Post-thaw Outcomes Research Articles

Proline pre-conditioning of Jurkat cells improves recovery after cryopreservation.

Cell therapies such as allogenic CAR T-cell therapy, natural killer cell therapy and stem cell transplants must be cryopreserved for transport and storage. This is typically achieved by addition of dimethyl sulfoxide (DMSO) but the cryoprotectant does not result in 100% cell recovery. New additives or technologies to improve their cryopreservation could have major impact for these emerging therapies. l-Proline is an amino acid osmolyte produced as a cryoprotectant by several organisms such as the codling moth Cydia pomonella and the larvae of the fly Chymomyza costata, and has been found to modulate post-thaw outcomes for several cell lines but has not been studied with Jurkat cells, a T lymphocyte cell line. Here we investigate the effectiveness of l-proline compared to d-proline and l-alanine for the cryopreservation of Jurkat cells. It is shown that 24-hour pre-freezing incubation of Jurkat cells with 200 mM l-proline resulted in a modest increase in cell recovery post-thaw at high cell density, but a larger increase in recovery was observed at the lower cell densities. l-Alanine was as effective as l-proline at lower cell densities, and addition of l-proline to the cryopreservation media (without incubation) had no benefit. The pre-freeze incubation with l-proline led to significant reductions in cell proliferation supporting an intracellular, biochemical, mechanism of action which was shown to be cell-density dependent. Controls with d-proline were found to reduce post-thaw recovery attributed to osmotic stress as d-proline cannot enter the cells. Preliminary analysis of apoptosis/necrosis profiles by flow cytometry indicated that inhibition of apoptosis is not the primary mode of action. Overall, this supports the use of l-proline pre-conditioning to improve T-cell post-thaw recovery without needing any changes to cryopreservation solutions nor methods and hence is simple to implement.

Improving post-thaw outcomes in primary human hepatocyte cryopreservation

Improving post-thaw outcomes in primary human hepatocyte cryopreservation

Is pre-freeze sperm preparation more advantageous than post-freeze?

SummaryHuman sperm cryopreservation is characterised to this day by sub-optimal success rates. Interestingly, a traditional approach to improving post-thaw outcome has been to integrate standard sperm preparation techniques into freezing protocols as a means of selecting sperm with the highest fertilisation potential prior to insemination. However, no consensus has been reached yet regarding the optimal timing (before or after freezing) of this selection step. Following analysis of a total of 20 human semen samples, which were divided into two aliquots prepared by density gradient centrifugation either before or after freezing, this study demonstrated higher post-thaw total (P < 0.0001), progressively motile (P = 0.005) and vital (P < 0.0001) sperm counts for frozen-prepared semen samples. The present study suggests that direct insemination with frozen-prepared sperm with minimal intervening post-thaw processing might be a more advantageous approach to current clinical practices, particularly for donor and patient intrauterine insemination programmes. Further research into cryopreservation-induced coiled sperm tail morphology is also warranted.Lay summaryFreezing and storing of sperm in liquid nitrogen (’sperm cryopreservation') is the current method of choice for preserving the fertility of a wide scope of men. Nevertheless, sub-optimal sperm survival is still associated with traditional cryopreservation methods, namely 'slow freezing', and may affect fertility treatment success rates. Interestingly, a widely applied approach for selecting high-quality sperm before treatment has been to incorporate 'sperm preparation' techniques, such as density gradient centrifugation, in slow freezing protocols. There is, however, an ongoing debate regarding which is the optimal timing of this selection step: before or after freezing. In this study, we collected 20 human semen samples which were divided into two portions and subjected to density gradient centrifugation either before or after freezing. Post-thaw semen analyses demonstrated significantly improved sperm counts (P < 0.05) when density gradient centrifugation was performed before freezing, thus suggesting this approach to be more advantageous for current clinical practices.

28 Evaluation invitro of two protocols of vitrification from alpaca (Vicugna pacos) embryos

The reproductive efficiency of South American camelids as the alpaca is low, with a few number of animals having a good genetic characteristic. The transfer of cryopreserved embryos has great potential to disseminate valuable genetic, but the suitable protocol for such cryopreservation still needs to be developed. In this study, two protocols of vitrification of alpaca embryos were tested. Day 6.5 post-mating, embryos (n=66) were recovered from 14 female alpacas through a non-surgical technique and classified according to the characteristics of old world camelids reported by Skidmore et al. 2004 (Reprod. Fertil. Dev. 16, 605–609). Only quality 1 and 2 embryos were used for the study. They were placed together in 50-µL drops of holding medium for 30min and transferred to a 100-µL drop of equilibration solution 1, consisting of 7.5% (v/v) ethylene glycol (EG) + 0.25M sucrose. After 1min, embryos were transferred to equilibration solution 2, consisting of 15% (v/v) EG + 0.5M sucrose. After 2min, embryos were transferred into 2 consecutive drops of vitrification solutions A [SA: 30% (v/v) EG + 1M sucrose] for 20s each, then in 2 other drops of vitrification solution B [SB: 30% (v/v) EG + 3% glycerol + 1M sucrose] for 20s each. Thereafter, embryos were quickly loaded into open pulled straws (OPS) in a volume of 10µL and then plunged into liquid nitrogen. For warming, the OPS were held in air for 5s and subsequently thawed at 37°C for 50s. Straws were emptied into 1mL of prewarmed holding medium solution (HMS1) containing 1M sucrose for wash and the thawed blastocysts were transferred into a second 1mL of prewarmed HMS1. After 5min incubation at 37°C, the blastocysts were transferred into 1mL of warmed Holding medium solution 2 (HMS2) containing 0.5M sucrose maintained at room temperature (∼24°C) for evaluation. Data were analysed by the Chi-squared test. Post-thaw embryo expansion results were 81.3% and 58.8% for SA and SB (P&amp;lt;0.05), respectively. Post-thaw embryo quality (1 and 2) were found at 62.5% and 29.1% with SA and SB, respectively (P&amp;lt;0.05). In conclusion, the vitrification of alpaca embryos with the ethylene glycol:sucrose solution results in better post-thaw outcomes than the ethylene glycol:sucrose:glycerol. Further experiments with embryo transfer are needed. This research was funded by FONDECYT project no. 149-2017.

Post-Thaw Culture and Measurement of Total Cell Recovery Is Crucial in the Evaluation of New Macromolecular Cryoprotectants.

The storage and transport of cells is a fundamental technology which underpins cell biology, biomaterials research, and emerging cell-based therapies. Inspired by antifreeze and ice-binding proteins in extremophiles, macromolecular (polymer) cryoprotectants are emerging as exciting biomaterials to enable the reduction and/or replacement of conventional cryoprotective agents such as DMSO. Here, we critically study post-thaw cellular outcomes upon addition of macromolecular cryoprotectants to provide unambiguous evidence that post-thaw culturing time and a mixture of assays are essential to claim a positive outcome. In particular, we observe that only measuring the viability of recovered cells gives false positives, even with non-cryoprotective polymers. Several systems gave apparently high viability but very low total cell recovery, which could be reported as a success but in practical applications would not be useful. Post-thaw culture time is also shown to be crucial to enable apoptosis to set in. Using this approach we demonstrate that polyampholytes (a rapidly emerging class of cryoprotectants) improve post-thaw outcomes across both measures, compared to poly(ethylene glycol), which can give false positives when only viability and short post-thaw time scales are considered. This work will help guide the discovery of new macromolecular cryoprotectants and ensure materials which only give positive results under limited outcomes can be quickly identified and removed.

Ultra-low shipping temperatures for cell therapies

Background & Aim Cell therapies require a cold chain delivery as part of the production and delivery process. Whether following an autologous or allogeneic route, a common workflow for manufacturing cell therapies consists of collecting a cell sample from a healthy donor or a patient, cryopreserving and shipping it to a manufacturing site for engineering purposes, cryopreserving the resulting therapeutic product and shipping it to a clinical site for thaw and patient administration. Cryopreservation enables extended shelf-life of cell products and facilitates the logistics. Cryogenic shipping has typically been undertaken using a dry shipper, a vessel containing some liquid nitrogen (LN2) to ensure that the product being shipped remains below approximately -150°C. The precise limits for safe transportation are however poorly understood, with variations methods and temperatures reported, between transport in liquid nitrogen (-196°C), to transport on dry ice (-80°C). This study examined the impact of transferring samples from stable ultra-low temperatures and storing for 5 and 10 days at -120°C, -100°C, -80°C, and -60°C before transfer back to ultra-low temperature storage to mimic the effect of shipping at lower temperatures. Methods, Results & Conclusion Two common cell lines were tested, Jurkats (immortalized human t cell line), and HepG2s (hepatocarcinoma). It was found that while -120°C transfer has no impact on post-thaw outcome, temporary storage temperatures above -120°C resulted in reduced post-thaw function and viable cell number. The reduction in post-thaw outcome was lower after 10 days’ storage compared with 5 days’ storage at all temperatures >-120°C, with the higher the temperature the greater the reduction in post-thaw function and viable cell number. For the transport of cellular therapies, we conclude that the temperature must be maintained at or below -120°C for optimal post-thaw outcome when cryopreserving with a DMSO based cryoprotectant.

Key events during the cryopreservation of t cells

Background & Aim Slow, controlled cooling is essential for successful cryopreservation of t cells. In practice, samples are typically cooled at a controlled rate of around 1°C min−1 before being transferred at around -80°C to -100°C. However, other than dehydration, the physical and biological events occurring as the temperature is lowered in t cells (and mammalian cells more widely) have been under-studied. Placing samples in the liquid or vapor phase of nitrogen too early could result in rapid cooling rates, leading to intracellular ice formation and cell death. However, there is little basis in the literature for setting the controlled cooling endpoint at -80°C or below. The present work explored the critical physical and biological events during the cooling of t cells (immortalized jurkat t cell line) through a combination of biological and physical measurements (Differential Scanning Calorimetry and Fourier transformed Infra-Red Spectroscopy). Methods, Results & Conclusion During cooling in a VIA Freeze controlled rate freezer, cells were seen to undergo a membrane transition from a liquid crystal to a gel state at -1.0°C ± 0.8°C. Ice nucleation occurred at -7.7°C ± 1.4°C in 1mL cryovials and was characterized by a rapid release of heat and macroscopic solidification of the sample. Cells dehydrate on cooling after ice nucleation to remain in osmotic equilibrium with the extra-cellular channels between ice crystals. A further transition was observed using DSC at -46.9°C ± 1.3°C. This transition was only present in cryovials during cooling when cells were present and is an intracellular glass transition. The intracellular glass transition temperature corresponded to the cells becoming osmotically inactive, reaching their maximally dehydrated state. Biologically samples following controlled cooling and plunged into liquid nitrogen below this temperature showed good post-thaw outcome, whereas samples plunged into liquid nitrogen above this point had substantial reduction in post-thaw viability and function. An extracellular glass transition at -123°C was observed and below this temperature samples could be safely stored and shipped. These results suggest that controlling cooling until -47°C is reached in t cells is critical for a successful cryopreservation, and no biological advantage is conferred by further cooling. Shorter controlled-rate cooling cycles could thus safely be applied, saving time and potentially allowing more cryopreservation cycles to be completed a day.

Cryopreservation of Andalusian donkey (Equus asinus) spermatozoa: Use of alternative energy sources in the freezing extender affects post-thaw sperm motility patterns but not DNA stability

The aim of this study was to compare the effect of three sugars and Equex paste in a freezing extender for donkey sperm cryopreservation. Ejaculates (n = 18) were collected from six Andalusian donkeys of proven fertility were pooled (two ejaculates per pool) and cryopreserved using a freezing extender containing three different sugars (glucose, fructose and sorbitol), with or without the addition of Equex paste. Sperm quality was assessed before and after freezing-thawing for motility, morphology, plasma membrane integrity, acrosome integrity and DNA integrity. The use of sorbitol in the freezing extender improved total and progressive sperm motility (P < 0.05) and amplitude of lateral head displacement (P < 0.01), but it reduced the values for other sperm motility variables compared with glucose (P < 0.001). The use of fructose resulted in a reduction in values for most CASA variables (P < 0.05), whereas addition of Equex paste did not have any beneficial effect on values for these variables (P > 0.05). Glucose was more effective in maintaining sperm morphology (P < 0.05), while there was no beneficial effect with the addition of Equex paste (P > 0.05). Supplementation of fructose and Equex paste in the freezing extender decreased plasma membrane integrity (P < 0.05) as compared with glucose, but there were no differences between treatments for acrosome and DNA integrity (P > 0.05), even after 24 h of incubation. The use of different sugar sources in the extender could affect the in vitro post-thaw quality of cryopreserved donkey spermatozoa, with sorbitol being an interesting alternative for improving the sperm quality. Results of the present study indicate the use of Equex paste could negatively affect post-thaw outcomes for sperm viability in this species.

Spatial considerations during cryopreservation of a large volume sample

There have been relatively few studies on the implications of the physical conditions experienced by cells during large volume (litres) cryopreservation – most studies have focused on the problem of cryopreservation of smaller volumes, typically up to 2 ml.This study explores the effects of ice growth by progressive solidification, generally seen during larger scale cryopreservation, on encapsulated liver hepatocyte spheroids, and it develops a method to reliably sample different regions across the frozen cores of samples experiencing progressive solidification.These issues are examined in the context of a Bioartificial Liver Device which requires cryopreservation of a 2 L volume in a strict cylindrical geometry for optimal clinical delivery. Progressive solidification cannot be avoided in this arrangement. In such a system optimal cryoprotectant concentrations and cooling rates are known. However, applying these parameters to a large volume is challenging due to the thermal mass and subsequent thermal lag. The specific impact of this to the cryopreservation outcome is required.Under conditions of progressive solidification, the spatial location of Encapsulated Liver Spheroids had a strong impact on post-thaw recovery. Cells in areas first and last to solidify demonstrated significantly impaired post-thaw function, whereas areas solidifying through the majority of the process exhibited higher post-thaw outcome. It was also found that samples where the ice thawed more rapidly had greater post-thaw viability 24 h post-thaw (75.7 ± 3.9% and 62.0 ± 7.2% respectively).These findings have implications for the cryopreservation of large volumes with a rigid shape and for the cryopreservation of a Bioartificial Liver Device.

Post-thaw outcomes of rare or very low counts of cryopreserved sperm

Post-thaw outcomes of rare or very low counts of cryopreserved sperm

A scale down process for the development of large volume cryopreservation

The process of ice formation and propagation during cryopreservation impacts on the post-thaw outcome for a sample. Two processes, either network solidification or progressive solidification, can dominate the water–ice phase transition with network solidification typically present in small sample cryo-straws or cryo-vials. Progressive solidification is more often observed in larger volumes or environmental freezing. These different ice phase progressions could have a significant impact on cryopreservation in scale-up and larger volume cryo-banking protocols necessitating their study when considering cell therapy applications.This study determines the impact of these different processes on alginate encapsulated liver spheroids (ELS) as a model system during cryopreservation, and develops a method to replicate these differences in an economical manner.It was found in the current studies that progressive solidification resulted in fewer, but proportionally more viable cells 24h post-thaw compared with network solidification. The differences between the groups diminished at later time points post-thaw as cells recovered the ability to undertake cell division, with no statistically significant differences seen by either 48h or 72h in recovery cultures.Thus progressive solidification itself should not prove a significant hurdle in the search for successful cryopreservation in large volumes. However, some small but significant differences were noted in total viable cell recoveries and functional assessments between samples cooled with either progressive or network solidification, and these require further investigation.

Liposome encapsulated soy lecithin and cholesterol can efficiently replace chicken egg yolk in human semen cryopreservation medium

Cryopreservation of spermatozoa plays a significant role in reproductive medicine and fertility preservation. Chicken egg yolk is used as an extender in cryopreservation of human spermatozoa using glycerol egg yolk citrate (GEYC) buffered medium. Even though 50% survival of spermatozoa is generally achieved with this method, the risk of high levels of endotoxins and transmission pathogens from chicken egg yolk is a matter of concern. In the present study we attempted to establish a chemically defined cryopreservation medium which can replace the chicken egg yolk without affecting sperm survival. Ejaculates from 28 men were cryopreserved with GEYC based freezing medium or liposome encapsulated soy lecithin-cholesterol based freezing medium (LFM). The semen samples were subjected to rapid thawing after 14 days of storage in liquid nitrogen. Post-thaw analysis indicated significantly higher post-thaw motility and sperm survival in spermatozoa cryopreserved with LFM compared to conventional GEYC freezing medium. The soy lecithin and cholesterol at the ratio of 80:20 with sucrose showed the highest percentage of post-thaw motility and survival compared to the other compositions. In conclusion, chemically defined cryopreservation medium with liposome encapsulated soy lecithin and cholesterol can effectively replace the chicken egg yolk from human semen cryopreservation medium without compromising post-thaw outcome.

Semen cryopreservation for men banking for oligospermia, cancers, and other pathologies: prediction of post-thaw outcome using basal semen quality

To evaluate post-thawing sperm parameters in a large series of men cryopreserving for different cancers and oligospermia. Retrospective observational study. Semen cryopreservation laboratory. Six hundred twenty-three patients undergoing semen cryopreservation for cancer or oligospermia who discontinued banking. None. Postcryopreservation sperm motility and viability. In oligospermic men, recovery of motile sperm after cryopreservation was possible in only a few out of the 219 samples cryopreserved for this problem. Similarly, independent of the reason for which cryopreservation was required, if one basal semen parameter fell below the 5th percentile of the World Health Organization reference values, recovery of motile and viable spermatozoa after thawing was low. Among samples cryopreserved for cancer, those with testicular cancer showed the lowest basal semen quality and recovery after thawing. In cases of hematological cancers or other types of cancers, motility recovery was similar to that of non-cancer-related samples. Receiver operating characteristic analyses demonstrate that basal progressive and total motility predict the recovery rate of motile sperm after thawing with high accuracy, sensibility and specificity. Our study demonstrates the ability of prefreeze semen parameters to predict cryosurvival in terms of sensitivity and precision. Using this information, the clinician could perform appropriate counseling about the future possibilities of fertility for the patient.

Mitochondria and membrane cryoinjury in micropatterned cells: Effects of cell–cell interactions

The maintenance of cell membrane integrity is an absolute minimum criterion for the selection of a successful cryopreservation process; however, it is often used as the sole determinant of cell “viability”. Membrane stresses and strains that develop with cell volume fluctuations are only one component of the overall cellular response to freezing. Damage to organelles resulting from excessive concentration of intracellular solutes and/or the alternation of molecular signalling events may affect post-thaw outcomes. As the low temperature response of cells is affected by the presence of cell–cell interactions, the cryopreservation of tissues and tissue model systems would benefit from a more detailed understanding of the sites and mechanisms of cryoinjury. The purpose of this study was to examine the relationship between mitochondria and plasma membrane damage in frozen micropatterned cells and to identify the role of cell–cell interactions. Madin Darby Canine Kidney cells (MDCK) were micropatterned using a polydimethylsiloxane (PDMS) elastomeric stamp to create non-adhesive regions of agarose on untreated glass substrates. Five different cell arrangements were used to examine the effect of cell–cell contact: single cells, cell doublets, linear arrangement of cells, randomly arranged cells and confluent monolayers. Cells were cooled in a programmable alcohol bath at 1 °C/min to −40 °C after extracellular ice nucleation at −5 °C. Post-thaw plasma membrane integrity and mitochondria depolarization were determined using trypan blue and the lipophilic, cyanine derivative JC-1, respectively. alamarBlue was used to assess the post-thaw metabolic activity of the cell arrangements. We found that the incidence of plasma membrane damage and mitochondria integrity increased with decreasing temperature and was dependent on the degree of cell–cell interaction. Mitochondria damage was evident in cells that displayed intact plasma membranes, however this injury could be reversed in the micropatterned cells that are exposed to suprazero temperatures. The results from this study suggest that the exclusive use of membrane integrity as a measure of cell “viability” does not consider subcellular injury that may contribute to delayed recovery and/or cell death following low temperature exposures.

Soy lecithin replaces egg yolk for cryopreservation of human sperm without adversely affecting postthaw motility, morphology, sperm DNA integrity, or sperm binding to hyaluronate

Semen specimens (one ejaculate from each of 20 consenting study participants) were subjected to routine semen analysis, an in vitro sperm binding assay (HBA), and a sperm chromatin dispersion assay (HaloSperm), both before and after cryopreservation using cryoprotectant media supplemented with either egg yolk or soy lecithin. Comparing the equivalency of the two phospholipid cryopreservation supplements with regard to postthaw functional parameters demonstrated that there were no statistically significant differences between the two supplements for [1] recovery of motile sperm, [2] maintenance of sperm cell morphology, [3] maintenance of the ability of sperm to bind to hyaluronate in vitro, or [4] maintenance of sperm DNA integrity.

Artificial collapse of mouse and human blastocysts prior to vitrification

Vitrification technology may become the method of choice for human embryo cryopreservation. In our clinical IVF laboratory we have noted better pregnancy outcome data with embryos vitrified at cleavage verus the blastocyst stage. Artificial collapse of blastocysts prior to vitrification has been postulated to improve post-thaw outcomes. The purpose of this study was to assess the impact of artificial collapse with either mechanical puncture or laser on post-thaw survival and development of vitrified mouse and human blastocysts.

P-205: Cryopreservation of mouse and human oocytes by vitrification

The potential of oocyte cryopreservation has yet to be realized. The mature metaphase II oocyte because of it’s large size, water content and chromosomal structure has been very difficult to freeze with methodology developed for embryo freezing. The purpose of this study was to investigate new cryotechnology for oocyte cryopreservation and to develop oocyte-specific modifications to facilitate and enhance post-thaw outcomes.

A Molecular Basis of Cryopreservation Failure and its Modulation to Improve Cell Survival

The requirement for more effective cryopreservation (CP) methodologies in support of the emerging fields of cell bioprocessing and cell therapy is now critical. Current CP strategies appropriately focus on minimizing the damaging actions of physicochemical stressors and membrane disruption associated with extra- and intracellular ice formation that occurs during the freeze-thaw process. CP protocols derived from this conceptual paradigm, however, yield suboptimal survival rates. We now provide the first report on the identification of delayed-onset cell death following CP and the significance of modulating molecular biological aspects of the cellular responses (apoptosis) to low temperature as an essential component to improve postthaw outcome. In this study we quantitatively examined the molecular basis of cell death associated with CP failure in a canine renal cell model. In addition, we report on the significant improvement in CP outcome through the modulation of these molecular mechanisms by the utilization of an organ preservation solution. HypoThermosol. Further, the utilization of HypoThermosol as the preservation medium and the modulation of molecular-based cell death have led to a paradigm shift in biologic preservation methodologies. The recognition of molecular mechanisms associated with CP-induced cell death offers the promise of improved CP of more complex and/or fragile biological systems such as stem cells, engineered tissues, and human organs.