Fig. 1

Stress changes morphology of MSCs and suppresses their spontaneous differentiation into adipocytes. a Microscopy pictures of time-dependent effects of serum starvation, hypoxia, and their combination on MSCs morphology. Cells were regularly observed under the microscope, photographs were taken at 3, 21, 28 and 42 days in culture. Pictures are representative data of six independent experiments. b Spontaneous differentiation of MSCs towards adipocytes, detected by Oil Red O at day 42 in normoxic culture, is much less prominent in starved, hypoxic, or combined hypoxic-starved (H/S) cultures. c Long-term (day 42) MSC culture growth measured by flow cytometry analysis (FACS). Only non-apoptotic (Annexin V-negative) cells are shown. From c to f: means with SEM of three experiments are shown. ^* P <0.1, ^** P <0.05, ^*** P <0.01, Dunnett’s test. d Flow cytometry analysis of apoptosis in long-term MSC culture (Annexin V-positive cells are presented). e Cell death in long-term MSC culture (FACS). Staining was done by Annexin V and 7AAD, 7AAD-positive cells are shown. f Cell cycle analysis shows cells entered S phase at day 42 (FACS). Western blot analysis detects full-length PARP (116 kDa) and cleaved PARP fragment (89 kDa) in MSC cell line (g) and in primary stromal cells (h), thereby confirming apoptosis at day 42