YAP inhibition enhances the differentiation of functional stem cell-derived insulin-producing β cells

Salt-inducible kinases transduce mechanical forces into the specification of the pancreatic endocrine lineage

The extracellular matrix-F-actin-Yes-associated protein 1 (YAP1)-Notch mechanosignaling axis is a gatekeeper in the fate decisions of bipotent pancreatic progenitors (bi-PPs). However, the link between F-actin dynamics and YAP1 activity remains poorly understood. Here, we identify salt-inducible kinases (SIKs) as mediators of F-actin-triggered changes in YAP1 activity. Interestingly, sodium chloride treatment promotes the differentiation of bi-PPs into NEUROG3+ endocrine progenitors (EPs) through enhanced SIK expression. Consistently, the pan-SIK inhibitor HG-9-09-01 (HG) inhibits latrunculin B (LatB)-induced EP differentiation via nuclear YAP1 accumulation. Unexpectedly, withdrawal of HG after a 12-h treatment increased SIK expression by a negative feedback mechanism, leading to significantly enhanced endocrinogenesis. Therefore, the combined treatment of bi-PPs with LatB and HG for 12 h boosted endocrinogenesis, ultimately leading to an increased number of beta cells. In summary, we identify SIKs as new transducers of mechanotransduction-triggered induction of pancreatic endocrine cell fates.

Effects of Neurogenin 3 Induction on Endocrine Differentiation and Delamination in Adult Human Pancreatic Ductal Organoids

Diabetes mellitus is characterized by the loss of pancreatic insulin-secreting β-cells in the Islets of Langerhans. Understanding the regenerative potential of human islet cells is relevant in the context of putative restoration of islet function after damage and novel islet cell replacement therapies. Adult human pancreatic tissue can be cultured as three-dimensional organoids with the capacity for long-term expansion and the promise of endocrine cell formation. Here, we characterize the endocrine differentiation potential of human adult pancreatic organoids. Because exocrine-to-endocrine differentiation is dependent on the expression of Neurogenin 3 (NEUROG3), we first generated NEUROG3-inducible organoid lines. We show that doxycycline-induced NEUROG3 expression in the organoids leads to the formation of chromogranin A positive (CHGA+) endocrine progenitor cells. The efficiency of this differentiation was improved with the addition of thyroid hormone T3 and the AXL inhibitor R428. Further, compound screening demonstrated that modifying the pivotal embryonic endocrine pancreas signalling pathways driven by Notch, YAP, and EGFR led to increased NEUROG3 expression in organoids. In a similar fashion to embryonic development, adult ductal cells delaminated from the organoids after NEUROG3 induction. Thus, mechanisms in islet (re)generation including the initiation of endocrine differentiation and delamination can be achieved by NEUROG3 induction.

Characterization of Hippo signaling components in the early dorsal pancreatic bud

All pancreatic lineages originate from a transitory structure known as the multipotent progenitor epithelium (MPE), which is an endodermal placode formed via epithelial stratification. Cells within the MPE undergo de novo lumenogenesis to give rise to an epithelial plexus, which serves as a progenitor niche for subsequent development of endocrine, ductal and acinar cell types. Recent evidence suggests that Hippo signaling is required for pancreatic cell differentiation, but little is known about the function of Hippo signaling in the development of the MPE. Here, we characterize the expression of YAP1, TAZ, and the Hippo regulators LATS1/2 kinases and MERLIN in early murine pancreatic epithelium, during epithelial stratification, plexus development and emergence of endocrine cells. We find that YAP1 expression is relatively low in the pancreas bud during stratification but increases by E11.5. Intriguingly, we find differing patterns of TAZ and YAP1 immunoreactivty throughout pancreatic development. We further find that MERLIN and LATS1/2 kinases are expressed during the period of rapid stratification and become markedly apical at nascent lumens. To gain a better understanding of how Hippo signaling and lumen formation are connected, we analyzed the subcellular localization of Hippo signaling components during varying stages of lumen formation and found that they are dynamically localized during lumenogenesis. Together, our results point to a previously unsuspected relationship between Hippo signaling and lumen formation during pancreatic development.

AG73-GelMA/AlgMA hydrogels provide a stable microenvironment for the generation of pancreatic progenitor organoids

Patient specific induced pluripotent stem cells (iPSCs) derived β cells represent an effective means for disease modeling and autologous diabetes cell replacement therapy. In this study, an AG73-5%gelatin methacryloyl (GelMA) /2% alginate methacrylate (AlgMA) hydrogel was employed to generate pancreatic progenitor (PP) organoids and improve stem cell-derived β (SC-β) cell differentiation protocol. The laminin-derived homolog AG73, which mimics certain cell‒matrix interactions, facilitates AKT signaling pathway activation to promote PDX1+/NKX6.1+ PP organoid formation and effectively modulates subsequent epithelial-mesenchymal transition (EMT) in the endocrine lineage. The 5%GelMA/2%AlgMA hydrogel mimics the physiological stiffness of the pancreas, providing the optimal mechanical stress and spatial structure for PP organoid differentiation. The Syndecan-4 (SDC4)-ITGAV complex plays a pivotal role in the early stages of pancreatic development by facilitating the formation of SOX9+/PDX1+ bipotent PPs. Our findings demonstrate that AG73-GelMA/AlgMA hydrogel-derived SC-β cells exhibit enhanced insulin secretion and accelerated hyperglycemia reversal in vivo. This study presents a cost-effective, stable, and efficient alternative for the comprehensive 3D culture of SC-β cells in vitro by mitigating the uncertainties associated with conventional culture methods.

Identification of mouse and human embryonic pancreatic cells with adult Procr+ progenitor transcriptomic and epigenomic characteristics

Background

The quest to find a progenitor cell in the adult pancreas has driven research in the field for decades. Many potential progenitor cell sources have been reported, but so far this is a matter of debate mainly due to reproducibility issues. The existence of adult Procr+ progenitor cells in mice islets has been recently reported. These were shown to comprise ~1% of islet cells, lack expression of Neurog3 and endocrine hormones, and to be capable of differentiating into all endocrine cell types. However, these findings had limited impact, as further evidence supporting the existence and function of Procr+ progenitors has not emerged.

Methods and findings

We report here an unbiased comparison across mouse and human pancreatic samples, including adult islets and embryonic tissue, to track the existence of Procr+ progenitors originally described based on their global gene expression signature. We could not find Procr+ progenitors on other mouse or human adult pancreatic islet samples. Unexpectedly, our results revealed a transcriptionally close mesothelial cell population in the mouse and human embryonic pancreas. These Procr-like mesothelial cells of the embryonic pancreas share the salient transcriptional and epigenomic features of previously reported Procr+ progenitors found in adult pancreatic islets. Notably, we report here that Procr-like transcriptional signature is gradually established in mesothelial cells during mouse pancreas development from E12.5 to E17.5, which has its largest amount. Further supporting a developmentally relevant role in the human pancreas, we additionally report that a transcriptionally similar population is spontaneously differentiated from human pluripotent stem cells cultured in vitro along the pancreatic lineage.

Conclusions

Our results show that, although the previously reported Procr+ progenitor cell population could not be found in other adult pancreatic islet samples, a mesothelial cell population with a closely related transcriptional signature is present in both the mouse and human embryonic pancreas. Several lines of evidence presented in this work support a developmentally relevant function for these Procr-like mesothelial cells.

Mechanism and therapeutic potential of hippo signaling pathway in type 2 diabetes and its complications

Loss of pancreatic islet cell mass and function is one of the most important factors in the development of type 2 diabetes mellitus, and hyperglycemia-induced lesions in other organs are also associated with apoptosis or hyperproliferation of the corresponding tissue cells. The Hippo signaling pathway is a key signal in the regulation of cell growth, proliferation and apoptosis, which has been shown to play an important role in the regulation of diabetes mellitus and its complications. Excessive activation of the Hippo signaling pathway under high glucose conditions triggered apoptosis and decreased insulin secretion in pancreatic islet cells, while dysregulation of the Hippo signaling pathway in the cells of other organ tissues led to proliferation or apoptosis and promoted tissue fibrosis, which aggravated the progression of diabetes mellitus and its complications. This article reviews the mechanisms of Hippo signaling, its individual and reciprocal regulation in diabetic pancreatic pathology, and its emerging role in the pathophysiology of diabetic complications. Potential therapeutics for diabetes mellitus that have been shown to target the Hippo signaling pathway are also summarized to provide information for the clinical management of type 2 diabetes mellitus.

Extracellular matrix proteins refine microenvironments for pancreatic organogenesis from induced pluripotent stem cell differentiation

Rationale: The current understanding on manipulating signaling pathways to generate mature human islet organoids with all major hormone-secreting endocrine cell types (i.e., α, β, δ, and γ cells) from induced pluripotent stem cells (iPSCs) is insufficient. However, donor islet shortage necessitates that we produce functional islets in vitro. In this study, we aimed to find decellularized pancreatic extracellular matrix (dpECM) proteins that leverage signaling pathways and promote functional iPSC islet organogenesis. Methods: We performed proteomic analysis to identify key islet promoting factors from porcine and rat dpECM. With this, we identified collagen type II (COL2) as a potential biomaterial cue that endorses islet development from iPSCs. Using global transcriptome profiling, gene set enrichment analysis, immunofluorescence microscopy, flow cytometry, Western blot, and glucose-stimulated hormonal secretion analysis, we examined COL2's role in regulating iPSC pancreatic lineage specification and signaling pathways, critical to islet organogenesis and morphogenesis. Results: We discovered COL2 acts as a functional biomaterial that augments islet development from iPSCs, similar to collagen type V (COL5) as reported in our earlier study. COL2 substantially stimulates the formation of endocrine progenitors and subsequent islet organoids with significantly elevated expressions of pancreatic signature genes and proteins. Furthermore, it enhances islets' glucose sensitivity for hormonal secretion. A cluster of gene expressions associated with various signaling pathways, including but not limited to oxidative phosphorylation, insulin secretion, cell cycle, the canonical WNT, hypoxia, and interferon-γ response, were considerably affected by COL2 and COL5 cues. Conclusion: We demonstrated dpECM's crucial role in refining stem cell differentiation microenvironments for organoid development and maturation. Our findings on biomaterial-stimulated signaling for stem cell specification, organogenesis, and maturation open up a new way to increase the differentiation efficacy of endocrine tissues that can contribute to the production of biologically functional islets.

The Hippo Signaling Pathway Manipulates Cellular Senescence

The Hippo pathway, a kinase cascade, coordinates with many intracellular signals and mediates the regulation of the activities of various downstream transcription factors and their coactivators to maintain homeostasis. Therefore, the aberrant activation of the Hippo pathway and its associated molecules imposes significant stress on tissues and cells, leading to cancer, immune disorders, and a number of diseases. Cellular senescence, the mechanism by which cells counteract stress, prevents cells from unnecessary damage and leads to sustained cell cycle arrest. It acts as a powerful defense mechanism against normal organ development and aging-related diseases. On the other hand, the accumulation of senescent cells without their proper removal contributes to the development or worsening of cancer and age-related diseases. A correlation was recently reported between the Hippo pathway and cellular senescence, which preserves tissue homeostasis. This review is the first to describe the close relationship between aging and the Hippo pathway, and provides insights into the mechanisms of aging and the development of age-related diseases. In addition, it describes advanced findings that may lead to the development of tissue regeneration therapies and drugs targeting rejuvenation.

Neuregulin-1 reduces Doxorubicin-induced cardiotoxicity by upregulating YAP to inhibit senescence

The cardiotoxicity of Doxorubicin (Dox) limits its clinical application, creating an urgent need to investigate its underlying mechanism and develop effective therapies. Senescence plays an important role in Dox-induced cardiotoxicity (DIC). Recently, Neuregulin-1 (NRG1) was found to regulate Yes-associated protein (YAP), which was reported to inhibit senescence, suggesting that NRG1 might be used to treat DIC by inhibiting senescence through YAP regulation. We examined the changes and regulatory roles of YAP and senescence in Dox cardiotoxicity and whether NRG1 could reduce DIC in chronic DIC mice and Dox-treated H9c2 cells. Our study revealed that sustained small doses of Dox impaired cardiac function and H9c2 cell viability, induced myocardial senescence, and inhibited YAP expression. Conversely, high levels of YAP inhibited Dox-induced senescence in H9c2 cells, indicating that Dox promotes myocardial senescence by inhibiting YAP. In addition, we found that exogenous NRG1 inhibited the phosphorylation of LATS1 and MST1, thereby inhibiting YAP phosphorylation and promote the nuclear translocation of YAP, inhibiting senescence and attenuating Dox-induced cardiotoxicity. YAP knockdown or inhibition of YAP binding to TEA domain transcription factor protein （TEAD）blocks the protective effects of NRG1. In conclusion, our study suggests that Dox-induced myocardial senescence through YAP inhibition is one of the pathological mechanisms of its cardiotoxicity. Additionally, NRG1 reduces DIC by upregulating YAP to inhibit senescence.

Inhibition of proteasome activity facilitates definitive endodermal specification of pluripotent stem cells by influencing YAP signalling

AIMS

The knowledge of the molecular players that regulate the generation of endoderm cells is imperative to obtain homogenous population of pancreatic β-cells from stem cells. The Ubiquitin proteasome system (UPS) has been envisaged as a crucial intracellular protein degradation system, but its role in the generation of β-cells remains elusive. Hence, it would be appropriate to unravel the potential role of UPS in endoderm specification and utilize the understanding to generate β-cells from pluripotent stem cells.

MATERIALS AND METHODS

The pluripotent stem cells (mESCs, miPSCs and hIPSCs) were subjected to differentiation towards pancreatic β-cells and assessed the proteasomal activity during endodermal differentiation. Pharmacologic agents MG132 and IU-1 were employed to inhibit and activate proteasomal activity respectively at the definitive endoderm stage to investigate its impact on the generation of β-cells. The expression of stage-specific genes were analyzed at transcript and protein levels. We also explored the role of unfolded protein response and UPS-regulated signalling pathways in endodermal differentiation.

KEY FINDINGS

We observed decreased proteasomal activity specifically during endoderm, but not during the generation of other lineages. Extraneous proteasomal inhibition enhanced the expression of endodermal genes while increasing the proteasomal activity hindered definitive endodermal differentiation. Proteasomal inhibition at the definitive endodermal stage culminated in an enriched generation of insulin-positive cells. Elevated endodermal gene expression was consistent in mESCs and hIPSCs upon proteasomal inhibition. Mechanistic insight revealed the proteasome-inhibited enhanced endodermal differentiation to be via modulating the YAP pathway.

SIGNIFICANCE

Our study unravels the specific involvement of UPS in endoderm cell generation from pluripotent stem cells and paves the way for obtaining potential definitive endodermal cells for plausible cellular therapy in the future.

Exploring optimal protocols for generating and preserving glucose-responsive insulin-secreting progenitor cells derived from human pluripotent stem cells

Human pluripotent stem cells (hPSCs) represent an unlimited source of β-like cells for both disease modeling and cellular therapy for diabetes. Numerous protocols have been published describing the differentiation of hPSCs into β-like cells that secret insulin in response to a glucose challenge. However, among the most widely used protocols it is not clear which yield the most functional cells with reproducible glucose-stimulated insulin-secretion (GSIS). Moreover, the technical challenges in culturing and differentiating hPSCs is a barrier for many researchers. In this study, we performed a side-by-side functional comparison based on three widely used methods to generate insulin expressing cells and identified optimal stages and conditions for cryopreserving and reconstituting stem cell (SC)-derived islets with a robust GSIS. Despite the fact that each protocol yields SC-islets consisting of insulin and glucagon-expressing cells, the SC-islets obtained from the two more recent revised protocols were more functional as measured by robust and reproducible GSIS. Moreover, we demonstrate that pancreatic progenitors and differentiated endocrine cells that have been cryopreserved for up to 10 months, can be reconstituted into glucose responsive SC-islets. These findings should enable the use of human PSC-derived β-like cells technologies even by groups with minimal PSC culture experience.

Characterization of Hippo Signaling Components in the Early Dorsal Pancreatic Bud

All pancreatic lineages originate from a transitory structure known as the multipotent progenitor epithelium (MPE), which is a placode formed via epithelial stratification. Cells within the MPE undergo de novo lumenogenesis to give rise to an epithelial plexus, which serves as a progenitor niche for subsequent development of endocrine, ductal and acinar cell types. Recent evidence suggests that Hippo signaling is required for pancreatic cell differentiation, but little is known about the function of Hippo signaling in the development of the MPE. Here, we characterize the expression of YAP1, TAZ, and the Hippo regulators LATS1/2 kinases and MERLIN in early murine pancreatic epithelium, during epithelial stratification, plexus development and emergence of endocrine cells. We find that YAP1 expression is relatively low in the pancreas bud during stratification, but increases by E11.5. Intriguingly, we find that TAZ, but not YAP1, is expressed in early endocrine cells. We further find that MERLIN and LATS1/2 kinases are robustly expressed during the period of rapid stratification and become markedly apical at nascent lumens. To gain a better understanding of how Hippo signaling and lumen formation are connected, we analyzed the expression of Hippo signaling components in an in vitro model of lumen formation and found that they are dynamically regulated during lumenogenesis. Together, our results point to a relationship between Hippo signaling and lumen formation during pancreatic development.

HIGHLIGHTS

YAP1 expression in the early mouse pancreatic anlagen is low until approximately E11.5, when it becomes localized to cell nuclei in multipotent progenitor cells. At E14.5, we find nuclear YAP1 in ductal cells.YAP1 is not expressed in early and midgestation endocrine cells. By contrast, TAZ is expressed in first transition endocrine cells.Hippo regulators MERLIN and LATS1/2 kinases are robustly expressed in the early pancreatic bud by E10.5. Both MERLIN and LATS1/2 exhibit strong apical localization in epithelial cells at nascent microlumens. Using in vitro models of de novo pancreas lumen formation, we show that YAP1 nuclear localization is high in early phases of lumen formation and gradually decreases as lumens matures.

Tankyrase inhibition promotes endocrine commitment of hPSC-derived pancreatic progenitors

Human pluripotent stem cells (hPSCs) have the potential to differentiate into various cell types, including pancreatic insulin-producing β cells, which are crucial for developing therapies for diabetes. However, current methods for directing hPSC differentiation towards pancreatic β-like cells are often inefficient and produce cells that do not fully resemble the native counterparts. Here, we report that highly selective tankyrase inhibitors, such as WIKI4, significantly enhances pancreatic differentiation from hPSCs. Our results show that WIKI4 promotes the formation of pancreatic progenitors that give rise to islet-like cells with improved β-like cell frequencies and glucose responsiveness compared to our standard cultures. These findings not only advance our understanding of pancreatic development, but also provide a promising new tool for generating pancreatic cells for research and potential therapeutic applications.

Metabolic dysfunction-associated liver disease and diabetes: Matrix remodeling, fibrosis, and therapeutic implications

Metabolic dysfunction-associated liver disease (MASLD) and steatohepatitis (MASH) are becoming the most common causes of chronic liver disease in the United States and worldwide due to the obesity and diabetes epidemics. It is estimated that by 2030 close to 100 million people might be affected and patients with type 2 diabetes are especially at high risk. Twenty to 30% of patients with MASLD can progress to MASH, which is characterized by steatosis, necroinflammation, hepatocyte ballooning, and in advanced cases, fibrosis progressing to cirrhosis. Clinically, it is recognized that disease progression in diabetic patients is accelerated and the role of various genetic and epigenetic factors, as well as cell-matrix interactions in fibrosis and stromal remodeling, have recently been recognized. While there has been great progress in drug development and clinical trials for MASLD/MASH, the complexity of these pathways highlights the need to improve diagnosis/early detection and develop more successful antifibrotic therapies that not only prevent but reverse fibrosis.

β-Cell keratin 8 maintains islet mechanical integrity, mitochondrial ultrastructure, and β-cell glucose transporter 2 plasma membrane targeting

Islet β-cell dysfunction is an underlying factor for type I diabetes (T1D) development. Insulin sensing and secretion are tightly regulated in β-cells at multiple subcellular levels. The epithelial intermediate filament (IF) protein keratin (K) 8 is the main β-cell keratin, constituting the filament network with K18. To identify the cell-autonomous functions of K8 in β-cells, mice with targeted deletion of β-cell K8 (K8flox/flox; Ins-Cre) were analyzed for islet morphology, ultrastructure, and integrity, as well as blood glucose regulation and streptozotocin (STZ)-induced diabetes development. Glucose transporter 2 (GLUT2) localization was studied in β-cells in vivo and in MIN6 cells with intact or disrupted K8/K18 filaments. Loss of β-cell K8 leads to a major reduction in K18. Islets without β-cell K8 are more fragile, and these β-cells display disjointed plasma membrane organization with less membranous E-cadherin and smaller mitochondria with diffuse cristae. Lack of β-cell K8 also leads to a reduced glucose-stimulated insulin secretion (GSIS) response in vivo, despite undisturbed systemic blood glucose regulation. K8flox/flox, Ins-Cre mice have a decreased sensitivity to STZ compared with K8 wild-type mice, which is in line with decreased membranous GLUT2 expression observed in vivo, as GLUT2 is required for STZ uptake in β-cells. In vitro, MIN6 cell plasma membrane GLUT2 is rescued in cells overexpressing K8/K18 filaments but mistargeted in cells with disrupted K8/K18 filaments. β-Cell K8 is required for islet and β-cell structural integrity, normal mitochondrial morphology, and GLUT2 plasma membrane targeting, and has implications on STZ sensitivity as well as systemic insulin responses.NEW & NOTEWORTHY Keratin 8 is the main cytoskeletal protein in the cytoplasmic intermediate filament network in β-cells. Here for the first time, we assessed the β-cell autonomous mechanical and nonmechanical roles of keratin 8 in β-cell function. We demonstrated the importance of keratin 8 in islet and β-cell structural integrity, maintaining mitochondrial morphology and GLUT2 plasma membrane targeting.

Hippo pathway-mediated YAP1/TAZ inhibition is essential for proper pancreatic endocrine specification and differentiation

The Hippo pathway plays a central role in tissue development and homeostasis. However, the function of Hippo in pancreatic endocrine development remains obscure. Here, we generated novel conditional genetically engineered mouse models to examine the roles of Hippo pathway-mediated YAP1/TAZ inhibition in the development stages of endocrine specification and differentiation. While YAP1 protein was localized to the nuclei in bipotent progenitor cells, Neurogenin 3 expressing endocrine progenitors completely lost YAP1 expression. Using genetically engineered mouse models, we found that inactivation of YAP1 requires both an intact Hippo pathway and Neurogenin 3 protein. Gene deletion of Lats1 and 2 kinases (Lats1&2) in endocrine progenitor cells of developing mouse pancreas using Neurog3Cre blocked endocrine progenitor cell differentiation and specification, resulting in reduced islets size and a disorganized pancreas at birth. Loss of Lats1&2 in Neurogenin 3 expressing cells activated YAP1/TAZ transcriptional activity and recruited macrophages to the developing pancreas. These defects were rescued by deletion of Yap1/Wwtr1 genes, suggesting that tight regulation of YAP1/TAZ by Hippo signaling is crucial for pancreatic endocrine specification. In contrast, deletion of Lats1&2 using β-cell-specific Ins1CreER resulted in a phenotypically normal pancreas, indicating that Lats1&2 are indispensable for differentiation of endocrine progenitors but not for that of β-cells. Our results demonstrate that loss of YAP1/TAZ expression in the pancreatic endocrine compartment is not a passive consequence of endocrine specification. Rather, Hippo pathway-mediated inhibition of YAP1/TAZ in endocrine progenitors is a prerequisite for endocrine specification and differentiation.

Assessment of human embryonic stem cells differentiation into definitive endoderm lineage on the soft substrates

Pluripotent stem cells (PSCs) hold enormous potential for treating multiple diseases owing to their ability to self-renew and differentiate into any cell type. Albeit possessing such promising potential, controlling their differentiation into a desired cell type continues to be a challenge. Recent studies suggest that PSCs respond to different substrate stiffness and, therefore, can differentiate towards some lineages via Hippo pathway. Human PSCs can also differentiate and self-organize into functional cells, such as organoids. Traditionally, human PSCs are differentiated on stiff plastic or glass plates towards definitive endoderm and then into functional pancreatic progenitor cells in the presence of soluble growth factors. Thus, whether stiffness plays any role in differentiation towards definitive endoderm from human pluripotent stem cells (hPSCs) remains unclear. Our study found that the directed differentiation of human embryonic stem cells towards endodermal lineage on the varying stiffness did not differ from the differentiation on stiff plastic dishes. We also observed no statistical difference between the expression of yes-associated protein (YAP) and phosphorylated YAP. Furthermore, we demonstrate that lysophosphatidic acid, a YAP activator, enhanced definitive endoderm formation, whereas verteporfin, a YAP inhibitor, did not have the significant effect on the differentiation. In summary, our results suggest that human embryonic stem cells may not differentiate in response to changes in stiffness, and that such cues may not have as significant impact on the level of YAP. Our findings indicate that more research is needed to understand the direct relationship between biophysical forces and hPSCs differentiation.

Natural compounds targeting YAP/TAZ axis in cancer: Current state of art and challenges

Cancer has become a burgeoning global healthcare concern marked by its exponential growth and significant economic ramifications. Though advancements in the treatment modalities have increased the overall survival and quality of life, there are no definite treatments for the advanced stages of this malady. Hence, understanding the diseases etiologies and the underlying molecular complexities, will usher in the development of innovative therapeutics. Recently, YAP/TAZ transcriptional regulation has been of immense interest due to their role in development, tissue homeostasis and oncogenic transformations. YAP/TAZ axis functions as coactivators within the Hippo signaling cascade, exerting pivotal influence on processes such as proliferation, regeneration, development, and tissue renewal. In cancer, YAP is overexpressed in multiple tumor types and is associated with cancer stem cell attributes, chemoresistance, and metastasis. Activation of YAP/TAZ mirrors the cellular "social" behavior, encompassing factors such as cell adhesion and the mechanical signals transmitted to the cell from tissue structure and the surrounding extracellular matrix. Therefore, it presents a significant vulnerability in the clogs of tumors that could provide a wide window of therapeutic effectiveness. Natural compounds have been utilized extensively as successful interventions in the management of diverse chronic illnesses, including cancer. Owing to their capacity to influence multiple genes and pathways, natural compounds exhibit significant potential either as adjuvant therapy or in combination with conventional treatment options. In this review, we delineate the signaling nexus of YAP/TAZ axis, and present natural compounds as an alternate strategy to target cancer.

Identification and removal of unexpected proliferative off-target cells emerging after iPSC-derived pancreatic islet cell implantation

Differentiation of pancreatic endocrine cells from human pluripotent stem cells (PSCs) has been thoroughly investigated for application in cell therapy against diabetes. In the context of induced pancreatic endocrine cell implantation, previous studies have reported graft enlargement resulting from off-target pancreatic lineage cells. However, there is currently no documented evidence of proliferative off-target cells beyond the pancreatic lineage in existing studies. Here, we show that the implantation of seven-stage induced PSC-derived pancreatic islet cells (s7-iPICs) leads to the emergence of unexpected off-target cells with proliferative capacity via in vivo maturation. These cells display characteristics of both mesenchymal stem cells (MSCs) and smooth muscle cells (SMCs), termed proliferative MSC- and SMC-like cells (PMSCs). The frequency of PMSC emergence was found to be high when 108 s7-iPICs were used. Given that clinical applications involve the use of a greater number of induced cells than 108, it is challenging to ensure the safety of clinical applications unless PMSCs are adequately addressed. Accordingly, we developed a detection system and removal methods for PMSCs. To detect PMSCs without implantation, we implemented a 4-wk-extended culture system and demonstrated that putative PMSCs could be reduced by compound treatment, particularly with the taxane docetaxel. When docetaxel-treated s7-iPICs were implanted, the PMSCs were no longer observed. This study provides useful insights into the identification and resolution of safety issues, which are particularly important in the field of cell-based medicine using PSCs.

Biomimetic Hydrogels Promote Pseudoislet Formation to Improve Glycemic Control in Diabetic Mice

Islet or β-cell transplantation is currently considered to be the ideal treatment for diabetes, and three-dimensional (3D) bioprinting of a bionic pancreas with physiological stiffness is considered to be promising for the encapsulation and transplantation of β-cells. In this study, a 5%GelMA/2%AlgMA hybrid hydrogel with pancreatic physiological stiffness was constructed and used for β-cell encapsulation, 3D bioprinting, and in vivo transplantation to evaluate glycemic control in diabetic mice. The hybrid hydrogel had good cytocompatibility and could induce insulin-producing cells (IPCs) to form pseudoislet structures and improve insulin secretion. Furthermore, we validated the importance of betacellulin (BTC) in IPCs differentiation and confirmed that IPCs self-regulation was achieved by altering the nuclear and cytoplasmic distributions of BTC expression. In vivo transplantation of diabetic mice quickly restored blood glucose levels. In the future, 3D bioprinting of β-cells using biomimetic hydrogels will provide a promising platform for clinical islet transplantation for the treatment of diabetes.

Scaling Insulin-Producing Cells by Multiple Strategies

In the quest to combat insulin-dependent diabetes mellitus (IDDM), allogenic pancreatic islet cell therapy sourced from deceased donors represents a significant therapeutic advance. However, the applicability of this approach is hampered by donor scarcity and the demand for sustained immunosuppression. Human induced pluripotent stem cells are a game-changing resource for generating synthetic functional insulin-producing β cells. In addition, novel methodologies allow the direct expansion of pancreatic progenitors and mature β cells, thereby circumventing prolonged differentiation. Nevertheless, achieving practical reproducibility and scalability presents a substantial challenge for this technology. As these innovative approaches become more prominent, it is crucial to thoroughly evaluate existing expansion techniques with an emphasis on their optimization and scalability. This manuscript delineates these cutting-edge advancements, offers a critical analysis of the prevailing strategies, and underscores pivotal challenges, including cost-efficiency and logistical issues. Our insights provide a roadmap, elucidating both the promises and the imperatives in harnessing the potential of these cellular therapies for IDDM.

Mapping novel QTL and fine mapping of previously identified QTL associated with glucose tolerance using the collaborative cross mice

A chronic metabolic illness, type 2 diabetes (T2D) is a polygenic and multifactorial complicated disease. With an estimated 463 million persons aged 20 to 79 having diabetes, the number is expected to rise to 700 million by 2045, creating a significant worldwide health burden. Polygenic variants of diabetes are influenced by environmental variables. T2D is regarded as a silent illness that can advance for years before being diagnosed. Finding genetic markers for T2D and metabolic syndrome in groups with similar environmental exposure is therefore essential to understanding the mechanism of such complex characteristic illnesses. So herein, we demonstrated the exclusive use of the collaborative cross (CC) mouse reference population to identify novel quantitative trait loci (QTL) and, subsequently, suggested genes associated with host glucose tolerance in response to a high-fat diet. In this study, we used 539 mice from 60 different CC lines. The diabetogenic effect in response to high-fat dietary challenge was measured by the three-hour intraperitoneal glucose tolerance test (IPGTT) test after 12 weeks of dietary challenge. Data analysis was performed using a statistical software package IBM SPSS Statistic 23. Afterward, blood glucose concentration at the specific and between different time points during the IPGTT assay and the total area under the curve (AUC0-180) of the glucose clearance was computed and utilized as a marker for the presence and severity of diabetes. The observed AUC0-180 averages for males and females were 51,267.5 and 36,537.5 mg/dL, respectively, representing a 1.4-fold difference in favor of females with lower AUC0-180 indicating adequate glucose clearance. The AUC0-180 mean differences between the sexes within each specific CC line varied widely within the CC population. A total of 46 QTL associated with the different studied phenotypes, designated as T2DSL and its number, for Type 2 Diabetes Specific Locus and its number, were identified during our study, among which 19 QTL were not previously mapped. The genomic interval of the remaining 27 QTL previously reported, were fine mapped in our study. The genomic positions of 40 of the mapped QTL overlapped (clustered) on 11 different peaks or close genomic positions, while the remaining 6 QTL were unique. Further, our study showed a complex pattern of haplotype effects of the founders, with the wild-derived strains (mainly PWK) playing a significant role in the increase of AUC values.

The collagen matrix regulates the survival and function of pancreatic islets

The extracellular matrix (ECM) provides an appropriate microenvironment for many kinds of cells, including pancreatic cells. Collagens are the most abundant components of the ECM. Type I, IV, V and VI collagen has been detected in pancreatic islets, and each type plays important role in the proliferation, survival, function and differentiation of pancreatic cells. In some cases, collagens show behaviours similar to those of growth factors and regulate the biological behaviour of β cells by binding with certain growth factors, including IGFs, EGFs and FGFs. The transcriptional coactivator YAP/TAZ has been widely recognised as a mechanosensor that senses changes in the physical characteristics of the ECM and inhibition of YAP/TAZ enhances insulin production and secretion. Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterised by the destruction of insulin-producing β cells. The crosstalk between collagens and immune cells plays a key role in the development and differentiation of immune cells. Further, Supplementation with collagens during islet transplantation is a promising strategy for improving the quality of the islets. But, excessive collagen deposition results in pancreatic fibrosis and pancreatic carcinoma. Targeting inhibit Piezo, autophagy or IL-6 may reduce excessive collagen deposition-induced pancreatic fibrosis and pancreatic carcinoma. This review provides insights into the treatment of T1DM to prolong life expectancy and provides the potential targets for treating collagen deposition-induced pancreatic fibrosis and pancreatic carcinoma.

Glucose Concentration in Regulating Induced Pluripotent Stem Cells Differentiation Toward Insulin-Producing Cells

The generation of insulin-producing cells from human-induced pluripotent stem cells holds great potential for diabetes modeling and treatment. However, existing protocols typically involve incubating cells with un-physiologically high concentrations of glucose, which often fail to generate fully functional IPCs. Here, we investigated the influence of high (20 mM) versus low (5.5 mM) glucose concentrations on IPCs differentiation in three hiPSC lines. In two hiPSC lines that were unable to differentiate to IPCs sufficiently, we found that high glucose during differentiation leads to a shortage of NKX6.1+ cells that have co-expression with PDX1 due to insufficient NKX6.1 gene activation, thus further reducing differentiation efficiency. Furthermore, high glucose during differentiation weakened mitochondrial respiration ability. In the third iPSC line, which is IPC differentiation amenable, glucose concentrations did not affect the PDX1/NKX6.1 expression and differentiation efficiency. In addition, glucose-stimulated insulin secretion was only seen in the differentiation under a high glucose condition. These IPCs have higher KATP channel activity and were linked to sufficient ABCC8 gene expression under a high glucose condition. These data suggest high glucose concentration during IPC differentiation is necessary to generate functional IPCs. However, in cell lines that were IPC differentiation unamenable, high glucose could worsen the situation.

Regulation of multiple signaling pathways promotes the consistent expansion of human pancreatic progenitors in defined conditions

The unlimited expansion of human progenitor cells in vitro could unlock many prospects for regenerative medicine. However, it remains an important challenge as it requires the decoupling of the mechanisms supporting progenitor self-renewal and expansion from those mechanisms promoting their differentiation. This study focuses on the expansion of human pluripotent stem (hPS) cell-derived pancreatic progenitors (PP) to advance novel therapies for diabetes. We obtained mechanistic insights into PP expansion requirements and identified conditions for the robust and unlimited expansion of hPS cell-derived PP cells under GMP-compliant conditions through a hypothesis-driven iterative approach. We show that the combined stimulation of specific mitogenic pathways, suppression of retinoic acid signaling, and inhibition of selected branches of the TGFβ and Wnt signaling pathways are necessary for the effective decoupling of PP proliferation from differentiation. This enabled the reproducible, 2000-fold, over 10 passages and 40-45 d, expansion of PDX1+/SOX9+/NKX6-1+ PP cells. Transcriptome analyses confirmed the stabilization of PP identity and the effective suppression of differentiation. Using these conditions, PDX1+/SOX9+/NKX6-1+ PP cells, derived from different, both XY and XX, hPS cell lines, were enriched to nearly 90% homogeneity and expanded with very similar kinetics and efficiency. Furthermore, non-expanded and expanded PP cells, from different hPS cell lines, were differentiated in microwells into homogeneous islet-like clusters (SC-islets) with very similar efficiency. These clusters contained abundant β-cells of comparable functionality as assessed by glucose-stimulated insulin secretion assays. These findings established the signaling requirements to decouple PP proliferation from differentiation and allowed the consistent expansion of hPS cell-derived PP cells. They will enable the establishment of large banks of GMP-produced PP cells derived from diverse hPS cell lines. This approach will streamline SC-islet production for further development of the differentiation process, diabetes research, personalized medicine, and cell therapies.

A simple tool for the synchronous differentiation of human induced pluripotent stem cells into pancreatic progenitors

Efficient differentiation of human induced pluripotent stem cells (hiPSCs) into functional pancreatic cells holds great promise for diabetes research and treatment. However, a robust culture strategy for producing pancreatic progenitors with high homogeneity is lacking. Here, we established a simple differentiation strategy for generating synchronous iPSC-derived pancreatic progenitors via a two-step method of sequential cell synchronization using botulinum hemagglutinin (HA), an E-cadherin function-blocking agent. Of the various methods tested, the first-step synchronization method with HA exposure induces a synchronous switch from E- to N-cadherin and N- to E-cadherin expression by spatially controlling heterogeneous cell distribution, subsequently improving their competency for directed differentiation into definitive endodermal cells from iPSCs. The iPSC-derived definitive endodermal cells can efficiently generate PDX1+ and NKX6.1+ pancreatic progenitor cells in high yields. The PDX1+ and PDX1+ /NKX6.1+ cell densities showed 1.6- and 2.2-fold increases, respectively, compared with those from unsynchronized cultures. The intra-run and inter-run coefficient of variation were below 10%, indicating stable and robust differentiation across different cultures and runs. Our approach is a simple and efficient strategy to produce large quantities of differentiated cells with the highest homogeneity during multistage pancreatic progenitor differentiation, providing a potential tool for guided differentiation of iPSCs to functional insulin-producing cells.

Hippo/YAP signaling pathway: a new therapeutic target for diabetes mellitus and vascular complications

Diabetic angiopathy, which includes diabetic kidney disease (DKD), cardio-cerebrovascular disease, and diabetic retinopathy (DR) among other diseases, is one of the most common complications affecting diabetic patients. Among these, DKD, which is a major cause of morbidity and mortality, affects about 40% of diabetic patients. Similarly, DR involves retinal neovascularization and neurodegeneration as a result of chronic hyperglycemia and is the main cause of visual impairment and blindness. In addition, inflammation also promotes atherosclerosis and diabetes, with atherosclerosis-related cardiovascular diseases being often a main cause of disability or death in diabetic patients. Given that vascular diseases caused by diabetes negatively impact human health, it is therefore important to identify appropriate treatments. In this context, some studies have found that the Hippo/Yes-associated protein (YAP) pathway is a highly evolutionarily conserved protein kinase signal pathway that regulates organ growth and size through its effector signaling pathway Transcriptional co-Activator with PDZ-binding motif (TAZ) and its YAP. YAP is a key factor in the Hippo pathway. The activation of YAP regulates gluconeogenesis, thereby regulating glucose tolerance levels; silencing the YAP gene thereby prevents the formation of glomerular fibrosis. YAP can combine with TEA domain family members to regulate the proliferation and migration of retinal vascular endothelial cells (ECs), so YAP plays a prominent role in the formation and pathology of retinal vessels. In addition, YAP/TAZ activation and translocation to the nucleus promote endothelial inflammation and monocyte-EC attachment, which can increase diabetes-induced cardiovascular atherosclerosis. Hippo/YAP signaling pathway provides a potential therapeutic target for diabetic angiopathy, which can prevent the progression of diabetes to DR and improve renal fibrosis and cardio-vascular atherosclerosis.

Challenges of CRISPR/Cas-Based Cell Therapy for Type 1 Diabetes: How Not to Engineer a "Trojan Horse"

Type 1 diabetes mellitus (T1D) is an autoimmune disease caused by the destruction of insulin-producing β-cells in the pancreas by cytotoxic T-cells. To date, there are no drugs that can prevent the development of T1D. Insulin replacement therapy is the standard care for patients with T1D. This treatment is life-saving, but is expensive, can lead to acute and long-term complications, and results in reduced overall life expectancy. This has stimulated the research and development of alternative treatments for T1D. In this review, we consider potential therapies for T1D using cellular regenerative medicine approaches with a focus on CRISPR/Cas-engineered cellular products. However, CRISPR/Cas as a genome editing tool has several drawbacks that should be considered for safe and efficient cell engineering. In addition, cellular engineering approaches themselves pose a hidden threat. The purpose of this review is to critically discuss novel strategies for the treatment of T1D using genome editing technology. A well-designed approach to β-cell derivation using CRISPR/Cas-based genome editing technology will significantly reduce the risk of incorrectly engineered cell products that could behave as a "Trojan horse".

Control of stem cell renewal and fate by YAP and TAZ

Complex physiological processes control whether stem cells self-renew, differentiate or remain quiescent. Two decades of research have placed the Hippo pathway, a highly conserved kinase signalling cascade, and its downstream molecular effectors YAP and TAZ at the nexus of this decision. YAP and TAZ translate complex biological cues acting on stem cells - from mechanical forces to cellular metabolism - into genome-wide effects to mediate stem cell functions. While aberrant YAP/TAZ activity drives stem cell dysfunction in ageing, tumorigenesis and disease, therapeutic targeting of Hippo signalling and YAP/TAZ can boost stem cell activity to enhance regeneration. In this Review, we discuss how YAP/TAZ control the self-renewal, fate and plasticity of stem cells in different contexts, how dysregulation of YAP/TAZ in stem cells leads to disease, and how therapeutic modalities targeting YAP/TAZ may benefit regenerative medicine and cancer therapy.

Stem cells therapy for diabetes: from past to future

Diabetes mellitus is a chronic disease of carbohydrate metabolism characterized by uncontrolled hyperglycemia due to the body's impaired ability to produce or respond to insulin. Oral or injectable exogenous insulin and its analogs cannot mimic endogenous insulin secreted by healthy individuals, and pancreatic and islet transplants face a severe shortage of sources and transplant complications, all of which limit the widespread use of traditional strategies in diabetes treatment. We are now in the era of stem cells and their potential in ameliorating human disease. At the same time, the rapid development of gene editing and cell-encapsulation technologies has added to the wings of stem cell therapy. However, there are still many unanswered questions before stem cell therapy can be applied clinically to patients with diabetes. In this review, we discuss the progress of strategies to obtain insulin-producing cells from different types of stem cells, the application of gene editing in stem cell therapy for diabetes, as well as summarize the current advanced cell encapsulation technologies in diabetes therapy and look forward to the future development of stem cell therapy in diabetes.

Loss of ZNF148 enhances insulin secretion in human pancreatic β cells

Insulin secretion from pancreatic β cells is essential to the maintenance of glucose homeostasis. Defects in this process result in diabetes. Identifying genetic regulators that impair insulin secretion is crucial for the identification of novel therapeutic targets. Here, we show that reduction of ZNF148 in human islets, and its deletion in stem cell-derived β cells (SC-β cells), enhances insulin secretion. Transcriptomics of ZNF148-deficient SC-β cells identifies increased expression of annexin and S100 genes whose proteins form tetrameric complexes involved in regulation of insulin vesicle trafficking and exocytosis. ZNF148 in SC-β cells prevents translocation of annexin A2 from the nucleus to its functional place at the cell membrane via direct repression of S100A16 expression. These findings point to ZNF148 as a regulator of annexin-S100 complexes in human β cells and suggest that suppression of ZNF148 may provide a novel therapeutic strategy to enhance insulin secretion.

Pancreatic β-cell heterogeneity in adult human islets and stem cell-derived islets

Recent studies reported that pancreatic β-cells are heterogeneous in terms of their transcriptional profiles and their abilities for insulin secretion. Sub-populations of pancreatic β-cells have been identified based on the functionality and expression of specific surface markers. Under diabetes condition, β-cell identity is altered leading to different β-cell sub-populations. Furthermore, cell-cell contact between β-cells and other endocrine cells within the islet play an important role in regulating insulin secretion. This highlights the significance of generating a cell product derived from stem cells containing β-cells along with other major islet cells for treating patients with diabetes, instead of transplanting a purified population of β-cells. Another key question is how close in terms of heterogeneity are the islet cells derived from stem cells? In this review, we summarize the heterogeneity in islet cells of the adult pancreas and those generated from stem cells. In addition, we highlight the significance of this heterogeneity in health and disease conditions and how this can be used to design a stem cell-derived product for diabetes cell therapy.

Developments in stem cell-derived islet replacement therapy for treating type 1 diabetes

The generation of islet-like endocrine clusters from human pluripotent stem cells (hPSCs) has the potential to provide an unlimited source of insulin-producing β cells for the treatment of diabetes. In order for this cell therapy to become widely adopted, highly functional and well-characterized stem cell-derived islets (SC-islets) need to be manufactured at scale. Furthermore, successful SC-islet replacement strategies should prevent significant cell loss immediately following transplantation and avoid long-term immune rejection. This review highlights the most recent advances in the generation and characterization of highly functional SC-islets as well as strategies to ensure graft viability and safety after transplantation.

Heterogeneity of Islet Cells during Embryogenesis and Differentiation

Diabetes is caused by insufficient insulin secretion due to β-cell dysfunction and/or β-cell loss. Therefore, the restoration of functional β-cells by the induction of β-cell differentiation from embryonic stem (ES) and induced-pluripotent stem (iPS) cells, or from somatic non-β-cells, may be a promising curative therapy. To establish an efficient and feasible method for generating functional insulin-producing cells, comprehensive knowledge of pancreas development and β-cell differentiation, including the mechanisms driving cell fate decisions and endocrine cell maturation is crucial. Recent advances in single-cell RNA sequencing (scRNA-seq) technologies have opened a new era in pancreas development and diabetes research, leading to clarification of the detailed transcriptomes of individual insulin-producing cells. Such extensive high-resolution data enables the inference of developmental trajectories during cell transitions and gene regulatory networks. Additionally, advancements in stem cell research have not only enabled their immediate clinical application, but also has made it possible to observe the genetic dynamics of human cell development and maturation in a dish. In this review, we provide an overview of the heterogeneity of islet cells during embryogenesis and differentiation as demonstrated by scRNA-seq studies on the developing and adult pancreata, with implications for the future application of regenerative medicine for diabetes.

Cell-binding peptides on the material surface guide stem cell fate of adhesion, proliferation and differentiation

Human cells, especially stem cells, need to communicate and interact with extracellular matrix (ECM) proteins, which not only serve as structural components but also guide and support cell fate and properties such as cell adhesion, proliferation, survival and differentiation. The binding of the cells with ECM proteins or ECM-derived peptides via cell adhesion receptors such as integrins activates several signaling pathways that determine the cell fate, morphological change, proliferation and differentiation. The development of synthetic ECM protein-derived peptides that mimic the biological and biochemical functions of natural ECM proteins will benefit academic and clinical application. Peptides derived from or inspired by specific ECM proteins can act as agonists of each ECM protein receptor. Given that most ECM proteins function in cell adhesion via integrin receptors, many peptides have been developed that bind to specific integrin receptors. In this review, we discuss the peptide sequence, immobilization design, reaction method, and functions of several ECM protein-derived peptides. Various peptide sequences derived from mainly ECM proteins, which are used for coating or grafting on dishes, scaffolds, hydrogels, implants or nanofibers, have been developed to improve the adhesion, proliferation or differentiation of stem cells and to culture differentiated cells. This review article will help to inform the optimal choice of ECM protein-derived peptides for the development of scaffolds, implants, hydrogels, nanofibers and 2D cell culture dishes to regulate the proliferation and direct the differentiation of stem cells into specific lineages.

TEAD1 regulates cell proliferation through a pocket-independent transcription repression mechanism

The Hippo-TEAD pathway regulates cellular proliferation and function. The existing paradigm is that TEAD co-activators, YAP and TAZ, and co-repressor, VGLL4, bind to the pocket region of TEAD1 to enable transcriptional activation or repressive function. Here we demonstrate a pocket-independent transcription repression mechanism whereby TEAD1 controls cell proliferation in both non-malignant mature differentiated cells and in malignant cell models. TEAD1 overexpression can repress tumor cell proliferation in distinct cancer cell lines. In pancreatic β cells, conditional knockout of TEAD1 led to a cell-autonomous increase in proliferation. Genome-wide analysis of TEAD1 functional targets via transcriptomic profiling and cistromic analysis revealed distinct modes of target genes, with one class of targets directly repressed by TEAD1. We further demonstrate that TEAD1 controls target gene transcription in a motif-dependent and orientation-independent manner. Mechanistically, we show that TEAD1 has a pocket region-independent, direct repressive function via interfering with RNA polymerase II (POLII) binding to target promoters. Our study reveals that TEAD1 target genes constitute a mutually restricted regulatory loop to control cell proliferation and uncovers a novel direct repression mechanism involved in its transcriptional control that could be leveraged in future studies to modulate cell proliferation in tumors and potentially enhance the proliferation of normal mature cells.

Deciphering the endometrial immune landscape of RIF during the window of implantation from cellular senescence by integrated bioinformatics analysis and machine learning

Recurrent implantation failure (RIF) is an extremely thorny issue in in-vitro fertilization (IVF)-embryo transfer (ET). However, its intricate etiology and pathological mechanisms are still unclear. Nowadays, there has been extensive interest in cellular senescence in RIF, and its involvement in endometrial immune characteristics during the window of implantation (WOI) has captured scholars' growing concerns. Therefore, this study aims to probe into the pathological mechanism of RIF from cellular senescence and investigate the correlation between cellular senescence and endometrial immune characteristics during WOI based on bioinformatics combined with machine learning strategy, so as to elucidate the underlying pathological mechanisms of RIF and to explore novel treatment strategies for RIF. Firstly, the gene sets of GSE26787 and GSE111974 from the Gene Expression Omnibus (GEO) database were included for the weighted gene correlation network analysis (WGCNA), from which we concluded that the genes of the core module were closely related to cell fate decision and immune regulation. Subsequently, we identified 25 cellular senescence-associated differentially expressed genes (DEGs) in RIF by intersecting DEGs with cellular senescence-associated genes from the Cell Senescence (CellAge) database. Moreover, functional enrichment analysis was conducted to further reveal the specific molecular mechanisms by which these molecules regulate cellular senescence and immune pathways. Then, eight signature genes were determined by the machine learning method of support vector machine-recursive feature elimination (SVM-RFE), random forest (RF), and artificial neural network (ANN), comprising LATS1, EHF, DUSP16, ADCK5, PATZ1, DEK, MAP2K1, and ETS2, which were also validated in the testing gene set (GSE106602). Furthermore, distinct immune microenvironment abnormalities in the RIF endometrium during WOI were comprehensively explored and validated in GSE106602, including infiltrating immunocytes, immune function, and the expression profiling of human leukocyte antigen (HLA) genes and immune checkpoint genes. Moreover, the correlation between the eight signature genes with the endometrial immune landscape of RIF was also evaluated. After that, two distinct subtypes with significantly distinct immune infiltration characteristics were identified by consensus clustering analysis based on the eight signature genes. Finally, a "KEGG pathway-RIF signature genes-immune landscape" association network was constructed to intuitively uncover their connection. In conclusion, this study demonstrated that cellular senescence might play a pushing role in the pathological mechanism of RIF, which might be closely related to its impact on the immune microenvironment during the WOI phase. The exploration of the molecular mechanism of cellular senescence in RIF is expected to bring new breakthroughs for disease diagnosis and treatment strategies.

IGF-1R/YAP signaling pathway is involved in collagen V-induced insulin biosynthesis and secretion in rat islet INS-1 cells

PURPOSE

Type V collagen (collagen V) is one of the important components of extracellular matrix (ECM) in pancreas. We previously reported that pre-coating collagen V on the culture dishes enhanced insulin production in INS-1 rat pancreatic β cells. In this study, we investigate the underlying mechanism.

RESULTS

Insulin biosynthesis and secretion are both increased in INS-1 cells cultured on collagen V-coated dishes, accompanied by the reduced nuclear translocation of Yes-associated protein (YAP), a transcriptional co-activator. YAP, the downstream effector of Hippo signaling pathway, plays an important role in the development and function of pancreas. Inhibition of YAP activation by verteporfin further up-regulates insulin biosynthesis and secretion. Silencing large tumor suppressor (LATS), a core component of Hippo pathway which inhibits activity of YAP by phosphorylation, by siRNA transfection inhibits both insulin biosynthesis and secretion. In the present study, the protein level of insulin-like growth factor 1 receptor (IGF-1 R), detected as the upstream molecule of YAP, is reduced in the INS-1 cells cultured on the dishes coated with collagen V. The silencing of IGF-1 R by siRNA transfection further enhances insulin biosynthesis and secretion. IGF-1 treatment reduces collagen V-induced up-regulation of insulin biosynthesis and secretion, accompanying the increased nuclear YAP.

CONCLUSION

Inhibition of IGF-1 R/YAP signal pathway is involved in collagen V-induced insulin biosynthesis and secretion in INS-1 cells.

Soft substrate maintains stemness and pluripotent stem cell-like phenotype of human embryonic stem cells under defined culture conditions

Human embryonic stem cells (hESCs) are derived from the inner cell mass (ICM) of the pre-implantation blastocyst. Prior to embryo implantation, the ICM cells are surrounded by trophoblasts which have mechanical stiffness ranging from Pascal (Pa) to kilopascal (kPa). However, under in vitro conditions these cells are cultured on stiff tissue culture treated plastic plates (TCP) which have stiffness of approximately 1 gigapascal (GPa). This obvious dichotomy motivated us to investigate the fate of hESCs cultured on softer substrate, and to probe if the hESCs undergo differentiation or they retain pluripotency on soft substrates. We investigated the expression of pluripotency markers, and lineage-specific markers; we particularly looked at the expression of transcriptional coactivator YAP (Yes-associated protein), an important mediator of extracellular matrix (ECM) mechanical cues and a known downstream transducer of Hippo pathway. Downregulation of YAP has been correlated to the loss of multipotency of human mesenchymal stem cells (hMSCs) and pluripotency in mouse ESCs (mESCs); but we report that hESCs maintain their stemness on soft substrate of varying stiffness. Our findings revealed that on soft substrate hESCs express pluripotency markers and does not undergo substrate-mediated differentiation. Interestingly we show that hESCs maintained basal level of YAP expression for cell survival and proliferation, but YAP expression does not correlate directly with pluripotency in hESCs. To summarize, our results show that hESCs retain their stemness on soft substrate despite downregulation of YAP.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10616-022-00537-z.

Stepwise differentiation of functional pancreatic β cells from human pluripotent stem cells

Pancreatic β cells differentiated from stem cells provide promise for cell replacement therapy of diabetes. Human pluripotent stem cells could be differentiated into definitive endoderm, followed by pancreatic progenitors, and then subjected to endocrinal differentiation and maturation in a stepwise fashion. Many achievements have been made in making pancreatic β cells from human pluripotent stem cells in last two decades, and a couple of phase I/II clinical trials have just been initiated. Here, we overview the major progresses in differentiating pancreatic β cells from human pluripotent stem cells with the focus on recent technical advances in each differentiation stage, and briefly discuss the current limitations as well.

Differentially expressed microRNAs during the differentiation of muscle-derived stem cells into insulin-producing cells, a promoting role of microRNA-708-5p/STK4 axis

Objective

Stem cell therapy is a promising approach for diabetes via promoting the differentiation of insulin-producing cells (IPCs). This study aimed to screen the differentially expressed miRNAs (DEmiRNAs) during the differentiation of muscle-derived stem cells (MDSCs) into IPCs, and uncover the underlying function and mechanism of a specific DEmiRNA, miR-708-5p.

Methods

MDSCs were successfully isolated from the leg muscle of rats, and were induced for IPCs differentiation through a five-stage protocol. miRNA microarray assay was performed for screening DEmiRNAs during differentiation. The features of MDSCs-derived IPCs were identified by qRT-PCR, flow cytometry, and immunofluorescence staining. The targeting of STK4 by miR-708-5p was examined by luciferase assay. The protein expression of STK4, YAP1, and p-YAP1 was determined by Western blot and immunofluorescence staining.

Results

MDSCs were successfully isolated and differentiated into IPCs. A total of 12 common DEmiRNAs were obtained during five-stage differentiation. Among them, miR-708-5p that highly expressed in MDSCs-derived IPCs was selected. Overexpression of miR-708-5p upregulated some key transcription factors (Pdx1, Ngn3, Nkx2.2, Nkx6.1, Gata4, Gata6, Pax4, and Pax6) involving in IPCs differentiation, and increased insulin positive cells. In addition, STK4 was identified as the target gene of miR-708-5p. miR-708-5p overexpression downregulated the expression of STK4 and the downstream phosphorylated YAP1.

Conclusions

There were 12 DEmiRNAs involved in the differentiation of MDSCs into IPCs. miR-708-5p promoted MDSCs differentiation into IPCs probably by targeting STK4-mediated Hippo-YAP1 signaling pathway.

Characterization and reduction of non-endocrine cells accompanying islet-like endocrine cells differentiated from human iPSC

The differentiation of pancreatic endocrine cells from human pluripotent stem cells has been thoroughly investigated for their application in cell therapy against diabetes. Although non-endocrine cells are inevitable contaminating by-products of the differentiation process, a comprehensive profile of such cells is lacking. Therefore, we characterized non-endocrine cells in iPSC-derived pancreatic islet cells (iPIC) using single-cell transcriptomic analysis. We found that non-endocrine cells consist of (1) heterogeneous proliferating cells, and (2) cells with not only pancreatic traits but also liver or intestinal traits marked by FGB or AGR2. Non-endocrine cells specifically expressed FGFR2, PLK1, and LDHB. We demonstrated that inhibition of pathways involving these genes selectively reduced the number of non-endocrine cells in the differentiation process. These findings provide useful insights into cell purification approaches and contribute to the improvement of the mass production of endocrine cells for stem cell-derived cell therapy for diabetes.

TAZ promotes PDX1-mediated insulinogenesis

Transcriptional co-activator with PDZ-binding motif (TAZ) is a key mediator of the Hippo signaling pathway and regulates structural and functional homeostasis in various tissues. TAZ activation is associated with the development of pancreatic cancer in humans, but it is unclear whether TAZ directly affects the structure and function of the pancreas. So we sought to identify the TAZ function in the normal pancreas. TAZ defect caused structural changes in the pancreas, particularly islet cell shrinkage and decreased insulin production and β-cell markers expression, leading to hyperglycemia. Interestingly, TAZ physically interacted with the pancreatic and duodenal homeobox 1 (PDX1), a key insulin transcription factor, through the N-terminal domain of TAZ and the homeodomain of PDX1. TAZ deficiency decreased the DNA-binding and transcriptional activity of PDX1, whereas TAZ overexpression promoted PDX1 activity and increased insulin production even in a low glucose environment. Indeed, high glucose increased insulin production by turning off the Hippo pathway and inducing TAZ activation in pancreatic β-cells. Ectopic TAZ overexpression along with PDX1 activation was sufficient to produce insulin in non-β-cells. TAZ deficiency impaired the mesenchymal stem cell differentiation into insulin-producing cells (IPCs), whereas TAZ recovery restored normal IPCs differentiation. Compared to WT control, body weight increased in TAZ-deficient mice with age and even more with a high-fat diet (HFD). TAZ deficiency significantly exacerbated HFD-induced glucose intolerance and insulin resistance. Therefore, TAZ deficiency impaired pancreatic insulin production, causing hyperglycemia and exacerbating HFD-induced insulin resistance, indicating that TAZ may have a beneficial effect in treating insulin deficiency in diabetes.

The cell cortex as mediator of pancreatic epithelial development and endocrine differentiation

Organogenesis is the complex process of cells coordinating their own proliferation with changes to their shape, cell migration and cell-cell signaling, so that they transform into a three dimensional functional tissue, with its own custom range of differentiated cell types. Understanding when and where critical signals emanate from, and how those signals are transduced and interpreted, is the fundamental challenge of developmental biology. Here, we review recent findings regarding how progenitor cells interpret cues during pancreatic morphogenesis and how they coordinate cell fate determination. Recent evidence suggests that molecules located in the cell cortex play a crticial role in determining cellular behavior during pancreatic morphogenesis. Specifically, we find that control of cell adhesion, polarity, and constriction are all integral to both initiation of epithelial development and to later cell differentiation. Here, we review key molecules that coordinate these processes and suggest that the cell cortex acts as a signaling center that relays cues during pancreas development.

Mitogen Synergy: An Emerging Route to Boosting Human Beta Cell Proliferation

Decreased number and function of beta cells are a key aspect of diabetes mellitus (diabetes), a disease that remains an onerous global health problem. Means of restoring beta cell mass are urgently being sought as a potential cure for diabetes. Several strategies, such as de novo beta cell derivation via pluripotent stem cell differentiation or mature somatic cell transdifferentiation, have yielded promising results. Beta cell expansion is another promising strategy, rendered challenging by the very low proliferative capacity of beta cells. Many effective mitogens have been identified in rodents, but the vast majority do not have similar mitogenic effects in human beta cells. Extensive research has led to the identification of several human beta cell mitogens, but their efficacy and specificity remain insufficient. An approach based on the simultaneous application of several mitogens has recently emerged and can yield human beta cell proliferation rates of up to 8%. Here, we discuss recent advances in restoration of the beta cell population, focusing on mitogen synergy, and the contribution of RNA-sequencing (RNA-seq) to accelerating the elucidation of signaling pathways in proliferating beta cells and the discovery of novel mitogens. Together, these approaches have taken beta cell research up a level, bringing us closer to a cure for diabetes.

Tissue geometry drives deterministic organoid patterning

Epithelial organoids are stem cell–derived tissues that approximate aspects of real organs, and thus they have potential as powerful tools in basic and translational research. By definition, they self-organize, but the structures formed are often heterogeneous and irreproducible, which limits their use in the lab and clinic. We describe methodologies for spatially and temporally controlling organoid formation, thereby rendering a stochastic process more deterministic. Bioengineered stem cell microenvironments are used to specify the initial geometry of intestinal organoids, which in turn controls their patterning and crypt formation. We leveraged the reproducibility and predictability of the culture to identify the underlying mechanisms of epithelial patterning, which may contribute to reinforcing intestinal regionalization in vivo. By controlling organoid culture, we demonstrate how these structures can be used to answer questions not readily addressable with the standard, more variable, organoid models.

Stem Cell-Derived β Cells: A Versatile Research Platform to Interrogate the Genetic Basis of β Cell Dysfunction

Pancreatic β cell dysfunction is a central component of diabetes progression. During the last decades, the genetic basis of several monogenic forms of diabetes has been recognized. Genome-wide association studies (GWAS) have also facilitated the identification of common genetic variants associated with an increased risk of diabetes. These studies highlight the importance of impaired β cell function in all forms of diabetes. However, how most of these risk variants confer disease risk, remains unanswered. Understanding the specific contribution of genetic variants and the precise role of their molecular effectors is the next step toward developing treatments that target β cell dysfunction in the era of personalized medicine. Protocols that allow derivation of β cells from pluripotent stem cells, represent a powerful research tool that allows modeling of human development and versatile experimental designs that can be used to shed some light on diabetes pathophysiology. This article reviews different models to study the genetic basis of β cell dysfunction, focusing on the recent advances made possible by stem cell applications in the field of diabetes research.