Hpmec

First-passage HPMECs were obtained from ScienCell Research Laboratories (Carlsbad, CA, USA). An additional ethical approval for HPMEC use shows this in more detail (Additional file 2). HPMECs were routinely characterised by the supplier. HPMECs were added into the upper chambers of 0.4-μm cell-culture inserts at a density of 50,000 cells per insert well and cultured in EGM-2 (endothelial growth media-2) (ScienCell Research Laboratories). The culture media were changed every 3 days, and the cells were used at passages 3 to 7 for all experiments.

Human mesenchymal stem cells (hMSCs) were purchased from Cyagen Biosciences, Inc. (Guangzhou, China). Human pulmonary microvascular endothelial cells (HPMECs) were obtained from ScienCell Research Laboratories. hMSCs were cultured in MSC growth medium (Cyagen Biosciences, Inc.), and HPMECs were cultured in endothelial growth medium (EGM-2; ScienCell Research Laboratories, USA). The cells were cultured in a humidified 5 % CO₂ incubator at 37 °C. The culture media were changed every 2–3 days, and the cells at passages 3–7 were used for all experiments.

Human umbilical vein endothelial cells (HUVECs) and human pulmonary microvascular endothelial cells (HPMECs) were purchased from Typical Animal Reserve Center of China (Shanghai, China) and ScienCell (Carlsbad, CA), respectively. Both HUVECs and HPMECs were cultured in endothelial cell medium (ECM, ScienCell, Carlsbad, CA) and cells harvested at passages 3–10 were used in assays. Human hepatocellular carcinoma (HCC) Hep3B cells were obtained from ATCC and cultured in DMEM supplemented with 10% FBS, 100 U/mL penicillin, and 100 mg/mL streptomycin. Human lung carcinoma cells (A549) were obtained from the China Centre for Type Culture Collection (CCTCC, Wuhan, China) and cultured in RPMI-1640 supplemented with 10% FBS, 100 U/mL penicillin, and 100 mg/mL streptomycin. Human erythroleukemia TF-1 cells were purchased from ATCC and cultured in RPMI-1640 supplemented with 2 ng/mL rhGM-CSF and 10% FBS. Human glioblastoma U87-MG cells were from ATCC (Molsheim, France) and cultured in DMEM supplemented with 10% FBS, 100 U/mL penicillin, and 100 mg/mL streptomycin. All the above cells were incubated at 37 °C under 95% air and 5% CO₂. A hypoxic condition was created in a hypoxia chamber (Billups-Rothenberg, Inc., San Diego, CA) equilibrated with certified gas containing 1% O₂, 5% CO₂, and 94% N₂.