Fig. 4
Reversibility of growth inhibition induced by cyclic mechanical stretch (CMS) and hyperoxia (HOX) in umbilical cord mesenchymal stem cells (UC-MSC) depending on strength and duration of the exposure (HOX 80%). (A) Bright-field microscopy of proliferation after 24 h of selective and/or combined exposure to CMS and HOX 80%. Outgrowth (OG) of cells in all intervention groups after further 3 days of recovery in room air without CMS. Scale bar 250 μm. (B) Bright-field microscopy of proliferation after 48 h of selective and/or combined exposure to CMS and HOX 80%. Outgrowth (OG) of cells in all intervention groups after further 3 days of recovery in room air without CMS (*after further 6 days in the HOX 80% and CMS + HOX 80% treatment group). Scale bar 250 μm. (C) Bright-field microscopy of proliferation after 72 h of selective and/or combined exposure to CMS and HOX 80%. OG of cells only in the selective treatment groups (CMS; HOX 80%) but not in combined treatment group (CMS + HOX 80%) after 6 days of recovery in room air without CMS. Representative experiments of n = 3. Scale bar 250 μm. (D) Change in cell expansion index (CEI) after 24 h/48 h/72 h of exposures was calculated as in Fig. 1D. CMS and/or hyperoxic exposure led to a time-dependent inhibition of MSC proliferation. Representative images of one experiment from n = 3 independent MSC cultures are displayed in A–C. In D, data are expressed as box plot with median and interquartile range, *p < 0.05, **p < 0.01, by paired t-test, comparing exposures to the control situation.
