The Future of Medicine: Regenerative Medicine (Part I)
Regenerative medicine is an exciting and quickly emerging field. By harnessing the bodies own regenerative capabilities, regenerative medicine scientists seek to understand how we treat injuries and diseases from broken bones to neurodegenerative diseases.
Conveniently, humans are already equipped with some of their own regenerative capabilities. For example, the liver is able to regrow to its original size if part of has been lost to injury or disease, our skin regenerates approximately every 27 days and red blood cells are renewed every 100 days or so. Impressive right?
However, not all cells, tissues and organs can regenerate- that’s where regenerative medicine scientists come in. Based on what we know and what we’re trying to understand, scientists believe that they could one day enable all cells, tissues and organs to regenerate. The first step in this journey involves understanding the mechanisms, behaviours and functions of cells that facilitate their own regeneration. Armed with this information, scientists are working to uncover how best to bestow regenerative abilities to all cells, tissues and organs in the human body.
“By harnessing the bodies own regenerative capabilities, regenerative medicine scientists seek to understand how we treat injuries and diseases from broken bones to neurodegenerative diseases.”
What are stem cells?
Stem cells are at the heart of regenerative medicine and to understand the capabilities of regenerative medicine, an appreciation of these wondrous cells is important. Stem cells are a very special type of cell, and are dubbed the ‘building blocks of organisms’ – and for good reason! They exist in our bodies and every other multicellular organism on the planet. For those who love a definition, the classical definition of a stem cell requires that it possesses two fundamental properties: self-renewal (the ability to divide over and over again without changing its stem cell identity) and potency (the ability to differentiate/transform into specialised cell types). These key features are what makes stem cells unique and unlike any other cell in the body.
In humans, stem cells are most active during early development, but they remain present and active in some regions of the body when we become adults. The role of stem cells is to create different types of cells, which they achieve by dividing and differentiating. When a stem cell divides, each new cell will either remain a stem cell or turn into one of the many different cells found in our bodies (e.g. muscle, nerve, and red blood cells). During development, stem cells give rise to all of our limbs and organs. Unlike early development, in an adult, stem cells are designed for growth and repair. A part of regenerative medicine research is understanding how populations of stem cells change during the transition from development to adulthood.
What are the different types of stem cells?
Currently, there are three different sources of stem cells. Embryonic stem cells originate from blastocysts, which are embryos that are five to seven days old. They are pluripotent, which means that can differentiate into any type of cell that is needed. In fact, embryonic stem cells can develop into more than 300 cell types that we see in the adult body! This makes them the most powerful type of stem cell.
Adult stem cells are more restricted – they can only turn into select cell types. These cells can renew themselves or change into a specialised cell type to maintain or repair tissue. Given this characteristic, they are categorised as multipotent. Adult stem cells are generally found in specific tissue or organs, like bone, skin, liver, and the lining of the stomach and gut. While these type of stem cells are not as powerful as embryonic stem cells, they are still somewhat useful. In fact, adult stem cells are frequently used in several treatments, for example, bone marrow transplantation to treat leukaemia and other blood cancers.
The third source of stem cells is induced pluripotent stem cells. These are a relatively new type of stem cell that can be made in the laboratory, thanks to the accumulated knowledge we have gained about stem cells. Scientists effectively extract a cell from the body and genetically reprogram it back into a stem cell with qualities similar to those of embryonic stem cells (i.e. pluripotent). Induced pluripotent stem cells are important and versatile tools for scientists to understand the regulatory mechanisms, the functions and the potential of stem cells. Currently, these cells are only used in research as the genetic programming technology is not quite advanced enough to be used for treating diseases and conditions in humans just yet. However, there are hopes that one day these cells may form part of a cure.
“Stem cells are an important tool to help us understand regeneration, regenerative medicine encompasses a much broader field of study that has the potential to give rise to new and different treatments.”
While scientists may not know everything about stem cells, over time, they have identified essential functions and characteristics of stem cells. And while stem cells are an important tool to help us understand regeneration, regenerative medicine encompasses a much broader field of study that has the potential to give rise to new and different treatments.