Why has the definition of stem cell gone off in all directions?
It’s the vagaries of cell culture. Because scientists typically study stem cells in a culture dish, they describe certain characteristics that may or may not relate back to what they do in the body. For example? Well, two things come to mind. A lot of people say that a stem cell is undifferentiated. But that may be a misnomer. It may be that a fully differentiated cell, under the proper conditions, can revert back and become a precursor cell or maybe even a more primitive cell like a stem cell. As long as a cell has an intact nucleus, nothing is really impossible. Secondly, some say a stem cell has the ability to replicate almost endlessly. But that isn’t necessarily the case either. Even the best characterized stem cell – the hematopoietic stem cell – is not immortal. Each hematopoietic stem cell can only repopulate blood cells a certain number of times before it becomes exhausted. How does this “stemness” translate to the periodontium? Let’s start with the periodontal ligament. We kn
