LONG-TERM STORAGE OF HUMAN FETAL HEMATOPOIETIC PROGENITOR CELLS AND THEIR SUBSEQUENT RECONSTITUTION - IMPLICATIONS FOR IN-UTERO TRANSPLANTATION

Haematopoietic progenitor cells were isolated from human fetal liver, obtained between 6 and 15 weeks gestation. After preparation of a sing le cell suspension, the cells were stored using a stepwise freezing pr otocol; taking the cells from room temperature through -70 degrees C t o liquid nitrogen. Viability (trypan blue exclusion), morphology (Leis hman stain), identification of cell type (flow cytometry) and growth c haracteristics in semisolid culture medium were assessed using the fre sh cell suspension. We were able to confirm that the predominant cells in human fetal liver up to about 15 weeks gestation are those of the erythroid lineage. It was established that viability in excess of 75% was required to ensure adequate growth in culture after frozen storage and it was deemed important to ensure morphological integrity of the cell preparations. The colonies formed in culture were observed to be producing haemoglobin between 7 and 9 days after initial seeding. We h ave determined that cells can be stored in liquid nitrogen for up to 2 years without loss of (1) viability, (2) morphological features and ( 3) ability to form colonies and produce haemoglobin in culture. These findings offer encouragement for the implementation of a cell bank to support an in utero transplantation programme.