Short YouTube clip from Joy Kong, MD warning about risks of over-culturing stem cells in incubators. Key claims: extended in‑vitro expansion can cause genetic changes, reduce the proportion of true (undifferentiated) stem cells due to asymmetric division and differentiation, degrade DNA and surface marker expression, and increase the risk of immune rejection when transplanted into another person.
Using cells that have been over cultured. When you grow the cells in a incubator to a huge number and this is commonly done overseas. The problem is the more you incubate and let the cells grow, the more genetic changes can happen. Also the less stem cells there are. Because stem cells divide, they tend to divide into a identical copy of itself and another copy that's actually stem cell slightly differentiated. So these are no longer the stem cell that we were speaking of. We are decreasing the stem cell population when we start to grow these cells in the culture. Also genetically, DNA wise they are degrading. They may express surface markers that mark them as foreign. So when you put it into another person's body, that may cause rejection. So not only the cells have degraded, in a sense they've lost a lot of the stem cell charact have a big batch of a lot of cells, but only small portion will be stem cells.
