Wnt signaling in stem cells during development and cell lineage specification

Chaperone-mediated autophagy sustains pericyte stemness necessary for brain tissue homeostasis

INTRODUCTION

Pericytes (PCs) are mural cells exhibiting some mesenchymal stem cell (MSC) properties and contribute to tissue regeneration after injury. We have previously shown that glioblastoma cancer cells induce in PCs, a pathogenic upregulation of chaperone-mediated autophagy (CMA) which modulates immune functions and MSC-like properties to support tumor growth.

OBJECTIVES

The aim of the study was to interrogate the role of CMA-regulated MSC properties in PCs in the context of tissue repair during inflammation triggered by a demyelinating injury.

METHODS

Studies of RNA-seq were done PCs with (WT) and without (LAMP-2A KO) CMA. Cell characterization related to stemness, lineage and morphology was done in WT and KO PCs. Secretome analysis and cell differentiation assay using the supernatants from CMA-efficient and deficient PCs cultures was done in mesenchymal cells. Inflammatory response of brain cells was assessed with WT and KO PCs secretome. To corroborate in vitro results, CMA modulation in response to inflammation in PCs and tissue repair markers were measured in the lesion areas of a demyelination mouse model and correlated with the tissue reparation after intravenous PC administration. An inflammatory mediator was used to study effects on PC-CMA activity.

RESULTS

We found that inflammatory mediators such as IFNγ downregulate CMA in PCs, suppressing PC stemness and promoting a pro-inflammatory secretome. Restoration of PC CMA activity during inflammation maintains PC MSC properties and induces an MSC-like proteome which decreases inflammation and promotes tissue repair. We identified secreted proteins involved in regenerative and protective processes, and therefore, necessary to restore brain tissue homeostasis after inflammation induced by a demyelinating injury.

CONCLUSION

we show that manipulation of CMA activity in host PCs could be a useful therapeutical approach in the context of brain inflammation, which might be extended to other diseases where the pericyte has a key role in response to inflammation.

Mitochondrial fission regulates midgut muscle assembly and tick feeding capacity

Ticks ingest over 100 times their body weight in blood. As the primary tissue for blood storage and digestion, the tick midgut's regulation in response to this substantial blood volume remains unclear. Here, we show that blood intake triggers stem cell proliferation and mitochondrial fission in the midgut of Haemaphysalis longicornis. While inhibiting stem cell proliferation does not impact feeding behavior, disruption of mitochondrial fission impairs tick feeding capacity. Mitochondrial fission mediated by dynamin 2 (DNM2) regulates ATP generation, which in turn influences the expression of the tropomyosin-anchoring subunit troponin T (TNT). Knockdown of TNT disrupts muscle fiber assembly, hindering midgut enlargement and contraction, thereby preventing blood ingestion. These findings underscore the indispensable role of musculature in facilitating midgut expansion during feeding in ticks.

Nanoparticle-Mediated Embryotoxicity: Mechanisms of Chemical Toxicity and Implications for Biological Development

Nanoparticles, defined by their nanoscale dimensions and unique physicochemical properties, are widely utilized in healthcare, electronics, environmental sciences, and consumer products. However, increasing evidence of their potential embryotoxic effects during pregnancy underscores the need for a molecular-level understanding of their interactions during embryonic development. Nanoparticles such as titanium dioxide, silver, cerium oxide, copper oxide, and quantum dots can cross the placental barrier and interfere with crucial developmental processes. At the molecular level, they disrupt signaling pathways like Wnt and Hedgehog, induce oxidative stress and inflammation, and cause genotoxic effects, all critical during sensitive phases, such as organogenesis. Furthermore, these nanoparticles interact directly with cellular components, including DNA, proteins, and lipids, impairing cellular function and viability. Innovative strategies to mitigate nanoparticle toxicity, such as surface modifications and incorporation of biocompatible coatings, are discussed as potential solutions to reduce adverse molecular interactions. Various laboratory animal models used to investigate nanoparticle-induced embryotoxicity are evaluated for their efficacy and limitations, providing insights into their applicability for understanding these effects. This Account examines the molecular mechanisms by which nanoparticles compromise embryonic development and emphasizes the importance of designing safer nanoparticles to minimize maternal-fetal exposure risks, particularly in biomedical applications.

Radiation-Induced Tissue Regeneration: Pathways, Mechanisms, and Therapeutic Potential

This article explores the paradoxic nature of radiation as both a destructive and regenerative force. The article examines the interplay of signaling pathways, immune modulation, and stem cells in tissue regeneration post radiation, emphasizing the roles of key pathways like Wnt, Hedgehog, Notch, and p53. It highlights advancements in low-dose radiation therapy, extracellular vesicles, and stem cell-based interventions. Furthermore, the immune system's dual role in repair and damage is dissected, along with technologies such as artificial intelligence and bioengineered scaffolds that enhance therapeutic outcomes. The article offers a roadmap for integrating therapeutic innovation with regenerative medicine to improve patient outcomes.

Proteomics Analysis of Porcine Endometrial Cell-Derived Extracellular Vesicles Involved in Embryo Attachment

Maternal-embryo interactions play a critical role in early mammalian development, with extracellular vesicles (EVs) playing a key role in intercellular communication. Recent studies have focused on the mechanisms by which maternal-derived factors, such as RNA, proteins, and metabolites influence gap junctions, EVs, and direct cell-to-cell interactions, contributing to embryonic development. In this study, using a proteomics approach, we investigated the impact of EVs secreted from porcine endometrial cells (pEECs) and their protein cargoes on embryonic development. We characterized EVs isolated from pEECs (pEEC-EVs) during the diestrus stage using a nanoparticle tracking analysis and cryo-transmission electron microscopy. Furthermore, the effects of pEEC-EVs with or without hormone treatment on the in vitro attachment of hatched blastocysts were evaluated. The attachment rate of porcine embryos was significantly higher for pEEC-EVs in the hormone treatment group than the control group (23.0 ± 1.7% versus 36.9 ± 1.9% for control and pEEC-EVs, respectively). Furthermore, hormone treatment altered the expression of proteins involved in cellular organization, protein transport, and immunity. Proteomic analysis revealed distinct biological processes between groups: control EVs supported cytoskeletal organization and adhesion, while hormone-treated EVs were enriched in protein transport, immune regulation, and stress response pathways. Key signaling pathways, including VEGFA-VEGFR2, focal adhesion, and TGF-β, were modulated, influencing implantation and embryogenesis. EVs play a crucial role in maternal-embryo interactions, optimizing implantation conditions and supporting embryo-derived stem cell establishment. These findings enhance our understanding of EV-mediated communication and suggest potential applications for improving reproductive health and assisted reproductive technologies.

Selective activation of FZD2 and FZD7 reveals non-redundant function during mesoderm differentiation

During gastrulation, Wnt-β-catenin signaling dictates lineage bifurcation generating different mesoderm cell types. However, the specific role of Wnt receptors in mesoderm specification remains elusive. Using selective Frizzled (FZD) and LRP5/6 antibody-based agonists, we examined FZD receptors' function during directed mesoderm differentiation of human pluripotent stem cells (hPSCs). We found that FZD2 and FZD7 receptors are expressed at the membrane of hPSCs and that their activation triggers β-catenin signaling with different kinetics, thereby influencing mesoderm patterning choices. Specifically, FZD7 activation enhances both paraxial and lateral mesoderm differentiation, whereas FZD2 activation favors paraxial mesoderm. Mechanistically, FZD2 activation promotes sustained Wnt-β-catenin levels, guiding hPSCs differentiation toward paraxial mesoderm, while blocking lateral mesoderm. In contrast, FZD7 activation kinetics display similar initial activation but more dampening of β-catenin signaling, permitting lateral mesoderm induction in addition to paraxial mesoderm specification. Our findings reveal non-redundant roles for FZD2 and FZD7 in mesoderm specification, offering leverage for precise directed differentiation outcomes.

Protein Coronation-Induced Cancer Staging-Dependent Multilevel Cytotoxicity: An All-Humanized Study in Blood Vessel Organoids

The protein corona effect refers to the phenomenon wherein nanomaterials in the bloodstream are coated by serum proteins, yet how protein coronated nanomaterials interact with blood vessels and its toxicity implications remain poorly understood. In this study, we investigated protein corona-related vessel toxicity by using an all-humanized assay integrating blood vessel organoids and patient-derived serum. Initially, we screened various nanomaterials to discern how parameters including size, morphology, hydrophobicity, surface charge, and chirality-dependent protein corona difference influence their uptake by vessel organoids. For nanomaterials showing substantial differences in vessel uptake, their protein corona was analyzed by using label-free mass spectra. Our findings revealed the involvement of cancer staging-related cytoskeleton components in mediating preferential uptake by cells, including endothelial and mural cells. Additionally, a transcriptome study was conducted to elucidate the influence of nanomaterials. We confirmed that protein coronated nanomaterials provoke remodeling at both transcriptional and translational levels, impacting pathways such as PI3K-Akt/Hippo/Wnt, and membraneless organelle integrity, respectively. Our study further demonstrated that the remodeling potential of patient-derived protein coronated nanomaterials can be harnessed to synergize with antiangiogenesis therapeutics to improve the outcomes. We anticipate that this study will provide guidance for the safe use of nanomedicine in the future.

Antisense mediated blockade of Dickkopf 1 attenuates tumor survival, metastases and bone damage in experimental osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy. The canonical Wnt inhibitor Dickkopf-1 (Dkk-1) has been implicated in bone destruction, tumor survival and metastases during OS. We examined the role of Dkk-1 in OS disease progression and explored strategies for targeting its activity. Dkk-1 enhances OS survival by amplifying a non-canonical Wnt pathway that upregulates aldehyde dehydrogenase 1A1. Targeting of Dkk-1 transcription with a vivo morpholino (DkkMo) reduced OS survival and enhanced osteogenic activity of OS in vitro. DkkMo as a single agent slowed tumor expansion, increased tumor necrosis, inhibited metastases and preserved bone in a PDX model of OS. DkkMo also reduced the frequency of dividing tumor cells and reinitiated a regenerative osteogenic phenotype in tumors and stroma while reducing infiltration of inflammatory cells. These findings indicate that DkkMo has the potential to safely target osteosarcoma growth, survival, metastases and bone destruction.

Targeting WNT5B and WNT10B in osteosarcoma

WNT signaling regulates osteosarcoma proliferation. However, there is controversy in the field of osteosarcoma as to whether WNT signaling is pro- or anti-tumorigenic. WNT-targeting therapeutics, both activators and inhibitors, are compared. WNT5B, a β-catenin-independent ligand, and WNT10B, a β-catenin-dependent WNT ligand, are each expressed in osteosarcomas, but they are not expressed in the same tumors. Furthermore, WNT10B and WNT5B regulate different histological subtypes of osteosarcomas. Using WNT signaling modulators as therapeutics may depend on the WNT ligand and/or the activated signaling pathway.

Get your receptors in a knot with new Wnt signaling agonists

Pharmacological modulation of the Wnt/β-catenin signaling pathway holds promises for both basic research and therapeutic applications. In this issue of Cell Chemical Biology, Kschonsak et al.1 engineered knotted peptides that promote Wnt signaling by targeting ZNRF3 and serve as pharmacological tools for studying Wnt biology and supporting organoid growth.

METTL3-dependent m6A modification of PSEN1 mRNA regulates craniofacial development through the Wnt/β-catenin signaling pathway

Craniofacial malformations, often associated with syndromes, are prevalent birth defects. Emerging evidence underscores the importance of m6A modifications in various bioprocesses such as stem cell differentiation, tissue development, and tumorigenesis. Here, in vivo, experiments with zebrafish models revealed that mettl3-knockdown embryos at 144 h postfertilization exhibited aberrant craniofacial features, including altered mouth opening, jaw dimensions, ethmoid plate, tooth formation and hypoactive behavior. Similarly, low METTL3 expression inhibited the proliferation and migration of BMSCs, HEPM cells, and DPSCs. Loss of METTL3 led to reduced mRNA m6A methylation and PSEN1 expression, impacting craniofacial phenotypes. Co-injection of mettl3 or psen1 mRNA rescued the level of Sox10 fusion protein, promoted voluntary movement, and mitigated abnormal craniofacial phenotypes induced by mettl3 knockdown in zebrafish. Mechanistically, YTHDF1 enhanced the mRNA stability of m6A-modified PSEN1, while decreased METTL3-mediated m6A methylation hindered β-catenin binding to PSEN1, suppressing Wnt/β-catenin signaling. Pharmacological activation of the Wnt/β-catenin pathway partially alleviated the phenotypes of mettl3 morphant and reversed the decreases in cell proliferation and migration induced by METTL3 silencing. This study elucidates the pivotal role of METTL3 in craniofacial development via the METTL3/YTHDF1/PSEN1/β-catenin signaling axis.

Stem Cells: Engines of Plant Growth and Development

The development of both animals and plants relies on populations of pluripotent stem cells that provide the cellular raw materials for organ and tissue formation. Plant stem cell reservoirs are housed at the shoot and root tips in structures called meristems, with the shoot apical meristem (SAM) continuously producing aerial leaf, stem, and flower organs throughout the life cycle. Thus, the SAM acts as the engine of plant development and has unique structural and molecular features that allow it to balance self-renewal with differentiation and act as a constant source of new cells for organogenesis while simultaneously maintaining a stem cell reservoir for future organ formation. Studies have identified key roles for intercellular regulatory networks that establish and maintain meristem activity, including the KNOX transcription factor pathway and the CLV-WUS stem cell feedback loop. In addition, the plant hormones cytokinin and auxin act through their downstream signaling pathways in the SAM to integrate stem cell activity and organ initiation. This review discusses how the various regulatory pathways collectively orchestrate SAM function and touches on how their manipulation can alter stem cell activity to improve crop yield.

Wnt Signaling in Brain Tumors: A Challenging Therapeutic Target

The involvement of Wnt signaling in normal tissue homeostasis and disease has been widely demonstrated over the last 20 years. In particular, dysregulation of Wnt pathway components has been suggested as a relevant hallmark of several neoplastic malignancies, playing a role in cancer onset, progression, and response to treatments. In this review, we summarize the current knowledge on the instructions provided by Wnt signaling during organogenesis and, particularly, brain development. Moreover, we recapitulate the most relevant mechanisms through which aberrant Wnt pathway activation may impact on brain tumorigenesis and brain tumor aggressiveness, with a particular focus on the mutual interdependency existing between Wnt signaling components and the brain tumor microenvironment. Finally, the latest anti-cancer therapeutic approaches employing the specific targeting of Wnt signaling are extensively reviewed and discussed. In conclusion, here we provide evidence that Wnt signaling, due to its pleiotropic involvement in several brain tumor features, may represent a relevant target in this context, although additional efforts will be needed to: (i) demonstrate the real clinical impact of Wnt inhibition in these tumors; (ii) overcome some still unsolved concerns about the potential systemic effects of such approaches; (iii) achieve efficient brain penetration.