Cryopreservation: An emerging paradigm change

Effort in manual operation of reproductive health cryostorage facilities

RESEARCH QUESTION

What areas of manual IVF cryostorage operations are common to the safe operation of IVF cryostorage facilities and require effort from embryologists?

DESIGN

Observational time and motion data were collected by two observers equipped with the digital cameras over 2 weeks at four well-characterized US IVF centres (sites α, β, γ and δ) from 12 participants performing cryostorage tasks. To understand the work processes of the different sites and assist in the data analysis, informal interviews were conducted with the study participants and laboratory directors. Data were analysed to identify work processes that might be eliminated or diminished by automation and software improvements.

RESULTS

On average, it took 3.4 data record queries per retrieval from cryostorage to identify a cane, while the canister was lifted an average of 1.5 times per retrieval, with a mean 11.8 ± 9.2 s per lift. Of the total time spent working with cryostorage equipment, 47.25% was of a fatiguing nature. Sites α, β and γ utilized one person to fill the liquid nitrogen storage Dewars, while site δ had two technicians working in tandem to move and fill the Dewars, with different frequencies and determination factors for refills and efficiencies.

CONCLUSIONS

This time and motion study demonstrated significant time investment, task redundancy and fatiguing working conditions among embryologists using manual cryostorage processes. There was a disparity of processes and space capacity across different laboratories. Some of these issues may be addressed by the integration of automation and technology solutions.

Exploring the effect of platelet-rich plasma on vascularization and survival of follicles in xenotransplanted human ovarian tissue

RESEARCH QUESTION

Do platelet-rich plasma (PRP) products, specifically human platelet lysate (hPL) and umbilical cord plasma, enhance vascularization and follicular survival in human ovarian tissue transplanted to immunodeficient mice?

DESIGN

Human ovarian tissue was transplanted to subcutaneous pockets in nude mice, followed by daily injections for 6 days of PRP or saline at the transplantation sites. After a grafting period of 3 and 6 days, vascularization was assessed using CD-31 quantification, and gene expression of angiogenic markers (VEGF/Vegf) together with apoptosis-related genes (BAX/BCL-2), oxidative stress markers (HMOX-1/Hmox-1) and pro-inflammatory markers (Il-1β/Il-6/Tnf-α) was quantitively analysed. Follicle density was analysed in the grafts after 4 weeks. Additionally, a pilot study was conducted exploring the suitability of ultrasound scanning for assessing survival and vascularization in ovarian tissue xenografted to mice.

RESULTS

Although there was a significant increase in the CD-31 area from day 3 to day 6 post-grafting, there were no significant differences between the hPL and control groups. Gene expression analysis revealed significant down-regulation of VEGF from day 3 to day 6 for both the hPL and control groups, and significant up-regulation of BAX/BCL-2 in the hPL group compared with the controls. The follicle density showed no significant differences in the hPL group and UCP groups compared with the controls. Furthermore, ultrasound biomicroscopy provided valuable insights into graft morphology, necrotic areas and blood flow, suggesting its potential as a monitoring tool.

CONCLUSIONS

Despite the angiogenic properties of PRP, this study was unable to demonstrate a significant impact of hPL on vascularization or of hPL and UCP on follicular survival in xenotransplanted human ovarian tissue.

Optimisation of cryopreservation conditions, including storage duration and revival methods, for the viability of human primary cells

BACKGROUND

Cryopreservation is a crucial procedure for safeguarding cells or other biological constructs, showcasing considerable potential for applications in tissue engineering and regenerative medicine.

AIMS

This study aimed to evaluate the effectiveness of different cryopreservation conditions on human cells viability.

METHODS

A set of cryopreserved data from Department of Tissue Engineering and Regenerative Medicine (DTERM) cell bank were analyse for cells attachment after 24 h being revived. The revived cells were analysed based on different cryopreservation conditions which includes cell types (skin keratinocytes and fibroblasts, respiratory epithelial, bone marrow mesenchymal stem cell (MSC); cryo mediums (FBS + 10% DMSO; commercial medium); storage durations (0 to > 24 months) and locations (tank 1-2; box 1-5), and revival methods (direct; indirect methods). Human dermal fibroblasts (HDF) were then cultured, cryopreserved in different cryo mediums (HPL + 10% DMSO; FBS + 10% DMSO; Cryostor) and stored for 1 and 3 months. The HDFs were revived using either direct or indirect method and cell number, viability and protein expression analysis were compared.

RESULTS

In the analysis cell cryopreserved data; fibroblast cells; FBS + 10% DMSO cryo medium; storage duration of 0-6 months; direct cell revival; storage in vapor phase of cryo tank; had the highest number of vials with optimal cell attachment after 24 h revived. HDFs cryopreserved in FBS + 10% DMSO for 1 and 3 months with both revival methods, showed optimal live cell numbers and viability above 80%, higher than other cryo medium groups. Morphologically, the fibroblasts were able to retain their phenotype with positive expression of Ki67 and Col-1. HDFs cryopreserved in FBS + 10% DMSO at 3 months showed significantly higher expression of Ki67 (97.3% ± 4.62) with the indirect revival method, while Col-1 expression (100%) was significantly higher at both 1 and 3 months compared to other groups.

CONCLUSION

In conclusion, fibroblasts were able to retain their characteristics after various cryopreservation conditions with a slight decrease in viability that may be due to the thermal-cycling effect. However, further investigation on the longer cryopreservation periods should be conducted for other types of cells and cryo mediums to achieve optimal cryopreservation outcomes.

Small RNA and Freeze Survival: The Cryoprotective Functions of MicroRNA in the Frozen Muscle Tissue of the Grey Tree Frog

The grey tree frog, Dryophytes versicolor, survives whole-body freezing for weeks during cold winter months. Survival in a state devoid of available food, water, or oxygen forces a reliance on metabolic rate depression (MRD) and the reprioritization of bodily functions. This study utilizes next-generation sequencing (NGS) and bioinformatic analyses to characterize changes in the microRNAome of D. versicolor. When comparing control to frozen groups, five microRNAs (miRNA) were found to be differentially regulated (miR-143-3p, miR-30e-3p, miR-10a-5p, miR-140-3p, and miR-148a-3p), suggesting that they play key roles in freeze survival. The KEGG and GO analyses of these changes predicted a significant negative enrichment of terms associated with cell proliferation and active metabolism while simultaneously predicting the upregulation of cell signalling terms. These results suggest a fast-acting regulatory role for miRNA in contributing to the reorganization of gene expression and the limitation of energy-expensive processes during MRD in the hind leg skeletal muscle of the frog.

Cryopreservation-induced delayed injury and cell-type-specific responses during the cryopreservation of endothelial cell monolayers

The cryopreservation of endothelial cell monolayers is an important step that bridges the cryopreservation of cells in suspension to that of tissues. Previous studies have identified clear distinctions in freezing mechanisms between cells in suspension and in monolayers, as well as developed novel protocols for monolayer cryopreservation. Recently, our group has shown that human umbilical vein endothelial cell (HUVEC) and porcine corneal endothelial cell (PCEC) monolayers grown on Rinzl plastic substrate can be cryopreserved in 5% dimethyl sulfoxide, 6% hydroxyethyl starch, and 2% chondroitin sulfate, following a slow-cooling protocol (-1 °C/min) with rapid plunge into liquid nitrogen from -40 °C. However, membrane integrity assessments were done immediately post thaw, which may result in an overestimation of cell viability due to possible delayed injury responses. Here, we show that for the optimal protocol condition of plunge at the -40 °C interrupt temperature, HUVEC and PCEC monolayers exhibited no significant immediate post-thaw injuries nor delayed injury responses during the 24-h post-thaw overnight culture period. HUVEC monolayers experienced no significant impact to their natural growth rate during the post-thaw culture, while PCEC monolayers experienced significantly higher growth than the unfrozen controls. The difference in the low-temperature responses between HUVEC and PCEC monolayers was further shown under high temperature plunge conditions. At these suboptimal plunge temperatures, HUVEC monolayers exhibited moderate immediate membrane injury but a pronounced delayed injury response during the 24-h post-thaw culture, while PCEC monolayers showed significant immediate membrane injury but no additional delayed injury response during the same period. Therefore, we provide further validation of our group's previously designed endothelial monolayer cryopreservation protocol for HUVEC and PCEC monolayers, and we identify several cell-type-specific responses to the freezing process.

Mesenchymal stromal cells derived from various tissues: Biological, clinical and cryopreservation aspects: Update from 2015 review

Mesenchymal stromal cells (MSCs) have become one of the most investigated and applied cells for cellular therapy and regenerative medicine. In this update of our review published in 2015, we show that studies continue to abound regarding the characterization of MSCs to distinguish them from other similar cell types, the discovery of new tissue sources of MSCs, and the confirmation of their properties and functions that render them suitable as a therapeutic. Because cryopreservation is widely recognized as the only technology that would enable the on-demand availability of MSCs, here we show that although the traditional method of cryopreserving cells by slow cooling in the presence of 10% dimethyl sulfoxide (Me2SO) continues to be used by many, several novel MSC cryopreservation approaches have emerged. As in our previous review, we conclude from these recent reports that viable and functional MSCs from diverse tissues can be recovered after cryopreservation using a variety of cryoprotectants, freezing protocols, storage temperatures, and periods of storage. We also show that for logistical reasons there are now more studies devoted to the cryopreservation of tissues from which MSCs are derived. A new topic included in this review covers the application in COVID-19 of MSCs arising from their immunomodulatory and antiviral properties. Due to the inherent heterogeneity in MSC populations from different sources there is still no standardized procedure for their isolation, identification, functional characterization, cryopreservation, and route of administration, and not likely to be a "one-size-fits-all" approach in their applications in cell-based therapy and regenerative medicine.

Impact of cryopreservation on elastomuscular artery mechanics

Low temperatures slow or halt undesired biological and chemical processes, protecting cells, tissues, and organs during storage. Cryopreservation techniques, including controlled media exchange and regulated freezing conditions, aim to mitigate the physical consequences of freezing. Dimethyl sulfoxide (DMSO), for example, is a penetrating cryoprotecting agent (CPA) that minimizes ice crystal growth by replacing intracellular water, while polyvinyl alcohol (PVA) is a nonpenetrating CPA that prevents recrystallization during thawing. Since proteins and ground substance dominate the passive properties of soft biological tissues, we studied how different freezing rates, storage temperatures, storage durations, and the presence of cryoprotecting agents (5% [v/v] DMSO + 1 mg/mL PVA) impact the histomechanical properties of the internal thoracic artery (ITA), a clinically relevant blood vessel with both elastic and muscular characteristics. Remarkably, biaxial mechanical analyses failed to reveal significant differences among the ten groups tested, suggesting that mechanical properties are virtually independent of the cryopreservation technique. Scanning electron microscopy revealed minor CPA-independent delamination in rapidly frozen samples, while cryoprotected ITAs had better post-thaw viability than their unprotected counterparts using methyl thiazole-tetrazolium (MTT) metabolic assays, especially when frozen at a controlled rate. These results can be used to inform ongoing and future studies in vascular engineering, physiology, and mechanics.

Mesenchymal stromal cells for improvement of cardiac function following acute myocardial infarction: a matter of timing

Acute myocardial infarction (AMI) is the leading cause of cardiovascular death and remains the most common cause of heart failure. Reopening of the occluded artery, i.e., reperfusion, is the only way to save the myocardium. However, the expected benefits of reducing infarct size are disappointing due to the reperfusion paradox, which also induces specific cell death. These ischemia-reperfusion (I/R) lesions can account for up to 50% of final infarct size, a major determinant for both mortality and the risk of heart failure (morbidity). In this review, we provide a detailed description of the cell death and inflammation mechanisms as features of I/R injury and cardioprotective strategies such as ischemic postconditioning as well as their underlying mechanisms. Due to their biological properties, the use of mesenchymal stromal/stem cells (MSCs) has been considered a potential therapeutic approach in AMI. Despite promising results and evidence of safety in preclinical studies using MSCs, the effects reported in clinical trials are not conclusive and even inconsistent. These discrepancies were attributed to many parameters such as donor age, in vitro culture, and storage time as well as injection time window after AMI, which alter MSC therapeutic properties. In the context of AMI, future directions will be to generate MSCs with enhanced properties to limit cell death in myocardial tissue and thereby reduce infarct size and improve the healing phase to increase postinfarct myocardial performance.

Downscaling platelet cryopreservation: Are platelets frozen in tubes comparable to standard cryopreserved platelets?

BACKGROUND

Platelet cryopreservation extends the shelf-life to at least 2 years. However, platelets are altered during the freeze/thaw process. Downscaling platelet cryopreservation by freezing in tubes would enable rapid screening of novel strategies to improve the quality of cryopreserved platelets (CPPs). The aim of this study was to characterize the effect of freezing conditions on the in vitro phenotype and function of platelets frozen in a low volume compared to standard CPPs.

METHODS

Platelets were prepared for cryopreservation using 5%-6% DMSO and processed using standard protocols or aliquoted into 2 mL tubes. Platelets were hyperconcentrated to 25 mL (standard CPPs) or 200 μL (tubes) before freezing at -80°C (n = 8). Six insulators/controlled rate freezing containers were used to vary the freezing rate of platelets in tubes. Platelets were thawed, resuspended in plasma, and then assessed by flow cytometry and thromboelastography.

RESULTS

The use of different insulators for tubes changed the freezing rate of platelets compared to platelets frozen using the standard protocol (p < .001). However, this had no impact on the recovery of the platelets (p = .87) or the proportion of platelets expressing GPIbα (p = .46) or GPVI (p = .07), which remained similar between groups. A lower proportion of platelets frozen in tubes externalized phosphatidylserine compared to standard CPPs (p < .001). The clot-forming ability (thromboelastography) of platelets was similar between groups (p > .05).

CONCLUSION

Freezing platelets in tubes modified the freezing rate and altered some platelet characteristics. However, the functional characteristics remained comparable, demonstrating the feasibility of downscaling platelet cryopreservation for high-throughput exploratory investigations.

Elevated fucose content enhances the cryoprotective performance of anionic polysaccharides

Biological cryopreservation often involves using a cryoprotective agent (CPA) to mitigate lethal physical stressors cells endure during freezing and thawing, but effective CPA concentrations are cytotoxic. Hence, natural polysaccharides have been studied as biocompatible alternatives. Here, a subset of 26 natural polysaccharides of various chemical composition was probed for their potential in enhancing the metabolic post-thaw viability (PTV) of cryopreserved Vero cells. The best performing cryoprotective polysaccharides contained significant fucose amounts, resulting in average PTV 2.8-fold (up to 3.1-fold) compared to 0.8-fold and 2.2-fold for all non-cryoprotective and cryoprotective polysaccharides, respectively, outperforming the optimized commercial CryoStor™ CS5 formulation (2.6-fold). Stoichiometrically, a balance between fucose (18-35.7 mol%), uronic acids (UA) (13.5-26 mol%) and high molecular weight (MW > 1 MDa) generated optimal PTV. Principal component analysis (PCA) revealed that fucose enhances cell survival by a charge-independent, MW-scaling mechanism (PC1), drastically different from the charge-dominated ice growth disruption of UA (PC2). Its neutral nature and unique properties distinguishable from other neutral monomers suggest fucose may play a passive role in conformational adaptability of polysaccharide to ice growth inhibition, or an active role in cell membrane stabilization through binding. Ultimately, fucose-rich anionic polysaccharides may indulge in polymer-ice and polymer-cell interactions that actively disrupt ice and minimize lethal volumetric fluctuations due to a balanced hydrophobic-hydrophilic character. Our research showed the critical role neutral fucose plays in enhancing cellular cryopreservation outcomes, disputing previous assumptions of polyanionicity being the sole governing predictor of cryoprotection.

Assessment and comparison of viability assays for cellular products

BACKGROUND AIMS

Accurate assessment of cell viability is crucial in cellular product manufacturing, yet selecting the appropriate viability assay presents challenges due to various factors. This study compares and evaluates different viability assays on fresh and cryopreserved cellular products, including peripheral blood stem cell (PBSC) and peripheral blood mononuclear cell (PBMC) apheresis products, purified PBMCs and cultured chimeric antigen receptor and T-cell receptor-engineered T-cell products.

METHODS

Viability assays, including manual Trypan Blue exclusion, flow cytometry-based assays using 7-aminoactinomycin D (7-AAD) or propidium iodide (PI) direct staining or cell surface marker staining in conjunction with 7-AAD, Cellometer (Nexcelom Bioscience LLC, Lawrence, MA, USA) Acridine Orange/PI staining and Vi-CELL BLU Cell Viability Analyzer (Beckman Coulter, Inc, Brea, CA, USA), were evaluated. A viability standard was established using live and dead cell mixtures to assess the accuracy of these assays. Furthermore, precision assessment was conducted to determine the reproducibility of the viability assays. Additionally, the viability of individual cell populations from cryopreserved PBSC and PBMC apheresis products was examined.

RESULTS

All methods provided accurate viability measurements and generated consistent and reproducible viability data. The assessed viability assays were demonstrated to be reliable alternatives when evaluating the viability of fresh cellular products. However, cryopreserved products exhibited variability among the tested assays. Additionally, analyzing the viability of each subset of the cryopreserved PBSC and PBMC apheresis products revealed that T cells and granulocytes were more susceptible to the freeze-thaw process, showing decreased viability.

CONCLUSIONS

The study demonstrates the importance of careful assay selection, validation and standardization, particularly for assessing the viability of cryopreserved products. Given the complexity of cellular products, choosing a fit-for-purpose viability assay is essential.

Specifics of Cryopreservation of Hydrogel Biopolymer Scaffolds with Encapsulated Mesenchymal Stem Cells

The demand for regenerative medicine products is growing rapidly in clinical practice. Unfortunately, their use has certain limitations. One of these, which significantly constrains the widespread distribution and commercialization of such materials, is their short life span. For products containing suspensions of cells, this issue can be solved by using cryopreservation. However, this approach is rarely used for multicomponent tissue-engineered products due to the complexity of selecting appropriate cryopreservation protocols and the lack of established criteria for assessing the quality of such products once defrosted. Our research is aimed at developing a cryopreservation protocol for an original hydrogel scaffold with encapsulated MSCs and developing a set of criteria for assessing the quality of their functional activity in vitro. The scaffolds were frozen using two alternative types of cryocontainers and stored at either -40 °C or -80 °C. After cryopreservation, the external state of the scaffolds was evaluated in addition to recording the cell viability, visible changes during subsequent cultivation, and any alterations in proliferative and secretory activity. These observations were compared to those of scaffolds cultivated without cryopreservation. It was shown that cryopreservation at -80 °C in an appropriate type of cryocontainer was optimal for the hydrogels/adipose-derived stem cells (ASCs) tested if it provided a smooth temperature decrease during freezing over a period of at least three hours until the target values of the cryopreservation temperature regimen were reached. It was shown that evaluating a set of indicators, including the viability, the morphology, and the proliferative and secretory activity of the cells, enables the characterization of the quality of a tissue-engineered construct after its withdrawal from cryopreservation, as well as indicating the effectiveness of the cryopreservation protocol.

Screening of Hydrophilic Polymers Reveals Broad Activity in Protecting Phages during Cryopreservation

Bacteriophages have many biotechnological and therapeutic applications, but as with other biologics, cryopreservation is essential for storage and distribution. Macromolecular cryoprotectants are emerging for a range of biologics, but the chemical space for polymer-mediated phage cryopreservation has not been explored. Here we screen the cryoprotective effect of a panel of polymers against five distinct phages, showing that nearly all the tested polymers provide a benefit. Exceptions were poly(methacrylic acid) and poly(acrylic acid), which can inhibit phage-infection with bacteria, making post-thaw recovery challenging to assess. A particular benefit of a polymeric cryopreservation formulation is that the polymers do not function as carbon sources for the phage hosts (bacteria) and hence do not interfere with post-thaw measurements. This work shows that phages are amenable to protection with hydrophilic polymers and opens up new opportunities for advanced formulations for future phage therapies and to take advantage of the additional functionality brought by the polymers.

Challenges of Cell Counting in Cell Therapy Products

Cell counting is a common and fundamental cell measurement technique that plays a crucial role in the development and quality control of cell therapy products. However, accurate and reliable cell counting can be challenging owing to the complexity of cell preparations, diverse counting purposes, and various counting methods. This review summarizes the challenges encountered in cell counting for cell therapy products and provides strategies to improve the cell counting accuracy, thereby guiding the counting process and ensuring the quality of cell therapy products.

Osmotic properties of T cells determined by flow imaging microscopy in comparison to electrical sensing zone analysis

To develop cryopreservation methods for cell-based medicinal products it is important to understand osmotic responses of cells upon immersion into solutions with cryoprotective agents (CPAs) and during freezing. The aim of this study was to assess the osmotic response of T cells by using flow imaging microscopy (FIM) as a novel cell-sizing technique, and to corroborate the findings with electrical impedance measurements conducted on a Coulter counter. Jurkat cells were used as a potential model cell line for primary T cells. Cell volume responses were used to derive important cell parameters for cryopreservation such as the osmotically inactive cell volume Vb and the membrane permeability towards water and various CPAs. Unlike Coulter counter measurement, FIM, combined with Trypan blue staining can differentiate between viable and dead cells, which yields a more accurate estimation of Vb. Membrane permeabilities to water, dimethyl sulfoxide (Me2SO) and glycerol were measured for Jurkat cells at different temperatures. The permeation of Me2SO into the cells was faster in comparison to glycerol. CPA permeation decreased with decreasing temperature following Arrhenius behavior. Moreover, membrane permeability to water decreased in the presence of CPAs. Vb of Jurkat cells was found to be 49% of the isotonic volume and comparable to that of primary T cells. FIM proved to be a valuable tool to determine the membrane permeability parameters of mammalian cells to water and cryoprotective agents, which in turn can be used to rationally design CPA loading procedures for cryopreservation.

Post-thaw application of ROCK-inhibitors increases cryopreserved T-cell yield

Emerging cell-based therapies such as CAR-T (Chimeric Antigen Receptor T) cells require cryopreservation to store and deliver intact and viable cells. Conventional cryopreservation formulations use DMSO to mitigate cold-induced damage, but do not address all the biochemical damage mechanisms induced by cold stress, such as programmed cell death (apoptosis). Rho-associated protein kinases (ROCK) are a key component of apoptosis, and their activation contributes to apoptotic blebbing. Here we demonstrate that the ROCK inhibitor fasudil hydrochloride, when supplemented into the thawing medium of T-cells increases the overall yield of healthy cells. Cell yield was highest using 5 or 10% DMSO cryopreservation solutions, with lower DMSO concentrations (2.5%) leading to significant physical damage to the cells. After optimisation, the post-thaw yield of T-cells increased by approximately 20% using this inhibitor, a significant increase in the context of a therapy. Flow cytometry analysis did not show a significant reduction in the relative percentage of cell populations undergoing apoptosis, but there was a small reduction in the 8 hours following thawing. Fasudil also led to a reduction in reactive oxygen species. Addition of fasudil into the cryopreservation solution, followed by dilution (rather than washing) upon thaw also gave a 20% increase in cell yield, demonstrating how this could be deployed in a cell-therapy context, without needing to change clinical thawing routines. Overall, this shows that modulation of post-thaw biochemical pathways which lead to apoptosis (or other degradative pathways) can be effectively targeted as a strategy to increase T-cell yield and function post-thaw.

Evaluation of heat transfer in porous scaffolds under cryogenic treatment: a numerical study

The present work had evaluated the effect of cryogenic treatment (233 K) on the degradation of polymeric biomaterial using a numerical model. The study on effect of cryogenic temperature on mechanical properties of cell-seeded biomaterials is very limited. However, no study had reported material degradation evaluation. Different structures of silk-fibroin-poly-electrolyte complex (SFPEC) scaffolds had been designed by varying hole distance and hole diameter, with reference to existing literature. The size of scaffolds were maintained at 5 [Formula: see text] 5 mm2. Current study evaluates the effect of cryogenic temperature on mechanical properties (corelated to degradation) of scaffold. Six parameters related to scaffold degradation: heat transfer, deformation gradient, stress, strain, strain tensor, and displacement gradient were analyzed for three different cooling rates (- 5 K/min, - 2 K/min, and - 1 K/min). Scaffold degradation had been evaluated in the presence of water and four different concentrations of cryoprotectant solution. Heat distribution at various points (points_base, point_wall and point_core) on the region of interest (ROI) was found similar for different cooling rates of the system. Thermal stress was found developing proportional to cooling rate, which leads to minimal variation in thermal stress over time. Strain tensor was found gradually decreasing due to attenuating response of deformation gradient. In addition to that, dipping down of cryogenic temperature had prohibited the movement of molecules in the crystalline structure which had restricting the displacement gradient. It was found that uniform distribution of desired heat at different cooling rates has the ability to minimize the responses of other scaffold degradation parameters. It was found that the rates of change in stress, strain, and strain tensor were minimal at different concentrations of cryoprotectant. The present study had predicted the degradation behavior of PEC scaffold under cryogenic temperature on the basis of explicit mechanical properties.

Ovarian tissue cryopreservation and transplantation: a review on reactive oxygen species generation and antioxidant therapy

Cancer is the leading cause of death worldwide. Fortunately, the survival rate of cancer continues to rise, owing to advances in cancer treatments. However, these treatments are gonadotoxic and cause infertility. Ovarian tissue cryopreservation and transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with significant follicle loss and an accompanying short lifespan of the grafts. There has been a decade of research in cryopreservation-induced oxidative stress in single cells with significant successes in mitigating this major source of loss of viability. However, despite its success elsewhere and beyond a few promising experiments, little attention has been paid to this key aspect of OTCT-induced damage. As more and more clinical practices adopt OTCT for fertility preservation, it is a critical time to review oxidative stress as a cause of damage and to outline potential ameliorative interventions. Here we give an overview of the application of OTCT for female fertility preservation and existing challenges; clarify the potential contribution of oxidative stress in ovarian follicle loss; and highlight potential ability of antioxidant treatments to mitigate the OTCT-induced injuries that might be of interest to cryobiologists and reproductive clinicians.

Establishment of Primary Adult Skin Fibroblast Cell Lines from African Savanna Elephants (Loxodonta africana)

Following population declines of the African savanna elephant (Loxodonta africana) across the African continent, the establishment of primary cell lines of endangered wildlife species is paramount for the preservation of their genetic resources. In addition, it allows molecular and functional studies on the cancer suppression mechanisms of elephants, which have previously been linked to a redundancy of tumor suppressor gene TP53. This methodology describes the establishment of primary elephant dermal fibroblast (EDF) cell lines from skin punch biopsy samples (diameter: ±4 mm) of African savanna elephants (n = 4, 14-35 years). The applied tissue collection technique is minimally invasive and paves the way for future remote biopsy darting. On average, the first explant outgrowth was observed after 15.75 ± 6.30 days. The average doubling time (Td) was 93.02 ± 16.94 h and 52.39 ± 0.46 h at passage 1 and 4, respectively. Metaphase spreads confirmed the diploid number of 56 chromosomes. The successful establishment of EDF cell lines allows for future elephant cell characterization studies and for research on the cancer resistance mechanisms of elephants, which can be harnessed for human cancer prevention and treatment and contributes to the conservation of their genetic material.

Kinetic vitrification: concepts and perspectives in animal sperm cryopreservation

Sperm cryopreservation is an important tool for genetic diversity management programs and the conservation of endangered breeds and species. The most widely used method of sperm conservation is slow freezing, however, during the process, sperm cells suffer from cryoinjury, which reduces their viability and fertility rates. One of the alternatives to slow freezing is vitrification, that consist on rapid freezing, in which viable cells undergo glass-like solidification. This technology requires large concentrations of permeable cryoprotectants (P- CPA's) which increase the viscosity of the medium to prevent intracellular ice formation during cooling and warming, obtaining successful results in vitrification of oocytes and embryos. Unfortunately, this technology failed when applied to vitrification of sperm due to its higher sensitivity to increasing concentrations of P-CPAs. Alternatively, a technique termed 'kinetic sperm vitrification' has been used and consists in a technique of permeant cryoprotectant-free cryopreservation by direct plunging of a sperm suspension into liquid nitrogen. Some of the advantages of kinetic vitrification are the speed of execution and no rate-controlled equipment required. This technique has been used successfully and with better results for motility in human (50-70% motility recovery), dog (42%), fish (82%) and donkey (21.7%). However, more studies are required to improve sperm viability after devitrification, especially when it comes to motility recovery. The objective of this review is to present the principles of kinetic vitrification, the main findings in the literature, and the perspectives for the utilization of this technique as a cryopreservation method.

Advancing wide implementation of precision oncology: A liquid nitrogen-free snap freezer preserves molecular profiles of biological samples

PURPOSE

In precision oncology, tumor molecular profiles guide selection of therapy. Standardized snap freezing of tissue biospecimens is necessary to ensure reproducible, high-quality samples that preserve tumor biology for adequate molecular profiling. Quenching in liquid nitrogen (LN₂ ) is the golden standard method, but LN₂ has several limitations. We developed a LN₂ -independent snap freezer with adjustable cold sink temperature. To benchmark this device against the golden standard, we compared molecular profiles of biospecimens.

METHODS

Cancer cell lines and core needle normal tissue biopsies from five patients' liver resection specimens were used to compare mass spectrometry (MS)-based global phosphoproteomic and RNA sequencing profiles and RNA integrity obtained by both freezing methods.

RESULTS

Unsupervised cluster analysis of phosphoproteomic and transcriptomic profiles of snap freezer versus LN₂ -frozen K562 samples and liver biopsies showed no separation based on freezing method (with Pearson's r 0.96 (range 0.92-0.98) and >0.99 for K562 profiles, respectively), while samples with +2 h bench-time formed a separate cluster. RNA integrity was also similar for both snap freezing methods. Molecular profiles of liver biopsies were clearly identified per individual patient regardless of the applied freezing method. Two to 25 s freezing time variations did not induce profiling differences in HCT116 samples.

CONCLUSION

The novel snap freezer preserves high-quality biospecimen and allows identification of individual patients' molecular profiles, while overcoming important limitations of the use of LN₂ . This snap freezer may provide a useful tool in clinical cancer research and practice, enabling a wider implementation of (multi-)omics analyses for precision oncology.

Raman Spectroscopy Revealed Cell Passage-Dependent Distinct Biochemical Alterations in Radiation-Resistant Breast Cancer Cells

Recapitulating radioresistant cell features in pertinent cell line models is essential for deciphering fundamental cellular mechanisms. The limited understanding of passage and cell cycle phases on radioresistant cells revived post-cryopreservation led us to investigate the effect of sub-culturing in parental and radioresistant MCF-7 cells. In this study, the radioresistant cells showed high-intensity nucleic acid and cytochrome bands, which are potentially a radiation-induced spectral marker. Raman spectroscopy data showed dynamic biochemical alterations in revived radioresistant G₂/M synchronized cells at early cell passages 1 and 3 with stabilization at a latter cell passage, 5. The study highlights the importance of cell passaging and cell cycle phases in potentially changing the biochemical parameters during in vitro experiments after the revival of radioresistant cells post-cryopreservation.

Effects of tris (hydroxymethyl) aminomethane and egg yolk on the cryopreservation of buck semen

Objectives

This study was designed to examine the effects of various concentrations of tris (hydroxymethyl) aminomethane (tris) and egg yolk on the quality of cryopreserved buck sperm.

Materials and Methods

The collected semen samples were pooled, washed, and diluted into five different freezing extender groups, viz., extender I (tris 0% + egg yolk 0%), extender II (tris 1.41% + egg yolk 4%), extender III (tris 2.41% + egg yolk 8%), extender IV (tris 3.41% + egg yolk 16%), and extender V (tris 4.41% + egg yolk 24%). The sperm parameter of the five groups of extenders was evaluated after equilibration and cryopreservation.

Results

The results showed that extenders II-V provided significantly higher semen progressive motility and total motility percentages than extender I after equilibration (p < 0.05). The higher percentages of semen progressive motility, total motility, viability, and plasma membrane integrity (by both HOST under light microscopy and stain after HOST under light microscopy) were found in the sperm cryopreserved with extender IV than extender I, extender II, and extender III groups after thawing (p < 0.05). In addition, semen progressive motility, total motility, and viability were not further increased, or plasma membrane integrity (by both HOST tests) was decreased by the addition of tris and egg yolk (extender V) after cryopreservation (p < 0.05).

Conclusion

In conclusion, our result indicates that the following washing, the supplementation of tris (3.41% + egg yolk 16%) on the freezing extender are suitable for improving the semen quality of buck after freezing and thawing.

Cryopreservation of Yak Semen: A Comprehensive Review

An urgent need to boost the sustainability and efficiency of animal production exists, owing to the growing global population. Enhancing the global fertility of animals, especially cattle, is essential to ameliorate this issue. Artificial insemination and sperm cryopreservation have a considerable and favorable influence on the quantity and quality of the cattle produced. Sperm cryopreservation is crucial for livestock production because it promotes and accelerates genetic diversity and the worldwide dispersion of animals with enhanced genetics. Owing to the importance of cryobiology in reproductive technologies, researchers are developing new approaches, and they are testing cryoprotectant drugs to enhance sperm cryosurvival. However, the viability of sperm after freezing is low and widely varies across breeding yaks. These faults are crucial because they impede advances in reproductive biotechnology and the study of mammalian gametes at a fundamental level. Using chemicals, researchers have developed and enhanced various extenders with varying degrees of efficiency to reduce cryodamage and oxidative stress. In this article, we review the cryopreservation of yak semen, the development of extenders, the difficulties faced during cryopreservation, and the evaluation of semen quality using various methodologies. This review might be helpful for researchers exploring semen cryopreservation in the future, as demand for enhanced cryopreservation exists to boost the post-thaw viability and fertility of sperm.

In vitro versus cryo-induced capacitation of bovine spermatozoa, part 1: Structural, functional, and oxidative similarities and differences

Low temperatures during cryopreservation activate a cascade of changes, which may lead into irreversible damage and reduction of the fertilization potential, including the process of premature capacitation. The aim of our study was to evaluate the range of cell damage following the cryopreservation process and possible activation of cryocapacitation in bovine spermatozoa. For the experiments semen samples were obtained from 30 sexually mature Holstein bulls. Within the analysed parameters, we focused on the functional activity, structural integrity, capacitation status and oxidative profile. The samples were divided into three experimental groups, control (CTRL), in vitro capacitated (CAP) and cryopreserved (CRYO). Based on the collected data, there was a significant decrease in the sperm motility, mitochondrial membrane potential and concentration of cyclic adenosine monophosphate in the CRYO group when compared to CAP and CTRL (P<0.0001). A significant decrease (P<0.01; P<0.0001) in the membrane and acrosome integrity as well as DNA fragmentation index and a significant increase (P<0.0001) of necrotic cells were observed in the CRYO group. Following capacitation, a significant increase (P<0.01; P<0.0001) was recorded in the number of cells which underwent the acrosome reaction in the CRYO group against CAP and CTRL. Changes in the oxidative profile of the CRYO group indicates an increase (P<0.0001) in the reactive oxygen species generation, except for the superoxide radical, which was significantly higher (P<0.0001; P<0.001) in the CAP group in comparison with CRYO and CTRL. In summary, premature capacitation may be considered a consequence of cryopreservation and the assessed parameters could serve as physical markers of cryogenic damage to bovine spermatozoa in the future.

Cryopreservation of Roughscale Sole (Clidoderma asperrimum) Sperm: Effects of Cryoprotectant, Diluent, Dilution Ratio, and Thawing Temperature

Simple Summary

The roughscale sole, Clidoderma asperrimum, is found in the East and West Seas of Korea, waters north of Hokkaido in Japan, as well as the East China Sea, the East Pacific, and the Canadian Maritimes. In 2021, this fish was categorized as an endangered species. Thus, there is a need to maintain gametes by freezing sperm. This study investigated the impacts of the cryoprotective agent, diluent, dilution ratio, and thawing temperature on the cryopreservation of fish sperm. In this investigation, sperm dilution 1:1 with a mixture of 10% dimethyl sulfoxide + Stein’s solution and thawing at 10 °C provided the most effective DNA damage prevention. These results support the development of a roughscale sole sperm cryopreservation procedure.

Abstract

The roughscale sole, Clidoderma asperrimum is categorized as an endangered species. Sperm freezing is essential for preserving gametes. This study examined the CPA concentration, diluent, dilution ratio, and thawing temperature to design a sperm cryopreservation protocol for roughscale sole. The variables examined included sperm motility and kinematics, cell survival, fertilization, and DNA fragmentation. Sperm motility parameters were assessed via computer-assisted sperm analysis using a CEROS II instrument. Cell survival rate and DNA damage were assessed using the Cell Counting Kit-8 and single-cell gel electrophoresis assay, respectively. Sperm preservation was tested using several CPAs, including ethylene glycol, dimethyl sulfoxide (DMSO), glycerol, propylene glycol, and methanol. The diluents tested were 300 mM sucrose, 300 mM glucose, Stein’s solution, Ringer’s solution, and Hank’s solution. The optimal conditions for sperm cryopreservation were 10% DMSO + Stein’s solution. After thawing, sperm motility was highest with a 1:1 dilution ratio (sperm to CPA + diluent), at 69.20 ± 0.32%; thawing at 10 °C was optimal for post-thaw motility (72.03 ± 0.95%). The highest fertilization rate (40.00 ± 1.22%) was obtained using DMSO. The fresh sperm had the lowest tail DNA, followed by 10% DMSO + Stein’s solution. The developed cryopreservation methods can be used in roughscale sole hatcheries.

Comparison of freshly cultured versus cryopreserved mesenchymal stem cells in animal models of inflammation: A pre-clinical systematic review

Background:

Mesenchymal stem cells (MSCs) are multipotent cells that demonstrate therapeutic potential for the treatment of acute and chronic inflammatory-mediated conditions. Although controversial, some studies suggest that MSCs may lose their functionality with cryopreservation which could render them non-efficacious. Hence, we conducted a systematic review of comparative pre-clinical models of inflammation to determine if there are differences in in vivo measures of pre-clinical efficacy (primary outcomes) and in vitro potency (secondary outcomes) between freshly cultured and cryopreserved MSCs.

Methods:

A systematic search on OvidMEDLINE, EMBASE, BIOSIS, and Web of Science (until January 13, 2022) was conducted. The primary outcome included measures of in vivo pre-clinical efficacy; secondary outcomes included measures of in vitro MSC potency. Risk of bias was assessed by the SYRCLE ‘Risk of Bias’ assessment tool for pre-clinical studies.

Results:

Eighteen studies were included. A total of 257 in vivo pre-clinical efficacy experiments represented 101 distinct outcome measures. Of these outcomes, 2.3% (6/257) were significantly different at the 0.05 level or less; 2 favoured freshly cultured and 4 favoured cryopreserved MSCs. A total of 68 in vitro experiments represented 32 different potency measures; 13% (9/68) of the experiments were significantly different at the 0.05 level or less, with seven experiments favouring freshly cultured MSC and two favouring cryopreserved MSCs.

Conclusions:

The majority of preclinical primary in vivo efficacy and secondary in vitro potency outcomes were not significantly different (p<0.05) between freshly cultured and cryopreserved MSCs. Our systematic summary of the current evidence base may provide MSC basic and clinical research scientists additional rationale for considering a cryopreserved MSC product in their pre-clinical studies and clinical trials as well as help identify research gaps and guide future related research.

Funding:

Ontario Institute for Regenerative Medicine

A cryopreservation method for bioengineered 3D cell culture models

Technologies to cryogenically preserve (a.k.a. cryopreserve) living tissue, cell lines and primary cells have matured greatly for both clinicians and researchers since their first demonstration in the 1950s and are widely used in storage and transport applications. Currently, however, there remains an absence of viable cryopreservation and thawing methods for bioengineered, three-dimensional (3D) cell models, including patients' samples. As a first step towards addressing this gap, we demonstrate a viable protocol for spheroid cryopreservation and survival based on a 3D carboxymethyl cellulose scaffold and precise conditions for freezing and thawing. The protocol is tested using hepatocytes, for which the scaffold provides both the 3D structure for cells to self-arrange into spheroids and to support cells during freezing for optimal post-thaw viability. Cell viability after thawing is improved compared to conventional pellet models where cells settle under gravity to form a pseudo-tissue before freezing. The technique may advance cryobiology and other applications that demand high-integrity transport of pre-assembled 3D models (from cell lines and in future cells from patients) between facilities, for example between medical practice, research and testing facilities.

Gamma-oryzanol supplemented in extender enhances the quality of semen cryopreservation and alters proteomic profile in Thai swamp buffalo

Reactive oxygen species (ROS) exert an adverse effect on sperm quality during the freezing process. Gamma-oryzanol is an effective antioxidant and has the ability to inhibit lipoperoxidation in various cells. Therefore, this study aims to investigate the effect of gamma-oryzanol supplementation in extender on post-thawed motility and proteomic profiles of swamp buffalo spermatozoa. Each ejaculate of an individual bull was divided into four equal aliquots. Gamma-oryzanol was supplemented at 0 (control), 0.1, 0.25, and 0.5 mM in tris-citrate egg yolk extender. The parameters of sperm motility were evaluated using computer assisted semen analyzer (CASA). The results showed that the progressive motility was significantly higher in 0.5 mM of gamma-oryzanol supplementation group when compared with the control group (p < 0.05), but no significant differences were observed among the treatments. In addition, a proteomic approach was applied to analyze the differentially expressed proteins in post-thawed sperm with or without gamma-oryzanol supplementation in extender. We confirmed that 2-phospho-d-glycerate hydro-lyase (ENO1), glutathione s-transferase mu 1 (GSTM1), phospholipid hydroperoxide glutathione peroxidase (GPX4), outer dense fiber protein 2 (ODF2), tektin-4 (TEKT4), tubulin beta-4B chain (TUBB4B), and ATP synthase subunit beta (ATP5B) were up-regulated in 0.5 mM of gamma-oryzanol supplementation group, which might be associated with the improved post-thawed motility observed in this treatment group. These results demonstrate the beneficial effect of gamma-oryzanol on post-thawed survival of swamp buffalo spermatozoa and help advance the understanding about molecular metabolism of sperm in this species.

Exogenous Melatonin Ameliorates the Negative Effect of Osmotic Stress in Human and Bovine Ovarian Stromal Cells

Ovarian tissue cryopreservation transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with follicle loss and an accompanying short lifespan of the grafts. Cryopreservation-induced damage could be due to cryoprotective agent (CPA) toxicity and osmotic shock. Therefore, one way to avoid this damage is to maintain the cell volume within osmotic tolerance limits (OTLs). Here, we aimed to determine, for the first time, the OTLs of ovarian stromal cells (OSCs) and their relationship with reactive oxygen species (ROS) and mitochondrial respiratory chain activity (MRCA) of OSCs. We evaluated the effect of an optimal dose of melatonin on OTLs, viability, MRCA, ROS and total antioxidant capacity (TAC) of both human and bovine OSCs in plated and suspended cells. The OTLs of OSCs were between 200 and 375 mOsm/kg in bovine and between 150 and 500 mOsm/kg in human. Melatonin expands OTLs of OSCs. Furthermore, melatonin significantly reduced ROS and improved TAC, MRCA and viability. Due to the narrow osmotic window of OSCs, it is important to optimize the current protocols of OTCT to maintain enough alive stromal cells, which are necessary for follicle development and graft longevity. The addition of melatonin is a promising strategy for improved cryopreservation media.

Evaluation of the TMRW vapor phase cryostorage platform using reproductive specimens and in vitro extended human embryo culture

OBJECTIVE

To assess the impact of shipment and storage of sperm, oocytes, and blastocysts in vapor phase nitrogen compared with static storage in liquid phase nitrogen.

DESIGN

Prospective cohort-matched study.

SETTING

Multiple in vitro fertilization laboratories in an in vitro fertilization network.

PATIENT(S)

Fifty-eight human embryos, 32 human oocytes, 15 units of bovine semen.

INTERVENTION(S)

Vapor vs. liquid nitrogen.

MAIN OUTCOME MEASURE(S)

The postwarming survival of oocytes, sperm, and blastocysts, and the developmental potential of blastocysts during in vitro extended culture.

RESULT(S)

Custom-designed labware, for use with the TMRW platform, enables continuous temperature monitoring during shipment and/or storage in the vapor phase robotic storage system. The highest temperature recorded for specimens shipped to a domestic laboratory was -180.2 °C with a mean ± SD of -190.4 ± 0.5 °C during shipment and -181.1 ± 0.6 °C during storage. Likewise, specimens shipped internationally had a high of -180.2 °C with a mean ± SD of -193.5 ± 0.6 °C during shipment and -181.2 ± 0.7 °C during storage. Results from the extended culture assays have revealed no deleterious effect of shipment and storage in nitrogen vapor. The viability of mammalian gametes and embryos was equivalent between the vapor phase and liquid phase storage.

CONCLUSION(S)

The evaluated system did not have any deleterious effects on the postwarming survival of sperm, oocytes, and blastocysts. The postwarming developmental potential of human blastocysts during in vitro extended culture was unaffected by storage and handling in the vapor phase nitrogen TMRW platform when compared with static liquid phase nitrogen storage. Our results suggest that the vapor phase cryostorage platform is a safe system to handle and store reproductive specimens for human assisted reproductive technology.

Impact of Cryopreservation and Freeze-Thawing on Therapeutic Properties of Mesenchymal Stromal/Stem Cells and Other Common Cellular Therapeutics

Purpose of Review

Cryopreservation and its associated freezing and thawing procedures–short “freeze-thawing”–are among the final steps in economically viable manufacturing and clinical application of diverse cellular therapeutics. Translation from preclinical proof-of-concept studies to larger clinical trials has indicated that these processes may potentially present an Achilles heel to optimal cell product safety and particularly efficacy in clinical trials and routine use.

Recent Findings

We review the current state of the literature on how cryopreservation of cellular therapies has evolved and how the application of this technique to different cell types is interlinked with their ability to engraft and function upon transfer in vivo, in particular for hematopoietic stem and progenitor cells (HSPCs), their progeny, and therapeutic cell products derived thereof. We also discuss pros and cons how this may differ for non-hematopoietic mesenchymal stromal/stem cell (MSC) therapeutics. We present different avenues that may be crucial for cell therapy optimization, both, for hematopoietic (e.g., effector, regulatory, and chimeric antigen receptor (CAR)-modified T and NK cell based products) and for non-hematopoietic products, such as MSCs and induced pluripotent stem cells (iPSCs), to achieve optimal viability, recovery, effective cell dose, and functionality of the cryorecovered cells.

Summary

Targeted research into optimizing the cryopreservation and freeze-thawing routines and the adjunct manufacturing process design may provide crucial advantages to increase both the safety and efficacy of cellular therapeutics in clinical use and to enable effective market deployment strategies to become economically viable and sustainable medicines.

Biomolecular and Biological Applications of Solid-State NMR with Dynamic Nuclear Polarization Enhancement

Solid-state NMR spectroscopy (ssNMR) with magic-angle spinning (MAS) enables the investigation of biological systems within their native context, such as lipid membranes, viral capsid assemblies, and cells. However, such ambitious investigations often suffer from low sensitivity due to the presence of significant amounts of other molecular species, which reduces the effective concentration of the biomolecule or interaction of interest. Certain investigations requiring the detection of very low concentration species remain unfeasible even with increasing experimental time for signal averaging. By applying dynamic nuclear polarization (DNP) to overcome the sensitivity challenge, the experimental time required can be reduced by orders of magnitude, broadening the feasible scope of applications for biological solid-state NMR. In this review, we outline strategies commonly adopted for biological applications of DNP, indicate ongoing challenges, and present a comprehensive overview of biological investigations where MAS-DNP has led to unique insights.

Freeform Cell-Laden Cryobioprinting for Shelf-Ready Tissue Fabrication and Storage

One significant drawback of existing bioprinted tissues is their lack of shelf-availability caused by complications in both fabrication and storage. Here, we report a cryobioprinting strategy for simultaneously fabricating and storing cell-laden volumetric tissue constructs through seamlessly combining extrusion bioprinting and cryopreservation. The cryobioprinting performance was investigated by designing, fabricating, and storing cell-laden constructs made of our optimized cryoprotective gelatin-based bioinks using a freezing plate with precisely controllable temperature. The in situ freezing process further promoted the printability of cell-laden hydrogel bioinks to achieve freeform structures otherwise inconvenient with direct extrusion bioprinting. The effects of bioink composition on printability and cell viability were evaluated. The functionality of the method was finally investigated using cell differentiation and chick ex ovo assays. The results confirmed the feasibility and efficacy of cryobioprinting as a single-step method for concurrent tissue biofabrication and storage.

Cryopreservation and post-thaw characterization of dissociated human islet cells

The objective of this study is to optimize the cryopreservation of dissociated islet cells and obtain functional cells that can be used in single-cell transcriptome studies on the pathology and treatment of diabetes. Using an iterative graded freezing approach we obtained viable cells after cooling in 10% dimethyl sulfoxide and 6% hydroxyethyl starch at 1°C/min to -40°C, storage in liquid nitrogen, rapid thaw, and removal of cryoprotectants by serial dilution. The expression of epithelial cell adhesion molecule declined immediately after thaw, but recovered after overnight incubation, while that of an endocrine cell marker (HPi2) remained high after cryopreservation. Patch-clamp electrophysiology revealed differences in channel activities and exocytosis of various islet cell types; however, exocytotic responses, and the biophysical properties of voltage-gated Na+ and Ca2+ channels, are sustained after cryopreservation. Single-cell RNA sequencing indicates that overall transcriptome and crucial exocytosis genes are comparable between fresh and cryopreserved dispersed human islet cells. Thus, we report an optimized procedure for cryopreserving dispersed islet cells that maintained their membrane integrity, along with their molecular and functional phenotypes. Our findings will not only provide a ready source of cells for investigating cellular mechanisms in diabetes but also for bio-engineering pseudo-islets and islet sheets for modeling studies and potential transplant applications.

Effect of glycerol addition time on the cryopreserved Korean native brindle cattle (Chikso) sperm quality

Although cryopreservation is an efficient method for maintaining the biological and genetic resources of sperm, the sperm damage during the cryopreservation process cannot be ignored. It should be possible to obtain the most effective cryopreservation performance by accurately grasping the effects of various factors on the cryopreservation of sperm. The previous study demonstrated that a suitable standard protocol for cryopreservation of Korean native brindled cattle (Chikso) does not exist, based on the methods for semen cryopreservation of Chikso differ in each research center. The most obvious difference between most of protocols is the addition of glycerol before and after cooling during the Chikso cryopreserved semen process. Therefore we focused on the effects of glycerol addition time on the quality of cryopreserved Chikso sperm. In the present study, 27 individual Chikso samples were collected by transrectal massage and divided into two parts: the “cryopreservation method A” group (adding glycerol before cooling) and the “cryopreservation method B” group (adding glycerol after cooling). Meanwhile, the values of various sperm parameters were derived from each group, including sperm motility, kinematics, capacitation status, cell viability, and intracellular ATP levels, which we used to compare and evaluate sperm function. The results of this study indicated that during the semen cryopreservation process of the Chikso, the addition of glycerol after cooling yielded superior results in a variety of sperm parameters, such as sperm motility, progressive motility, rapid motility, VCL, VSL, VAP, ALH, capacitation status, viability, and intracellular ATP level after freezing and thawing. Our study is suggested that the glycerol addition time during the cryopreservation process for Chikso should be considered. In addition, our results may be provided reference to develop suitable the cryopreservation procedure of the Chikso sperm.

The Use of κ-Carrageenan in Egg Yolk Free Extender Improves the Efficiency of Canine Semen Cryopreservation

κ-Carrageenan is a plant polysaccharide derived from red seaweeds reported to possess potential medicinal and antioxidants activities. The present study aimed to identify the cryoprotective effects of κ-carrageenan on the quality of frozen-thawed canine semen. Twenty-eight ejaculates were collected and diluted in a Tris egg-yolk-free extender supplemented with various concentrations of κ-carrageenan (0.0%, 0.1%, 0.2%, 0.3%, and 0.5%). The addition of κ-carrageenan to the extender at a 0.2% concentration induced a significant increase in the total motility (TM) and the rapid progressive motility (RPM) of canine sperm. Among the experimental groups, the highest percentage of sperms with intact acrosomes was found in the 0.5% κ-carrageenan group (p < 0.05). Apoptosis levels were significantly lower in the 0.1% and 0.2% κ-carrageenan treatment. Moreover, sperm in the κ-carrageenan supplemented group showed a significantly higher expression of antiapoptotic (Bcl-2) and lower expression of NADPH oxidase (NOX5), spermine synthase (SMS), and spermine oxidase (SMOX) genes than those in the control group. In conclusion, the addition of κ-carrageenan to the freezing extender improved the overall efficiency of frozen-thawed dog spermatozoa.

Polymer-Mediated Cryopreservation of Bacteriophages

Bacteriophages (phages, bacteria-specific viruses) have biotechnological and therapeutic potential. To apply phages as pure or heterogeneous mixtures, it is essential to have a robust mechanism for transport and storage, with different phages having very different stability profiles across storage conditions. For many biologics, cryopreservation is employed for long-term storage and cryoprotectants are essential to mitigate cold-induced damage. Here, we report that poly(ethylene glycol) can be used to protect phages from cold damage, functioning at just 10 mg·mL-1 (∼1 wt %) and outperforms glycerol in many cases, which is a currently used cryoprotectant. Protection is afforded at both -20 and -80 °C, the two most common temperatures for frozen storage in laboratory settings. Crucially, the concentration of the polymer required leads to frozen solutions at -20 °C, unlike 50% glycerol (which results in liquid solutions). Post-thaw recoveries close to 100% plaque-forming units were achieved even after 2 weeks of storage with this method and kill assays against their bacterial host confirmed the lytic function of the phages. Initial experiments with other hydrophilic polymers also showed cryoprotection, but at this stage, the exact mechanism of this protection cannot be concluded but does show that water-soluble polymers offer an alternative tool for phage storage. Ice recrystallization inhibiting polymers (poly(vinyl alcohol)) were found to provide no additional protection, in contrast to their ability to protect proteins and microorganisms which are damaged by recrystallization. PEG's low cost, solubility, well-established low toxicity/immunogenicity, and that it is fit for human consumption at the concentrations used make it ideal to help translate new approaches for phage therapy.

Biomolecular Perturbations in In-Cell Dynamic Nuclear Polarization Experiments

In-cell DNP is a growing application of NMR to the study of biomolecular structure and function within intact cells. An important unresolved question for in-cell DNP spectroscopy is the integrity of cellular samples under the cryogenic conditions of DNP. Despite the rich literature around cryopreservation of cells in the fields of stem cell/embryonic cell therapeutics, cell line preservation and in cryo-EM applications, the effect of cryopreservation procedures on DNP parameters is unclear. In this report we investigate cell survival and apoptosis in the presence of cryopreserving agents and DNP radicals. We also assess the effects of these reagents on cellular enhancements. We show that the DNP radical AMUPol has no effect on membrane permeability and does not induce apoptosis. Furthermore, the standard aqueous glass forming reagent, comprised of 60/30/10 d₈-glycerol/D₂O/H₂O (DNP juice), rapidly dehydrates cells and induces apoptosis prior to freezing, reducing structural integrity of the sample prior to DNP analysis. Preservation with d₆-DMSO at 10% v/v provided similar DNP enhancements per √unit time compared to glycerol preservation with superior maintenance of cell size and membrane integrity prior to freezing. DMSO preservation also greatly enhanced post-thaw survival of cells slow-frozen at 1°C/min. We therefore demonstrate that in-cell DNP-NMR studies should be done with d₆-DMSO as cryoprotectant and raise important considerations for the progression of in-cell DNP-NMR towards the goal of high quality structural studies.

The Impact of Ammonium Chloride-Based Erythrocyte Lysis Process on Banked Adipose-Derived Stem Cells

The safety of banked human adipose-derived stem cells (hADSCs) purified by 155 mM ammonium chloride (NH₄Cl)-based erythrocyte lysis has not been evaluated. This study was conducted to determine the impact of NH₄Cl-based erythrocyte lysis on the biological characteristics of cryopreserved hADSCs. Stromal vascular fractions (SVFs) were obtained from lipoaspirates and purified with NH₄Cl-based erythrocyte lysis (lysis group) or without (nonlysis group). The hADSCs were freshly isolated (fresh group) from SVFs and/or cryopreserved for 2 weeks (cryo group). The morphologies, immunophenotypes, viability, apoptosis, and growth kinetics of each group were compared. The cell cycle and differentiation capacity assays were performed in both cryopreserved groups. All groups showed similar cell morphology, immunological phenotypes, and viability. However, the main effect of lysis and its interaction with cryopreservation were observed when early apoptosis was regarded as a dependent variable in two-way repeated-measures analysis of variance. After cryopreservation, significant growth retardation and S-phase fraction reduction were observed in lytic hADSCs compared with those in nonlytic hADSCs. No significant differences in the adipogenic and osteogenic differentiation capacities were found between the two groups. Although NH₄Cl-based erythrocyte lysis did not affect the cell morphology, immunological phenotypes, viability, and adipogenic and osteogenic differentiation capacities of cryopreserved hADSCs, exposure to NH₄Cl-based erythrocyte lysis or its synergistic action with cryopreservation may induce apoptosis and inhibit the proliferation and mitosis of cryopreserved hADSCs. These results indicate that NH₄Cl-based erythrocyte lysis is not suitable for high-quality banked collection of hADSCs for future clinical applications. Further development of safe, convenient, and cost-effective purification methods of hADSCs is warranted.

Optimization of a Protocol for the Cryopreservation of Sperm in Pellets for the Common Pheasant (Phasianus colchicus mongolicus)

The sperm of each avian species and breed have unique characteristics that render them more or less susceptible to the freezing-thawing process; therefore, a suitable cryopreservation protocol that is specific for the sperm of each type of bird is needed. In this context, little information about the common pheasant's sperm is available. Therefore, the aim of this study was to test different parameters at each step of the process of freezing into pellets and thawing to detect the least deleterious parameter settings. Sixteen different protocols were tested by studying two levels in each of the four steps (dilution, equilibration at 5 °C, final dimethylacetamide concentration, and dimethylacetamide equilibration time) comprising the freezing process. The pheasant sperm exhibited a high susceptibility to the damage caused by freezing into pellets; however, the survival of the sperm reached 29%, and the greatest recovered mobility was 22%. The mobility of the sperm was affected by the dilution and the dimethylacetamide concentration, and the viability of the sperm was affected by the equilibration at 5 °C and the dimethylacetamide equilibration. The protocols that caused the least damage to the pheasant sperm were found to be those with higher dilution rates, 10 min of equilibration at 5 °C, and 6% dimethylacetamide equilibrated for 1 or 5 min. In the present study, we individualise some applicable parameters for certain critical steps of the freezing-thawing process; however, further investigations are needed in order to improve upon and complete a suitable protocol for the cryopreservation and thawing of pheasant sperm.

Lipid profiling in chilled coral larvae

Coral reefs are disappearing worldwide as a result of several harmful human activities. The establishment of cryobanks can secure a future for these ecosystems. To design effective cryopreservation protocols, basic proprieties such as chilling tolerance and lipid content must be assessed. In the present study, we investigated chilling sensitivity and the effect of chilling exposure on the lipid content and composition of larvae belonging to 2 common Indo-Pacific corals: Seriatopora caliendrum and Pocillopora verrucosa. The viability of coral larvae incubated with 0.5, 1, and 2 M ethylene glycol (EG), propylene glycol (PG), dimethyl sulfoxide (Me₂SO), methanol, or glycerol and kept at 5 °C for different time periods was documented. In addition, we investigated the content of cholesterol, triacylglycerol (TAG), wax ester (WE), sterol ester (SE), lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamine, and several fatty acid (FA) classes in coral propagules incubated with 1 M PG or EG and kept at 5 °C for 6 h. Moreover, we examined seasonal changes in the aforementioned lipid classes in coral larvae. S. caliendrum incubated with 0.5 M PG or Me₂SO and chilled for 2 h exhibited a viability rate of 11 ± 11%, whereas P. verrucosa exhibited a viability rate of 22 ± 14% after being chilled for 4 h. Furthermore, the results indicated that chilling exposure did not affect the content of any investigated lipid class in either species. The higher concentration of SE in P. verrucosa compared to S. caliendrum larvae may have contributed to the different cryotolerance displayed by the 2 larval species. A year-round lipid analysis of both coral larvae species revealed trends of homeoviscous adaptation and seasonal enhancement of lipid fluxes from symbionts to the host. During winter, the cholesterol/phospholipid ratio significantly increased, and P. verrucosa larvae exhibited an averagely decrease in FA chain lengths. During spring and summer, intracellular lipid content in the form of TAGs and WEs significantly increased in both species, and the average content of Symbiodiniaceae-derived FAs increased in P. verrucosa larvae. We concluded that the low cryotolerance displayed by S. caliendrum and P. verrucosa larvae is attributable to their chilling-sensitive membrane lipid profile and the high intracellular lipid content provided by their endosymbionts.

Mitochondria Content and Activity Are Crucial Parameters for Bull Sperm Quality Evaluation

Standard sperm evaluation parameters do not enable predicting their ability to survive cryopreservation. Mitochondria are highly prone to suffer injuries during freezing, and any abnormalities in their morphology or function are reflected by a decline of sperm quality. Our work focused on describing a link between the number and the activity of mitochondria, with an aim to validate its applicability as a biomarker of bovine sperm quality. Cryopreserved sperm collected from bulls with high (group 1) and low (group 2) semen quality was separated by swim up. The spermatozoa of group 1 overall retained more mitochondria (MitoTrackerGreen) and mtDNA copies, irrespective of the fraction. Regardless of the initial ejaculate quality, the motile sperm contained significantly more mitochondria and mtDNA copies. The same trend was observed for mitochondrial membrane potential (ΔΨm, JC-1), where motile sperm displayed high ΔΨm. These results stay in agreement with transcript-level evaluation (real-time polymerase chain reaction, PCR) of antioxidant enzymes (PRDX1, SOD1, GSS), which protect cells from the reactive oxygen species. An overall higher level of glutathione synthetase (GSS) mRNA was noted in group 1 bulls, suggesting higher ability to counteract free radicals. No differences were noted between basal oxygen consumption rate (OCR) (Seahorse XF Agilent) and ATP-linked respiration for group 1 and 2 bulls. In conclusion, mitochondrial content and activity may be used as reliable markers for bovine sperm quality evaluation.

The role of apoptosis in cryopreserved animal oocytes and embryos

Cryopreservation of both gametes and embryos, both for storage and for the preservation of their developmental capacity is a critical aspect of assisted reproductive technology. The survival of reproductive material following cryopreservation protocols is not only vital to clinical applications in the human in vitro fertilisation clinic, but is also important in the in vitro production of livestock embryos. The ability to routinely cryopreserve oocytes and embryos of livestock species has the potential to improve animal welfare, reduce environmental impact, and reduce the associated costs for breeding companies through the reduction of live animal transportation. Unfortunately, frozen oocytes and embryos are regularly documented to contain a higher proportion of apoptotic cells compared to their non-frozen counterparts, with freezing procedures thought to trigger apoptotic pathways of cell death. Comparisons between frozen and non-frozen samples also show changes in the gene expression of apoptotic factors such as Bcl-2 and Bax in response to cryopreservation. Apoptotic inhibition has the potential to improve cryosurvival, and how to achieve this is subject to debate. Here, we review how exposure to low temperatures during cryopreservation may be responsible for the abnormal activation of apoptotic pathways in mammalian oocytes and embryos, and discuss the ways in which they can be influenced to improve cryopreservation protocols, particularly in agriculturally important species.

Effective Cryopreservation of a Bioluminescent Auxotrophic Escherichia coli-Based Amino Acid Array to Enable Long-Term Ready-to-Use Applications

Amino acid arrays comprising bioluminescent amino acid auxotrophic Escherichia coli are effective systems to quantitatively determine multiple amino acids. However, there is a need to develop a method for convenient long-term preservation of the array to enable its practical applications. Here, we reported a potential strategy to efficiently maintain cell viability within the portable array. The method involves immobilization of cells within agarose gel supplemented with an appropriate cryoprotectant in individual wells of a 96-well plate, followed by storage under freezing conditions. Six cryoprotectants, namely dimethyl sulfoxide, glycerol, ethylene glycol, polyethylene glycol, sucrose, and trehalose, were tested in the methionine (Met) auxotroph-based array. Carbohydrate-type cryoprotectants (glycerol, sucrose, and trehalose) efficiently preserved the linearity of determination of Met concentration. In particular, the array with 5% trehalose exhibited the best performance. The Met array with 5% trehalose could determine Met concentration with high linearity (R² value = approximately 0.99) even after storage at −20 °C for up to 3 months. The clinical utilities of the Met and Leu array, preserved at −20 °C for 3 months, were also verified by successfully quantifying Met and Leu in spiked blood serum samples for the diagnosis of the corresponding metabolic diseases. This long-term preservation protocol enables the development of a ready-to-use bioluminescent E. coli-based amino acid array to quantify multiple amino acids and can replace the currently used laborious analytical methods.

Corneal Donation: Current Guidelines and Future Direction

PURPOSE

This review aims to outline current practices and guidelines of corneal donation and eye banking, describes the implications of COVID-19 and emerging diseases on the corneal donor pool, and discusses future trends to improve and increase the efficiency of the processes involved in corneal donation and eye banking.

SUMMARY

Corneal screening, preservation, corneal storage, and prevention of systemic disease transmission from donor to recipient have been crucial in shaping the policies of the FDA and eye banks across the world. Eye banks globally have developed varying guidelines and criteria for evaluating the viability of donor corneas. Variables such as the age of the donor, medical history, and potential disease transmission are important screening parameters. While known infectious diseases may be transmissible through the cornea, emerging infectious diseases that are not well studied may be more transmissible than other infections. In particular, coronavirus has impacted corneal transplantation as SARS-CoV-2 expression has been detected in corneal tissue and conjunctiva. In recent years, partial-thickness corneal transplantations have been introduced. Lamellar grafts and other corneal layers are now utilized for transplantation of the specific areas that are damaged.

Development of a Cryoprotective Formula Based on the Fucose-Containing Polysaccharide FucoPol

This study reports the performance of the polysaccharide FucoPol as an enhancer of cryoprotective formulations. FucoPol at a concentration of 0.25% (w/v) was added to several normothermic Dulbecco-derived solutions and hypothermic Euro-Collins, Custodiol-HTK, and Unisol-CV media, substituting some constituents in the latter class to develop FucoPol-based formulations that were tested for their ability to cryopreserve Vero cells. Supplementation yielded post-thaw cell recovery enhancements of at least 70% and averaged at 82%. The FucoPol-supplemented formulations Dulbecco(+)^+FP and Unisol-CV_S3 achieved cell viabilities capable of competing with the commercial cryogenic formula CryoStor CS5. Particularly in Unisol-CV_S3, mannitol, glucose, gluconate, and dextran were all substituted by 0.25% FucoPol, and still, a similar viability was achieved. Multiparametric correlation clustering showed that FucoPol cryoprotection synergizes best with K⁺, Ca²⁺, and Cl^- in its microenvironment. Component substitution analysis demonstrated that FucoPol acts consistently as a cryoprotectant, an impermeant, and a colloidal stabilizer, providing a combined alternative to glucose, mannitol, gluconate, and dextran, thus highlighting its potential in the development of high-performing cryoprotective formulas.

Natural deep eutectic systems, an emerging class of cryoprotectant agents

This work aimed at evaluating the potential of using natural deep eutectic systems (NADES) as cryoprotectant agents (CPAs). Several combinations between natural primary metabolites that have been identified in animals that live in extreme cold climates were prepared. All systems showed very little cytoxicity towards L929 cells at concentrations high as 1–2 M. Moreover, this cell line was highly tolerant to 10% (w/v) of NADES when compared to Me₂SO. To test NADES as CPAs, two cell lines were used, L929 and HacaT cells. After freeze/thawing cycle, it was possible to observe that for L929 cells, NADES presented similar behaviour to Me₂SO. For Hacat cell line a significant improvement on post-thawing recovery was observed. Moreover, the results presented herein showed that NADES do not need to be removed from the freezing media after thawing the cells, which is a great advantage of these materials. Additionally, we have shown that NADES can act as CPA when cells are frozen at −20 °C. In overall, the results demonstrate the high potential of NADES to be used in cryobiology as alternative CPAs.