Let’s talk about stem cells. You may have heard of stem cells in the context of advanced scientific research, or in terms of being able to do things that “regular” cells cannot do, or more details in that they have the potential to create organs in labs and be used in future transplants. All of these things are somewhat true, but let’s get a more concrete idea of what stem cells can do in today’s world through Dr. Emmanuelle Passagué’s research at Columbia University.
Our body is made up of trillions of cells, which are commonly called the building blocks of life. These cells differ from each other by the role that they play: your tongue cells, which help you taste food, are different from your skin cells, which help shield your body from and sense the environment. Within our body, we also have blood cells, which make up the red fluid that courses through your arteries, veins, capillaries, and even out of your body when you accidentally get a bad paper cut.
From what we can visually observe, we only see a blob of red, but within that blob, blood is actually made up of a few dozen different types of cells that carry oxygen and food around your body and make up the immune system that fights off infections and keeps you healthy. Each type of blood cell serves a part of one of these roles.
Cells don’t live forever. In fact, all the cells in our body are renewed once every seven years or so (Sison). During this renewal process, our older cells die and are removed from the body. But what fills in that gap?
Within nearly every organ of our body, we have stem cells. They are immature cells that reside within the organ, waiting for the signal to grow and mature. The signal comes when the older cells die. When stem cells receive this signal, the proteins within the cell alter the other types of protein produced by chemically defining which parts of the cell genome (DNA) is read.
In fact, DNA works kind of like a menu at Rainforest Cafe. When you are young, you go to the restaurant and order from the kids section. When you are older, you stop ordering from the kids section and start ordering from the adult section of the menu. At different ages, the menu is the same, but your age correlates to which section of the menu you order from. In cells, the DNA works like the menu because the DNA is the same in all cells in your body, but based on the cell type, different proteins are produced to fulfill their different functions. The production of these proteins are selective on a DNA level, just like how you order from different parts of the menu based on your age.
Stem cells remain in the body as stem cells because they haven’t received the signal to grow up yet. The body needs stem cells because we need to regenerate different parts of our body at different points in life. In the blood, the process of generating blood cells from stem cells is called hematopoiesis. Interestingly, all blood cells come from the same stem cell, which is called the multipotential hematopoietic stem cell (Jagannathan-Bogdan et al.).
Hematopoiesis is a highly regulated process—just imagine telling a group of 20 kindergarteners to do 20 different things at the same time and not copy their friend standing next to them; it takes a lot of monitoring and instructions. As we age, our body’s regulatory system becomes less capable of accurately regulating hematopoiesis. Thus, in older individuals, blood diseases such as leukemia become more common.
While it is very difficult to monitor what happens at a cellular level within the body, scientists have discovered a way to work around this barrier. Instead of putting probes directly into living animals, scientists can now take human stem cells, grow them on a petri dish in the lab, flood its environment with the same hematopoietic signals a stem cell would receive in its native environment in the body, and then watch the stem cells grow into mature blood cells.
Using this newly discovered procedure, Dr. Passegué at Columbia experimented with stem cells to study the effect of hematopoiesis on aging. What she and her lab found is that normal hematopoiesis is an intricate balancing act between self-renewal to grow more stem cells and maturation to meet the needs of the body’s blood system (Olson et al.). In addition, being able to grow stem cells on a dish allowed for in-depth analysis into how aging transforms our bone marrow—the locations where hematopoietic stem cells live and where a majority of the hematopoiesis process occurs—into a pro-leukemia environment (Verovskaya et al.).
In summary, the process of blood regeneration is a highly regulated and complex process. A lot of our body’s livelihood depends on hematopoiesis, but as we age, a lot can go wrong too. To understand exactly what can go wrong and how these mistakes happen, stem cells on a dish give scientists a new lens into the human body, helping us understand the biochemical processes behind aging and blood malignancies, and driving the development of new treatments to address these previously untreatable diseases.
E;, Olson OC;Kang YA;Passegué. "Normal Hematopoiesis Is a Balancing Act of Self-Renewal and Regeneration." Cold Spring Harbor Perspectives in Medicine. U.S. National Library of Medicine. Web. 07 Apr. 2021.
Jagannathan-Bogdan, Madhumita, and Leonard I Zon. "Hematopoiesis." Development (Cambridge, England). Company of Biologists, June 2013. Web. 07 Apr. 2021.
Sison, Gerardo. "Does Your Body Really Replace Itself Every 7 Years?" Discovery. 01 Aug. 2019. Web. 07 Apr. 2021.
Verovskaya, Evgenia V., Paul V. Dellorusso, and Emmanuelle Passegué. "Losing Sense of Self and Surroundings: Hematopoietic Stem Cell Aging and Leukemic Transformation." Trends in Molecular Medicine. Elsevier Current Trends, 17 May 2019. Web. 07 Apr. 2021.
Last Fact Checked on May 29th, 2021.