The Mannheim Cord Blood Project: Experience in Collection and Processing of the First 880 Banked Unrelated Cord Blood Transplants

Abstract

Background: Placental blood (= cord blood, CB) as a source of hematopoietic progenitor cells is an alternative to bone marrow or to peripheral blood stem cells for hematopoietic reconstitution after a myeloablative conditioning regime. With allogeneic CB transplants it is possible to cure patients with life-threatening malignant and nonmalignant diseases. The Mannheim Cord Blood Bank started the processing of unrelated cord blood transplants for routine clinical application in 1996. Materials and Methods: With a signed informed consent of the mothers more than 880 placental blood samples have now been collected by puncturing the umbilical cord of the placenta in situ. CB is only collected when there is evidence of neither maternal infection nor deformity of the child. After collection the CB is stored at room temperature until further processing. Units with a volume of >60 ml or >5 × 10⁸ total nucleated cells (NC) are processed as potential transplants. All specimens are evaluated for NC count, CD34-positive cells, erythroblasts and NC differentiation, HLA class I/II typing, bacterial contamination, AB0/Rh blood groups, and clonogenic capacity of hematopoietic progenitor cells. The maternal blood is screened for infectious diseases. To reduce the volume of the transplants, we centrifuged the blood and isolated the buffy coat by top/bottom separation. Finally, the transplant is frozen with 5% final concentration of dimethyl sulfoxide (DMSO) and stored in the vapor phase of liquid nitrogen. Results: We collected 65 ± 23 ml CB containing 6.6 ± 3.9 × 10⁸ NC (mean ± SD). 50% of all collected units had to be discarded for various reasons. The median recovery of NC, mononucleated cells (MNC) and CD34-positive cells achieved with the buffy coat preparation was 92.6%, 97.1% and 85.4%, respectively. Defining a threshold dose of 3.0 × 10⁷ NC/kg body weight (BW) for transplantation, 23% of the transplants were sufficient for the treatment of patients over 30 kg BW. Six months after delivery we asked all mothers for a further blood sample and for information about the development of the child. 49.1% of them responded within 8 weeks. Conclusion: We showed that in a very close collaboration with the obstetrician it is possible to establish a routine collection and processing procedure for cord blood transplants. Buffy coat separation by centrifugation is an effective method to reduce the volume of CB units. We found that a closed system technique is easy to perform and shows good recovery rates of nucleated cells.