OBJECTIVETo observe the effects of conditioned medium from keloid fibroblasts under hypoxia on angiogenesis, and to investigate the role of hypoxic microenvironment in invasive growth of keloid.

METHODSPrimary keloid fibroblasts and human umbilical endothelial cells (HUVEC) were cultured as conventional method. Keloid fibroblasts were cultured either in a hypoxic incubator (2% O2) for 48 h or in a normoxic incubator (20% O2) as control. Then those cell culture mediums were collected and mixed with endothelial cell medium by the proportion of 1:1 as conditioned medium. The mRNA and secreted protein of pro-angiogenic factors such as vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and periostin of keloid fibroblasts under hypoxia were detected by real time PCR and ELISA. The proliferation, migration and invasion, tube formation of HUVEC cultured with conditioned medium were evaluated by CCK-8 assay, Transwell assay and matrigel tube formation assay, respectively.

RESULTSHypoxia increased the expression of VEGF, Ang-1 and periostin in both mRNA (increased by 75%, 43% and 118% respectively, P < 0.05) and secreted protein (increased by 30.2%, 14.2% and 19.5% respectively, P < 0.05) levels; the proliferations of HUVEC in hypoxic conditioned medium in 1, 2 and 3 d were 0.67 +/- 0.07, 0.84 +/- 0.09 and 1.08 +/- 0.10 respectively, which were higher compared to those in control group (0.52 +/- 0.08, 0.72 +/- 0.10 and 0.91 + 0.14, P < 0.05); the numbers of migration, invasion and tube formation of HUVEC were (73.2 +/- 8.9), (56.3 +/- 12.5), (9.66 +/- 1.96) cells/HP, which were higher compared to those in control group [(59.0 +/- 8.0), 35.5 +/- 8.5), (6.5 +/- 1.87) cells/HP, P < 0.05].

CONCLUSIONSHypoxia increases the expression of pro-angiogenic factors of keloid fibroblasts, and its conditioned medium under hypoxia could promote angiogenesis. The results suggest hypoxic microenvironment may play a significant role in the invasive growth of keloid by inducing angiogenesis.