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Chromosome errors, or aneuploidy, affect an exceptionally high number of human conceptions, causing pregnancy loss and congenital disorders. Here, we have followed chromosome segregation in human oocytes from females aged 9 to 43 years and report that aneuploidy follows a U-curve. Specific segregation error types show different age dependencies, providing a quantitative explanation for the U-curve. Whole-chromosome nondisjunction events are preferentially associated with increased aneuploidy in young girls, whereas centromeric and more extensive cohesion loss limit fertility as women age. Our findings suggest that chromosomal errors originating in oocytes determine the curve of natural fertility in humans.

Purpose The aim of the study was to investigate the maturation rate of immature oocytes collected from ovarian medulla tissue normally discarded during preparation of ovarian cortical tissue for fertility preservation. Further we evaluated survival of derived MII oocytes following vitrification and warming. Methods 36 patients aged from 8 to 41 years who had one ovary excised for fertility preservation were included. Oocytes were collected from the medulla tissue and matured in vitro 44–48 h followed by vitrification. Number of oocytes collected, the rates of maturation and post-warming survival were assessed. Results On average, 11 immature oocytes were collected per patient. The overall maturation rate was 29 % irrespective of whether the ovary was transported 4–5 h on ice or obtained immediately after oophorectomy. The maturation rate in patients below 20 years of age (55 %) was significantly higher than that of patients aged 20–30 years (29 %) and above 30 years (26 %). The post-warming survival rate was 64 %. No significant relationship was observed between the number of collected oocytes and the age of patients. Conclusions Approximately three MII oocytes were obtained per patient following in vitro maturation (IVM) of immature oocytes collected from medulla tissue, of which two survived vitrification and warming. This approach represents an add-on method to potentially augment the fertility opportunity for cancer patients, especially in young women with cancer where transplantation of cortical tissue may pose a risk of relapse, but the IVM approach is currently too inefficient to be the only method used for fertility preservation.

Background The suggested effects of the oocyte secreted GDF9 and BMP15 growth factors on oocyte maturation are currently based on recombinant proteins, and little is known about native GDF9 and BMP15 in humans. Methods Human immature cumulus-oocyte complexes (COCs) obtained in connection with ovarian tissue cryopreservation (OTC) underwent in vitro maturation (IVM). Oocyte-produced GDF9 and BMP15 were detected in COCs using immunofluorescence, and in fresh GV oocytes and in GV and MII oocytes after IVM by western blot. Concentrations of GDF9, BMP15 homodimers, and GDF9/BMP15 heterodimer in spent media after IVM were measured by ELISA. The relative expression of seven genes from the GDF9 and BMP15 signaling pathways ( BMPR2, ALK5, ALK6, SMAD1, SMAD2, SMAD3, and SMAD5 ) was evaluated in fresh cumulus cells (before IVM) and in cumulus cells from GV and MII oocytes after IVM by RT-qPCR. Results We detected native pro-mature GDF9 and BMP15 in human oocytes with molecular weights (Mw) of 47 kDa and 43 kDa, respectively. Concentrations of GDF9 and BMP15 in spent media after IVM were detected in 99% and 64% of the samples, respectively. The GDF9/BMP15 heterodimer was detected in 76% of the samples. Overall, the concentration of GDF9 was approximately 10-times higher than BMP15. The concentrations of both GDF9 and BMP15 were significantly lower in spent medium from MII oocytes than in media from oocytes that remained at the GV stage. Concentrations of the GDF9/BMP15 heterodimer did not differ between GV and MII oocytes. Furthermore, BMPR2 , SMAD3 , and SMAD5 were significantly upregulated in cumulus cells from MII oocytes, indicating that both GDF9 and BMP15 signaling were active during oocyte meiotic resumption in vitro . Conclusion These data suggest that the driving mechanisms for oocyte nuclear maturation may involve both GDF9 and BMP15 homodimers, while the role of the GDF9/BMP15 heterodimer is questionable.

PurposeThe aim of the present study was to improve the in vitro maturation (IVM) procedure using oocytes from surplus ovarian tissue after fertility preservation.MethodsTwenty-five patients aged 17–37 years were included in the study. Maturation was compared between oocytes collected in HEPES-buffered medium or saline, and we determined whether transport on ice prior to oocyte collection affected maturation. Two different IVM media were used that were supplemented with and without recombinant human midkine. Mature oocytes were assessed for aneuploidy using next-generation sequencing (NGS).ResultsOn average, 36 immature oocytes were collected from each patient (range 7–90, N = 895). Oocytes recovered from HEPES-buffered medium matured at a higher rate than oocytes recovered from saline (36% vs 26%, p < 0.01). Ovarian transportation on ice prior to the procedure negatively affected maturation compared with non-transported samples (42% vs 27%, p < 0.01). The addition of midkine improved maturation rate (34% vs 27%, p < 0.05). On average, 11 MII oocytes were obtained per patient (range 1–30). NGS of 53 MII oocytes and their first polar bodies indicated that 64% were euploid.ConclusionsThe study demonstrated unexpectedly high number of immature oocytes collected from surplus ovarian tissue without any stimulation. The overall MII rate was one in three, resulting in a total number of MII oocytes that was similar to the number obtained after ovarian stimulation. If these MII oocytes prove suitable for IVF, they will provide a substantial improvement in fertility preservation for patients and advance IVM as an interesting platform for further improvements in assisted reproduction.

PurposeTo investigate the effect of different FSH concentrations on human oocyte maturation in vitro and its impact on gene expression of key factors in the surrounding cumulus cells.MethodsThe study included 32 patients who underwent unilateral oophorectomy for ovarian tissue cryopreservation (OTC) (aged 28 years on average). Immature oocytes were collected from surplus medulla tissue. A total of 587 immature oocytes were divided into three categories according to the size of the cumulus mass: large (L-COCs), small (S-COCs), and naked oocytes (NOs), and submitted to 44-h IVM with one of the following concentrations of recombinant FSH: 0 IU/L, 20 IU/L, 40 IU/L, 70 IU/L, or 250 IU/L. After IVM, oocyte nuclear maturation stage and diameter were recorded. The relative gene expression of FSHR, LHCGR, and CYP19A1 in cumulus cells before (day 0; D0) and after IVM were evaluated.ResultsAddition of 70 or 250 IU/L FSH to the IVM medium improved oocyte nuclear maturation compared to 0, 20, and 40 IU/L FSH by upregulating LHCGR and downregulating FSHR in the cumulus cells.ConclusionFSH improved oocyte nuclear maturation at concentrations above 70 IU/L suggesting a threshold for FSH during IVM of ex vivo collected human oocytes from small antral follicles. Moreover, current results for the first time highlight that FSH function in vitro is mediated via cumulus cells by downregulating FSHR and upregulating LHCGR, which was also observed when the immature oocytes progressed in meiosis from the GV to the MII stage.

Background Ovarian tissue transplantation can restore fertility in young cancer survivors, however the detrimental loss of follicles following transplantation of cryopreserved ovarian tissue is hampering the efficiency of the procedure. This study investigates whether needle puncturing prior to transplantation can enhance revascularization and improve follicle survival in xenotransplanted human ovarian cortex. Methods Cryopreserved human ovarian cortex pieces ( N  = 36) from 20 women aged 24–36 years were included. During the thawing process, each piece of tissue was cut in halves; one half serving as the untreated control and the other half was punctured approximately 150–200 times with a 29-gauge needle. The cortex pieces were transplanted subcutaneously to immunodeficient mice for 3, 6 and 10 days ( N  = 8 patients) and for 4 weeks ( N  = 12 patients). After 3, 6 and 10 days, revascularization of the ovarian xenografts were assessed using immunohistochemical detection of CD31 and gene expression of angiogenic factors ( Vegfα , Angptl4 , Ang1 , and Ang2 ), and apoptotic factors ( BCL2 and BAX ) were performed by qPCR. Follicle density and morphology were evaluated in ovarian xenografts after 4 weeks. Results A significant increase in the CD31 positive area in human ovarian xenografts was evident from day 3 to 10, but no significant differences were observed between the needle and control group. The gene expression of Vegfα was consistently higher in the needle group compared to control at all three time points, but not statistically significant. The expression of Ang1 and Ang2 increased significantly from day 3 to day 10 in the control group ( p  < 0.001, p  = 0.0023), however, in the needle group this increase was not observed from day 6 to 10 (Ang2 p  = 0.027). The BAX / BCL2 ratio was similar in the needle and control groups. After 4-weeks xenografting, follicle density (follicles/mm 3 , mean ± SEM) was higher in the needle group (5.18 ± 2.24) compared to control (2.36 ± 0.67) ( p  = 0.208), and a significant lower percentage of necrotic follicles was found in the needle group (19%) compared to control (36%) ( p  = 0.045). Conclusions Needle puncturing of human ovarian cortex prior to transplantation had no effect on revascularization of ovarian grafts after 3, 6 and 10 days xenotransplantation. However, needle puncturing did affect angiogenic genes and improved follicle morphology.

Background Turner syndrome (TS) is a chromosomal disorder caused by complete or partial loss of one X chromosome, resulting in a high risk of premature ovarian insufficiency (POI) and infertility. While the underlying mechanisms are not fully understood, oocyte loss is known to begin in fetal life and continue throughout childhood, often leading to ovarian failure before the onset of puberty. Ovarian tissue cryopreservation (OTC) offers a potential method to preserve fertility in girls with TS, but the procedure remains experimental in this group. To date, only three cases of autotransplantation have been reported, and no live births have occurred in women with TS. Moreover, predictors of residual ovarian function and eligibility for OTC are poorly defined, and the long-term effects of unilateral oophorectomy in girls with already limited ovarian reserve are unknown. Objective To investigate long-term reproductive outcomes following OTC in girls with TS. Methods The Danish Turner Syndrome Cryopreservation Study is a nationwide, prospective cohort study with long-term follow-up, combining observational and interventional elements. Girls with TS aged 2–17 years are invited to participate. As ovarian reserve is depleted before adulthood in most girls with TS, all participants undergo ovarian function assessment to evaluate the likelihood of remaining viable follicles. If follicles are deemed present, unilateral OTC may be offered. The primary outcome is the number of pregnancies, miscarriages, and live births following autotransplantation of cryopreserved and thawed ovarian tissue in adulthood. Secondary objectives include identifying early predictors of POI, assessing the impact of oophorectomy on ovarian function and pubertal progression, and exploring molecular mechanisms of ovarian dysgenesis through genetic and epigenetic analyses of ovarian and peripheral tissues. Recruitment began in January 2024 and is ongoing at three university hospitals across Denmark. Follow-up is expected to continue until 2050. Conclusion This study addresses a critical gap in fertility preservation for girls with TS by evaluating the feasibility and long-term outcomes of OTC. The findings will improve understanding of POI progression, refine selection criteria for OTC, and support evidence-based counselling for girls with TS and their families. Trial registration ClinicalTrials.gov, NCT05740579. Registered 13 February 2023. https//clinicaltrials.gov/study/NCT05740579.

Girls and women suffering from a cancer that requires treatment with gonadotoxic drugs may experience cessation of reproductive function as a side effect due to obliteration of the ovarian pool of follicles. Techniques are now available for fertility preservation, such as cryopreservation of mature oocytes, embryos or ovarian cortical tissue. Whereas collection of mature oocytes and embryos requires at least a 2-week period, ovarian tissue may on short notice be frozen prior to treatment and can be transplanted back into women with ovarian failure. Transplanted frozen/thawed tissue supports survival and growth of follicles, giving rise to menstrual cycles and hormone production for several years. Worldwide, the procedure has resulted in the birth of 15 healthy children. Many cancer patients including girls and young women want fertility preservation, and the techniques are now being further developed and implemented in several centers.

The aim of this study was to investigate whether pH is stable when transporting ovarian tissue in media buffered with either HEPES or histidine. Furthermore, if the choice of transport media impacts the in vitro maturation rate of oocytes collected in connection with ovarian tissue cryopreservation. Human ovaries (n = 34) collected for ovarian tissue cryopreservation were transported immersed in either 30 ml of HEPES buffered (follicle flushing media (Origio; Denmark)) or histidine buffered media (Custodiol®-HTK, Koehler-Chemie, Germany). Tissue was transported on ice for 4–5 h. At arrival, the ovary was weighed, and the pH of the media was measured at 0 °C. From 15 patients, immature oocytes were collected for in vitro maturation, oocytes that matured to metaphase II were evaluated. The pH measured in the HEPES buffered media (pH = 7.5 ± 0.13, n = 18) was significantly higher ( p  < 0.001) than the pH measured in the histidine buffered media (pH = 7.2 ± 0.05, n = 16). The standard deviation of pH measurements for the histidine buffered media was significantly lower than for the HEPES buffered media measurements ( p  < 0.0001). A total of 170 and 247 immature oocytes were collected and in vitro matured from ovaries transported in HEPES and histidine buffered media, respectively. The maturation rate of immature oocytes after IVM was similar in the two groups. The results show that pH in the histidine buffered media is closer to the physiological level and more stable than in HEPES buffered medium and support the use of histidine buffered media for cooled transportation of human ovaries.

Polycystic ovaries (PCO) contain antral follicles that arrest growing around 3–11 mm in diameter, perturbing the dominant follicle’s selection and the subsequent ovulatory process. Proteomic alterations of PCO follicular fluid (FF) (i.e., microenvironment in which the oocyte develops until ovulation) have been studied from large follicles in connection with oocyte pickup during ovarian stimulation. The present study aimed to detect proteomic alterations in FF from unstimulated human small antral follicles (hSAF) obtained from PCO. After performing deep-sequencing label-free proteomics on 10 PCO and 10 non-PCO FF samples from unstimulated hSAF (4.6–9.8 mm), 1436 proteins were identified, of which 115 were dysregulated in PCO FF samples. Pathways and processes related to the immune system, inflammation, and oxidative stress appeared to be upregulated in PCO, while extracellular matrix receptors interactions, the collagens-containing extracellular matrix, and the regulation of signaling were downregulated. The secreted proteins SFRP1, THBS4, and C1QC significantly decreased their expression in PCO FF, and this downregulation was suggested to affect future oocyte competence. In conclusion, our study revealed, for the first time, evidence of proteomic alterations occurring in the FF of PCO hSAF that may be related to the dysfunction of follicular growth and subsequent oocyte competence.