Abstract
Background aims. We investigated two different plastic freezing bags, namely the most recently U.S. Food and Drug Administration (FDA)-approved CryoMACS® freezing bag (200-074-402) from Miltenyi Biotec and the familiar Cryocyte® freezing bag (R4R9955) from (Baxter Healthcare, Deerfield, IL, United States) for the cryogenic storage of human hematopoietic progenitor cells (HPC). Methods. The study material consisted of 12 frozen HPC pairs (= 24 transplant units) that were no longer needed for autologous treatment of patients. After thawing, one unit of a pair was transferred into the Miltenyi (M) bag; the other unit remained in the original Baxter (B) bag. After refreezing both units, all units were stored again under cryogenic conditions either partially immersed in liquid nitrogen (n = 22) or in the vapor phase over liquid nitrogen, n = 2, <−170°) before thawing. Results. The correlation coefficients (r) between the results obtained from the two bag types were high for white blood cells (WBC) content (r = 0.98), mononuclear cells (MNC) (r = 0.97), lymphocytes (r = 0.98), monocytes (r = 0.96), membrane integrity (r = 0.93), concentration of ‘free’ hemoglobin (r = 0.97) and hemolysis rate (r = 0.95). With regard to clonogenicity, there were no significant differences (Student's paired t-test) for the three parameters investigated [i.e. total number of colonies, including the numbers of burst-forming units–erythroid (BFU-E) and colony-forming units–granulocyte-macrophage (CFU-GM) colonies, respectively). Conclusions. The CryoMACS freezing bag 200-074-402 is bioequivalent to the Cryocyte freezing container R4R9955. An advantageous feature of the CryoMACS is that its double-sterile wrapping provides additional safety regarding potential cross-contamination during cryogenic storage.
Acknowledgments
The authors wish to gratefully acknowledge the outstanding experimental work of Edeltraut Merle, Marie-Luise Reckhaus, Cathrin Schwarz and Kirsten Holzhüter throughout this study.
Declaration of interest: The study was supported by Miltenyi Biotec, Bergisch Gladbach, Germany. The authors alone are responsible for the conception and conduction of the investigations. This holds for the content and writing of the paper as well.