Viability assessment of fresh and frozen/thawed isolated human follicles: reliability of two methods (Trypan blue and Calcein AM/ethidium homodimer-1)

Comparison of cation and anion-mediated resolution enhancement of bioprinted hydrogels for membranous tissue fabrication

Fabrication of engineered thin membranous tissues (TMTs) presents a significant challenge to researchers, as these structures are small in scale, but present complex anatomies containing multiple stratified cell layers. While numerous methodologies exist to fabricate such tissues, many are limited by poor mechanical properties, need for post-fabrication, or lack of cytocompatibility. Extrusion bioprinting can address these issues, but lacks the resolution necessary to generate biomimetic, microscale TMT structures. Therefore, our goal was to develop a strategy that enhances bioprinting resolution below its traditional limit of 150 μm and delivers a viable cell population. We have generated a system to effectively shrink printed gels via electrostatic interactions between anionic and cationic polymers. Base hydrogels are composed of gelatin methacrylate type A (cationic), or B (anionic) treated with anionic alginate, and cationic poly-L-lysine, respectively. Through a complex coacervation-like mechanism, the charges attract, causing compaction of the base GelMA network, leading to reduced sample dimensions. In this work, we evaluate the role of both base hydrogel and shrinking polymer charge on effective print resolution and cell viability. The alginate anion-mediated system demonstrated the ability to reach bioprinting resolutions of 70 μm, while maintaining a viable cell population. To our knowledge, this is the first study that has produced such significant enhancement in extrusion bioprinting capabilities, while also remaining cytocompatible.

An injectable hydrogel of porcine cholecyst extracellular matrix for accelerated wound healing

Hydrogel formulations of xenogeneic extracellular matrices have been widely used for topical wound care because of their exceptional tunability over other formulations like lyophilized sheets, powders, non-injectable gels, pastes, and ointments. This is important in the treatment of wounds with irregular shapes and depth. This study identified an injectable hydrogel formulation of porcine cholecyst extracellular matrix (60%) in medical-grade carboxymethyl cellulose (40%) as vehicle and evaluated its biomaterial properties. Further, an in-depth evaluation of in vivo wound healing efficacy was conducted in a rat full-thickness skin excision wound healing model, which revealed that the hydrogel formulation accelerated wound healing process compared to wounds treated with a commercial formulation and untreated wounds. The hydrogel appeared to have promoted a desirable pro-regenerative tissue reaction predominated by Th2 helper lymphocytes and M2 macrophages as well as an effective collagen remodeling indicative of diminished scarring. In conclusion, the porcine cholecyst extracellular matrix injectable hydrogel formulation appeared to be a promising candidate formulation as an advanced wound care biomaterial for faster healing of skin wounds with minimal scarring.

Solvent-free enzymatic synthesis and evaluation of vanillyl propionate as an effective and biocompatible preservative

Preservatives are chemicals added to protect products against microbial spoilage, and thus are indispensable for pharmaceuticals, cosmetics, and foods. Due to growing concerns about human health and environments in conventional chemical preservatives, many companies have been seeking safe and effective alternatives that can be produced through environment-friendly processes. In this work, in order to develop effective and safe preservatives from plants, we attempt solvent-free lipase-catalyzed transesterification of vanillyl alcohol with ethyl propionate for the first time. The reaction product, vanillyl propionate was efficiently obtained in a high yield. Unlike vanillyl alcohol and ethyl propionate, vanillyl propionate showed antimicrobial activity. The minimal inhibitory concentration test showed that it exhibited high and broad antimicrobial activity against all the tested microorganisms (Gram-negative and Gram-positive bacteria, yeasts, and molds), which was overall comparable to that of propyl paraben, which is one of the most effective preservatives. It was also found to have even higher antioxidant capacity and biocompatibility with human cells than propyl paraben. Vanillyl propionate, which is a plant-based preservative produced through a green bioprocess, is expected to be successfully applied to various industries thanks to its high antimicrobial and antioxidant effect, and high biocompatibility.

Optimizing the Ovarian Tissue Cryopreservation in the 'Oncofertility' Institutional Program at an Italian National Cancer Institute

BACKGROUND

The majority of female cancer patients undergoing anticancer treatments are at risk of experiencing 'cancer treatment-related infertility', which can result in permanent damage to their reproductive prospects. Among the fertility preservation methods, ovarian tissue cryopreservation (OTC) has emerged as an alternative for these patients. The Cancer Institute of Bari initiated a research program to assess the feasibility of OTC. This study compares the viability of ovarian cortical fragments cryopreserved using slow freezing (SF) and ultra-rapid freezing (URF) methods.

METHODS

Ovarian cortex biopsies were obtained from 11 fertile women enrolled in our oncofertility service between June 2022 and January 2023. After tissue collection, a histological assessment was performed before cryopreservation. OTC was carried out using both SF and URF methods. Six months later, thawed samples were evaluated for follicle counts and histological integrity.

RESULTS

No statistically significant difference was observed in the proportion of intact follicles (means of 31.5% and 73.0% in the SF and URF groups, respectively; p = 0.064). However, there was a significant difference in the number of follicles between the SF group (n = 149) and the URF group (n = 37) (p = 0.046).

CONCLUSIONS

We assessed the viability of ovarian cortex after freezing and thawing, focusing on the structural integrity of follicles. Our findings suggest that there are no significant differences between the SF and URF methods.

Fabrication and Morphological Control of Nonspherical Alginate Hydrogel Particles

We report a simple platform for the fabrication of nonspherical alginate hydrogel particles using a dripping method. Hydrogel particles with novel morphologies, such as vortex ring, teardrop, disk, sphere, and mushroom, are fabricated by controlling various parameters. We monitored the deformation process of the hydrogel particles after they penetrated the crosslinking solution using a high-speed camera. Then, we proposed a mechanism showing a unique morphological transformation from a spherical to a disk shape. We demonstrated how controlling the collecting height that causes the drop impact force against the crosslinking solution surface was critical to producing hydrogel particles with these intriguing shapes. In particular, disk-shaped alginate particles show their ability as potential platforms for culturing mouse adrenocortical tumor cells (Y1) and a hippocampal neuronal cell (HT-22). To modify alginate particles, cell-adhesive gelatin is incorporated into the alginate matrix and then alginate particles are coated with poly(allylamine hydrochloride). Two modified alginate particles show good adhesion and proliferation rates on their surfaces. In particular, the hybrid hydrogel particles provide great potential to be developed into promising materials for cell culture, drug delivery, and tissue engineering.

CTR9 drives osteochondral lineage differentiation of human mesenchymal stem cells via epigenetic regulation of BMP-2 signaling

Cell fate determination of human mesenchymal stem/stromal cells (hMSCs) is precisely regulated by lineage-specific transcription factors and epigenetic enzymes. We found that CTR9, a key scaffold subunit of polymerase-associated factor complex (PAFc), selectively regulates hMSC differentiation to osteoblasts and chondrocytes, but not to adipocytes. An in vivo ectopic osteogenesis assay confirmed the essentiality of CTR9 in hMSC-derived bone formation. CTR9 counteracts the activity of Enhancer Of Zeste 2 (EZH2), the epigenetic enzyme that deposits H3K27me3, in hMSCs. Accordingly, CTR9 knockdown (KD) hMSCs gain H3K27me3 mark, and the osteogenic differentiation defects of CTR9 KD hMSCs can be partially rescued by treatment with EZH2 inhibitors. Transcriptome analyses identified bone morphology protein-2 (BMP-2) as a downstream effector of CTR9. BMP-2 secretion, membrane anchorage, and the BMP-SMAD pathway were impaired in CTR9 KD MSCs, and the effects were rescued by BMP-2 supplementation. This study uncovers an epigenetic mechanism engaging the CTR9-H3K27me3-BMP-2 axis to regulate the osteochondral lineage differentiation of hMSCs.

Effects of N-acetylcysteine on Growth, Viability, and Ultrastructure of In Vitro Cultured Bovine Secondary Follicles

This study aimed to investigate the effects of different concentrations of N-acetylcysteine (NAC) on the growth, antrum formation, viability, and ultrastructure of bovine secondary follicles cultured in vitro for 18 days. To this end, the follicles were cultured in TCM-199+ medium alone or supplemented with 1.0, 5.0, or 25.0 mM NAC. Follicular growth, antrum formation, viability (calcein-AM and ethidium homodimer-1) and ultrastructure were evaluated at the end of culture period. The results showed that 1.0 mM NAC increased the percentage of growing follicles and the fluorescence intensity for calcein-AM when compared to other treatments (p < 0.05). On the other hand, follicles cultured with 25.0 mM NAC had higher fluorescence intensity for ethidium homodimer-1, which is a sign of degeneration. Ultrastructural analysis showed that oocytes from follicles cultured in control medium alone or with 1 mM NAC had intact zonae pellucidae in close association with oolemmae, but the ooplasm showed mitochondria with a reduced number of cristae. On the other hand, oocytes from follicles cultured with 5 or 25 mM NAC had extremely vacuolated cytoplasm and no recognizable organelles. In conclusion, 1 mM NAC increases cytoplasmic calcein staining and the growth rate in bovine secondary follicles cultured in vitro, but the presence of 5 or 25 mM NAC causes damage in cellular membranes and organelles, as well as reducing the percentages of growing follicles.

Reprogramming Synthetic Cells for Targeted Cancer Therapy

Advances in synthetic biology enable the reprogramming of bacteria as smart agents to specifically target tumors and locally release anticancer drugs in a highly controlled manner. However, the bench-to-bedside translation of engineered bacteria is often impeded by genetic instability and the potential risk of uncontrollable replication of engineered bacteria inside the patient. SimCells (simple cells) are chromosome-free bacteria controlled by designed gene circuits, which can bypass the interference of the native gene network in bacteria and eliminate the risk of bacterial uncontrolled growth. Here, we describe the reprogramming of SimCells and mini-SimCells to serve as “safe and live drugs” for targeted cancer therapy. We engineer SimCells to display nanobodies on the surface for the binding of carcinoembryonic antigen (CEA), which is an important biomarker found commonly in colorectal cancer cells. We show that SimCells and mini-SimCells with surface display of anti-CEA nanobody can specifically bind CEA-expressing Caco2 cancer cells in vitro while leaving the non-CEA-expressing SW80 cancer cells untouched. These cancer-targeting SimCells and mini-SimCells induced cancer cell death in vitro by compromising the plasma membrane of cancer cells. The cancer-killing effect can be further enhanced by an aspirin/salicylate inducible gene circuit that converts salicylate into catechol, a potent anticancer. This work highlights the potential of SimCells and mini-SimCells for targeted cancer therapy and lays the foundation for the application of synthetic biology to medicine.

Corneal endothelial regeneration in human eyes using endothelium-free grafts

Background

To report on corneal endothelial regeneration, graft clarity, and vision recovery when using endothelium-free grafts.

Methods

We evaluated the donor’s cell viability using trypan blue staining and dual staining with calcein acetoxy methyl ester and ethidium homodimer-1. To preserve eyeball integrity, we performed therapeutic penetrating keratoplasty using cryopreserved donor tissue without endothelium on 195 consecutive patients who suffered from corneal perforation due to progressive primary corneal disease such as herpes simplex keratitis, fungal keratitis, ocular thermal burns, keratoconus, and phlyctenular keratoconjunctivitis. Of these, 18 eyes recovered corneal graft clarity and underwent periodic slit-lamp microscopy, A-scan pachymetry, and in vivo confocal microscopy to observe the clinical manifestations, variations in corneal thickness, and repopulation of the corneal endothelial cells on the donor grafts.

Results

No viable cells were detected in the cryopreserved corneas. After the therapeutic penetrating keratoplasty, notable corneal graft edema was observed in all 18 eyes for 1–4 months, and no corneal endothelial cells were detected on the grafts during this period. Thereafter, we observed gradual and progressive regression and final resolution of the stromal edema, with complete recovery of corneal graft clarity. Through periodic confocal microscopy, we observed the corneal endothelium’s regenerating process, along with single cells bearing multiple nuclei and cell division-like morphology. The regenerated endothelium on the grafts reached a mean cell density of 991 cells/mm². Remarkable vision rehabilitation was achieved in all 18 patients.

Conclusions

We obtained conclusive evidence that host-derived endothelial cells can regenerate a new endothelium over the endothelium-free graft, which possesses normal functions for corneal clarity and vision recovery.

Bioenergetic Analyses of In Vitro and In Vivo Samples to Guide Toxicological Endpoints

Toxicology is a broad field that requires the translation of biochemical responses to xenobiotic exposures into useable information to ensure the safety of the public. Modern techniques are improving rapidly, both quantitatively and qualitatively, to provide the tools necessary to expand available toxicological datasets and refine our ability to translate that data into relevant information via bioinformatics. These new techniques can, and do, impact many of the current critical roles in toxicology, including the environmental, forensic, preclinical/clinical, and regulatory realms. One area of rapid expansion is our understanding of bioenergetics, or the study of the transformation of energy in living organisms, and new mathematical approaches are needed to interpret these large datasets. As bioenergetics are intimately involved in the regulation of how and when a cell responds to xenobiotics, monitoring these changes (i.e., metabolic fluctuations) in cells/tissues post-exposure provides an approach to define the temporal scale of pharmacodynamic responses, which can be used to guide additional toxicological techniques (e.g., "omics"). This chapter will summarize important in vitro assays and in vivo imaging techniques to take real-time measurements. Using this information, our laboratory has utilized bioenergetics to identify significant time points of pharmacodynamic relevance as well as forecast the cell's eventual fate.

Preservation of female genetic resources in feline species

The development of assisted reproduction techniques (ART) specifically for felids has been propagated for two main reasons: (i) most felids are threatened and faced with extinction in all or part of their native habitats (IUCN Red List of Threatened Species, www.catsg.org), and (ii) the domestic cat (Felis catus) can serve as a research model for the implementation of advanced assisted reproductive techniques (ART) to be applied in exotic cats. Domestic cat ovaries can be freshly obtained from veterinary clinics and are frequently used for research on preservation of genetic resources in feline species. The presented review will summarize recent advances and obstacles in biobanking of female genetic resources and discuss alternative approaches which are under investigation.

Preparation and Characterization of Thermoresponsive Poly(N-Isopropylacrylamide) for Cell Culture Applications

Poly(N-isopropylacrylamide) (PNIPAAm) is a typical thermoresponsive polymer used widely and studied deeply in smart materials, which is attractive and valuable owing to its reversible and remote "on-off" behavior adjusted by temperature variation. PNIPAAm usually exhibits opposite solubility or wettability across lower critical solution temperature (LCST), and it is readily functionalized making it available in extensive applications. Cell culture is one of the most prospective and representative applications. Active attachment and spontaneous detachment of targeted cells are easily tunable by surface wettability changes and volume phase transitions of PNIPAAm modified substrates with respect to ambient temperature. The thermoresponsive culture platforms and matching thermal-liftoff method can effectively substitute for the traditional cell harvesting ways like enzymatic hydrolysis and mechanical scraping, and will improve the stable and high quality of recovered cells. Therefore, the establishment and detection on PNIPAAm based culture systems are of particular importance. This review covers the important developments and recommendations for future work of the preparation and characterization of temperature-responsive substrates based on PNIPAAm and analogues for cell culture applications.

Synergistic combination of chemo‑phototherapy based on temozolomide/ICG‑loaded iron oxide nanoparticles for brain cancer treatment

Chemo‑photothermal therapy for cancer treatment has received increasing attention due to its selective therapeutic effects. In the present study, the anticancer effects of drug‑loaded Fe3O4 magnetic nanoparticles (MNPs) by chemo‑photothermal therapy on U‑87 MG human glioblastoma cells was investigated. Anticancer drug‑loaded Fe3O4 MNPs were prepared by loading temozolomide (TMZ) and indocyanine green (ICG), and were characterized by X‑ray diffraction, UV‑vis spectroscopy, thermal gravimetric analysis, transmission electron microscope, as well as drug‑loading capacity. Following treatment with near‑infrared (NIR) light irradiation, the administration of Fe3O4‑TMZ‑ICG MNPs resulted in the apoptosis of U‑87 MG glioblastoma cells through the generation of reactive oxygen species. Western blot analysis and reverse transcription‑quantitative polymerase chain reaction revealed that Fe3O4‑TMZ‑ICG MNPs with NIR laser irradiation lead to significantly enhanced anticancer effects on U‑87 MG glioblastoma cells through the modulation of intrinsic and extrinsic apoptosis genes, including Bcl‑2‑associated X protein, Bcl‑2, cytochrome c, caspase‑3, Fas associated via death domain and caspase‑8. These results suggest that Fe3O4‑TMZ‑ICG MNPs may be potential candidates when administered as chemo‑phototherapy for the treatment of brain cancer.

Intraoviductal concentrations of steroid hormones during in vitro culture changed phospholipid profiles and cryotolerance of bovine embryos

The objective of this study was to evaluate the effect of progesterone (P4), estradiol (E2), and cortisol (CO) at intraoviductal concentrations on bovine embryo development and quality in vitro. After fertilization of in vitro matured oocytes, zygotes were cultured for 8 days in synthetic oviductal fluid, supplemented with 55 ng/ml P4, 120 pg/ml E2, 40 ng/ml CO, or their combination (ALL). Control embryos were cultured with vehicle (0.1% ethanol). Exposure to steroids did not affect the embryo developmental rate nor the mean number of cells per blastocyst. However, at 24 hr after vitrification-warming, exposure to P4 improved the proportion of embryos that re-expanded and were viable while exposure to CO decreased the proportion of viable embryos. By intact cell MALDI-TOF mass spectrometry, a total of 242 phospholipid masses of 400-1000 m/z were detected from individual fresh blastocysts. Exposure to ALL induced the highest and most specific changes in embryo phospholipids, followed by P4, E2, and CO. In particular, the m/z 546.3 and 546.4 attributed to lysophosphatidylcholines were found less abundant after exposure to P4. In conclusion, exposure of bovine embryos to intraoviductal concentrations of steroid hormones did not affect in vitro development but changed blastocyst quality in terms of cryotolerance and phospholipid profiles.

Establishment of an improved vitrification protocol by combinations of vitrification medium for isolated mouse ovarian follicles

In vitro follicle growth (IVFG) is an emerging alternative option for fertility preservation in women instead of ovarian tissue cryopreservation and transplantation. To widen the application of this technique, follicle cryopreservation should be established prior to clinical use. In the present study, we tried to determine the optimal vitrification protocol of mouse ovarian follicle for in vitro culture and oocyte maturation by comparing four different compositions of cryoprotective agents (CPA). Secondary follicles were mechanically isolated from 2-week-old BDF-1 mice and randomly assigned to fresh control and four different groups by the composition of CPAs (ES, EDS, EFS and EPS groups; E: ethylene glycol, D: dimethyl sulfoxide, S: sucrose, F: ficoll, P: 1,2-propanediol (PROH)). After vitrification and warming procedures, the follicles were cultured in vitro for 10 days and then treated with human chorionic gonadotropin and epidermal growth factor to induce oocyte maturation. Fourteen to 16 h later, oocyte maturation and quality were assessed. Follicle viability was evaluated by Calcein-AM/ethidium homodimer-1 staining immediately after warming, and their survival and diameters were measured during follicle culture periods. Antral cavity formation was observed at the end of the culture period (on the 10th day of culture). Following oocyte maturation, its maturational ability and meiotic spindle formation were assessed to evaluate their competence. There was no significant difference in viability after warming among the vitrification groups. From the 8th day of culture, the survival rate of ES and EDS were significantly higher than those of other vitrification groups (EPS and EFS). The follicle diameter was largest in the fresh-control group from the 6th day, while smallest in the EFS with statistical significance. On the 10th day of culture, the antral-cavity formation rate of EDS was comparable to that of the fresh control group. However, the oocyte maturation was significantly decreased in all four vitrification groups when compared with control group; especially, the EFS showed a more marked reduction in the oocyte maturation. There were no significant differences in meiotic spindle formation among all of those groups. Our results suggest that EDS combination for mouse follicle vitrification are the most effective vitrification protocols for mouse follicle and evaluated by an in vitro culture and oocyte maturation after warming.

Cell Counting and Viability Assessment of 2D and 3D Cell Cultures: Expected Reliability of the Trypan Blue Assay

BACKGROUND

Whatever the target of an experiment in cell biology, cell counting and viability assessment are always computed. The Trypan Blue (TB) assay was proposed about a century ago and is still the most widely used method to perform cell viability analysis. Furthermore, the combined use of TB with a haemocytometer is also considered the standard approach to estimate cell population density. There are numerous research articles reporting the use of TB assays to compute cell number and viability of 2D and 3D cultures. However, the literature still lacks studies regarding the reliability of the TB assay in terms of assessment of its repeatability and reproducibility.

METHODS

We compared the TB assay's measurements obtained by two biologists who analysed 105 different samples in double-blind for a total of 210 counts performed. We measured: (a) the repeatability of the count performed by the same operator; (b) the reproducibility of counts performed by the two operators.

RESULTS

There were no significant differences in the results obtained with 2D and 3D cell cultures: we estimated an approximate variability of 5% when the TB assay was used to assess the viability of the culture, and a variability of around 20% when it was used to determine the cell population density.

CONCLUSIONS

The main aim of this study was to make researchers aware of potential measurement errors when TB is used with a haemocytometer for counting and viability measurements in 2D and 3D cultures. We believe that these results can help researchers to determine whether the expected reliability of the TB assay is compliant with their applications.

Reduced competence of immature and mature oocytes vitrified by Cryotop method: assessment by in vitro fertilization and parthenogenetic activation in a bovine model

This study aimed to evaluate the embryo development competence, the nuclear maturation and the viability of germinal vesicle (GV) and metaphase II (MII) oocytes vitrified by the Cryotop method. Cumulus–oocyte complexes were derived from bovine ovaries and three experiments were conducted. In Experiment 1, GV oocytes were vitrified and underwent in vitro maturation (IVM) or not and their nuclear maturation was assessed by orcein staining. In Experiment 2, GV oocytes and MII oocytes were vitrified or not and the viability was assessed by calcein/ethidium homodimer-1 staining. In Experiment 3, MII oocytes matured before or after vitrification were submitted to in vitro fertilization (IVF) and parthenogenetic activation (PA) in order to evaluate embryo development. No difference was found for the nuclear maturation rate in the GV group (50%) and the GV control group (67%; P = 0.23) and for viability rate (56%; 77%; P = 0.055, respectively). However, in the MII group (27%) viability was significantly lower than that of the MII control group (84%; P < 0.0001). The cleavage rate by IVF and PA was similar in the GV group and the MII group. In contrast, vitrified MII oocytes showed no capacity for blastocyst development after IVF or PA and vitrified GV oocytes were able to develop to blastocysts only after PA, but not after IVF. In conclusion, oocyte vitrification by the Cryotop method reduced the capacity for embryo development. Vitrification of GV oocytes, however, did not influence the capacity of meiotic nuclear maturation and they exhibited higher viability following vitrification at the MII stage.

Cryopreservation of ovarian tissue in pediatric patients undergoing sterilizing chemotherapy

Significantly improved survival rates in children and adolescents with cancer have put fertility preservation high on the pediatric oncology agenda. Here we report a retrospective single-center study of 13 years experience of ovarian tissue cryopreservation (OTC) before sterilizing treatment in order to define the safety/benefits of OTC and study clinical/hormonal outcomes in girls. From 2000 to 2013, OTC was performed in 36 girls: eight had non-malignant disease and 28 had malignant disease. Laparoscopy was used to collect a third of each ovary that was frozen by a slow cooling protocol. Indications for OTC were 13 auto-, 19 allo-stem-cell-transplantation and 4 sterilizing chemotherapy. Ovarian tissue harvested by intraumbilical laparoscopy led to no major postoperative complications and did not delay chemotherapy. Histological analysis of ovarian tissue showed an average of 9 primordial follicles/mm(2) [0-83] and no malignant cells were identified. Median post-harvest follow-up was 36 months [1-112]: 26 girls were alive in complete remission and 10 had died. Hormonal results were evaluable for 27 patients (median age 17 yrs [5-26]): 16 patients were in premature ovarian insufficiency. OTC sampling one third of each ovary appears to be an appropriate approach to preserve fertility in children without consequences on subsequent therapeutic program.

Successful slush nitrogen vitrification of human ovarian tissue

OBJECTIVE

To study whether slush nitrogen vitrification improves the preservation of human ovarian tissue.

DESIGN

Control vs. treatment study.

SETTING

University research laboratory.

PATIENT(S)

Ovarian biopsies collected from nine women (aged 14-35 years) during laparoscopic surgery for benign gynecologic conditions.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Ovarian cortical strips of 2 × 5 × 1 mm were vitrified with liquid or slush nitrogen. Fresh and vitrified cortical strips were analyzed for cryodamage and viability under light, confocal, and transmission electron microscopy.

RESULT(S)

Compared with liquid nitrogen, vitrification with slush nitrogen preserves [1] follicle quality (grade 1 follicles: fresh control, 50%; liquid nitrogen, 27%; slush nitrogen, 48%); [2] granulosa cell ultrastructure (intact cells: fresh control, 92%; liquid nitrogen, 45%; slush nitrogen, 73%), stromal cell ultrastructure (intact cells: fresh control, 59.8%; liquid nitrogen, 24%; slush nitrogen, 48.7%), and DNA integrity (TUNEL-positive cells: fresh control, 0.5%; liquid nitrogen, 2.3%; slush nitrogen, 0.4%); and [3] oocyte, granulosa, and stromal cell viability (oocyte: fresh control, 90%; liquid nitrogen, 63%; slush nitrogen, 87%; granulosa cells: fresh control, 93%; liquid nitrogen, 53%; slush nitrogen, 81%; stromal cells: fresh control, 63%; liquid nitrogen, 30%; slush nitrogen, 52%).

CONCLUSION(S)

The histology, ultrastructure, and viability of follicles and stromal cells are better preserved after vitrification with slush nitrogen compared with liquid nitrogen.

Vitrification of human ovarian tissue: a practical and relevant alternative to slow freezing

BACKGROUND

Cryopreservation of ovarian tissue can be used to preserve the fertility of patients who are about to receive treatment(s) that could compromise their future ovarian function. Here we evaluate the effectiveness of a vitrification protocol by carrying out a systematic comparison with a conventional slow-freezing method on human ovarian tissue.

METHODS

Human ovarian samples (mean age 28.0 ± 1.1 years) were processed in parallel for each cryopreservation procedure: vitrification and slow-freezing. Following warming/thawing, histological observations and a TUNEL assay in ovarian follicles were performed and compared to unfrozen control.

RESULTS

Both cryopreservation protocols gave comparable histological outcomes. Percentage of intact follicles was 83.6 % following vitrification in a 1.5 M 1,2-propanediol (PrOH), 1.5 M ethylene glycol (EG) and 0.5 M raffinose solution, 80.7 % after slow-freezing in 1.5 M PrOH and 0.025 M raffinose, and 99.6 % in fresh tissue. Follicle density was unchanged by vitrification (0.6 follicles/mm2) or slow-freezing (0.5 follicles/mm2) compared to fresh tissue (0.7 follicles/mm2). Percentage of follicles with DNA fragmentation was not statistically different in vitrified (20.8 %) or slow-frozen (31.3 %) tissues compared to the unfrozen control (35.0 %). There was no difference in proportion of stroma cells with DNA fragmentation in vitrified (6.4 %) and slow-frozen (3.7 %) tissues compared to unfrozen tissue (4.2 %).

CONCLUSIONS

This vitrification protocol enables good preservation of ovarian quality post-warming. The evaluation of endocrine function after vitrification need to be perform in a higher cohort to evaluate if this protocol may offer a relevant alternative to conventional slow-freezing for the cryopreservation of human ovarian tissue.

Effects of neutral red assisted viability assessment on the cryotolerance of isolated bovine preantral follicles

PURPOSE

Fertility preservation strategies warrant non-invasive viability assessment of preantral follicles (PAF) such as staining with Neutral Red (NR) that is incorporated by viable follicles. To optimize the procedure, we firstly determined the lowest concentration and shortest exposure time needed for optimal viability screening of isolated bovine PAF. Secondly, we combined this protocol to a vitrification procedure to assess cryotolerance of the stained follicles.

METHODS

Isolated PAF (900, divided over 6 replicates) were cultured in DMEM/Ham's F12 (Culture Medium - Cm) for 4 days (38.5 °C, 5% CO2). On D0, D2 and D4, follicles were stained, by adding NR medium (NRm = Cm with different concentrations NR) after which viability was assessed by counting stained/non-stained PAF every 30 min for a period of 2 h.

RESULTS

Following a binary logistic regression analysis with staining as a result (yes/no) versus log-concentration, a probability model could be fitted, indicating that the proportion of stained follicles remained stable after 30 min when 15 μg/ml NR was used, without compromising follicular health and viability. Consequently, using this protocol, no significant effect of staining prior to vitrification, was found on PAF viability immediately after warming or following 4 days of culture.

CONCLUSIONS

In conclusion, we propose NR staining as a non-invasive, non-detrimental viability assessment tool for PAF, when applied at 15 μg/ml for 30 min, being perfectly compatible with PAF vitrification.

Efficacy of ovarian tissue cryopreservation in a major European center

PURPOSE

To evaluate the effect of cryopreservation and thawing of ovarian tissue from oncological patients opting for fertility preservation on ovarian tissue viability.

METHODS

In this prospective cohort study, the ovarian tissue viability before and after cryopreservation and thawing was measured for 25 newly diagnosed oncological patients who had their ovarian tissue cryopreserved. Outcome measures were follicle integrity (histology), follicle viability (Calcein viability assay), steroid hormone production (estradiol and progesterone production in vitro) and overall tissue viability (glucose uptake in vitro). This study was conducted at a Cryobank for storage of ovarian tissue in a university hospital.

RESULTS

Cryopreserved/thawed ovarian tissue showed a decreased glucose uptake when compared to tissue that had not been cryopreserved. In addition, a diminished E2 and P4 production was observed after cryopreservation and thawing, despite the fact that numbers of viable follicles as determined by the Calcein viability assay were comparable. Histological examination revealed a higher percentage of degenerated follicles after cryopreservation and thawing.

CONCLUSIONS

Ovarian tissue cryopreservation and thawing impairs the viability of ovarian tissue in oncological patients opting for fertility preservation.

Quality and functionality of human ovarian tissue after cryopreservation using an original slow freezing procedure

PURPOSE

To evaluate the efficiency of an original slow freezing protocol on the quality and function of human ovarian cortex.

METHODS

Human ovarian tissues were cryopreserved using a freezing medium supplemented with propanediol and raffinose as cryoprotectants and antioxidants (L-glutamine, taurine). Samples were then frozen using a faster cooling rate than the usual one. Viability and morphology of follicles, DNA fragmentation in follicles and stroma as well as histology of the vascular endothelium were analyzed before and after freezing/thawing. Moreover, a functional analysis was performed based on the evaluation of follicular growth and development in thawed ovarian tissues that were cultured in vitro.

RESULTS

Our freezing/thawing protocol allows preservation of a high proportion of viable follicles and the preservation of the different follicle developmental stages (p>0.05 versus fresh control). 70.5 ± 5.2 % of follicles retained an intact morphology after cryopreservation (p=0.04). Stroma cells but not follicles exhibited a slight increase of DNA fragmentation after thawing (p<0.05). Microvessel endothelium within thawed tissues appeared to be preserved. Granulosa cells showed signs of proliferation in follicles cultured for 12 days. Secretion of 17β-oestradiol significantly increased during in vitro culture.

CONCLUSIONS

This protocol leads to good preservation of ovarian integrity and functionality post-thawing and thus appears as a suitable technique of ovarian tissue cryopreservation in clinical settings. Further research could be extended to optimize conditions of in vitro culture.