Population doubling and karyotypic analysis. Panel A) Results of hFTs lineage in passage two. Panel B) Results of hFTs lineage in passage 11. We observed high rates of cell division, with gradual decreasing of the population doubling time (PDT) in lineages cultured for a long time. Despite that, no evidence of chromosomal abnormality was observed (Ikaros System, Axiophot 2, Carl Zeiss).