We collect 60mL. There are normally about 10-15M nucleated cells recovered per mL of bone marrow. Stem cell counts are typically 0.01% of this (MSCs are about 1000/mL). We bank the cells in multiple chambers (3 larger ones, 5-6 smaller ones) so that you can draw them up multiple times. As they can be greatly expanded, it is our intent that the cells be grown to large numbers and then those portions cryopreserved. As an experiment, I have done this with my mesenchymal stem cells, and now have more outside of me than inside of me. If properly managed, a vast pool of cells could be created to draw upon. It's worth noting that we have gotten much better at expanding these cells over the last decade (decreasing negative effects of expansion). I expect that trend to continue.
If expanded over many passages in culture, the cells can degrade, much like they do due to age. For this reason, it is advantageous to start with sufficient numbers (thousands), rather than a few cells. However, as mentioned, we have improved culture conditions greatly in the last decade (ex. growing mesenchymal stem cells in a 3D matrix rather than flat on plates), which has extended our ability to generate more cells.
