Key Issues Related to Cryopreservation and Storage of Stem Cells and Cancer Stem Cells: Protecting Biological Integrity

Effect of paternal aging and vitrification on mitochondrial DNA copy number and telomere length of mouse blastocysts

In this study, we examined the effects of paternal aging on the mitochondrial DNA copy number (mt-cn), telomere length (TL), and gene expression in mouse embryos. The effects of vitrification on the mt-cn and TL of the embryos derived from young and aged male parents (YF and AF, respectively) were examined. C57BL/6N male mice were used for embryo production at 13-23 and 50-55 weeks of age. Two-cell stage embryos were collected from the oviducts of superovulated female mice (8-15 weeks old) and cultured for 24 h until the 8-cell stage, followed by embryo vitrification. Fresh and vitrified-warmed embryos were incubated for 2 days until the blastocyst stage, and mt-cn and TL were investigated. The cell-free mitochondrial DNA copy number (cf-mt-cn) in the spent culture medium (SCM) of the embryos was then investigated. RNA sequencing of blastocysts revealed that metabolic pathways, including oxidative phosphorylation and mTOR pathways, were enriched in differentially expressed genes. The mt-cn and TL of AF-derived blastocysts were lower and shorter, respectively, than those of YF-derived blastocysts. Paternal aging did not affect the blastocyst rate after vitrification. Vitrification of the 8-cell stage embryos did not affect the mt-cn of the blastocysts. However, it increased the cf-mt-cn (cell-free mt-cn) in the SCM of both YF- and AF-derived embryos. Vitrification did not affect the TL of either YF- or AF-derived embryos. Thus, paternal aging affected the mt-cn and TL of the embryos, but vitrification did not affect these parameters in either age groups.

Pros and Cons of Cryopreserving Allogeneic Stem Cell Products

The COVID-19 pandemic has precipitously changed the practice of transplanting fresh allografts. The safety measures adopted during the pandemic prompted the near-universal graft cryopreservation. However, the influence of cryopreserving allogeneic grafts on long-term transplant outcomes has emerged only in the most recent literature. In this review, the basic principles of cell cryopreservation are revised and the effects of cryopreservation on the different graft components are carefully reexamined. Finally, a literature revision on studies comparing transplant outcomes in patients receiving cryopreserved and fresh grafts is illustrated.

Enhancing Viability of Human Embryonic Stem Cells during Cryopreservation via RGD-REP-Mediated Activation of FAK/AKT/FoxO3a Signaling Pathway

BACKGROUND

Cryopreservation is a crucial method for long-term storage and stable allocation of human pluripotent stem cells (hPSCs), which are increasingly being used in various applications. However, preserving hPSCs in cryogenic conditions is challenging due to reduced recovery rates.

METHODS

To address this issue, the Arginine-Glycine-Aspartate (RGD) motif was incorporated into a recombinant elastin-like peptide (REP). Human embryonic stem cells (hESCs) were treated with REP containing RGD motif (RGD-REP) during suspension and cryopreservation, and the survival rate was analyzed. The underlying mechanisms were also investigated.

RESULTS

The addition of RGD-REP to the cryopreservation solution improved cell survival and pluripotency marker expression. The improvement was confirmed to be due to the activation of the FAK-AKT cascade by RGD-REP binding to hESC surface interin protein, and consequent inhibition of FoxO3a. The inactivation of FoxO3a reduced the expression of apoptosis-related genes, such as BIM, leading to increased survival of PSCs in a suspension state.

CONCLUSION

RGD-REP, as a ligand for integrin protein, improves the survival and maintenance of hPSCs during cryopreservation by activating survival signals via the RGD motif. These results have potential implications for improving the efficiency of stem cell usage in both research and therapeutic applications.

Investigation of the Mitigation of DMSO-Induced Cytotoxicity by Hyaluronic Acid following Cryopreservation of Human Nucleus Pulposus Cells

To develop an off-the-shelf therapeutic product for intervertebral disc (IVD) repair using nucleus pulposus cells (NPCs), it is beneficial to mitigate dimethyl sulfoxide (DMSO)-induced cytotoxicity caused by intracellular reactive oxygen species (ROS). Hyaluronic acid (HA) has been shown to protect chondrocytes against ROS. Therefore, we examined the potential of HA on mitigating DMSO-induced cytotoxicity for the enhancement of NPC therapy. Human NPC cryopreserved in DMSO solutions were thawed, mixed with equal amounts of EDTA-PBS (Group E) or HA (Group H), and incubated for 3-5 h. After incubation, DMSO was removed, and the cells were cultured for 5 days. Thereafter, we examined cell viability, cell proliferation rates, Tie2 positivity (a marker of NP progenitor cells), and the estimated numbers of Tie2 positive cells. Fluorescence intensity of DHE and MitoSOX staining, as indicators for oxidative stress, were evaluated by flow cytometry. Group H showed higher rates of cell proliferation and Tie2 expressing cells with a trend toward suppression of oxidative stress compared to Group E. Thus, HA treatment appears to suppress ROS induced by DMSO. These results highlight the ability of HA to maintain NPC functionalities, suggesting that mixing HA at the time of transplantation may be useful in the development of off-the-shelf NPC products.

N-acetylcysteine attenuates oxidative stress-mediated cell viability loss induced by dimethyl sulfoxide in cryopreservation of human nucleus pulposus cells: A potential solution for mass production

Background

Cell therapy is considered a promising strategy for intervertebral disc (IVD) regeneration. However, cell products often require long-term cryopreservation, which compromises cell viability and potency, thus potentially hindering commercialization and off-the-shelf availability. Dimethyl sulfoxide (DMSO) is a commonly used cryoprotectant, however, DMSO is associated with cytotoxicity and cell viability loss. This study aimed to investigate the effects of DMSO on human nucleus pulposus cells (NPC) and the role of oxidative stress in DMSO-induced cytotoxicity. Furthermore, we examined the potential of antioxidant N-acetylcysteine (NAC) supplementation to mitigate the negative effects of DMSO.

Methods

NPC were exposed to various concentrations of DMSO with or without a freezing cycle. Cell viability, cell apoptosis and necrosis rates, intracellular reactive oxygen species (ROS) levels, and gene expression of major antioxidant enzymes were evaluated. In addition, NAC was added to cryopreservation medium containing 10% DMSO and its effects on ROS levels and cell viability were assessed.

Results

DMSO concentrations ≤1% for 24 h did not significantly affect the NPC viability, whereas exposure to 5 and 10% DMSO (most commonly used concentration) caused cell viability loss (loss of 57% and 68% respectively after 24 h) and cell death in a dose- and time-dependent manner. DMSO increased intracellular and mitochondrial ROS (1.9-fold and 3.6-fold respectively after 12 h exposure to 10% DMSO) and downregulated gene expression levels of antioxidant enzymes in a dose-dependent manner. Tempering ROS through NAC treatment significantly attenuated DMSO-induced oxidative stress and supported maintenance of cell viability.

Conclusions

This study demonstrated dose- and time-dependent cytotoxic effects of DMSO on human NPC. The addition of NAC to the cryopreservation medium ameliorated cell viability loss by reducing DMSO-induced oxidative stress in the freeze-thawing cycle. These findings may be useful for future clinical applications of whole cells and cellular products.

A pre‑clinical model combining cryopreservation technique with precision‑cut slice culture method to assess the in vitro drug response of hepatocellular carcinoma

Models considering hepatocellular carcinoma (HCC) complexity cannot be accurately replicated in routine cell lines or animal models. We aimed to evaluate the practicality of tissue slice culture by combining it with a cryopreservation technique. We prepared 0.3-mm-thick tissue slices by a microtome and maintained their cell viability using a cryopreservation technique. Slices were cultured individually in the presence or absence of regorafenib (REG) for 72 h. Alterations in morphology and gene expression were assessed by histological and genetic analysis. Overall viability was also analyzed in tissue slices by CCK-8 quantification assay and fluorescent staining. Tissue morphology and cell viability were evaluated to quantify drug effects. Histological and genetic analyses showed that no significant alterations in morphology and gene expression were induced by the vitrification-based cryopreservation method. The viability of warmed HCC tissues was up to 90% of the fresh tissues. The viability and proliferation could be retained for at least four days in the filter culture system. The positive drug responses in precision-cut slice culture in vitro were evaluated by tissue morphology and cell viability. In summary, the successful application of precision-cut HCC slice culture combined with a cryopreservation technique in a systematic drug screening demonstrates the feasibility and utility of slice culture method for assessing drug response.

Assessment of the Impact of Post-Thaw Stress Pathway Modulation on Cell Recovery following Cryopreservation in a Hematopoietic Progenitor Cell Model

The development and use of complex cell-based products in clinical and discovery science continues to grow at an unprecedented pace. To this end, cryopreservation plays a critical role, serving as an enabling process, providing on-demand access to biological material, facilitating large scale production, storage, and distribution of living materials. Despite serving a critical role and substantial improvements over the last several decades, cryopreservation often remains a bottleneck impacting numerous areas including cell therapy, tissue engineering, and tissue banking. Studies have illustrated the impact and benefit of controlling cryopreservation-induced delayed-onset cell death (CIDOCD) through various “front end” strategies, such as specialized media, new cryoprotective agents, and molecular control during cryopreservation. While proving highly successful, a substantial level of cell death and loss of cell function remains associated with cryopreservation. Recently, we focused on developing technologies (RevitalICE™) designed to reduce the impact of CIDOCD through buffering the cell stress response during the post-thaw recovery phase in an effort to improve the recovery of previously cryopreserved samples. In this study, we investigated the impact of modulating apoptotic caspase activation, oxidative stress, unfolded protein response, and free radical damage in the initial 24 h post-thaw on overall cell survival. Human hematopoietic progenitor cells in vitro cryopreserved in both traditional extracellular-type and intracellular-type cryopreservation freeze media were utilized as a model cell system to assess impact on survival. Our findings demonstrated that through the modulation of several of these pathways, improvements in cell recovery were obtained, regardless of the freeze media and dimethyl sulfoxide concentration utilized. Specifically, through the use of oxidative stress inhibitors, an average increase of 20% in overall viability was observed. Furthermore, the results demonstrated that by using the post-thaw recovery reagent on samples cryopreserved in intracellular-type media (Unisol™), improvements in overall cell survival approaching 80% of non-frozen controls were attained. While improvements in overall survival were obtained, an assessment on the impact of specific cell subpopulations and functionality remains to be completed. While work remains, these results represent an important step forward in the development of improved cryopreservation processes for use in discovery science, and commercial and clinical settings.

Nonfreezing Low Temperature Maintains the Viability of Menstrual Blood-Derived Endometrial Stem Cells Under Oxygen-Glucose Deprivation Through the Sustained Release of Autophagy-Produced Energy

Between the completion of the mesenchymal stem cell (MSCs) preparation and the transplantation into the patient, there is a time interval during which the quality control and transport of MSC products occur, which usually involves suspending the cells in normal saline in an oxygen-glucose deprivation (OGD) microenvironments. Thus, how to effectively maintain MSC viability during the abovementioned time interval is bound to play a significant role in the therapeutic effect of MSC-based therapies. Recently, menstrual blood-derived endometrial stem cells (MenSCs) have attracted extensive attention in regenerative medicine due to their superior biological characteristics, including noninvasive protocols for their collection, abundant source material, stable donation, and autotransplantation. Therefore, this study aimed to mainly determine the effect of storage temperature on the maintenance of MenSC viabilities in an OGD microenvironment, and to preliminarily explore its potential mechanism. Simultaneously, the effects of solvents commonly used in the clinic on MenSC viability were also examined to support the clinical application of MenSCs. Consequently, our results demonstrated that in the OGD microenvironment, a nonfreezing low temperature (4°C) was suitable and cost-effective for MenSC storage, and the maintenance of MenSC viability stored at 4°C was partly contributed by the sustained releases of autophagy-produced energy. Furthermore, the addition of human serum albumin effectively inhibited the cell sedimentations in the MenSC suspension. These results provide support and practical experience for the extensive application of MenSCs in the clinic.

A Tool for Accurate Stoichiometric Composition of Cryopreservative Media for Fetal and Induced Pluripotent Stem Cell-Derived Human Neural Stem Cells

Fetal human neural stem cells (fhNSC) are of considerable interest as potential regenerative therapies for neuronal or glial degeneration or destruction resulting from genetic abnormalities, disease, or injury. Realization of this potential requires securing a supply of cells sufficient to meet the needs of transplantation, which are often tens to hundreds of millions of cells per dose. This challenge necessitates the establishment of safe and efficient cell banking protocols. Cryopreservation, involving the slow freezing or vitrification of cells, enables storage of fhNSC for prolonged periods, while maintaining their viability and multipotency required for clinical use. To optimize cryopreservation of fhNSC, attention has become focused on the composition of the medium used to effect cryopreservation by slow freezing/vitrification-i.e., the cryopreservative medium. The cryopreservative medium is typically specified as a dilution of a concentrated cryoprotectant, such as dimethylsulfoxide or glycerol, in cell culture medium that is often combined with serum or another source of necessary growth factors. The present work is devoted to a computational tool for determining the composition of a cryopreservative medium that can be combined with dissociated fhNSC resuspended in a certain volume of culture medium to achieve the criterion of stoichiometric dilution of cryoprotectant favorable to cell viability in the final mixture of cryopreservative medium and cells. © 2021 Wiley Periodicals LLC. Basic Protocol: Culture and passage of fhNSC, counting of enzymatically dissociated fhNSC, and quantitative formulation of cryomedium Alternate Protocol: Procedure when cell medium is not added to the cryomedium.

Isolation of intact extracellular vesicles from cryopreserved samples

Extracellular vesicles (EVs) have emerged as promising candidates in biomarker discovery and diagnostics. Protected by the lipid bilayer, the molecular content of EVs in diverse biofluids are protected from RNases and proteases in the surrounding environment that may rapidly degrade targets of interests. Nonetheless, cryopreservation of EV-containing samples to -80°C may expose the lipid bilayer to physical and biological stressors which may result in cryoinjury and contribute to changes in EV yield, function, or molecular cargo. In the present work, we systematically evaluate the effect of cryopreservation at -80°C for a relatively short duration of storage (up to 12 days) on plasma- and media-derived EV particle count and/or RNA yield/quality, as compared to paired fresh controls. On average, we found that the plasma-derived EV concentration of stored samples decreased to 23% of fresh samples. Further, this significant decrease in EV particle count was matched with a corresponding significant decrease in RNA yield whereby plasma-derived stored samples contained only 47-52% of the total RNA from fresh samples, depending on the extraction method used. Similarly, media-derived EVs showed a statistically significant decrease in RNA yield whereby stored samples were 58% of the total RNA from fresh samples. In contrast, we did not obtain clear evidence of decreased RNA quality through analysis of RNA traces. These results suggest that samples stored for up to 12 days can indeed produce high-quality RNA; however, we note that when directly comparing fresh versus cryopreserved samples without cryoprotective agents there are significant losses in total RNA. Finally, we demonstrate that the addition of the commonly used cryoprotectant agent, DMSO, alongside greater control of the rate of cooling/warming, can rescue EVs from damaging ice formation and improve RNA yield.

Changes in telomere length and senescence markers during human ovarian tissue cryopreservation

Ovarian tissue cryopreservation is considered as a useful option to preserve fertility for cancer patients. This study purposed to evaluate the change of telomere length and senescence markers during human ovarian tissue cryopreservation. Ovarian tissues were obtained from women who underwent benign ovarian surgery in the gynecology research unit of a university hospital with prior consent and IRB approval. DNA was extracted from the ovarian tissues using a DNeasy tissue kit and telomere lengths in the DNA samples were determined by real time PCR before and after cryopreservation. All tissues were stained with hematoxylin–eosin and subjected to immunohistochemistry and TUNEL assays. Other senescence markers, including p53, p16, p21, and phospho-pRb proteins, were evaluated using western blot analysis. Ovarian tissues were collected from ten patients and prepared for slow freezing with the same size of diameter 4 mm and 1 mm thickness. Mean age of patients was 26.7 ± 6.2 years (range, 16–34 years), and ovarian tissues were cryopreserved and thawed 4 weeks after cryopreservation. The mean telomere length was significantly decreased after cryopreservation (9.57 ± 1.47 bp vs. 8.34 ± 1.83 bp, p = 0.001). Western blot analysis revealed that p53, p16, and p21 proteins increased and phospho-pRb protein expression decreased after ovarian tissue cryopreservation. Ovarian tissue cryopreservation and transplantation is regarded as one of promising options for fertility preservation. However, clinicians and researchers should be aware of possible irreversible DNA changes such as shortening of telomere length and alterations of other senescence markers in human ovarian tissues.

Natural Compounds as a Strategy to Optimize "In Vitro" Expansion of Stem Cells

The efficient use of stem cells for transplantation is often limited by the relatively low number of stem cells collected. The ex vivo expansion of human stem cells for clinical use is a potentially valuable approach to increase stem cell number. Currently, most of the procedures used to expand stem cells are carried out using a 21% oxygen concentration, which is about 4- to 10-fold greater than the concentration characteristic of their natural niches. Hyperoxia might cause oxidative stress with a deleterious effect on the physiology of cultured stem cells. In this review, we investigate and critically examine the available information on the ability of natural compounds to counteract hyperoxia-induced damage in different types of stem cells ex vivo. In particular, we focused on proliferation and stemness maintenance in an attempt to draw up useful indications to define new culture media with a promoting activity on cell expansion in vitro.

Cryopreservation and thawing of hematopoietic stem cell CD34-induced apoptosis through caspase pathway activation: Key role of granulocytes

INTRODUCTION

Cell damage inescapably occurs during both the freezing and the thawing graft processes for autologous hematopoietic stem cell (HSC) transplantation. To estimate HSC injury, a quality control is performed including: (i) CD34⁺ quantification; (ii) percentage of CD34⁺ viability and (iii) evaluation of HSC functional ability to form colony forming unit-granulocyte macrophage (CFU-GM). Apoptosis involves complex pathways such as caspase enzymes. Here, we assess the extent of apoptosis that is caspase-dependent before and after cryoconservation of CD34⁺, using a Fluorescent Labeled Inhibitor of CAspases (FLICA).

METHODS

Caspase pathway activation status was evaluated in 46 patients (multiple myeloma [n = 24], lymphoma [n = 22]), by flow cytometry, using a 7-aminoactinomycin-D (7AAD)/FLICA staining test, in CD34⁺, CD3⁺, CD14⁺ and CD56⁺ cells. Viable 7AAD^-/FLICA⁺ cells were then correlated with various parameters.

RESULTS

We showed a significant caspase pathway activation, with 23% CD34⁺/7AAD^-/FLICA⁺ cells after thawing, compared with the 2% described in fresh CD34⁺ cells (P < 0.0001). Moreover, caspase pathway was significantly activated in thawing CD3⁺, CD56⁺ and CD14⁺ cells. We also report a significant correlation between the rate of CD34⁺/7AAD^-/FLICA⁺ cells and post-thawing granulocytes count (P = 0.042) and their potential to be differentiated into CFU-GM (P = 0.004).

DISCUSSION

Our results show substantial cell death, induced by the increase of caspase pathway activation, secondary to the thawing process, and across all study cell types. This observation may affect the immune response quality during recipient aplasia, without detecting a clinical impact. Moreover, caspase pathway activation through CD3⁺ and CD56⁺ subpopulations could modify the therapeutic result of donor lymphocytes infusion (DLI).

Icariin Improves the Viability and Function of Cryopreserved Human Nucleus Pulposus-Derived Mesenchymal Stem Cells

Nucleus pulposus-derived mesenchymal stem cells (NPMSCs) have shown a good prospect in the regeneration of intervertebral disc (IVD) tissues. However, fresh NPMSCs are not always readily available for basic research and clinical applications. Therefore, there is a need for an effective long-term cryopreservation method for NPMSCs. The aim of this study was to determine whether adding icariin (ICA) to the conventional cryoprotectant containing dimethyl sulfoxide (DMSO) had a better cryoprotective effect for NPMSCs. The results showed that the freezing solution containing ICA along with DMSO significantly increased the postthawed cell viability, decreased the apoptosis rate, improved cell adherence, and maintained the mitochondrial functions, as compared to the freezing solution containing DMSO alone. And the inhibition of oxidative stress and upregulation of heat shock proteins (HSPs) in the presence of ICA also confirmed the beneficial effect of ICA. Furthermore, ICA had no cytotoxicity and did not alter the characteristics of postthawed NPMSCs. In conclusion, these results suggested that the addition of ICA to the conventional freezing medium could improve the viability and function of the cryopreserved human NPMSCs and provided an optimal formulated freezing solution for human NPMSC cryopreservation.

Stem cells and beta cell replacement therapy: a prospective health technology assessment study

BACKGROUND

Although current beta cell replacement therapy is effective in stabilizing glycemic control in highly selected patients with refractory type 1 diabetes, many hurdles are inherent to this and other donor-based transplantation methods. One solution could be moving to stem cell-derived transplant tissue. This study investigates a novel stem cell-derived graft and implant technology and explores the circumstances of its cost-effectiveness compared to intensive insulin therapy.

METHODS

We used a manufacturing optimization model based on work by Simaria et al. to model cost of the stem cell-based transplant doses and integrated its results into a cost-effectiveness model of diabetes treatments. The disease model simulated marginal differences in clinical effects and costs between the new technology and our comparator intensive insulin therapy. The form of beta cell replacement therapy was as a series of retrievable subcutaneous implant devices which protect the enclosed pancreatic progenitors cells from the immune system. This approach was presumed to be as effective as state of the art islet transplantation, aside from immunosuppression drawbacks. We investigated two different cell culture methods and several production and delivery scenarios.

RESULTS

We found the likely range of treatment costs for this form of graft tissue for beta cell replacement therapy. Additionally our results show this technology could be cost-effective compared to intensive insulin therapy, at a willingness-to-pay threshold of $100,000 per quality-adjusted life year. However, results also indicate that mass production has by far the best chance of providing affordable graft tissue, while overall there seems to be considerable room for cost reductions.

CONCLUSIONS

Such a technology can improve treatment access and quality of life for patients through increased graft supply and protection. Stem cell-based implants can be a feasible way of treating a wide range of patients with type 1 diabetes.

Maintaining viability and characteristics of cholangiocarcinoma tissue by vitrification-based cryopreservation

Tumor tissue has great clinical and scientific value which relies highly on the proper preservation of primary materials. Conventional tumor tissue cryopreservation using slow-freezing method has yielded limited success, leading to significant cell loss and morphological damage. Here we report a standardized vitrification-based cryopreservation method, by which we have successfully vitrified and warmed 35 intrahepatic cholangiocarcinoma (ICC) tissues with up to 80% viability of the fresh tumor tissues. Cryopreserved ICC tissue could generate patient-derived xenografts (PDXs) with take rates of 68.2% compared to 72.7% using fresh tumor tissues. Histological and genetic analyses showed that no significant alterations in morphology and gene expression were introduced by this cryopreservation method. Our procedure may facilitate collection, long-time storage and propagation of cholangiocarcinoma or other tumor specimens for (pre)clinical studies of novel therapies or for basic research.