Growth Differentiation Factor 11 treatment leads to neuronal and vascular improvements in the hippocampus of aged mice

Circulatory factors in stroke protection and recovery

Over the past decade, the management of acute ischemic stroke has undergone a paradigm shift, especially a longer time-window and a wider indication for endovascular treatments. However, many patients still have long-term dysfunction despite the best medical care at present. Based on findings from innovative proteomic and transcriptomic technologies, researchers have identified an array of novel or previously underappreciated circulatory factors that play pivotal roles in mediating post-injuries brain communication. Thus, the previous concept of the brain as a privileged compartment isolated from the rest of the body has been replaced by the novel consensus that brain bidirectionally interacts with the other organs after brain diseases. In this review, we make a summary of several axes that connect the brain with the rest of the body after stroke. More importantly, we summarize several circulatory factors that play pivotal roles in fostering post-stroke functional recovery in the chronic stage. Special attention is given to the instrumental role of circulatory signals, positing them as significant contributors to the complex process of brain function recovery and as translational therapeutic targets for ischemic stroke in future studies.

Recombinant GDF11 Promotes Recovery in a Rat Permanent Ischemia Model of Subacute Stroke

BACKGROUND

Stroke remains a leading cause of death and disability, underscoring the urgent need for treatments that enhance recovery. GDF11 (growth differentiation factor 11), a member of the TGF-β (transforming growth factor-β) superfamily, is a circulating protein involved in cellular development and tissue repair. GDF11 has gained attention for its potential regenerative properties in aging and disease contexts, making it a candidate for stroke recovery therapies.

METHODS

The therapeutic benefits of rGDF11 (recombinant GDF11) were evaluated using a rat ischemic stroke model, in which focal cerebral infarcts were induced in 8- to 10-week-old young adult male Sprague-Dawley rats by permanently occluding the proximal right middle cerebral artery. Rats received single or multiple doses of rGDF11 (0.1-4 mg/kg) or vehicle from 24 to 72 hours post-injury. Sensorimotor functions were evaluated, and brain and serum samples were examined to determine the mechanisms of action and identify biomarkers, using immunofluorescence, target-specific ELISAs, and an aptamer-based proteomics platform.

RESULTS

We confirmed rGDF11 activity in vitro and in established in vivo mouse models of cardiac hypertrophy and glucose metabolism and assessed the efficacy of rGDF11 treatment in 6 preclinical stroke studies using independent Contract Research Organizations, with all study animals and treatment groups blinded. All 6 studies revealed consistent improvement in sensorimotor outcomes with rGDF11. rGDF11-treated rats showed increased cortical vascularization and radial glia in the ventricular zone. Serum analysis revealed that rGDF11 caused dose-dependent decreases in CRP (C-reactive protein) and identified novel pharmacodynamic biomarkers and pathways associated with potential mechanisms of action of rGDF11.

CONCLUSIONS

These results demonstrate that systemically delivered rGDF11 enhances neovascularization, reduces inflammation, promotes neurogenesis, and improves sensorimotor function post-injury in a rat model of ischemic stroke. More importantly, these data define an optimized and clinically feasible rGDF11 dosing regimen for therapeutic development in ischemic stroke and identify a panel of candidate pharmacodynamic and mechanistic biomarkers to support clinical translation.

Systemic Rejuvenating Interventions: Perspectives on Neuroinflammation and Blood-Brain Barrier Integrity

The aging process results in structural, functional, and immunological changes in the brain, which contribute to cognitive decline and increase vulnerability to neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and stroke-related complications. Aging leads to cognitive changes and also affect executive functions. Additionally, it causes neurogenic and neurochemical alterations, such as a decline in dopamine and acetylcholine levels, which also impact cognitive performance. The chronic inflammation caused by aging contributes to the impairment of the blood-brain barrier (BBB), contributing to the infiltration of immune cells and exacerbating neuronal damage. Therefore, rejuvenating therapies such as heterochronic parabiosis, cerebrospinal fluid (CSF) administration, plasma, platelet-rich plasma (PRP), and stem cell therapy have shown potential to reverse these changes, offering new perspectives in the treatment of age-related neurological diseases. This review focuses on highlighting the effects of rejuvenating interventions on neuroinflammation and the BBB.

The pathobiology of neurovascular aging

As global life expectancy increases, age-related brain diseases such as stroke and dementia have become leading causes of death and disability. The aging of the neurovasculature is a critical determinant of brain aging and disease risk. Neurovascular cells are particularly vulnerable to aging, which induces significant structural and functional changes in arterial, venous, and lymphatic vessels. Consequently, neurovascular aging impairs oxygen and glucose delivery to active brain regions, disrupts endothelial transport mechanisms essential for blood-brain exchange, compromises proteostasis by reducing the clearance of potentially toxic proteins, weakens immune surveillance and privilege, and deprives the brain of key growth factors required for repair and renewal. In this review, we examine the effects of neurovascular aging on brain function and its role in stroke, vascular cognitive impairment, and Alzheimer's disease. Finally, we discuss key unanswered questions that must be addressed to develop neurovascular strategies aimed at promoting healthy brain aging.

Natural products that alleviate depression: The putative role of autophagy

Major depressive disorder (MDD) is a common mental disorder that severely disrupts psychosocial function and decreases the quality of life. Although the pathophysiological mechanism underlying MDD is complex and remains unclear, emerging evidence suggests that autophagy dysfunction plays a role in MDD occurrence and progression. Natural products serve as a major source of drug discovery and exert tremendous potential in developing antidepressants. Recently published reports are paying more attention on the autophagy regulatory effect of antidepressant natural products. In this review, we comprehensively discuss the abnormal changes occurred in multiple autophagy stages in MDD patients, and animal and cell models of depression. Importantly, we emphasize the regulatory mechanism of antidepressant natural products on disturbed autophagy, including monomeric compounds, bioactive components, crude extracts, and traditional Chinese medicine formulae. Our comprehensive review suggests that enhancing autophagy might be a novel approach for MDD treatment, and natural products restore autophagy homeostasis to facilitate the renovation of mitochondria, impede neuroinflammation, and enhance neuroplasticity, thereby alleviating depression.

Blood-derived factors to brain communication in brain diseases

Brain diseases, mainly including acute brain injuries, neurodegenerative diseases, and mental disorders, have posed a significant threat to human health worldwide. Due to the limited regenerative capability and the existence of the blood-brain barrier, the brain was previously thought to be separated from the rest of the body. Currently, various cross-talks between the central nervous system and peripheral organs have been widely described, including the brain-gut axis, the brain-liver axis, the brain-skeletal muscle axis, and the brain-bone axis. Moreover, several lines of evidence indicate that leveraging systemic biology intervention approaches, including but not limited to lifestyle interventions, exercise, diet, blood administration, and peripheral immune responses, have demonstrated a significant influence on the progress and prognosis of brain diseases. The advancement of innovative proteomic and transcriptomic technologies has enriched our understanding of the nuanced interplay between peripheral organs and brain diseases. An array of novel or previously underappreciated blood-derived factors have been identified to play pivotal roles in mediating these communications. In this review, we provide a comprehensive summary of blood-to-brain communication following brain diseases. Special attention is given to the instrumental role of blood-derived signals, positing them as significant contributors to the complex process of brain diseases. The insights presented here aim to bridge the current knowledge gaps and inspire novel therapeutic strategies for brain diseases.

Growth Differentiation Factor 11 Evokes Lung Injury, Inflammation, and Fibrosis in Mice through the Activin A Receptor Type II-Like Kinase, 53kDa-Smad2/3 Signaling Pathway

Growth differentiation factor 11 (GDF11) belongs to the transforming growth factor beta superfamily and participates in various pathophysiological processes. Initially, GDF11 was suggested to act as a rejuvenator by improving age-related phenotypes of the heart, brain, and skeletal muscle in aged mice. Recent studies demonstrate that GDF11 also serves as an adverse risk factor for human frailty and diseases. However, the role of GDF11 in pulmonary fibrosis (PF) remains unclear. This study explored the role and signaling mechanisms of GDF11 in PF. GDF11 expression was markedly up-regulated in fibrotic lung tissues of both humans and mice. Intratracheal administration of commercial recombinant GDF11 caused lung injury, inflammation, and fibrogenesis in mice. Furthermore, adenovirus-mediated secretory expression of mature GDF11 was exacerbated, whereas full-length GDF11 or the GDF11 propeptide (GDF111-298) alleviated bleomycin-induced PF in mice. In in vitro experiments, GDF11 suppressed the growth of alveolar and bronchial epithelial cells (A549 and BEAS-2B) and human pulmonary microvascular endothelial cells, promoted fibroblast activation, and induced epithelial/endothelial-mesenchymal transition. These effects corresponded to the phosphorylation of Smad2/3, and blocking activin A receptor type II-like kinase, 53kDa (ALK5)-Smad2/3 signaling abolished the in vivo and in vitro effects of GDF11. In conclusion, these findings provide evidence that GDF11 acts as a potent injurious, proinflammatory, and profibrotic factor in the lungs via the ALK5-Smad2/3 pathway.

Polygenic proxies of age-related plasma protein levels reveal TIMP2 role in cognitive performance

Background

While numerous studies have identified blood proteins that modulate brain aging in mice, the direct translation of these findings to human health remains a substantial challenge. Bridging this gap is critical for developing interventions that can effectively target human brain aging and associated diseases.

Methods

We first identified 12 proteins with aging or rejuvenating properties in murine brains through a systematic review. Using protein quantitative trait loci data for these proteins, we developed polygenic scores to predict plasma protein levels, which we then validated in two independent human cohorts. We employed association models to explore the association between these genetically predicted protein levels and cognitive performance, focusing specifically on their interaction with key genetic markers such as sex, APOE-ε4 and Aβ42 status.

Results

Predicted plasma levels of Tissue Inhibitor of Metalloproteinases 2 (TIMP2) were significantly associated with improved global cognition and memory performance in humans, also when the models were stratified by sex, APOE-ε4, and Aβ42 status.

Conclusions

This finding aligns with TIMP2's brain-rejuvenating role in murine models, suggesting it as a promising therapeutic target for brain aging and age-related brain diseases in humans.

Young blood-mediated cerebromicrovascular rejuvenation through heterochronic parabiosis: enhancing blood-brain barrier integrity and capillarization in the aged mouse brain

Age-related cerebromicrovascular changes, including blood-brain barrier (BBB) disruption and microvascular rarefaction, play a significant role in the development of vascular cognitive impairment (VCI) and neurodegenerative diseases. Utilizing the unique model of heterochronic parabiosis, which involves surgically joining young and old animals, we investigated the influence of systemic factors on these vascular changes. Our study employed heterochronic parabiosis to explore the effects of young and aged systemic environments on cerebromicrovascular aging in mice. We evaluated microvascular density and BBB integrity in parabiotic pairs equipped with chronic cranial windows, using intravital two-photon imaging techniques. Our results indicate that short-term exposure to young systemic factors leads to both functional and structural rejuvenation of cerebral microcirculation. Notably, we observed a marked decrease in capillary density and an increase in BBB permeability to fluorescent tracers in the cortices of aged mice undergoing isochronic parabiosis (20-month-old C57BL/6 mice [A-(A)]; 6 weeks of parabiosis), compared to young isochronic parabionts (6-month-old, [Y-(Y)]). However, aged heterochronic parabionts (A-(Y)) exposed to young blood exhibited a significant increase in cortical capillary density and restoration of BBB integrity. In contrast, young mice exposed to old blood from aged parabionts (Y-(A)) rapidly developed cerebromicrovascular aging traits, evidenced by reduced capillary density and increased BBB permeability. These findings underscore the profound impact of systemic factors in regulating cerebromicrovascular aging. The rejuvenation observed in the endothelium, following exposure to young blood, suggests the existence of anti-geronic elements that counteract microvascular aging. Conversely, pro-geronic factors in aged blood appear to accelerate cerebromicrovascular aging. Further research is needed to assess whether the rejuvenating effects of young blood factors could extend to other age-related cerebromicrovascular pathologies, such as microvascular amyloid deposition and increased microvascular fragility.

Polygenic proxies of age-related plasma protein levels reveal TIMP2 role in cognitive performance

Several studies have identified blood proteins that influence brain aging performance in mice, yet translating these findings to humans remains challenging. Here we found that higher predicted plasma levels of Tissue Inhibitor of Metalloproteinases 2 (TIMP2) were significantly associated with improved global cognition and memory performance in humans. We first identified 12 proteins with aging or rejuvenating effects on murine brains through a systematic review. Using protein quantitative trait loci data for these proteins, we computed polygenic scores as proxies for plasma protein levels and validated their prediction accuracy in two independent cohorts. Association models between genetic proxies and cognitive performance highlighted the significance of TIMP2, also when the models were stratified by sex, APOE -ε4, and Aβ42 status. This finding aligns with TIMP2's brain-rejuvenating role in murine models, suggesting it as a promising therapeutic target for brain aging and age-related brain diseases in humans.

Blood-based therapies to combat neurodegenerative diseases

Neurodegeneration, known as the progressive loss of neurons in terms of their structure and function, is the principal pathophysiological change found in the majority of brain-related disorders. Ageing has been considered the most well-established risk factor in most common neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease (AD). There is currently no effective treatment or cure for these diseases; the approved therapeutic options to date are only for palliative care. Ageing and neurodegenerative diseases are closely intertwined; reversing the aspects of brain ageing could theoretically mitigate age-related neurodegeneration. Ever since the regenerative properties of young blood on aged tissues came to light, substantial efforts have been focused on identifying and characterizing the circulating factors in the young and old systemic milieu that may attenuate or accentuate brain ageing and neurodegeneration. Later studies discovered the superiority of old plasma dilution in tissue rejuvenation, which is achieved through a molecular reset of the systemic proteome. These findings supported the use of therapeutic blood exchange for the treatment of degenerative diseases in older individuals. The first objective of this article is to explore the rejuvenating properties of blood-based therapies in the ageing brains and their therapeutic effects on AD. Then, we also look into the clinical applications, various limitations, and challenges associated with blood-based therapies for AD patients.

Healthy blood, healthy brain: a window into understanding and treating neurodegenerative diseases

Our limited understanding of complex neurodegenerative disorders has held us back on the development of efficient therapies. While several approaches are currently being considered, it is still unclear what will be most successful. Among the latest and more novel ideas, the concept of blood or plasma transfusion from young healthy donors to diseased patients is gaining momentum and attracting attention beyond the scientific arena. While young or healthy blood is enriched with protective and restorative components, blood from older subjects may accumulate neurotoxic agents or be impoverished of beneficial factors. In this commentary, we present an overview of the compelling evidence collected in various animal models of brain diseases (e.g., Alzheimer, Parkinson, Huntington) to the actual clinical trials that have been conducted to test the validity of blood-related treatments in neurodegenerative diseases and argue in favor of such approach.

Progress in the relationship between GDF11 and depression

Annually, the frequency of morbidity in depression has increased progressively in response to life stressors, and there is an increasing trend toward younger morbidity. The pathogenesis of depression is complicated and includes factors such as genetic inheritance and variations in physiological functions induced by various environmental factors. Currently, drug therapy has wide adaptability in clinical practice and plays an important role in the treatment of patients with mild depression. However, the therapeutic effects of most antidepressants are typically not significant and are associated with considerable adverse effects and addiction. Therefore, it is imperative to identify the deeper mechanisms of depression and search for alternative drug targets. Growth differentiation factor 11 (GDF11) is described as an anti-ageing molecule that belongs to a member of the transforming growth factor β family. Additionally, the latest research findings suggested that GDF11 positively regulates neurogenesis and enhances neuronal activity, thereby attenuating depression-like behaviours. Although an increasing number of studies have focused on the multiple functions of GDF11 in skeletal dysplasia and carcinogenesis, its precise mechanism of action in depression remains unknown. Thus, in this review, we discuss the role of GDF11 and its mechanistic pathways in the pathogenesis of depression to develop novel therapies for depression.

GDF11 mediates H2S to prevent chronic stress-induced cognitive impairment by reducing hippocampal NLRP3/caspase-1-dependent pyroptosis

BACKGROUND

We previously revealed that hydrogen sulfide (H2S) attenuates chronic stress-induced cognitive impairment, but the underlying mechanism needs to be further clarified. Growth differentiation factor 11 (GDF11) plays an important regulatory role in cognitive function and that hippocampal NLRP3/caspase-1-mediated pyroptosis contributes to the pathogenesis of cognitive impairment. Hence, this research aimed to explore whether promoting GDF11 levels and suppressing hippocampal NLRP3/caspase-1-mediated pyroptosis mediate H2S to alleviate chronic stress-induced cognitive impairment.

METHODS

Sprague-Dawley rats were subjected to unpredictable chronic mild stress lasting four weeks to establish an animal model of chronic stress-induced cognitive impairment. Behavioral performance was assessed by the Y-maze test and the novel object recognition test. The expression levels of proteins were analyzed by Western blot analysis. The levels of IL-1β and IL-18 in the hippocampus were measured by ELISA.

RESULTS

NaHS upregulated the expression of GDF11 in the hippocampus of chronic unpredictable mild stress (CUMS)-exposed rats. Silencing GDF11 blocked NaHS-improved cognitive impairment in CUMS-exposed rats, according to the Y-maze test and the novel object recognition test. Furthermore, NaHS mitigated NLRP3/caspase-1-mediated pyroptosis in the hippocampus of CUMS-exposed rats and this effect was reversed by silencing GDF11. Moreover, overexpression of GDF11 alleviated CUMS-induced cognitive impairment and NLRP3/caspase-1-mediated hippocampal pyroptosis.

CONCLUSIONS

GDF11 mediates H2S to attenuate chronic stress-induced cognitive impairment via inhibiting hippocampal NLRP3/caspase-1-mediated pyroptosis.

Skeletal muscle TFEB signaling promotes central nervous system function and reduces neuroinflammation during aging and neurodegenerative disease

Skeletal muscle has recently arisen as a regulator of central nervous system (CNS) function and aging, secreting bioactive molecules known as myokines with metabolism-modifying functions in targeted tissues, including the CNS. Here, we report the generation of a transgenic mouse with enhanced skeletal muscle lysosomal and mitochondrial function via targeted overexpression of transcription factor E-B (TFEB). We discovered that the resulting geroprotective effects in skeletal muscle reduce neuroinflammation and the accumulation of tau-associated pathological hallmarks in a mouse model of tauopathy. Muscle-specific TFEB overexpression significantly ameliorates proteotoxicity, reduces neuroinflammation, and promotes transcriptional remodeling of the aged CNS, preserving cognition and memory in aged mice. Our results implicate the maintenance of skeletal muscle function throughout aging in direct regulation of CNS health and disease and suggest that skeletal muscle originating factors may act as therapeutic targets against age-associated neurodegenerative disorders.

GDF11 slows excitatory neuronal senescence and brain ageing by repressing p21

As a major neuron type in the brain, the excitatory neuron (EN) regulates the lifespan in C. elegans. How the EN acquires senescence, however, is unknown. Here, we show that growth differentiation factor 11 (GDF11) is predominantly expressed in the EN in the adult mouse, marmoset and human brain. In mice, selective knock-out of GDF11 in the post-mitotic EN shapes the brain ageing-related transcriptional profile, induces EN senescence and hyperexcitability, prunes their dendrites, impedes their synaptic input, impairs object recognition memory and shortens the lifespan, establishing a functional link between GDF11, brain ageing and cognition. In vitro GDF11 deletion causes cellular senescence in Neuro-2a cells. Mechanistically, GDF11 deletion induces neuronal senescence via Smad2-induced transcription of the pro-senescence factor p21. This work indicates that endogenous GDF11 acts as a brake on EN senescence and brain ageing.

Evaluation of Associations of Growth Differentiation Factor-11, Growth Differentiation Factor-8, and Their Binding Proteins Follistatin and Follistatin-Like Protein-3 With Dementia and Cognition

BACKGROUND

Studies using heterochronic parabiosis discovered that circulating factors mediate brain aging in animal models.

METHODS

We assessed growth differentiation factors (GDF)-11 and GDF-8 using mass spectrometry and inhibitors follistatin and follistatin-like protein-3 (FSTL-3) with ELISA in the Cardiovascular Health Study (CHS; N = 1 506) and the Health, Aging and Body Composition (Health ABC) Study (N = 1 237). CLL-11 and beta-2 microglobulin (β2M) were measured with ELISA in a subset of 400 individuals in Health ABC. Associations were assessed with cognitive function, brain magnetic resonance imaging (MRI) findings (CHS only), and incident dementia using correlations, linear regression, and Cox proportional hazards models.

RESULTS

In CHS, levels of GDF-11, GDF-8, and follistatin were not correlated cross-sectionally with the 3MSE or DSST, brain MRI findings of white matter hyperintensity, atrophy, or small infarcts, nor were they associated with incident dementia. FSTL-3 was modestly correlated with poorer cognitive function, greater white matter hyperintensities, and atrophy on MRI, as well as with incident dementia with an adjusted hazard ratio (HR) of 1.72 (95% CI = 1.13, 2.61) per doubling of FSTL-3. FSTL-3 was not associated with cognition or dementia in Health ABC, but GDF-8 was associated with both. The adjusted HR for incident dementia was 1.50 (95% CI = 1.07, 2.10) per doubling of GDF-8.

CONCLUSIONS

Total GDF-11 level was not related to cognition or dementia in older adults. Associations of GDF-8 with cognitive outcomes in Health ABC were not expected, but consistent with animal models. Associations of FSTL-3 with cognition, brain abnormalities, and incident dementia in CHS implicate TGFβ superfamily inhibition in the pathogenesis of dementia.

The germline coordinates mitokine signaling

The ability of mitochondria to coordinate stress responses across tissues is critical for health. In C. elegans , neurons experiencing mitochondrial stress elicit an inter-tissue signaling pathway through the release of mitokine signals, such as serotonin or the WNT ligand EGL-20, which activate the mitochondrial unfolded protein response (UPR MT ) in the periphery to promote organismal health and lifespan. We find that germline mitochondria play a surprising role in neuron-to-peripheral UPR MT signaling. Specifically, we find that germline mitochondria signal downstream of neuronal mitokines, like WNT and serotonin, and upstream of lipid metabolic pathways in the periphery to regulate UPR MT activation. We also find that the germline tissue itself is essential in UPR MT signaling. We propose that the germline has a central signaling role in coordinating mitochondrial stress responses across tissues, and germline mitochondria play a defining role in this coordination because of their inherent roles in germline integrity and inter-tissue signaling.

Heterochronic Plasma Transfer: Experimental Design, Considerations, and Technical Challenges

Experimental approaches such as Heterochronic Plasma Transfer (HPT) provide insights into the aging process and help identify the factors that impact aging, with the aim of developing anti-aging therapies. HPT involves the transfer of plasma from an animal of one age to an animal of a different age and highlights the effects of the systemic environment on aging. Despite its importance as an aging research tool, HPT is not without limitations and HPT experiments across various studies differ in key experimental designs considerations, presenting a challenge in obtaining comparable outcomes. In this review, we examine the caveats and experimental design considerations of HPT as a research tool. We provide insights into plasma preparation procedures, route of administration, dosing regimen, and appropriate controls to assist investigators in achieving their experimental goals.

GDF11 and aging biology - controversies resolved and pending

Since the exogenous administration of GDF11, a TGF-ß superfamily member, was reported to have beneficial effects in some models of human disease, there have been many research studies in GDF11 biology. However, many studies have now confirmed that exogenous administration of GDF11 can improve physiology in disease models, including cardiac fibrosis, experimental stroke, and disordered metabolism. GDF11 is similar to GDF8 (also called Myostatin), differing only by 11 amino acids in their mature signaling domains. These two proteins are now known to be biochemically different both in vitro and in vivo. GDF11 is much more potent than GDF8 and induces more strongly SMAD2 phosphorylation in the myocardium compared to GDF8. GDF8 and GDF11 prodomain are only 52% identical and are cleaved by different Tolloid proteases to liberate the mature signaling domain from inhibition of the prodomain. Here, we review the state of GDF11 biology, highlighting both resolved and remaining controversies.

tVNS in Stroke: A Narrative Review on the Current State and the Future

Ischemic stroke is a leading cause of disability and there is a paucity of therapeutic strategies that promote functional recovery after stroke. Transcutaneous vagus nerve stimulation (tVNS) has shown promising evidence as a tool to reduce infarct size in animal models of hyperacute stroke. In chronic stroke, tVNS paired with limb movements has been shown to enhance neurological recovery. In this review, we summarize the current evidence for tVNS in preclinical models and clinical trials in humans. We highlight the mechanistic pathways involved in the beneficial effects of tVNS. We critically evaluate the current gaps in knowledge and recommend the key areas of research required to translate tVNS into clinical practice in acute and chronic stroke.

Effect of growth differentiation factor 11 expression after peripheral nerve injury in Sprague-Dawley rats

OBJECTIVES

We attempt to investigate the expression pattern of GDF11 in the sciatic nerves after injury.

METHODS

Thirty-six healthy male Sprague Dawley (SD) rats were divided into three groups at random and were labelled as: day 1, day 4, and day 7 post-surgery. The sciatic nerve crush model was established on the left-hind limb, while the right limb was untreated, and served as the control. Nerve samples were collected at post-injury day 1, day 4 and day 7. Nerve samples collected from the proximal and distal stump of the injury site underwent immunofluorescence staining with GDF11, NF200 and CD31. GDF11 mRNA expression was analyzed by qRT-PCR. CCK-8 assay, after si-GDF11 transfection in Schwann cells (RSC96) was applied to verify its effect in cell proliferation rate.

RESULTS

GDF11 was abundantly expressed in axons stained with NF200 and Schwann cells stained with S100. However, no GDF11 expression was observed in vascular endothelial tissues stained with CD31. From day 4 onwards, the level of GDF11 showed an increasing trend, up to a twofold level at day 7 after injury. Proliferation rate of RSC96 cells showed a significant decrease after the down-regulation of GDF11 by siRNAs compared to the control group.

CONCLUSIONS

GDF11 may play a role in the proliferation of Schwann cell during nerve regeneration process.

From Youthful Vigor to Aging Decline: Unravelling the Intrinsic and Extrinsic Determinants of Hippocampal Neural Stem Cell Aging

Since Joseph Altman published his pioneering work demonstrating neurogenesis in the hippocampus of adult rats, the number of publications in this field increased exponentially. Today, we know that the adult hippocampus harbors a pool of adult neural stem cells (NSCs) that are the source of life-long neurogenesis and plasticity. The functions of these NSCs are regulated by extrinsic cues arising from neighboring cells and the systemic environment. However, this tight regulation is subject to imbalance with age, resulting in a decline in adult NSCs and neurogenesis, which contributes to the progressive deterioration of hippocampus-related cognitive functions. Despite extensive investigation, the mechanisms underlying this age-related decline in neurogenesis are only incompletely understood, but appear to include an increase in NSC quiescence, changes in differentiation patterns, and NSC exhaustion. In this review, we summarize recent work that has improved our knowledge of hippocampal NSC aging, focusing on NSC-intrinsic mechanisms as well as cellular and molecular changes in the niche and systemic environment that might be involved in the age-related decline in NSC functions. Additionally, we identify future directions that may advance our understanding of NSC aging and the concomitant loss of hippocampal neurogenesis and plasticity.

Integrated genomic, proteomic and cognitive assessment in Duchenne Muscular Dystrophy suggest astrocyte centric pathology

Introduction

Documented Duchenne Muscular Dystrophy (DMD) biomarkers are confined to Caucasians and are poor indicators of cognitive difficulties and neuropsychological alterations.

Materials and methods

This study correlates serum protein signatures with cognitive performance in DMD patients of South Asian origin. Study included 25 DMD patients aged 6-16 years. Cognitive profiles were assessed by Wechsler Intelligence Scale for Children. Serum proteome profiling of 1317 proteins was performed in eight DMD patients and eight age-matched healthy volunteers.

Results

Among the several novel observations we report, better cognitive performance in DMD was associated with increased serum levels of MMP9 and FN1 but decreased Siglec-3, C4b, and C3b. Worse cognitive performance was associated with increased serum levels of LDH-H1 and PDGF-BB but reduced GDF-11, MMP12, TPSB2, and G1B. Secondly, better cognitive performance in Processing Speed (PSI) and Perceptual Reasoning (PRI) domains was associated with intact Dp116, Dp140, and Dp71 dystrophin isoforms while better performance in Verbal Comprehension (VCI) and Working Memory (WMI) domains was associated with intact Dp116 and Dp140 isoforms. Finally, functional pathways shared with Alzheimer's Disease (AD) point towards an astrocyte-centric model for DMD.

Conclusion

Astrocytic dysfunction leading to synaptic dysfunction reported previously in AD may be a common pathogenic mechanism underlying both AD and DMD, linking protein alterations to cognitive impairment. This new insight may pave the path towards novel therapeutic approaches targeting reactive astrocytes.

Platelet factors attenuate inflammation and rescue cognition in ageing

Identifying therapeutics to delay, and potentially reverse, age-related cognitive decline is critical in light of the increased incidence of dementia-related disorders forecasted in the growing older population1. Here we show that platelet factors transfer the benefits of young blood to the ageing brain. Systemic exposure of aged male mice to a fraction of blood plasma from young mice containing platelets decreased neuroinflammation in the hippocampus at the transcriptional and cellular level and ameliorated hippocampal-dependent cognitive impairments. Circulating levels of the platelet-derived chemokine platelet factor 4 (PF4) (also known as CXCL4) were elevated in blood plasma preparations of young mice and humans relative to older individuals. Systemic administration of exogenous PF4 attenuated age-related hippocampal neuroinflammation, elicited synaptic-plasticity-related molecular changes and improved cognition in aged mice. We implicate decreased levels of circulating pro-ageing immune factors and restoration of the ageing peripheral immune system in the beneficial effects of systemic PF4 on the aged brain. Mechanistically, we identified CXCR3 as a chemokine receptor that, in part, mediates the cellular, molecular and cognitive benefits of systemic PF4 on the aged brain. Together, our data identify platelet-derived factors as potential therapeutic targets to abate inflammation and rescue cognition in old age.

Plasma growth differentiation factor - 8 / Myostatin level as prognostic biomarker of patients with ischemic stroke and acute revascularization therapy. PARADISE study

BACKGROUND

Identifying biological markers of ischemic stroke (IS) is an important research approach to develop innovative therapeutic strategies. This study aimed to assess the association between plasma Growth Differentiation Factor-8 (GDF-8)/Myostatin levels and outcome of IS patients.

METHODS

Consecutive patients with acute IS treated with either intravenous thrombolysis and/or mechanical thrombectomy at Dijon University Hospital, France were prospectively included. Clinical variables were recorded, and plasma GDF-8 was collected just after the revascularization procedure. Primary endpoint was functional outcome at 3 months assessed by the modified Rankin Scale (mRS) score. Secondary endpoints included mRS scores at 6 and 12 months, and overall mortality over 1-year of follow-up.

RESULTS

Among the 173 included patients (median age: 76 years, Interquartile range (IQR): 66-85; 49% women), median plasma GDF-8 levels at admission were significantly lower in those with a poor outcome at 3 months defined as a mRS score > 2 (2073 (IQR: 1564-2757) pg/mL versus 1471 (1192-2241) pg/mL, p < 0.001). Lower GDF-8 levels at admission were associated with higher 3-months mRS score in multivariable ordinal logistic regression analysis (OR = 0.9995; 95% CI: 0.9991-0.9999, p = 0.011). The association was also observed with 6- and 12-month mRS scores. Although mortality was higher in patients with lower GDF-8 levels, the association was not significant in multivariable Cox analysis.

CONCLUSION

Lower plasma GDF-8 levels were associated with a poorer functional outcome in IS patients treated with acute revascularization therapy. Underlying pathophysiological mechanisms involving GDF-8 in post-stroke outcome remain to be elucidated.

Blood-to-brain communication in aging and rejuvenation

Aging induces molecular, cellular and functional changes in the adult brain that drive cognitive decline and increase vulnerability to dementia-related neurodegenerative diseases. Leveraging systemic and lifestyle interventions, such as heterochronic parabiosis, administration of 'young blood', exercise and caloric restriction, has challenged prevalent views of brain aging as a rigid process and has demonstrated that aging-associated cognitive and cellular impairments can be restored to more youthful levels. Technological advances in proteomic and transcriptomic analyses have further facilitated investigations into the functional impact of intertissue communication on brain aging and have led to the identification of a growing number of pro-aging and pro-youthful factors in blood. In this review, we discuss blood-to-brain communication from a systems physiology perspective with an emphasis on blood-derived signals as potent drivers of both age-related brain dysfunction and brain rejuvenation.

Heterochronic parabiosis reprograms the mouse brain transcriptome by shifting aging signatures in multiple cell types

Aging is a complex process involving transcriptomic changes associated with deterioration across multiple tissues and organs, including the brain. Recent studies using heterochronic parabiosis have shown that various aspects of aging-associated decline are modifiable or even reversible. To better understand how this occurs, we performed single-cell transcriptomic profiling of young and old mouse brains after parabiosis. For each cell type, we cataloged alterations in gene expression, molecular pathways, transcriptional networks, ligand-receptor interactions and senescence status. Our analyses identified gene signatures, demonstrating that heterochronic parabiosis regulates several hallmarks of aging in a cell-type-specific manner. Brain endothelial cells were found to be especially malleable to this intervention, exhibiting dynamic transcriptional changes that affect vascular structure and function. These findings suggest new strategies for slowing deterioration and driving regeneration in the aging brain through approaches that do not rely on disease-specific mechanisms or actions of individual circulating factors.

MeCP2 regulates Gdf11, a dosage-sensitive gene critical for neurological function

Loss- and gain-of-function of MeCP2 causes Rett syndrome (RTT) and MECP2 duplication syndrome (MDS), respectively. MeCP2 binds methyl-cytosines to finely tune gene expression in the brain, but identifying genes robustly regulated by MeCP2 has been difficult. By integrating multiple transcriptomics datasets, we revealed that MeCP2 finely regulates growth differentiation factor 11 (Gdf11). Gdf11 is down-regulated in RTT mouse models and, conversely, up-regulated in MDS mouse models. Strikingly, genetically normalizing Gdf11 dosage levels improved several behavioral deficits in a mouse model of MDS. Next, we discovered that losing one copy of Gdf11 alone was sufficient to cause multiple neurobehavioral deficits in mice, most notably hyperactivity and decreased learning and memory. This decrease in learning and memory was not due to changes in proliferation or numbers of progenitor cells in the hippocampus. Lastly, loss of one copy of Gdf11 decreased survival in mice, corroborating its putative role in aging. Our data demonstrate that Gdf11 dosage is important for brain function.

Systemic GDF11 attenuates depression-like phenotype in aged mice via stimulation of neuronal autophagy

Cognitive decline and mood disorders increase in frequency with age. Many efforts are focused on the identification of molecules and pathways to treat these conditions. Here, we demonstrate that systemic administration of growth differentiation factor 11 (GDF11) in aged mice improves memory and alleviates senescence and depression-like symptoms in a neurogenesis-independent manner. Mechanistically, GDF11 acts directly on hippocampal neurons to enhance neuronal activity via stimulation of autophagy. Transcriptomic and biochemical analyses of these neurons reveal that GDF11 reduces the activity of mammalian target of rapamycin (mTOR), a master regulator of autophagy. Using a murine model of corticosterone-induced depression-like phenotype, we also show that GDF11 attenuates the depressive-like behavior of young mice. Analysis of sera from young adults with major depressive disorder (MDD) reveals reduced GDF11 levels. These findings identify mechanistic pathways related to GDF11 action in the brain and uncover an unknown role for GDF11 as an antidepressant candidate and biomarker.

Anatomical biology guides a search for nutrients for the aging brain

Considerable evidence has established the importance of specific nutrients that have been found vital for the developing brain. We hypothesize that in a similar manner there should be nutrients vital to the aging brain and that based on aging's distinct pathophysiology they should be different than those essential to development. Specific brain networks that govern cognition are particularly vulnerable to the aging process, resulting in what is referred to as 'cognitive aging'. Common late-life disorders, however, such as Alzheimer's disease also target these same brain networks. Studies have disambiguated cognitive aging from late-life disease by isolating regions and biological pathways within each network differentially linked to one or the other. This anatomical biology anchors a framework to identify nutrients and/or dietary bioactives relevant to cognitive aging whose utility is illustrated via a decades-long research program into how dietary bioactive flavanols benefit the brain. As we are living longer in cognitively more demanding lives, the framework's ultimate goal is to generate specific dietary recommendations that will fortify our mind for its golden years.

Modifying enzyme replacement therapy - A perspective

Several diseases are caused by the lack of functional proteins, including lysosomal storage diseases or haemophilia A and B. Patients suffering from one of these diseases are treated via enzyme replacement therapies to restore the missing protein. Although this treatment strategy prevents some disease symptoms, enzyme replacement therapies are very expensive and require very frequent infusions, which can cause infusion adverse reactions and massively impair the quality of life of the patients. This review proposes a technology to sustainably produce proteins within the patient to potentially make frequent protein-infusions redundant. This technology is based on blood circulating immune cells as producers of the needed therapeutic protein. To ensure a stable protein concentration over time the cells are equipped with a system, which induces cell proliferation when low therapeutic protein levels are detected and a system inhibiting cell proliferation when high therapeutic protein levels are detected.

CircNUFIP2 overexpression induces GDF11 to ameliorate oxygen-glucose deprivation-induced hippocampal neuron cell apoptosis and oxidative stress after cerebral ischemia

Background Previous data have indicated the regulation of circular RNA (circRNA) toward cerebral ischemia. This study aims to reveal the effects of circNUFIP2 on cerebral ischemia and the underlying mechanism. Methods Oxygen-glucose deprivation (OGD) hippocampal neuron (HT22) cell model and middle cerebral artery occlusion (MCAO) mouse model were used for this study. The expression of circRNA nuclear FMR1 interacting protein 2 (circNUFIP2), microRNA-1224-5p (miR-1224-5p) and growth differentiation factor 11 (GDF11) was detected by quantitative real-time polymerase-chain reaction. Protein expression was checked by Western blotting. The binding relationships among circNUFIP2, miR-1224-5p and GDF11 were identified by dual-luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation assay. Cell proliferation and apoptosis were investigated by 5-Ethynyl-29-deoxyuridine and flow cytometry analysis, respectively. Results CircNUFIP2 and GDF11 expression were decreased, but miR-1224-5p was increased in OGD-treated HT22 cells when compared with their expression in control groups. OGD treatment inhibited HT22 cell proliferation but induced cell apoptosis and oxidative stress; however, these effects were attenuated after circNUFIP2 overexpression. Also, circNUFIP2 upregulation assuaged the cerebral infarction of MCAO mice. Besides, circNUFIP2 bound to miR-1224-5p and mediated OGD-induced HT22 cell damage through miR-1224-5p. Meanwhile, knockdown of GDF11, a target gene of miR-1224-5p, relieved miR-1224-5p depletion-caused effects in OGD-treated HT22 cells. Furthermore, circNUFIP2 regulated GDF11 expression by interacting with miR-1224-5p. Conclusion CircNUFIP2 overexpression protected neuron cells against cerebral ischemia-induced damage, at least in part, by the miR-1224-5p/GDF11 pathway, providing a possible target for the therapy of cerebral ischemic stroke.

Acute endurance exercise modulates growth differentiation factor 11 in cerebrospinal fluid of healthy young adults

OBJECTIVE

Strong evidence supports the benefits of exercise for healthy ageing, including reduced risk of neurodegenerative diseases. Recent studies suggested interorgan crosstalk as a key element of systemic adaptive response, however, the role of specific molecules in mediating exercise effects on the human brain are not fully understood. In the present study, we explored the exercise-related regulation of Growth Differentiation Factor 11 (GDF11) in cerebrospinal fluid (CSF) and blood.

METHODS

The samples of serum, plasma and CSF were obtained before and 60min after acute exercise (90min run) from twenty healthy young individuals. Additional serum and plasma samples were collected immediately after run. GDF11 protein content (immunoblotting), body composition (bioelectrical impedance), physical fitness (VO₂max, cycle spiroergometry) and cognitive functions (standardized computerized tests, Cogstate) were evaluated.

RESULTS

Running decreased GDF11 protein content in CSF (-20.6%. p=0.046), while GDF11 in plasma and serum were not regulated. Two GDF11-specific antibodies of different origin were used to corroborate this result. Individuals with higher physical fitness displayed greater exercise-induced decrease of GDF11 in CSF than those with lower physical fitness (p=0.025). VO₂max correlated positively with GDF11 in serum (r=0.63, p=0.020) as well as with the exercise-induced change in GDF11 levels in CSF (r=0.59, p=0.042). Indirect measure of blood-brain barrier permeability (i.e. CSF/serum albumin ratio) tended to positively correlate with CSF/serum GDF11 ratio (p=0.060). CSF levels of GDF11 correlated positively with cognitive functions, including working memory, both before and after run (p<0.05).

CONCLUSION

Running-induced down-regulation of the GDF11 protein in the cerebrospinal fluid of healthy young individuals indicates the potential role of GDF11 in the exercise-induced cross-talk between periphery and the brain.

Multifaceted Benefits of GDF11 Treatment in Spinal Cord Injury: In Vitro and In Vivo Studies

Traumatic spinal cord injury (SCI) initiates a series of cellular and molecular events that include both primary and secondary injury cascades. This secondary cascade provides opportunities for the delivery of therapeutic intervention. Growth differentiation factor 11 (GDF11), a member of the transforming growth factor-β (TGF-β) superfamily, regulates various biological processes in mammals. The effects of GDF11 in the nervous system were not fully elucidated. Here, we perform extensive in vitro and in vivo studies to unravel the effects of GDF11 on spinal cord after injury. In vitro culture studies showed that GDF11 increased the survival of both neuronal and oligodendroglial cells but decreased microglial cells. In stressed cultures, GDF11 effectively inhibited LPS stimulation and also protected neurons from ischemic damage. Intravenous GDF11 administration to rat after eliciting SCI significantly improved hindlimb functional restoration of SCI rats. Reduced neuronal connectivity was evident at 6 weeks post-injury and these deficits were markedly attenuated by GDF11 treatment. Furthermore, SCI-associated oligodendroglial alteration were more preserved by GDF11 treatment. Taken together, GDF11 infusion via intravenous route to SCI rats is beneficial, facilitating its therapeutic application in the future.

Spermidine inhibits high glucose-induced endoplasmic reticulum stress in HT22 cells by upregulation of growth differentiation factor 11

Hyperglycemia-induced neuronal endoplasmic reticulum (ER) stress is particularly important for the pathogenesis of diabetic encephalopathy. Spermidine (Spd) has neuroprotection in several nervous system diseases. Our current study to explore the potential protective role of Spd in hyperglycemia-induced neuronal ER stress and the underlying mechanisms. HT22 cells were treated with high glucose (HG) to establish an in-vitro model of hyperglycemia toxicity. The HT22 cells' activity was tested by cell counting kit-8 assay. RNA interference technology was used to silence the expression of growth differentiation factor 11 (GDF11) in HT22 cells. The GDF11 expression levels of mRNA were assessed using reverse transcription-PCR (RT-PCR). Western blotting analysis was applied to evaluate the expressions of GRP78 and cleaved caspase-12. Spd markedly abolished HG-exerted decline in cell viability as well as upregulations of GRP78 and cleaved caspase-12 in HT22 cells, indicating the protection of Spd against HG-induced neurotoxicity and ER stress. Furthermore, we showed that Spd upregulated the expression of GDF11 in HG-exposed HT22 cells. While, silenced GDF11 expression by RNA interference reversed the protective effects of Spd on HG-elicited neurotoxicity and ER stress in HT22 cells. These results indicated that Spd prevents HG-induced neurotoxicity and ER stress through upregulation of GDF11. Our findings identify Spd as a potential treatment for diabetic encephalopathy as well as ER stress-related neurologic diseases.

GDF11 Regulates PC12 Neural Stem Cells via ALK5-Dependent PI3K-Akt Signaling Pathway

Growth differentiation factor 11 (GDF11), belonging to the transforming factor-β superfamily, regulates anterior-posterior patterning and inhibits neurogenesis during embryonic development. However, recent studies recognized GDF11 as a rejuvenating (or anti-ageing) factor to reverse age-related cardiac hypertrophy, repair injured skeletal muscle, promote cognitive function, etc. The effects of GDF11 are contradictory and the mechanism of action is still not well clarified. The objective of the present study was to investigate effects of GDF11 on PC12 neural stem cells in vitro and to reveal the underlying mechanism. We systematically assessed the effects of GDF11 on the life activities of PC12 cells. GDF11 significantly suppressed cell proliferation and migration, promoted differentiation and apoptosis, and arrested cell cycle at G2/M phase. Both TMT-based proteomic analysis and phospho-antibody microarray revealed PI3K-Akt pathway was enriched when treated with GDF11. Inhibition of ALK5 or PI3K obviously attenuated the effects of GDF11 on PC12 neural stem cells, which exerted that GDF11 regulated neural stem cells through ALK5-dependent PI3K-Akt signaling pathway. In summary, these results demonstrated GDF11 could be a negative regulator for neurogenesis via ALK5 activating PI3K-Akt pathway when it directly acted on neural stem cells.

Beyond Static Pipes: Mechanisms and In Vitro Models of Vascular Aging

The vascular system is a key player for the maintenance of healthy tissues, suggesting how the physiological decline of blood vessel functionality during aging could be a major contributor of organ degeneration. While basic research studies have begun to pinpoint potential mechanisms of vascular aging, it is now critical to translate them into therapeutically relevant options. Microphysiological systems represent a powerful tool to precisely control which combinations of stimuli are provided to in vitro reconstructed blood vessels and to analyze their functional consequences. After highlighting key aspects of vascular aging, this review discusses in vitro models that are able to recapitulate relevant features of blood vessel damage during aging. Strategies to improve current in vitro systems so that they will more faithfully recapitulate vascular aging are proposed, emphasizing the importance of combining in vivo models with microphysiological systems for an effective translation of vascular aging biomarkers and therapies to the clinical level.

Dietary intake of GDF11 delays the onset of several biomarkers of aging in male mice through anti-oxidant system via Smad2/3 pathway

Current studies have generated controversy over the age-related change in concentration of growth differentiation factor 11 (GDF11) and its role in the genesis of rejuvenation conditions. In this study, we displayed rGDF11 on the surface of Yarrowic Lipolytica (Y. lipolytica), and proved the bioavailability of the yeast-displayed rGDF11 by oral delivery in aged male mice. On the basis of these findings, we started to explore the anti-aging activity and underlying mechanisms of displayed rGDF11. It was found that dietary intake of displayed rGDF11 had little influence on the body weight and biochemical parameters of aged male mice, but delayed the occurrence and development of age-related biomarkers such as lipofuscin (LF) and senescence-associated-β-galactosidase, and to some extent, prolonged the lifespan of aged male mice. Moreover, we demonstrated once again that dietary intake of displayed rGDF11 enhanced the activity of anti-oxidant enzymes, including catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX), reduced the reactive oxygen species (ROS) level, and slowed down the protein oxidation and lipid peroxidation. Importantly, we showed for the first time that rGDF11 enhanced the activity of CAT, SOD and GPX through activation of the Smad2/3 signaling pathway. Our study also provided a simple and safe route for delivery of recombinant GDF11, facilitating its therapeutic application in the future.

Potential role of recombinant growth differentiation factor 11 in Alzheimer’s disease treatment

Alzheimer's disease (AD) is a neurodegenerative disease closely related to the accumulation of beta-amyloid (Aβ) plaques. Growth differentiation factor 11 (GDF11) is one of the proteins that play a role in the aggravation of AD. Decreased concentration of GDF11 disrupts regenerative nervous system, blood vessels, and various vital systems. Low levels of GDF11 with age can be overcome with recombinant GDF11 (rGDF11) to rejuvenate the regenerative effect. Based on research results, rGDF11 enhance the proliferation rate of neuronal precursor cells as well as angiogenesis. rGDF11 can replace lost levels of GDF11, overcome astrogliosis and activation of nerve cell microglia. Therapeutic effect of rGDF11 leads to an improved prognosis in AD patients by neurogenesis and angiogenesis. The prospects of rGDF11 in the treatment of AD have great potential for further research in the future.

The emerging translational potential of GDF11 in chronic wound healing

Chronic skin wounds impose immense suffers and economic burdens. Current research mainly focuses on acute wound management which exhibits less effective in chronic wound healing. Growth differentiation factor 11 (GDF11) has profound effects on several important physiological processes related to chronic wound healing, such as inflammation, cell proliferation, migration, angiogenesis, and neurogenesis. This review summarizes recent advances in biology of chronic wounds and the potential role of GDF11 on wound healing with its regenerative effects, as well as the potential delivery methods of GDF11. The challenges and future perspectives of GDF11-based therapy for chronic wound care are also discussed. The Translational Potential of this Article: This review summarized the significance of GDF11 in the modulation of inflammation, vascularization, cell proliferation, and remodeling, which are important physiological processes of chronic wound healing. The potential delivery methods of GDF11 in the management of chronic wound healing is also summarized. This review may provide potential therapeutic approaches based on GDF11 for chronic wound healing.

Accumulation of systematic TPM1 mediates inflammation and neuronal remodeling by phosphorylating PKA and regulating the FABP5/NF-κB signaling pathway in the retina of aged mice

The molecular mechanisms underlying functional decline during normal brain aging are poorly understood. Here, we identified the actin‐associated protein tropomyosin 1 (TPM1) as a new systemic pro‐aging factor associated with function deficits in normal aging retinas. Heterochronic parabiosis and blood plasma treatment confirmed that systemic factors regulated age‐related inflammatory responses and the ectopic dendritic sprouting of rod bipolar (RBC) and horizontal (HC) cells in the aging retina. Proteomic analysis revealed that TPM1 was a potential systemic molecule underlying structural and functional deficits in the aging retina. Recombinant TPM1 protein administration accelerated the activation of glial cells, the dendritic sprouting of RBCs and HCs and functional decline in the retina of young mice, whereas anti‐TPM1 neutralizing antibody treatment ameliorated age‐related structural and function changes in the retina of aged mice. Old mouse plasma (OMP) induced glial cell activation and the dendritic outgrowth of RBCs and HCs in young mice, and yet TMP1‐depleted OMP failed to reproduce the similar effect in young mice. These results confirmed that TPM1 was a systemic pro‐aging factor. Moreover, we demonstrated that systematic TPM1 was an immune‐related molecule, which elicited endogenous TPM1 expression and inflammation by phosphorylating PKA and regulating FABP5/NF‐κB signaling pathway in normal aging retinas. Interestingly, we observed TPM1 upregulation and the ectopic dendritic sprouting of RBCs and HCs in young mouse models of Alzheimer's disease, indicating a potential role of TPM1 in age‐related neurodegenerative diseases. Our data indicate that TPM1 could be targeted for combating the aging process.

Hippocampus and its involvement in Alzheimer's disease: a review

Hippocampus is the significant component of the limbic lobe, which is further subdivided into the dentate gyrus and parts of Cornu Ammonis. It is the crucial region for learning and memory; its sub-regions aid in the generation of episodic memory. However, the hippocampus is one of the brain areas affected by Alzheimer's (AD). In the early stages of AD, the hippocampus shows rapid loss of its tissue, which is associated with the functional disconnection with other parts of the brain. In the progression of AD, atrophy of medial temporal and hippocampal regions are the structural markers in magnetic resonance imaging (MRI). Lack of sirtuin (SIRT) expression in the hippocampal neurons will impair cognitive function, including recent memory and spatial learning. Proliferation, differentiation, and migrations are the steps involved in adult neurogenesis. The microglia in the hippocampal region are more immunologically active than the other regions of the brain. Intrinsic factors like hormones, glia, and vascular nourishment are instrumental in the neural stem cell (NSC) functions by maintaining the brain's microenvironment. Along with the intrinsic factors, many extrinsic factors like dietary intake and physical activity may also influence the NSCs. Hence, pro-neurogenic lifestyle could delay neurodegeneration.

Characterization of the neurogenic niche in the aging dentate gyrus using iterative immunofluorescence imaging

Advancing age causes reduced hippocampal neurogenesis, associated with age-related cognitive decline. The spatial relationship of age-induced alterations in neural stem cells (NSCs) and surrounding cells within the hippocampal niche remains poorly understood due to limitations of antibody-based cellular phenotyping. We established iterative indirect immunofluorescence imaging (4i) in tissue sections, allowing for simultaneous detection of 18 proteins to characterize NSCs and surrounding cells in 2-, 6-, and 12-month-old mice. We show that reorganization of the dentate gyrus (DG) niche already occurs in middle-aged mice, paralleling the decline in neurogenesis. 4i-based tissue analysis of the DG identifies changes in cell-type contributions to the blood-brain barrier and microenvironments surrounding NSCs to play a pivotal role to preserve neurogenic permissiveness. The data provided represent a resource to characterize the principles causing alterations of stem cell-associated plasticity within the aging DG and provide a blueprint to analyze somatic stem cell niches across lifespan in complex tissues.

Potential Application of Low-Intensity Pulsed Ultrasound in Delaying Aging for Mice

INTRODUCTION

The low-intensity pulsed ultrasound (LIPUS) is one of the popular treatment modalities allowing to boost the proliferation, differentiation, and migratory activity of cells, which might be a powerful strategy for anti-aging. Seeking a novel setup for LIPUS would benefit the development of ultrasound therapeutics.

METHODS

Here, we proposed a novel underwater exposure setup of LIPUS. C57BL/6 mice were reared in the designated age-groups, which consisted of a middle-aged group (12-14 months) and an old-age group (20-23 months). The age-related changes of body composition, imbalance of energy supply and demand, imbalance of signal network maintaining internal stability, and representative phenotypes of neurodegeneration and neuroplasticity with the presence and absence of underwater LIPUS in middle-aged and aged groups were evaluated.

RESULTS

The results showed that there were obvious aging changes, imbalance of energy supply and demand, imbalance of signal network maintaining homeostasis, neurodegeneration, and damage of neural plasticity in the middle-aged and aged group with or without the LIPUS. Although middle-aged group and aged group responded differently to LIPUS, they mostly generated positive results in relieving bone loss, improving ovarian structure, regulated immune system, and enhanced endurance ability, which should have declined over age.

DISCUSSION

These findings indicate that underwater extracorporeal LIPUS exposure could be employed as single or combined anti-aging strategies that generated positive outcomes against the process of aging.

In situ slow-release recombinant growth differentiation factor 11 exhibits therapeutic efficacy in ischemic stroke

Systemic growth differentiation factor 11 (GDF11) treatment improves the vasculature in the hippocampus and cortex in mice in recent studies. However, systemic application of recombinant GDF11 (rGDF11) cannot cross the brain blood barrier (BBB). Thus, large doses and long-term administration are required, while systemically applied high-dose rGDF11 is associated with deleterious effects, such as severe cachexia. This study tested whether in situ low dosage rGDF11 (1 μg/kg) protects the brain against ischemic stroke and it investigated the underlying mechanisms. Fibrin glue mixed with rGDF11 was applied to the surgical cortex for the slow release of rGDF11 in mice after permanent middle cerebral artery occlusion (MCAO). In situ rGDF11 improved cerebral infarction and sensorimotor function by upregulating Smad2/3 and downregulating FOXO3 expression. In situ rGDF11 was associated with reductions in protein and lipid oxidation, Wnt5a, iNOS and COX2 expression, at 24 h after injury. In situ rGDF11 protected hippocampal neurons and subventricular neural progenitor cells against MCAO injury, and increased newborn neurogenesis in the peri-infarct cortex. Systematic profiling and qPCR analysis revealed that Pax5, Sox3, Th, and Cdk5rap2, genes associated with neurogenesis, were increased by in situ rGDF11 treatment. In addition, greater numbers of newborn neurons in the peri-infarct cortex were observed with in situ rGDF11 than with systemic application. Our evidence indicates that in situ rGDF11 effectively decreases the extent of damage after ischemic stroke via antioxidative, anti-inflammatory and proneurogenic activities. We suggest that in situ slow-release rGDF11 with fibrin glue is a potential therapeutic approach against ischemic stroke.

GDF11 expressed in the adult brain negatively regulates hippocampal neurogenesis

Growth differentiation factor 11 (GDF11) is a transforming factor-β superfamily member that functions as a negative regulator of neurogenesis during embryonic development. However, when recombinant GDF11 (rGDF11) is administered systemically in aged mice, it promotes neurogenesis, the opposite of its role during development. The goal of the present study was to reconcile this apparent discrepancy by performing the first detailed investigation into the expression of endogenous GDF11 in the adult brain and its effects on neurogenesis. Using quantitative histological analysis, we observed that Gdf11 is most highly expressed in adult neurogenic niches and non-neurogenic regions within the hippocampus, choroid plexus, thalamus, habenula, and cerebellum. To investigate the role of endogenous GDF11 during adult hippocampal neurogenesis, we generated a tamoxifen inducible mouse that allowed us to reduce GDF11 levels. Depletion of Gdf11 during adulthood increased proliferation of neural progenitors and decreased the number of newborn neurons in the hippocampus, suggesting that endogenous GDF11 remains a negative regulator of hippocampal neurogenesis in adult mice. These findings further support the idea that circulating systemic GDF11 and endogenously expressed GDF11 in the adult brain have different target cells or mechanisms of action. Our data describe a role for GDF11-dependent signaling in adult neurogenesis that has implications for how GDF11 may be used to treat CNS disease.

Einstein-Nathan Shock Center: translating the hallmarks of aging to extend human health span

The overarching mission of the Einstein-Nathan Shock Center (E-NSC) is to make scientific discoveries in geroscience, leveraging on the expertise in our center in 6 out of the 7 pillars of aging, and to translate their effects towards drug discovery. The relevance of this basic biology of aging discoveries to humans will be confirmed through the unique gero-human resource at E-NSC. This is achieved through services provided by E-NSC, connectivity among its members, attracting worldwide investigators, and providing them with the opportunities to become future leaders. The two central components of the E-NSC are (a) cutting-edge research programs and (b) unique E-NSC research support cores. E-NSC scientists lead NIH-supported cutting-edge research programs that integrate key hallmarks of aging including proteostasis/autophagy, metabolism/inflammaging, genetic/epigenetics, stem cells/regeneration, and translational aging/longevity. Since the inception of the E-NSC, the well-integrated, collaborative, and innovative nature of the multiple supporting state-of-the-art E-NSC research cores form the bedrock of research success at the E-NSC. The three state-of-the-art E-NSC research cores, (i) Proteostasis of Aging Core (PAC), (ii) the Health Span Core (HSC), and (iii) the Human Multi-Omics Core (HMOC), have allowed impressive expansion of translational biological research programs. Expansion was facilitated through the wealth of data coming from genomics/proteomics and metabolomic analysis on human longevity studies, due to access to a variety of biological samples from elderly subjects in clinical trials with aging-targeting drugs, and new drug design services via the PAC to target the hallmarks of aging.