Counteracting age-related VEGF signaling insufficiency promotes healthy aging and extends life span

More VEGF, more life span and health span

Advanced aging is celebrated but its ill effects of deterioration at the cell, tissue, and organ levels are not. Grunewald et al. provide evidence for the vascular theory of aging, which reports that an age-related decrease of vascular function is a driver of organismal aging at large (see the Perspective by Augustin and Kipnis). Vascular endothelial growth factor (VEGF) signaling insufficiency underlies this vascular insufficiency in aged mice. A modest compensatory increase in circulatory VEGF was sufficient to preserve a young-like vascular homeostasis, alleviate multiple adverse age-related processes, and ameliorate a host of age-associated pathologies in mice.

Science, abc8479, this issue p. eabc8479; see also abj8674, p. 490

Structured Abstract

INTRODUCTION

All body cells rely on blood vessels (BVs) for the provision of oxygen and other blood-borne substances and, in certain settings, also for the provision of endothelial-derived paracrine factors. Like other organ systems, the vascular system undergoes aging, which leads to progressive functional deterioration. Given the centrality of BVs to organ homeostasis, it has been hypothesized that vascular aging is an upstream, founding factor in organismal aging, but experimental support for this proposition is limited. Vascular aging involves both large and small vessels, with the latter marked by capillary rarefaction, i.e., age-related failure to maintain adequate microvascular density (MVD). A key homeostatic mechanism preventing MVD reduction relies on the angiogenic activity of vascular endothelial growth factor (VEGF), which by virtue of its hypoxic inducibility, constantly acts to replenish lost vessels and match vascular supply to the tissue needs. The reason(s) that VEGF fails to do so during aging is unknown.

RATIONALE

Compromised vascular function is expected to perturb organ homeostasis in ways conducive for the development of age-related frailties and diseases. Accordingly, counteracting critical facets of vascular aging might be a useful approach for their alleviation. The presumption that insufficient vascular supply in aging is underlined by VEGF signaling insufficiency, primarily (but not exclusively) because of its indispensable role in preventing capillary loss, led us to investigate whether securing a young-like level of VEGF signaling might rectify capillary loss and its sequelae. On the premise that deteriorated vascular function is an upstream driver of multiorgan malfunctioning, it is envisioned that its rectification might confer comprehensive geroprotection.

RESULTS

Although VEGF production is not significantly reduced during mouse aging, longitudinal monitoring revealed that VEGF signaling was greatly reduced in multiple key organs. This was associated with increased production of soluble VEGFR1 (sVEGFR1) generated through an age-related shift in alternative splicing of VEGFR1 mRNA and its activity as a VEGF trap. A modest increase of circulatory VEGF using a transgenic VEGF gain-of-function system or adeno-associated virus (AAV)–assisted VEGF transduction maintained a more youthful level of VEGF signaling and provided protection from age-related capillary loss, compromised perfusion, and reduced tissue oxygenation. Aging hallmarks such as mitochondrial dysfunction, compromised metabolic flexibility, endothelial cell senescence, and inflammaging were alleviated in VEGF-treated mice. Conversely, VEGF loss of function by conditional induction of transgenic sFlt1 in endothelial cells accelerated the development of these adverse age-related phenotypes. VEGF-treated mice lived longer and had an extended health span, as reflected by reduced abdominal fat accumulation, reduced liver steatosis, reduced muscle loss (sarcopenia) associated with better preservation of muscle-generating force, reduced bone loss (osteoporosis), reduced kyphosis, and reduced burden of spontaneous tumors.

CONCLUSION

The study provides compelling evidence for the proposition that vascular aging is a hierarchically high driver of overall organismal aging. It places VEGF signaling insufficiency at center stage to multiorgan aging and suggests that its undoing might confer comprehensive geroprotection.

Centrality of VEGF and vascular alterations in age-related phenotypes.

Shown is a graphic representation of age-associated alterations in organ physiology and function (orange arrows) alleviated by VEGF gain of function (green arrows). Insert shows vascular casts of a native adult mouse myocardium before (control) and after sVEGFR1 induction, highlighting a failure to maintain adequate MVD in the presence of impaired VEGF signaling, a process that takes place naturally during aging. OCR, oxygen consumption rate; CH, carbohydrate; RQ, respiratory quotient; pVEGFR2: phosphorylated VEGFR2.

Abstract

Aging is an established risk factor for vascular diseases, but vascular aging itself may contribute to the progressive deterioration of organ function. Here, we show in aged mice that vascular endothelial growth factor (VEGF) signaling insufficiency, which is caused by increased production of decoy receptors, may drive physiological aging across multiple organ systems. Increasing VEGF signaling prevented age-associated capillary loss, improved organ perfusion and function, and extended life span. Healthier aging was evidenced by favorable metabolism and body composition and amelioration of aging-associated pathologies including hepatic steatosis, sarcopenia, osteoporosis, “inflammaging” (age-related multiorgan chronic inflammation), and increased tumor burden. These results indicate that VEGF signaling insufficiency affects organ aging in mice and suggest that modulating this pathway may result in increased mammalian life span and improved overall health.