Why bank iPSCs
instead of other stem cells?
The cord blood is one of the major sources for cyro-preservation banking. These cord blood cells are rich in blood-making stem cells, known as hematopoietic stem cells (HSCs). Although HSCs are stem cells, they can only give rise to cells of blood lineage. Furthermore, HSCs have limited proliferation capability outside the body and thus cannot be expanded indefinitely.
Another type of adult stem cell commonly used in cell therapies is mesenchymal stem cells (MSCs). MSCs are also multipotent and only give rise to certain cells such as bone, muscles and fat. Typically, MSCs are derived from fat tissue or bone marrow of adults. Like cord blood- or bone marrow-derived HSCs, MSCs have limited proliferation capability outside the body. However, unlike cord blood-derived HSCs, MSCs may already carry background genetic mutations, which make them even less ideal for cryo-preservation.
Besides the multipotent HSCs and MSCs, there is another type of stem cell called pluripotent stem cells (PSCs). Different from HSCs and MSCs, PSCs have self-renewal capability and thus can be expanded indefinitely. Moreover, PSCs are pluripotent, meaning that they can give rise to all cell types of the body. A classical source of PSCs is called embryonic stem cells (ESCs), which are derived from a fertilized egg. ESCs open many possibilities for regenerative medicine. However, ethical concerns are many as establishing ESCs causes destruction of fertilized eggs.
In 2007, Professor Yamanaka and his team of scientists discovered that human dermal fibroblast could be converted into PSCs through the delivery of four genes using virus. Such pluripotent stem cells are “induced” from mature cell and thus named induced pluripotent stem cells (iPSCs). Functionally, iPSCs are similar to ESCs. They are capable of self-renewing and differentiating into any cell types of the body. Yet, as the starting materials for generating iPSCs are sourced from consented individuals, there is no ethical issue involved.
In Singapore, researchers of CytoMed Therapeutics, have generated “off-the-shelf” cancer-killing cells from iPSCs for cancer immunotherapy (Figure 1). All these efforts indicate that the clinical potential of personalised iPSCs may soon outweigh the traditionally cryopreserved HSCs and MSCs. Table 1 summaries the therapeutic potential of iPSCs and other types of stem cells.
Such personalized cryopreserved iPSCs are recommendable to everyone including individuals who have banked their own cord blood when they were born. The cryopreserved iPSCs may provide much more than the cryopreserved cord blood. For individuals who have missed the opportunity to bank their own cord blood at birth, cryopreservation of all-encompassing iPSCs provides an even better chance for a personalised storage of your own stem cells that may do so much more than cord blood.