Metformin protects lens epithelial cells against senescence in a naturally aged mouse model

The senescence of lens epithelial cells (LECs) is a major factor leading to age-related cataract (ARC). ARC results in visual impairment and severe vision loss in elderly patients. However, the specific mechanism of ARC remains unclear, and there are no effective therapeutic agents to halt the formation of ARC. This study aimed to assess the underlying mechanism of the formation of ARC and investigate the potential anti-ageing effect of metformin (MET) on ARC. Male C57BL/6 mice were divided into three groups: the control group having young mice (3 months old, n = 40), the naturally aged group (aged 20 months, n = 60) and the MET group (MET, 20 months, n = 60). Mice in the control and the naturally aged groups were fed a standard purified mouse diet ad libitum and water, whereas those in the MET group were fed chows supplemented with 0.1% MET for 10 months. The transparency of the lens and age-associated proteins p21 and p53 were analysed in the LECs of these three groups. Furthermore, we determined the expressions of the adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway and the effect of MET on this pathway in LECs during the ageing process of ARC. In addition, the relationship between autophagy and the senescence of LECs and the role of MET in the autophagy of LECs during the ageing process of ARC were examined. Our results indicated that age-related inactivation of the AMPK pathway and impairment of autophagy might contribute to the senescence of LECs and the occurrence of ARC. More importantly, these results demonstrated that MET effectively alleviated the senescence of LECs and the formation of ARC probably via inactivation of the AMPK pathway and augmentation of autophagy. These findings revealed that MET can be exploited as a potentially useful drug for ARC prevention. Our study will help in enlightening the development of innovative strategies for the clinical treatment of ARC.

Single-Cell Analysis Identify Transcription Factor BACH1 as a Master Regulator Gene in Vascular Cells During Aging

Vascular aging is a potent driver of cardiovascular and cerebrovascular diseases. Vascular aging features cellular and functional changes, while its molecular mechanisms and the cell heterogeneity are poorly understood. This study aims to 1) explore the cellular and molecular properties of aged cardiac vasculature in monkey and mouse and 2) demonstrate the role of transcription factor BACH1 in the regulation of endothelial cell (EC) senescence and its mechanisms. Here we analyzed published single-cell RNA sequencing (scRNA-seq) data from monkey coronary arteries and aortic arches and mouse hearts. We revealed that the gene expression of YAP1, insulin receptor, and VEGF receptor 2 was downregulated in both aged ECs of coronary arteries’ of monkey and aged cardiac capillary ECs of mouse, and proliferation-related cardiac capillary ECs were significantly decreased in aged mouse. Increased interaction of ECs and immunocytes was observed in aged vasculature of both monkey and mouse. Gene regulatory network analysis identified BACH1 as a master regulator of aging-related genes in both coronary and aorta ECs of monkey and cardiac ECs of mouse. The expression of BACH1 was upregulated in aged cardiac ECs and aortas of mouse. BACH1 aggravated endothelial cell senescence under oxidative stress. Mechanistically, BACH1 occupied at regions of open chromatin and bound to CDKN1A (encoding for P21) gene enhancers, activating its transcription in senescent human umbilical vein endothelial cells (HUVECs). Thus, these findings demonstrate that BACH1 plays an important role in endothelial cell senescence and vascular aging.

Fermented Antler Recovers Stamina, Muscle Strength and Muscle Mass in Middle-Aged Mice

In a previous study, we found that Lactobacillus curvatus HY7602-fermented antler (FA) improved exercise endurance by increasement of muscle mass and strength in a young mouse model. In this study, we investigated the effect of FA on recovery of muscle mass and strength in aging-induced muscle loss. We have used a middle-aged model in which muscle decline begins in many mammalian species. All mice performed treadmill exercise and forced swimming, and measured muscle grip strength. Then, calf muscle weight and histological analysis, blood biomarker and gene expression in soleus muscle tissue were measured. Muscle strength and forced swimming time were significantly increased in the FA-intake groups compared to controls. The levels of muscle and liver damage-related indicators (ATL, ALP, LDH and CK) and muscle endurance, fatigue and exercise performance-related indicators (lactate and creatinine) were significantly improved by FA supplementation. In addition, FA regulates genes related to muscle protein degradation (Atrogin-1 and MuRF1) and muscle fiber synthesis (MyoD and Myf5), resulting in increased muscle mass, and fiber diameter and area values. The Bax/Bcl-2 ratio, related to apoptosis in skeletal muscle was significantly decreased. These results demonstrate that FA improves exercise performance with ameliorating blood biomarkers and also increases muscle mass and muscle strength by inhibiting muscle proteolysis and promoting muscle synthesis in a middle-aged mouse.

Accumulation of Treg cells is detrimental in late-onset (aged) mouse model of multiple sclerosis

Although typically associated with onset in young adults, multiple sclerosis (MS) also attacks aged people, which is termed late-onset MS. The disease can be recapitulated and studied in the aged mouse model of experimental autoimmune encephalomyelitis (EAE). The onset of induced EAE is delayed in aged mice, but the disease severity is increased relative to standard EAE in young mice. Given that CD4+FoxP3+ regulatory T (Treg) cells play an ameliorative role in MS/EAE severity and the aged immune system accumulates Treg cells, failure of these cells to prevent or ameliorate EAE disease is enigmatic. When analyzing the distribution of Treg cells in EAE mice, the aged mice exhibited a higher proportion of polyclonal(pan) Treg cells and a lower proportion of antigen-specific-Treg cells in their periphery, but lower proportions of pan- and antigen-specific-Treg cells in the central nervous system (CNS). Furthermore, in the aged CNS, Treg cells exhibited a higher plasticity and T effector (Teff) cells exhibited a greater clonal expansion, which disrupted the Treg/Teff balance. Transiently inhibiting FoxP3 expression in peripheral Treg cells partially ameliorated the disease and corrected Treg distribution in the aged mice. These results provide evidence that accumulated aged Treg cells play a detrimental role in neuronal inflammation of aged MS.

Functional rejuvenation of aged neural stem cells by Plagl2 and anti-Dyrk1a activity

The regenerative potential of neural stem cells (NSCs) declines during aging, leading to cognitive dysfunctions. This decline involves up-regulation of senescence-associated genes, but inactivation of such genes failed to reverse aging of hippocampal NSCs. Because many genes are up-regulated or down-regulated during aging, manipulation of single genes would be insufficient to reverse aging. Here we searched for a gene combination that can rejuvenate NSCs in the aged mouse brain from nuclear factors differentially expressed between embryonic and adult NSCs and their modulators. We found that a combination of inducing the zinc finger transcription factor gene Plagl2 and inhibiting Dyrk1a, a gene associated with Down syndrome (a genetic disorder known to accelerate aging), rejuvenated aged hippocampal NSCs, which already lost proliferative and neurogenic potential. Such rejuvenated NSCs proliferated and produced new neurons continuously at the level observed in juvenile hippocampi, leading to improved cognition. Epigenome, transcriptome, and live-imaging analyses indicated that this gene combination induces up-regulation of embryo-associated genes and down-regulation of age-associated genes by changing their chromatin accessibility, thereby rejuvenating aged dormant NSCs to function like juvenile active NSCs. Thus, aging of NSCs can be reversed to induce functional neurogenesis continuously, offering a way to treat age-related neurological disorders.

Targeting cellular senescence with novel senotherapeutics by design to extend healthspan

Senescent cells accumulate with age in various tissues and organs, leading to the decline in tissue function and deterioration of many age-related diseases and aging. Senolytics have emerged as an effective therapeutic approach to eliminate senescent cells to improve aging phenotypes and associated co-morbidities. Despite their promising potential, only a handful of senolytics have been reported, including a natural flavonoid fisetin discovered by our group. Fisetin has been shown to reduce senescence, suppress age-related pathology, and extend healthspan in aged mice. However, its moderate potency, potential mutagenic risk and poor bioavailability have limited its further clinical applications. By leveraging drug design, medicinal chemistry and high-content imaging analysis, we have successfully optimized the senolytic activity of fisetin, leading to the identification of two improved fisetin senolytic analogs (FAs) with reduced toxicity in non-senescent cells. The improved senolytic activity of these FAs was demonstrated in murine and human senescent cell models as well as in accelerated aging and naturally aged mouse models. The analysis of the senolytic activity of the FAs as well as several other recently identified senolytics, including a senolytic lipid, will be presented.

Cell Senescence as a Mediator of Age-Dependent Brain Inflammation

Cellular senescence and inflammation are interconnected causes and consequences of tissue aging. Here, we implemented orthogonal approaches to study their interaction in steady-state mature and aged mouse brain. Using single cell sequencing, we identified a putative senescent microglial population, which increased in abundance with age and was characterized by increased expression of p16 and chemotactic senescence associated secretory phenotype (SASP) factors. Using p16-INK-ATTAC transgenic mice to eliminate p16ink4a-positive senescent cells and mass cytometry, we show that p16ink4a-positive cell targeting reduced the abundance of activated inflammatory cells in the aged female brain. Age-dependent declines in executive cognitive function were improved following transgenic p16ink4a-positive cell targeting, and executive function robustly correlated with inflammatory brain cell composition in females. Collectively, our findings demonstrate fundamental differences in the age- and sex-dependent brain inflammatory landscape and implicate p16ink4a-positive senescent cell targeting as a therapeutic strategy to attenuate age-related inflammation and cognitive decline.

Three-dimensional morphological analysis of spermatogenesis in aged mouse testes

Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age. To investigate changes in spermatogenesis with aging, we reconstructed the seminiferous tubules of 12 mice aged 12 to 30 months from serial sections and examined age-related and region-specific alterations in the seminiferous epithelium and spermatogenic waves in three dimensions. The basic structure of the seminiferous tubules, including the numbers of tubules, terminating points, branching points, and total tubule length, did not change with age. Age-related alterations in spermatogenesis, primarily assessed by the formation of vacuoles in Sertoli cells, were detected in the seminiferous tubules at 12 months. The proportion of altered tubule segments with impaired spermatogenesis further increased by 24 months, but remained unchanged thereafter. Altered tubule segments were preferentially distributed in tubule areas close to the rete testis and those in the center of the testis. Spermatogenic waves became shorter in length with age. These results provide a basis for examining the decline of spermatogenesis not only with aging, but also in male infertility.