Eosinophils regulate adipose tissue inflammation and sustain physical and immunological fitness in old age.

Adipose tissue eosinophils (ATEs) are important in the control of obesity-associated inflammation and metabolic disease. However, the way in which ageing impacts the regulatory role of ATEs remains unknown. Here, we show that ATEs undergo major age-related changes in distribution and function associated with impaired adipose tissue homeostasis and systemic low-grade inflammation in both humans and mice.

Brain Endothelial Cells Are Exquisite Sensors of Age-Related Circulatory Cues.

Brain endothelial cells (BECs) are key constituents of the blood-brain barrier (BBB), protecting the brain from pathogens and restricting access of circulatory factors. Yet, because circulatory proteins have prominent age-related effects on adult neurogenesis, neuroinflammation, and cognitive function in mice, we wondered whether BECs receive and potentially relay signals between the blood and brain. Using single-cell RNA sequencing of hippocampal BECs, we discover that capillary BECs-compared with arterial and venous BECs-undergo the greatest transcriptional changes in normal aging, upregulating innate immunity and oxidative stress response pathways.

Undulating changes in human plasma proteome profiles across the lifespan.

Aging is a predominant risk factor for several chronic diseases that limit healthspan. Mechanisms of aging are thus increasingly recognized as potential therapeutic targets. Blood from young mice reverses aspects of aging and disease across multiple tissues, which supports a hypothesis that age-related molecular changes in blood could provide new insights into age-related disease biology.

Aged blood impairs hippocampal neural precursor activity and activates microglia via brain endothelial cell VCAM1.

An aged circulatory environment can activate microglia, reduce neural precursor cell activity and impair cognition in mice. We hypothesized that brain endothelial cells (BECs) mediate at least some of these effects. We observe that BECs in the aged mouse hippocampus express an inflammatory transcriptional profile with focal upregulation of vascular cell adhesion molecule 1 (VCAM1), a protein that facilitates vascular-immune cell interactions.

Papain-based Single Cell Isolation of Primary Murine Brain Endothelial Cells Using Flow Cytometry.

Brain endothelial cells (BECs) form the integral component of the blood-brain barrier (BBB) which separates the systemic milieu from the brain parenchyma and protects the brain from pathogens and circulating factors. In order to study BEC biology, it was of particular interest to establish a method that enables researchers to investigate and understand the underlying molecular mechanisms regulating their function during homeostasis, aging and disease. Furthermore, due to the heterogeneity of the cerebrovasculature and different vessel types that comprise the BBB, it is of particular interest to isolate primary BECs for single cell analysis from various subregions of the brain, such as the neurogenic and highly vascularized hippocampus and to enrich for specific vessel types.

Collagenase-based Single Cell Isolation of Primary Murine Brain Endothelial Cells Using Flow Cytometry.

The brain endothelium is a highly specialized vascular structure that maintains the activity and integrity of the central nervous system (CNS). Previous studies have reported that the integrity of the brain endothelium is compromised in a plethora of neuropathologies. Therefore, it is of particular interest to establish a method that enables researchers to investigate and understand the molecular changes in CNS endothelial cells and underlying mechanisms in conjunction with murine models of disease.

Systemic attenuation of the TGF-β pathway by a single drug simultaneously rejuvenates hippocampal neurogenesis and myogenesis in the same old mammal.

Stem cell function declines with age largely due to the biochemical imbalances in their tissue niches, and this work demonstrates that aging imposes an elevation in transforming growth factor β (TGF-β) signaling in the neurogenic niche of the hippocampus, analogous to the previously demonstrated changes in the myogenic niche of skeletal muscle with age. Exploring the hypothesis that youthful calibration of key signaling pathways may enhance regeneration of multiple old tissues, we found that systemically attenuating TGF-β signaling with a single drug simultaneously enhanced neurogenesis and muscle regeneration in the same old mice, findings further substantiated via genetic perturbations. At the levels of cellular mechanism, our results establish that the age-specific increase in TGF-β1 in the stem cell niches of aged hippocampus involves microglia and that such an increase is pro-inflammatory both in brain and muscle, as assayed by the elevated expression of β2 microglobulin (B2M), a component of MHC class I molecules.

Age-Associated Increase in BMP Signaling Inhibits Hippocampal Neurogenesis.

Hippocampal neurogenesis, the product of resident neural stem cell proliferation and differentiation, persists into adulthood but decreases with organismal aging, which may contribute to the age-related decline in cognitive function. The mechanisms that underlie this decrease in neurogenesis are not well understood, although evidence in general indicates that extrinsic changes in an aged stem cell niche can contribute to functional decline in old stem cells. Bone morphogenetic protein (BMP) family members are intercellular signaling proteins that regulate stem and progenitor cell quiescence, proliferation, and differentiation in various tissues and are likewise critical regulators of neurogenesis in young adults.

Mechanisms of action of hESC-secreted proteins that enhance human and mouse myogenesis.

Adult stem cells grow poorly in vitro compared to embryonic stem cells, and in vivo stem cell maintenance and proliferation by tissue niches progressively deteriorates with age. We previously reported that factors produced by human embryonic stem cells (hESCs) support a robust regenerative capacity for adult and old mouse muscle stem/progenitor cells. Here we extend these findings to human muscle progenitors and investigate underlying molecular mechanisms.

Let-7d microRNA affects mesenchymal phenotypic properties of lung fibroblasts.

MicroRNAs are small noncoding RNAs that inhibit protein expression. We have previously shown that the inhibition of the microRNA let-7d in epithelial cells caused changes consistent with epithelial-to-mesenchymal transition (EMT) both in vitro and in vivo. The aim of this study was to determine whether the introduction of let-7d into fibroblasts alters their mesenchymal properties.

hESC-secreted proteins can be enriched for multiple regenerative therapies by heparin-binding.

This work builds upon our findings that proteins secreted by hESCs exhibit pro-regenerative activity, and determines that hESC-conditioned medium robustly enhances the proliferation of both muscle and neural progenitor cells. Importantly, this work establishes that it is the proteins that bind heparin which are responsible for the pro-myogenic effects of hESC-conditioned medium, and indicates that this strategy is suitable for enriching the potentially therapeutic factors. Additionally, this work shows that hESC-secreted proteins act independently of the mitogen FGF-2, and suggests that FGF-2 is unlikely to be a pro-aging molecule in the physiological decline of old muscle repair.

Embryonic anti-aging niche.

Although functional organ stem cells persist in the old, tissue damage invariably overwhelms tissue repair, ultimately causing the demise of an organism. The poor performance of stem cells in an aged organ, such as skeletal muscle, is caused by the changes in regulatory pathways such as Notch, MAPK and TGF-β, where old differentiated tissue actually inhibits its own regeneration. This perspective analyzes the current literature on regulation of organ stem cells by their young versus old niches and suggests that determinants of healthy and prolonged life might be under a combinatorial control of cell cycle check point proteins and mitogens, which need to be tightly balanced in order to promote tissue regeneration without tumor formation.

Inhibition and role of let-7d in idiopathic pulmonary fibrosis.

Rationale: Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually lethal fibrotic lung disease characterized by profound changes in epithelial cell phenotype and fibroblast proliferation.

Objectives: To determine changes in expression and role of microRNAs in IPF.

Methods: RNA from 10 control and 10 IPF tissues was hybridized on Agilent microRNA microarrays and results were confirmed by quantitative real-time polymerase chain reaction and in situ hybridization.