Enrichment of lineage⁻CD34⁻ cells using a newly developed filter system

Recent studies have demonstrated the presence of human lineage⁻ (lin⁻)CD34⁻ cells that are capable of differentiating into CD34⁺ cells in xenogeneic transplantation systems. We developed a new filter system that can enrich lin⁻CD34⁻ cells, a precursor cell population of CD34⁺ cells. The filter consists of polyethylene terephthalate non-woven fabrics coated with hydrophilic polymer. The frequency of lin⁻CD34⁻ cells in the cell population after filtration was 7.45 ± 4.41%, a 16.8 ± 8.81-fold enrichment compared with 0.49 ± 0.31% in the cell population before filtration. The mean recovery of lin⁻CD34⁻ cells was 48.57 ± 13.59% (n = 15). Purified lin⁻CD34⁻ cells, obtained by sorting the filtrated cell population, acquired CD34 expression and colony-forming activity after 7 d of culture. Our results indicate that this filter system is useful for isolating lin⁻CD34⁻ cells, including precursors of CD34⁺ cells, and will help further the study of lin⁻CD34⁻ cells.