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。     

银制封闭式冷冻载体改善人卵巢组织异种移植效果的研究

目的:探讨银制封闭式玻璃化冷冻载体促进人卵巢组织冷冻后移植严重免疫缺陷(SCID)鼠新生血管效果。方法:收集2015年4月至2016年6月在我院妇科手术治疗的患者卵巢组织共8例,每例患者标本随机等量分配到银制封闭式冷冻管及传统封闭式冷冻管玻璃化冷冻保存。选取40只SCID鼠,分为银制封闭式玻璃化冷冻管组及传统封闭式玻璃化冷冻管组(每组20只),分别移植两种封闭式玻璃化冷冻法复苏后的卵巢皮质到SCID鼠皮下,测定CD31反映卵巢皮质新生血管,比较两组人卵巢组织冷冻复苏后移植SCID鼠皮下保存效果。结果:移植后3天和7天,两组中卵巢皮质新生血管数差异无统计学意义(P0.05);移植后14天和21天,银制封闭式玻璃化冷冻管组中卵巢皮质新生血管数高于传统封闭式玻璃化冷冻管组(P0.05)。结论:银制封闭式玻璃化冷冻管与传统封闭式玻璃化冷冻管相比能更好地保存卵巢皮质功能,在深低温保存人卵巢组织中具有应用价值。     

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。     

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.     

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。     

两种冷冻保护剂玻璃化冷冻小鼠卵巢的比较研究

目的:探讨两种玻璃化冷冻保护剂对小鼠卵巢组织学和功能的影响。方法:将23只4周龄ICR雌鼠随机分为新鲜卵巢移植组(6只)、去势组(5只)、EG40组(6只)和ED20组(6只)。EG40组和ED20组分别应用乙二醇(EG)和联合应用EG与二甲基亚砜(DMSO)玻璃化冷冻小鼠卵巢组织,一周后解冻,将一部分复苏卵巢组织自体移植入小鼠肾被膜下,另一部分组织行组织学观察。移植术后5d开始观察所有小鼠的动情周期,一个月后处死小鼠,对存活的卵巢组织行组织学观察。结果:EG40组、ED20组和新鲜卵巢移植组小鼠动情周期出现率均为100%,出现动情周期的天数分别为10.2±1.2d、8.0±0.9d和6.8±1.0d,EG40组动情周期出现天数明显多于新鲜卵巢移植组(P<0.01);ED20组与新鲜卵巢移植组差异无显著性(P>0.05)。移植存活的卵巢组织内可见不同发育阶段的卵泡,形态正常,但冻融卵巢组织内卵泡数量比新鲜组织少。结论:联合应用玻璃化冷冻保护剂EG和DMSO对小鼠卵巢组织学和功能的影响较小。     

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。     

卵巢组织冷冻移植过程中抗卵泡凋亡的研究进展

卵巢组织冷冻和移植在女性生育力保存中具有重要作用,但卵巢组织冷冻和移植过程会 导致大量卵泡凋亡,缩短了移植物存活时间,严重影响卵巢组织移植后生殖内分泌功能的维持时间, 从而限制了卵巢组织冷冻和移植技术的临床应用。 卵巢组织移植后早期经历缺血缺氧及再灌注损 伤,是造成卵泡大量凋亡的重要因素。 因此,卵巢组织移植后尽快促进血管生成,恢复血供,减轻氧 化应激,降低缺血再灌注损伤是移植成功的关键。 本文综述在卵巢组织冷冻和移植过程中,添加凋 亡抑制剂、促血管生成因子、抗氧化剂,应用干细胞、中药以及联合治疗,是否能促进移植组织血管生 成,减轻局部氧化应激及炎症反应,抑制卵泡凋亡,改善冻融卵巢组织移植存活率,为卵巢组织冷冻 和移植技术临床应用提供依据。     

人脐血单个核细胞移植治疗放射性裸鼠卵巢早衰

目的:探讨人脐血单个核细胞(HCMNCs)移植治疗卵巢早衰(POF)的可行性及疗效。方法 :雌性BALB/C裸鼠105只,随机分为空白对照组、POF对照组、POF+人脐血单个核细胞移植组。钴60γ射线照射建立POF模型,聚蔗糖(Ficoll)密度梯度离心法制备HCMNCs悬液,并以5-溴-2′-脱氧尿苷(BrdU)标记。POF造模成功后,移植组双侧卵巢内注入标记的HCMNCs悬液,POF对照组双侧卵巢内注入同等量的达尔伯克改良伊格尔氏低培养基(L-DMEM)培养液,空白对照组未行任何处理。移植后4周,酶联免疫吸附试验(ELISA)法测定血清雌二醇(E2)、卵泡刺激素(FSH)、黄体生成激素(LH)水平变化,并取卵巢组织行苏木素-伊红(HE)染色、BrdU组化染色,观察卵巢卵泡数目变化及移植细胞成活情况。结果:在移植组发现移植的脐血单个核细胞可在早衰的卵巢内存活并参与卵巢功能的修复;血清E2、FSH、LH与POF对照组相比,E2明显升高(P<0.05),FSH和LH明显降低(均P<0.05);卵巢切片HE染色示未闭锁卵泡数目有所增加,并可见各个发育阶段卵泡;免疫组化示移植的人脐血单个核细胞可在裸鼠卵巢内定居并存活。结论:HCMNCs可成功植入裸鼠放射性早衰卵巢内,并能改善其功能。     

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。     

冻存复苏人卵巢皮质在裸鼠体内的发育及卵细胞的提取

目的:探求冻存复苏人卵巢皮质在裸鼠体内的发育及卵细胞的提取。方法:取手术切除的5例患者卵巢皮质,放入1.5 mol/L的二甲基亚砜+10％血清中,应用可控程序冷冻仪逐渐降温,移入液氮中冻存。三个月后,将融解的卵巢皮质移植入89只裸鼠皮下,注射hFSH 12周,刺激卵泡生长。注射hCG 36 h后,用18号针头穿刺提取卵细胞。结果:卵泡直径为3～9 mm,穿刺获19个卵细胞,放入TC-199培养基,加20％胎牛血清,25 mmol/L丙酮酸,75 mIU/mL FSH和LH培养,获15个分裂中期的次级卵母细胞。结论:人卵巢组织冻融后可异体移植生长,且其卵细胞可在体外发育成熟。     

Follicular growth in fresh and cryopreserved human ovarian cortical grafts transplanted to immunodeficient mice.

OBJECTIVE: To investigate follicle growth in fresh and cryopreserved human ovarian cortical grafts transplanted to immunodeficient mice. STUDY DESIGN: Fresh or frozen-thawed human ovarian cortex was grafted subcutaneously or under the kidney capsule of 43 mice (35 nude mice and eight SCID mice), 14 of which were non-stimulated controls, 21 injected intra-peritoneally with gonadotrophins during 2 weeks and eight injected during 3 months. Follicle count was compared by Chi-square. RESULTS: Proportions of primordial follicles were significantly lower in grafts than in the tissue before transplantation in gonadotrophin-stimulated mice (37% versus 79%), but not in non-stimulated mice (51% versus 74%). Proportions of primary and secondary follicles were increased after transplantation indicating early follicular growth. One antral follicle was observed in a graft in a mouse stimulated for 3 months. CONCLUSION: Primordial follicles in fresh or frozen-thawed human ovarian cortex transplanted under the kidney capsule or subcutaneously can grow and are responsive to hormonal stimulation. Condensation: Primordial follicles in fresh and cryopreserved human ovarian cortical grafts can initiate growth after transplantation to immunodeficient mice     

Histologic and ultrastructural evaluation of fresh and frozen-thawed human ovarian xenografts in nude mice

OBJECTIVE: To compare histologic and ultrastructural characteristics of fresh and frozen-thawed human ovarian cortical tissue grafted into nude mice. DESIGN: Experimental prospective study. SETTING: An academic research environment. PATIENT(S): Ovarian biopsy specimens were obtained from 13 women undergoing laparoscopy for tubal ligation or infertility. ANIMAL(S): Forty nude mice. INTERVENTION(S): A minilaparotomy was performed to place fresh and frozen-thawed ovarian grafts subcutaneously (sc) or intraperitoneally (ip). Removal of the ovarian grafts was performed at 24 days. MAIN OUTCOME MEASURE(S): [1] the follicular population, [2] fibrosis, [3] vascularization of the grafted tissue, and [4] ultrastructural evaluation. RESULT(S): A greater fibrosis relative surface area was noted in frozen-thawed transplanted tissue than in fresh transplants. Regardless of this fibrosis, a similar follicular density was observed in fresh and frozen-thawed ovarian tissue 24 days after transplantation. Active angiogenesis was proved by both immunohistochemical study of the vascular endothelial growth factor and morphometric study of the vascular network. Normal ultrastructural characteristics were noted in frozen-thawed ovarian biopsies. CONCLUSION(S): Angiogenesis allows implantation of the graft even if it has been cryopreserved and thawed similarly to implantation of fresh tissue. The greater fibrosis observed in grafts after cryopreservation and implantation does not seem to affect the primordial and primary ovocyte population and their ultrastructural characteristics, but further studies must be conducted to prove that after cryopreservation and transplantation, ovocytes may achieve full maturation and fertilization.     

Blastocyst Development After Cryopreservation and Subcutaneous Transplantation of Mouse Ovarian Tissue

Purpose To investigate follicle survival and developmental potential with IVF of cryopreserved, subcutaneously transplanted mouse ovarian tissue.Methods Fresh and frozen mouse ovarian tissue was autologously transplanted into subcutaneous tissue. Two weeks after the transplantation, the morphology and histology of the fresh and frozen grafts were compared. Superovulation and IVF was performed to evaluate the fertility potential of the frozen ovarian graft.Results Both fresh and frozen grafts of ovarian tissue survived in 14 of 16 mice (88%). Morphologically, both types of grafts resembled fresh ovarian tissue and contained follicles at all stages of folliculogenesis. A total of 73% of follicles in fresh grafts and 62% in frozen grafts survived after transplantation compared with fresh ovarian tissue. Sixteen ICR mice underwent superovulation. A total of 56 oocytes from antral follicles were recovered from the subcutaneously transplanted cryopreserved ovarian tissue. Fourteen (25%) oocytes were in metaphase II stage, 6 were fertilized by IVF, and 2 progressed to the blastocyst stage.Conclusions Cryopreservation and subcutaneous transplantation of ovarian tissue provides a possible means of fertility preservation. The main loss of follicles occurred during grafting rather than during freezing and thawing.     

Production of the first offspring from oocytes derived from fresh and cryopreserved pre-antral follicles of adult mice

Although mammalian ovaries contain hundreds of thousands of pre-antral follicles, fewer than 1% of these reach maturity and ovulation. Obtaining immature eggs from the pre-antral follicles of ovarian tissue could increase the possibility of preserving fertility in women undergoing anti-cancer treatment, and in women who wish to delay pregnancy and child raising until they are older. This study reports the birth of 10 healthy mouse pups derived from oocytes obtained from pre-antral follicles after adult ovary tissue cryopreservation and allotransplantation. High in-vitro maturation (55.1%), fertilization (76.3%) and cleavage (98.3%) rates were achieved using these oocytes, and there was no significant difference between the vitrified and control samples except in maturation rate (55.1 versus 72.8%, P < 0.05). After an ultra-rapid vitrification procedure, the warmed tissue fragments were transplanted beneath the kidney capsule of severe combined immunodeficient mice for onward in-vivo culture. Within 10 days of culture, 138 full size oocytes developed from the 456 transplanted pre-antral follicles. In-vivo growth of follicles was followed by in-vitro oocyte maturation, in-vitro fertilization and subsequent embryo transfer, leading to the birth of 10 healthy pups. These results may lead to increasing the possibility of preserving fertility by cryopreservation of ovarian tissue.     

Growth of follicles of various animals following ovarian grafting under the kidney capsules of immunodeficient mice

Aim:  Various researchers have studied xenografting ovarian tissues into immunodeficient mice to accelerate the follicular growth of several mammalian species. In this study, the authors focused on the following three points in growing follicles in transplanted ovarian tissues under kidney capsules: the effects of the storage conditions of the donor ovarian tissues, the effects of donor age on the survival rates of grafted mouse ovaries, and the methods used to grow the follicles of xenografted bovine ovaries.
Methods and Results:  When ovaries stored for 0, 6, 12 or 24 h at 4°C and at room temperature were transplanted under the kidney capsules of immunodeficient mice, fewer mouse and rabbit grafts survived following 24 h storage. The survival rates of bovine grafts were relatively low for all storage times. When mouse ovaries were held for 24 h at 4°C or at room temperature, low-temperature storage effectively improved the survival rates of the grafts. Although the survival rates of grafted genital ridges containing premeiotic germ cells from fetuses and grafted ovaries from mice 0, 10, 20, 40 and 80 days after birth were similar among donors of different ages, the cleavage rate of oocytes following insemination was significantly lower in the grafts from the ovaries of 80-day-old mice. Antral follicles formed in surviving bovine ovarian grafts. Cumulus–oocyte complexes were collected from the grafted ovaries of fetuses and calves, and the oocytes reached the metaphase II stage following culture, but they did not develop to the pronuclear stage after in vitro fertilization.
Conclusion:  Our findings provide basic data on xenografting ovarian tissues into immunodeficient mice to accelerate the growth of follicles. (Reprod Med Biol 2008; 7 : 45–54)     

重组腺病毒bcl-xs基因对人卵巢癌裸鼠移植瘤作用的研究

目的 观察重组腺病毒bcl-xs基因（adv-bcl-xs基因,简称bcl-xs基因）对人卵巢癌裸鼠移植瘤的生长抑制和荷瘤裸鼠生存率的影响。为卵巢癌的基因治疗提供实验基础。方法 采用以复制缺陷型腺病毒bcl-xs基础感染的人胚肾细胞,使bcl-xs基因对NUTU-19细胞的生长抑制作用并检测其病毒滴度后,将bxl-xs基因导入人卵巢癌裸鼠移植瘤中,观察bcl-xs基因对腹水的生长抑制作用,计算裸鼠的生存时间,并观察bcl-xs基因对裸鼠全身和局部的毒副作用。电镜观察bcl-xs基因的病毒颗粒,以免疫细胞化学染色测定bcl-xs基因表达情况。结果 bcl-xs基因可在人胚肾细胞内扩增,对NUTU-19细胞有抑制和杀伤作用。并在裸鼠体内呈过度表达,使裸鼠腹水形成的时间由5-10d延长至11-23d,裸鼠平均生存时间由24d延长至39d,bcl-xs基因对裸鼠全身和局部无明显毒副作用。结论 bcl-xs基因导入人卵巢癌裸鼠移植肿瘤,能延缓腹水形成,延长裸鼠的生存时间,为卵巢癌的基因治疗提供了一种新方法。     

Survival of mouse ovarian tissue transplanted into the uterine horn of postpartum rats nursing pups of various numbers and sizes

Aim and background  To investigate the effect of the number of pups being nursed on the survival of mouse ovarian tissue transplanted into the post-partum rat uterus. Methods  Mouse ovarian tissue was transplanted into the uterine horn of post-partum rats. The number of pups nursed by each recipient rat was adjusted in a manner predetermined. Examinations were undertaken at 1–11 weeks after transplantation. Ovarian tissue containing healthy follicles was considered to have taken successfully. Results  In rats with 12 pups, ovarian tissue remained viable at 11 weeks post-transplantation. No viable ovarian tissue remained when there were one or two pups. Viability improved as the number of pups increased. Conclusion  When mouse ovarian tissue is transplanted into post-partum lactating rats, viability improves as the number of pups increases. We concluded that these findings may be explained in terms of progesterone levels in the recipient rats.