Figure 1: Human spermatogonia cultured in vitro after CD49f- and matrix-selection. (a) Typical morphology of spermatogonia from same patient 184 during culture: (A) after one week, (B) after one month, (C) after three months, and (D) after six months. Single and interconnected round cells with high nucleus/cytoplasm ratio typical of spermatogonia were observable. Pairs, chains, and small groups/colonies of interconnected spermatogonia were present in all cell cultures. Long-term cultured cells were grown on inactivated CF1 feeder cells. Cultures were devoid of human fibroblasts. (E) Purified VASA-positive germ cell cultures were devoid of VIMENTIN-positive somatic cells. (b) Collection of spermatogonia by a micromanipulation system (micropipette) for gene expression profiling (A). (B) Example of selected spermatogonia is shown as insert. Magnification (a): (A)–(D) 10x, (E/1)–(E/4) 20x; (b): (B) 5x, insert 20x.