The quality of stem and progenitor cells after long-term cryogenic storage

 by ALEXEY BERSENEV on JUNE 6, 2012 ·  in CLINICAL LAB,HEMATOPOIETIC The quality of stem cells after long-term cryogenic storage is an important question in the era of personalized cell banking and cell therapy. To date, we have some data for cord blood storage. Hal Broxmeyer’s group is carefully checking the quality of cord blood samples stored in liquid nitrogen since 1992. They publish reports every 3 years or so. The most recent report was from the last year:  We now report efficient recovery of functional HPCs up to 21-23.5 years, with more in depth studies on CB HSC engraftment in immune deficient mice, recovery of responsive T cells, generation of induced pluripotent stem (iPS) cells and detection of endothelial colony forming cells (ECFCs).  The quality of bone marrow-derived mesenchymal stromal cells after 25 years of cryopreservation was recently reported.  Despite regular reports on long-term storage of cord blood, we don’t have any data about quality of hematopoietic cells in stored bone marrow or mobilized blood cell products. A new study, published online 2 days ago, provides us valuable information about recovery of bone marrow- and mobilized blood-derived haematopoietic stem cell products after long-term storage.  … 31 separate bags of stem cell product (SCP) stored for 11–19 years (median 15 years) were assessed for total nucleated cell (TNC) count, colony forming unit-granulocyte/macrophage (CFU-GM), CD34+ cell count and cell viability. 

Few important points from the methodology of this study:  good number of samples analyzed (18 – bone marrow, 13 – mobilized blood); the same method of cryopreservation was used during last 20 years in this center; post-freeze/thaw test samples were used as controls. Results are quite interesting:  Recovery of TNC, CD34+ cell count and cell viability decreased with time (P=<0.01) but CFU-GM did not. This study shows that SCPs harvested from PB and BM do deteriorate with long-term storage. 

I was wondering why viability would drop?  The median recovery of viability was 58% and linear regression analysis demonstrated a significant decrease (P=0.01) in viability recovery with longer storage time of the product (Figure 2). The linear regression slope decreased at a rate of 0.282 per month, giving an estimated time to 50% recovery of viability of 195 months.  PS: Interestingly, this study was submitted for publication in 2010.