Mind & body, in brief

Your cells are dying constantly. One review puts the daily total near 148 billion; another puts it at 200 to 300 billion. [1][2]

That is roughly a million cells a second, and you feel none of it. [2]

Dead cells are almost never found sitting in tissue. That absence is how researchers know the removal is fast. [1]

The eating has a name: efferocytosis. Macrophages, the immune system's cleaners, do most of it. [5][6]

Clearing debris this way is classed as housekeeping. It happens without any immune response being switched on. [51]

A dying cell flags itself first. It flips a fat molecule called phosphatidylserine to its outer surface as an eat-me sign. [1][5]

Healthy cells carry a don't-eat-me sign called CD47, which tells a macrophage to leave them alone. [5][7]

A cell that dies tidily makes no noise. The membrane holds, the contents stay in, and no alarm is raised. [1]

A cell that dies messily spills its contents. Those spilled parts are the alarm, and the inflammation follows from them. [27][28][49]

So the harm is not in the dying. It is in a body that sits there uncollected. [6][56]

In artery plaque, cells switch on the don't-eat-me sign and clearing stops. The dead pile up into the plaque's soft core. [7][8]

In lupus, clearing runs slow, and the leftover cell parts become the material the immune system attacks. [19][20]

Senescent cells make themselves hard to remove. They switch on survival pathways that let them dodge the immune clearing. [16][18]

Clearing also slows with age. It fell in old mice, and the same signal was raised in liver samples from older people. [11]

Ageing is described as a decline in the body's own ability to repair itself, and this is one of the ways. [52][17]

Why it matters. Watch whether restoring clearance works in people rather than mice. Nobody has yet shown that blocking the EP2 receptor lifts removal in aged human tissue. [11]

Stanford researchers found old mice had built up senescent neutrophils because tissue macrophages had stopped clearing them, traced to a molecule called prostaglandin E2. [11]

Why it matters. It moves the target from killing the cells to repairing the service that should remove them.

The two published senolytic trials in Alzheimer's, SToMP-AD and STAMINA, were open-label Phase 1 studies with five and twelve participants and no control group. [12]

Why it matters. The phrase zombie cells has travelled much further than the human data behind it.

In advanced artery plaque, cells display CD47, a don't-eat-me signal that blocks macrophages. Antibodies against CD47 restored clearing and shrank the dead core in mice. [7][8]

Why it matters. The plaque's dangerous soft centre is uncollected bodies, and the same death pathways drive calcium into vessel walls. [50]

Researchers reported five lupus patients carrying recessive mutations in PLD4, a gene whose product breaks down leftover single-stranded nucleic acid. The enzyme did not work. [22]

Why it matters. It is the closest thing here to a test of whether failed clearing alone can start the disease.

In lupus, dead-cell debris and neutrophil extracellular traps are cleared poorly. That leaves a steady supply of the body's own material for antibodies to attack. [19][21][25]

Why it matters. The self being attacked is largely rubbish that should have been taken away.

Ultraviolet light kills keratinocytes in the skin. The nucleic acids and danger signals they release switch on the interferon response that drives skin lupus. [23]

Why it matters. It explains why sun is a trigger, and it is a matter for a dermatologist, not a search engine.

Microglia and the complement system tag and remove synapses. In Alzheimer's that tagging goes wrong in some regions, while their clearing of the aggregates weakens. [29][31][32]

Why it matters. One cell is doing too much of one job and too little of the other, and viral infections can shift the balance too. [33]

In a mouse model of inflammation-driven Parkinson's, midbrain synapses were lost one day after the last injection. The dopamine neurons only died at day 14. [30]

Why it matters. The removal came first, which is an argument about cause rather than proof of it.

Many cancers block apoptosis using proteins such as survivin and XIAP. Researchers are now testing other death routes to get around that resistance. [34][35][55]

Why it matters. Where the body's problem is too little clearing, a tumour's is a cell that will not leave.

Caspase-3, best known for carrying out apoptosis, also pushes neighbouring cells to multiply. In tumours that turns an executioner into a growth signal. [36][37]

Why it matters. A dying cell is not a neutral event; it changes what its neighbours do next.

Apoptosis is only one route. Reviews now list necroptosis, pyroptosis, ferroptosis, cuproptosis and more. One counts nineteen named forms; another says over twenty. [26][27][28]

Why it matters. The count is unsettled, and each route leaves a different mess for the cleaners.

A review of 22 studies found intermittent fasting produced about 3% weight loss, below the 5% doctors call clinically meaningful. Its lead author called it no miracle solution. [38]

Why it matters. Autophagy, the clean-up inside one cell, is the mechanism most often named for fasting, and the human evidence stays inconsistent. [41][39]

A randomised study put 46 healthy adults on 850 calories a day for a week, comparing a low-protein and a high-protein version against a normal diet. [40]

Why it matters. That is the size of the human evidence sitting under a very large diet industry.

Mayo Clinic researchers found that RNA leaking out of the mitochondria of senescent cells triggers the inflammation driving a severe form of fatty liver disease. [13]

Why it matters. It names a specific route from one uncleared cell to organ damage.

Mayo used aptamers, short synthetic DNA strands that fold into shapes, sifted from over 100 trillion random sequences, to flag senescent mouse cells among healthy ones. [15][14]

Why it matters. Nobody can count what they cannot see, which is why the field argues about how many there are.

A model estimated that damage to neurons and heart muscle cuts a theoretical 1,759-year lifespan to 156 years. Liver, which replaces its cells, lasted millennia. [42]

Why it matters. Turnover is not decay. The tissues that turn over are the ones that last.

After oxygen loss at birth, necroptosis, an inflammatory kind of cell death, starts early and stays active for days. Cooling the baby suppresses it only in part. [43]

Why it matters. The standard treatment falls short against the death route that spills rather than the one that packages.

Researchers found that a cell pulling itself apart leaves an anchored patch of membrane behind. The patch carries the eat-me flag and marks the exact site for cleaners. [9]

Why it matters. Under a virus it can also hold virus particles, so the marker becomes a route of infection. [9]

In chronic wounds linked to diabetes, macrophage clearing of dead cells is impaired. Inflammation never resolves, and the wound does not close. [10][3]

Why it matters. The visible failure is a wound; the underlying failure is a collection service running behind.

In skeletal muscle, apoptosis removes damaged nuclei, necroptosis holds back excessive inflammation, and autophagy breaks down faulty proteins and worn-out parts. [44]

Why it matters. One tissue running three clean-up systems shows how much of staying well is removal work.

Cells run their own disposal network of chaperones, a protein shredder and the lysosome. Its collapse is now treated as a shared feature of several diseases. [46]

Why it matters. A Tau mutation that causes dementia was found to break the very route that would have cleared Tau. [47]

Watching disposal cell by cell in the zebrafish spinal cord, researchers found motor neurons degrade their own contents fastest, and losing a protein called TDP-43 made it worse. [48]

Why it matters. It offers a reason why one cell type dies first in motor neurone disease.

Macrophages that ate dying bone-building cells switched to burning sugar and poured out lactate, which altered inflammation and the making of bone-dissolving cells. [45]

Why it matters. Clearing is not neutral tidying; the act of eating changes the eater and its neighbourhood.

Researchers describe a molecule, Zharp1-163, that blocks both ferroptosis and necroptosis at once, aimed at inflammatory disease and sudden kidney injury. [54][53]

Why it matters. Where medicine once tried to stop cells dying, it is now trying to choose how they die.