DIRECT COMPARISON BY LIMITING DILUTION ANALYSIS OF LONG-TERM CULTURE-INITIATING CELLS IN HUMAN BONE-MARROW, UMBILICAL-CORD BLOOD, AND BLOODSTEM-CELLS

Limiting-dilution analysis of long-term culture-initiating cells (LTCI C) is a quantitative method of estimating hematopoietic stem cell acti vity in clinical samples. We compared the numbers of LTCIC in bone mar row (BM), umbilical cord blood, and blood progenitor cells (obtained f rom patients with solid tumors at leukapheresis after mobilization wit h induction chemotherapy and filgrastim administration). using a two-s tage long-term culture system and a limiting-dilution technique, scori ng cobblestone areas of greater than 15 hematopoietic cells weekly for up to 8 weeks. Samples were obtained from 30 normal BMs, 20 human umb ilical cords, and 32 leukapheresis products. Direct comparison of LTCI C in the three sources showed that the median proportions of cells gen erating hematopoietic foci from unfractionated mononuclear cells at 5 and 8 weeks, respectively, were 1:13,314 and 1:33,949 for BM, 1:12,506 and 1:34,546 for umbilical cord blood, and 1:10,302 and 1:12,891 for leukapheresis product. The estimated proportions of, LTCIC from unfrac tionated mononuclear cells and CD34(+) cells were similar in experimen ts with leukapheresis product. Leukapheresis product was superior to u mbilical cord blood and cord blood to BM at 5 and 8 weeks of culture ( P = .01). In two-stage long-term cultures, more colonies per flask and CD34(+) cells were found in assays of leukapheresis product than in B M or umbilical cord blood cultures (P = .0005). Results obtained by th is simplified limiting-dilution analysis correlated well with standard long-term cultures and can be used as a measure of the stem cell popu lation. These data suggest that the incidence of putative stem cells i n leukapheresis product and umbilical cord blood are at least comparab le with that of BM. (C) 1994 by The American Society of Hematology.