title: Comparison of conventional and directional freezing for the cryopreservation of human umbilical vein endothelial cells.
abstract: OBJECTIVE
  To compare conventional slow equilibrium cooling and directional freezing (DF) by gauze package for cryopreservation of human umbilical vein endothelial cells (HUVECs).
  
  
  METHODS
  HUVECs were randomly assigned to conventional freezing (CF) and DF by gauze package group. The two groups of HUVECs were incubated with a freezing liquid consisting of 10% dimethylsulfoxide (DMSO), 60% fetal bovine serum (FBS) and 30% Dulbecco's modified Eagle's medium (DMEM) and then put into cryopreserved tubes. CF group, slow equilibrium cooling was performed with the following program: precool in 4°C for 30min, -20°C for 1h, and then immersion in -80°C refrigerator. DF group, the tubes were packaged with gauze and then directional freezing in -80°C refrigerator straightly. One month later, the vitality of HUVECs were calculated between two groups.
  
  
  RESULTS
  There was no significant difference in the survival rate and growth curve between CF and DF groups. The DF group was significantly better than CF group in adherent rates, morphological changes and proliferative ability.
  
  
  CONCLUSIONS
  In the conventional cryopreserved method, cells are slow equilibrium cooling by steps (4°C, -20°C and finally -80°C), which is a complicated and time-consuming process. But the improved DF by gauze package method is better than conventional method, for which is convenient and easy to operate.
authors.affiliation: Department of Ophthalmology, Zhuhai People's Hospital, the Third Affiliated Hospital of Jinan University, Zhuhai 519000, Guangdong Province, China ; Department of Ophthalmology, the First Affiliated Hospital of Jinan University, Guangzhou 510632, Guangdong Province, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Qi
authors.affiliation: Department of Ophthalmology, Affiliated Anhui Provincial Hospital of Anhui Medical University, Hefei 230001, Anhui Province, China.
authors.forename: Qing-Shan
authors.initials: QS
authors.lastname: Ji
authors.affiliation: Department of Ophthalmology, Zhuhai People's Hospital, the Third Affiliated Hospital of Jinan University, Zhuhai 519000, Guangdong Province, China.
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Hou
authors.affiliation: Department of Ophthalmology, the First Hospital of Nanchang, the Third Affiliated Hospital of Nanchang University, Nanchang 330038, Jiangxi Province, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Ophthalmology, the First Affiliated Hospital of Jinan University, Guangzhou 510632, Guangdong Province, China.
authors.forename: Xian-Fen
authors.initials: XF
authors.lastname: Cao
authors.affiliation: Department of Ophthalmology, the First Affiliated Hospital of Jinan University, Guangzhou 510632, Guangdong Province, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
keywords: cryopreservation; directional freezing; human umbilical vein endothelial cells; slow equilibrium cooling