MHC-DRB alleles with amino acids Val11, Phe13, and the shared epitopes promote collagen-induced arthritis and a rapid IgG1 response in Filipino cynomolgus macaques

Macaques are useful animal models for studying the pathogenesis of rheumatoid arthritis (RA) and the development of anti-rheumatic drugs. The purpose of this study was to identify the major histocompatibility complex (MHC) polymorphisms associated with the pathology of collagen-induced arthritis (CIA) and anti-collagen IgG induction in a cynomolgus macaque model, as MHC polymorphisms affect the onset of CIA in other animal models. Nine female Filipino cynomolgus macaques were immunized with bovine type II collagen (b-CII) to induce CIA, which was diagnosed clinically by scoring the symptoms of joint swelling over 9 weeks. MHC polymorphisms and anti-b-CII antibody titers were compared between symptomatic and asymptomatic macaques. Four of 9 (44%) macaques were defined as the CIA-affected group. Anti-b-CII IgG in the affected group increased in titer approximately 3 weeks earlier compared with the asymptomatic group. The mean plasma IgG1 titer in the CIA-affected group was significantly higher (p < 0.05) than that of the asymptomatic group. Furthermore, the cynomolgus macaque MHC (Mafa)-DRB1*10:05 or Mafa-DRB1*10:07 alleles, which contain the well-documented RA-susceptibility five amino acid sequence known as the shared epitope (SE) in positions 70 to 74, with valine at position 11 (Val11, V11) and phenylalanine at position 13 (Phe13, F13), were detected in the affected group. In contrast, no MHC polymorphisms specific to the asymptomatic group were identified. In conclusion, the presence of V11 and F13 along with SE in the MHC-DRB1 alleles seems essential for the production of IgG1 and the rapid induction of severe CIA in female Filipino cynomolgus macaques.

Generation of a familial hypercholesterolemia model in non-human primate

Familial hypercholesterolemia (FH) is an inherited autosomal dominant disorder that is associated with a high plasma level of low-density lipoprotein (LDL) cholesterol, leading to an increased risk of cardiovascular diseases. To develop basic and translational research on FH, we here generated an FH model in a non-human primate (cynomolgus monkeys) by deleting the LDL receptor (LDLR) gene using the genome editing technique. Six LDLR knockout (KO) monkeys were produced, all of which were confirmed to have mutations in the LDLR gene by sequence analysis. The levels of plasma cholesterol and triglyceride were quite high in the monkeys, and were similar to those in FH patients with homozygous mutations in the LDLR gene. In addition, periocular xanthoma was observed only 1 year after birth. Lipoprotein profile analysis showed that the plasma very low-density lipoprotein and LDL were elevated, while the plasma high density lipoprotein was decreased in LDLR KO monkeys. The LDLR KO monkeys were also strongly resistant to medications for hypercholesterolemia. Taken together, we successfully generated a non-human primate model of hypercholesterolemia in which the phenotype is similar to that of homozygous FH patients.

Induction of fetal meiotic oocytes from embryonic stem cells in cynomolgus monkeys

Human in vitro oogenesis provides a framework for clarifying the mechanism of human oogenesis. To create its benchmark, it is vital to promote in vitro oogenesis using a model physiologically close to humans. Here, we establish a foundation for in vitro oogenesis in cynomolgus (cy) monkeys (Macaca fascicularis): cy female embryonic stem cells harboring one active and one inactive X chromosome (Xa and Xi, respectively) differentiate robustly into primordial germ cell-like cells, which in xenogeneic reconstituted ovaries develop efficiently into oogonia and, remarkably, further into meiotic oocytes at the zygotene stage. This differentiation entails comprehensive epigenetic reprogramming, including Xi reprogramming, yet Xa and Xi remain epigenetically asymmetric with, as partly observed in vivo, incomplete Xi reactivation. In humans and monkeys, the Xi epigenome in pluripotent stem cells functions as an Xi-reprogramming determinant. We further show that developmental pathway over-activations with suboptimal up-regulation of relevant meiotic genes impede in vitro meiotic progression. Cy in vitro oogenesis exhibits critical homology with the human system, including with respect to bottlenecks, providing a salient model for advancing human in vitro oogenesis.

Impact of administering umbilical cord-derived mesenchymal stem cells to cynomolgus monkeys with endometriosis

Purpose

This study aimed to explore whether umbilical cord-derived mesenchymal stem cells (UC-MSCs) could be used as a therapeutic resource for endometriosis.

Methods

Of seven cynomolgus monkeys with endometriosis, five were administered UC-MSCs (intervention group) and two were administered saline (control group). First, intravenous US-MSC treatment was administered for three months. Second, weekly intravenous US-MSC administration combined with monthly intraperitoneal US-MSC administration was conducted for 3 months. Finally, weekly intraperitoneal US-MSC administration was conducted for 3 months. The dose of UC-MSCs was set to 2 × 106 cells/kg for all administration routes. Laparoscopic findings and serum cancer antigen 125 (CA125) levels were also evaluated. The Revised American Society for Reproductive Medicine classification was used for laparoscopic evaluation.

Results

Laparoscopic findings showed exacerbation of endometriosis after intraperitoneal UC-MSC administration, although no changes were observed in the control group. Intravenous UC-MSC administration decreased the level of CA125 in all monkeys; however, the difference was not significant. Intraperitoneal UC-MSC administration significantly exacerbated endometriosis compared with intravenous administration (p = 0.02).

Conclusions

This study revealed that intraperitoneal UC-MSC administration exacerbates endometriosis in a nonhuman primate model of the disease.

Ex vivo reconstitution of fetal oocyte development in humans and cynomolgus monkeys

In vitro oogenesis is key to elucidating the mechanism of human female germ-cell development and its anomalies. Accordingly, pluripotent stem cells have been induced into primordial germ cell-like cells and into oogonia with epigenetic reprogramming, yet further reconstitutions remain a challenge. Here, we demonstrate ex vivo reconstitution of fetal oocyte development in both humans and cynomolgus monkeys (Macaca fascicularis). With an optimized culture of fetal ovary reaggregates over three months, human and monkey oogonia enter and complete the first meiotic prophase to differentiate into diplotene oocytes that form primordial follicles, the source for oogenesis in adults. The cytological and transcriptomic progressions of fetal oocyte development in vitro closely recapitulate those in vivo. A comparison of single-cell transcriptomes among humans, monkeys, and mice unravels primate-specific and conserved programs driving fetal oocyte development, the former including a distinct transcriptomic transformation upon oogonia-to-oocyte transition and the latter including two active X chromosomes with little X-chromosome upregulation. Our study provides a critical step forward for realizing human in vitro oogenesis and uncovers salient characteristics of fetal oocyte development in primates.

The developmental origin and the specification of the adrenal cortex in humans and cynomolgus monkeys

Development of the adrenal cortex, a vital endocrine organ, originates in the adrenogonadal primordium, a common progenitor for both the adrenocortical and gonadal lineages in rodents. In contrast, we find that in humans and cynomolgus monkeys, the adrenocortical lineage originates in a temporally and spatially distinct fashion from the gonadal lineage, arising earlier and more anteriorly within the coelomic epithelium. The adrenal primordium arises from adrenogenic coelomic epithelium via an epithelial-to-mesenchymal transition, which then progresses into the steroidogenic fetal zone via both direct and indirect routes. Notably, we find that adrenocortical and gonadal lineages exhibit distinct HOX codes, suggesting distinct anterior-posterior regionalization. Together, our assessment of the early divergence of these lineages provides a molecular framework for understanding human adrenal and gonadal disorders.

The X chromosome dosage compensation program during the development of cynomolgus monkeys

[Figure: see text].

The Natural History of Spontaneously Occurred Endometriosis in Cynomolgus Monkeys by Monthly Follow-Up Laparoscopy for Two Years

Endometriosis, a disease in which endometrial tissue proliferates outside the uterus, is a progressive disease that affects women in reproductive age. It causes abdominal pain and infertility that severely affects the quality of life in young women. The mechanism of the onset and development of endometriosis has not been fully elucidated because of the complex mechanism involved in the disease. Nonhuman primates have been used to study the pathogenesis of spontaneous endometriosis because of their gynecological and anatomical similarities to humans. To reveal the natural history of endometriosis in cynomolgus monkeys, we selected 11 female cynomolgus monkeys with spontaneous endometriosis and performed monthly laparoscopies, mapping endometriotic lesions and adhesions up to two years. At the initial laparoscopy, endometriotic lesions were exclusively found in the vesicouterine pouch in 45.4% (5/11) of the monkeys and spread to the Douglas' pouch over time. Appearance of small de novo lesions and disappearance of some of the small lesions were observed in 100% (11/11) and 18.2% (2/11) of the monkeys, respectively. Endometriosis developed in all monkeys, and the speed of progression varied greatly among individuals that could be attributed to the degree or frequency of retrograde menstruation and genetic factors; these findings support the similarities between humans and monkeys, thus verifying the value of this nonhuman primate model. Finding reliable quantification markers and unravelling the underlying factors in correlation with the spatiotemporal development of the disease using a nonhuman primate model would be useful for the better management of endometriosis in humans.

Generation of Transgenic Cynomolgus Monkeys Overexpressing the Gene for Amyloid-β Precursor Protein

Alzheimer’s disease (AD) is the most common cause of dementia and understanding its pathogenesis should lead to improved therapeutic and diagnostic methods. Although several groups have developed transgenic mouse models overexpressing the human amyloid-β precursor protein (APP) gene with AD mutations, with and without presenilin mutations, as well as APP gene knock-in mouse models, these animals display amyloid pathology but do not show neurofibrillary tangles or neuronal loss. This presumably is due to differences between the etiology of the aged-related human disease and the mouse models. Here we report the generation of two transgenic cynomolgus monkeys overexpressing the human gene for APP with Swedish, Artic, and Iberian mutations, and demonstrated expression of gene tagged green fluorescent protein marker in the placenta, amnion, hair follicles, and peripheral blood. We believe that these nonhuman primate models will be very useful to study the pathogenesis of dementia and AD. However, generated Tg monkeys still have some limitations. We employed the CAG promoter, which will promote gene expression in a non-tissue specific manner. Moreover, we used transgenic models but not knock-in models. Thus, the inserted transgene destroys endogenous gene(s) and may affect the phenotype(s). Nevertheless, it will be of great interest to determine whether these Tg monkeys will develop tauopathy and neurodegeneration similar to human AD.

The embryonic ontogeny of the gonadal somatic cells in mice and monkeys

In the early fetal stage, the gonads are bipotent and only later become the ovary or testis, depending on the genetic sex. Despite many studies examining how sex determination occurs from biopotential gonads, the spatial and temporal organization of bipotential gonads and their progenitors is poorly understood. Here, using lineage tracing in mice, we find that the gonads originate from a T⁺ primitive streak through WT1⁺ posterior intermediate mesoderm and appear to share origins anteriorly with the adrenal glands and posteriorly with the metanephric mesenchyme. Comparative single-cell transcriptomic analyses in mouse and cynomolgus monkey embryos reveal the convergence of the lineage trajectory and genetic programs accompanying the specification of biopotential gonadal progenitor cells. This process involves sustained expression of epithelial genes and upregulation of mesenchymal genes, thereby conferring an epithelial-mesenchymal hybrid state. Our study provides key resources for understanding early gonadogenesis in mice and primates.

Capturing human trophoblast development with naive pluripotent stem cells in vitro

Trophoblasts are extraembryonic cells that are essential for maintaining pregnancy. Human trophoblasts arise from the morula as trophectoderm (TE), which, after implantation, differentiates into cytotrophoblasts (CTs), syncytiotrophoblasts (STs), and extravillous trophoblasts (EVTs), composing the placenta. Here we show that naïve, but not primed, human pluripotent stem cells (PSCs) recapitulate trophoblast development. Naive PSC-derived TE and CTs (nCTs) recreated human and monkey TE-to-CT transition. nCTs self-renewed as CT stem cells and had the characteristics of proliferating villous CTs and CTs in the cell column of the first trimester. Notably, although primed PSCs differentiated into trophoblast-like cells (BMP4, A83-01, and PD173074 [BAP]-treated primed PSCs [pBAPs]), pBAPs were distinct from nCTs and human placenta-derived CT stem cells, exhibiting properties consistent with the amnion. Our findings establish an authentic paradigm for human trophoblast development, demonstrating the invaluable properties of naive human PSCs. Our system provides a platform to study the molecular mechanisms underlying trophoblast development and related diseases.

GATA transcription factors, SOX17 and TFAP2C, drive the human germ-cell specification program

This work shows that GATA transcription factors transduce the BMP signaling and, with SOX17 and TFAP2C, induce the human germ-cell fate, delineating the mechanism for human germ-cell specification.

The in vitro reconstitution of human germ-cell development provides a robust framework for clarifying key underlying mechanisms. Here, we explored transcription factors (TFs) that engender the germ-cell fate in their pluripotent precursors. Unexpectedly, SOX17, TFAP2C, and BLIMP1, which act under the BMP signaling and are indispensable for human primordial germ-cell-like cell (hPGCLC) specification, failed to induce hPGCLCs. In contrast, GATA3 or GATA2, immediate BMP effectors, combined with SOX17 and TFAP2C, generated hPGCLCs. GATA3/GATA2 knockouts dose-dependently impaired BMP-induced hPGCLC specification, whereas GATA3/GATA2 expression remained unaffected in SOX17, TFAP2C, or BLIMP1 knockouts. In cynomolgus monkeys, a key model for human development, GATA3, SOX17, and TFAP2C were co-expressed exclusively in early PGCs. Crucially, the TF-induced hPGCLCs acquired a hallmark of bona fide hPGCs to undergo epigenetic reprogramming and mature into oogonia/gonocytes in xenogeneic reconstituted ovaries. By uncovering a TF circuitry driving the germ line program, our study provides a paradigm for TF-based human gametogenesis.

First Successful Delivery after Uterus Transplantation in MHC-Defined Cynomolgus Macaques

Delivery following uterus transplantation (UTx)—an approach for treating uterine factor infertility—has not been reported in nonhuman primate models. Here, six female major histocompatibility complex (MHC)-defined cynomolgus macaques that underwent allogeneic UTx were evaluated. Antithymocyte globulin and rituximab were administered to induce immunosuppression and a triple maintenance regimen was used. Menstruation resumed in all animals with long-term survival, except one, which was euthanized due to infusion associated adverse reaction to antithymocyte globulin. Donor-specific antibodies (DSA) were detected in cases 2, 4, and 5, while humoral rejection occurred in cases 4 and 5. Post-transplant lymphoproliferative disorder (PTLD) developed in cases 2 and 3. Pregnancy was attempted in cases 1, 2, and 3 but was achieved only in case 2, which had haploidentical donor and recipient MHCs. Pregnancy was achieved in case 2 after recovery from graft rejection coincident with DSA and PTLD. A cesarean section was performed at full-term. This is the first report of a successful livebirth following allogeneic UTx in nonhuman primates, although the delivery was achieved via UTx between a pair carrying haploidentical MHCs. Experimental data from nonhuman primates may provide important scientific knowledge needed to resolve unsolved clinical issues in UTx.

Experimental techniques for the development of a uterus transplantation model in cynomolgus macaques

Uterus transplantation (UTx) is now a treatment for women with uterine factor infertility to have a child. However, UTx is still largely at the experimental stage, and many medical issues remain unsolved. Therefore, adequate studies in large animals including non-human primates are required for validation of these issues. UTx research, especially in non-human primates, can provide important information for its full establishment in humans due to the anatomical and physiological similarities between the two. We accumulated data from UTx studies using cynomolgus macaques since 2009 and established autologous and allogeneic UTx models which led to deliveries after performing the procedure. In this paper, we summarized key points to develop UTx models in cynomolgus macaques based on our experience. UTx models in non-human primates can surely contribute new and beneficial knowledge in this field and can be useful for the further development of UTx in humans.

Clinical features of irreversible rejection after allogeneic uterus transplantation in cynomolgus macaques

Uterus transplantation (UTx) is a potential option for women with uterine factor infertility to have a child. The clinical features indicating irreversible rejection of the uterus are unknown. In our experimental series of allogeneic UTx in cynomolgus macaques, six female macaques were retrospectively examined, which were unresponsive to treatment with immunosuppressants (i.e. irreversible rejection). Clinical features including general condition, hematology, uterine size, indocyanine green (ICG) fluorescence imaging by laparotomy, and histopathological findings of the removed uterus were evaluated. In all cases, general condition was good at the time of diagnosis of irreversible rejection and thereafter. Laboratory evaluation showed temporary increases in white blood cells, lactate dehydrogenase and C-reactive protein, then these levels tended to decrease gradually. In transabdominal ultrasonography, the uterus showed time-dependent shrinkage after transient swelling at the time of diagnosis of irreversible rejection. In laparotomy, a whitish transplanted uterus was observed and enhancement of the transplanted uterus was absent in ICG fluorescence imaging. Histopathological findings in each removed uterus showed hyalinized fibrosis, endometrial deficit, lymphocytic infiltration and vasculitis. These findings suggest that uterine transplantation rejection is not fatal, in contrast to rejection of life-supporting organs. Since the transplanted uterus with irreversible rejection atrophies naturally, hysterectomy may be unnecessary.

Comprehensive evaluation of ubiquitous promoters suitable for the generation of transgenic cynomolgus monkeys†

Nonhuman primates (NHPs) are considered to be the most valuable models for human transgenic (Tg) research into disease because human pathology is more closely recapitulated in NHPs than rodents. Previous studies have reported the generation of Tg NHPs that ubiquitously overexpress a transgene using various promoters, but it is not yet clear which promoter is most suitable for the generation of NHPs overexpressing a transgene ubiquitously and persistently in various tissues. To clarify this issue, we evaluated four putative ubiquitous promoters, cytomegalovirus (CMV) immediate-early enhancer and chicken beta-actin (CAG), elongation factor 1α (EF1α), ubiquitin C (UbC), and CMV, using an in vitro differentiation system of cynomolgus monkey embryonic stem cells (ESCs). While the EF1α promoter drove Tg expression more strongly than the other promoters in undifferentiated pluripotent ESCs, the CAG promoter was more effective in differentiated cells such as embryoid bodies and ESC-derived neurons. When the CAG and EF1α promoters were used to generate green fluorescent protein (GFP)-expressing Tg monkeys, the CAG promoter drove GFP expression in skin and hematopoietic tissues more strongly than in ΕF1α-GFP Tg monkeys. Notably, the EF1α promoter underwent more silencing in both ESCs and Tg monkeys. Thus, the CAG promoter appears to be the most suitable for ubiquitous and stable expression of transgenes in the differentiated tissues of Tg cynomolgus monkeys and appropriate for the establishment of human disease models.

Establishment of macaque trophoblast stem cell lines derived from cynomolgus monkey blastocysts

The placenta forms a maternal-fetal junction that supports many physiological functions such as the supply of nutrition and exchange of gases and wastes. Establishing an in vitro culture model of human and non-human primate trophoblast stem/progenitor cells is important for investigating the process of early placental development and trophoblast differentiation. In this study, we have established five trophoblast stem cell (TSC) lines from cynomolgus monkey blastocysts, named macTSC #1-5. Fibroblast growth factor 4 (FGF4) enhanced proliferation of macTSCs, while other exogenous factors were not required to maintain their undifferentiated state. macTSCs showed a trophoblastic gene expression profile and trophoblast-like DNA methylation status and also exhibited differentiation capacity towards invasive trophoblast cells and multinucleated syncytia. In a xenogeneic chimera assay, these stem cells contributed to trophectoderm (TE) development in the chimeric blastocysts. macTSC are the first primate trophoblast cell lines whose proliferation is promoted by FGF4. These cell lines provide a valuable in vitro culture model to analyze the similarities and differences in placental development between human and non-human primates.

Monkeys mutant for PKD1 recapitulate human autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) caused by PKD1 mutations is one of the most common hereditary disorders. However, the key pathological processes underlying cyst development and exacerbation in pre-symptomatic stages remain unknown, because rodent models do not recapitulate critical disease phenotypes, including disease onset in heterozygotes. Here, using CRISPR/Cas9, we generate ADPKD models with PKD1 mutations in cynomolgus monkeys. As in humans and mice, near-complete PKD1 depletion induces severe cyst formation mainly in collecting ducts. Importantly, unlike in mice, PKD1 heterozygote monkeys exhibit cyst formation perinatally in distal tubules, possibly reflecting the initial pathology in humans. Many monkeys in these models survive after cyst formation, and cysts progress with age. Furthermore, we succeed in generating selective heterozygous mutations using allele-specific targeting. We propose that our models elucidate the onset and progression of ADPKD, which will serve as a critical basis for establishing new therapeutic strategies, including drug treatments.

Long-Term Outcome and Rejection After Allogeneic Uterus Transplantation in Cynomolgus Macaques

Uterus transplantation (UTx) is an option for women with uterine factor infertility to have a child, but is still in the experimental stage. Therefore, allogeneic animal models of UTx are required for resolution of clinical issues. In this study, long-term outcomes were evaluated in four recipients (cases 1-4) after allogeneic UTx in cynomolgus macaques. Immunosuppression with antithymocyte globulin induction and a triple maintenance regimen was used. Postoperative ultrasonography and biopsy of the transplanted uterus and immunoserological examinations were performed. All four recipients survived for >3 months after surgery, but continuous menstruation did not resume, although temporary menstruation occurred (cases 1 and 2). All animals were euthanized due to irreversible rejection and no uterine blood flow (cases 1, 2 and 4) and post-transplant lymphoproliferative disorder (case 3). Donor-specific antibodies against MHC class I and II were detected in cases 1, 2 and 4, but not in case 3. Peripheral lymphocyte counts tended to elevate for CD3⁺, CD20⁺ and NK cells in conjunction with uterine rejection, and all animals had elevated stimulation indexes of mixed lymphocyte reaction after surgery. Establishment of allogeneic UTx in cynomolgus macaque requires further exploration of immunosuppression, but the clinicopathological features of uterine rejection are useful for development of human UTx.

Poor second ovarian stimulation in cynomolgus monkeys (Macaca fascicularis) is associated with the production of antibodies against human follicle-stimulating hormone

Cynomolgus monkeys (Macaca fascicularis) are a valuable model organism for human disease modeling because human physiology and pathology are closer to those of cynomolgus monkeys than rodents. It has been widely reported that mature oocytes can be recovered from cynomolgus monkeys through ovarian stimulation by human follicle-stimulating hormone (hFSH). However, it is unknown whether mature oocytes can be effectively obtained through a second ovarian stimulation by hFSH. Here, we report that some ovaries (eight ovaries from 14 female monkeys) were stimulated effectively by hFSH even after the first ovum pick up, whereas the others were stimulated poorly by hFSH. Furthermore, we found antibodies against hFSH only in the serum of female monkeys with poorly stimulated ovaries. Collectively, these data suggest that anti-hFSH antibodies in serum may cause a poor ovarian response to hFSH stimulation. Finally, detection of such antibodies as well as observation of the ovary over the course of hFSH administration might be useful to predict favorable second ovarian stimulation by hFSH.

Single-cell transcriptome of early embryos and cultured embryonic stem cells of cynomolgus monkeys

In mammals, the development of pluripotency and specification of primordial germ cells (PGCs) have been studied predominantly using mice as a model organism. However, divergences among mammalian species for such processes have begun to be recognized. Between humans and mice, pre-implantation development appears relatively similar, but the manner and morphology of post-implantation development are significantly different. Nevertheless, the embryogenesis just after implantation in primates, including the specification of PGCs, has been unexplored due to the difficulties in analyzing the embryos at relevant developmental stages. Here, we present a comprehensive single-cell transcriptome dataset of pre- and early post-implantation embryo cells, PGCs and embryonic stem cells (ESCs) of cynomolgus monkeys as a model of higher primates. The identities of each transcriptome were also validated rigorously by other way such as immunofluorescent analysis. The information reported here will serve as a foundation for our understanding of a wide range of processes in the developmental biology of primates, including humans.

The Germ Cell Fate of Cynomolgus Monkeys Is Specified in the Nascent Amnion

The germ cell lineage ensures reproduction and heredity. The mechanism for germ cell specification in primates, including humans, has remained unknown. In primates, upon implantation the pluripotent epiblast segregates the amnion, an extra-embryonic membrane eventually ensheathing an embryo, and thereafter initiates gastrulation to generate three germ layers. Here, we show that in cynomolgus monkeys, the SOX17/TFAP2C/BLIMP1-positive primordial germ cells (cyPGCs) originate from the dorsal amnion at embryonic day 11 (E11) prior to gastrulation. cyPGCs appear to migrate down the amnion and, through proliferation and recruitment from the posterior amnion, expand in number around the posterior yolk sac by E17. Remarkably, the amnion itself expresses BMP4 and WNT3A, cytokines potentially critical for cyPGC specification, and responds primarily to them. Moreover, human PGC-like cells in vitro exhibit a transcriptome similar to cyPGCs just after specification. Our study identifies the origin of PGCs and a unique function of the nascent amnion in primates.

Generation of transgenic cynomolgus monkeys that express green fluorescent protein throughout the whole body

Nonhuman primates are valuable for human disease modelling, because rodents poorly recapitulate some human diseases such as Parkinson’s disease and Alzheimer’s disease amongst others. Here, we report for the first time, the generation of green fluorescent protein (GFP) transgenic cynomolgus monkeys by lentivirus infection. Our data show that the use of a human cytomegalovirus immediate-early enhancer and chicken beta actin promoter (CAG) directed the ubiquitous expression of the transgene in cynomolgus monkeys. We also found that injection into mature oocytes before fertilization achieved homogenous expression of GFP in each tissue, including the amnion, and fibroblasts, whereas injection into fertilized oocytes generated a transgenic cynomolgus monkey with mosaic GFP expression. Thus, the injection timing was important to create transgenic cynomolgus monkeys that expressed GFP homogenously in each of the various tissues. The strategy established in this work will be useful for the generation of transgenic cynomolgus monkeys for transplantation studies as well as biomedical research.

Robust In Vitro Induction of Human Germ Cell Fate from Pluripotent Stem Cells

Mechanisms underlying human germ cell development are unclear, partly due to difficulties in studying human embryos and lack of suitable experimental systems. Here, we show that human induced pluripotent stem cells (hiPSCs) differentiate into incipient mesoderm-like cells (iMeLCs), which robustly generate human primordial germ cell-like cells (hPGCLCs) that can be purified using the surface markers EpCAM and INTEGRINα6. The transcriptomes of hPGCLCs and primordial germ cells (PGCs) isolated from non-human primates are similar, and although specification of hPGCLCs and mouse PGCs rely on similar signaling pathways, hPGCLC specification transcriptionally activates germline fate without transiently inducing eminent somatic programs. This includes genes important for naive pluripotency and repression of key epigenetic modifiers, concomitant with epigenetic reprogramming. Accordingly, BLIMP1, which represses somatic programs in mice, activates and stabilizes a germline transcriptional circuit and represses a default neuronal differentiation program. Together, these findings provide a foundation for understanding and reconstituting human germ cell development in vitro.

Triplet pregnancy in a cynomolgus monkey (Macaca fascicularis) after double embryo transfer

At our research center, cynomolgus monkeys (Macaca fascicularis) are bred by mating or intracytoplasmic sperm injection (ICSI) and embryo transfer. We typically transfer 2 embryos, because the pregnancy rate is better than that for single embryo transfer. In the case we present here, 2 embryos that had been frozen and thawed after ICSI were transplanted into a recipient female macaque, and a multiple pregnancy (3 fetuses) was confirmed. All 3 fetuses were miscarried between days 81 and 85 of pregnancy. One fetus, which was wrapped in the amnion, was expelled along with its own placenta and one other. Because the other placenta had 2 umbilical arteries, 2 fetuses may have shared it. Therefore, we believe this pregnancy was a case of triplets, including a set of twins from an embryo that divided after transfer.

220 NONHUMAN PRIMATE EMBRYONIC STEM CELLS SIMILAR TO THE BIOLOGICAL PROPERTIES OF MOUSE EMBRYONIC STEM CELLS

Human and mouse embryonic stem (ES) cells are derived from the inner cell mass of preimplantation blastocysts and human ES cells were long thought to be equivalent to mouse ES cells, despite clear morphological difference and different signalling pathways to maintain their pluripotency between these two ES cell types. Mouse ES cells depend on leukemia inhibitory factor (LIF) and bone morphogenic protein 4 (BMP4) signalling, whereas their human counterparts rely on basic fibroblast growth factor (bFGF) and activin A signalling. The biggest difference of two ES cells is the ability of chimera formation and mouse ES cells can contribute chimera but primate ES cells fails to do that. Monkey ES cells in primates only can be tested for chimera formation in vivo due to the ethical issue and cynomolgus monkey is the most common nonhuman primate to be used for the safety study of drug discoveries. The objective of this study was to develop novel cynomolgus monkey ES cells that have similar biological properties with mouse ES cell and our ultimate goal is to establish germline competent nonhuman primate ES cells. Ovarian stimulation and oocyte collection were carried out for the derivation of ES cells as previously described by Torii et al. Briefly, GnRH (0.9 mg/head) was administered to cynomolgus monkey and two weeks later, a micro infusion pump (iPRECIO™, Primetech Corp) contains FSH was implanted subcutaneously. Follicular aspiration was then performed 40 h after hCG injection and metaphase II oocytes were fertilized by intracytoplasmic sperm injection (ICSI). Cynomolgus monkey ES cells were then established under mouse ES cell conditions such as LIF/STAT signalling and a dome tree-dimensional (3D) morphology nonhuman primate ES cells were selected. On the other hands, ES cells that were established with the presence of basic FGF showed conventional layer-type morphology. Dome-type ES cells express pluripotent transcriptional factors such as Oct-3/4, Nonog and Sox2 as same as layer-type ES cells and both ES lines were capable of multilineage differentiations in vitro after embryoid body formation. Dome-type nonhuman ES cells can also form teratomas and differentiated into all three germ layers when grafted into immunodeficiency mice. For fluorescent gene delivery to nonhuman primate ES cells, feeder-free condition was applied and CAG-GFP vector was transfected into ES cells using Neon electroporation system (Invitrogen Inc.) for the tracing ES cells in the transplantation study. In this study, we have established dome-type ES cell lines that similar to mouse ES cells in morphology and signalling pathway. Dome-type nonhuman primate ES cells express pluripotent gene markers and prove their pluripotency both of in vitro and in vivo, in addition, these modifications would be important to create germline competent ES cells.

114 LIVE-CELL IMAGING FOR THE QUALITY ASSESSMENT OF INTRACYTOPLASMIC SPERM INJECTION EMBRYO IN CYNOMOLGUS MONKEY

We have developed a live-cell imaging technique to assess measures of embryo quality such as epigenetic status and chromosome integrity during the early cleavage stages of pre-implantation development in the mouse. The advantages of this method are that the procedure is safe for the embryo and pups are not transgenic even after the imaging (Yamagata et al. 2009 Hum. Reprod. 24, 2490–2499). One of the valuable indexes in using this imaging technique is chromosome segregation (CS) during first mitosis; the embryos showing normal CS (NCS) result in normal offspring, whereas abnormal CS (ACS) embryos do not. In this study, we established a live-cell imaging technique for cynomolgus monkey intracytoplasmic sperm injection (ICSI) embryos and we succeeded in obtaining a normal offspring from NCS embryos after the assessment of live-cell imaging. Ovarian stimulation was carried out as previously described by Torii et al. (2001 Exp. Anim. 50, 259). Oocytes were collected by follicular aspiration using laparoscopy and ICSI was performed to metaphase II oocytes. After the ICSI, a mixture of mRNA encoding fluorescent labelled tubulin and histone was injected into ICSI embryos for the evaluation. Live-cell imaging was initiated 4 h after injection by laser confocal microscopy and 2-cell embryos were classified as NCS or ACS the next day. After embryo culture, embryo transfer (ET) was carried out to recipient donors (NCS embryos: 13, ACS embryos: 2) and pregnancy was diagnosed by ultrasonography at 4 weeks after ET. In another experiment, we tried to assess the 2-cell embryos with a snapshot image taken by a conventional fluorescent microscope as a simplified method. A total 121 embryos from 15 monkeys were analysed and embryos were classified as NCS or ACS. Live-cell imaging revealed that the NCS rate was 43.3% and the ACS rate was 56.7%. Pregnancy was confirmed in 2 NCS embryos from 13 ET (15.4%; 2/13); however, no pregnancy was observed in the ACS group (0%, 0/2). Furthermore, one normal offspring was achieved from ET of 2 NCS embryos that were diagnosed by live-cell imaging. In addition, we could also assess the status of chromosome and nuclei in the 2-cell embryos even by fluorescent microscopy and in this case, the NCS rate was 69.2% and the ACS rate was 30.8%. In conclusion, live-cell imaging can be used to evaluate the status of chromosome segregation of ICSI embryos in the cynomolgus monkey under laser confocal and fluorescent microcopy. The results indicate that ACS would be a detrimental factor in the embryonic development in the monkey, similar to in the mouse. Moreover, a normal offspring was born after the imaging and therefore this new technique could be applicable to assessment of embryo quality in human assisted reproductive technology.

127 OVARIAN STIMULATION IN CYNOMOLGUS MONKEYS BY A CONTROLLED RELEASE OF FOLLICULAR-STIMULATING HORMONE UTILIZING A MICRO-INFUSION PUMP

We have established an indoor artificial breeding system for the cynomolgus monkey in an effort to increase the number of MII oocytes that are required for enhanced reproductive efficiency. A conventional ovarian stimulus method requires FSH to be administered to monkeys intramuscularly once a day for 9 days. Recently, a novel implantable and programmable micro-infusion pump (iPRECIO™, Primetech Corp, Tokyo, Japan) has been introduced for small laboratory animals to infuse fluids continuously for long periods of time in vivo. We adapted this micro-infusion pump to administer FSH to cynomolgus monkeys. In this study, we optimized the controlled-release program of FSH for the appropriate ovarian stimulation. First, laparoscopic evaluation was performed to identify animals that had small, underdeveloped follicles and gonadotropin-releasing hormone (0.9 mg animal–1; Leuplin, Takeda, Osaka, Japan) was administered to all selected animals. Two weeks later, iPRECIO™ containing FSH (Gonapure, ASKA, Tokyo, Japan) was implanted subcutaneously and the continuous infusion was started at 15.0 IU kg–1 per day. Five days after implantation, follicular development was evaluated by laparoscopy and the infusion rate was adjusted based on follicular profile (high level: reduced to 12.5 IU kg–1 per day, n = 11; middle level: maintained at 15.0 IU kg–1 per day, n = 47; low level: increased to 20.0 IU kg–1 per day, n = 30). Four days later, hCG (400 IU kg–1, IM) was administered and follicular aspiration was performed 40 h later. In the control group (n = 6), FSH (25.0 IU kg–1 per day) was injected intramuscularly once a day for 9 days, followed by an hCG injection. Oocytes were collected and evaluated and MII oocytes were fertilized by intracytoplasmic sperm injection. Injected oocytes were cultured for 7 days in CRML-1066 medium supplemented with 20% bovine serum at 38°C, with 5% CO2 and 5% O2 in air and blastocyst development was evaluated. Data were analysed by a two-sided t-test. All animals treated with the controlled-release FSH using iPRECIO™ showed significantly higher MII maturation rates (mean: 59.4%, 22/37; P < 0.05) than those of the control group (MII rate: 46.3%, 19/41); however, there was no significant difference among the different FSH release programs. Blastocyst development rates of the test group were also significantly higher than those of the control group (test: 52.0%, control: 28.1%; P < 0.05); however, there was no significant difference among the different FSH programs. This controlled-release system did not require daily injections to the animal, which would be beneficial for decreasing stress. Further, the required dose of FSH using iPRECIO™ was much less than that of the conventional multiple-injection method. These results indicated that controlled release of FSH utilising an iPRECIO™ pump can be customized based on follicular profile and has financial and animal care advantages compared with the conventional method.

39 CLONAL OFFSPRING DERIVED FROM SEPARATED BLASTOMERES IN CYNOMOLGUS MONKEYS (MACACA FASCICULARIS)

There are no reports of cloning by embryo splitting in the cynomolgus monkey, but production of genetically identical monkeys would have tremendous implications for biomedical research, especially for immunological studies, production of disease models, and behavioral science. Cloning would also reduce the number of animals required for the above research by increasing experimental reproducibility. In this study, we tried to produce cynomolgus monkey offspring by embryo splitting and embryo transfer. Controlled ovarian stimulation and oocyte recovery have been previously described by Torii et al. (2000 Primates 41, 39–47). Cumulus-free mature oocytes were fertilized by intracytoplasmic sperm injection. Single spermatozoa were individually immobilized by scoring their tails and picking them up with the injection pipette. The denuded oocyte was held by the holding pipette with the polar body in the 12 o'clock position. The injection pipette was then inserted at the 3 o'clock position and was introduced into the cytoplasm, breaking the ooplasmic membrane by pulling gently. One spermatozoon was injected into the cytoplasm. The injected oocytes were cultured at 38�C in 5% CO2, 5% O2 and 90% N2 in CMRL-1066 medium (Invitrogen, Grand Island, NY, USA) containing 20% calf serum (CS, Invitrogen) for 2–3 days. Splitting was performed using 4- to 7-cell-stage embryos. The zona pellucida was disrupted with acidic Tyrode's solution, and individual blastomeres were separated from the zona-free embryos by 0.25% trypsin-EDTA with added CaCl2 (<1 min). After transferring the zona-free embryos into TALP-HEPES medium, blastomeres were dissociated by pipetting with a 40–50 µm micropipette 4–5 times. These blastomeres were then transferred into empty zonae that had been produced from immature oocytes by the aspiration of ooplasm with a micromanipulator. Sixteen embryos underwent blastomere separation and a total of 33 split embryos were produced. After being cultured for 2–3 h in CMRL-1066 medium containing 20% CS, 30 of these split embryos, comprising 1–4 blastomeres each, were transferred into the oviducts of 23 fertile surrogate mothers at 0 to 5 days after ovulation. Pregnancy was confirmed in two animals (8.7%; 2/23) by ultrasound approximately 30 days after transfer. The pregnancies were uneventful and two normal healthy babies were born without any assistance 159 days after transfer. The low pregnancy rate could be due to the presence of fewer cells in the smaller split embryos, the ruptured zona pellucida, or the in vitro micromanipulation of embryos during blastomere separation and reconstruction. Here we report the first production of viable cloned offspring produced by blastomere separation in the cynomolgus monkey. Since we have previously succeeded in establishing ES cell lines from isolated blastomeres, in the future we will be able to produce genetically identical monkeys from a single 4- to 8-cell-stage embryo using those ES cell lines and the embryo splitting technique.

256 EFFECT OF EPIDERMAL GROWTH FACTOR ON IN VITRO MATURATION OF CYNOMOLGUS MONKEY (MACACA FASCICULARIS) OOCYTES

Collected oocytes include not only mature oocytes (metaphase II: MII), but also immature oocytes (germinal vesicle: GV, and metaphase I: MI). To establish a dependable artificial indoor breeding program in cynomolgus monkeys, we are planning to carry out in vitro maturation (IVM) using GV and MI oocytes. In this study, we attempted to determine whether different types of feeder layers and epidermal growth factor (EGF) were effective for IVM. Cumulus–oocyte complexes (COCs) were collected from ovaries of 4–10-year-old female cynomolgus monkeys stimulated by the combination of FSH (25 IU kg–1 × 9 days) and hCG (400 IU kg–1) (Torii 2000 Primates 39, 399–406). Oocytes were classified by morphological features: oocytes retaining an intact germinal vesicle nucleus (GV); oocytes that had undergone germinal vesicle breakdown without polar body formation (MI); and oocytes with a first polar body (MII). GV and MI oocytes were co-cultured on monkey cumulus cells (MCC), monkey follicular ovarian cells (MFOC), monkey oviductal cells (MOC), or human solubilized amnion product (HSAP), with TCM-199+10% fetal bovine serum containing epidermal growth factor (EGF; 10 ng mL–1 or 20 ng mL–1). The maturation rate from GV to MII oocytes was 6.7% (MCC), 18.0% (MFOC), 35.7% (MOC), and 28.6% (HSAP) (Table 1). Although higher maturity was observed in MOC and HSAP, the effect of EGF was not found in co-cultures using any feeder layers. The maturation rate from MI to MII oocytes was 33.3% (MCC), 27.8% (MFOC), 55.6% (MOC), and 44.0% (HSAP) (Table 1). The highest maturation rate from GV and MI was observed in co-cultures using MOC. The maturation rate from MI to MII oocytes in the presence of 10 ng mL–1 EGF was 75.0% (MCC) and 73.7% (HSAP) (Table 1), whereas the rate in the presence of 20 ng mL–1 EGF was 59.1% (MCC), 64.3% (MFOC), 92.3% (MOC), and 60.0% (HSAP) (Table 1). Thus, the best maturation rate was a co-culture using MOC as a feeder layer with 20 ng mL–1 EGF. According to our results, maturation rate during IVM depends on the cellular type of feeder layers and the concentration of EGF. EGF is especially effective for maturity from MI to MII oocytes, but not from GV to MI or MII oocytes. Thus, IVM should be carred out under optimal culture conditions, including suitable feeder layer and media plus supplements. In the future, it is important that intracytoplasmic sperm injection be carried out using in vitro-matured MII oocytes for establishment of an artificial indoor breeding program in cynomolgus monkeys. Table 1. Number of matured oocytes co-cultured with different feeder layers and EGF

60 INFLUENCE OF HOECHST STAINING FOR NUCLEAR TRANSFER ON PARTHENOGENETIC EMBRYOS IN CYNOMOLGUS MONKEYS (MACACA FASCICULARIS)

Nonhuman primates are valuable animal models for the study of human diseases, and somatic cell nuclear transfer (SCNT) is an important method for establishing tailor-made embryonic stem (ES) cells and transgenic animals in these model species. However, there have been few reports on SCNT in nonhuman primates. Moreover, the development of cloned blastocysts could be influenced by any chemical reagents and manipulations used in this technique. In this study we compared blastocyst developmental rates with and without Hoechst staining. Metaphase II (MII) oocytes were collected from hormone-treated adult female cynomolgus monkeys (Macaca fascicularis) under laparoscopic observation (Torii et al. 2000 Primates 41, 39–47). A pseudo-SCNT procedure, which consisted of cytochalasin B treatment, cytoplasm removal, and dissection of the oocyte membrane, was performed on MII oocytes either in the presence of (Experiment 1; Ex1) or in the absence of Hoechst 33342 (Experiment 2; Ex2). Hoffman modulation contrast microscopy was used in Ex1 and Nomarski differential interference contrast (DIC) was used in Ex2. In Ex1, cumulus-free MII oocytes were treated with Hoechst 33342 (5 mg mL–1; Sigma Chemical Co., St. Louis, MO, USA) for 5 min and the following pseudo-SCNT procedure was carried out: cytochalasin B (CB, 5 µg mL–1; Sigma) for 20 min, removal of a small amount of cytoplasm (pseudo-EN), and then dissection of the oocyte cytoplasmic membrane (pseudo-IN) under Hoffman modulation contrast microscopy. In Ex2, CB treatment, pseudo-EN, and pseudo-IN were performed under Nomarski DIC microscopy. After treatment, these oocytes were activated by parthenogenetic stimulation. Parthenogenesis was induced by 5-m ionomycin (Sigma) for 2 min and 2 mm 6-dimethylaminopurine (Sigma) for 4 h. As a control, cumulus-free MII oocytes were activated by only parthenogenetic stimulation, without the above manipulations. These activated oocytes were cultured in CMRL-1066 medium containing 20% calf serum at 38�C in 5% CO2, 5% O2, and 90% N2 for 7–8 days. The rates of development to blastocyst stage were 14% (1/7) in Ex1, 30% (3/10) in Ex2, and 29% (2/7) in the control. The developmental rate of parthenotes to the blastocyst stage in Ex2 was greater than that in Ex1 and similar to the control. These results suggest that treatment of cynomolgus monkey oocytes with Hoechst staining possibily decreases development to the blastocyst stage. Therefore, enucleation under Nomarski DIC will be a good alternative to Hoechst staining and could improve the potential development of nonhuman primate SCNT embryos.

290 A CYNOMOLGUS MONKEY EMBRYONIC STEM CELL LINE DERIVED FROM A SINGLE BLASTOMERE

The establishment of most embryonic stem (ES) cell lines requires the destruction of embryos. Some ES cell lines in mice and humans are currently derived from a single blastomere, so that remaining blastomeres can still develop into fetuses. However, the procedures currently in use for establishing these lines are very complicated, and other ES cell lines from the same species are needed (Chung et al. 2006 Nature 439, 216–219; Klimanskaya et al. 2006 Nature 444, 481–485). The objective of this study was to devise a method simpler than those previously described for establishing ES cell lines from a single blastomere in the cynomolgus monkey. Controlled ovarian stimulation and oocyte recovery have been described previously by Torii et al. (2000 Primates 41, 39–47). Cumulus-free mature oocytes were fertilized by intracytoplasmic sperm injection (ICSI), and then cultured at 38�C in 5% CO2, 5% O2 for 2 days. The zona pellucida of 4- to 5-cell-stage embryos was disrupted using acidic Tyrode's solution, and individual blastomeres were separated from the denuded embryos using trypsin. These blastomeres were cultured on mitomycin-C-treated mouse embryonic fibroblasts and ES medium containing adrenocorticotropic hormone (ACTH) (Ogawa et al. 2004 Genes to Cells 9, 471–477). After the formation of initial outgrowths, half of the medium was changed every other day until the outgrowths reached approximately 100 cells. Passage of putative monkey ES cells was performed by mechanical dispersion of the colonies and transfer to fresh feeders every 3–4 days until there were enough cells for enzymatic dispersion. One stable ES cell line was obtained from two 4- or 5-cell-stage embryos using ES medium containing ACTH. The morphology of this ES cell colony was consistent with the monkey ES cell colony previous described by Suemori et al. (2001 Dev. Dynamics 222, 273–279). The ES cell line was passaged more than 17 times, and the morphology of the ES cell colony did not differ between the first and seventeenth passages. The ES cells showed normal karyotype and retained pluripotency markers for primate ES cells including octamer-binding protein 4 (Oct-4), stage-specific embryonic antigen (SSEA)-4, tumor-rejection antigen (TRA)-1-60, and TRA-1-81. We are presently confirming whether this ES cell line possesses potencies to differentiate in all three embryonic germ layers using both an in vitro assay and teratoma formation. Here we showed that cynomolgus monkey ES cells can be derived from a single blastomere, without co-culturing another ES cell line, as has been done in previous studies on mice and humans. This method allows the establishment of ES cell lines from a single blastomere, leaving the other blastomeres available for embryo transfer. Thus, the method described here is simpler than previously described methods and alleviates some ethical concerns.

155 LAPAROSCOPIC EVALUATION OF OVARIAN REACTION TO HORMONE STIMULATION IN CYNOMOLGUS MONKEYS (MACACA FASCICULARIS)

Oocyte collection is a key step to development of a system for modeling human regenerative medicine and assisted reproductive technology in cynomolgus monkeys (Macaca fascicularis), but collecting oocytes at a suitable developmental stage (metaphase II) is difficult. Metaphase II (MII) oocytes can be collected from cynomolgus ovaries stimulated by hormone injection. In this study, we developed a useful method for collecting a large number of MII oocytes by monitoring the morphology and size of ovaries with laparoscopic observation. Controlled ovarian stimulation and oocyte recovery in mature cynomolgus monkeys have been previously described by Torii et al. (2000 Biochemistry 39, 3197–3205). Beginning at menses, levels of estrogens were down-regulated by the subcutaneous injection of a GnRH antagonist (Leuplin, 0.9 mg animal-1; Takeda Chemical Industries, Ltd., Osaka, Japan). Two weeks later, human follicle stimulating hormone (FSH, Fertinorm, 25 IU kg-1; Serono, Canton Zug, Switzerland) was administered for 9 days. On the day after that of the last FSH administration, human chorionic gonadotropin (hCG, Puberogen, 400 IU kg-1; Sankyo Co., Ltd., Tokyo, Japan) was intramuscularly injected. Follicular aspiration was performed at 404-41 hours post-hCG injection. Oocyte collection was monitored using a 3-mm laparoscope attached to a video system. Oocytes were aspirated from the follicles using a 20-guage needle. Follicle development of the ovary was rated morphologically as A (small follicles), B (many small follicles), or C (many large follicles), and size relative to the uterus was rated as 1 (no response), 2 (smaller), 3 (equal), or 4 (larger) at oocyte collection. Regarding morphology, the highest ratio of MII/total oocytes was obtained from B–C ovaries (rating of 2 ovaries, one each left or right with a rating of B or C, n = 8, 26.9 � 22.4, 70.7%), followed by B–B (n = 21, 19.5 � 14.3, 55.9%), and C–C (n = 19, 10.6 � 5.8, 51.9%). No MII oocytes were collected from A–A (n = 1, 0%) ovaries. Ovaries appeared to be over-stimulated in the ovaries rated C–C but under-stimulated in B–B. Regarding ovary size, the highest ratio of MII/total oocytes was obtained from 4–4 (both ovaries with rating of 4, n = 10, 21.9 � 11.2, 68.8%), followed by 3–3 (n = 21, 19.1 � 14.3, 58.2%), and 2–2 (n = 9, 11.6 � 6.5, 53.3%). No MII oocytes were collected from 1–1 ovaries (n = 1, 0%). The number of MII oocytes collected was directly related to ovary size: more MII oocytes were collected from larger ovaries. These data demonstrate that the number of oocytes collected is directly related to ovary size. Our results suggest that the ratio of MII oocytes can be predicted by the morphology and the size of ovaries. In addition, we found that ovarian development can be controlled by adjusting FSH dosage. Therefore, laparoscopic observation of ovaries during FSH treatment and adjusting FSH dosage are necessary to collect MII oocytes efficiently.