Understanding QA results

We check the quality of our cryopreserved cord blood and tissue samples twice a year to determine the quality of stem cells inside the cord blood.  Since a stem cell looks like any other mono-nuclear cells (MNC), one cannot identify the stem cells simply by looking under a microscope.  Here are some ways to check:

Using a biochemical stain, it is possible to enumerate the cells that are positive for CD34, a protein marker found on the surface of hematopoietic stem cells.  However, CD34+ counts are very basic and it is only a simple measure of active stem cells within the stored cord blood.  In fact, only 1-2% of the MNCs that are CD34+, but clinical engraftment need almost all the stored cord blood unit.  In summary, this means the CD34+ result alone is not representative of the functionality of the cord blood unit used in future clinical therapy.

This is an important and most commonly reported type of viable cell count relative to the potency of a cord blood collection unit for storage after processing.  TNC is highly reproducible among labs.  It is therefore used accurately throughout the blood banking community and the TNC report is what a Medical Centre will observe and check prior to any Stem Cell Therapies.

This is currently the best measure to indicate whether the long-term cryopreserved stem cells are “viable”.  In a CFU assay, a small portion of sample is analyzed under controlled conditions within 10-14 days to see whether the observed stem cells differentiate and proliferate to form colonies, which are then counted.  It is a time-consuming test procedure, but this is the type of test that we are committed to do regularly at CRYOLIFE to ensure your precious cryopreserved Cord Blood samples are well-taken care of and are still alive and viable for future stem cell therapeutic use.

Reference: https://parentsguidecordblood.org/en/faqs/what-are-tnc-mnc-cd34-and-cfu-and-why-should-i-care