Transplanted Stem Cells Transplanted stem cells, such as those from bone marrow, come from your own body and are placed where they are needed to treat a condition. An example would be transplanting stem cells from your bone marrow to your knee to treat an injury there. Many patients think this is better because it comes from your own body. The reality is that this actually poses many limitations due to the loss of stem cells over the course of your life (see previous question for details) meaning your own stem cell concentrations will be lower than those you could get from an outside donor. Donor Stem Cells Donor stem cells come from an outside source. It is important to verify that the stem cells come from an ethical and reliable donor, such as bone marrow or umbilical cord blood, and contain mesenchymal stem cells (MSCs). MSCs have the ability to differentiate, meaning they can take on the role of many different cell functions. A body does not “reject” stem cells the same way it could reject an organ that comes from an outside donor and does not match due to the nature of stem cells and particularly the ability of MSCs to differentiate. Reputable clinics utilize only stem cells ethically extracted from umbilical cords donated at birth. Umbilical cord blood stem cells are a heterogeneous mixture of stem cells including MSCs. Injections include infusions of up to 30 million stem cells in one session.