Figure 3. Progenitor/stem cell functional assays. (A) Colony-forming efficiency assay. Left bars show colonies consisting of 16-49 cells. Right bars show colonies consisting of greater than 50 cells. N = 10; Passage 3 (N = 1), Passage 4 (N = 5), Passage 6 (N = 3), Passage 8 (N = 1). Higher colony efficiency of both size colonies is seen with the Small cells. (B) Long-term growth potential. (1) Assumptive total output of cells after cell-sorting (N = 7). Type IV collagen-attached cells out of the 2.0 x 10⁴ sorted Small cell subpopulation yielded cells up to 5.0 x 10⁸ folds, and were significantly more productive. Out of 7, 3 failed further propagation in Medium and Large cells. (C) Long-term growth potential. (2) Days in culture after cell-sorting (N = 7). Large, 26.4 ± 26.6; Medium, 40.1 ± 49.7; Small, 121.1 ± 43.9 days (Mean ± SD). Small cell subpopulations significantly survived longer than Medium and Large cell subpopulations in vitro. (D) Long-term growth potential. (3) Cumulative population doublings after cell-sorting (N = 7). Small cells had an enhanced replicate lifespan. In contrast, the lifespan of Medium and Large cells diminished earlier than that of Small cells. In B, C, and D, each number indicated a different person’s sample.