Angiogenic potential of hypoxia preconditioned human adipose and umbilical cord-derived mesenchymal stem cells: a comparative study

BACKGROUND: Angiogenesis plays an important role in tissue repair. In recent years, one of the main research strategies used to induce angiogenesis in vivo has been via stem cell therapy, especially therapy using mesenchymal stem cells (MSCs). However, the use of MSCs in angiogenesis has also been limited due to the low angiogenic potency of MSCs. Therefore, this study aimed to investigate the effects of hypoxiapreconditioned MSCs from human adipose tissue-derived MSCs (AT-MSCs) and from human umbilical cord-derived MSCs (UC-MSCs). We evaluated the role of hypoxia on the angiogenic potency of these MSCs. METHODS: Both AT-MSCs and UC-MSCs were obtained from an established cell bank and expanded in vitro. After expansion, they were checked for their stemness before use in experiments. MSCs were preconditioned in a hypoxic environment (5% oxygen) for 48 hours. The concentrations of growth factors (such as HGF, bFGF, and VEGF) in the cell culture supernatants collected from culture media of the hypoxiapreconditioned AT-MSCs and UC-MSCs (as well as those from AT-MSCs and UC-MSCs cultured in normoxia) were measured by ELISA. Angiogenic potency-related gene expression markers (such as angiogenin, angiopoietin-1, angiopoietin-2, bFGF, HB-EGF, MMP-9, PDGF-BB, SDF-1 alpha, TGF-beta 1, VEGF, HGF, IL-6, and IL-8) of hypoxic- and normoxic-cultured AT-MSCs and UC-MSCs were evaluated using real-time reverse transcription PCR. In-vivo assessment of the angiogenic potency of hypoxic and normoxic AT-MSCs and UC-MSCs was conducted using an ex ovo quail embryo model (cultured in 6-well plates). The angiogenic potency was evaluated based on the area and length of blood vessels formed in the quail embryos on days 1, 3, 5, and 7 after transplantation with hypoxic AT -MSCs, normoxic AT -MSCs, hypoxic UC-MSCs, or normoxic UC-MSCs, and compared to placebo control (PBS injection). RESULTS : The data showed that preconditioning with hypoxia promoted the secretion of bFGF, VEGF, and HGF by both AT-MSCs and UCMSCs. For AT-MSCs, there was a significant increase in VEGF and bFGF production when preconditioned with hypoxia, compared to normoxia, while HGF production was only slightly increased. For UC-MSCs, there was a significant increase in bFGF and HGF production, but only a slight change in VEGF production when preconditioned with hypoxia, as compared to normoxia. A significant up-regulation of gene expression was observed for angiogenin, angiopoietin-1, angiopoietin-2, bFGF, HB-EGF, HGF, IL-8, MMP-9, PDGF-BB, SDF-1 alpha, TGF-beta 1, and VEGF in both hypoxic AT-MSCs and UC-MSCs, compared to normoxic AT-MSCs and UC-MSCs. In quail embryo models, normoxic UC-MSCs promoted angiogenesis better than normoxic AT-MSCs; however, the angiogenic potency of hypoxic AT-MSCs and UC-MSCs were not significantly different. CONCLUSIONS: The angiogenic potency of UC-MSCs was better than that of AT -MSCs. However, when preconditioned with hypoxia (5% O2), the angiogenic potency of both AT -MSCs and UC-MSCs was similar. In vivo, hypoxic preconditioning could enhance the angiogenic potency of AT-MSCs, compared to normoxic AT-MSCs, although the angiogenic potency of hypoxic and normoxic UC-MSCs was not significantly different.