LNSLNS The method we used to cryopreserve living cells is a procedure that is established worldwide, tried and tested; it meets the requirements of the pharmaceutical drug law and has been licensed by the supervisory authorities.

On the basis of our longstanding experiences in growing and culturing unrestricted, non-hematopoietic stem cells from umbilical cord blood (USSC), we do not agree that varying the freezing parameters would increase the generating frequency of the USSC from frozen material, because it turns out that fresh material contains non-hematopoietic stem cells only at a frequency of 1–11 colonies (1).

This is the actual problem, and it is the reason why generating USSC is successful only for about 30% of fresh cord blood. Changing the cryopreservation method would not change the cell loss and cannot easily be done owing to legal reasons.

In the long term, it would be advantageous to develop methods that further minimize the loss of hematopoietic, but also non-hematopoietic, cells—procedures that are superior to the current established protocols.
DOI: 10.3238/arztebl.2010.0293b

Prof. Dr. rer. nat. Gesine Kögler
Dr. rer. medic. Verena Reimann
Universitätsklinikum Düsseldorf
Institut für Transplantationsdiagnostik und Zelltherapeutika
Moorenstr. 5
40225 Düsseldorf, Germany
reimann@itz.uni-duesseldorf.de
koegler@itz.uni-duesseldorf.de

Conflict of interest statement
Dr Reimann and Professor Koegler work at the José Carreras Stammzellbank (the public umbilical cord blood bank at Düsseldorf University Medical Center). Professor Creutzig declares that no conflict of interest exists according to the guidelines of the International Committee of Medical Journal Editors.
1.
Kögler G, Trapp T, Critser P, Yoder M: Future of cord blood for non oncology uses. Bone Marrow Transplant 2009; 44: 683–97. MEDLINE
2.
Reimann V, Creuztig U, Kögler G: Stem cells derived from cord blood in transplantation and regenerative medicine [Stammzellen aus Nabelschnurblut in der Transplantations- und regenerativen Medizin]. Dtsch Arztebl Int 2009;106(50): 831–6. VOLLTEXT
1. Kögler G, Trapp T, Critser P, Yoder M: Future of cord blood for non oncology uses. Bone Marrow Transplant 2009; 44: 683–97. MEDLINE
2. Reimann V, Creuztig U, Kögler G: Stem cells derived from cord blood in transplantation and regenerative medicine [Stammzellen aus Nabelschnurblut in der Transplantations- und regenerativen Medizin]. Dtsch Arztebl Int 2009;106(50): 831–6. VOLLTEXT