Fig. 4
Proliferative capacity of conditioned UC tissue-derived cells. a Proliferation of MSC-like cells obtained after reculture of cryopreserved conditioned UC tissues from three different donors (MSC100314UC-re(1), MSC110314UC-re(1), MSC180314UC-re(1)) was evaluated by cell counting in a hemocytometer after initial seeding of 104 cells from each MSC population. Relative proliferative capacity was calculated as fold changes after setting the initial cell number 104 cells = 1. Likewise, a second reculture after repeated cryopreservation of these UC tissue pieces (MSC100314UC-re(2), MSC110314UC-re(2), MSC180314UC-re(2)) demonstrated similar cell growth properties compared with the previous explant culture of the same tissues under the same experimental conditions. Data represent the mean ± SD of three independent experiments. Statistical analysis was performed by Student’s t test (**p <0.001). b A parallel cell cycle analysis of the MSC explant cultures was performed by flow cytometry and demonstrated proliferating cells in all cultures by the appearance of all cell cycle phases in the histograms. c Detection of senescent cells in MSCUC-re(2) explant culture by SA-β-gal staining. Staining of outgrowing MSC-like cells (MSC100314UC-re(2), MSC110314UC-re(2), MSC180314UC-re(2)) obtained from the repeated reculture of a second corresponding tissue cryopreservation with the SA-β-gal kit demonstrated only a marginal expression of this aging marker (arrows) in less than 2 % of the cells. SA-β-gal senescence-associated β-galactosidase