Cryopreservation in trehalose preserves functional capacity of murine spermatogonial stem cells

New strategies for germ cell cryopreservation: Cryoinjury modulation

Cryopreservation is an option for the preservation of pre- or post-pubertal female or male fertility. This technique not only is beneficial for human clinical applications, but also plays a crucial role in the breeding of livestock and endangered species. Unfortunately, frozen germ cells, including oocytes, sperm, embryos, and spermatogonial stem cells, are subject to cryoinjury. As a result, various cryoprotective agents and freezing techniques have been developed to mitigate this damage. Despite extensive research aimed at reducing apoptotic cell death during freezing, a low survival rate and impaired cell function are still observed after freeze-thawing. In recent decades, several cell death pathways other than apoptosis have been identified. However, the relationship between these pathways and cryoinjury is not yet fully understood, although necroptosis and autophagy appear to be linked to cryoinjury. Therefore, gaining a deeper understanding of the molecular mechanisms of cryoinjury could aid in the development of new strategies to enhance the effectiveness of the freezing of reproductive tissues. In this review, we focus on the pathways through which cryoinjury leads to cell death and propose novel approaches to enhance freezing efficacy based on signaling molecules.

Trehalose in Biomedical Cryopreservation-Properties, Mechanisms, Delivery Methods, Applications, Benefits, and Problems

Cells and tissues are the foundation of translational medicine. At present, one of the main technological obstacles is their preservation for long-term usage while maintaining adequate viability and function. Optimized storage techniques must be developed to make them safer to use in the clinic. Cryopreservation is the most common long-term preservation method to maintain the vitality and function of cells and tissues. But, the formation of ice crystals in cells and tissues is considered to be the main mechanism that could harm cells and tissues during freezing and thawing. To reduce the formation of ice crystals, cryoprotective agents (CPAs) must be added to the cells and tissues to achieve the cryoprotective effect. However, conventional cryopreservation of cells and tissues often needs to use toxic organic solvents as CPAs. As a result, cryopreserved cells and tissues may need to go through a time-consuming washing process to remove CPAs for further applications in translational medicine, and multiple valuable cells are potentially lost or killed. Currently, trehalose has been researched as a nontoxic CPA due to its cryoprotective ability and stability during cryopreservation. Nevertheless, trehalose is a nonpermeable CPA, and the lack of an effective intracellular trehalose delivery method has become the main obstacle to its use in cryopreservation. This article illustrated the properties, mechanisms, delivery methods, and applications of trehalose, summarized the benefits and limits of trehalose, and summed up the findings and research direction of trehalose in biomedical cryopreservation.

The Role of Promyelocytic Leukemia Zinc Finger (PLZF) and Glial-Derived Neurotrophic Factor Family Receptor Alpha 1 (GFRα1) in the Cryopreservation of Spermatogonia Stem Cells

The cryopreservation of spermatogonia stem cells (SSCs) has been widely used as an alternative treatment for infertility. However, cryopreservation itself induces cryoinjury due to oxidative and osmotic stress, leading to reduction in the survival rate and functionality of SSCs. Glial-derived neurotrophic factor family receptor alpha 1 (GFRα1) and promyelocytic leukemia zinc finger (PLZF) are expressed during the self-renewal and differentiation of SSCs, making them key tools for identifying the functionality of SSCs. To the best of our knowledge, the involvement of GFRα1 and PLZF in determining the functionality of SSCs after cryopreservation with therapeutic intervention is limited. Therefore, the purpose of this review is to determine the role of GFRα1 and PLZF as biomarkers for evaluating the functionality of SSCs in cryopreservation with therapeutic intervention. Therapeutic intervention, such as the use of antioxidants, and enhancement in cryopreservation protocols, such as cell encapsulation, cryoprotectant agents (CPA), and equilibrium of time and temperature increase the expression of GFRα1 and PLZF, resulting in maintaining the functionality of SSCs. In conclusion, GFRα1 and PLZF have the potential as biomarkers in cryopreservation with therapeutic intervention of SSCs to ensure the functionality of the stem cells.

Development of Serum-Free Media for Cryopreservation of Hydrogel Encapsulated Cell-Based Therapeutics

Introduction

While hydrogel encapsulation of cells has been developed to treat multiple diseases, methods to cryopreserve and maintain the composite function of therapeutic encapsulated cell products are still needed to facilitate their storage and distribution. While methods to preserve encapsulated cells, and post-synthesis have received recent attention, effective preservation mediums have not been fully defined.

Methods

We employed a two-tiered screen of an initial library of 32 different cryopreservation agent (CPA) formulations composed of different cell-permeable and impermeable agents. Formulations were assayed using dark field microscopy to evaluate alginate hydrogel matrix integrity, followed by cell viability analyses and measurements of functional secretion activity.

Results

The structural integrity of large > 1 mm alginate capsules were highly sensitive to freezing and thawing in media alone but could be recovered by a number of CPA formulations containing different cell-permeable and impermeable agents. Subsequent viability screens identified two top-performing CPA formulations that maximized capsule integrity and cell viability after storage at - 80 °C. The top formulation (10% Dimethyl sulfoxide (DMSO) and 0.3 M glucose) was demonstrated to preserve hydrogel integrity and retain cell viability beyond a critical USA FDA set 70% viability threshold while maintaining protein secretion and resultant cell potency.

Conclusions

This prioritized screen identified a cryopreservation solution that maintains the integrity of large alginate capsules and yields high viabilities and potency. Importantly, this formulation is serum-free, non-toxic, and can support the development of clinically translatable encapsulated cell-based therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-022-00739-7.

Recent Developments in Cell Shipping Methods

As opposed to remarkable advances in the cell therapy industry, researches reveal inexplicable difficulties associated with preserving and post-thawing cell death. Post cryopreservation apoptosis is a common occurrence that has attracted the attention of scientists to use apoptosis inhibitors. Transporting cells without compromising their survival and function is crucial for any experimental cell-based therapy. Preservation of cells allows the safe transportation of cells between distances and improves quality control testing in clinical and research applications. The vitality of transported cells is used to evaluate the efficacy of transportation strategies. For many decades, the conventional global methods of cell transfer were not only expensive but also challenging and had adverse effects. The first determination of some projects is optimizing cell survival after cryopreservation. The new generation of cryopreservation science wishes to find appropriate and alternative methods for cell transportation to ship viable cells at an ambient temperature without dry ice or in media-filled flasks. The diversity of cell therapies demands new cell shipping methodologies and cryoprotectants. In this review, we tried to summarize novel improved cryopreservation methods and alternatives to cryopreservation with safe and viable cell shipping at ambient temperature, including dry preservation, hypothermic preservation, gel-based methods, encapsulation methods, fibrin microbeads, and osmolyte solution compositions. This article is protected by copyright. All rights reserved.

Co-supplementation of freezing media with trehalose and vitamin C on cell viability and apoptotic gene expression in ovine spermatogonial stem cells

The purpose of this research was to investigate the trehalose and vitamin C (Vit C) co-supplementation of freezing media to create a successful cryopreservation protocol for conservation of ovine spermatogonial stem cells (SSCs). SSCs were cryopreserved and cultured with an essential freezing medium containing 200 mM trehalose, 40 µg/mL Vit C, and a combination of both for 3 weeks. Cell viability, colony number and diameter and mRNA levels of Bax, and Bcl-2 genes were evaluated before and after cryopreservation with quantitative real-time PCR. The results showed that cells cryopreserved in freezing medium containing 200 mM of trehalose plus 40 µg/mL Vit C had considerably greater cell viability than the control group (P<0.0001). Up to the 3rd week of cell culture, supplementation of freezing medium with 200 mM trehalose resulted in significantly lower colonies diameters than in the control group. No significant differences were observed during the 1st to 2nd weeks in colony diameter and number of colonies between cells cryopreserved in the freezing medium containing either Vit C or trehalose compared with the control groups. Following thawing, the mRNA level of Bax in the Vit C + trehalose group was drastically lower than in those treated with trehalose or Vit C only (P<0.0001). High expression of Bcl-2 in the 40 µg/mL Vit C group was recorded in the thawed cells compared to the control group (P<0.0001). These findings indicate that the concomitant use of antioxidants and sugar in the freezing medium can improve the quality and viabi­lity of SSCs after freezing via different mechanisms. Further studies are needed to clarify apoptosis and cell biomarkers in SSCs during freezing and thawing.

Cryoprotective Effect of Pentoxifylline on Spermatogonial Stem Cell During Transplantation into Azoospermic Torsion Mouse Model

Preserving the spermatogonial stem cells (SSCs) in long periods of time during the treatment of male infertility using stem cell banking systems and transplantation is an important issue. Therefore, this study was conducted to develop an optimal cryopreservation protocol for SSCs using 10 mM pentoxifylline (PTX) as an antioxidant in basal freezing medium. Testicular torsion-a mouse model for long-term infertility-was used to transplant fresh SSCs (n = 6), fresh SSCs treated with PTX (n = 6), cryopreserved SSCs with basal freezing medium (n = 6), and cryopreserved SSCs treated with PTX (n = 6). Eight weeks after germ cell transplantation, samples were assessed for proliferation, through evaluation of Ddx4 and Id4 markers, and differentiation via evaluation of C-Kit and Sycp3, Tnp1, Tnp2, and Prm1 markers. According to morphological and flow cytometry results, SSCs are able to form colonies and express Gfra1, Id4, α6-integrin, and β1-integrin markers. We found positive influence from PTX on proliferative and differentiative markers in SSCs transplanted to azoospermic mice. In the recipient testis, donor SSCs formed spermatogenic colonies and sperm. Respecting these data, adding pentoxifylline is a practical way to precisely cryopreserve germ cells enriched for SSCs in cryopreservation, and this procedure could become an efficient method to restore fertility in a clinical setup. However, more studies are needed to ensure its safety in the long term.

Advanced biomaterials in cell preservation: Hypothermic preservation and cryopreservation

Cell-based medicine has made great advances in clinical diagnosis and therapy for various refractory diseases, inducing a growing demand for cell preservation as support technology. However, the bottleneck problems in cell preservation include low efficiency and poor biocompatibility of traditional protectants. In this review, cell preservation technologies are categorized according to storage conditions: hypothermic preservation at 1 °C~35 °C to maintain short-term cell viability that is useful in cell diagnosis and transport, while cryopreservation at -196 °C~-80 °C to maintain long-term cell viability that provides opportunities for therapeutic cell product storage. Firstly, the background and developmental history of the protectants used in the two preservation technologies are briefly introduced. Secondly, the progress in different cellular protection mechanisms for advanced biomaterials are discussed in two preservation technologies. In hypothermic preservation, the hypothermia-induced and extracellular matrix-loss injuries to cells are comprehensively summarized, as well as the recent biomaterials dependent on regulation of cellular ATP level, stabilization of cellular membrane, balance of antioxidant defense system, and supply of mimetic ECM to prolong cell longevity are provided. In cryopreservation, cellular injuries and advanced biomaterials that can protect cells from osmotic or ice injury, and alleviate oxidative stress to allow cell survival are concluded. Last, an insight into the perspectives and challenges of this technology is provided. We envision advanced biocompatible materials for highly efficient cell preservation as critical in future developments and trends to support cell-based medicine. STATEMENT OF SIGNIFICANCE: Cell preservation technologies present a critical role in cell-based applications, and more efficient biocompatible protectants are highly required. This review categorizes cell preservation technologies into hypothermic preservation and cryopreservation according to their storage conditions, and comprehensively reviews the recently advanced biomaterials related. The background, development, and cellular protective mechanisms of these two preservation technologies are respectively introduced and summarized. Moreover, the differences, connections, individual demands of these two technologies are also provided and discussed.

Antioxidant or Apoptosis Inhibitor Supplementation in Culture Media Improves Post-Thaw Recovery of Murine Spermatogonial Stem Cells

We postulated that supplementation of antioxidant or apoptosis inhibitor in post-thaw culture media of spermatogonial stem cells (SSCs) alleviates reactive oxygen species (ROS) generation and apoptosis. Our aim was to develop an effective culture media for improving post-thaw recovery of SSCs. To determine the efficacy of supplementation with hypotaurine (HTU), α-tocopherol (α-TCP), and Z-DEVD-FMK (ZDF), we assessed the relative proliferation rate and SSC functional activity and performed a ROS generation assay, apoptosis assay, and western blotting for determination of the Bax/Bcl-xL ratio, as well as immunocytochemistry and real-time quantitative polymerase chain reaction (RT-qPCR) for SSC characterization. The relative proliferation rates with HTU 400 μM (133.7 ± 3.2%), α-TCP 400 μM (158.9 ± 3.6%), and ZDF 200 μM (133.1 ± 7.6%) supplementation were higher than that in the DMSO control (100 ± 3.6%). ROS generation was reduced with α-TCP 400 μM (0.8-fold) supplementation in comparison with the control (1.0-fold). Early apoptosis and Bax/Bcl-xL were lower with α-TCP 400 μM (2.4 ± 0.4% and 0.5-fold) and ZDF 200 μM (1.8 ± 0.4% and 0.3-fold) supplementation in comparison with the control (5.3 ± 1.4% and 1.0-fold) with normal characterization and functional activity. Supplementation of post-thaw culture media with α-TCP 400 μM and ZDF 200 μM improved post-thaw recovery of frozen SSCs via protection from ROS generation and apoptosis after cryo-thawing.

Inhibition of Caspase-8 Activity Improves Freezing Efficiency of Male Germline Stem Cells in Mice

Cryopreservation of male germline stem cells (GSCs) is an essential technique for their long-term preservation and utilization in various fields. However, the specific apoptosis pathways involved in cryoinjury during freezing remain unclear. Therefore, our study sought to identify the pathways involved in cryoinjury-induced apoptosis and thereby to improve freezing efficiency during GSC cryopreservation through the creation of a specific molecular-based cryoprotectant. The activities of caspase-8, caspase-9, caspase-3, and caspase-7 were assessed by Western blot analyses to determine the role of specific apoptosis pathways in GSC cryoinjury. Specifically, the role of a specific caspase was identified by recovery rate, relative proliferation rate, Annexin V/propidium iodide co-staining, and caspase activity using its inhibitor and activator. Moreover, the safety of the cryoprotectant was assessed by immunofluorescence and quantitative real-time polymerase chain reaction (qRT-PCR). Furthermore, the efficacy of the molecular-based cryoprotectant was assessed using frozen cells in the presence of dimethyl sulfoxide (DMSO) (control), trehalose, a caspase-8 inhibitor Z-IETD-FMK [ZIF], or a mixture of the aforementioned compounds, after which the changes in Src signaling were measured. Our results demonstrated that caspase-8 plays a major role in cryoinjury-induced apoptosis and therefore its inhibition improves freezing efficiency. Specifically, a significantly higher relative proliferation rate was observed in the Z-IETD-FMK 0.01 μM-treated cells than in the DMSO control (100% ± 6.2% vs. 189.8% ± 9.5%), with decreases in both early apoptosis (16.6% ± 2.2% vs. 7.5% ± 1.0%) and caspase-8 activity (1.0-fold vs. 0.4-fold). The relative proliferation rate was significantly higher in the cryoprotectant mixture (246.0% ± 12.2%) than other individual treatment groups (trehalose 200 mM, 189.8% ± 9.5%; Z-IETD-FMK 0.01 μM, 189.7% ± 2.2%) with no significant differences in Src signaling. Therefore, our findings provide novel insights into the development of freezing protocols to enhance GSC freezing efficiency, thereby facilitating the wider adoption of GSCs in the livestock industry and/or clinical trials.

Effect of miR-30a-5p on Apoptosis, Colonization, and Oxidative Stress Variables in Frozen-Thawed Neonatal Mice Spermatogonial Stem Cells

Cryopreservation of spermatogonial stem cells (SSCs) is a useful method for fertility preservation in preadolescent children suffering from cancer. However, SSCs may become damaged during cryopreservation due to the generation of reactive oxygen species (ROS). For this reason, various antioxidant agents have been used to protect SSCs from cryopreservation-induced damages. Recently, it has been reported that miR-30a-5p has antiapoptotic and antioxidant activity. The aim of this study was to assess the antiapoptotic and antioxidant effects of miR-30a-5p mimics in frozen-thawed SSCs. To this end, SSCs were isolated from male BALB/C mice (3-6 days old) and cultivated for 14 days. After the detection of optimum concentration, a miR-30a-5p mimic or miR-30a-5p inhibitor with Lipofectamine was transfected into SSCs and, finally, the cell groups were frozen for 1 week. After thawing, different properties, including cell viability (using MTT), colonization of SSCs (number and diameter of colonies), ROS generation (using DCFH-DA assay), levels of malondialdehyde (MDA) and superoxide dismutase (SOD), and gene expression of Bcl-2 and BAXBax (using quantitative real-time PCR), were investigated. The transfection of SSCs with miR-30a-5p mimics before the freezing-thawing process significantly increased the viability, number, and diameter of SSCs colonies. Also, the miR-30a-5p mimic decreased the levels of ROS production and MDA, but it increased the SOD levels. Moreover, the miR-30a-5p mimic decreased BAX and increased Bcl-2 expression in frozen-thawed SSCs. The transfection of SSCs with the miR-30a-5p mimic can increase cell viability and antioxidant defense, and it can decrease apoptosis during the freezing-thawing process. If SSC is able to produce spermatozoa after the transfection of miR-30a-5p and the freezing-thawing process, it can be suggested as a promising strategy for the cryopreservation of SSCs in prepubertal boys suffering from cancer.

Cryopreservation of Cyanobacteria and Eukaryotic Microalgae Using Exopolysaccharide Extracted from a Glacier Bacterium

Exopolysaccharide (EPS) has been known to be a good cryoprotective agent for bacteria, but it has not been tested for cyanobacteria and eukaryotic microalgae. In this study, we used EPS extracted from a glacier bacterium as a cryoprotective agent for the cryopreservation of three unicellular cyanobacteria and two eukaryotic microalgae. Different concentrations of EPS (10%, 15%, and 20%) were tested, and the highest concentration (20%) of EPS yielded the best growth recovery for the algal strains we tested. We also compared EPS with 5% dimethyl sulfoxide (DMSO) and 10% glycerol for the cryopreservation recovery. The growth recovery for the microalgal strains after nine months of cryopreservation was better than 5% DMSO, a well-known cryoprotectant for microalgae. A poor recovery was recorded for all the tested strains with 10% glycerol as a cryoprotective agent. The patterns of growth recovery for most of these strains were similar after 5 days, 15 days, and 9 months of cryopreservation. Unlike common cryopreservants such as DMSO or methanol, which are hazardous materials, EPS is safe to handle. We demonstrate that the EPS from a psychrotrophic bacterium helped in the long-term cryopreservation of cyanobacteria and microalgae, and it has the potential to be used as natural cryoprotective agent for other cells.

Effect of a Freezing Medium Containing Melatonin on Markers of Pre-meiotic and Post-meiotic Spermatogonial Stem Cells (SSCs) After Transplantation in an Azoospermia Mouse Model Due to Testicular Torsion

Spermatogonial stem cells (SSCs) are essential to the initiation of spermatogenesis. Cryopreservation, long-term maintenance, and auto-transplantation of SSCs could be a new treatment for infertility. The aim of this study was to add melatonin to the basic freezing medium and to evaluate its effect on the efficiency of the thawed SSCs after transplantation into the testicles of azoospermic mice. SSCs were isolated from newborn NMRI mice, and the cells were enriched to assess morphological features. The thawed SSCs were evaluated for survival, apoptosis, and ROS level before transplantation, and the proliferation (MVH and ID4) and differentiation (c-Kit, SCP3, TP1, TP2, and Prm1) markers of SSCs were examined using immunofluorescence, western blot, and quantitative real-time polymerase chain reaction (PCR) after transplantation. It was found that the survival rate of SSCs after thawing was significantly higher in the melatonin group compared with the cryopreservation group containing basic freezing medium, and the rate of apoptosis and level of ROS production also decreased significantly in the cryopreservation group with melatonin (p < 0.05). The expression of proliferation and differentiation markers after transplantation was significantly higher in the cryopreservation group with melatonin compared to the cryopreservation group (p < 0.05). The results suggest that adding melatonin to the basic freezing medium can effectively protect the SSCs by increasing the viability and reducing the ROS production and apoptosis and improve the transplantation efficiency of SSCs after cryopreservation, which will provide a significant suggestion for fertility protection in the clinic.

Fine-tuned dehydration by trehalose enables the cryopreservation of RBCs with unusually low concentrations of glycerol

We regulated the amount of trehalose and combined it with glycerol to achieve unusually low glycerol concentrations in the cryopreservation of RBCs compared with traditional methods.

The combination of trehalose and glycerol: an effective and non-toxic recipe for cryopreservation of human adipose-derived stem cells

Background

Adipose-derived stem cells (ADSCs) promote tissue regeneration and repair. Cryoprotective agents (CPAs) protect cells from cryodamage during cryopreservation. Safe and efficient cryopreservation of ADSCs is critical for cell-based therapy in clinical applications. However, most CPAs are used at toxic concentrations, limiting their clinical application.

Objective

The aim of this study is to develop a non-toxic xeno-free novel CPA aiming at achieving high-efficiency and low-risk ADSC cryopreservation.

Methods

We explored different concentrations of trehalose (0.3 M, 0.6 M, 1.0 M, and 1.25 M) and glycerol (10%, 20%, and 30% v/v) for optimization and evaluated and compared the outcomes of ADSCs cryopreservation between a combination of trehalose and glycerol and the commonly used CPA DMSO (10%) + FBS (90%). All samples were slowly frozen and stored in liquid nitrogen for 30 days. The effectiveness was evaluated by the viability, proliferation, migration, and multi-potential differentiation of the ADSCs after thawing.

Results

Compared with the groups treated with individual reagents, the 1.0 M trehalose (Tre) + 20% glycerol (Gly) group showed significantly higher efficiency in preserving ADSC activities after thawing, with better outcomes in both cell viability and proliferation capacity. Compared with the 10% DMSO + 90% FBS treatment, the ADSCs preserved in 1.0 M Tre + 20% Gly showed similar cell viability, surface markers, and multi-potential differentiation but a significantly higher migration capability. The results indicated that cell function preservation can be improved by 1.0 M Tre + 20% Gly.

Conclusions

The 1.0 M Tre + 20% Gly treatment preserved ADSCs with a higher migration capability than 10% DMSO + 90% FBS and with viability higher than that with trehalose or glycerol alone but similar to that with 10% DMSO + 90% FBS and fresh cells. Moreover, the new CPA achieves stemness and multi-potential differentiation similar to those in fresh cells. Our results demonstrate that 1.0 M Tre + 20% Gly can more efficiently cryopreserve ADSCs and is a non-toxic CPA that may be suitable for clinical applications.

Effective cryopreservation protocol for preservation of male primate (Macaca fascicularis) prepubertal fertility

RESEARCH QUESTION

Can specimen types (cells versus tissues) and additive cryoprotectant agents contribute to efficient cryopreservation of primate spermatogonial stem cells (SSC)?

DESIGN

Testicular tissues or cells from four prepubertal monkeys were used in this study. The freezing efficacy of testicular tissue was compared with cell suspensions using conventional freezing media (1.4 mol/l dimethyl sulfoxide [DMSO]) and the efficacy of cryoprotectant additives (1.4 mol/l DMSO combined with trehalose 200 mmol/l, hypotaurine 14 mmol/l, necrostatin-1 50 µmol/l or melatonin 100 µmol/l) was evaluated in testicular tissue freezing.

RESULTS

The survival rate (46.0 ± 4.8% versus 33.7 ± 6.0%; P = 0.0286) and number of recovered cells (5.0 ± 1.5 × 10⁶ cells/g versus 0.7 ± 0.8 × 10⁶ cells/g; P = 0.0286) were significantly higher in frozen tissues than in frozen cell suspensions. After tissue freezing, a higher number of recovered PGP9.5⁺ cells were observed with 200 mmol/l trehalose treatment than in DMSO controls (2.4 ± 0.6 × 10⁶ cells/g versus 1.1 ± 0.3 × 10⁶ cells/g; P = 0.0164). Normal establishment of donor-derived colony was observed in SSC after tissue freezing with 200 mmol/l trehalose.

CONCLUSIONS

Testicular tissue freezing is more effective than single cell suspension freezing for higher recovery of undifferentiated spermatogonia. Moreover, it was verified that slow freezing using 200 mmol/l trehalose, 1.4 mol/l DMSO and 10% KnockOut™ Serum Replacement in Dulbecco's phosphate-buffered saline is an effective cryopreservation protocol for primate testicular tissue.

Effect of Equilibration Time and Temperature on Murine Spermatogonial Stem Cell Cryopreservation

Cryopreservation of spermatogonial stem cells (SSCs) is essential for preservation of valuable livestock and clinical applications. Although optimal equilibration of cryoprotectants has emerged as a promising approach to improve the cryopreservation efficiency, standard equilibration protocols have not yet been considered in cryopreservation of SSCs. This study aimed to establish a standard equilibration protocol to improve the cryopreservation efficiency of murine germ cells enriched for SSCs. After time- and temperature-dependent equilibration, the germ cells were cryopreserved with 10% dimethyl sulfoxide (DMSO) and 200 mM trehalose. To investigate cryopreservation efficiency at different equilibration conditions, the survival and proliferation rates were assessed after thawing, and then, cytotoxicity and intracellular trehalose quantification were analyzed. Protein (PLZF, GFRα1, VASA, and c-Kit) and gene (Bcl6b, Erm, Dazl, and Sycp1) expression was determined using immunofluorescence and real-time quantitative polymerase chain reaction (RT-qPCR), respectively. The proliferation rate increased significantly following equilibration for 20 minutes at room temperature (RT; 163.7% ± 24.6%) or 4°C (269.0% ± 18.2%). Cytotoxicity was reduced in 10% DMSO with 200 mM trehalose compared with that of 10% DMSO alone. Also, intracellular trehalose was observed after equilibration. The immunofluorescence and RT-qPCR data revealed that the murine germ cells enriched for SSCs retained their self-renewal ability after cryopreservation following equilibration. The most effective protocol was equilibration with 10% DMSO and 200 mM trehalose for 20 minutes at RT or 4°C, which is due to synergistic effects of intracellular and extracellular trehalose. This improved methodology will contribute toward the development of a standardized freezing protocol for murine germ cells enriched for SSCs and thereby expand their application in various fields.

Effects of Me2SO and Trehalose on the Cell Viability, Proliferation, and Bcl-2 Family Gene (BCL-2, BAX, and BAD) Expression in Cryopreserved Human Breast Cancer Cells

Long-term cryopreservation of the viability and metabolic state of cells in cancer cell/tissue specimens has significant implications for diagnostic verification of disease progression in cancer patients and selection of effective treatment options via development of the patient-derived xenograft (PDX) models for drug screening. The purpose of this study is to investigate the effects of cryoprotectant agents (CPAs) on the expression of BCL-2 family genes (BCL-2, BAX, and BAD) that are involved in the growth and development of breast cancers. MCF-7 cells were cryopreserved in Dulbecco's modified Eagle's medium (DMEM) with 20% (v/v) fetal bovine serum, using 10% (v/v) Me₂SO (dimethyl sulfoxide, DMSO) or 7.5% (v/v) Me₂SO with 100is-300 mM trehalose as cryoprotectant solutions. After storage at -80°C for 7 days, the cells were thawed for evaluation. The use of Me₂SO and trehalose has affected cell survival, proliferation, apoptotic state, as well as BCL-2 family gene expression. The conventional 10% (v/v) Me₂SO method yields ∼80% post-thaw cell survival and good cell proliferation, but it drastically alters the pattern of the BCL-2 family gene expression. The antiapoptotic gene BCL-2 is downregulated, whereas two proapoptotic genes BAX and BAD are upregulated. The partial substitution of Me₂SO with 200 or 300 mM trehalose enhances cell proliferation of survived cells after cryopreservation. The presence of trehalose upregulates the expression of both the antiapoptotic gene BCL-2 and proapoptotic genes BAX and BAD. Cryopreservation could tip off the checkpoint of the apoptotic pathway regulated by the BCL-2 family members, and the effect may be protectant dependent. The findings of this study demonstrate the importance of paying attention to the potential change of gene expression and metabolic state of cancer cells after cryopreservation in an attempt to development of the PDX models from cryopreserved cancer cells or tissue specimens.

Trehalose protects testicular tissue of dairy goat upon cryopreservation

The aim of this study was to investigate whether the addition of trehalose to cryomedia reduces cellular damage and improves gene expression in cryopreserved dairy goat testicular tissues. Testicular tissues were cryopreserved in cryomedia without or with trehalose at a concentration of 5%, 10%, 15%, 20% or 25%. Cryopreserved testicular tissues were analysed for TUNEL-positive cell number, expression of BAX, BCL-2, CREM, BOULE and HSP70-2. Isolated Leydig cells from cryopreserved tissue were cultured, and spent medium was evaluated for testosterone level. The results showed that though the TUNEL-positive cell number increased in cryopreserved testicular tissues, the presence of trehalose reduced apoptotic cell number significantly. Quantitative real-time polymerase chain reaction results showed that although the expression of BAX was upregulated following cryopreservation, the presence of trehalose downregulates it in cryopreserved testicular tissues. Expression of BCL-2, CREM, BOULE and HSP70-2 was downregulated following cryopreservation but the presence of trehalose significantly upregulated their expression in cryopreserved testicular tissues. Leydig cells isolated from testicular tissues cryopreserved with trehalose produced higher testosterone than the one without it (control). These results suggest that trehalose has a protective role in cryopreservation of dairy goat testicular tissue, and the most suitable trehalose concentration for cryopreservation is 15%.

The roles of reactive oxygen species and antioxidants in cryopreservation

Cryopreservation has facilitated advancement of biological research by allowing the storage of cells over prolonged periods of time. While cryopreservation at extremely low temperatures would render cells metabolically inactive, cells suffer insults during the freezing and thawing process. Among such insults, the generation of supra-physiological levels of reactive oxygen species (ROS) could impair cellular functions and survival. Antioxidants are potential additives that were reported to partially or completely reverse freeze-thaw stress-associated impairments. This review aims to discuss the potential sources of cryopreservation-induced ROS and the effectiveness of antioxidant administration when used individually or in combination.

Large-Scale Generation and Characterization of Homogeneous Populations of Migratory Cortical Interneurons from Human Pluripotent Stem Cells

During development, cortical interneurons (cINs) are generated from the ventral telencephalon, robustly migrate to the dorsal telencephalon, make local synaptic connections, and critically regulate brain circuitry by inhibiting other neurons. Thus, their abnormality is associated with various brain disorders. Human pluripotent stem cell (hPSC)-derived cINs can provide unlimited sources with which to study the pathogenesis mechanism of these disorders as well as provide a platform to develop novel therapeutics. By employing spinner culture, we could obtain a >10-fold higher yield of cIN progenitors compared to conventional culture without affecting their phenotype. Generated cIN spheres can be maintained feeder-free up to 10 months and are optimized for passaging and cryopreservation. In addition, we identified a combination of chemicals that synchronously matures generated progenitors into SOX6⁺KI67⁻ migratory cINs and extensively characterized their maturation in terms of metabolism, migration, arborization, and electrophysiology. When transplanted into mouse brains, chemically matured migratory cINs generated grafts that efficiently disperse and integrate into the host circuitry without uncontrolled growth, making them an optimal cell population for cell therapy. Efficient large-scale generation of homogeneous migratory cINs without the need of feeder cells will play a critical role in the full realization of hPSC-derived cINs for development of novel therapeutics.

Trehalose to cryopreserve human pluripotent stem cells

The successful exploitation of human pluripotent stem cells (hPSCs) for research, translational or commercial reasons requires the implementation of a simple and efficient cryopreservation method. Cryopreservation is usually performed with dimethylsulphoxide (DMSO), in addition to animal proteins. However, even at sub-toxic levels, DMSO diminishes the pluripotency capacity of hPSCs and affects their epigenetic system by acting on the three DNA methyltransferases (Dnmts) and histone modification enzymes. Our study aimed to test trehalose-based cryosolutions containing ethylene glycol (EG) or glycerol (GLY) on hESCs RC17, hiPSCs CTR2#6 and long-term neuroepithelial-like stem cells (lt-NES) AF22. Here, we demostrate the effectiveness of these cryosolutions in hPSCs by showing an acceptable rate of cell viability and high stability compared to standard 10% DMSO freezing medium (CS10). All cell lines retained their morphology, self renewal potential and pluripotency, and none of the cryosolutions affected their differentiation potential. Genotoxicity varied among different stem cells types, while trehalose-based cryopreservation did not sensibly alter the homeostasis of endoplasmic reticulum (ER). This study provides evidence that pluripotent and neural stem cells stored in trehalose alone or with other cryoprotectants (CPAs) maintain their functional properties, indicating their potential use in cell therapies if produced in good manufacturing practice (GMP) facility.

Developmental competence of in vitro matured ovine oocytes vitrified in solutions with different concentrations of trehalose

This study aimed to determine the optimum concentration of trehalose in solutions used for vitrification of in vitro matured (IVM) ovine oocytes. IVM oocytes were randomly divided into four experimental (vitrified) and one control (fresh) groups. Experimental groups were treated with different concentrations (0.0, 0.25, 0.5 and 1.0 M) of trehalose. After warming, some viable oocytes were exposed to 0.25% pronase to test zona pellucida hardening, whereas the others were fertilized and cultured in vitro for 8 days to evaluate their developmental competence. Blastocysts quality was assessed by differential staining and TUNEL test. Survival and developmental rates of oocytes vitrified in the presence of 0.5 M trehalose were significantly higher than those of the other vitrified groups. Furthermore, there was a significant difference between fresh and vitrified groups in total blastocyst rate. Analysis of blastocysts quality also revealed a significant difference between the group treated with 0.5 M trehalose and other groups in terms of apoptotic index. Furthermore,zona pellucida digestion time period was longer in trehalose-free (0.0 M) group compared to other groups. In conclusion, we found that IVM ovine oocytes vitrified in solutions containing 0.5 M trehalose are fertilization-competent and are able to produce good-quality blastocysts with an apoptotic index comparable to that of the fresh oocytes. Therefore, 0.5 M may be considered the optimum concentration of trehalose to be used in solutions prepared for vitrification of oocytes.

Predehydration and Ice Seeding in the Presence of Trehalose Enable Cell Cryopreservation

Conventional approaches for cell cryopreservation require the use of toxic membrane-penetrating cryoprotective agents (pCPA), which limits the clinical application of cryopreserved cells. Here, we show intentionally induced ice formation at a high subzero temperature (> -10 °C) during cryopreservation, which is often referred to as ice seeding, could result in significant cell injury in the absence of any pCPA. This issue can be mitigated by predehydrating cells using extracellular trehalose to their minimal volume with minimized osmotically active water before ice seeding. We further observe that ice seeding can minimize the interfacial free energy that drives the devastating ice recrystallization-induced cell injury during warming cryopreserved samples. Indeed, by combining predehydration using extracellular trehalose with ice seeding at high subzero temperatures, high cell viability or recovery is achieved for fibroblasts, adult stem cells, and red blood cells after cryopreservation without using any pCPA. The pCPA-free technology developed in this study may greatly facilitate the long-term storage and ready availability of living cells, tissues, and organs that are of high demand by modern cell-based medicine.

Long-term culture-induced phenotypic difference and efficient cryopreservation of small intestinal organoids by treatment timing of Rho kinase inhibitor

AIM

To investigate a suitable long-term culture system and optimal cryopreservation of intestinal organoid to improve organoid-based therapy by acquiring large numbers of cells.

METHODS

Crypts were isolated from jejunum of C57BL/6 mouse. Two hundred crypts were cultured in organoid medium with either epidermal growth factor/Noggin/R-spondin1 (ENR) or ENR/CHIR99021/VPA (ENR-CV). For subculture, organoids cultured on day 7 were passaged using enzyme-free cell dissociation buffer (STEMCELL Technologies). The passage was performed once per week until indicated passage. For cryopreservation, undissociated and dissociated organoids were resuspended in freezing medium with or without Rho kinase inhibitor subjected to different treatment times. The characteristics of intestinal organoids upon extended passage and freeze-thaw were analyzed using EdU staining, methyl thiazolyl tetrazolium assay, qPCR and time-lapse live cell imaging.

RESULTS

We established a three-dimensional culture system for murine small intestinal organoids using ENR and ENR-CV media. Both conditions yielded organoids with a crypt-villus architecture exhibiting Lgr5⁺ cells and differentiated intestinal epithelial cells as shown by morphological and biochemical analysis. However, during extended passage (more than 3 mo), a comparative analysis revealed that continuous passaging under ENR-CV conditions, but not ENR conditions induced phenotypic changes as observed by morphological transition, reduced numbers of Lgr5⁺ cells and inconsistent expression of markers for differentiated intestinal epithelial cell types. We also found that recovery of long-term cryopreserved organoids was significantly affected by the organoid state, i.e., whether dissociation was applied, and the timing of treatment with the Rho-kinase inhibitor Y-27632. Furthermore, the retention of typical morphological characteristics of intestinal organoids such as the crypt-villus structure from freeze-thawed cells was observed by live cell imaging.

CONCLUSION

The maintenance of the characteristics of intestinal organoids upon extended passage is mediated by ENR condition, but not ENR-CV condition. Identified long-term cryopreservation may contribute to the establishment of standardized cryopreservation protocols for intestinal organoids for use in clinical applications.

Trehalose, an easy, safe and efficient cryoprotectant for the parasitic protozoan Trypanosoma brucei

Trehalose, a non-permeating cryoprotective agent (CPA), has been documented as less toxic and highly efficient at cryopreserving different kinds of cells or organisms. In the present study, trehalose was evaluated for its application in cryopreservation of both Trypanosoma brucei procyclic and bloodstream form cells. The cryopreservation efficiency was determined by the motility of trypanosomes after thawing, as well as a subsequent recovery and infectivity assessment. The viability of trypanosomes from cultivation that were frozen in a serial concentrations of trehalose showed similar results to classical CPAs of glycerol and DMSO. Nevertheless, trypanosomes cryopreserved in 0.2M trehalose showed the best growth characteristic during subsequent cultivation. In addition, CPA cocktails with trehalose and permeating CPA glycerol or DMSO were developed and evaluated. Interestingly, trypanosomes in host (mouse) blood cryopreserved in 0.4M trehalose plus 5% glycerol showed higher infectivity than those preserved in trehalose/DMSO cocktails as well as individually. Further investigations showed that, in comparison with slow freezing at -80°C, flash freezing in liquid nitrogen provided better cryopreservation for bloodstream form cells than slow freezing. In conclusion, trehalose is an easy, safe and efficient CPA for cryopreservation of T. brucei and potentially for other protozoan species and cells.

Cryopreservation of testicular tissue or testicular cell suspensions: a pivotal step in fertility preservation

BACKGROUND

Germ cell depletion caused by chemical or physical toxicity, disease or genetic predisposition can occur at any age. Although semen cryopreservation is the first reflex for preserving male fertility, this cannot help out prepubertal boys. Yet, these boys do have spermatogonial stem cells (SSCs) that able to produce sperm at the start of puberty, which allows them to safeguard their fertility through testicular tissue (TT) cryopreservation. SSC transplantation (SSCT), TT grafting and recent advances in in vitro spermatogenesis have opened new possibilities to restore fertility in humans. However, these techniques are still at a research stage and their efficiency depends on the amount of SSCs available for fertility restoration. Therefore, maintaining the number of SSCs is a critical step in human fertility preservation. Standardizing a successful cryopreservation method for TT and testicular cell suspensions (TCSs) is most important before any clinical application of fertility restoration could be successful.

OBJECTIVE AND RATIONALE

This review gives an overview of existing cryopreservation protocols used in different animal models and humans. Cell recovery, cell viability, tissue integrity and functional assays are taken into account. Additionally, biosafety and current perspectives in male fertility preservation are discussed.

SEARCH METHODS

An extensive PubMED and MEDline database search was conducted. Relevant studies linked to the topic were identified by the search terms: cryopreservation, male fertility preservation, (immature)testicular tissue, testicular cell suspension, spermatogonial stem cell, gonadotoxicity, radiotherapy and chemotherapy.

OUTCOMES

The feasibility of fertility restoration techniques using frozen-thawed TT and TCS has been proven in animal models. Efficient protocols for cryopreserving human TT exist and are currently applied in the clinic. For TCSs, the highest post-thaw viability reported after vitrification is 55.6 ± 23.8%. Yet, functional proof of fertility restoration in the human is lacking. In addition, few to no data are available on the safety aspects inherent to offspring generation with gametes derived from frozen-thawed TT or TCSs. Moreover, clarification is needed on whether it is better to cryopreserve TT or TCS.

WIDER IMPLICATIONS

Fertility restoration techniques are very promising and expected to be implemented in the clinic in the near future. However, inter-center variability needs to be overcome and the gametes produced for reproduction purposes need to be subjected to safety studies. With the perspective of a future clinical application, there is a dire need to optimize and standardize cryopreservation and safety testing before using frozen-thawed TT of TCSs for fertility restoration.

Effect of Antioxidants and Apoptosis Inhibitors on Cryopreservation of Murine Germ Cells Enriched for Spermatogonial Stem Cells

Spermatogonial stem cells (SSCs) are germline stem cells that serve as the foundation of spermatogenesis to maintain fertility throughout a male’s lifetime. To treat male infertility using stem cell banking systems and transplantation, it is important to be able to preserve SSCs for long periods of time. Therefore, this study was conducted to develop an optimal cryopreservation protocol for SSCs using antioxidants and apoptosis inhibitors in freezing medium. No differences were observed compared to controls when SSCs were cryopreserved in the presence of apoptosis inhibitors by themselves. However, mouse germ cells cryopreserved in basal medium containing the antioxidant hypotaurine (14 mM) resulted in significantly greater proliferation potential and mitochondrial activity. Furthermore, treatment groups with combinations containing 200 mM trehalose and 14 mM hypotaurine showed higher proliferation rates compared to controls. In addition, several serum free conditions were evaluated for SSC cryopreservation. Treatment media containing 10% or 20% knockout serum replacement resulted in similar cryopreservation results compared to media containing FBS. SSC transplantation was also performed to confirm the functionality of SSCs frozen in 14 mM hypotaurine. Donor SSCs formed normal spermatogenic colonies and sperm in the recipient testis. These data indicate that inclusion of 14 mM hypotaurine in cryopreservation media is an effective way to efficiently cryopreserve germ cells enriched for SSCs and that knockout serum replacement can replace FBS in germ cell cryopreservation media.

Cryopreservation of Human Mucosal Leukocytes

Background

Understanding how leukocytes in the cervicovaginal and colorectal mucosae respond to pathogens, and how medical interventions affect these responses, is important for developing better tools to prevent HIV and other sexually transmitted infections. An effective cryopreservation protocol for these cells following their isolation will make studying them more feasible.

Methods and Findings

To find an optimal cryopreservation protocol for mucosal mononuclear leukocytes, we compared cryopreservation media and procedures using human vaginal leukocytes and confirmed our results with endocervical and colorectal leukocytes. Specifically, we measured the recovery of viable vaginal T cells and macrophages after cryopreservation with different cryopreservation media and handling procedures. We found several cryopreservation media that led to recoveries above 75%. Limiting the number and volume of washes increased the fraction of cells recovered by 10–15%, possibly due to the small cell numbers in mucosal samples. We confirmed that our cryopreservation protocol also works well for both endocervical and colorectal leukocytes. Cryopreserved leukocytes had slightly increased cytokine responses to antigenic stimulation relative to the same cells tested fresh. Additionally, we tested whether it is better to cryopreserve endocervical cells on the cytobrush or in suspension.

Conclusions

Leukocytes from cervicovaginal and colorectal tissues can be cryopreserved with good recovery of functional, viable cells using several different cryopreservation media. The number and volume of washes has an experimentally meaningful effect on the percentage of cells recovered. We provide a detailed, step-by-step protocol with best practices for cryopreservation of mucosal leukocytes.

Beyond the mouse monopoly: studying the male germ line in domestic animal models

Spermatogonial stem cells (SSCs) are the foundation of spermatogenesis and essential to maintain the continuous production of spermatozoa after the onset of puberty in the male. The study of the male germ line is important for understanding the process of spermatogenesis, unravelling mechanisms of stemness maintenance, cell differentiation, and cell-to-cell interactions. The transplantation of SSCs can contribute to the preservation of the genome of valuable individuals in assisted reproduction programs. In addition to the importance of SSCs for male fertility, their study has recently stimulated interest in the generation of genetically modified animals because manipulations of the male germ line at the SSC stage will be maintained in the long term and transmitted to the offspring. Studies performed mainly in the mouse model have laid the groundwork for facilitating advancements in the field of male germ line biology, but more progress is needed in nonrodent species in order to translate the technology to the agricultural and biomedical fields. The lack of reliable markers for isolating germ cells from testicular somatic cells and the lack of knowledge of the requirements for germ cell maintenance have precluded their long-term maintenance in domestic animals. Nevertheless, some progress has been made. In this review, we will focus on the state of the art in the isolation, characterization, culture, and manipulation of SSCs and the use of germ cell transplantation in domestic animals.

Vitrified canine testicular cells allow the formation of spermatogonial stem cells and seminiferous tubules following their xenotransplantation into nude mice

Belgian Malinois (BM), one of the excellent military dog breeds in South Korea, is usually castrated before sexual maturation. Therefore, the transfer of their genetic features to the next generation is difficult. To overcome this, testicular cells from 4-month-old BMs were frozen. Testicular cells were thawed after 3 months and cultured in StemPro-34 medium. Spermatogonial stem cell (SSC) characteristics were determined by the transplantation of the cultured germ cell-derived colonies (GDCs) into empty testes, containing only several endogenous SSCs and Sertoli cells, of immunodeficient mice, 4 weeks after busulfan treatment. Following the implantation, the transplanted cells localized in the basement membrane of the seminiferous tubules, and ultimately colonized the recipient testes. Xenotransplantation of GDCs together with testicular somatic cells conjugated with extracellular matrix (ECM), led to the formation of de novo seminiferous tubules. These seminiferous tubules were mostly composed of Sertoli cells. Some germ cells were localized in the basement membrane of seminiferous tubules. This study revealed that BM-derived SSCs, obtained from the castrated testes, might be a valuable tool for the transfer of BM genetic features to the next generation.

Successful cryopreservation of whole sheep ovary by using DMSO-free cryoprotectant

PURPOSE

The study aims to assess the protective effects of dimethyl sulfoxide (DMSO)-free solution based on trehalose on the cryopreservation of a whole sheep ovary and evaluate its use as an efficient cryoprotectant.

METHOD

Twenty-one ovaries collected from 6- to 8-month-old non-pregnant female sheep were randomly distributed into three groups, namely, a fresh group, a DMSO-free group, and a DMSO group. The morphology, cell apoptosis (by hematoxylin and eosin (HE) staining and terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) assay), and mRNA transcript of Bcl-2-associated X protein (BAX) and cold inducible RNA-binding protein (CIRP) (by real-time PCR) of the thawed sheep ovaries and fresh controls were tested to establish a criterion for appraising the results of the cryopreservation.

RESULTS

(i) The histological assessment indicated that the structure of the DMSO-free ovaries remained largely intact and comparable to those of the fresh control groups; whereas, significant damage was observed in the ovaries of the DMSO group (P < 0.05). (ii) The TUNEL assay and mRNA transcript of the BAX assessment showed that the apoptosis parameter in the fresh group was the lowest among all the groups (P < 0.05), and the parameter in the DMSO-free group was significantly lower than that in the DMSO group (P < 0.05). (iii) The level of the CIRP transcripts increased the most in the DMSO-free group followed by the DMSO group and the fresh control group (P < 0.05).

CONCLUSIONS

These results indicate that a DMSO-free cryoprotectant solution, especially a trehalose cryoprotectant, is an efficient cryoprotectant and has a beneficial effect on the cryopreservation of whole sheep ovaries.

Freezing tolerance of sea urchin embryonic cells: Differentiation commitment and cytoskeletal disturbances in culture

This study focuses on the freezing tolerance of sea urchin embryonic cells. To significantly reduce the loss of physiological activity of these cells that occurs after cryopreservation and to study the effects of ultra-low temperatures on sea urchin embryonic cells, we tested the ability of the cells to differentiate into spiculogenic or pigment directions in culture, including an evaluation of the expression of some genes involved in pigment differentiation. A morphological analysis of cytoskeletal disturbances after freezing in a combination of penetrating (dimethyl sulfoxide and ethylene glycol) and non-penetrating (trehalose and polyvinylpyrrolidone) cryoprotectants revealed that the distribution pattern of filamentous actin and tubulin was similar to that in the control cultures. In contrast, very rare spreading cells and a small number of cells with filamentous actin and tubulin were detected after freezing in the presence of only non-penetrating cryoprotectants. The largest number of pigment cells was found in cultures frozen with trehalose or trehalose and dimethyl sulfoxide. The ability to induce the spicule formation was lost in the cells frozen only with non-penetrating cryoprotectants, while it was maximal in cultures frozen in a cryoprotective mixture containing both non-penetrating and penetrating cryoprotectants (particularly, when ethylene glycol was present). Using different markers for cell state assessment, an effective cryopreservation protocol for sea urchin cells was developed: three-step freezing with a low cooling rate (1-2°C/min) and a combination of non-penetrating and penetrating cryoprotectants made it possible to obtain a high level of cell viability (up to 65-80%).

Phenotypic and functional characterization of long-term cryopreserved human adipose-derived stem cells

Cryopreservation represents an effective technique to maintain the functional properties of human adipose-derived stem cells (ASCs) and allows pooling of cells via long-term storage for clinical applications, e.g., cell-based therapies. It is crucial to reduce freezing injury during the cryopreservation process by loading the ASCs with the optimum concentration of suitable cryoprotective agents (CPAs). In this study, human ASCs were preserved for 3 months in different combinations of CPAs, including 1) 0.25 M trehalose; 2) 5% dimethylsulfoxide (DMSO); 3) 10% DMSO; 4) 5% DMSO + 20% fetal bovine serum (FBS); 5) 10% DMSO + 20% FBS; 6) 10% DMSO + 90% FBS. Interestingly, even with a reduction of DMSO to 5% and without FBS, cryopreserved ASCs maintained high cell viability comparable with standard cryomedium (10% DMSO + 90% FBS), with normal cell phenotype and proliferation rate. Cryopreserved ASCs also maintained their differentiation capability (e.g., to adipocytes, osteocytes and chondrocytes) and showed an enhanced expression level of stemness markers (e.g., NANOG, OCT-4, SOX-2 and REX-1). Our findings suggest that 5% DMSO without FBS may be an ideal CPA for an efficient long-term cryopreservation of human ASCs. These results aid in establishing standardized xeno-free long-term cryopreservation of human ASCs for clinical applications.

Effect of the addition of six antioxidants on sperm motility, membrane integrity and mitochondrial function in red seabream (Pagrus major) sperm cryopreservation

The present study was to evaluate the effects of six antioxidants on frozen-thawed sperm motility, viability, membrane integrity and mitochondrial function in red seabream (Pagrus major) by computer-assisted sperm analysis system and flow cytometry, respectively. All the parameters tested in this study were determined using one-way ANOVA and identified using the SNK test (P < 0.05). The results demonstrated that on the first day, the highest motility and longevity occurred in 100 mM trehalose (78.34 ± 3.41%, 29 ± 4.00 days) and 50 mM taurine (77.46 ± 1.54%, 29.33 ± 4.04 days), followed by 25 mM vitamin C (79.03 ± 5.37 %, 17 ± 1.00 days), 25 mM vitamin E (69.64 ± 1.64%, 27.67 ± 1.53 days) and 25 mM vitamin A (78.89 ± 2.81%, 9.33 ± 1.53 days), which were all higher than frozen-thawed sperm without antioxidant (control) (66.80 ± 5.55, 5.67 ± 1.15 days). Especially, the percentages of class A sperm with the addition of 100 mM trehalose (40.39 ± 5.20%) and 50 mM taurine (37.78 ± 3.22%) were significantly improved compared to the control (19.63 ± 5.44%). The viability of all groups on the third and sixth day showed a similar trend. Moreover, during the 4 °C storage process, the decrease of frozen-thawed sperm motility was closely associated with the decrease in membrane integrity and mitochondrial function. In conclusion, the present study indicated that antioxidant (100 mM trehalose and 50 mM taurine) provided the most pronounced protective effect in improving frozen-thawed quality of red seabream sperm. The addition of antioxidant may be capable of scavenging the ROS generated during the cryopreservation process and 4 °C storage.

Transporting Cells in Semi-Solid Gel Condition and at Ambient Temperature

Mammalian cells including human cancer cells are usually transported in cryovials on dry ice or in a liquid nitrogen vapor shipping vessel between different places at long distance. The hazardous nature of dry ice and liquid nitrogen, and the associated high shipping cost strongly limit their routine use. In this study, we tested the viability and properties of cells after being preserved or shipped over long distance in Matrigel mixture for different days. Our results showed that cells mixed with Matrigel at suitable ratios maintained excellent viability (>90%) for one week at room temperature and preserved the properties such as morphology, drug sensitivity and metabolism well, which was comparable to cells cryopreserved in liquid nitrogen. We also sent cells in the Matrigel mixture via FedEx service to different places at ambient temperature. Upon arrival, it was found that over 90% of the cells were viable and grew well after replating. These data collectively suggested that our Matrigel-based method was highly convenient for shipping live cells for long distances in semi-solid gel condition and at ambient temperature.

Medium composition for effective slow freezing of embryonic cell lines derived from marine medaka (Oryzias dancena)

This study was conducted to identify optimal medium composition for freezing Oryzias dancena embryonic cell lines. Different freezing media consisting of various concentration of dimethyl sulfoxide (DMSO), fetal bovine serum (FBS), and trehalose were prepared and long-term cultured embryonic cell line was frozen in each freezing medium by conventional slow freezing program for 7 days. Through measurement of viability and growth of post-thaw cells frozen in each freezing medium, it was determined that optimal composition of three components was 10 % DMSO, 20 % FBS, and 0.1 M trehalose. The post-thaw cells frozen in optimal freezing medium showed similar morphology and growth rate with non-frozen cells. Next, this condition was applied to two different sets of experiment; (1) freezing of the same cells during expanded period (57 days) and (2) freezing of short-term cultured cells from other batches for 7 days. The viability of post-thaw cells was significantly low and comparable in set 1 and 2, respectively, when compared with the result of long term-cultured cells frozen in optimal freezing medium for 7 days and similar morphology and growth rate with non-frozen counterparts were detected in the post-thaw cells from both sets. In conclusion, this study first reports the optimal medium composition for freezing O. dancena embryonic cells, which can contribute to fish species preservation as well as improvement of cell-based biotechnology by providing stable cell storage.

Effect of sugar molecules on the cryopreservation of mouse spermatogonial stem cells

OBJECTIVE

To study the influence of sugars and establish a serum-free freezing method for the cryopreservation of spermatogonial stem cells (SSCs).

DESIGN

Animal study.

SETTING

University laboratory.

ANIMAL(S)

C57BL/6-TgEGFP, C57BL/6 mice.

INTERVENTION(S)

Germ cells enriched from testis cells were frozen using standard freezing medium containing sugars, including monosaccharides, disaccharides, and trisaccharides at 50, 100, and 200 mM, respectively. To study the feasibility of establishing a serum-free freezing method, fetal bovine serum was substituted with knockout serum replacement.

MAIN OUTCOME MEASURE(S)

Freeze-thawed germ cells were evaluated for recovery rate, proliferation capacity, and stem cell activity after transplantation to recipient testes.

RESULT(S)

Supplementation of freezing medium with 200 mM disaccharide is an effective method for cryopreservation of SSCs. Trehalose is the most effective cryoprotectant among all the sugars tested and only lactose was comparable to trehalose. Our proliferation and transplantation data show that serum-free freezing can be achieved in freezing medium supplemented with 200 mM trehalose, 10% knockout serum replacement, and 10% dimethyl sulfoxide (DMSO) for cryopreservation of SSCs.

CONCLUSION(S)

These findings raise the possibility of effectively banking frozen SSCs from various species, including humans, in a traditional serum-free medium for germ cell research and male infertility treatments.