Background: There are controversial reports on the effects of human amnion epithelial cells (hAECs) on angiogenesis. hAECs have been reported to secrete several angiogenic factors in vitro but this did not correlate with increase in vessel sprouts or vessel lengths in healthy animals. It is yet unknown if hAECs affect angiogenesis during inflammation.
Aims: (i) To evaluate the effect of hAECs on angiogenesis in the presence of TNF-a and IFN-g in vitro. (ii) To determine if hAECs promote angiogenesis in vivo when administered to hyperoxia-injured neonatal mice.
Hypothesis: hAECs promote angiogenesis in an inflammatory environment.
Methods: Human umbilical vein endothelial cells (HUVECs) were cultured on matrigel in the presence of either hAEC conditioned media or control media. Gene expression of VEGFA, PDGFB and TIMP2 were measured by q-PCR in hAECs cultured with and without TNF-a and IFN-g. Neonatal mice exposed to hyperoxia from birth (85% Fi02) were administered hAECs intraperitoneally. Immunohistochemistry for CD31 was done on postnatal day 14 lung tissue.
Results: HUVECs formed longer vascular tubes following culture in hAEC conditioned media (88.03±15.25 mm vs 57.45±5.72 mm, p<0.001). Following stimulation with TNF-a and IFN-g, hAECs increased gene expression of VEGFA and PDGFB (2.72±0.20 and 8.21±0.57 times respectively), and TIMP2 expression was decreased (0.86±0.60 vs 0.10±0.03, p<0.05) compared to control. CD31 staining was not significantly different between cohorts of hyperoxia-injured animals.
Conclusion: hAECs release soluble factors that promote angiogenesis and this effect was magnified in the presence of inflammatory cytokines in vitro. hAEC administration did not significantly increase angiogenesis in hyperoxia-injured mice, suggesting that this is not a major mechanism by which hAECs elicit their protective and/or reparative effects.