Organs Are A Mix Of New And Old Cells, New Study Suggests


Much like how you are growing older and aging, your organs are too. But, with the new scientific and medical findings, it has been witnessed that the organs in our body are often a mix of old as well as new cells. So, when you are trying to assess how old your organs are, a new study can definitely pave way for that.

The study (R), conducted by the researchers from the Salk Institute has found a new breakthrough in judging the age of the organs in the body. While the researchers did think that neurons and the heart cells were the oldest, the researchers have found that it is indeed the brain, liver and the pancreas which consists of the oldest cells as found in the study conducted in the mice.

This specific study explains everything there is to know about “age mosaicism” and the findings of this study were published on June 06, 2019 in the journal, Cell Metabolism.

Martin Hetzer, Salk Vice President, Chief Science Officer who is also the senior author of the study and a professor stated that the researchers were surprised to find that some of the tissues in the organs in organism are as old as the organism that they reside in. What this suggests is the fact that cellular complexity is way more than what the scientists previously thought. Additionally, the same also has intriguing implications in the process of aging of the organs like the brain, heart and even the pancreas.

Majority of the neurons don’t divide during our adulthood which results in the long lifespan followed by the age related decline as well. Alternatively, because of the technical limitations, the lifespan of the cells outside of the brain was quite difficult to determine.

Rafael Arrojo e Drigo, Salk staff scientist and the first author of the study stated that there has always been a lingering question in the minds of the scientists on how old the organs are. While they thought that the neurons will have the oldest tissues and cells and the rest of the organs comprising of regeneration of cells through the year, the same was the primary reason why they set out to find traces of it with factual evidence.

Owing to the fact that they knew that the neurons don’t divide throughout the lifespan, they used that as a standard and termed it as the “age baseline” to compare the non-dividing cells in the body.

In order for further analysis, the team of researchers combined the electron isotope labeling along with a hybrid imaging method to help visualize and quantify cell and the protein age as well as the turnover in the brain cells along with that of the pancreas, liver in both the young as well as old rodents.

In order to validate the process that they were opting for, they determined the age of the neurons and to their knowing, they found that it was as the age of the organism itself. But, they also found that the endothelial cells in the lining of the blood vessels which does suggest that some of the non-neuronal cells do not divide or replicate through the lifespan.


Additionally, the pancreas even showcased a varying aging of the cells in them. A small portion of cells in the pancreas, known as the Islets of Langerhans, were found to have a combination of both young as well as old cells.

Some of the beta cells in the pancreas did replicate through the lifespan and were thus relatively new while a few of them didn’t replicate and were long lived much like that of the neurons.

The delta cells were found to have not divided at all, thus making pancreas an ideal model for age mosaicism which describes a population of identical cells distinguished by their life spans.


The prior studies have suggested well and through that liver does have the capacity to regenerate through the years, thus the researchers were expecting the organ to predominantly have new cells and tissues.

But, with the study conducted, the researchers found that majority of the cells in the liver were as old as the organism itself. It was the cells lining around the blood vessels as well as the stellate like cells were the ones which had a much shortlived cells in them.

All of these new findings do suggest better scopes of regenerative studies for this organ in the coming days.

Molecular levels

When it came down to studying it under the molecular scale, it was found that majority of the selection of the long lived cells did contain several kinds of protein complexes that displayed the prospect of age mosaicism. Be it the primary cilia of the beta cells in the pancreas or even the neurons in different regions.

In comparison and contrast, the liver cells didn’t necessary consist of any form of long lived proteins in them.

Mark Ellisman, Distinguished Professor of Neurosciences at UC San Diego’s School of Medicine, who is also the co-leader of the study stated that it is all because of the new technologies that have made it a lot easy for us to assess the age of the cells as well as their supramolecular complexes even better. This helps in providing with a wide spectrum of knowledge concerning studying of the cells, tissues as well as the organs in both the normal as well as the diseased states.

Throwing some more clarifications to this, Hetzer said that determination of the age of cells as well as the subcellular structures in the adult organisms is going to create a breakthrough and provide insights into cell maintenance as well as the repair mechanisms involved. The ultimate goal of the researchers is to prevent the age related decline of the varying organs that have limited cell renewal.

Following finding these with the aging of the cells in the organs, the next step that they are thinking of is to find the difference in the lifespans of the nucleic acids and lipids. Furthermore, they also want to see how the age mosaicism relates to varying chronic diseases like that of type-2 diabetes.