The timing and mechanisms of mitochondrial DNA (mtDNA) segregation and transmission in mammals are poorly understood. Genetic bottleneck in female germ cells has been proposed as the main phenomenon responsible for rapid intergenerational segregation of heteroplasmic mtDNA. We demonstrate here that mtDNA segregation occurs during primate preimplantation embryogenesis resulting in partitioning of mtDNA variants between daughter blastomeres. A substantial shift toward homoplasmy occurred in fetuses and embryonic stem cells (ESCs) derived from these heteroplasmic embryos. We also observed a wide range of heteroplasmic mtDNA variants distributed in individual oocytes recovered from these fetuses. Thus, we present here evidence for a previously unknown mtDNA segregation and bottleneck during preimplantation embryo development, suggesting that return to the homoplasmic condition can occur during development of an individual organism from the zygote to birth, without a passage through the germline.

A three-dimensional culture system supports the development of primate preantral follicles to the antral stage with appreciable steroid production. This study assessed i) whether in vitro developmental competence of follicles is age dependent, ii) the role of gonadotropins and insulin in supporting folliculogenesis, and iii) anti-Müllerian hormone (AMH) and vascular endothelial growth factor (VEGF) production by growing follicles. Ovaries were obtained from prepubertal, young, and older adult rhesus macaques. Secondary follicles were encapsulated into alginate beads and cultured individually for 40 days in media containing 0.05 or 5 μg/ml insulin, with or without recombinant human (rh) FSH (500 mIU/ml). No follicles survived in the culture without rhFSH. In the presence of rhFSH, survival was lower for follicles from older animals, whereas growth, i.e. follicle diameter, was less by day 40 for follicles from prepubertal animals. The surviving follicles were categorized as no-grow (NG; ≤250 μm), slow-grow (SG; 250–500 μm), and fast-grow (FG; ≥500 μm) according to their diameters. SG follicles cultured with 5 μg/ml insulin produced more ovarian steroids than those cultured with 0.05 μg/ml insulin by week 5. SG and FG follicles produced more AMH and VEGF than the NG, and levels peaked at weeks 2 and 5 respectively. After 100 ng/ml rh chorionic gonadotropin treatment for 34 h, more healthy oocytes were retrieved from young adults whose follicles were cultured with 5 μg/ml insulin. This culture system offers an opportunity to characterize the endocrine and paracrine function of primate follicles that influence follicle growth and oocyte maturation. Abstract A three-dimensional culture system supports the development of primate preantral follicles to the antral stage with appreciable steroid production. This study assessed i) whether in vitro developmental competence of follicles is age dependent, ii) the role of gonadotropins and insulin in supporting folliculogenesis, and iii) anti-Müllerian hormone (AMH) and vascular endothelial growth factor (VEGF) production by growing follicles. Ovaries were obtained from prepubertal, young, and older adult rhesus macaques. Secondary follicles were encapsulated into alginate beads and cultured individually for 40 days in media containing 0.05 or 5 μg/ml insulin, with or without recombinant human (rh) FSH (500 mIU/ml). No follicles survived in the culture without rhFSH. In the presence of rhFSH, survival was lower for follicles from older animals, whereas growth, i.e. follicle diameter, was less by day 40 for follicles from prepubertal animals. The surviving follicles were categorized as no-grow (NG; ≤250 μm), slow-grow (SG; 250–500 μm), and fast-grow (FG; ≥500 μm) according to their diameters. SG follicles cultured with 5 μg/ml insulin produced more ovarian steroids than those cultured with 0.05 μg/ml insulin by week 5. SG and FG follicles produced more AMH and VEGF than the NG, and levels peaked at weeks 2 and 5 respectively. After 100 ng/ml rh chorionic gonadotropin treatment for 34 h, more healthy oocytes were retrieved from young adults whose follicles were cultured with 5 μg/ml insulin. This culture system offers an opportunity to characterize the endocrine and paracrine function of primate follicles that influence follicle growth and oocyte maturation.

Does fibrin introduced into the extracellular matrix affect the growth and maturation of individual primate follicles during encapsulated three-dimensional (3D) culture? While not altering follicle survival, fibrin–alginate (FIBRIN) improves macaque primary, but not secondary, follicle development during encapsulated 3D culture in terms of growth, steroidogenesis, anti-Müllerian hormone (AMH)/vascular endothelial growth factor (VEGF) production and oocyte maturation. Efforts to grow non-human primate ovarian follicles from the secondary to the antral stage during encapsulated 3D culture have been successful. However, the growth and maturation of primary follicles in vitro has not been reported in primates, especially in chemically defined conditions. In vitro follicle maturation was investigated using the rhesus macaque (Macaca mulatta). Ovaries (n = 7 pairs) were obtained during the early follicular phase of the menstrual cycle (cycle day 1–4). Primary (80–120 µm diameter) and secondary (125–225 µm diameter) follicles were isolated mechanically, randomly assigned to experimental groups, encapsulated into alginate (0.25% w/v) or FIBRIN (25 mg/ml fibrinogen–0.25% alginate) and cultured for 13 and 5 weeks, respectively. Individual follicles were cultured in alpha minimum essential medium supplemented with FSH. Follicle survival and growth were assessed by microscopy. Follicles that reached the antral stage were treated with recombinant hCG. Metaphase II (MII) oocytes were inseminated via ICSI. Follicle morphology was evaluated by hematoxylin and eosin (H&E) staining. Immunohistochemistry was performed for cytochrome P450 family 17 subfamily A polypeptide 1 (CYP17A1) and 19 subfamily A polypeptide 1 (CYP19A1). Culture medium was analyzed for estradiol (E₂) and progesterone by chemiluminescence, androstenedione (A4) by radioimmunoassay, as well as anti-Müllerian hormone (AMH) and vascular endothelial growth factor (VEGF) by enzyme-linked immunosorbent assay. A total of 105 primary and 133 secondary follicles were collected. The presence of fibrin in the alginate matrix had no effect on either primary or secondary follicle survival. Growing primary and secondary follicles formed an antrum at Weeks 9 and 3, respectively. The percentage of growing follicles was higher (P < 0.05) for primary follicles cultured in FIBRIN than alginate at Week 13. The diameters were larger for the growing secondary follicles cultured in alginate than FIBRIN at Week 5 (P < 0.05). H&E staining revealed the typical morphology for small antral follicles. CPY17A1 immunostaining was detected in theca cells, while CYP19A1 was observed in granulosa cells. E₂ increased (P < 0.05) during antrum formation in growing follicles at Week 9 for primary and Week 3 for secondary follicles. AMH levels in medium from growing primary follicles increased (P < 0.05) after Week 4 with peak levels at Weeks 9–11. AMH increased (P < 0.05) in growing secondary follicles at Weeks 3–5. VEGF levels in medium were elevated (P < 0.05) in growing primary follicles at Week 9. VEGF increased (P < 0.05) in medium from growing secondary follicles at Weeks 3–5. E₂, AMH and VEGF production was higher (P < 0.05) in primary follicle culture with FIBRIN than alginate alone. One primary follicle cultured in FIBRIN (1 of 5 follicles harvested) and a secondary follicle cultured in alginate alone (1 of 15 follicles harvested) yielded an MII oocyte. The fertilized oocyte from primary follicle culture arrested without cell division after fertilization, while the oocyte from secondary follicle culture cleaved and reached the morula stage. The study reports on in vitro development and function of individual macaque follicles, that is limited to the interval from the primary and secondary stage to the small antral stage. The findings await translation to human ovarian follicles. The 3D model for primate follicle development offers a unique opportunity to investigate the growth and regulation of primate primary, as well as secondary follicles, and their enclosed oocytes, as they grow to the antral stage by monitoring and manipulating factors or signaling pathways in vitro. Since primate primary follicles, in addition to secondary follicles, can be cultured to the antral stage to provide mature oocytes, they represent an additional source of pre-antral follicles for in vitro follicle maturation with the potential to provide gametes for assisted reproductive technology as an option for fertility preservation in women, including patients with cancer. This work was supported by The Oncofertility Consortium (NIH U54 RR024347-HD058294, PL1-EB008542), NIH U54-HD18185 (Eunice Kennedy Shriver Specialized Cooperative Centers Program in Reproduction and Infertility Research), NIH ORWH/NICHD 2K12HD043488 (BIRCWH), Oregon National Primate Research Center 8P51OD011092. There are no conflicts of interest.

What are the direct effects and physiological role of anti-Müllerian hormone (AMH) during primate follicular development and function at specific stages of folliculogenesis? AMH actions in the primate ovary may be stage-dependent, directly promoting pre-antral follicle growth while inhibiting antral follicle maturation and dominant follicle selection. AMH is expressed in the adult ovary, particularly in developing follicles. Studies in mice suggest that AMH suppresses pre-antral follicle growth in vitro, and inhibits primordial follicle recruitment and FSH-stimulated antral follicle steroidogenesis. For in vitro study, secondary follicles were isolated from ovaries of 12 rhesus macaques and cultured for 5 weeks. For in vivo study, intraovarian infusion was conducted on five monkeys for the entire follicular phase during two spontaneous menstrual cycles. For in vitro study, individual follicles were cultured in a 5% O₂ environment, in alpha minimum essential medium supplemented with recombinant human FSH. Follicles were randomly assigned to treatments of recombinant human AMH protein or neutralizing anti-human AMH antibody (AMH-Ab). Follicle survival, growth, steroid production, steroidogenic enzyme expression, and oocyte maturation were assessed. For in vivo study, ovaries were infused with control vehicle or AMH-Ab during the follicular phase of the menstrual cycle. Cycle length, serum steroid levels, and antral follicle growth were evaluated. AMH exposure during culture weeks 0–3 (pre-antral stage) promoted, while AMH-Ab delayed, antrum formation of growing follicles compared with controls. AMH treatment during culture weeks 3–5 (antral stage) decreased (P < 0.05) estradiol (E2) production, as well as the mRNA expression of cytochrome P450 family 19 subfamily A polypeptide 1, by antral follicles relative to controls, whereas AMH-Ab increased (P < 0.05) follicular mRNA levels of the enzyme. Intraovarian infusion of AMH-Ab during the follicular phase of the menstrual cycle increased (P < 0.05) the average levels of serum E2 compared with those of the control cycles. Three of the five AMH-Ab-treated ovaries displayed multiple (n = 2–9) medium-to-large (2–8 mm) antral follicles at the mid-cycle E2 peak, whereas only one large (4–7 mm) antral follicle was observed in all monkeys during their control cycles. The average levels of serum progesterone were higher (P < 0.05) during the luteal phase of cycles following the AMH-Ab infusion relative to the vehicle infusion. The in vitro study of AMH actions on cultured individual macaque follicles was limited to the interval from the secondary to small antral stage. A sequential study design was used for in vivo experiments, which may limit the power of the study. The current study provides novel information on direct actions and role of AMH during primate follicular development, and selection of a dominant follicle by the late follicular phase of the menstrual cycle. We hypothesize that AMH acts positively on follicular growth during the pre-antral stage in primates, but negatively impacts antral follicle maturation, which is different from what is reported in the mouse model. NIH NICHD R01HD082208, NIH ORWH/NICHD K12HD043488 (BIRCWH), NIH OD P51OD011092 (ONPRC), Collins Medical Trust. There are no conflicts of interest. Not applicable.

Can group culture with stage-specific anti-Müllerian hormone (AMH) modulation support human follicular development and oocyte maturation in vitro? In the presence of FSH, AMH supplementation at the secondary-to-early antral stage followed by AMH depletion promotes the coordinated growth and function of human follicles during group culture, thereby yielding mature oocytes. Stage-specific AMH modulation promotes in-vitro development of nonhuman primate follicles. The group culture method supports nonhuman primate follicle growth from the primary to antral stage, producing developmentally competent oocytes. Ovarian tissue samples were collected from 19 patients of reproductive age (22–47 years old having menstrual cycles) who underwent oophorectomy or hysterectomy for clinical purposes. Tissue pieces were cultured in a matrix-free system for 3 weeks followed by isolation of follicles for the subsequent 6-week individual or group culture. Pieces of ovarian cortical tissue were cultured to support primordial follicle activation and early-stage follicle growth. Secondary follicles isolated from cultured tissue were then randomly assigned to two groups for individual culture: control and AMH modulation, i.e., recombinant human AMH protein supplementation during the secondary-to-early antral stage followed by the addition of neutralizing anti-human AMH antibody. Secondary follicles were also cultured in groups with the same AMH modulation. Follicle survival, growth, steroid hormone and paracrine factor production, steroidogenic protein expression, as well as oocyte maturation and morphology were assessed. Follicles grew to the secondary stage during 3 weeks of ovarian tissue culture. In-vitro-developed follicles expressed AMH and levels of secreted AMH increased (P < 0.05) in the culture media over time. Secondary follicles isolated from cultured ovarian tissue survived and grew to the antral stage during 6 weeks of individual follicle culture. In-vitro-developed antral follicles produced granulosa and theca cell-derived steroid hormones and paracrine factors, which were detectable in the culture media. Germinal vesicle oocytes obtained from cultured follicles exhibited a perinucleolar chromatin rim configuration. AMH modulation did not alter follicle survival or oocyte maturation relative to those of the control follicles. However, follicle diameters, as well as steroid hormone and paracrine factor production, increased (P < 0.05) in the AMH-modulation group compared with the control group. Secondary follicles isolated from cultured ovarian tissue formed aggregates and grew to the antral stage during 6 weeks of group culture. In-vitro-developed antral follicles expressed steroidogenic enzymes and secreted steroid hormones were detectable in the culture media. Oocytes obtained from cultured follicle aggregates with AMH-modulation progressed to the metaphase II stage after IVM, containing a normal-sized first polar body and meiotic spindle. Oocytes exhibited a typical ultrastructure. Follicles were obtained from fresh ovarian tissue of adult patients. Oocyte maturation rates were relatively low and oocytes were assessed by morphological evaluation. Owing to the lack of a control group, the beneficial effects of AMH modulation remained undetermined for the group culture in this study. Stage-specific AMH modulation supports human follicular development in the matrix-free group culture, which is consistent with previously reported AMH actions on growing follicles in nonhuman primates. Oocytes generated by in-vitro-developed follicles achieve meiotic maturation with a typical morphology and ultrastructure, which supports in-vitro follicle maturation as a potential approach for fertility preservation in women. NICHD R01HD082208 and NIH Office of the Director P51OD011092. The authors have no competing interest to declare. N/A.

Negative energy balance during lactation is reflected by low levels of insulin and leptin and is associated with chronic hyperphagia and suppressed GnRH/LH activity. We studied whether restoration of insulin and/or leptin to physiological levels would reverse the lactation-associated hyperphagia, changes in hypothalamic neuropeptide expression [increased neuropeptide Y (NPY) and agouti-related protein (AGRP) and decreased proopiomelanocortin (POMC), kisspeptin (Kiss1), and neurokinin B (NKB)] and suppression of LH. Ovariectomized lactating rats (eight pups) were treated for 48 h with sc minipumps containing saline, human insulin, or rat leptin. The arcuate nucleus (ARH) was analyzed for NPY, AGRP, POMC, Kiss1, and NKB mRNA expression; the dorsal medial hypothalamus (DMH) was analyzed for NPY mRNA. Insulin replacement reversed the increase in ARH NPY/AGRP mRNAs, partially recovered POMC, but had no effect on recovering Kiss1/NKB. Leptin replacement only affected POMC, which was fully recovered. Insulin/leptin dual replacement had similar effects as insulin replacement alone but with a slight increase in Kiss1/NKB. The lactation-induced increase in DMH NPY was unchanged after treatments. Restoration of insulin and/or leptin had no effect on food intake, body weight, serum glucose or serum LH. These results suggest that the negative energy balance of lactation is not required for the hyperphagic drive, although it is involved in the orexigenic changes in the ARH. The chronic hyperphagia of lactation is most likely sustained by the induction of NPY in the DMH. The negative energy balance also does not appear to be a necessary prerequisite for the suppression of GnRH/LH activity.