Maternal diabetes induces senescence and neural tube defects sensitive to the senomorphic rapamycin

Brain development and bioenergetic changes

Bioenergetics describe the biochemical processes responsible for energy supply in organisms. When these changes become dysregulated in brain development, multiple neurodevelopmental diseases can occur, implicating bioenergetics as key regulators of neural development. Historically, the discovery of disease processes affecting individual stages of brain development has revealed critical roles that bioenergetics play in generating the nervous system. Bioenergetic-dependent neurodevelopmental disorders include neural tube closure defects, microcephaly, intellectual disability, autism spectrum disorders, epilepsy, mTORopathies, and oncogenic processes. Developmental timing and cell-type specificity of these changes determine the long-term effects of bioenergetic disease mechanisms on brain form and function. Here, we discuss key metabolic regulators of neural progenitor specification, neuronal differentiation (neurogenesis), and gliogenesis. In general, transitions between glycolysis and oxidative phosphorylation are regulated in early brain development and in oncogenesis, and reactive oxygen species (ROS) and mitochondrial maturity play key roles later in differentiation. We also discuss how bioenergetics interface with the developmental regulation of other key neural elements, including the cerebrospinal fluid brain environment. While questions remain about the interplay between bioenergetics and brain development, this review integrates the current state of known key intersections between these processes in health and disease.

Role of cellular senescence in inflammation and regeneration

Cellular senescence is the state in which cells undergo irreversible cell cycle arrest and acquire diverse phenotypes. It has been linked to chronic inflammation and fibrosis in various organs as well as to individual aging. Therefore, eliminating senescent cells has emerged as a potential target for extending healthy lifespans. Cellular senescence plays a beneficial role in many biological processes, including embryonic development, wound healing, and tissue regeneration, which is mediated by the activation of stem cells. Therefore, a comprehensive understanding of cellular senescence, including both its beneficial and detrimental effects, is critical for developing safe and effective treatment strategies to target senescent cells. This review provides an overview of the biological and pathological roles of cellular senescence, with a particular focus on its beneficial or detrimental functions among its various roles.

Piezoelectric Catalysis Induces Tumor Cell Senescence to Boost Chemo-Immunotherapy

Cellular senescence, a vulnerable state of growth arrest, has been regarded as a potential strategy to weaken the resistance of tumor cells, leading to dramatic improvements in treatment efficacy. However, a selective and efficient strategy for inducing local tumor cellular senescence has not yet been reported. Herein, piezoelectric catalysis is utilized to reduce intracellular NAD+ to NADH for local tumor cell senescence for the first time. In detail, a biocompatible nanomedicine (BTO/Rh-D@M) is constructed by wrapping the piezoelectric BaTiO3/(Cp*RhCl2)2 (BTO/Rh) and doxorubicin (DOX) in the homologous cytomembrane with tumor target. After tumors are stimulated by ultrasound, negative and positive charges are generated on the BTO/Rh by piezoelectric catalysis, which reduce the intracellular NAD+ to NADH for cellular senescence and oxidize H2O to reactive oxygen species (ROS) for mitochondrial damage. Thus, the therapeutic efficacy of tumor immunogenic cell death-induced chemo-immunotherapy is boosted by combining cellular senescence, DOX, and ROS. The results indicate that 23.9% of the piezoelectric catalysis-treated tumor cells senesced, and solid tumors in mice disappeared completely after therapy. Collectively, this study highlights a novel strategy to realize cellular senescence utilizing piezoelectric catalysis and the significance of inducing tumor cellular senescence to improve therapeutic efficacy.

Small Molecule Activators of Mitochondrial Fusion Prevent Congenital Heart Defects Induced by Maternal Diabetes

Most congenital heart defect (CHD) cases are attributed to nongenetic factors; however, the mechanisms underlying nongenetic factor-induced CHDs are elusive. Maternal diabetes is one of the nongenetic factors, and this study aimed to determine whether impaired mitochondrial fusion contributes to maternal diabetes-induced CHDs and if mitochondrial fusion activators, teriflunomide and echinacoside, could reduce CHD incidence in diabetic pregnancy. We demonstrated maternal diabetes-activated FoxO3a increases miR-140 and miR-195, which in turn represses Mfn1 and Mfn2, leading to mitochondrial fusion defects and CHDs. Two mitochondrial fusion activators are effective in preventing CHDs in diabetic pregnancy.

Diabetes Mellitus and Pregnancy: An Insight into the Effects on the Epigenome

Worldwide, diabetes mellitus represents a growing health problem. If it occurs during pregnancy, it can increase the risk of various abnormalities in early and advanced life stages of exposed individuals due to fetal programming occurring in utero. Studies have determined that maternal conditions interfere with the genotypes and phenotypes of offspring. Researchers are now uncovering the mechanisms by which epigenetic alterations caused by diabetes affect the expression of genes and, therefore, the development of various diseases. Among the numerous possible epigenetic changes in this regard, the most studied to date are DNA methylation and hydroxymethylation, as well as histone acetylation and methylation. This review article addresses critical findings in epigenetic studies involving diabetes mellitus, including variations reported in the expression of specific genes and their transgenerational effects.

MicroRNA-322 overexpression reduces neural tube defects in diabetic pregnancies

BACKGROUND

Hyperglycemia from pregestational diabetes mellitus induces neural tube defects in the developing fetus. Folate supplementation is the only effective way to prevent neural tube defects; however, some cases of neural tube defects are resistant to folate. Excess folate has been linked to higher maternal cancer risk and infant allergy. Therefore, additional interventions are needed. Understanding the mechanisms underlying maternal diabetes mellitus-induced neural tube defects can identify potential targets for preventing such defects. Despite not yet being in clinical use, growing evidence suggests that microRNAs are important intermediates in embryonic development and can serve as both biomarkers and drug targets for disease intervention. Our previous studies showed that maternal diabetes mellitus in vivo activates the inositol-requiring transmembrane kinase/endoribonuclease 1α (IRE1α) in the developing embryo and that a high glucose condition in vitro reduces microRNA-322 (miR-322) levels. IRE1α is an RNA endonuclease; however, it is unknown whether IRE1α targets and degrades miR-322 specifically or whether miR-322 degradation leads to neural tube defects via apoptosis. We hypothesize that IRE1α can inhibit miR-322 in maternal diabetes mellitus-induced neural tube defects and that restoring miR-322 expression in developing neuroepithelium ameliorates neural tube defects.

OBJECTIVE

This study aimed to identify potential targets for preventing maternal diabetes mellitus-induced neural tube defects and to investigate the roles and relationship of a microRNA and an RNA endonuclease in mouse embryos exposed to maternal diabetes mellitus.

STUDY DESIGN

To determine whether miR-322 reduction is necessary for neural tube defect formation in pregnancies complicated by diabetes mellitus, male mice carrying a transgene expressing miR-322 were mated with nondiabetic or diabetic wide-type female mice to generate embryos with or without miR-322 overexpression. At embryonic day 8.5 when the neural tube is not yet closed, embryos were harvested for the assessment of 3 miR-322 transcripts (primary, precursor, and mature miR-322), tumor necrosis factor receptor-associated factor 3 (TRAF3), and neuroepithelium cell survival. Neural tube defect incidences were determined in embryonic day 10.5 embryos when the neural tube should be closed if there is no neural tube defect formation. To identify which miR-322 transcript is affected by maternal diabetes mellitus and high glucose conditions, 3 miR-322 transcripts were assessed in embryos from dams with or without diabetes mellitus and in C17.2 mouse neural stem cells treated with different concentrations of glucose and at different time points. To determine whether the endonuclease IRE1α targets miR-322, small interfering RNA knockdown of IRE1α or overexpression of inositol-requiring transmembrane kinase/endoribonuclease 1α by DNA plasmid transfection was used to determine the effect of IRE1α deficiency or overexpression on miR-322 expression. RNA immunoprecipitation was performed to reveal the direct targets of inositol-requiring transmembrane kinase/endoribonuclease 1α.

RESULTS

Maternal diabetes mellitus suppressed miR-322 expression in the developing neuroepithelium. Restoring miR-322 expression in the neuroepithelium blocked maternal diabetes mellitus-induced caspase-3 and caspase-8 cleavage and cell apoptosis, leading to a neural tube defect reduction. Reversal of maternal diabetes mellitus-inhibited miR-322 via transgenic overexpression prevented TRAF3 up-regulation in embryos exposed to maternal diabetes mellitus. Activated IRE1α acted as an endonuclease and degraded precursor miR-322, resulting in mature miR-322 reduction.

CONCLUSION

This study supports the crucial role of the IRE1α-microRNA-TRAF3 circuit in the induction of neuroepithelial cell apoptosis and neural tube defect formation in pregnancies complicated by diabetes mellitus and identifies IRE1α and miR-322 as potential targets for preventing maternal diabetes mellitus-induced neural tube defects.

Cisplatin Provokes Peripheral Nociception and Neuronal Features of Therapy-Induced Senescence and Calcium Dysregulation in Rats

Therapy-Induced Senescence (TIS) is a form of senescence that is typically described in malignant cells in response to the exposure of cancer chemotherapy or radiation but can also be precipitated in non-malignant cells. TIS has been shown to contribute to the development of several cancer therapy-related adverse effects; however, evidence on its role in mediating chemotherapy-induced neurotoxicity, such as Chemotherapy-induced Peripheral Neuropathy (CIPN), is limited. We here show that cisplatin treatment over two cycles (cumulative dose of 23 mg/kg) provoked mechanical allodynia and thermal hyperalgesia in Sprague-Dawley rats. Isolation of dorsal root ganglia (DRG) from the cisplatin-treated rats demonstrated robust SA-β-gal upregulation at both day 8 (after the first cycle) and day 18 (after the second cycle), decreased lmnb1 expression, increased expression of cdkn1a and cdkn2a, and of several factors of the Senescence-associated Secretory Phenotype (SASP) (Il6, Il1b, and mmp9). Moreover, single-cell calcium imaging of cultured DRGs revealed a significant increase in terms of the magnitude of KCl-evoked calcium responses in cisplatin-treated rats compared to vehicle-treated rats. No significant change was observed in terms of the magnitude of capsaicin-evoked calcium responses in cisplatin-treated rats compared to vehicle-treated rats but with decreased area under the curve of the responses in cisplatin-treated rats. Further evidence to support the contribution of TIS to therapy adverse effects is required but should encourage the use of senescence-modulating agents (senotherapeutics) as novel palliative approaches to mitigate chemotherapy-induced neurotoxicity.

Targeting therapy-induced senescence as a novel strategy to combat chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a treatment-limiting adverse effect of anticancer therapy that complicates the lifestyle of many cancer survivors. There is currently no gold-standard for the assessment or management of CIPN. Subsequently, understanding the underlying mechanisms that lead to the development of CIPN is essential for finding better pharmacological therapy. Therapy-induced senescence (TIS) is a form of senescence that is triggered in malignant and non-malignant cells in response to the exposure to chemotherapy. Recent evidence has also suggested that TIS develops in the dorsal root ganglia of rodent models of CIPN. Interestingly, several components of the senescent phenotype are commensurate with the currently established primary processes implicated in the pathogenesis of CIPN including mitochondrial dysfunction, oxidative stress, and neuroinflammation. In this article, we review the literature that supports the hypothesis that TIS could serve as a holistic mechanism leading to CIPN, and we propose the potential for investigating senotherapeutics as means to mitigate CIPN in cancer survivors.

Rutin is a potent senomorphic agent to target senescent cells and can improve chemotherapeutic efficacy

Aging is a major risk factor for most chronic disorders, for which cellular senescence is one of the central hallmarks. Senescent cells develop the pro-inflammatory senescence-associated secretory phenotype (SASP), which significantly contributes to organismal aging and age-related disorders. Development of senotherapeutics, an emerging class of therapeutic agents to target senescent cells, allows to effectively delay aging and alleviate chronic pathologies. Here we report preliminary outputs from screening of a natural medicinal agent (NMA) library for senotherapeutic candidates and validated several agents with prominent potential as senomorphics. Rutin, a phytochemical constituent found in a number of plants, showed remarkable capacity in targeting senescent cells by dampening expression of the full spectrum SASP. Further analysis indicated that rutin restrains the acute stress-associated phenotype (ASAP) by specifically interfering with the interactions of ATM with HIF1α, a master regulator of cellular and systemic homeostasis activated during senescence, and of ATM with TRAF6, part of a key signaling axis supporting the ASAP development toward the SASP. Conditioned media produced by senescent stromal cells enhanced the malignant phenotypes of prostate cancer cells, including in vitro proliferation, migration, invasion, and more importantly, chemoresistance, while rutin remarkably downregulated these gain-of-functions. Although classic chemotherapy reduced tumor progression, the treatment outcome was substantially improved upon combination of a chemotherapeutic agent with rutin. Our study provides a proof of concept for rutin as an emerging natural senomorphic agent, and presents an effective therapeutic avenue for alleviating age-related pathologies including cancer.

Gastruloids - a minimalistic model to study complex developmental metabolism

Metabolic networks are well placed to orchestrate the coordination of multiple cellular processes associated with embryonic development such as cell growth, proliferation, differentiation and cell movement. Here, we discuss the advantages that gastruloids, aggregates of mammalian embryonic stem cells that self-assemble a rudimentary body plan, have for uncovering the instructive role of metabolic pathways play in directing developmental processes. We emphasise the importance of using such reductionist systems to link specific pathways to defined events of early mammalian development and their utility for obtaining enough material for metabolomic studies. Finally, we review the ways in which the basic gastruloid protocol can be adapted to obtain specific models of embryonic cell types, tissues and regions. Together, we propose that gastruloids are an ideal system to rapidly uncover new mechanistic links between developmental signalling pathways and metabolic networks, which can then inform precise in vivo studies to confirm their function in the embryo.

High glucose-increased miR-200c contributes to cellular senescence and DNA damage in neural stem cells

BACKGROUND

Maternal diabetes increases the risk for neural tube defects (NTDs). It is unclear if miRNAs, senescence, and DNA damage are involved in this process. In this study, we used neural stem cells as an in vitro proxy of embryonic neuroepithelium to investigate whether high glucose triggers neural stem cell senescence and DNA damage by upregulating miR-200c, which may be responsible for NTDs.

METHODS

C17.2 neural stem cells were cultured with normal glucose (5 mM) or high glucose (≥16.7 mM) at different doses and time points for detecting miR-200c levels, markers of senescence and DNA damage. Neural stem cells were exposed to antioxidant SOD1 mimetic Tempol and high glucose for 48 h to test roles of oxidative stress on the miR-200c, senescence, and DNA damage levels. An miR-200c mimic and an inhibitor were transfected into neural stem cells to increase or decrease miR-200c activities.

RESULTS

High glucose upregulated miR-200c in neural stem cells. A time course study of the effect of high glucose revealed that miR-200c initially increased at 12 h and reached its zenith at 18 h. Tempol reduced miR-200c levels caused by high glucose. High glucose induced markers of senescence and DNA damage in neural stem cells. Tempol abolished high glucose-induced markers of senescence and DNA damage. The miR-200c inhibitor suppressed high glucose-induced markers of senescence and DNA damage. Treatment with miR-200c mimic imitates high glucose-induced markers of senescence and DNA damage.

CONCLUSIONS

We show that high glucose increases miR-200c, which contributes to cellular senescence and DNA damage in neural stem cells and provides a potential pathway for maternal diabetes-induced neural tube defects.

Maternal metabolism influences neural tube closure

Changes in maternal nutrient availability due to diet or disease significantly increase the risk of neural tube defects (NTDs). Because the incidence of metabolic disease continues to rise, it is urgent that we better understand how altered maternal nutrient levels can influence embryonic neural tube development. Furthermore, primary neurulation occurs before placental function during a period of histiotrophic nutrient exchange. In this review we detail how maternal metabolites are transported by the yolk sac to the developing embryo. We discuss recent advances in understanding how altered maternal levels of essential nutrients disrupt development of the neuroepithelium, and identify points of intersection between metabolic pathways that are crucial for NTD prevention.

Senescence: a double-edged sword in beta-cell health and failure?

Cellular senescence is a complex process marked by permanent cell-cycle arrest in response to a variety of stressors, and acts as a safeguard against the proliferation of damaged cells. Senescence is not only a key process underlying aging and development of many diseases, but has also been shown to play a vital role in embryogenesis as well as tissue regeneration and repair. In context of the pancreatic beta-cells, that are essential for maintaining glucose homeostasis, replicative senescence is responsible for the age-related decline in regenerative capacity. Stress induced premature senescence is also a key early event underlying beta-cell failure in both type 1 and type 2 diabetes. Targeting senescence has therefore emerged as a promising therapeutic avenue for diabetes. However, the molecular mechanisms that mediate the induction of beta-cell senescence in response to various stressors remain unclear. Nor do we know if senescence plays any role during beta-cell growth and development. In this perspective, we discuss the significance of senescence in beta-cell homeostasis and pathology and highlight emerging directions in this area that warrant our attention.

Senescent cells in the brain and where to find them

Cellular senescence is a process in which cells change their characteristic phenotype in response to stress and enter a state of prolonged cell cycle arrest accompanied by a distinct secretory phenotype. Cellular senescence has both beneficial and detrimental outcomes. With age, senescent cells progressively accumulate in tissues and might be the bridge connecting ageing to many age-related pathologies. In recent years, evidence emerged supporting the accumulation of brain senescent cells during neurological disorders and ageing. Here, we will discuss the different brain cell populations that exhibit a senescent phenotype. Subsequently, we will explore several senolytic strategies which have been developed to eliminate senescent cells. Finally, we will examine their potential to directly eliminate these senescent brain cells.

Cellular senescence and developmental defects

Cellular senescence is a distinct state that is frequently induced in response to ageing and stress. Yet studies have also uncovered beneficial functions in development, repair and regeneration. Current opinion therefore suggests that timely and controlled induction of senescence can be beneficial, while misregulation of the senescence program, either through mis-timed activation, or chronic accumulation of senescent cells, contributes to many disease states and the ageing process. Whether atypical activation of senescence plays a role in the pathogenesis of developmental defects has been relatively underexplored. Here, we discuss three recent studies that implicate ectopic senescence in neurodevelopmental defects, with possible causative roles for senescence in these birth defects. In addition, we highlight how the examination of senescence in other birth defects is warranted, and speculate that aberrantly activated senescence may play a much broader role in developmental defects than currently appreciated.

Obesity impacts placental function through activation of p-IRE1a-XBP1s signaling

Maternal obesity is associated with a variety of obstetrical outcomes including stillbirth, preeclampsia, and gestational diabetes, and increases the risk of fetuses for congenital heart defects. Obesity during pregnancy represents a major contribution to metabolic dysregulation, which not only plays a key role in the pathogenesis of adverse outcome but also can potently induce endoplasmic reticulum (ER) stress. However, the mechanism associating such an obesogenic metabolic environment and adverse pregnancy outcomes has remained poorly understood. In this study, we aimed to determine whether the ER stress pathways (also named unfolded protein response (UPR)) were activated in the placenta by obesity. We collected placenta from the obese pregnancy (n = 12) and non-obese pregnancy (n = 12) following delivery by Caesarean-section at term. The specimens were assessed with immunocytochemistry staining and RT-QPCR. Our results revealed that in the obese placenta, p-IRE1α and XBP1s were significantly increased, CHOP and nine UPR chaperone genes were upregulated, including GRP95, PDIA6, Calnexin, p58IPK, SIL-1, EDEM, Herp, GRP58 and Calreticulin. However, Perk and BiP are not activated in the obese placenta. Our data suggest that upregulated p-IRE1α and XBP1s signaling, and UPR chaperone genes may play an important role in maternal obesity-induced placental pathology. In conclusion, this is the first report on ER stress and UPR activation in the placenta of maternal obesity. Our findings represent the first step in the understanding of one of the key ER signaling pathways, also referred to IRE1α-XBP1, in placental pathophysiology affected by obesity, which may be an important mechanism accounting for the observed higher maternal and perinatal risks.

Alleviation of cisplatin-induced neuropathic pain, neuronal apoptosis, and systemic inflammation in mice by rapamycin

Platinum-based chemotherapeutic treatment of cancer patients is associated with debilitating adverse effects. Several adverse effects have been well investigated, and can be managed satisfactorily, but chemotherapy-induced peripheral neuropathy (CIPN) remains poorly treated. Our primary aim in this study was to investigate the neuroprotective effect of the immunomodulatory drug rapamycin in the mitigation of cisplatin-induced neurotoxicity. Pain assays were performed in vivo to determine whether rapamycin would prevent or significantly decrease cisplatin-induced neurotoxicity in adult male Balb/c mice. Neuropathic pain induced by both chronic and acute exposure to cisplatin was measured by hot plate assay, cold plate assay, tail-flick test, and plantar test. Rapamycin co-treatment resulted in significant reduction in cisplatin-induced nociceptive-like symptoms. To understand the underlying mechanisms behind rapamycin-mediated neuroprotection, we investigated its effect on certain inflammatory mediators implicated in the propagation of chemotherapy-induced neurotoxicity. Interestingly, cisplatin was found to significantly increase peripheral IL-17A expression and CD8- T cells, which were remarkably reversed by the pre-treatment of mice with rapamycin. In addition, rapamycin reduced the cisplatin-induced neuronal apoptosis marked by decreased neuronal caspase-3 activity. The rapamycin neuroprotective effect was also associated with reversal of the changes in protein expression of p21^Cip1, p53, and PUMA. Collectively, rapamycin alleviated some features of cisplatin-induced neurotoxicity in mice and can be further investigated for the treatment of cisplatin-induced peripheral neuropathy.

Oxidative Stress Kinase Activation and Impaired Insulin Receptor Signaling Precede Overt Alzheimer’s Disease Neuropathology

Background: The cascade of events that lead to Alzheimer’s disease (AD) consists of several possible underlying signal transduction pathways. Apoptosis signal-regulating kinase 1 (ASK1) and insulin receptor (IR) signaling are implicated in AD. Objective: We aimed to determine whether ASK1 activation and IR signaling impairment occurred prior to and during overt AD. Methods: Immunostaining, immunoblotting, and quantitative PCR were used to assess the levels of ASK1 and IR signaling intermediates. Glucose uptake was determined in AD-patient derived inducible pluripotent stem cells (iPSCs). Results: ASK1 signaling was activated in postmortem brain tissues acquired from APOE4 carriers, a causative heritable factor, and in brain tissues of AD subjects in comparison with those harboring the normal APOE3 variant, which was manifested with an increased phosphorylated ASK1 (p-ASK1) and reduced thioredoxin 1 (TRX1). ASK1 downstream signaling effectors were also significantly elevated in these APOE4 carriers and AD brain tissues. Increased insulin receptor substrate 1 (IRS1) phosphorylation at serine residues, and decreased p-AKT1, p-IRβ, and GLUT3 expression were present in all APOE4 carriers and AD samples, suggesting impaired IR signaling leading to insulin resistance. ASK1 activation, IR signaling impairment, and GLUT3 reduction were also present in young AD transgenic mice prior to AD syndromes, AD mice at AD neuropathology onset, and AD iPSCs and their derived neurons prior to p-Tau aggregation. Conclusion: We conclude that the activation of oxidative stress-responsive kinases and reduced IR signaling precede and are persistent in AD pathogenesis. Our data further suggest possible crosstalk between ASK1 signaling and insulin resistance in AD etiology.

SARS-CoV-2 invades cognitive centers of the brain and induces Alzheimer's-like neuropathology

The neurotropism of SARS-CoV-2 and the phenotypes of infected neurons are still in debate. Long COVID manifests with "brain diseases" and the cause of these brain dysfunction is mysterious. Here, we analyze 34 age- and underlying disease-matched COVID-19 or non-COVID-19 human brains. SARS-CoV-2 RNA, nucleocapsid, and spike proteins are present in neurons of the cognitive centers of all COVID-19 patients, with its non-structural protein NSF2 detected in adult cases but not in the infant case, indicating viral replications in mature neurons. In adult COVID-19 patients without underlying neurodegeneration, SARS-CoV-2 infection triggers Aβ and p-tau deposition, degenerating neurons, microglia activation, and increased cytokine, in some cases with Aβ plaques and p-tau pretangles. The number of SARS-CoV-2 + cells is higher in patients with neurodegenerative diseases than in those without such conditions. SARS-CoV-2 further activates microglia and induces Aβ and p-tau deposits in non-Alzheimer's neurodegenerative disease patients. SARS-CoV-2 infects mature neurons derived from inducible pluripotent stem cells from healthy and Alzheimer's disease (AD) individuals through its receptor ACE2 and facilitator neuropilin-1. SARS-CoV-2 triggers AD-like gene programs in healthy neurons and exacerbates AD neuropathology. An AD infectious etiology gene signature is identified through SARS-CoV-2 infection and silencing the top three downregulated genes in human primary neurons recapitulates the neurodegenerative phenotypes of SARS-CoV-2. Thus, our data suggest that SARS-CoV-2 invades the brain and activates an AD-like program.

Pathogenesis of neural tube defects: The regulation and disruption of cellular processes underlying neural tube closure

Neural tube closure (NTC) is crucial for proper development of the brain and spinal cord and requires precise morphogenesis from a sheet of cells to an intact three-dimensional structure. NTC is dependent on successful regulation of hundreds of genes, a myriad of signaling pathways, concentration gradients, and is influenced by epigenetic and environmental cues. Failure of NTC is termed a neural tube defect (NTD) and is a leading class of congenital defects in the United States and worldwide. Though NTDs are all defined as incomplete closure of the neural tube, the pathogenesis of an NTD determines the type, severity, positioning, and accompanying phenotypes. In this review, we survey pathogenesis of NTDs relating to disruption of cellular processes arising from genetic mutations, altered epigenetic regulation, and environmental influences by micronutrients and maternal condition. This article is categorized under: Congenital Diseases > Genetics/Genomics/Epigenetics Neurological Diseases > Genetics/Genomics/Epigenetics Neurological Diseases > Stem Cells and Development.

Single-cell transcriptomic profiling unveils dysregulation of cardiac progenitor cells and cardiomyocytes in a mouse model of maternal hyperglycemia

Congenital heart disease (CHD) is the most prevalent birth defect, often linked to genetic variations, environmental exposures, or combination of both. Epidemiological studies reveal that maternal pregestational diabetes is associated with ~5-fold higher risk of CHD in the offspring; however, the causal mechanisms affecting cardiac gene-regulatory-network (GRN) during early embryonic development remain poorly understood. In this study, we utilize an established murine model of pregestational diabetes to uncover the transcriptional responses in key cell-types of the developing heart exposed to maternal hyperglycemia (matHG). Here we show that matHG elicits diverse cellular responses in E9.5 and E11.5 embryonic hearts compared to non-diabetic hearts by single-cell RNA-sequencing. Through differential-gene-expression and cellular trajectory analyses, we identify perturbations in genes, predominantly affecting Isl1⁺ second heart field progenitors and Tnnt2⁺ cardiomyocytes with matHG. Using cell-fate mapping analysis in Isl1-lineage descendants, we demonstrate that matHG impairs cardiomyocyte differentiation and alters the expression of lineage-specifying cardiac genes. Finally, our work reveals matHG-mediated transcriptional changes in second heart field lineage that elevate CHD risk by perturbing Isl1-GRN during cardiomyocyte differentiation. Gene-environment interaction studies targeting the Isl1-GRN in cardiac progenitor cells will have a broader impact on understanding the mechanisms of matHG-induced risk of CHD associated with diabetic pregnancies.

ScRNA-seq of embryonic heart tissues from a mouse model of maternal hyperglycemia (matHG) provides further insight into how matHG disrupts heart development and perturbs second heart field derived cardiomyocyte differentiation.

Functional cargos of exosomes derived from Flk-1+ vascular progenitors enable neurulation and ameliorate embryonic anomalies in diabetic pregnancy

Various types of progenitors initiate individual organ formation and their crosstalk orchestrates morphogenesis for the entire embryo. Here we show that progenitor exosomal communication across embryonic organs occurs in normal development and is altered in embryos of diabetic pregnancy. Endoderm fibroblast growth factor 2 (FGF2) stimulates mesoderm Flk-1+ vascular progenitors to produce exosomes containing the anti-stress protein Survivin. These exosomes act on neural stem cells of the neuroepithelium to facilitate neurulation by inhibiting cellular stress and apoptosis. Maternal diabetes causes Flk-1+ progenitor dysfunction by suppressing FGF2 through DNA hypermethylation. Restoring endoderm FGF2 prevents diabetes-induced survivin reduction in Flk-1+ progenitor exosomes. Transgenic Survivin expression in Flk-1+ progenitors or in utero delivery of survivin-enriched exosomes restores cellular homeostasis and prevents diabetes-induced neural tube defects (NTDs), whereas inhibiting exosome production induces NTDs. Thus, functional inter-organ communication via Flk-1 exosomes is vital for neurulation and its disruption leads to embryonic anomalies.

RNA Hypomethylation and Unchanged DNA Methylation Levels in the Cortex of ApoE4 Carriers and Alzheimer's Disease Subjects

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, and ApoE4 variants are significant risk factors for AD. Epigenetic modifications are involved in AD pathology. However, it is unclear whether DNA/RNA methylation plays a role in AD pathology, and dysregulation of DNA/RNA methylation occurs in ApoE4 carriers.

OBJECTIVE

The present study aimed to determine whether dysregulation of DNA/RNA methylation is present in the brains of ApoE4 carriers and AD patients.

METHODS

In this study, postmortem brain tissues from carriers of ApoE4 and ApoE3, from AD and non- AD controls, were used in the analysis of DNA/RNA methylation, methyltransferases, and their demethylases.

RESULTS

Immunofluorescence staining indicates that RNA methylation is suppressed in ApoE4 carriers. Further analysis shows that the expression of RNA methyltransferases and an RNA methylation reader is suppressed in ApoE4 carriers, whereas RNA demethylase expression is increased. RNA hypomethylation occurs in NeuN+ neurons in ApoE4 carriers and AD patients. Furthermore, in ApoE4 carriers, both DNA methyltransferases and demethylases are downregulated, and overall DNA methylation levels are unchanged.

CONCLUSION

Our finding indicates that RNA methylation decreased in ApoE4 carriers before AD pathology and AD individuals. The expression of RNA methyltransferases and RNA methylation reader is inhibited, and RNA demethylase is upregulated in ApoE4 carriers, which leads to suppression of RNA methylation, and the suppression precedes the AD pathogenesis and persists through AD pathology.

A SARS-CoV-2 Delta Variant Case Manifesting as Extensive Placental Infection and Fetal Transmission

INTRODUCTION

Studies indicate a very low rate of SARS-CoV-2 detection in the placenta or occasionally a low rate of vertical transmission in COVID-19 pregnancy. SARS-CoV-2 Delta variant has become a dominant strain over the world and possesses higher infectivity due to mutations in its spike receptor-binding motif.

CASE PRESENTATION

To determine whether SARS-CoV-2 Delta variant has increased potential for placenta infection and vertical transmission, we analyzed SARS-CoV-2 infection in the placenta, umbilical cord, and fetal membrane from a case where an unvaccinated mother and her neonate were COVID-19 positive. A 35-year-old primigravida with COVID-19 underwent an emergent cesarean delivery due to placental abruption in the setting of premature rupture of membranes. The neonate tested positive for SARS-CoV-2 within the first 24 h, and then again on days of life 2, 6, 13, and 21. The placenta exhibited intervillositis, increased fibrin deposition, and syncytiotrophoblast necrosis. Sequencing of viral RNA from fixed placental tissue revealed SAR-CoV-2 B.1.167.2 (Delta) variant. Both spike protein and viral RNA were abundantly present in syncytiotrophoblasts, cytotrophoblasts, umbilical cord vascular endothelium, and fetal membranes.

CONCLUSION

We report with strong probability the first SARS-CoV-2 Delta variant transplacental transmission. Placental cells exhibited extensive apoptosis, senescence, and ferroptosis after SARS-CoV-2 Delta infection.

BMP9 reduces age-related bone loss in mice by inhibiting osteoblast senescence through Smad1-Stat1-P21 axis

Age-related osteoporosis is characterized by the accumulation of senescent osteoblastic cells in bone microenvironment and significantly reduced osteogenic differentiation. Clearing of the senescent cells is helpful to improve bone formation in aged mice. Bone morphogenetic protein 9 (BMP9), a multifunctional protein produced and secreted by liver, was reported to improve osteoporosis caused by estrogen withdrawal. However, the mechanism of BMP9 has not been fully elucidated, and its effect on senile osteoporosis has not been reported. This study reveals that BMP9 significantly increases bone mass and improves bone biomechanical properties in aged mice. Furthermore, BMP9 reduces expression of senescent genes in bone microenvironment, accompanied by decreased senescence-associated secretory phenotypes (SASPs) such as Ccl5, Mmp9, Hmgb1, Nfkb1, and Vcam1. In vitro, Bmp9 treatment inhibits osteoblast senescence through activating Smad1, which suppresses the transcriptional activity of Stat1, thereby inhibits P21 expression and SASPs production. Furthermore, inhibiting the Smad1 signal in vivo can reverse the inhibitory effect of BMP9 on Stat1 and downstream senescent genes, which eliminates the protection of BMP9 on age-related osteoporosis. These findings highlight the critical role of BMP9 on reducing age-related bone loss by inhibiting osteoblast senescence through Smad1-Stat1-P21 axis.

BMP9 inhibits cellular senescence by activation of Smad1, which suppresses the transcription of Stat1, resulting in decreased P21 expression and SASPs production in osteoblast. The anti-aging effect of BMP9 is benefit to improving age-related osteoporosis.

Senolytics: Eliminating Senescent Cells and Alleviating Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is the main cause of cervical and lumbar spondylosis. Over the past few years, the relevance between cellular senescence and IVDD has been widely studied, and the senescence-associated secretory phenotype (SASP) produced by senescent cells is found to remodel extracellular matrix (ECM) metabolism and destruct homeostasis. Elimination of senescent cells by senolytics and suppression of SASP production by senomorphics/senostatics are effective strategies to alleviate degenerative diseases including IVDD. Here, we review the involvement of senescence in the process of IVDD; we also discuss the potential of senolytics on eliminating senescent disc cells and alleviating IVDD; finally, we provide a table listing senolytic drugs and small molecules, aiming to propose potential drugs for IVDD therapy in the future.

Blockage of ERCC6 Alleviates Spinal Cord Injury Through Weakening Apoptosis, Inflammation, Senescence, and Oxidative Stress

Objective: Spinal cord injury (SCI) is a devastating disease resulting in lifelong disability, but the molecular mechanism remains unclear. Our study was designed to observe the role of excision repair cross-complementing group 6 (ERCC6) following SCI and to determine the underlying mechanism.

Methods: SCI mouse models and LPS-induced microglia cell models were established. ERCC6 expression was blocked by ERCC6-siRNA-carrying lentivirus. Nissl staining was utilized for detecting neuronal damage, and apoptosis was analyzed with TUNEL and Western blotting (apoptotic markers). Immunofluorescence was used for measuring macrophage markers (CD68 and F4/80) and astrocyte and microglia markers (GFAP and Iba-1). Pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) were measured via ELISA. Senescent cells were estimated via SA-β-Gal staining as well as Western blot (senescent markers p21 and p27). Oxidative stress was investigated by detecting the expression of 4-HNE, Nrf2, and Keap1, and intracellular ROS levels.

Results: ERCC6 expression was remarkably upregulated both in the spinal cord of SCI mice and LPS-induced microglia cells. ERCC6 deficiency alleviated neuronal damage and apoptosis. Macrophage infiltration and inflammatory response were suppressed by si-ERCC6 treatment. Moreover, ERCC6 blockage ameliorated astrocyte and microglia activation and cell senescence in the damaged spinal cord. Excessive oxidative stress was significantly decreased by ERCC6 knockdown in SCI.

Conclusion: Collectively, ERCC6 exerts crucial functions in mediating physiological processes (apoptosis, inflammation, senescence, and oxidative stress), implying that ERCC6 might act as a prospective therapeutic target against SCI.

Nuclear factor I-C disrupts cellular homeostasis between autophagy and apoptosis via miR-200b-Ambra1 in neural tube defects

Impaired autophagy and excessive apoptosis disrupt cellular homeostasis and contribute to neural tube defects (NTDs), which are a group of fatal and disabling birth defects caused by the failure of neural tube closure during early embryonic development. However, the regulatory mechanisms underlying NTDs and outcomes remain elusive. Here, we report the role of the transcription factor nuclear factor I-C (NFIC) in maintaining cellular homeostasis in NTDs. We demonstrated that abnormally elevated levels of NFIC in a mouse model of NTDs can interact with the miR-200b promoter, leading to the activation of the transcription of miR-200b, which plays a critical role in NTD formation, as reported in our previous study. Furthermore, miR-200b represses autophagy and triggers apoptosis by directly targeting the autophagy-related gene Ambra1 (Autophagy/Beclin1 regulator 1). Notably, miR-200b inhibitors mitigate the unexpected effects of NFIC on autophagy and apoptosis. Collectively, these results indicate that the NFIC-miR-200b-Ambra1 axis, which integrates transcription- and epigenome-regulated miRNAs and an autophagy regulator, disrupts cellular homeostasis during the closure of the neural tube, and may provide new insight into NTD pathogenesis.

Transgenic overexpression of the miR-200b/200a/429 cluster inhibits mammary tumor initiation

•

Overexpression of the miR-200b/200a/429 cluster prevents mammary tumor initiation.

•

miR-200s may prevent mammary tumor initiation by suppressing Spp1, Saa1 and Saa2.

•

Overexpression of miR-200s does not impair normal mammary ductal development.

The miR-200 family consists of five members expressed as two clusters: miR-200c/141 cluster and miR-200b/200a/429 cluster. In the mammary gland, miR-200s maintain epithelial identity by decreasing the expression of mesenchymal markers leading to high expression of epithelial markers. While the loss of miR-200s is associated with breast cancer growth and metastasis the impact of miR-200 expression on mammary tumor initiation has not been investigated. Using mammary specific expression of the miR-200b/200a/429 cluster in transgenic mice, we found that elevated expression miR-200s could almost completely prevent mammary tumor development. Only 1 of 16 MTB-IGFIRba429 transgenic mice (expressing both the IGF-IR and miR-200b/200a/429 transgenes) developed a mammary tumor while 100% of MTB-IGFIR transgenic mice (expressing only the IGF-IR transgene) developed mammary tumors. RNA sequencing, qRT-PCR, and immunohistochemistry of mammary tissue from 55-day old mice found Spp1, Saa1, and Saa2 to be elevated in mammary tumors and inhibited by miR-200b/200a/429 overexpression. This study suggests that miR-200s could be used as a preventative strategy to protect women from developing breast cancer. One concern with this approach is the potential negative impact miR-200 overexpression may have on mammary function. However, transgenic overexpression of miR-200s, on their own, did not significantly impact mammary ductal development indicating the miR-200 overexpression should not significantly impact mammary function. Thus, this study provides the initial foundation for using miR-200s for breast cancer prevention and additional studies should be performed to identify strategies for increasing mammary miR-200 expression and determine whether miR-200s can prevent mammary tumor initiation by other genetic alterations.