兔卵巢组织玻璃化冷冻的实验研究

目的:探讨玻璃化冷冻法保存兔卵巢组织的效果。方法:随机将25只新西兰雌兔分为对照组(5只)、慢速冷冻组(10只)和玻璃化冷冻组(10只),比较各组冻融前后卵巢组织学、超微结构、卵泡凋亡(原位末端标记法,TUNEL)和子宫系膜内移植后卵巢功能的恢复情况。结果:新鲜组织、慢速冷冻复苏组织和玻璃化冷冻复苏组织中正常形态卵泡比例分别为87.36%、81.96%和82.72%,两冷冻组正常卵泡比例均低于对照组,差异有统计学意义?P(0.05),但玻璃化冷冻组与慢速冷冻组差异无统计学意义(P>0.05)。3组间卵泡凋亡比率分别为21.4%、13.5%和17.1%,差异无统计学意义(P>0.05);3组移植后兔动情周期出现率均为100%,动情周期出现天数差异无统计学意义?P>0.05);移植存活的卵巢组织内可见各级形态正常的卵泡发育。结论:玻璃化冷冻可有效保存卵巢组织的结构和功能,是一种简单、可行的兔卵巢组织冷冻保存法。     

两种玻璃化法冻存小鼠卵巢的研究

目的:探讨2种玻璃化法对小鼠卵巢组织、器官形态和功能保存作用的影响。方法:以改良的DMEM-F12为玻璃化液,分别采用常规玻璃化法(A组)和超速玻璃化法(B组)冻存小鼠卵巢组织及器官,解冻后通过组织学观察、卵巢组织异体、卵巢器官自体肾被膜下移植,观察动情周期恢复率、恢复时间、卵泡发育状况,并分别以新鲜卵巢组织异体移植、卵巢器官自体移植(C组)为对照,评价2种玻璃化法的冻存效果。结果:①A组、B组、C组卵巢组织异体移植小鼠动情周期出现率为100%,出现动情周期分别10.5±5.4d、8.0±2.2d、6.3±1.0d。A组与C组比,差异显著(P<0.05);B组与C组无差异,A组与B组间也无差异(P均>0.05)。②A组、B组、C组卵巢器官自体移植小鼠动情周期出现率为100%,出现动情周期分别为9.4±0.9d、6.9±1.1d、6.1±1.1d,A组与B、C组相比有统计学差异(P<0.05),而B组与C组间无差异(P>0.05)。移植存活的卵巢组织、器官内均可见不同发育阶段的卵泡,形态正常。结论:2种玻璃化法可有效地冻存卵巢组织及器官,但超速玻璃化法效果较优。     

3种玻璃化液对新生鼠卵巢的渗透反应及冻存效果的比较

目的:探索适宜新生鼠卵巢保存的玻璃化液和冷冻方案。方法:观察新生SD大鼠卵巢在预平衡液及3种玻璃化液中不同时间段的表面积变化,冻融后进行组织学观察和成年SD大鼠肾被膜下异体移植后在体活力分析。结果:新生鼠卵巢在预平衡液中出现渗透性脱水变化,移入EFS40(A组)、EG5.5(B组)、EG5.5/30(C组)3种玻璃化液中,再次剧烈皱缩。3min后,卵巢表面积分别为等渗液对照组表面积的63.2%、82.4%、70.8%。此脱水状态的卵巢玻璃化冻融后形态完整的卵泡百分率均与新鲜移植组(D组)无显著性差异(P>0.05);异体移植后,动情周期出现率和动情周期出现时间均与D组无显著性差异(P>0.05)。各冷冻移植组存活移植物均可见不同发育阶段的各级卵泡,但卵泡数目少于D组,移植20d时A组与D组间有显著性差异(P<0.05);移植60d时B组卵泡数少于D组,组间有差异(P<0.05);C组在各时间点上取材的卵泡数与D组均无差异(P>0.05)。结论:在预平衡液中15min、改良的EG5.5/30液中3min的二步渗透平衡法适宜新生鼠卵巢的玻璃化冷冻。     

抗冷冻蛋白Ⅲ减少家兔卵巢组织冷冻损伤的效果观察

目的:评价抗冷冻蛋白Ⅲ(AFPⅢ)对玻璃化冷冻家兔卵巢组织的影响。方法:收集家兔卵巢30只,随机分为新鲜卵巢组、添加AFPⅢ玻璃化冷冻组(AFPⅢ终浓度为500 ng/ml)和常规玻璃化冷冻组,各组10只,解冻后分析各组卵巢的组织学结构、卵泡形态正常率、卵巢组织超微结构、卵母细胞凋亡率及卵泡存活率。结果:新鲜卵巢组的卵泡形态正常率(91.6%)、卵泡存活率(81.75%)显著高于两冷冻组(P0.01),卵母细胞凋亡率(12.0%)显著低于两冷冻组(P0.01);添加AFPⅢ玻璃化冷冻组卵泡形态正常率(77.5%)、卵泡存活率(45.31%)显著高于常规玻璃化冷冻组(分别为62.1%、37.25%)(P0.01),卵母细胞凋亡率(25.8%)显著低于常规玻璃化冷冻组(41.2%)(P0.01)。结论:家兔冷冻卵巢组织的卵泡形态正常率、卵泡存活率显著低于新鲜组织,冷冻保护剂中加入AFPⅢ可减少家兔卵巢组织冷冻损伤。     

4种冷冻-解冻方法对家兔卵巢组织形态学的影响

目的:探讨适宜的卵巢组织冻存方案。方法:采用PROH(A2组)及DMSO(B2组)慢速程序化冷冻和DMSO+PROH(C2组)及DMSO+EG(D2组)玻璃化冷冻方法,冻存家兔卵巢组织,解冻复苏后,以相应的4组新鲜组织为对照(A1-D1组),做HE染色,行组织形态学分析。结果:A1-D1组始基卵泡的形态正常率分别为90.1%、91.5%、91.8%、92.2%,其相对应的A2-D2组分别下降为67.6%、69.7%、70.5%、80.1%,差异均有统计学意义(P均<0.05)。冷冻组中A2组始基卵泡形态正常率最高,与B2、C2、D2组比,差异有显著性(P<0.05)。C2、D2组间比,差异无显著性(P>0.05)。各冷冻组合并后形态正常率始基卵泡为72.7%,初级卵泡为55.7%,两者比较有统计学差异(P<0.05)。4个冷冻组中均可见卵巢组织结构受损的表现。结论:4种冷冻解冻方法对卵巢皮质中各级卵泡及卵巢组织结构均造成一定程度的损害,使各级卵泡的形态正常率明显下降,卵巢间质细胞连接变得疏松;PROH慢速程序化冷冻法明显优于DMSO法及玻璃化法,较适合卵巢组织中始基卵泡的保存;冻存卵巢组织对初级卵泡的影响大于始基卵泡。     

玻璃化冷冻对乳鼠卵巢Dnmt1和Grb10的影响研究

目的探索玻璃化冷冻对乳鼠卵巢Dnmt1和Grb10 mRNA和蛋白表达的影响。方法 26只出生10 d的C57BL/6雌性小鼠,每只乳鼠双侧卵巢均分成新鲜组和玻璃化冷冻组。免疫组织化学法检测Dnmt1蛋白在玻璃化冻融前、后卵巢组织卵泡中的表达变化;通过qRT-PCR检测Dnmt1和Grb10 mRNA在玻璃化冻融前、后卵巢组织中的表达变化;通过Western blotting方法检测Dnmt1和Grb10蛋白在玻璃化冻融前后卵巢组织中的表达变化。结果 Dnmt1在玻璃化冻融前、后的乳鼠卵巢组织各级卵泡的颗粒细胞及卵母细胞胞核表达。与新鲜组相比,玻璃化冷冻组卵巢内Dnmt1蛋白和mRNA表达水平均显著下调(P0.05);Grb10蛋白和mRNA表达水平均显著上调(P0.05)。结论玻璃化冷冻复苏过程导致卵巢内Dnmt1表达降低,使印记基因Grb10过表达,可能使配子糖代谢性表观遗传信息紊乱的的风险增加。     

玻璃化冷冻保存羊卵巢组织异种移植的实验研究

目的:探讨羊卵巢组织玻璃化冷冻复苏后异种移植的卵泡生长发育情况。方法:取绵羊的卵巢,将卵巢皮质切块,应用玻璃化快速冷冻法保存。羊卵巢组织片复苏后在裸鼠的颈部皮下移植,每只裸鼠移植2块组织,于移植1个月后获取移植物,HE染色观察存活卵泡的情况。结果:共移植组织16块,取材时肉眼可见其中一块组织纤维化萎缩,镜下见此块组织纤维化,移植组织存活率87.5%(14/16)。HE染色观察每只移植小鼠的2块移植物中基本只有1块有可视卵泡。1只鼠未见可视卵泡;1只鼠见1个不典型原始卵泡;1只鼠有2个不典型原始卵泡;余下5只鼠的移植卵巢组织中均可见多个典型的存活卵泡。结论:羊卵巢组织经冷冻复苏后能够成功移植于裸鼠的颈部皮下,大部分卵泡处于良好的存活状态。     

冻融后移植的小鼠卵巢组织对促性腺激素的反应

目的 探讨冻融后移植的小鼠卵巢组织对促性腺激素的反应.方法 将36只性成熟雌性小白鼠随机分为新鲜移植组、冻融移植组和对照组,每组12只.新鲜移植组小鼠切除双侧卵巢,将卵巢切成小组织块,立即移植人双侧肾被膜下;冻融移植组小鼠切除双侧卵巢,将卵巢切成小组织块,采用玻璃化冷冻方法冷冻保存,2周后将冷冻卵巢组织复苏,移植入小鼠双侧肾被膜下.卵巢组织移植2周后,新鲜移植组和冻融移植组每组随机取6只小鼠应用7.5 IU人绝经期促性腺激素及10 IU绒毛膜促性腺激素,观察移植后的卵巢组织对促性腺激素的反应.同时应用免疫组化染色方法观察各组卵泡中卵泡刺激素受体的表达情况.结果 新鲜移植组、冻融移植组和对照组未应用促性腺激素小鼠卵巢组织内近成熟卵泡百分率分别为2.3%、2.3%和2.6%,应用促性腺激素小鼠卵巢组织内近成熟卵泡百分率分别为4.2%、4.0%和5.8%,各组内分别比较,差异均有统计学意义(P＜0.05);新鲜移植组和冻融移植组与对照组比较,差异均元统计学意义(P＞0.05).新鲜移植组、冻融移植组和对照组卵泡刺激素受体表达积分吸光度值在窦状卵泡中分别为9408±2777、9175±3093和8838±2064,在窦前卵泡中分别为4531±1903、4808±1386和5516±1136,各组间分别比较,差异均无统计学意义(P＞0.05).结论 卵巢组织冷冻保存、复苏及移植过程未影响卵巢卵泡刺激素受体的表达,冻融后移植的小鼠卵巢组织对外源性促性腺激素的反应未受冷冻、复苏及移植等过程影响.     

自制冷冻环人卵巢组织玻璃化冷冻的可行性研究

目的探讨应用自制冷冻环进行人卵巢组织玻璃化冷冻的效果。方法2008年5月至9月在华中科技大学同济医学院附属同济医院收集5例人卵巢组织标本,以乙二醇、二甲基亚砜、蔗糖作为冷冻保护剂,自制冷冻环为载体进行玻璃化冷冻。并观察卵巢新鲜组织和冻融后组织始基卵泡和初级卵泡的形态学变化、凋亡情况、超微结构变化及体外培养内分泌功能。结果新鲜及冻融后组织形态正常卵泡比值分别是89.46±4.94、84.47±4.66,无统计学意义(P>0.05)。凋亡面积分别是(0.07±0.02)%、(0.10±0.05)%,无明显增加(P>0.05)。超微结构无明显改变。新鲜组织及冻融后组织体外培养上清液雌二醇含量分别(2549.73±711.87)pmol/L、(2514.87±714.66)pmol/L,无统计学意义(P>0.05)。结论自制冷冻环可作为一种便宜、方便、可行的人卵巢组织低温保存的可替代方法。     

荷人卵巢上皮癌裸鼠冻融卵巢组织移植的效果评价

目的:获取人卵巢上皮癌裸鼠原位移植瘤癌旁正常卵巢组织,经安全筛查并冻融后移植至去势裸鼠体内,探讨移植后效果,为临床应用提供依据。方法:将人卵巢上皮癌OVCAR3细胞种植于裸鼠皮下以获取瘤源,并进行卵巢原位移植,建立卵巢癌原位移植瘤模型,解剖裸鼠获取癌旁正常卵巢组织。癌旁组:取筛选后的癌旁卵巢组织进行玻璃化冷冻,复苏后分别进行皮下及原位移植,各20例;对照组:同龄正常裸鼠卵巢组织,皮下移植及原位移植各20例;去势裸鼠组:20只同龄去势裸鼠;正常卵巢组:20只同龄正常裸鼠。移植12周后,分析各组裸鼠卵巢组织内卵泡形态及激素分泌功能。结果:40只人卵巢上皮癌裸鼠原位移植瘤模型中共获取35份活检正常的癌旁卵巢组织,获取率87.5%(35/40)。玻璃化冷冻前后卵巢组织中卵泡形态及各级卵泡比例均无显著差异(P>0.05),癌旁冷冻组织和癌旁新鲜组织的异常卵泡比例差异无统计学意义(P>0.05),冷冻组织以初级卵泡及次级卵泡等窦前卵泡为主。癌旁组皮下移植组织存活率80%(16/20),对照组皮下移植组织存活率90%(18/20),癌旁组原位移植组织存活率90%(18/20),对照组原位移植组织存活率95%(19/20)。移植后组织内卵泡以次级卵泡及窦状卵泡为主,各级卵泡的形态及构成比和未移植的同龄正常裸鼠卵巢相似(P>0.05);癌旁组卵泡数明显低于对照组(P<0.05)及正常卵巢组(P<0.01);皮下移植和原位移植组织内的各级卵泡数差异无统计学意义(P>0.05)。癌旁组卵泡刺激素水平明显低于去势裸鼠组,而雌二醇水平明显高于去势裸鼠组(P<0.01);癌旁组卵泡刺激素水平明显高于对照组(P<0.05)及正常卵巢组(P<0.01),而雌二醇水平明显低于对照组(P<0.05)及正常卵巢组(P<0.01);皮下移植和原位移植的卵泡刺激素水平和雌二醇水平差异无统计学意义(P>0.05)。结论:癌旁卵巢组织冻融移植后有正常卵泡发育及激素分泌功能;皮下移植和原位移植均可取得较好的效果;癌旁卵巢组织冻融移植有望作为卵巢上皮癌患者治疗后恢复卵巢内分泌功能的有效手段。     

Ovarian tissue vitrification: Cortex and whole ovary in sheep

OBJECTIVE: The aim of this study was to evaluate a cryopreservation technique by vitrification of cortex or whole ovaries in sheep, using two cryoprotectant solutions: VS1 and VS4 and to study their physical properties to avoid ice crystallisation by vitrification of whole sheep ovaries permeated with a cryoprotectant solution. ANIMALS AND METHODS: From 6-month-old ewes, whole sheep ovaries with their vascular pedicles were collected at the slaughterhouse or at the veterinary school and prepared for cryoprotectant toxicity tests and freezing procedure. Follicle viability was measured by trypan blue test and histological examination of ovary. The hemi-ovarian cortex was stored in liquid nitrogen. Four to six weeks after the first laparotomy, the controlateral ovary was removed and the vitrified-warmed hemi-ovary was sutured. Thermal properties of a cryoprotectant solution called VS4 (critical cooling rates [Vccr], vitreous transition temperature [Tg], end of melting temperature [Tm]) were measured by differential scanning calorimetry. RESULTS: No significant difference in follicle viability or normal follicle rates was observed between ovarian cortex exposed or non-exposed to cryoprotectant solutions. Nor was any significant difference observed before and after vitrification. Three pregnancies occurred, from which four lambs were born after autografts of vitrified ovarian cortex. With whole ovary, the decrease in the number of normal follicles was lower when frozen-thawed ovaries were treated with VS4 (P = 0.04). There were less nuclear anomalies (P = 0.02). The Vccr of VS4 has been estimated to be 14.3+/-1.1 degrees C/min and Tg was -125.0+/-0.2 degrees C. Because the penetration of cryoprotectants was very low, Vccr was very high and the cooling speed did not allow cortex to vitrify. DISCUSSION AND CONCLUSIONS: Cryopreservation of cortex or whole ovary by vitrification seems a promising technique in reproductive medicine. The best histologic results were obtained with the VS4 cryoprotectant when whole ovary was vitrified.     

Damage to fetal bovine ovarian tissue caused by cryoprotectant exposure and vitrification is mitigated during tissue culture

Purpose

The objective of this study is to characterize the impact of exposure to cryoprotectants followed by vitrification on primordial follicle survival and activation using a fetal bovine model.

Methods

In the first study, fetal bovine cortical pieces were exposed to cryoprotectants with or without sucrose and cultured up to 7 days in the presence or absence of insulin. In the second study, cortical pieces were exposed to cryoprotectants with or without sucrose, vitrified, and cultured up to 7 days after warming in the presence or absence of insulin. Viability and morphology of follicles, as well as proliferation and/or DNA repair in ovarian tissue were analyzed.

Results

When compared to non-exposed controls, normal follicular morphology was affected in groups exposed to cryoprotectants only immediately post-exposure and after 1 day of culture, but improved by day 3 and did not significantly differ by day 7. Similarly, normal follicular morphology was compromised in vitrified groups after warming and on day 1 compared to controls, but improved by days 3 and 7. Proliferation and/or DNA repair in ovarian tissue was not affected by vitrification in this model. Cryoprotectant exposure and vitrification of ovarian tissue did not impair the activation of primordial follicles in response to insulin, although activation was delayed relative to non-exposed controls. Interestingly, sucrose had no noticeable protective effect.

Conclusion

Vitrified fetal bovine ovarian tissue has the intrinsic capacity to mitigate the immediate damage to primordial follicles’ morphology and retains the capacity to activate. These findings provide a basis for a successful cryopreservation protocol for ovarian cortical tissue in other species including humans.     

Effect of vitrification method on survivability, follicular growth and ovulation of preantral follicles in mice

AIM: This study was designed to compare the survival rates, follicular growth rates, and ovulation rates of vitrified preantral follicles (PF) from ovaries with those isolated from a vitrified ovarian cortical strip. METHODS: Mouse ovaries were divided into three groups: those not treated by vitrification of the PF (control), those treated by vitrification of the PF isolated from the ovaries (group I), and those treated by vitrification of ovarian tissue followed by PF isolation (group II). The group I samples were exposed to equilibration solution (EG-20) for 5.0 min plus vitrification solution (EFS-40) for 0.5 min, while the group II samples were exposed to EG-20 for 10.0 min plus EFS-40 for 2.0 min, before vitrification. They were subsequently placed on an electron microscope grid, and submerged immediately in liquid nitrogen. After thawing, the survival rate and the growth rate of the follicles were evaluated every 2 days. RESULTS: In the in vitro condition, the follicles grew and developed into antral follicles in groups I and II. The survival rate of the group I samples was higher than that of the group II samples during the in vitro culture (P<0.05). The growth rates of the follicles in group I were higher than those in group II after day 6 (P<0.05). The ovulation rate of the samples in group I was higher than that of group II (P<0.05). CONCLUSION: These results demonstrated that direct PF vitrification appeared to be better than vitrification of the PF isolated from ovarian tissue.     

Histological and biological assessment of vitrified ovarian follicles from large animals

Mammalian ovaries contain mixed populations of follicles at different developmental stages. A combination of vitrification and growth culture of ovarian follicles could provide the desired number of mature eggs from a preserved small amount of ovarian tissues. Secondary and primordial follicles from porcine and bovine ovaries were vitrified in solutions containing ethylene glycol, dimethyl sulfoxide and different concentrations of sucrose, and assessed via histological examination, viability staining, xenografting to immunodeficient mice, and in vitro culturing. Histological examination revealed the damage to oocytes and the damage to follicle components separately. The effects of sucrose in vitrification solutions on the follicles were different depending on the developmental stage of the follicle, oocyte size, cell type in the follicle, and species. Viability staining with fluorescein diacetate was useful to assess the damage to oocytes in secondary follicles. In the xenografts, vitrified bovine primordial and secondary follicles developed to the antral stage, and vitrified porcine primordial follicles developed to the secondary stage. Furthermore, bovine secondary follicles formed antrum-like structures in culture. These results suggest that histological examination and viability staining are valuable for assessing the direct effects of vitrification and warming conditions on follicles and oocytes, while xenografting and in vitro culturing can be useful for evaluating the developmental ability of vitrified follicles and oocytes.     

Effects of vitrification solutions and equilibration times on the morphology of cynomolgus ovarian tissues

This study assessed the effects of vitrification solutions and equilibration times on morphology of cynomolgus ovarian tissues. Ovarian cortical sections (0.1–0.2 cm thickness) of seven cynomolgus monkeys were randomly allocated to either a control group or one of six vitrification groups. Ovarian tissue sections were vitrified ultra-rapidly by placing them directly into liquid nitrogen using two different vitrification solutions (VSEGP: 5.64 mol/l ethylene glycol + 5% (w/v) polyvinylpyrrolidone + 0.5 mol/l sucrose; and VSED: 3.22 mol/l ethylene glycol + 2.56 mol/l dimethylsulphoxide + 0.5 mol/l sucrose) after three different exposure times (5–20 min). After warming, follicle morphology was analysed using light and transmission electron microscopy. The proportion of morphologically normal follicles vitrified using VSED after a 5-min exposure was lower (P < 0.05) than those vitrified by other conditions. The proportion of normally structured mitochondria in oocytes of preantral follicles vitrified after a 5-min exposure to VSED (56%) was lower (P < 0.01) than those vitrified by other conditions (78–88%). Following tissue vitrification with VSED, the surface ratio of lysosome was increased compared with non-vitrified oocytes (1.64% versus 1.11%; P < 0.05). These results indicate that VSEGP can support the morphology of vitrified preantral follicles and oocytes.Cryopreservation of preantral follicles in ovarian tissues has been expected to be an effective measure for preserving fertility in young women who need to undergo cytotoxic therapy. However, a cryopreservation protocol has not yet been well established. This paper revealed that only 5-min exposure time to a cryoprotectant containing a combination of ethylene glycol and polyvinylpyrrolidone yields better follicle and oocyte morphology at an ultra-structural level in mammalian ovarian tissues after ultra-rapid vitrification using a new ultra-rapid vitrification device compared with a cryoprotectant containing a combination of ethylene glycol and dimethylsulphoxide. Survival rates of cancer patients are increasing. However, patients requiring chemotherapy and/or radiotherapy for cancer, leukaemia or other benign pathologies are likely to experience premature ovarian failure and loss of fertility as a consequence of these potentially gonadotoxic treatments. Use of the procedure reported in this study may increase the chance of fertility preservation.     

Modified vitrification of human pronuclear oocytes: efficacy and effect on ultrastructure

The efficacy of cryopreservation by direct plunging into liquid nitrogen (vitrification) of human pronuclear oocytes using open pulled straws with a super-finely pulled tip, as well as the ultrastructural changes caused by cooling and vitrification, were evaluated. Clinical and electron microscopic studies of cooled and vitrified oocytes were performed. Oocytes were cooled to 4 degrees C in the presence and absence of cryoprotectants, vitrified, warmed, cultured and transferred. Abnormally fertilized oocytes were examined by electron microscopy. Vitrified and warmed 2-pronuclear oocytes showed 71.1% survival rate and 83.3% developmental rate. One- and 3-pronuclear oocytes, after cooling without cryoprotectants (presumably non-viable), showed progressive swelling of mitochondrial smooth endoplasmic reticulum (SER). After vitrification, oocytes (presumably viable) showed the formation of large SER vesicles associated with mitochondria. The described protocol of vitrification of human pronuclear oocytes was shown to be effective in producing pregnancy. Normal ultrastructure after undergoing the described vitrification protocol was confirmed.     

Cryopreservation of mature human oocytes by vitrification with ethylene glycol in straws

OBJECTIVE: To examine the effect of vitrification with ethylene glycol (EG) for mature human oocytes in straws. DESIGN: Prospective, randomized, in vitro experiments. SETTING: Reproductive unit of a university hospital. PATIENT(S): Immature oocytes from 110 patients undergoing intracytoplasmic sperm injection (ICSI). INTERVENTION(S): The immature oocytes were incubated to reach metaphase II (MII). The MII oocytes were treated with EG-based cryoprotectants and vitrified in straws. They were diluted in sucrose solutions, inseminated by ICSI, and cultured in vitro. MAIN OUTCOME MEASURE(S): Survival, fertilization, and embryo cleavage. RESULT(S): The survival rates were greater for oocytes pretreated with 1.5 M of EG (65% for 0 minute, 93% for 5 minutes, and 96% for 10 minutes). The oocytes vitrified in 60 and 90 seconds had a greater rate of fertilization than those vitrified in 120 seconds. There were no differences in survival and fertilization for vitrified oocytes diluted by three or four steps. The cleavage rates to the six- to eight-cell stage were comparable with controls. However, no blastocyst formation was observed in vitrified oocytes. CONCLUSION(S): Vitrification of human oocytes with EG in straws achieves a high rate of survival, fertilization, and early cleavage of embryos. Further studies should be conducted for the improvement of blastocyst formation.