Vitrification Solution Research Articles

First report on cryopreservation of mature shoot tips of two avocado (Persea americana Mill.) rootstocks

Cryopreservation combined with in vitro culture offers a safe and cost-effective method to conserve germplasm. Conservation of Persea spp. has been limited to heterozygous somatic embryos that are not true-to-type. A method for shoot-tip cryopreservation is vital to preserve the exact gene pool of interest. For the first time cryopreservation protocols for mature shoot tips of two avocado cultivars (cvs) ‘Velvick’ and ‘Reed’, were established. In vitro shoots were subjected to two different optimised pre-treatments; (1) cv ‘Velvick’—high sucrose (0.3 M) or (2) cv ‘Reed’—low temperature (10 °C) incubation, over a 2-week period prior shoot tip dissection. Two different plant vitrification solutions, plant vitrification solution 2 (PVS2) and vitrification solution L (VSL) were tested at 0 °C for 0, 10, 20, 30 and 40 min. Vitrified shoots were evaluated for survival and regrowth at 2 and 8 weeks after vitrification treatment and either with or without liquid nitrogen exposure. The study revealed that the optimal exposure time for each cultivar varied with the cryoprotectant used. After liquid nitrogen cv ‘Velvick’ highest regrowth levels were observed with 20 min exposure to either PVS2 or VSL, however, vigorous plants were produced only from VSL treated shoots. In the case of cv ‘Reed’ highest regrowth levels were observed with 10 min exposure to PVS2 however only morphologically normal plants were recovered from VSL treated shoots. Cryopreservation of avocado shoot tips was successful using PVS2 and VSL with both recording similar recovery rates for ‘Velvick’ and ‘Reed’; although only vigorous and morphologically normal plants were developed from VSL treatments.

Shoot Tip Cryopreservation of Lamprocapnos spectabilis (L.) Fukuhara Using Different Approaches and Evaluation of Stability on the Molecular, Biochemical, and Plant Architecture Levels.

The aim of this study is to optimize and evaluate the effectiveness of vitrification, droplet-vitrification, and encapsulation-vitrification techniques in the cryopreservation of Lamprocapnos spectabilis (L.) Fukuhara ‘Gold Heart’, a popular medicinal and ornamental plant species. In vitro-derived shoot tips were used in the experiments. All three techniques were based on explant dehydration with plant vitrification solution 3 (PVS3; 50% glycerol and 50% sucrose) for 0, 30, 60, 90, 120, 150, or 180 min. The recovered microshoots were subjected to morphometric, biochemical, and molecular analyses (RAPD, ISSR, SCoT). The highest recovery level was reported with the encapsulation-vitrification protocol based on 150 min dehydration (73.1%), while the vitrification technique was the least effective (maximum 25.8% recovery). Explants cryopreserved with the encapsulation-vitrification technique produced the highest mean number of shoots (4.9); moreover, this technique was optimal in terms of rooting efficiency. The highest fresh weight of shoots, on the other hand, was found with the vitrification protocol based on a 30-min PVS3 treatment. The concentrations of chlorophyll a and b were lower in all cryopreservation-derived plants, compared to the untreated control. On the other hand, short dehydration and cryopreservation of non-encapsulated explants stimulated the synthesis of anthocyanins. A small genetic variation in 5% of all samples analyzed was detected by RAPD and ISSR marker systems. Only plants recovered from the encapsulation-vitrification protocol had no DNA sequence alternations.

Cryopreservation of seeds of Melocactus zehntneri Braun ex Ritter f. and Cereus gounellei Luetzelb ex Schum k. by the vitrification method

The Brazilian Caatinga houses a number of cacti species, which are considered endangered due to human influence. Two of them, Melocactus zehntneri Braun ex Ritter f. and Cereus gounellei Luetzelb ex Schum k., are endemic of the Brazilian Caatinga. Cryopreservation can provide a means for long-term preservation of endangered plant material. The aim of this study was to evaluate the efficiency of cryoprotectants for the cryopreservation of seeds from these two ­species. The treatments consisted of immersing seeds in different cryoprotectant solutions and vitrification solutions before storage in liquid nitrogen (NL) at -196 °C, as follows: T1- Control: no cryoprotectants; T2- PVS2 (10 min), T3- PVS2 + phloroglucinol 1% (10 min), T4- PVS2 (10 min) + Supercool 1%; T5- PVS2 + phloroglucinol 1% (10 min) + Supercool 1%. Seed germination was evaluated after cryopreservation. The experimental design was completely randomized with five treatments and five replicates per treatment. Seed moisture at the beginning of the experiment was 6.2% for M. zehntneri and 7.8% for C. gounellei. There were no statistically significant differences for the seed germination percentage among the different treatments. Therefore, we concluded that seed of these two cacti species can be cryopreserved directly without the need for cryoprotectant solutions.

Direct cryopreservation of winter-acclimated buds of Dracocephalum austriacum (Lamiaceae) from field material

This study develops protocols for the micropropagation and cryopreservation of Dracocephalum austriacum (Lamiaceae). It is a perennial herbaceous plant that overwinters with ground-level sprouts and is classified as critically endangered in Europe. In vitro cultures were initiated from seeds on growth-regulator-free Murashige & Skoog (MS) medium after nicking the seed coat. Propagation via shoot culture was achieved on ½ MS medium with 1 µM benzyl adenine (BAP). Rooting on various indole-3-butyric acid (IBA)-media was not reliable, but the rooting success was 80% after 10 weeks on medium with 1 µM BAP. Two starting materials underwent cryopreservation: (1) shoot tips from cold-acclimated in vitro plantlets and (2) axillary buds from winter shoots from field plants. For the cryopreservation of in vitro shoots, plant vitrification solution (PVS)3 and incubation over ice yielded the best results (~ 34% regeneration success). However, regeneration using winter acclimated buds were 100, 76 and 30% for collections in December, February and March, respectively, using the same protocol. Moreover, the ploidy levels of cryopreserved plantlets were estimated using flow cytometry. The use of winter-acclimated field material of temperate herbaceous plants or subshrubs has high potential as explant source for cryopreservation and calls for exploring this technique for other species.

Successful vitrification of dromedary camel embryos using a novel embryo vitrification kit

Embryos (n = 87) collected 8 days after mating and 7 days after ovulation were vitrified using a camel-specific vitrification kit. Vitrification solutions (VS) containing 20% foetal calf serum, with or without 2% bovine serum albumin (BSA) were used to cryopreserve embryos, in three steps VS1 (5 min), VS2 (5 min) and VS3 (30−35 s) at room temperature (RT) before being loaded into open pulled straws and immediately frozen in liquid nitrogen. Embryos were subsequently thawed in warming solutions (WS) in three steps: WS1 at 37 °C (1 min), WS2 at RT (5 min) then into holding media at RT (5−60 min) prior to transfer, in pairs, into recipient camels 6 days after ovulation. There were 42 of 43 embryos viable after vitrification in media without BSA and these were subsequently transferred into 21 recipient females which resulted in ten pregnancies 60 days after transfer (48% pregnancy rate). There were 38 of 44 viable embryos vitrified in media containing BSA that were transferred in pairs into 19 recipient females which resulted in five pregnancies 60 days after transfer (26% pregnancy rate; P > 0.05). Of the total 15 foetuses that developed to 60 days of gestation after vitrification, 11 resulted from embryos of 200–499 μm diameter and four from embryos of 500–700 μm diameter (P > 0.05). There were encouraging results with use of this novel vitrification kit for the commercial application of cryopreservation of camel embryos with a diameter of 300–550 μm.

Cryopreservation of Pleione bulbocodioides (Franch.) Rolfe protocorm-like bodies by vitrification

In this study, a vitrification cryopreservation system for the protocorm-like bodies of monolingual orchids was successfully established and the factors involved in cryopreservation by vitrification, including preculture, loading, cryoprotection, cooling, rewarming, and recovery, were investigated. Histological observation, biochemical and genetic analyses were carried out in every step. The results revealed a high survival rate of 93.33% when the protocorm-like bodies were precultured in 0.4 M sucrose for 2 days, then loaded in 50% plant vitrification solution 2 (15% glycerin, 7.5% ethylene glycol, 7.5% dimethyl sulfoxide, 7.5% sucrose and 62.5% liquid MS) at 25 °C for 40 min, and subsequently treated with modified PVS (25% glycerin, 15% ethylene glycol, 2% polyethylene glycol, 13% dimethyl sulfoxide, 15% sucrose and 30% liquid MS) at 0 °C for 50 min, which improved the vitrification efficiency. The samples were rewarmed directly in a water bath at 60 °C for 2 min after storage in liquid nitrogen. The PLBs were then transferred to a solid medium with 1.0 mg L⁻¹ 6-benzyl adenine, 0.2 mg L⁻¹α-naphthylacetic acid, and 0.5 g L⁻¹ activated charcoal. The PLBs were maintained in the dark for 3 weeks before growth in the light in a culture room. Biochemical analyses revealed that the content of soluble protein and sugar increased during the early stage but decreased during cryopreservation. Histological analyses displayed visible nuclei, few damaged cells, and denser cytoplasm in the cryopreserved PLBs. Inter-simple sequence repeat molecular marker analysis revealed no genetic changes in vitrified PLBs, validating the use of this protocol as an efficient long-term conservation option for this species.

Effects of Different Vitrification Solutions and Protocol on Follicular Ultrastructure and Revascularization of Autografted Mouse Ovarian Tissue.

Objective Many attempts have been made to preserve fertility by improving the cryopreservation of the ovarian tissue. This current studyaimed to improve of direct cover vitrification (DCV) protocol on follicular preservation and angiogenesis in autografted ovarian tissue. Materials and Methods In this experimental study, sixty five female Balb/c mice (5-6 week-old) were anesthetized and their ovaries were dissected. The left ovaries were vitrified by DCV solution, thawed by descending concentrations of sucrose, and then autografted subcutaneously. The right ovaries were autografted with no vitrification procedure prior to transplantation. The animals were sacrificed under anesthesia on the 7thday after transplantation to obtain ovarian tissue. Follicular quality was assessed by histological and ultrastructure observations, and angiogenesis was examined by immunohistochemical staining and real-time polymerase chain reaction (PCR) analysis. Results The histological and ultrastructure features of the follicles preserved well after vitrification of the ovarian tissue by 10% ethylene glycol (EG) and 10% dimethyl sulfoxide (DMSO). Revascularizationwas manifested prominently in the DCV1-vitrified/grafted ovaries by von Willebrand factor (vWF) and alpha smooth muscle actin (α-SMA) immunostaining. The ovarian tissue vitrified in DCV1 protocol had higher expression levels of angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF) 7 days after autotransplantation (P<0.01). ConclusionThese findings suggest that DCV with 10% of both EG and DMSO, is an effective cryopreservation solution for preservation of good quality follicles as well an upregulation of angiogenic factors after ovarian tissue transplantation.

Standardization of vitrification treatments for safe cryo-conservation of banana (Musa acuminata Colla) cultivars using differential scanning calorimetry

Cryo-conservation is the most promising approach and reliable method for long term conservation of banana and plantain genetic resources. Prior to the development of a safe cryo-conservation procedure for highly hydrated tissues of any vegetatively propagated crop species such as banana, suitable vitrification treatments involving loading solution in combination with Plant Vitrification Solution 2 (PVS2) solution have to be standardized. In the present study, Differential Scanning Calorimetry (DSC) technique was attempted to identify the best vitrification treatment using shoot apices as storage explants in two banana cultivars namely Grand Naine and Red banana. The results showed that DSC thermogram curves detected the formation of ice nucleation at a temperature of -18.67°C for Grand Naine and -19.16°C for Red banana in the control shoot apices. Among the sixteen vitrification treatment combinations tested, the treatments, LP6, LP7, LP10, LP11, LP14 and LP15 were judged as best treatments for cryo-conservation of both banana cultivars as revealed by the formation of glass transition events in the vitrified shoot apices. This information obtained through DSC experiments would further provide scope for designing safe cryo-conservation system for banana. This is the first report to demonstrate the application of DSC to optimize the vitrification treatments that would be adopted for developing cryo-conservation protocol for Musa germplasm.

Amorphous state stability of plant vitrification solutions

Two critical factors for obtaining high viable biological samples after cryopreservation by vitrification method are cryoprotectant glass-forming ability while cooling and the stability of its amorphous state during warming. The present work is devoted to the study of the amorphous state stability of plant vitrification solutions (PVS) by differential scanning calorimetry method. The objects of the study were PVS1 modified, PVS2, PVS3 modified, PVS4 and PVSN. The thermograms of PVSs, frozen in liquid nitrogen, were recorded at a warming rate of 0.5 deg/min. The glass transition temperatures of PVS1, PVS2 and PVS3 were –109.0°C, –115.3°C, and –93.9°C, respectively. Neither exo- nor endothermic peaks have been recorded, indicating no crystallization, at the cooling and the warming stages. PVS4 and PVSN thermograms, besides glass transition (–111.5°C and –110.0°C, correspondingly), showed crystallization from the amorphous state (devitrification) and ice melting peaks. Crystallization enthalpy of PVSN was 2.8 times higher compared to PVS4. This fact testifies that the crystalline phase was larger in PVSN compared to PVS4. It should be noted that crystallization in PVS4 and PVSN may be related to the low warming rate used during the experiment. At higher warming rates, this crystallization is likely to be avoided. Thus, PVS1, PVS2 and PVS3 have a high glass-forming ability and a stabile amorphous state. The amorphous state stability of PVS4 and PVSN is significantly lower compared to PVS1, PVS2, and PVS3.

Advances in cryopreservation of vanilla (Vanilla planifolia Jacks.) shoot-tips: assessment of new biotechnological and cryogenic factors

The effect of dehydration, cryopreservation, and reculture conditions on growth recovery (%) of vanilla (Vanilla planifolia) shoot-tips was evaluated using a D-cryoplate procedure. Tissues were excised from in vitro grown plantlets, preconditioned on MS semisolid medium supplemented with 0.15 M trehalose for 1 d, loaded in a solution of 0.4 M sucrose or trehalose and 2 M glycerol for 30 min, and dehydrated within a laminar flow cabinet for various durations (30, 60, 90, 120, 150, and 180 min). The same preconditioning and loading treatments were compared using dehydration with vitrification solutions (PVS2 or PVS3) for 30 min at room temperature according to droplet-vitrification and V-cryoplate methods. The highest (33%) recovery of cryopreserved shoot-tips was achieved using the D-cryoplate method after 0.15 M trehalose preconditioning, loading with sucrose-glycerol solution and desiccation for 180 min. DSC analyses revealed that the osmotically active water (OAW) content of the shoot-tips was reduced from 77% (fresh weight basis) to 17% after the only effective drying duration (180 min). Melting endotherms indicated that crystallization events accompanied cryopreservation of the tissues. Proliferation of multiple shoots was obtained by indirect organogenesis. Histological analysis of the explants during post-cryopreservation recovery confirmed the organogenic nature of the callus formed after 3–4 mo of reculture in the dark on semisolid multiplication medium. This was followed by a secondary organogenesis on MS medium with kinetin (2 mg L−1) and exposure to a photoperiod. At present, this is the most optimized cryopreservation protocol for shoot-tips of V. planifolia.

Vitrified Human Umbilical Arteries as Potential Grafts for Vascular Tissue Engineering.

The development of a biological based small diameter vascular graft (d < 6mm), that can be properly stored over a long time period at - 196°C, in order to directly be used to the patients, still remains a challenge. In this study the decellularized umbilical arteries (UAs) where vitrified, evaluated their composition and implanted to a porcine model, thus serving as vascular graft. Human UAs were decellularized using 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and sodium dodecyl sulfate (SDS) detergents. Then, vitrified with vitrification solution 55 (VS55) solution, remained for 6months in liquid nitrogen and their extracellular matrix composition was compared to conventionally cryopreserved UAs. Additionally, total hydroxyproline, sulphated glycosaminoglycan and DNA content were quantified in all samples. Finally, the vitrified umbilical arteries implanted as common carotid artery interposition graft to a porcine animal model. Decellularized and vitrified UAs characterized by proper preservation of extracellular matrix proteins and tissue architecture, whereas conventionally cryopreserved samples exhibited a disorganized structure. Total hydroxyproline content was preserved, although sulphated glycosaminoglycan and DNA contents presented significantly alterations in all samples. Implanted UAs successfully recellularized and remodeled as indicated by the histological analysis. Decellularized and vitrified UAs retained their structure function properties and can be possible used as an alternative source for readily accessible small diameter vascular grafts.

The harmful effect of removing the extracellular vitrification medium during embryo cryopreservation using a nylon mesh device in rabbit

During the last decades, many techniques have been developed to reduce sample volume and improve cooling and warming rates during embryo vitrification. The vast majority are based on the “minimum drop size” concept, in which the vitrification solution around embryos is reduced by aspiration, leaving a tiny part of volume surrounding embryos. However, novel cryodevices were aimed to remove the entire vitrification solution. This study was designed to compare the “minimum drop size” technique using Cryotop® with the nylon mesh as cryodevice on rabbit morula embryos. The outcomes assessed were the in vitro development rates (experiment 1) and the offspring rates at birth (experiment 2). Embryos were vitrified in a two-step procedure; equilibrium (10% EG + 10% Me2SO) for 2 min and vitrification (20% EG + 20% Me2SO) for 1 min. In experiment 1, embryos (n = 323) were warmed and subsequently in vitro cultured for 48 h to assess the embryo developmental capability to reach the hatching-hatched blastocyst stage. In experiment 2, embryos were transferred using the laparoscopic technique (n = 369) to assess the offspring rate at birth. In this context, rates of in vitro embryo development were similar between vitrified groups (0.73 ± 0.042% and 0.66 ± 0.047% for Cryotop® and nylon mesh device, respectively), but lower than in the fresh group (0.97 ± 0.016%, p < 0.05). In experiment 2, there were no significant differences in survival rates (offspring born/total embryos transferred) among the Cryotop® device group and fresh group (0.41 ± 0.049% and 0.49 ± 0.050%, respectively). But significantly lower value was obtained in the nylon mesh device group (0.18 ± 0.030%). These results indicate that nylon mesh is not suitable as cryodevice for rabbit morula vitrification, remaining those using the “minimum drop size” methodology as the best option.

Droplet-vitrification cryotherapy for eradication of apple stem grooving virus and apple stem pitting virus from “Marubakaido” apple rootstock

The apple stem grooving virus (ASGV) and apple stem pitting virus (ASPV) are among the major viral species that infect apple trees and are responsible for substantial damage and loss. The aim of this study was to assess the effectiveness of droplet-vitrification cryotherapy technique in eradication of ASGV and ASPV in Malus prunifolia “Marubakaido” apple rootstock plants. The axillary shoot tips were excised from ASGV- and ASPV-infected plants and incubated for one day on preculture medium. Subsequently, they were exposed to plant vitrification solution 2 (PVS2) for 0, 20, 40, 50, 60 or 80 min at 22 °C and immersed in liquid nitrogen for 1 h. Cryopreserved shoot tips had the highest survival (75 and 65%) and regrowth (53 and 58%) percentages with PVS2 exposure duration of 20 and 40 min, respectively. After six months of growth in a greenhouse, RT-PCR analyses revealed that all the tested plants were free of ASPV and 70% were free of ASGV. The high eradication percentage of ASGV and ASPV indicated that the droplet-vitrification cryotherapy technique is an effective tool to produce ASGV- and ASPV-free propagating material of “Marubakaido” apple rootstock.

Grey poplar explant acclimation to improvethe dehydration tolerance and cryopreservation

Cryostorage techniques have been developed to preserve the most valuable genotype from an endangered native population of Populus × canescens Aiton Sm. (grey poplar), which is located in the floodplain forest in the South Moravia region of the Czech Republic and which is difficult to propagate using cuttings. The prevailing genotype with valuable traits was selected by the simple sequence repeats method. This genotype was used to determine the most effective pre-cultivation conditions (cold hardening, and cold hardening combine with osmotic treatment) on dehydration tolerance and post-thaw recovery of the grey poplar shoot tips. The pre-cultivation and application of a modified plant vitrification solution 3 (PVS3) considerable reduced the freezable water content in shoot tips. Evaluation after eight weeks of regrowth revealed that simultaneous effect of cold and osmotic pre-treatments and application of PVS3 for 120 min enabled 93.3 ± 5.8 % recovery. The results emphasize the importance of the pre-cultivation conditions, which significantly improved the post-thaw recovery of the grey poplar explants.

Y2SK2- and SK3-type dehydrins from Agapanthus praecox act as protectants to improve plant cell viability during cryopreservation

The cryopreservation of plants through vitrification prevents ice damage by bringing the plants to a glassy state for cryogenic storage. Most angiosperm seeds are dehydrated to extremely low levels of their original water content, accumulate late embryogenesis abundant (LEA) proteins, and greatly increase their cytoplasmic viscosity, thereby reaching a glassy state during maturation. In this study, two LEA family recombinant dehydrin (DHN) proteins (Y2SK2 and SK3) from Agapanthus praecox, when added to the plant vitrification solution, were found to double the survival rate of Arabidopsis thaliana seedlings after cryopreservation. Evans blue staining revealed that the Y2SK2 and SK3 proteins decreased the damage to the plasma membranes of plant cells during cryopreservation. Furthermore, the Y2SK2 and SK3 proteins significantly decreased the malondialdehyde and H2O2 contents, increased the glutathione (GSH) content, and downregulated NADPH oxidase (RbohA) in A. thaliana seedlings. Thus, these DHNs may reduce excessive reactive oxygen species production and membrane lipid peroxidation damage under the complex stresses of cryopreservation. Additionally, Y2SK2 can effectively enhance peroxidase activity and catalase2 (CAT2) expression levels; SK3 obviously improved ascorbic acid (AsA) content, as well as Cu/Zn superoxide dismutase (Cu/Zn-SOD) and ascorbate peroxidase 5 (APX5) expression in plant cells and enhanced H2O2 scavenging capacity by promoting the activity of the AsA-GSH cycle. These findings suggested that Y2SK2 and SK3, the DHNs added at the dehydration step, can relieve cell cryoinjury by inducing high antioxidant levels and positive oxidative stress responses and act as protectants, improving plant cell viability after cryopreservation. Application of dehydrins optimization plant cryopreservation protocol, dehydrins can significantly improve complex stress damage and enhance the cell viability from cryopreservation.

The presence of synthetic polymers in the maturation medium affects the cryotolerance and developmental capacity after parthenogenic activation of vitrified goat oocytes

The purpose of this present study is to assess if addition of the synthetic polymers in maturation medium can influence cryotolerance and subsequently embryonic development of mammalian oocytes. We examined the roles of two polymers, including polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), on in vitro maturation (IVM), embryonic developmental capacity, and cryotolerance of goat oocytes. The present study includes two parts. At first, goat cumulus−oocyte complexes (COCs) were matured in a medium supplemented with 10% fetal bovine serum (FBS), 3 mg/ml PVP, or 1 mg/ml PVA, respectively. Data of oocyte with first polar body, cleavage, and blastocyst following parthenogenetic activation (PA) were recorded. Secondly, after maturation in the above medium, oocytes were vitrified using the Cryotop technique and then the morphology, cleavage and blastocyst formation of vitrified oocytes have been checked. The results demonstrated that the adding of PVP or PVA in maturation medium can't affect IVM of goat oocytes in comparison with FBS, as concern cumulus cell expansion, first polar body formation, and embryonic development. Additionally, without plunging into liquid nitrogen, only exposure to the vitrification and warming solutions cannot also influence the quality of oocytes, in terms of morphology, cleavage, and blastocyst formation. However, after IVM with synthetic polymers and vitrification, the ratio of oocytes with standard morphology in PVP or PVA group was only 59.47% ± 3.56% or 54.86% ± 5.19%, respectively, and was significantly less than that in the FBS group (89.37% ± 4.52%, P < 0.05). Furthermore, the cleavage ratio of oocytes in PVP or PVA group was 37.41% ± 4.17% or 27.71% ± 3.91% and was considerably less than that in the FBS group (64.97% ± 4.69%, P < 0.05). In addition, the cleavage ratio in PVP group was statistically higher than that in PVA group (P < 0.05). In terms of blastocyst development, a significant difference was observed between the synthetic polymer group and the FBS group (24.96% ± 3.62%, P < 0.05). However, the blastocyst ratio in the PVA group (7.51% ± 1.68%) was statistically less than the PVP groups (13.20% ± 4.59%, P < 0.05) and the FBS group (P < 0.05). In conclusion, two potential serum replacements, either PVP or PVA, can support IVM and embryonic development of goat oocytes at the concentration used in this study. But IVM with synthetic polymers supplemented to maturation medium may reduce the cryotolerance of oocytes. Additionally, the supportive function of PVP on embryonic development of vitrified oocytes might be better than that of PVA.

Silk fibroin sheet multilayer suitable for vitrification of in vitro-matured bovine oocytes

Minimum volume cooling (MVC) procedure has been successfully applied to vitrify mammalian oocytes, but high skill of capillary pipetting is required to load the oocytes on a cryodevice with a minimal volume (<1 μL) of vitrification solution (VS). Here we report a novel cryodevice for bovine oocyte vitrification, silk fibroin (SF) sheet multilayer, of which spontaneous absorption property can eliminate pipette operation for removal of excess VS. Based on physical stability and scanning electron microscopic observation, the SF sheet prepared from 1.5% (wt/vol) fibroin solution was selected and layered around a polypropylene strip (0.1-mm thickness, 0.7-mm width, 10-mm depth). Ten denuded bovine mature oocytes were loaded onto the SF sheet multilayer with 2–3 μL of the VS, and then cooled rapidly by plunging into liquid nitrogen. Nylon mesh (NM) device with square opening 37-μm length of a side and commercially available Cryotop® (CT) device were used as controls, and the minimization of VS volume was performed by paper towel absorption and capillary aspiration, respectively. In SF, NM and CT groups, post-warming oocyte recovery rates were 99.5, 99.1 and 100%, and the morphological survival rates were 99.7, 94.5 and 99.0%, respectively. Subsequent IVF and 8-days IVC resulted in comparable blastocyst yields among the three groups (25.5, 25.0 and 26.1% in SF, NM and CT groups, respectively). These results suggest that SF sheet multilayer is a useful cryodevice for bovine matured oocytes in MVC vitrification because VS volume surrounding the oocytes can be easily minimized through its absorption property.

Cryopreservation of shoot apices and callus cultures of globe artichoke using vitrification method

BackgroundCryogenic cooling became a crucial tool for the storage of heterozygous plants such as globe artichoke. This study was carried out to optimize a reliable method for in vitro cryopreservation of shoot apices and callus cultures of globe artichoke using dimethylsulfoxide (DMSO) and Plant Vitrification Solutions 2 (PVS2) as cryoprotectant solutions. Shoot apices were exposed to DMSO or PVS2 for 20, 40, 60, and 80 min prior to plunge in liquid nitrogen (LN). ResultsIt was found that using PVS2 as a cryoprotectant in cryopreservation of shoot apices of globe artichoke was more effective compared with using of DMSO alone. Among the exposure time tested, 60 min gave the best results of survival. The highest survival (60%), regeneration (56%), and proliferated shootlets (4.30) were obtained after cryoprotection with PVS2 for 60 min. Regarding callus cultures, the maximum values of fresh weights and subsequently growth value of recovered callus were registered with 40 min followed by 60 min exposure time. Related to the type of the tested cryoprotectants, the best survival and growth parameters of the cryopreserved callus cultures were obtained with PVS2 treatments. Treatment with PVS2 for 40 min registered the highest survival observations of cryopreserved callus. Also, the maximum values of fresh weight (1.30 g) and growth value (4.20) were obtained with 40 min exposure time. Microscopy analysis presented as cell morphology revealed that the treatment of PVS2 40% was the optimum for cell growth of cryopreserved callus of globe artichoke. ConclusionThe results demonstrated that using PVS2 as a cryoprotectant in cryopreservation of shoot apices and callus cultures of globe artichoke was more effective compared with DMSO.

Use of synthetic polymers improves the quality of vitrified caprine preantral follicles in the ovarian tissue

The aim of this study was to evaluate whether the addition of synthetic polymers to the vitrification solution affected follicular morphology and development and the expression of Ki-67, Aquaporin 3 (AQP3) and cleaved Caspase-3 proteins in ovarian tissue of the caprine species. Caprine ovaries were fragmented and two fragments were immediately fixed (Fresh Control) for morphological evaluation, while other two were in vitro cultured for 7 days (Cultured Control) and fixed as well. The remaining fragments were distributed in two different vitrification groups: Vitrified and Vitrified/Cultured. Each group was composed of 4 different treatments: 1) Sucrose (SUC); 2) SuperCool X-1000 0.2 % (X-1000); 3) SuperCool Z-1000 0.4 % (Z-1000) or 4) with polyvinylpyrrolidone K-12 0.2 % (PVP). Also, Fresh Control, Cultured Control, SUC and X-1000 were destined to immunohistochemical detection of Ki-67, AQP3 and cleaved Caspase-3 proteins. Morphologically, the treatment with X-1000 showed no significant difference with the Fresh Control group and was superior to the other treatments. After the cleaved caspase-3 analysis, X-1000 showed the lowest percentages of strong immunostaining while Cultured Control showed the highest. Also, a positive correlation was found between the percentages of degenerated follicles and the percentages of strong staining intensity follicles. Regarding the AQP3 analysis, the highest percentages of strong AQP3 staining intensity were found in X-1000. In conclusion, we have demonstrated that the addition of the synthetic polymer SuperCool X-1000 to the vitrification solution improved the current vitrification protocol of caprine ovarian tissue.

Antioxidants increase blastocyst cryosurvival and viability post-vitrification.

What is the effect of antioxidants acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid (A3) in vitrification and warming solutions on mouse blastocyst development and viability? The combination of three antioxidants in vitrification solutions resulted in mouse blastocysts with higher developmental potential in vitro and increased viability as assessed by both an outgrowth model in vitro and fetal development following uterine transfer. The antioxidant combination of acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid present in IVF handling and embryo culture media has significant beneficial effects on mouse embryo and fetal development, especially under oxidative stress. The study was a laboratory-based analysis of an animal model. Rapid cooling through vitrification was conducted on F1 mouse blastocysts, with antioxidants (A3) supplemented in vitrification and/or warming solutions, followed by culture and embryo transfer. Pronucleate oocytes were collected and cultured in groups to Day 4 blastocysts. Expanded blastocysts were vitrified and warmed in solutions with and without the A3 antioxidants and cultured for a further 24h. Blastocyst cell number and allocation, apoptosis and histone acetylation levels were all quantified, and viability through outgrowths and transfers assessed. Mouse blastocysts vitrified with no antioxidants had significantly lower cell numbers (P < 0.001) and higher apoptotic cells (P < 0.05) compared to non-vitrified embryos. Addition of combined A3 antioxidants to the vitrification and warming solutions resulted in a significant increase in inner cell mass cell (ICM) number (P < 0.001) and total cell number (P < 0.01), and an increase in outgrowth area (P < 0.05), which correlated with the increased fetal weight (P < 0.05), crown rump length (P < 0.05) and limb development (P < 0.05) determined following transfer compared to embryos with no antioxidants. Furthermore, while blastocyst vitrification significantly reduced acetylation levels (P < 0.05) compared to non-vitrified embryos, the inclusion of A3 antioxidants helped to ameliorate this. Embryo development was only examined in the mouse. Results in this study demonstrate that vitrification and warming of blastocysts have significant detrimental effects on embryo histone acetylation and subsequent viability. The presence of antioxidants in the vitrification solutions helps to alleviate the negative effects of cryopreservation. Our data indicate that antioxidants need to be present in the medium at the time of exposure to increased oxidative stress associated with vitrification and that prior exposure (i.e. during culture or IVF alone) is insufficient to protect cells against cryo-induced injury. Hence, A3 antioxidants may assist in maintaining the viability of vitrified human embryos in ART through the reduction of oxidative stress. This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.