of the cornea, which in turn ensures a clear vision. In vivo, human corneal endothelial cells (HCECs) are generally believed to be nonproliferating. In many cases, due to their nonproliferative nature, any damage to these cells can lead to further issues with Descemet’s membrane (DM), stroma and epithelium which may ultimately lead to hazy vision and blindness. Endothelial keratoplasties such as Descemet’s stripping automated endothelial keratoplasty (DSAEK) and Descemet’s membrane endothelial keratoplasty (DEK) are the standard surgeries routinely used to restore vision following endothelial failure. Basically, these two similar surgical techniques involve the replacement of the diseased endothelial layer in the center of the cornea by a healthy layer taken from a donor cornea. Globally, eye banks are facing an increased demand to provide corneas that have suitable features for transplantation. Consequently, it can be stated that there is a significant shortage of corneal grafting tissue; for every 70 corneas required, only 1 is available. Nowadays, eye banks face long waiting lists due to shortage of donors, seriously aggravated when compared with previous years, due to the global COVID-19 pandemic. Thus, there is an urgent need to find alternative and more sustainable sources for treating endothelial diseases, such as utilizing bioengineering to use of biomaterials as a remedy. The current review focuses on the use of biomaterials to repair the corneal endothelium. A range of biomaterials have been considered based on their promising results and outstanding features, including previous studies and their key findings in the context of each biomaterial.

The Hippo Signaling Pathway in Cancer: A Cell Cycle Perspective

Simple Summary

Cancer is increasingly viewed as a cell cycle disease in that the dysregulation of the cell cycle machinery is a common feature in cancer. The Hippo signaling pathway consists of a core kinase cascade as well as extended regulators, which together control organ size and tissue homeostasis. The aberrant expression of cell cycle regulators and/or Hippo pathway components contributes to cancer development, and for this reason, we specifically focus on delineating the roles of the Hippo pathway in the cell cycle. Improving our understanding of the Hippo pathway from a cell cycle perspective could be used as a powerful weapon in the cancer battlefield.

Abstract

Cell cycle progression is an elaborate process that requires stringent control for normal cellular function. Defects in cell cycle control, however, contribute to genomic instability and have become a characteristic phenomenon in cancers. Over the years, advancement in the understanding of disrupted cell cycle regulation in tumors has led to the development of powerful anti-cancer drugs. Therefore, an in-depth exploration of cell cycle dysregulation in cancers could provide therapeutic avenues for cancer treatment. The Hippo pathway is an evolutionarily conserved regulator network that controls organ size, and its dysregulation is implicated in various types of cancers. Although the role of the Hippo pathway in oncogenesis has been widely investigated, its role in cell cycle regulation has not been comprehensively scrutinized. Here, we specifically focus on delineating the involvement of the Hippo pathway in cell cycle regulation. To that end, we first compare the structural as well as functional conservation of the core Hippo pathway in yeasts, flies, and mammals. Then, we detail the multi-faceted aspects in which the core components of the mammalian Hippo pathway and their regulators affect the cell cycle, particularly with regard to the regulation of E2F activity, the G1 tetraploidy checkpoint, DNA synthesis, DNA damage checkpoint, centrosome dynamics, and mitosis. Finally, we briefly discuss how a collective understanding of cell cycle regulation and the Hippo pathway could be weaponized in combating cancer.

Lysophosphatidic Acid Mediates Imiquimod-Induced Psoriasis-like Symptoms by Promoting Keratinocyte Proliferation through LPAR1/ROCK2/PI3K/AKT Signaling Pathway

Psoriasis is a chronic inflammatory skin disease. Recently, lysophosphatidic acid (LPA)/LPAR5 signaling has been reported to be involved in both NLRP3 inflammasome activation in macrophages and keratinocyte activation to produce inflammatory cytokines, contributing to psoriasis pathogenesis. However, the effect and molecular mechanisms of LPA/LPAR signaling in keratinocyte proliferation in psoriasis remain unclear. In this study, we investigated the effects of LPAR1/3 inhibition on imiquimod (IMQ)-induced psoriasis-like mice. Treatment with the LPAR1/3 antagonist, ki16425, alleviated skin symptoms in IMQ-induced psoriasis-like mouse models and decreased keratinocyte proliferation in the lesion. It also decreased LPA-induced cell proliferation and cell cycle progression via increased cyclin A2, cyclin D1, cyclin-dependent kinase (CDK)2, and CDK4 expression and decreased p27^Kip1 expression in HaCaT cells. LPAR1 knockdown in HaCaT cells reduced LPA-induced proliferation, suppressed cyclin A2 and CDK2 expression, and restored p27^Kip1 expression. LPA increased Rho-associated protein kinase 2 (ROCK2) expression and PI3K/AKT activation; moreover, the pharmacological inhibition of ROCK2 and PI3K/AKT signaling suppressed LPA-induced cell cycle progression. In conclusion, we demonstrated that LPAR1/3 antagonist alleviates IMQ-induced psoriasis-like symptoms in mice, and in particular, LPAR1 signaling is involved in cell cycle progression via ROCK2/PI3K/AKT pathways in keratinocytes.

Downregulation of acylglycerol kinase suppresses high glucose-induced endothelial-mesenchymal transition in HRECs through regulating the LPAR1/TGF-β/Notch signaling pathway

The endothelial-mesenchymal transition (EndMT) participates in the progression of diabetic retinopathy (DR), but cell-intrinsic factors modulating this process remain elusive. In this study, we explored the role of lysophosphatidic acid (LPA)-producing enzyme, acylglycerol kinase (AGK) in the EndMT of human retinal microvascular endothelial cells (HRECs) under high glucose (HG) conditions. We found that AGK was significantly elevated in HG-treated cells. In addition, AGK knockdown reversed the HG-induced EndMT in HRECs, which was evidenced by the increased epithelial markers (CD31 and VE-cadherin) and decreased mesenchymal markers (FSP1 and α-SMA). Furthermore, downregulation of AGK inhibited the HG-induced activation of TGF-β/Notch pathways, whereas exogenous TGF-β1 (10 ng/ml) impeded the inhibitory effects of AGK knockdown on HG-induced EndMT in HRECs. Additionally, the silence of AGK abolished the HG-induced upregulation of LPA and its receptor LPAR1, and overexpression of LPAR1 further rescued the AGK knockdown-mediated inhibition of the EndMT process. In conclusion, we demonstrate that downregulation of acylglycerol kinase suppresses high glucose-induced endothelial-mesenchymal transition in HRECs through regulating the LPAR1/TGF-β/Notch signaling pathway, indicating that AGK might be a potential therapeutic target for the treatment of DR.

Activation of Rac1 Has an Opposing Effect on Induction and Maintenance of Long-Term Potentiation in Hippocampus by Acting on Different Kinases

Rac1 is a small GTPase of the Rho family. A previous study showed that the activation of Rac1 had an opposing effect on induction and maintenance of long-term potentiation (LTP) in the hippocampus. However, the molecular mechanism underlying this opposing effect remains to be addressed. In the present work, we find that the activation of Rac1 during the induction of LTP leads to an activation of PKCι/λ by phosphatidylinositol-3-kinase (PI3K), whereas the activation of Rac1 during the maintenance of LTP leads to the inhibition of PKMζ by LIM_kinase (LIMK) in the hippocampus. This result suggests that during different stages of LTP, the activation of Rac1 can modulate different signaling pathways, which leads to an opposing effect on the induction and maintenance of LTP in the hippocampus.

Proliferation Increasing Genetic Engineering in Human Corneal Endothelial Cells: A Literature Review

The corneal endothelium is the inner layer of the cornea. Despite comprising only a monolayer of cells, dysfunction of this layer renders millions of people visually impaired worldwide. Currently, corneal endothelial transplantation is the only viable means of restoring vision for these patients. However, because the supply of corneal endothelial grafts does not meet the demand, many patients remain on waiting lists, or are not treated at all. Possible alternative treatment strategies include intracameral injection of human corneal endothelial cells (HCEnCs), biomedical engineering of endothelial grafts and increasing the HCEnC density on grafts that would otherwise have been unsuitable for transplantation. Unfortunately, the limited proliferative capacity of HCEnCs proves to be a major bottleneck to make these alternatives beneficial. To tackle this constraint, proliferation enhancing genetic engineering is being investigated. This review presents the diverse array of genes that have been targeted by different genetic engineering strategies to increase the proliferative capacity of HCEnCs and their relevance for clinical and research applications. Together these proliferation-related genes form the basis to obtain a stable and safe supply of HCEnCs that can tackle the corneal endothelial donor shortage.

Activation of yes-associated protein mediates sphingosine-1-phosphate-induced proliferation and migration of pulmonary artery smooth muscle cells and its potential mechanisms

The aims of the present study were to examine the molecular mechanisms underlying sphingosine-1-phosphate (S1P)-induced rat pulmonary artery smooth muscle cells (PASMCs) proliferation/migration and to determine the effect of yes-associated protein (YAP) activation on S1P-induced PASMCs proliferation/migration and its potential mechanisms. S1P induced YAP dephosphorylation and nuclear translocation, upregulated microRNA-130a/b (miR-130a/b) expression, reduced bone morphogenetic protein receptor 2 (BMPR2), and inhibitor of DNA binding 1(Id1) expression, and promoted PASMCs proliferation and migration. Pretreatment of cells with Rho-associated protein kinase (ROCK) inhibitor Y27632 suppressed S1P-induced YAP activation, miR-130a/b upregulation, BMPR2/Id1 downregulation, and PASMCs proliferation/migration. Knockdown of YAP using small interfering RNA also suppressed S1P-induced alterations of miR-130a/b, BMPR2, Id1, and PASMCs behavior. In addition, luciferase reporter assay indicated that miR-130a/b directly regulated BMPR2 expression in PASMCs. Inhibition of miR-130a/b functions by anti-miRNA oligonucleotides attenuated S1P-induced BMPR2/Id1 downregulation and the proliferation and migration of PASMCs. Taken together, our study indicates that S1P induces activation of YAP through ROCK signaling and subsequently increases miR-130a/b expression, which, in turn, downregulates BMPR2 and Id1 leading to PASMCs proliferation and migration.

Evaluation of moxifloxacin-induced cytotoxicity on human corneal endothelial cells

Moxifloxacin hydrochloride (MXF) is widely used for the prevention of bacterial endophthalmitis after intraocular surgeries. However, the safety issue of intracameral injection of MXF for human corneal endothelial cells (HCECs) is still debatable. In this study, we investigated concentration-dependent cytotoxicity (0.05–1 mg/ml) of MXF for immortalized HCECs (B4G12 cell) and the underlying mechanism. Reactive oxygen generation (ROS) and cell viability after MXF exposure was measured. Flow cytometric analysis and TUNEL assay was used to detect apoptotic HCECs after MXF exposure. Ultrastructure of damaged HCECs by MXF was imaged by transmission electron microscope. Western blot analysis and caspase 2, 3 and 8 analysis were used to reveal the underlying mechanism of MXF induced damage in HCECs. We found that MXF induced dose-dependent cytotoxicity in HCECs. MXF exposure increased ROS generation and induced autophagy in HCECs. Increased LDH release represented the cellular membrane damage by MXF. In addition, caspases activation, Bax/Bcl-xL-dependent apoptosis pathway and apoptosis inducing factor nuclear translocation were all involved in MXF induced HCECs’ damage, especially after exposure to high dose of MXF (0.5 and 1.0 mg/ml). These findings suggest that MXF toxicity on HCECs should be thoroughly considered by ophthalmologists when intracameral injection of MXF is planned.

Low-intensity vibration restores nuclear YAP levels and acute YAP nuclear shuttling in mesenchymal stem cells subjected to simulated microgravity

Reducing the musculoskeletal deterioration that astronauts experience in microgravity requires countermeasures that can improve the effectiveness of otherwise rigorous and time-expensive exercise regimens in space. The ability of low-intensity vibrations (LIV) to activate force-responsive signaling pathways in cells suggests LIV as a potential countermeasure to improve cell responsiveness to subsequent mechanical challenge. Mechanoresponse of mesenchymal stem cells (MSC), which maintain bone-making osteoblasts, is in part controlled by the "mechanotransducer" protein YAP (Yes-associated protein), which is shuttled into the nucleus in response to cyto-mechanical forces. Here, using YAP nuclear shuttling as a measurement outcome, we tested the effect of 72 h of clinostat-induced simulated microgravity (SMG) and daily LIV application (LIVDT) on the YAP nuclear entry driven by either acute LIV (LIVAT) or Lysophosphohaditic acid (LPA), applied after the 72 h period. We hypothesized that SMG-induced impairment of acute YAP nuclear entry would be alleviated by the daily application of LIVDT. Results showed that while both acute LIVAT and LPA treatments increased nuclear YAP entry by 50 and 87% over the basal levels in SMG-treated MSCs, nuclear YAP levels of all SMG groups were significantly lower than non-SMG controls. LIVDT, applied in parallel to SMG, restored the SMG-driven decrease in basal nuclear YAP to control levels as well as increased the LPA-induced but not LIVAT-induced YAP nuclear entry over SMG only, counterparts. These cell-level observations suggest that daily LIV treatments are a feasible countermeasure for restoring basal nuclear YAP levels and increasing the YAP nuclear shuttling in MSCs under SMG.

Corneal endothelium tissue engineering: An evolution of signaling molecules, cells, and scaffolds toward 3D bioprinting and cell sheets

Cornea is an avascular and transparent tissue that focuses light on retina. Cornea is supported by the corneal-endothelial layer through regulation of hydration homeostasis. Restoring vision in patients afflicted with corneal endothelium dysfunction-mediated blindness most often requires corneal transplantation (CT), which faces considerable constrictions due to donor limitations. An emerging alternative to CT is corneal endothelium tissue engineering (CETE), which involves utilizing scaffold-based methods and scaffold-free strategies. The innovative scaffold-free method is cell sheet engineering, which typically generates cell layers surrounded by an intact extracellular matrix, exhibiting tunable release from the stimuli-responsive surface. In some studies, scaffold-based or scaffold-free technologies have been reported to achieve promising outcomes. However, yet some issues exist in translating CETE from bench to clinical practice. In this review, we compare different corneal endothelium regeneration methods and elaborate on the application of multiple cell types (stem cells, corneal endothelial cells, and endothelial precursors), signaling molecules (growth factors, cytokines, chemical compounds, and small RNAs), and natural and synthetic scaffolds for CETE. Furthermore, we discuss the importance of three-dimensional bioprinting strategies and simulation of Descemet's membrane by biomimetic topography. Finally, we dissected the recent advances, applications, and prospects of cell sheet engineering for CETE.

Lysophosphatidic acid improves corneal endothelial density in tissue culture by stimulating stromal secretion of interleukin-1β

The short supply of donor corneas is exacerbated by the unsuitability of donors with insufficient endothelial cell density. Few studies have investigated promoting corneal endothelial cell proliferation to increase the endothelial cell density. We hypothesize that pre‐transplantation treatment of proliferative tissue‐cultivated corneas may increase corneal endothelial cell density. We observed that the airlift cultures were superior to immersion cultures with respect to both transparency and thickness. In this tissue culture system, we observed that lysophosphatidic acid increased the rabbit corneal endothelial cell density, number of BrdU‐positive cells and improve wound healing. We also observed an indirect effect of lysophosphatidic acid on corneal endothelial cell proliferation mediated by the stimulation of interleukin‐1β secretion from stromal cells. Human corneal tissues treated with lysophosphatidic acid or interleukin‐1β contained significantly more Ki‐67‐positive cells than untreated group. The lysophosphatidic acid‐ or interleukin‐1β‐treated cultured tissue remained hexagon‐shaped, with ZO‐1 expression and no evidence of the endothelial‐mesenchymal transition. Our novel protocol of tissue culture may be applicable for eye banks to optimize corneal grafting.

Topical Ascorbic Acid Ameliorates Oxidative Stress-Induced Corneal Endothelial Damage via Suppression of Apoptosis and Autophagic Flux Blockage

Compromised pumping function of the corneal endothelium, due to loss of endothelial cells, results in corneal edema and subsequent visual problems. Clinically and experimentally, oxidative stress may cause corneal endothelial decompensation after phacoemulsification. Additionally, in vitro and animal studies have demonstrated the protective effects of intraoperative infusion of ascorbic acid (AA). Here, we established a paraquat-induced cell damage model, in which paraquat induced reactive oxygen species (ROS) production and apoptosis in the B4G12 and ARPE-19 cell lines. We demonstrate that oxidative stress triggered autophagic flux blockage in corneal endothelial cells and that addition of AA ameliorated such oxidative damage. We also demonstrate the downregulation of Akt phosphorylation in response to oxidative stress. Pretreatment with ascorbic acid reduced the downregulation of Akt phosphorylation, while inhibition of the PI3K/Akt pathway attenuated the protective effects of AA. Further, we establish an in vivo rabbit model of corneal endothelial damage, in which an intracameral infusion of paraquat caused corneal opacity. Administration of AA via topical application increased its concentration in the corneal stroma and reduced oxidative stress in the corneal endothelium, thereby promoting corneal clarity. Our findings indicate a perioperative strategy of topical AA administration to prevent oxidative stress-induced damage, particularly for those with vulnerable corneal endothelia.

Exploring the Mesenchymal Stem Cell Secretome for Corneal Endothelial Proliferation

Ex vivo grown human corneal endothelial cells (HCEnC) are a new emerging treatment option to treat visually impaired patients aimed at alleviating the current global donor shortage. Expanding HCEnC is still challenging, and obtaining cells in sufficient quantities is a limiting factor. It is already known that conditioned medium obtained from bone marrow mesenchymal stem cells can stimulate the proliferation of endothelial cells. The aim of this study was to take this work a step further to identify some of the underlying factors responsible. We confirmed the stimulatory effect of the mesenchymal stem cell secretome seen previously and separated the exosomes from the soluble proteins using size exclusion chromatography. We demonstrated the presence of exosomes and soluble proteins in the early and late fractions, respectively, with transmission electron microscopy and protein assays. Proliferation studies demonstrated that growth stimulation could be reproduced with the later protein-rich fractions but not with the exosome-rich fraction. Antibody assays revealed the presence of the secreted proteins EGF, IGFBP2, and IGFBP6 in protein-high fractions, but the growth enhancement was not seen with purified protein formulations. In conclusion, we confirmed the stimulatory effect of stem cell-conditioned medium and have determined that the effect was attributable to the proteins rather than to the exosomes. We were not able to reproduce the growth stimulation, however, with the pure recombinant protein candidates tested. Specific identification of the underlying proteins using proteomics could render a bioactive protein that can be used for ex vivo expansion of cells or as an in vivo drug to treat early corneal endothelial damage.

Inhibition of cyclin-dependent kinase 7 down-regulates yes-associated protein expression in mesothelioma cells

Cyclin-dependent kinase 7 (CDK7) is a protein kinase that plays a major role in transcription initiation. Yes-associated protein (YAP) is a main effector of the Hippo/YAP signalling pathway. Here, we investigated the role of CDK7 on YAP regulation in human malignant pleural mesothelioma (MPM). We found that in microarray samples of human MPM tissue, immunohistochemistry staining showed correlation between the expression level of CDK7 and YAP (n = 70, r = .513). In MPM cells, CDK7 expression level was significantly correlated with GTIIC reporter activity (r = .886, P = .019). Inhibition of CDK7 by siRNA decreased the YAP protein level and the GTIIC reporter activity in the MPM cell lines 211H, H290 and H2052. Degradation of the YAP protein was accelerated after CDK7 knockdown in 211H, H290 and H2052 cells. Inhibition of CDK7 reduced tumour cell migration and invasion, as well as tumorsphere formation ability. Restoration of the CDK7 gene rescued the YAP protein level and GTIIC reporter activity after siRNA knockdown in 211H and H2052 cells. Finally, we performed a co-immunoprecipitation analysis using an anti-YAP antibody and captured the CDK7 protein in 211H cells. Our results suggest that CDK7 inhibition reduces the YAP protein level by promoting its degradation and suppresses the migration and invasion of MPM cells. Cyclin-dependent kinase 7 may be a promising therapeutic target for MPM.

YAP promotes the proliferation of neuroblastoma cells through decreasing the nuclear location of p27Kip1 mediated by Akt

Objective

We aimed to investigate the roles and underlying mechanisms of YAP in the proliferation of neuroblastoma cells.

Methods

The expression level of YAP was evaluated by Western blotting and immunocytochemistry. Cell viability, cell proliferation and growth were detected by CCK‐8, PH3 and Ki67 immunostaining, and the real‐time cell analyser system. The nuclear and cytoplasmic proteins of p27^Kip1 were dissociated by the nuclear‐cytosol extraction kit and were detected by Western blotting and immunocytochemistry. mRNA levels of Akt, CDK5 and CRM1 were determined by qRT‐PCR.

Results

YAP was enriched in SH‐SY5Y cells (a human neuroblastoma cell line). Knock‐down of YAP in SH‐SY5Y cells or SK‐N‐SH cell line (another human neuroblastoma cell line) significantly decreased cell viability, inhibited cell proliferation and growth. Mechanistically, knock‐down of YAP increased the nuclear location of p27^Kip1, whereas serum‐induced YAP activation decreased the nuclear location of p27^Kip1 and was required for cell proliferation. Meanwhile, overexpression of YAP in these serum‐starved SH‐SY5Y cells decreased the nuclear location of p27^Kip1, promoted cell proliferation and overexpression of p27^Kip1 in YAP‐activated cells inhibited cell proliferation. Furthermore, knock‐down of YAP reduced Akt mRNA and protein levels. Overexpression of Akt in YAP‐downregulated cells decreased the nuclear location of p27^Kip1 and accelerated the proliferation of SH‐SY5Y cells.

Conclusions

Our studies suggest that YAP promotes the proliferation of neuroblastoma cells through negatively controlling the nuclear location of p27^Kip1 mediated by Akt.

Lysophosphatidic acid-induced YAP/TAZ activation promotes developmental angiogenesis by repressing Notch ligand Dll4

Lysophosphatidic acid (LPA) is a potent lipid mediator with various biological functions mediated through six G protein-coupled receptors (GPCRs), LPA1-6. Previous studies have demonstrated that LPA-Gα12/Gα13 signaling plays an important role in embryonic vascular development. However, the responsible LPA receptors and underlying mechanisms are poorly understood. Here, we show a critical role of LPA4 and LPA6 in developmental angiogenesis. In mice, Lpa4;Lpa6 double knockout (DKO) embryos were lethal due to global vascular deficiencies, and endothelial cell (EC)-specific Lpa4;Lpa6 DKO retinas had impaired sprouting angiogenesis. Mechanistically, LPA activated the transcriptional regulators YAP and TAZ through LPA4/LPA6-mediated Gα12/Gα13-Rho-ROCK signaling in ECs. YAP/TAZ knockdown increased β-catenin- and Notch intracellular domain (NICD)-mediated endothelial expression of the Notch ligand delta-like 4 (DLL4). Fibrin gel sprouting assay revealed that LPA4/LPA6, Gα12/Gα13, or YAP/TAZ knockdown consistently blocked EC sprouting, which was rescued by a Notch inhibitor. Of note, the inhibition of Notch signaling also ameliorated impaired retinal angiogenesis in EC-specific Lpa4;Lpa6 DKO mice. Overall, these results suggest that the Gα12/Gα13-coupled receptors LPA4 and LPA6 synergistically regulate endothelial Dll4 expression through YAP/TAZ activation. This could in part account for the mechanism of YAP/TAZ-mediated developmental angiogenesis. Our findings provide a novel insight into the biology of GPCR-activated YAP/TAZ.

Extracellular Matrix Protein Coating of Processed Fish Scales Improves Human Corneal Endothelial Cell Adhesion and Proliferation

Purpose

Corneal transplantation can treat corneal endothelial diseases. Implanting cultivated human corneal endothelial cells (HCECs) via a cell carrier has clinical value as an alternative therapeutic strategy. This study was performed to compare the feasibility of fish scales and other biomaterials (gelatin and chitosan) as cell carriers and to investigate the effects of an extracellular matrix (ECM) protein coating to improve the cytocompatibility of fish scales.

Methods

The physical properties of gelatin, chitosan, and fish scales were compared. Immortalized HCECs (B4G12) were cultured on processed fish scales, which were coated with fibronectin, laminin, collagen IV, or FNC Coating Mix. Cell attachment and proliferation were evaluated by immunofluorescence, cell counting, and bromodeoxyuridine (BrdU) labeling assays. Immunoblots were used to examine the expression levels of integrin-linked kinase (ILK), phosphate-ILK, β-catenin, p63, and cell cycle mediators (cyclin D1 and p27^Kip1).

Results

The transparency of processed fish scales was better than that of chitosan, while the strength was higher than that of gelatin. The laminin, collagen IV, and FNC coatings facilitated B4G12 cell adhesion and proliferation, while fibronectin only facilitated cell adhesion. The laminin, collagen IV, and FNC coatings also upregulated phosphate-ILK and p63 expression. In addition, the FNC coating activated cell cycle mediators.

Conclusion

ECM protein-coated processed fish scales can serve as a novel cell carrier to facilitate the development of HCEC transplantation.

Translational Relevance

Improving the physical properties and cytocompatibility of fish scales as a cell carrier will facilitate the transplantation of HCECs into corneas for the purpose of cell therapy.

Effects of lysophosphatidic acid on human periodontal ligament stem cells from teeth extracted from dental patients

Despite their potential applications in future regenerative medicine, periodontal ligament stem cells (PDLSCs) are difficult to obtain in large amounts from patients. Therefore, maintaining stemness while expanding the cell numbers for medical use is the key to transitioning PDLSCs from the bench to the clinic. Lysophosphatidic acid (LPA), which is present in the human body and saliva, is a signaling molecule derived from phospholipids. In this study, we examined the effects of LPA on stemness maintenance in human PDLSCs. Several spindle-shaped and fibroblast-like periodontal ligament stem-like cell lines were established from PDLSC isolation. Among these cell lines, the most morphologically appropriate cell line was characterized. The expression levels of OCT4, NANOG (a stem cell marker), and CD90 (a mesenchymal stem cell marker) were high. However, CD73 (a negative marker of mesenchymal stem cells) expression was not observed. Notably, immunofluorescence analysis identified the expression of STRO-1, CD146 (a mesenchymal stem cell marker), and sex determining region Y-box 2 at the protein level. In addition, lipid droplets were stained by Oil red O after the induction of adipogenesis for 21 days, and mineralized nodules were stained by Alizarin Red S after the induction of osteogenesis for 14 days. Alkaline phosphate staining also demonstrated the occurrence of osteogenesis. In summary, we established a human PDLSC line, which could be applied as a cell source for tissue regeneration in dental patients. However, further studies are needed to determine the detailed effects of LPA on PDLSCs.

Butyrate promotes the adaptation of intestinal smooth muscle cells through the yes-associated protein (YAP) pathway in a rat model of short bowel syndrome

Our previous study demonstrated that the proliferation of human intestinal smooth muscle (ISM) cells was stimulated by butyrate through the yes-associated protein (YAP) pathway in vitro, suggesting a valuable approach for intestinal adaption of short bowel syndrome (SBS). This study was conducted to confirm these findings in vivo. Three-week-old Sprague-Dawley rats were randomly divided into the following groups: Sham group (bowel transection and reanastomosis), SB W group (80% small bowel resection/water ad libitum), and SB Bu group (80% small bowel resection/50 mM sodium butyrate ad libitum). Morphological changes were determined by hematoxylin and eosin staining; the proliferation rate of ISM cells was examined by Ki67 staining, and apoptosis was determined in the TUNEL assay. Changes in the expression of YAP and its downstream genes were evaluated by quantitative-polymerase chain reaction and western blotting. Fourteen days post-operation, a significant increase in ISM thickness was observed in the SB Bu group compared to the SB W group, accompanied by enhanced proliferation of ISM cells and suppression of apoptosis. Notably, YAP expression was also significantly increased in the SB Bu group, with a 6.5-fold increase in the proportion of YAP-positive ISM cells, 2.2-fold increase in YAP mRNA expression, and 3.4-fold increase in protein expression. In conclusion, our results suggest that butyrate promotes ISM adaption through YAP in vivo, which may be a potential therapeutic approach for SBS patients.

TCF21 inhibits proliferation and chemoresistance through the AKT pathway in human gastric cancer

In a previous study, we showed that transcription factor 21 (TCF21) is methylated and downregulated in human gastric cancer samples and serves as an independent prognostic factor. However, its biological role and potential mechanism in gastric cancer cells remain unexplored. In the current study, we examined TCF21 expression in 6 gastric cancer cell lines. The BGC-823 and SGC-7901 cell lines were selected for small interfering RNA and plasmid transfection, respectively. The results of the Cell Counting Kit-8 assay demonstrated that TCF21 inhibited gastric cancer cell proliferation. Cell cycle analysis suggested that TCF21 inhibited cell cycle progression in gastric cancer cells. The Matrigel invasion assay demonstrated that TCF21 negatively regulated invasion. The cell adhesion assay showed that TCF21 increased cell adhesion. Gastric cancer cells were treated with cisplatin to explore the role of TCF21 in chemoresistance. Cell Counting Kit-8 assay and AnnexinV/propidium iodide analyses showed that TCF21 overexpression sensitized SGC-7901 cells to cisplatin, whereas its depletion reduced sensitivity in BGC-823 cells. JC-1 staining was performed to measure the effect of TCF21 on mitochondrial potential. TCF21 downregulated mitochondrial membrane potential after treatment with cisplatin. Western blot analysis showed that TCF21 overexpression negatively regulated Bcl-xL, phosphorylated extracellular signal regulated kinase, and phosphorylated AKT expression and induced caspase 3 cleavage. LY294002, an AKT inhibitor, blocked the effect of TCF21 on Bcl-xL, caspase 3 and CDDP-induced apoptosis. Nude mice experiments demonstrated that TCF21 inhibited gastric cancer growth in vivo. In conclusion, our results suggest that TCF21 inhibits gastric cancer growth and chemoresistance possibly through the AKT signaling pathway.

The transcriptional co-activator YAP: A new player in head and neck cancer

The Hippo-YAP (Yes-associated protein) pathway is a key regulator of tissue growth, organ size and stem cell function. More recently, a fundamental role for this pathway has emerged in stem cell function and tumorigenesis. Activation of the transcriptional co-activator YAP promotes cell-contact independent proliferation, epithelial to mesenchymal transition (EMT), cancer stem cell features and drug resistance. In this review, we describe the main components of the pathway, the microenvironment and the cell-intrinsic cues governing its activation, the downstream players of the pathway and the biological implications of their activation in the context of cancer. We will focus on the existing knowledge of this pathway in head and neck squamous carcinoma (HNSCC), its clinical value in this type of cancer as a marker of poor prognosis and resistance to therapy, as well as the most encouraging therapeutic strategies targeting the pathway.

TGF-β1 promotes cell barrier function upon maturation of corneal endothelial cells

Human corneal endothelial cells (HCECs) easily become fibroblastic-like when cultured, rendering them unsuitable for tissue engineering of the cornea. Transforming growth factor β (TGF-β) could be a key factor in this phenomenon; however, TGF-β is also known to maintain the endothelium in a quiescent state in vivo. This work aimed to compare the effects of TGF-β1 on the phenotype of HCECs during the proliferation and maturation phases. Our results show that addition of TGF-β1 during the active proliferation phase produced fibroblastic HCECs and loss of the cell junction markers ZO-1 and n-cadherin, independent from the presence of epidermal growth factor (EGF). By contrast, addition of TGF-β1 in maturation media containing few mitogens led to an endothelial phenotype and functional cell junctions as HCECs developed a high trans-endothelial resistance. Furthermore, addition of AG-1478, an epithelial growth factor receptor inhibitor, enhanced the gain of the endothelial phenotype and cell barrier function. Overall, these results show that TGF-β1 can be used to promote the formation of a typical leaky endothelial barrier during the maturation phase of cultured HCECs. A two-phase culture of HCECs using distinct proliferation and maturation media could also be key for developing ideal HCEC culture conditions.

Inhibition of YAP ameliorates choroidal neovascularization via inhibiting endothelial cell proliferation

Purpose

Age-related macular degeneration (AMD) is the leading cause of central visual loss among patients over the age of 55 years worldwide. Neovascular-type AMD (nAMD) accounts for approximately 10% of patients with AMD and is characterized by choroidal neovascularization (CNV). The proliferation of choroidal endothelial cells (CECs) is one important step in the formation of new vessels. Transcriptional coactivator Yes-associated protein (YAP) can promote the proliferation of multiple cancer cells, corneal endothelial cells, and vascular smooth muscle cells, which participate in angiogenesis. This study intends to reveal the expression and functions of YAP during the CNV process.

Methods

In the study, a mouse CNV model was generated by laser photocoagulation. YAP expression was detected with western blotting and immunohistochemistry. YAP siRNA and ranibizumab, a VEGF monoclonal antibody, were injected intravitreally in CNV mice. The YAP and VEGF expression levels after injection were detected with western blotting. The incidence and leakage area of CNV were measured with fundus fluorescein angiography, choroidal flat mounting, and hematoxylin and eosin (HE) staining. Immunofluorescent double staining was used to detect YAP cellular localization with CD31 (an endothelial cell marker) antibody. Proliferating cell nuclear antigen (PCNA) expression in CNV mice without or with YAP siRNA intravitreal injection and the colocalization of PCNA and CD31 were measured with western blotting and immunofluorescent double staining, respectively.

Results

YAP expression increased following laser exposure, in accordance with vascular endothelial growth factor (VEGF) expression. YAP siRNA and ranibizumab decreased VEGF expression and the incidence and leakage area of CNV. YAP was localized in the vascular endothelium within the CNV site. Additionally, after laser exposure, YAP siRNA inhibited the increased expression of PCNA, which was colocalized with endothelial cells.

Conclusions

This study showed that YAP upregulation promoted CNV formation by upregulating the proliferation of endothelial cells, providing evidence for the molecular mechanisms of CNV and suggesting a novel molecular target for nAMD treatment.

Safety of Nonporous Silica Nanoparticles in Human Corneal Endothelial Cells

Nonporous silica nanoparticles (SiNPs) are promising drug carrier platforms for intraocular drug delivery. In this study, we investigated the safety of three different sizes of SiNPs (50, 100, and 150 nm) in a human corneal endothelial cell (HCEC) line, B4G12. The HCECs were exposed to different concentrations (0, 25, 50, and 100 µg/ml) of three sizes of SiNPs for up to 48 h. Cellular viability, autophagy, lactate dehydrogenase (LDH) assay, and mammalian target of rapamycin (mTOR) pathway activation were evaluated. Intracellular distribution of the SiNPs was evaluated with transmission electron microscopy (TEM). TEM revealed that the SiNPs were up-taken by the HCECs inside cytoplasmic vacuoles. No mitochondrial structural damage was observed. Both cellular viability and LDH level remained unchanged with up to 100 µg/mL of SiNP treatment. Autophagy showed a significant dose-dependent activation with 50, 100, and 150 nm SiNPs. However, the mTOR activation remained unchanged. Human corneal tissue culture with 100 µg/ml concentrations of SiNPs for 72 h revealed no significant endothelial toxicity. In vivo corneal safety of the SiNPs (0.05 ml intracameral injection, 200 mg/ml concentration) was also verified in rabbit models. These findings suggested that 50, 100, and 150 nm SiNPs did not induce acute significant cytotoxicity in corneal endothelial cells at concentrations up to 100 µg/mL. However, long-term toxicity of SiNPs remains unknown.

Therapy of corneal endothelial dysfunction with corneal endothelial cell-like cells derived from skin-derived precursors

Corneal endothelial dysfunction occurs when corneal endothelial cells (CECs) are dramatically lost and eventually results in vision loss. Corneal transplantation is the only solution at present. However, corneal transplantation requires a fresh human cornea and there is a worldwide shortage of donors. Therefore, finding new functional CECs to replace human CECs is urgent. Skin-derived precursors (SKPs) can be easily acquired and have multiple differential potential. We co-cultured human SKPs with B4G12 cells in serum-free medium and obtained abundant CEC-like cells which had similar morphology and characteristic to human CECs. CEC-like cells exerted excellent therapeutic effect when they were transplanted into rabbit and monkey corneal endothelial dysfunction models by injection method. This protocol enables efficient production of CEC-like cells from SKPs. The renewable cell source, novel derivation method and simple treatment strategy may lead to potential applications in cell replacement therapy for corneal endothelial dysfunction.

Cytoresistance after acute kidney injury is limited to the recovery period of proximal tubule integrity and possibly involves Hippo-YAP signaling

Rat proximal tubule (PT) cells that have recovered from severe acute kidney injury induced by uranyl acetate (UA) develop cytoresistance to subsequent UA treatments. We reported that enhanced G1 arrest might contribute to cytoresistance. Herein, we examined these mechanisms by investigating Yes-associated protein (YAP), a regulator of cell number, and survivin, a downstream mediator of YAP that inhibits apoptosis. Rats pretreated with saline (vehicle group) or UA (AKI group) were injected with UA 2 weeks, 2 months, or 6 months after treatment. Cytoresistance, evaluated by serum creatinine, was observed at 2 weeks, was attenuated at 2 months, and was lost at 6 months in the AKI group. Based on immunohistochemistry, overexpressed YAP/survivin in PT cells and an increased number of PT cells was found before the second insult at 2 weeks, regressed gradually, and returned to a normal value by 6 months in the AKI group. Cell cycle status, assessed by flow cytometry, was equivalent in all groups before the second insult. However, early G1 phase (cyclin D1-) and p27+ PT cells increased in the AKI group compared to those in the vehicle group until 2 months, but were comparable to those in the vehicle group at 6 months. p21+ PT cells increased at 2 weeks, but normalized by 2 months. Thus, PT cells that have recovered from AKI transiently overexpress YAP/survivin, probably inhibiting apoptosis and resulting in acquired cytoresistance. This effect occurs until PT remodeling is complete, subceullular PT integrity is restored, and cell numbers are normalized.

WWC3 downregulation correlates with poor prognosis and inhibition of Hippo signaling in human gastric cancer

The aim of this study was to investigate the clinicopathological significance and biological roles of WWC3 in human gastric cancer (GC). Clinical significance of WWC3 in human GCs was examined by using immunohistochemistry (IHC). WWC3 was downregulated in 48 of 111 human GCs, and its downregulation was associated with advanced stage, positive nodal status, and higher relapse rate. Importantly, WWC3 downregulation correlated with poor survival. It was also found that WWC3 protein expression was downregulated in GC cell lines compared with normal cell line GES-1. On one hand, WWC3 overexpression inhibited the cell growth rate and invading ability in HGC-27 cell line. On the other hand, depleting WWC3 by small interfering RNA (siRNA) promoted proliferation rate and invading ability in the SGC-7901 cell line. In addition, cell cycle analysis showed that WWC3 overexpression inhibited while its depletion accelerated cell cycle progression at the G1/S transition. Western blot (WB) analysis demonstrated that WWC3 repressed cyclin D1 and cyclin E while upregulated p27 expression. Luciferase reporter assay showed that WWC3 activated Hippo signaling pathway by suppressing TEAD transcription activity, with downregulation of total and nuclear YAP and its target CTGF. WWC3 siRNA depletion exhibited the opposite effects. In conclusion, this study indicates that WWC3 serves as a tumor suppressor in GC by activating Hippo signaling.

A human cellular system for analyzing signaling during corneal endothelial barrier dysfunction

Correct corneal endothelial barrier function is essential for maintaining corneal transparency. However, research on cell signaling pathways mediating corneal endothelial barrier dysfunction has progressed more slowly than that involving other cellular barriers because of the lack of human corneal endothelial cell models. Here we have optimized the culture of the human corneal endothelial cell (HCEC) line B4G12 as a model for studying paracellular permeability. We show that B4G12-HCECs form confluent monolayers with stable cell-cell junctions when cultured on plastic, but not glass, surfaces precoated with various extracellular matrix components. Cell morphometry and measuring intercellular spaces and transendothelial electric resistance indicate that B4G12-HCECs form optimal monolayers on collagen and fibronectin. Based on the use of specific inhibitors, it has been proposed that the Rho-regulated kinases, ROCK-I and ROCK-II, mediate actomyosin-induced contraction in corneal endothelial cell barriers. ROCKs are effectors of RhoA, RhoB and RhoC. We show that the GTPase RhoA and its effector ROCK-II are predominantly expressed in B4G12-HCECs and primary human corneal endothelial cells. The activation of Rho GTPases during acute barrier disruption has not been investigated in corneal endothelial cells. RhoA, but not other related GTPases that are highly expressed in B4G12-HCECs, such as Rac1 and Cdc42, is transiently activated during barrier disruption in response to the inflammatory mediator thrombin. Pharmacological inhibition of RhoA and ROCK reduces B4G12-HCEC acute contraction. We propose that exploiting B4G12-HCECs is a useful experimental strategy for gaining further insight into the signaling pathways involved in human corneal endothelial barrier function.

Biomechanical relationships between the corneal endothelium and Descemet's membrane

The posterior face of the cornea consists of the corneal endothelium, a monolayer of cuboidal cells that secrete and attach to Descemet's membrane, an exaggerated basement membrane. Dysfunction of the endothelium compromises the barrier and pump functions of this layer that maintain corneal deturgesence. A large number of corneal endothelial dystrophies feature irregularities in Descemet's membrane, suggesting that cells create and respond to the biophysical signals offered by their underlying matrix. This review provides an overview of the bidirectional relationship between Descemet's membrane and the corneal endothelium. Several experimental methods have characterized a richly topographic and compliant biophysical microenvironment presented by the posterior surface of Descemet's membrane, as well as the ultrastructure and composition of the membrane as it builds during a lifetime. We highlight the signaling pathways involved in the mechanotransduction of biophysical cues that influence cell behavior. We present the specific example of Fuchs' corneal endothelial dystrophy as a condition in which a dysregulated Descemet's membrane may influence the progression of disease. Finally, we discuss some disease models and regenerative strategies that may facilitate improved treatments for corneal dystrophies.

The Steroid Hormone 20-Hydroxyecdysone Promotes the Cytoplasmic Localization of Yorkie to Suppress Cell Proliferation and Induce Apoptosis

The transcriptional co-activator Yki (Yorkie), a member of the Hippo pathway, regulates cell proliferation or apoptosis, depending on its nuclear or cytoplasmic location. However, the upstream factors regulating the subcellular localization of Yki are unclear. We found that the steroid hormone 20-hydroxyecdysone (20E) induces phosphorylation of Yki, causing it to remain in the cytoplasm, where it promotes apoptosis in the midgut of the lepidopteran insect Helicoverpa armigera Yki is expressed in various tissues, with an increase in the epidermis and midgut during early metamorphic molting. Yki is localized mainly in the nucleus of feeding larval midgut cells but is mainly localized in the cytoplasm of metamorphic molting larval midgut cells. The knockdown of Yki in the feeding larvae promotes larval-pupal transition, midgut programmed cell death, and repressed IAP1 (inhibitor of apoptosis 1) expression. Knockdown of Yki in the epidermal cell line (HaEpi) induced increased activation of Caspase3/7. Overexpressed Yki in HaEpi cells was mainly localized in the nucleus and induced cell proliferation. 20E promotes the cytoplasmic localization of Yki, reducing the expression of the IAP1, resulting in apoptosis. 20E promotes cytoplasmic retention of Yki by increasing Yki phosphorylation levels and promoting the interaction between Yki and the adaptor protein 14-3-3-ϵ. This regulation of Yki suppresses cell proliferation and induces cell apoptosis.

ATX-LPA1 axis contributes to proliferation of chondrocytes by regulating fibronectin assembly leading to proper cartilage formation

The lipid mediator lysophosphatidic acid (LPA) signals via six distinct G protein-coupled receptors to mediate both unique and overlapping biological effects, including cell migration, proliferation and survival. LPA is produced extracellularly by autotaxin (ATX), a secreted lysophospholipase D, from lysophosphatidylcholine. ATX-LPA receptor signaling is essential for normal development and implicated in various (patho)physiological processes, but underlying mechanisms remain incompletely understood. Through gene targeting approaches in zebrafish and mice, we show here that loss of ATX-LPA₁ signaling leads to disorganization of chondrocytes, causing severe defects in cartilage formation. Mechanistically, ATX-LPA₁ signaling acts by promoting S-phase entry and cell proliferation of chondrocytes both in vitro and in vivo, at least in part through β1-integrin translocation leading to fibronectin assembly and further extracellular matrix deposition; this in turn promotes chondrocyte-matrix adhesion and cell proliferation. Thus, the ATX-LPA₁ axis is a key regulator of cartilage formation.

Yes-associated protein (YAP) signaling regulates lipopolysaccharide-induced tissue factor expression in human endothelial cells

BACKGROUND

Sepsis-induced acute lung injury (ALI) is characterized by fibrin deposition, which indicates the local activation of coagulation. Tissue factor (TF), expressed in the pulmonary microvasculature, acts as a critical initiator of blood coagulation and ALI in sepsis. The molecular mechanism of lipopolysaccharide (LPS)-induced TF expression in endothelial cells (ECs), however, has not been determined. In this study, we implicate the Rho-associated protein kinase (ROCK)/Yes associated protein (YAP)/early growth response (Egr-1) signaling pathway in LPS-induced TF expression in vitro and in sepsis-induced ALI in vivo.

METHODS

Human umbilical vein ECs incubated with LPS were pretreated with or without the ROCK inhibitor Y-27632, a YAP small, interfering RNA (siRNA) and an Egr-1 siRNA. ROCK, YAP and Egr-1 signaling-induced protein expression was investigated by Western blot. The LPS-induced activation of YAP was analyzed by an immunofluorescent assay. Furthermore, we intratracheally injected YAP siRNA to assess septic ALI in mice by hematoxylin and eosin staining.

RESULTS

LPS rapidly induced ROCK activation and increased TF expression in ECs. LPS caused YAP shuttling into the nuclei of ECs and combined with Egr-1 via the activation of ROCK. Furthermore, the LPS-mediated TF expression increase was prevented by ROCK inactivation, YAP knockdown and Egr-1 depletion, suggesting that LPS-induced TF expression is closely associated with the ROCK/YAP/Egr-1 signaling pathway in ECs. Finally, an intratracheal injection of YAP siRNA relieved lung injury in septic mice.

CONCLUSION

This study not only suggests that ROCK/YAP/Egr-1 signaling regulates TF expression after stimulation with LPS in ECs, but it also indicates that LPS-induced activation of YAP signaling plays an important role in septic ALI in mice. Our findings provide a new insight into the pathogenic mechanism of TF expression, which is closely linked to septic ALI, and YAP signaling is considered to be a novel target for therapeutic intervention under septic conditions.