Every single cell in your body is happy, but some lucky ones may just be the happiest, given their lifespans!
The human body replaces its cells every 7 to 10 years, but this is just an average—from mere hours to days after the body dies, each group of cells has its own lifespan.
If you’ve ever wondered which cells live the longest in the human body, you’re in the right place!
In search of the answer ourselves, here’s what we came across!
The Longest-Living Cell
Each cell and tissue has its own lifespan, primarily influenced by the amount of work it does.
For example, the cells that form the human skin—epidermal cells—regenerate every 3-4 weeks, on average, as they’re the most exposed to various elements and the ensuing wear and tear; neutrophil cells last 2-5 days and gut cells last five!
Red-blood cells, constantly circulating around your body, live for up to four months, whereas adult liver cells get replaced every 200 to 300 days.
Some cells have longer lifespans, such as intestinal cells. These cells can last up to 16 years, as can rib-muscle cells.
Here’s the lifespan of a few major cell groups in the body:
- Neurons: Neurons are believed to live for decades and do not divide (non-mitotic). Memory B-cells and T-cells have been shown to provide long-lasting immunity against antigen exposure.
- Oocytes: These cells are present from the time of birth in the human body and mature as the person hits puberty. They last for a few decades after that, but not as many decades as neurons.
- Eye Lens Cells: Cells in the lens of the eyes can last a lifetime.
- Heart Muscle Cells: These cells can last between 40 and 50 years.
- Fat Cells: Fat cells last eight years (yep, you read that right!).
Some cells, such as mature neutrophils, stay on in their mature forms within the bone marrow, before they start circulating, and once done, may exit their circulation route and enter storehouses such as the lungs.
So though their actual lifespan, counted as per their circulation time, is eight days, they live much longer.
Earlier, it was widely believed in the world of science that since they lived as long as the bodies they were housed in, neurons and heart cells were the longest-living cells in the human body.
However, further research led to the discovery that brain cells, especially from the cortex, lived up to the same age as their human hosts.
Scientists believe that this could be due to the need for these cells to be wired in an extremely stable manner, with even the smallest change possibly causing disruptions in major brain functions.
Further studies showed that pancreatic and liver cells also could live as long as the organism itself. The cells in these organs didn’t regenerate or get replaced throughout the organism’s life and endured from the time of birth all the way until death did them part!
So does that mean that these three groups of cells are the longest living in the human body?
Well, yes and no.
Meet stem cells!
Stem Cells: The Methuselah?
It turns out that stem cells are the longest-living cells in the human body and can even stay alive beyond its death!
Stem cells are specialized cells in the human body that develop into various other types of cells, called daughter cells, which range from brain cells to muscle cells.
Stem cells are akin to raw material, serving as the base ingredient from which other cells and specialized functions develop. This makes them extremely valuable, with many scientists and organizations trying to harness their regenerative properties and longevity for treatments and therapies.
The fact that these cells are rare, difficult to extract from samples, and cannot be easily differentiated from other cells makes stem cell research hard. Additionally, most samples only contain small numbers of these cells.
Getting back to the main question at hand, many types of stem cells, once formed through embryogenesis, continue to function in their original forms until death.
Apart from the brain and many muscles, stem cells are also found in self-renewing tissues, such as the skin, blood, gut epithelium, and bone marrow.
The life of the stem cells in these different parts depends on the work these cells do in their respective parts, which is why some stem cells live shorter than others.
Therefore, stem cells are the cells that live longest in the human body.
In fact, recent research shows that stem cells remain alive even after death, for up to an impressive 17 days—the cells lived for two days inside the cadaver despite the lack of nutrients and oxygen that cells generally need to survive, and for 15 days, under laboratory conditions, after they were removed from the cadaver.
Which Cells Live The Longest? The Bottom Line
And there we have it—the answer to which cells live the longest!
Stem cells are a hardy lot, responsible for a lot of good stuff that happens in your body. As mentioned, many scientists are trying to replicate the regenerative qualities of stem cells in order to find the secret to prolonging human life.
Recent studies also show that brain cells, like stem cells, may be able to survive outside the human body after its death.
However, this research is still nascent, and for now, stem cells remain the clear winner!