Optimal human ovarian follicle isolation: A review focused on enzymatic digestion.

The damage or depletion of ovarian reserves due to aging or cancer treatment can increase the need for fertility preservation techniques. One of the most common ways of supporting fertility in prepubertal girls and women who require immediate cancer treatment is through ovarian tissue cryopreservation and re-transplantation following cancer treatment. However, a more appropriate method should be employed in diseases such as leukemia, where malignant cells may be present in cryopreserved tissue, instead of ovarian tissue transplantation. Human ovarian follicle isolation for in vitro culture or the use of artificial ovaries for their growth can decrease the risk of reintroducing cancer cells into these individuals. Here we review the methods for the isolation of human ovarian follicles.

Successful 3D culture and transplantation of mouse isolated preantral follicles in hydrogel of bioengineered Wharton's jelly.

MAIN OBJECTIVE: Due to Human Wharton's Jelly (HWJ) could be applied in tissue engineering as a bio scaffold, the present study was conducted to investigate the effects of HWJ hydrogel on in vitro culture and auto-transplantation of mouse ovarian follicles. MATERIALS AND METHODS: HWJ was isolated from umbilical cord and decellularized with SDS/Tris/EDTA. DNA, Collagen and Glycosaminoglycans (GAGs) were measured. Decellularized Wharton's Jelly (DWJ) was dissolved to make Wharton's Jelly Hydrogel (WJH), and composited with Alginate (ALG) (1.5%) in equal ratio (WJH+ALG). Then, mouse preantral follicles were isolated and encapsulated in 10µL droplets of WJH and randomly considered for both 14 days culture and auto-transplantation. RESULTS: Collagen, GAGs and DNA evaluations showed majority of WJ cells have been removed and MTT approved no toxicity. Degradation rate and rheological analysis represented optimal hydrogel compatibility. The data from in vitro culture revealed significant antral formation in WJH+ALG (P≤0.05). In transplantation, follicles failed to survive in ALG; however, survived in WJH+ALG to antral stage (P<0.05). VEGF and CD34 had greater expression in WJH+ALG than ALG (P< 0.05). CONCLUSION: Wharton's jelly hydrogel and Alginate compound is interesting composite for successful development of mouse preantral follicles in both 3D in vitro culture and transplantation.

Ovarian extracellular matrix-based hydrogel for human ovarian follicle survival in vivo: A pilot work.

To successfully assemble a bio-engineered ovary, we need to create a three-dimensional matrix able to accommodate isolated follicles and cells. The goal of this study was to develop an extracellular matrix hydrogel (oECM) derived from decellularized bovine ovaries able to support, in combination with alginate, human ovarian follicle survival and growth in vitro. Two different hydrogels (oECM1, oECM2) were produced and compared in terms of decellularization efficiency (dsDNA), ECM preservation (collagen and glycosaminoglycan levels), ultrastructure, rigidity, and cytotoxicity. oECM2 showed significantly less dsDNA, greater retention of glycosaminoglycans and better rigidity than oECM1. Isolated human ovarian follicles were then encapsulated in four selected hydrogel combinations: (1) 100% oECM2, (2) 90% oECM2 + 10% alginate, (3) 75% oECM2 + 25% alginate, and (4) 100% alginate. After 1 week of in vitro culture, follicle recovery rate, viability, and growth were analyzed. On day 7 of in vitro culture, follicle recovery rates were 0%, 23%, 65%, 82% in groups 1-4, respectively, rising proportionally with increased alginate content. However, there was no difference in follicle viability or growth between groups 2 and 3 and controls (group 4). In conclusion, since pure alginate cannot be used to graft preantral follicles due to its poor revascularization and degradation after grafting, oECM2 hydrogel combined with alginate may provide a new and promising alternative to graft isolated human follicles in a bio-engineered ovary.

NLRP3 inflammasome: A joint, potential therapeutic target in management of COVID-19 and fertility problems.

To overcome COVID-19 long-term consequences, one possible approach is to control inflammasomes activation, because SARS-CoV-2 can induce humoral and cellular immune responses. In this opinion article we hypothesized that if it is proven with convincing and unmistakable evidence that firstly, SARS-CoV-2 can enter cells and damage them through its common receptors in the reproductive tissues, and secondly, inflammasome pathway activation is responsible for the damages caused, then the inflammasome inhibitors might be considered as suitable candidates in preventing the pathological effects on the germ cells and reproductive tissues and subsequent fertility.

Mitochondrial content, activity, and morphology in prepubertal and adult human ovaries.

PURPOSE: To investigate whether mitochondrial content, activity, and morphology differ in prepubertal versus adult ovarian follicles. METHODS: Ovarian tissue was collected from 7 prepubertal girls (age 1-10 years) and 6 adult women (age 20-35 years). Primordial and primary follicles were isolated from frozen-thawed prepubertal and adult ovarian tissue and their viability was assessed. Mitochondrial content was investigated by TOMM20 immunostaining of prepubertal and adult ovarian tissue, while mitochondrial activity in isolated follicles was analyzed by MitoTracker CM-H2XRos and JC-1. Frozen-thawed ovarian tissue from the same patients was also evaluated by transmission electron microscopy to examine mitochondrial morphology. RESULTS: Higher TOMM20 staining was detected in prepubertal follicles compared to their adult counterparts, indicating the presence of more mitochondria in prepubertal follicles. Analysis of mitochondrial activity by MitoTracker showed higher fluorescence intensity in prepubertal follicles, suggesting that follicles in this group are more active than adult follicles. JC-1 analysis did not reveal any statistically significant difference in the inactive/active ratio between the two groups. Moreover, ultrastructural analysis by TEM detected morphological differences in the shape and cristae of prepubertal mitochondria, probably suggesting a mechanism of response to autophagy. CONCLUSION: Differences in the number, activity, and morphology of mitochondria were reported, suggesting that consequential modifications might occur during puberty, which could be the window of opportunity required by mitochondria to undergo changes needed to reach maturity, and hence the capacity for ovulation and fertilization.

Ovarian tissue transportation: a systematic review.

In recent years, some countries and fertility preservation networks have started adopting 24 h transportation for ovarian tissue, a practice that has the potential to spread very quickly due to the high costs and bureaucracy involved in the establishment of ovarian tissue cryobanks. While pregnancies and live births have been reported after such long periods of transportation, this, however, remains an empirical procedure. This review aims to prompt reflection on ovarian tissue transport, highlighting the lack of knowledge in humans by providing a counterpoint looking into more than 40 studies published in different animal models. By discussing these studies in animals, the findings of various models can be deciphered, and light shed on the patterns identified. Like the development of different assisted reproductive technology procedures, this is an important step in creating guidelines for future studies on human ovarian tissue transportation.

Follicle populations and vascularization in ovarian tissue of pediatric patients before and after long-term grafting.

OBJECTIVE: To characterize ovarian tissue from pediatric patients by evaluating development and vascularization in follicle populations and comparing it with adult tissue after xenografting. DESIGN: Prospective experimental study. SETTING: Academic research center. PATIENT(S): Five children (median age 3 years) and seven women (median age 28 years). INTERVENTION(S): Hematoxylin and eosin staining, immunofluorescence, and transmission electron microscopy (TEM) evaluation before and after grafting. MAIN OUTCOME MEASURE(S): Follicle density, morphology, classification, and size, ovarian tissue vascularization, follicle ultrastructure. RESULT(S): Frozen-thawed ovarian tissue was divided into three fragments: nongrafted controls, TEM, and xenografting for 20 weeks. Follicle density was statistically significantly higher in pediatric than adult patients; even though it decreased in both groups after transplantation, it remained higher in pediatric patients. In the pediatric group, quiescent-stage follicles were the majority of the follicle pool before and after grafting, while growing follicles statistically significantly increased in both groups after grafting. Abnormal and atretic follicles were also observed in pediatric tissue and declined with age and after grafting. Pediatric ovarian tissue contained more and larger immature vessels, while mature vessels were larger in adults. The TEM analysis of abnormal pediatric follicles showed loss of shape and vacuolization of the cytoplasm without organelle damage. CONCLUSION(S): Statistically significant differences in follicle density were observed between pediatric and adult patients, but the follicle proportions were similar before and after grafting, with the exception of atretic and abnormal follicles. Pediatric tissue contains more and larger immature vessels than adult tissue, and the posttransplantation revascularization process is accelerated in this group.

Perinatal exposure to bisphenol A impacts in the mammary gland morphology of adult Mongolian gerbils.

The endocrine disruptive effects caused by bisphenol A (BPA) are well known. Despite this, to date, evaluation of its long term effects is limited, meaning that there is still much to be unveiled in terms of alterations caused by perinatal exposure to BPA. Our aim was to determine if perinatal exposure to two different doses of BPA causes long term morphological and molecular alteration effects in the mammary gland (MG). We evaluated MG from Mongolian gerbil offspring exposed perinatally (during gestation and lactation) to 50 or 5000 µg/kg/day BPA. At 90 days of age the animals were subjected to a single dose of N-nitroso-N-methylurea in order to mimic a carcinogenic environment. At 6 months of age, animals in estrous were euthanized for morphological evaluation of the MGs. The MG architecture presented considerable changes in terms of detached epithelial cells, inflammation, glandular hyperplasia, and collagen fiber deposition. Furthermore, a higher index of epithelial cell proliferation was detected in comparison to the intact control group. In addition, we verified a higher molecular expression of EZH2 in the vehicle treated group, indicating that corn oil applied alone can alter the expression of this epigenetic biomarker. In conclusion, BPA perinatal exposure promotes significant changes in glandular cytoarchitecture and increases glandular epithelium proliferation rate, leading to the retention of stem-like properties. This event could compromise the fate and differentiation potential of mammary epithelium.

Impact of perinatal bisphenol A and 17ß estradiol exposure: Comparing hormone receptor response.

Hormonal regulation controls mammary gland (MG) development. Therefore some hormone-related factors can disrupt the early phases of MGs development, making the gland more susceptible to long term modifications in its response to circulating hormones. Endocrine disruptors, such as bisphenol A (BPA), are able to cause alterations in hormone receptor expression, leading to changes in the cell proliferation index, which may expose the tissue to neoplastic alterations. Thus, we evaluated the variations in hormone receptor expression in the MG of 6-month old Mongolian gerbils exposed to BPA and 17ß estradiol during the perinatal period. Receptors for estrogen alpha (ERα), beta (ERß), progesterone (PGR), prolactin (PRL-R), and co-localization of connexin 43 (Cx43) and ERα in gerbils were analyzed, and serum concentrations of estradiol and progesterone were assessed. No alterations in body, liver, and ovary-uterus complex weights were observed. However, there was an increase in epithelial ERα expression in the 17ß estradiol (E2) group and in PGR in the BPA group. Although immunohistochemistry did not show alterations in ERß expression, western blotting revealed a decrease in this protein in the BPA group. PRL-R was more present in epithelial cells in the vehicle control (VC), E2, and BPA groups in comparison to the intact control group. Cx43 was more frequent in E2 and BPA groups, suggesting a protective response from the gland against possible malignancy. Serum concentration of estradiol reduced in VC, E2, and BPA groups, confirming that alterations also impacts steroid levels. Consequently, perinatal exposure to BPA and the reference endogenous estrogen, 17ß estradiol, are able to increase the tendency of endocrine disruption in MG in a long term manner, since repercussions are observed even 6 months after exposure.

Role of the PI3K and Hippo pathways in follicle activation after grafting of human ovarian tissue.

PURPOSE: Our aim was to elucidate the mechanisms involved in follicle activation of the ovarian reserve after human ovarian tissue transplantation, with specific focus on the role of the effectors of the PI3K (mTOR and FOXO1) and Hippo (YAP) signaling pathways and whether they are somehow altered. METHODS: Frozen-thawed ovarian tissue was collected from six women (age 25-35 years) undergoing surgery for non-ovarian pathologies and divided into 4 fragments in each case: one for non-grafted controls and three for grafting to immunodeficient mice for 3, 7 and 21 days. The tissue was processed for hematoxylin and eosin staining, immunohistochemistry and immunofluorescence at different timepoints before and after grafting. Activation of the PI3K and Hippo signaling pathways was investigated by analysis of mTOR phosphorylation, FOXO1 cytoplasmic localization and YAP nuclear localization. RESULTS: No change in mTOR levels was observed in primordial follicles post-transplantation, but a significant upturn was recorded in growing follicles compared with primordial follicles, irrespective of grafting time. A higher percentage of primordial follicles was also found with FOXO1 in the cytoplasm after 3 days of transplantation than in non-grafted controls. Finally, a greater proportion of primordial follicles was detected with YAP in the nucleus at all timepoints after grafting. CONCLUSIONS: This study supports the hypothesis that follicle activation may occur as an early event after transplantation, with follicle growth and death both contributing to the burnout phenomenon. This is the first time that the effectors of the PI3K and Hippo pathways have been investigated in grafted human ovarian tissue and their role in burnout documented.

Formation and activation induction of primordial follicles using granulosa and cumulus cells conditioned media.

Fertility preservation of prepubertal girls subjected to invasive cancer therapy necessitates defining protocols for activation of isolated primordial follicles. Granulosa (GCs) and cumulus cells (CCs) play pivotal role in oocyte development. Although GCs and CCs share some similarities, they differ in growth factors production. The current study was conducted to evaluate the effects of GCs, CCs and their conditioned media on mice primordial follicles activation. One-day-old mice ovaries were subjected to 6-day culture with base medium (BM), GC conditioned medium (GCCM), GC coculture (GCCC), CC conditioned medium (CCCM) or CC coculture (CCCC). Follicular growth and primordial to primary follicle transition was observed during 6-day culture, and follicular activation rate tended to be greater in GCCM than other groups (0.05

In vivo characterization of metabolic activity and oxidative stress in grafted human ovarian tissue using microdialysis.

OBJECTIVE: To characterize oxidative stress and metabolic activity in xenografted human ovarian tissue using microdialysis. DESIGN: Prospective experimental study. SETTING: Gynecology research unit at a university hospital. PATIENT(S): Cryopreserved ovarian cortex from five women 27-35 years of age. INTERVENTION(S): Frozen-thawed human ovarian tissue fragments were xenografted to the back muscle of ten nude mice. Before grafting, a microdialysis probe was placed inside each fragment. MAIN OUTCOME MEASURE(S): Daily reactive oxygen species (ROS), lactate, and glucose levels were collected by means of microdialysis. Follicle loss (hematoxylin and eosin), murine and human vascularization, and vessel stability (CD31, von Willebrand factor, and α-smooth muscle actin triple immunofluorescence) were analyzed on post-grafting days 10 and 21. RESULT(S): Lactate levels were significantly higher than glucose levels until day 10, after which time the lactate-glucose ratio stabilized at ∼1:1. Regarding ROS generation, there were two peaks on post-grafting days 10 and 17. Total vascularization increased significantly up to day 10 and remained similar up to day 21. However, murine vessel area and stabilization significantly increased up to day 21. Major follicle loss occurred in the first 10 days after transplantation. CONCLUSION(S): Our data validated microdialysis as a tool to characterize metabolic behavior and oxidative stress in grafted ovarian tissue. Three different post-grafting periods were identified according to the metabolic activity of grafted tissue, showing a long progression from anaerobic to aerobic metabolism and a protracted period of ROS generation. Oxidative stress was observed relatively late, after the most critical period of follicle loss, and lasted until the tissue vasculature stabilized.

Utilizing Fibrin-Alginate and Matrigel-Alginate for Mouse Follicle Development in Three-Dimensional Culture Systems.

In vitro culture of ovarian follicles is a new technique in reproductive technology, which helps in understanding the process of folliculogenesis. The in vitro culture of follicles could be carried out using three-dimensional (3D) natural scaffolds that mimic the ovarian tissue stroma. Selection of the right matrix and culture media in these scaffolds could increase the survival and maturation of the follicles. In this work, the applicability of matrigel-alginate (MA) and fibrin-alginate (FA) 3D scaffolds for folliculogenesis was assessed. The ovaries of 13-day-old Naval Medical Research Institute (NMRI) mice were isolated and distributed into control and vitrification groups. Preantral follicles (mean diameter: 120-140 µm) were mechanically isolated from control and vitrified-warmed ovaries, encapsulated in MA or FA scaffold and cultured for 12 days. Follicle survival, growth, maturation, and quantitative expression of oocyte maturation genes (Gdf9, Bmp15, Fgf8, KitL, Kit, and Amh) and proteins (GDF9 and BMP15) were assessed. Survival rate of culture preantral follicles in control groups was found to be significantly higher than vitrified follicles. Antrum formation was similar in all groups. Follicle diameters were significantly increased in all groups during culture period. A decreasing pattern of gene expression was seen for all genes in all groups. This trend was verified through evaluation of protein expression, during which there was strong staining in antral follicles from all groups in the last day of in vitro culture. The better survival and maturation rate of follicles in the MA compared to FA scaffold indicates that the MA matrix, being rich in extracellular matrix components, could mimic the ovarian condition better and presents a good environment for follicle development.

A novel fibrin-based artificial ovary prototype resembling human ovarian tissue in terms of architecture and rigidity.

PURPOSE: The aim of this study is to optimize fibrin matrix composition in order to mimic human ovarian tissue architecture for human ovarian follicle encapsulation and grafting. METHODS: Ultrastructure of fresh human ovarian cortex in age-related women (n = 3) and different fibrin formulations (F12.5/T1, F30/T50, F50/T50, F75/T75), rheology of fibrin matrices and histology of isolated and encapsulated human ovarian follicles in these matrices. RESULTS: Fresh human ovarian cortex showed a highly fibrous and structurally inhomogeneous architecture in three age-related patients, but the mean ± SD of fiber thickness (61.3 to 72.4 nm) was comparable between patients. When the fiber thickness of four different fibrin formulations was compared with human ovarian cortex, F50/T50 and F75/T75 showed similar fiber diameters to native tissue, while F12.5/T1 was significantly different (p value < 0.01). In addition, increased concentrations of fibrin exhibited enhanced storage modulus with F50/T50, resembling physiological ovarian rigidity. Excluding F12.5/T1 from further analysis, only three remaining fibrin matrices (F30/T50, F50/T50, F75/T75) were histologically investigated. For this, frozen-thawed fragments of human ovarian tissue collected from 22 patients were used to isolate ovarian follicles and encapsulate them in the three fibrin formulations. All three yielded similar follicle recovery and loss rates soon after encapsulation. Therefore, based on fiber thickness, porosity, and rigidity, we selected F50/T50 as the fibrin formulation that best mimics native tissue. CONCLUSIONS: Of all the different fibrin matrix concentrations tested, F50/T50 emerged as the combination of choice in terms of ultrastructure and rigidity, most closely resembling human ovarian cortex.

A modified and tailored human follicle isolation procedure improves follicle recovery and survival.

BACKGROUND: Ovarian tissue cryopreservation followed by transplantation after cancer remission is the most commonly applied fertility restoration approach in very young girls and women who require immediate cancer therapy. However, clinicians strongly advise against reimplantation of one's own ovarian tissue when there is a high risk of recurrence after grafting. For these patients, development of an alternative strategy, namely a transplantable artificial ovary, offers future hope of conceiving. The first essential requirement for an artificial ovary is the set-up of a safe and effective follicle isolation procedure. Despite encouraging results with different variants of this technique, none of them take into the account the physiology and great variability in follicular density inside individual tissue fragments and between different patients. The goal of this study was to improve our previously applied follicle isolation procedure in order to develop a tailored isolation procedure for human follicles according to individual tissue properties. To this end, enzymatic digestion was divided into three time intervals in order to initially recover the first follicles to be isolated, and then further dissociate undigested fragments of tissue containing entrapped follicles. RESULTS: After thawing frozen human ovarian tissue using a modified and tailored follicle isolation method, already 35% of follicles were fully isolated and recovered after 30 min of enzymatic digestion. Indeed, this protocol resulted in a higher follicle yield (p < 0.01) and greater numbers of primordial and primary follicles (p < 0.05) than the previous approach. However, no significant difference was found in caspase-3-positive and Ki67-positive staining between the two isolation protocols. In addition, greater follicle quality was demonstrated. When human follicles isolated using the modified protocol were encapsulated in a fibrin matrix with high concentrations of fibrinogen and thrombin and xenografted to a SCID mouse, more follicles were found to be healthy after one week of transplantation than in a previous our study. CONCLUSIONS: With the modified follicle isolation method, we were able to maximize the number and quality of isolated primordial and primary follicles, and develop a tailored follicle isolation procedure according to individual tissue properties. Moreover, improved follicle survival inside an artificial ovary prototype was detected after one week of xenografting.

Evaluation of a human ovarian follicle isolation technique to obtain disease-free follicle suspensions before safely grafting to cancer patients.

OBJECTIVE: To evaluate the safety of our follicle isolation procedure in a model of ovarian tissue artificially contaminated with cancer cells, then to improve the procedure to effectively eliminate malignant cells from follicle suspensions without altering viability. DESIGN: Prospective experimental study. SETTING: Gynecology research unit in a university hospital. PATIENT(S): Ten women undergoing laparoscopy for benign gynecologic disease. INTERVENTION(S): Follicle isolation from ovarian tissue artificially contaminated with marked fluorescent leukemic cells, either by the usual pickup technique without further treatment (group 1) or by washing three times after pickup (group 2). MAIN OUTCOME MEASURE(S): Evidence of leukemic cells in follicle suspensions using fluorescence microscopy and quantitative real-time polymerase chain reaction, and analysis of follicle viability. RESULT(S): In group 1, 196 leukemic cells were detected by fluorescence microscopy out of 499 follicles retrieved, while just one leukemic cell was found among 772 follicles after three washes. The BCR-ABL fusion transcript was detected when at least 19 cells were present in follicle suspensions; four samples were positive in group 1, and all were negative in group 2. Follicle viability was similar in both groups (95.6% vs. 96.4%). CONCLUSION(S): Cancer cells could inadvertently be picked up with isolated follicles in case of malignant contamination of ovarian tissue. A simple purging procedure consisting of three washes proved effective for eliminating leukemic cells while maintaining good follicle viability.

A new step toward the artificial ovary: survival and proliferation of isolated murine follicles after autologous transplantation in a fibrin scaffold.

OBJECTIVE: To create an artificial ovary to provide an alternative way of restoring fertility in patients who cannot benefit from transplantation of cryopreserved ovarian tissue due to the threat of reintroducing malignant cells. DESIGN: In vivo experimental study. SETTING: Gynecology research unit in a university hospital. ANIMAL(S): Six-week-old female NMRI mice. INTERVENTION(S): Autografting of isolated preantral follicles and ovarian cells (OCs) encapsulated in two fibrin matrices containing low concentrations of fibrinogen (F; mg/mL) and thrombin (T; IU/mL): F12.5/T1 and F25/T4. MAIN OUTCOME MEASURE(S): Follicular density and development, OC survival and proliferation, inflammatory response, and vascularization. RESULT(S): After 1 week, the follicle recovery rate ranged from 30.8% (F25/T4) to 31.8% (F12.5/T1). With both fibrin formulations, all follicles were found to be alive or minimally damaged, as demonstrated by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay, and at the growing stage (primary, secondary, and antral follicles), confirmed by Ki67 immunostaining. Isolated OCs also survived and proliferated after grafting, as evidenced by <1% apoptotic cells and a high proportion of Ki67-positive cells. Vessels were found in both fibrin formulations, and the global vascular surface area varied from 1.35% (F25/T4) to 1.88% (F12.5/T1). Numerous CD45-positive cells were also observed in both F25/T4 and F12.5/T1 combinations. CONCLUSION(S): The present study is the first to show survival and growth of isolated murine ovarian follicles 1 week after autotransplantation of isolated OCs in a fibrin scaffold. The results indicate that fibrin is a promising candidate as a matrix for the construction of an artificial ovary. Xenotransplantation of isolated human follicles and OCs is the necessary next step to validate these findings.

Evaluation of cryopreserved ovarian tissue from prepubertal patients after long-term xenografting and exogenous stimulation.

OBJECTIVE: To assess follicular development after long-term xenotransplantation and exogenous stimulation of cryopreserved prepubertal ovarian tissue. DESIGN: Pilot study. SETTING: Gynecology research unit in a university hospital. PATIENT(S): Cryopreserved ovarian fragments were obtained from five prepubertal patients aged 7.2-12.2 years. INTERVENTION(S): Xenografting of frozen-thawed prepubertal ovarian fragments to SCID mice for 5 months and exogenous stimulation. MAIN OUTCOME MEASURE(S): Follicular density, morphology, proliferation, development. RESULT(S): Follicular density varied between 1.05 and 47.89 follicles/mm(2) in frozen-thawed ovarian tissue and 0.48 and 32.74 follicles/mm(2) in grafted prepubertal ovarian tissue. Growing follicles at the last stage of follicular development were observed at significantly higher proportions after grafting. No statistical difference was evidenced in the number of primordial follicles, representing the largest proportion of the follicle pool (99.51% before grafting and 92.46% after grafting). Ki67 and antimüllerian hormone expression were observed in these growing follicles. CONCLUSION(S): This is the first description of transplantation of human cryopreserved prepubertal ovarian tissue to mice, demonstrating that a very high number of follicles survive after transplantation and a large pool of primordial follicles remains dormant. Growing follicles were observed, proving the responsiveness of prepubertal ovarian tissue to gonadotropins.

Vitrification and xenografting of human ovarian tissue.

OBJECTIVE: To assess the efficiency of two vitrification protocols to cryopreserve human preantral follicles with the use of a xenografting model. DESIGN: Pilot study. SETTING: Gynecology research unit in a university hospital. PATIENT(S): Ovarian biopsies were obtained from seven women aged 30-41 years. INTERVENTION(S): Ovarian tissue fragments were subjected to one of three cryopreservation protocols (slow freezing, vitrification protocol 1, and vitrification protocol 2) and xenografted for 1 week to nude mice. MAIN OUTCOME MEASURE(S): The number of morphologically normal follicles after cryopreservation and grafting and fibrotic surface area were determined by histologic analysis. Apoptosis was assessed by the TUNEL method. Morphometric analysis of TUNEL-positive surface area also was performed. Follicle proliferation was evaluated by immunohistochemistry. RESULT(S): After xenografting, a difference was observed between the cryopreservation procedures applied. According to TUNEL analysis, both vitrification protocols showed better preservation of preantral follicles than the conventional freezing method. Moreover, histologic evaluation showed a significantly higher proportion of primordial follicles in vitrified (protocol 2)-warmed ovarian tissue than in frozen-thawed tissue. The proportion of growing follicles and fibrotic surface area was similar in all groups. CONCLUSION(S): Vitrification procedures appeared to preserve not only the morphology and survival of preantral follicles after 1 week of xenografting, but also their ability to resume folliculogenesis. In addition, vitrification protocol 2 had a positive impact on the quiescent state of primordial follicles after xenografting.

Cryopreservation of prepubertal mouse testicular tissue by vitrification.

OBJECTIVE: To compare cryopreservation of prepubertal testicular tissue after vitrification (V) and slow-freezing (SF). DESIGN: Prospective experimental study. SETTING: Academic research unit. ANIMAL(S): Six-day-old mice. INTERVENTION(S): After cryopreservation, viability tests (n = 10) and short-term culture (1 and 3 days) (n = 5) were performed. A comparison was made with fresh (FR) and noncultured controls (FR Ctrl). MAIN OUTCOMES MEASURE(S): Tissue viability was assessed by lactate dehydrogenase release assay. Apoptosis (caspase-3) and proliferation (Ki67) were evaluated by immunohistochemistry, and tubular diameter, integrity, and cell density by light microscopy. RESULT(S): Lactate dehydrogenase release was greater after SF than V (54.6% vs. 26.7%), whereas the mean number of apoptotic cells/tubule was higher after V than SF (2.13 vs. 0.07). On day 1, a decrease in cell density was noted in both cryopreserved groups, but this difference was not subsequently observed. On day 3, an increase in proliferation was seen in the SF and V groups versus FR tissue, and similar tubular diameter, integrity, and cell density were found in all cultured groups. CONCLUSION(S): This study shows that both SF and V protocols preserve survival, development, and integrity of prepubertal mouse testicular tissue in short-term organotypic culture. Additional investigation should now be conducted to assess tissue functionality.