Youth-Associated Protein TIMP2 Rejuvenates Brain Immune Cells in Aged Mice
核心洞察
Researchers at Mount Sinai found that the youth-associated protein TIMP2 supports healthy microglial function in the brain.
Removing TIMP2 caused microglia to develop aging- and neurodegeneration-associated features, including impaired debris clearance and cellular senescence signatures.
Restoring TIMP2 in the blood of aged mice shifted microglia away from pro-inflammatory states and improved their ability to clear debris.
Researchers at The Icahn School of Medicine at Mount Sinai (搜索) have identified a role for TIMP2, a protein associated with youth, in helping microglia—the brain's resident immune cells—maintain healthier function. Published August 12 in Nature Communications, the study found that removing TIMP2 caused microglia to develop several characteristics linked to aging and neurodegeneration, while restoring TIMP2 in the blood of aged mice improved the cells' ability to remove debris and reduced molecular markers associated with inflammation and other maladaptive states.
Aging is the strongest known risk factor for Alzheimer's disease (搜索) and other neurodegenerative disorders, yet the biological changes that make older brains more susceptible to disease remain incompletely understood. Microglia help protect brain health by clearing cellular debris, supporting neural circuits, and responding to injury. As they age, however, these cells can become less efficient and shift into states that may promote inflammation and impaired brain function.
"TIMP2 facilitates healthy function for the brain's immune cells," said Joseph M. Castellano, PhD, Associate Professor of Neuroscience at the Ronald M. Loeb Center for Alzheimer's Disease (搜索) and The Friedman Brain Institute at The Icahn School of Medicine at Mount Sinai (搜索), and corresponding author of the study. "By supporting the ability of microglia to clear debris and limit maladaptive responses, TIMP2 may help restore aspects of microglial function that become compromised with age. Since our previous work identified TIMP2 as a regulator of synaptic plasticity through the extracellular matrix, these findings suggest that this factor sits at the intersection of several processes that are critical for normal brain function."
Loss of TIMP2 Drives Aging-Like Microglial Changes
To investigate how TIMP2 affects microglia in healthy and aging brains, the researchers—including first author Brittany Hemmer, PhD, a graduate student in the Castellano laboratory at the time—studied several mouse models. Some mice lacked TIMP2 throughout the body, while others had the protein selectively removed from either microglia or neurons.
The team analyzed gene activity using single-nucleus RNA sequencing of brain tissue, combined with advanced imaging, functional assays, and in vivo microdialysis, a technique used to sample molecules in the living brain.
When TIMP2 was removed, microglia developed features commonly linked to aging and brain injury. The cells showed changes in activation markers, became less capable of clearing cellular debris, and displayed molecular signatures associated with cellular senescence. In vivo microdialysis also revealed higher levels of inflammatory and stress-related proteins in the extracellular environment of the brain when TIMP2 was absent.
Restoring TIMP2 Improves Debris Clearance in Aged Mice
The researchers next examined whether adding TIMP2 could counter some of these age-related changes. After administering systemic injections of TIMP2 to aged mice, they found that microglia shifted away from pro-inflammatory states and became better at clearing debris.
The findings suggest that TIMP2 helps regulate how microglia respond to challenges in the brain, supporting functions that preserve a healthy neural environment while limiting potentially damaging responses. They also point to a possible molecular connection between systemic factors associated with youth and the function of innate immune cells in the aging brain.
Human Translation Remains Unclear
"While additional studies are needed, this work provides new insight into how youth-associated factors influence pathways involved in brain aging and age-related neurological disorders that may ultimately inform therapeutic strategies," Dr. Castellano added.
Because the experiments were conducted in mice, further research will be needed to determine whether the same findings apply to humans. Researchers must also establish whether TIMP2 or the pathways it controls could eventually be targeted to alter age-related changes in the brain.
The work was supported by the National Institute on Aging (R01AG061382, RF1AG072300, 1F31AG079604-01A1, T32AG049688, R01AG061382-02S1) and the Cure Alzheimer's Fund.