CRYOPRESERVATION, STORAGE AND SHIPMENT

Hematopoietic stem cells (HSC) isolated from the peripheral blood (PBSC) are frozen and stored using the same techniques previously developed for bone marrow hematopoietic cells.1 The general parameters include cryopreservation in dimethylsulfoxide (DMSO) and a source of plasma protein with or without hydroxyethylstarch (HES),2,3 cooling at 1 to 3o C/minute, and storage at-80o C or colder. The major difference for the cryobiologist is the large number of cells collected during apheresis, averaging 4.3x1010 in a series of patients at this center, that complicates cryopreservation of PBSC. Cryopreservation of cells at the concentrations frequently used for bone marrow could result in volumes in excess of 400 ml for each collection. Infusion-related toxicities appear to be related to the amount of DMSO infused.4 The maximal tolerated dose of dimethylsulfoxide is not known for humans. The LD50 of DMSO for dogs has been reported to be 2.5 gm per kilogram body weight, 5 or about 22 ml/kg of a 10% DMSO solution. We limit the amount of cryopreserved cells to be infused to 10ml/kg/day for this reason. Patients with larger volumes will receive the cells over more than 1 day. To minimize the volume infused, we concentrate the cells before cryopreservation. In one series of patients, the average cell concentration of cryopreserved PBSC was 5.59x108 nucleated cells per ml.6 High concentrations of red cells and platelets were also frozen. We found no detrimental effect of cryopreservation at these high cel