title: Cryobiological Characteristics of L-proline in Mammalian Oocyte Cryopreservation.
abstract: BACKGROUND
  L-proline is a natural, nontoxic cryoprotectant that helps cells and tissues to tolerate freezing in a variety of plants and animals. The use of L-proline in mammalian oocyte cryopreservation is rare. In this study, we explored the cryobiological characteristics of L-proline and evaluated its protective effect in mouse oocyte cryopreservation.
  
  
  METHODS
  The freezing property of L-proline was detected by Raman spectroscopy and osmometer. Mature oocytes obtained from 8-week-old B6D2F1 mice were vitrified in a solution consisting various concentration of L-proline with a reduced proportion of dimethyl sulfoxide (DMSO) and ethylene glycol (EG), comparing with the control group (15% DMSO and 15% EG without L-proline). The survival rate, 5-methylcytosine (5-mC) expression, fertilization rate, two-cell rate, and blastocyst rate in vitro were assessed by immunofluorescence and in vitro fertilization. Data were analyzed by Chi-square test.
  
  
  RESULTS
  L-proline can penetrate the oocyte membrane within 1 min. The osmotic pressure of 2.00 mol/L L-proline mixture is similar to that of the control group. The survival rate of the postthawed oocyte in 2.00 mol/L L-proline combining 7.5% DMSO and 10% EG is significantly higher than that of the control group. There is no difference of 5-mC expression between the L-proline combination groups and control. The fertilization rate, two-cell rate, and blastocyst rate in vitro from oocyte vitrified in 2.00 mol/L L-proline combining 7.5% DMSO and 10% EG solution are similar to that of control.
  
  
  CONCLUSIONS
  It indicated that an appropriate concentration of L-proline can improve the cryopreservation efficiency of mouse oocytes with low concentrations of DMSO and EG, which may be applicable to human oocyte vitrification.
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproduction, Beijing 100191, China.
authors: Lu
authors: L
authors: Zhang
authors: Beijing Key Laboratory of Cryo-Biomedical Engineering and Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors: Xu
authors: X
authors: Xue
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproduction, Beijing 100191, China.
authors: Jie
authors: J
authors: Yan
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Key Laboratory of Assisted Reproduction, Ministry of Education, Beijing 100191, China.
authors: Li-Ying
authors: LY
authors: Yan
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproduction, Beijing 100191, China.
authors: Xiao-Hu
authors: XH
authors: Jin
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproduction, Beijing 100191, China.
authors: Xiao-Hui
authors: XH
authors: Zhu
authors: Beijing Key Laboratory of Cryo-Biomedical Engineering and Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors: Zhi-Zhu
authors: ZZ
authors: He
authors: Beijing Key Laboratory of Cryo-Biomedical Engineering and Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190; Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China.
authors: Jing
authors: J
authors: Liu
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Key Laboratory of Assisted Reproduction, Ministry of Education, Beijing 100191, China.
authors: Rong
authors: R
authors: Li
authors: Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191; Key Laboratory of Assisted Reproduction, Ministry of Education, Beijing 100191, China.
authors: Jie
authors: J
authors: Qiao
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D005260:Female; D005307:Fertilization in Vitro; D006863:Hydrogen-Ion Concentration; D008297:Male; D051379:Mice; D009865:Oocytes / Q000187:drug effects*; D009997:Osmotic Pressure; D011392:Proline / Q000494:pharmacology*; D013059:Spectrum Analysis, Raman; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents; D011392:Proline