A single-nucleus transcriptomic atlas of primate liver aging uncovers the pro-senescence role of SREBP2 in hepatocytes

Aging increases the risk ofliver diseases and systemic susceptibility to aging-related diseases.However,cell type-specific changes and the underlying mechanism of liver aging in higher vertebrates remain incompletely characterized.Here,we constructed the first single-nucleus transcriptomic landscape of primate liver aging,in which we resolved cell type-specific gene expression fluctuation in hepatocytes across three liver zonations and detected aberrant cell-cell interactions between hepatocytes and niche cells.Upon in-depth dissection of this rich dataset,we identifed impaired lipid metabolism and upregulation of chronic inflammation-related genes prominently associated with declined liver functions during aging.In particular,hyperactivated sterol regulatory element-binding protein(SREBP)signaling was a hallmark of the aged liver,and consequently,forced activation of SREBP2 in human primary hepatocytes recapitulated in vivo aging phenotypes,manifesting as impaired detoxification and accelerated cellular senescence.This study expands our knowledge of primate liver aging and informs the development of diagnostics and therapeutic interventions for liver aging and associated diseases.

MAVS Antagonizes Human Stem Cell Senescence as a Mitochondrial Stabilizer

Mitochondrial dysfunction is a hallmark feature of cellular senescence and organ aging.Here,we asked whether the mitochondrial antiviral signaling protein(MAVS),which is essential for driving antiviral response,also regulates human stem cell senescence.To answer this question,we used CRISPR/Cas9-mediated gene editing and directed differentiation techniques to generate various MAVS-knockout human stem cell models.We found that human mesenchymal stem cells(hMSCs)were sensitive to MAVS deficiency,as manifested by accelerated senescence phenotypes.We uncovered that the role of MAVS in maintaining mitochondrial structural integrity and functional homeostasis depends on its interaction with the guanosine triphosphatase optic atrophy type 1(OPA1).Depletion of MAVS or OPA1 led to the dysfunction of mitochondria and cellular senescence,whereas replenishment of MAVS or OPA1 in MAVS-knockout hMSCs alleviated mitochondrial defects and premature senescence phenotypes.Taken together,our data underscore an uncanonical role of MAVS in safeguarding mitochondrial homeostasis and antagonizing human stem cell senescence.

Human ESC-derived vascular cells promote vascular regeneration in a HIF-1α dependent manner

Hypoxia-inducible factor(HIF-1α),a core transcription factor responding to changes in cellular oxygen levels,is closely associated with a wide range of physiological and pathological conditions.However,its differential impacts on vascular cell types and molecular programs modulating human vascular homeostasis and regeneration remain largely elusive.Here,we applied CRISPR/Cas9-mediated gene editing of human embryonic stem cells and directed differentiation to generate HIF-ia-deficient human vascular cells including vascular endothelial cells,vascular smooth muscle cells,and mesenchymal stem cells(MsCs),as a platform for discovering cell type-specific hypox-ia-induced response mechanisms.Through comparative molecular profiling across cell types under normoxic and hypoxic conditions,we provide insight into the indispensable role of HIF-1αin the promotion of ischemic vascular regeneration.We found human MSCs to be the vascular cell type most susceptible to HIF-1a deficiency,and that transcriptional inactivation of ANKZF1,an effector of HIF-1a,impaired pro-angiogenic processes.Altogether,our findings deepen the understanding of HIF-ia in human angiogenesis and support further explorations of novel therapeutic strategies of vascular regeneration against ischemic damage.

Single-nucleus profiling unveils a geroprotective role of the Foxo3 in primate skeletal muscle aging

Age-dependent loss of skeletal muscle mass and function is a feature of sarcopenia,and increases the risk of many aging-related metabolic diseases.Here,we report phenotypic and single-nucleus transcriptomic analyses of non-human primate skeletal muscle aging.A higher transcriptional fluctuation was observed in myonuclei relative to other interstitial cell types,indicating a higher susceptibility of skeletal muscle fiber to aging.We found a downregulation of Foxo3 in aged primate skeletal muscle,and identi-fied FOxo3 as a hub transcription factor maintaining skeletal muscle homeostasis.Through the establishment of a complementary experimental pipeline based on a human pluripotent stem cell-derived myotube model,we revealed that silence of Foxo3 accelerates human myotube senescence,whereas genetic activation of endogenous FOxO3 alleviates human myotube aging.Altogether,based on a combination of monkey skeletal muscle and human myotube aging research models,we unraveled the pivotal role of the FOxO3 in safeguarding primate skeletal muscle from aging,providing a comprehensive resource for the development of clinical diagnosis and targeted therapeutic interventions against human skeletal muscle aging and the onset of sarcopenia along with aging-relateddisorders.

A single-nucleus transcriptomic atlas of primate testicular aging reveals exhaustion of the spermatogonial stem cell reservoir and loss of Sertoli cell homeostasis

The testis is pivotal for male reproduction,and its progressive functional decline in aging is associated with infertility.However,the regulatory mechanism underlying primate testicular aging remains largely elusive.Here,we resolve the aging-related cellular and molecular alterations of primate testicular aging by establishing a single-nucleus transcriptomic atlas.Gene-expression patterns along the spermatogenesis trajectory revealed molecular programs associated with attrition of spermatogonial stem cell reservoir,disturbed meiosis and impaired spermiogenesis along the sequential continuum.Remarkably,Sertoli cell was identified as the cell type most susceptible to aging,given its deeply perturbed age-associated transcriptional profiles.Concomitantly,downregulation of the transcription factor Wilms'Tumor 1(WTi),essential for Sertoli cell homeostasis,was associated with accelerated cellular senescence,disrupted tight junctions,and a compromised cell identity signature,which altogether may help create a hostile microenvironment for spermatogenesis.Collectively,our study depicts in-depth transcriptomic traits of non-human primate(NHP)testicular aging at single-cell resolution,providing potential diagnostic biomarkers and targets for therapeutic interventions against testicular aging and age-related male reproductive diseases.

Single-cell profiling reveals a potent role of quercetin in promoting hair regeneration

Hair loss affects millions of people at some time in their life,and safe and efficient treatments for hair loss are a significant unmet medical need.We report that topical delivery of quercetin(Que)stimulates resting hair follicles to grow with rapid follicular keratinocyte proliferation and replenishes perifollicular microvasculature in mice.We construct dynamic single-cell transcriptome landscape over the course of hair regrowth and find that Que treatment stimulates the differentiation trajectory in the hair follicles and induces an angiogenic signature in dermal endothelial cells by activating HIF-1αin endothelial cells.Skin administration of a HIF-1αagonist partially recapitulates the pro-angiogenesis and hair-growing effects of Que.Together,these findings provide a molecular understanding for the efficacy of Que in hair regrowth,which underscores the translational potential of targeting the hair follicle niche as a strategy for regenerative medicine,and suggest a route of pharmacological intervention that may promote hair regrowth.