Novel cryoprotectant significantly improves the post-thaw recovery and quality of HSC from CB

BackgroundHematopoietic stem cells (HSC) have traditionally been frozen using the cryoprotectant DMSO in dextran-40, saline or albumin. However, the process of freezing and thawing results in loss of HSC numbers and/or function.MethodsThis study investigated the use of CryoStor™ for the freezing of HSC from cord blood (CB). CB donations (n = 30) were collected under an Institutional Ethics Committee-approved protocol, volume reduced and frozen using three different methods of cryoprotection. Aliquots were frozen with either 10% DMSO in dextran-40, 10% DMSO in CryoStor™ or 5% DMSO in CryoStor™. Prior to freezing samples were separated for nucleated cell (NC) and CD34+ counts and assessment of CD34+ viability. Aliquots were frozen and kept in vapor phase nitrogen for a minimum of 72 h. Vials were rapidly thawed at 37°C and tested for NC and CD34+ counts and CD34+ viability and colony-forming unit (CFU) assay.ResultsCells frozen with CryoStor™ in 10% DMSO had significantly improved NC (P < 0.001), CD34+ recovery, viable CD34+ (P < 0.001) and CFU numbers (P < 0.001) compared with dextran in 10% DMSO. CryoStor™ in 5% DMSO resulted in significantly improved NC (P < 0.001) and CFU (P < 0.001).DiscussionThese results suggest that improved HSC recovery, viability and functionality can be obtained using CryoStor™ with 10% DMSO and that similar if not better numbers can be obtained with 5% DMSO compared with dextran-40 with 10% DMSO.