SCIENCE OF STEM CELLS
Stem Cell Basics
What are stem cells?
>> DR. MARC PENN: Stem cells are actually defined very simply. They’re a cell that can divide and make two daughter cells, and those daughter cells can differentiate into more than one kind of cell in the body.
What are adult stem cells?
>> DR. PENN: Adult stem cells come from an adult, which is any time after birth. So, that includes umbilical cord stem cells, bone marrow-derived stem cells, fat-derived stem cells, whereas non-adult stem cells are embryonic stem cells. They come from before birth.
The main difference between embryonic or pre-adult stem cells and adult stem cells is that adult stem cells have a limited differentiation capacity. They can’t become everything, whereas embryonic stem cells, by definition, are totipotent, which means they can become anything in the body.
What do we currently know about how stem cells work?
>> DR. PENN: Adult stem cells work through four mechanisms. They are anti-inflammatory. They decrease inflammation at the site where they’re delivered. They also block cell death. So, if a tissue’s been injured and cells are dying and you get them adult stem cells as happens in heart attack and stroke, you can actually prevent those cells from dying.
They also activate what we call the endogenous stem cell system. Every organ in our body has its own stem cells. By delivering adult stem cells to that organ, you activate those cells. Those cells can then differentiate and replace dead or dying cells, and they can also release molecules that improve tissue function, and finally, adult stem cells are anti-fibrotic.
They either prevent scarring or they remodel scarring. So, there’s less scarring present after the tissue has healed. Adult stem cells do this through the release of proteins and what we call exosomes. They release them into the tissue where they’ve been delivered, and that really activates these four mechanisms that they work through.