Fight Aging!

The primary scientific impulse is to accumulate data and extract knowledge from that data. Application of that knowledge to the production new technologies is a distant afterthought. So too in the life sciences specifically. When it comes to cellular senescence as a driving mechanism of aging, the primary focus of the research community is to employ modern omics tools to build as great a body of data as possible regarding the burden of cellular senescence in aged tissues. In particular this includes the ways in which the state of senescence differs between cell types, or even within the same cell type. Senescence appears to be much more a collection of distinct subtypes than initially suspected.

None of this changes the potential utility of early senotherapeutics, such as the low cost senolytic combination of dasatinib and quercetin that selectively pushes senescent cells into programmed cell death. Clearing even a third of lingering senescent cells from aged tissues produces dramatic benefits in aged mice, meaning a clear reversal of many different age-related diseases and dysfunctions. Yet relatively little effort has been made to rigorously assess this and other early senolytic drugs in humans. A few small academic clinical trials at a few doses have been undertaken when it comes to dasatinib and quercertin, too small a sample to say anything other than the results seem promising, and one company has made it as far as phase 2 trials for a poor choice of senolytic strategy before failing. One would think that the quality of the animal data demands a greater effort when it comes to dasatinib and quercetin.

Scientists Develop First Comprehensive Atlas of Human Cellular Senescence in Aging

A massive scientific initiative to decode how aging reshapes the human body reached a major milestone this month. The National Institutes of Health (NIH) Cellular Senescence Network (SenNet) published its first wave of discoveries. Together, they represent the first coordinated effort to map senescent cells - damaged or aged cells that stop dividing but refuse to die - at single-cell and spatial resolution. When cellular senescence occurs, these "zombie cells" accumulate over time. They secrete harmful chemicals that trigger inflammation and damage surrounding tissue. This process drives aging and fuels chronic diseases like arthritis, cancer, and Alzheimer's disease.

Charting human cellular senescence in aging and disease

Cellular senescence was first recognized in long-term in vitro cultures, where cells eventually ceased dividing yet remained metabolically active. Later studies revealed that senescence also occurs in vivo as a distinct cellular state induced by stress, damage, or other stimuli, resulting in permanent cell-cycle arrest alongside widespread alterations in intracellular and extracellular signaling, including the senescence-associated secretory phenotype (SASP). However, in the human body, we still know surprisingly little about which cell types undergo senescence, their abundance, their spatial distribution, and the impact on the microenvironment across different organs and tissues.

Without such a comprehensive "blueprint" of senescent cells in human tissues and organs, it is nearly impossible to address fundamental questions about their roles in maintaining tissue homeostasis, driving age-related physiological decline, or contributing to chronic diseases. Moreover, emerging evidence suggests that senescence is not a single, uniform program but a highly heterogeneous process. It may manifest differently depending on the initiating trigger, its duration, the tissue microenvironment, the cell type affected, and the individual's age or life stage. Yet, this diversity has been documented primarily in cell culture or animal models, with very limited characterization in human tissues.

The NIH SenNet consortium aims to build the first comprehensive human reference framework for heterogeneous senescent cell states, defined as "senotypes," providing the resources and tools needed to finally ask and answer the deep and meaningful questions about how senescent cells influence human aging and disease. The SenNet publication collection highlights some of the progress made in generating the human cellular senescence atlas during healthy aging of whole lymph nodes, lung parenchyma, prefrontal cortex tissues of the brain, and 14 other tissues; during disease in the liver and human chronic wounds from aged skin; and during the COVID-19 pandemic. Some of the manuscripts highlight the senolytic therapies identified and tested within the SenNet consortium. We envision that mapping senescent cells across human tissues will enable the development of precise diagnostics and senolytic therapies that selectively target harmful senescence while preserving its beneficial roles, transforming the management of aging and chronic diseases.