Fig. 3

a Confocal microscopy of early and late-passage CV-MSC (i–iv), BM-MSC (v–viii), AT-MSC (ix–xii), and UC-MSC (xiii–xvi) analyzed by Q-FISH. Telomeres were stained with Tel-Cy3 peptide nucleic acid probe and chromatin was stained with DAPI (overlaid image on left). Telomere signal alone (black and white image on right) shown to improve visual comparability. Shown side by side are on the left MSC in passage 3 (i, ii, v, vi, ix, x) and on the right MSC in passage 9 (iii, iv, vii, viii, xi, xii), except for UC-MSC that were on the left in passage 1 (xiii, xiv) and on the right in passage 3 (xv, xvi). Scale = 10 μm. b Telomere loss (Δtel) per passage (in arbitrary units (a.u.)) according to Q-FISH. CV-MSC (n = 4), BM-MSC (n = 2), UC-MSC (n = 4), AT-MSC (n = 3) (**p < 0.005). AT adipose tissue, BM bone marrow, CV chorionic villi, MSC mesenchymal stromal cells, UC umbilical cord