An efficient method for the cryopreservation of fetal human liver hematopoeitic progenitor cells

The use of human hematopoietic progenitor cells (HPC) for transplantation r equires efficient recovery methods and cryopreservation procedures. The pur pose of this study was to determine cryopreservation techniques for fetal h uman liver (FHL) CD34(+) cells. We assessed FHL HPC recovery efficiency aft er freezing and thawing by viability testing, fluoresrence-activated cell s orting analysis, and colony-forming ability under different conditions. We also determined optimal cell freezing concentrations and the effect of rate -controlled freezing on cell recovery. Lastly, cell recovery after varying freezing time periods was examined. Our results indicated that optimal cell recovery occurs when: A) cryopreservation medium consists of either 5% dim ethylsulphoxide (DMSO) or 10% DMSO in combination with either 20% fetal bov ine serum (FBS) or 70% FBS and when Iscove's modified Dulbecco's medium con sists of not more than 10% DMSO; B) a rate-controlled freezing device conta iner is used; C) CD34(+) cells are frozen at a concentration of 1 x 10(6)/m l, and D) a thawing temperature of 37 degreesC is used, These observations indicate that cryopreservation of FHL HPC is possible for up to 18 months i n optimal conditions without losing hematopoietic activity.