A bioinspired and chemically defined alternative to dimethyl sulfoxide for the cryopreservation of human hematopoietic stem cells

Impact of controlled ice nucleation on intracellular dehydration, ice formation and their implications on T cell freeze-thaw viability

Cryopreservation is important in manufacturing of cell therapy products, influencing their safety and effectiveness. During freezing and thawing, intracellular events such as dehydration and ice formation can impact cell viability. In this study, the impact of controlling the ice nucleation temperature on intracellular events and viability were investigated. A model T cell line, Jurkat cells, were evaluated in commercially relevant cryoformulations (2.5 and 5 % v/v DMSO in Plasma-Lyte A) using a cryomicroscopic setup to monitor the dynamic changes cells go through during freeze-thaw as well as a controlled rate freezer to study bulk freeze-thaw. The equilibrium freezing temperatures of the studied formulations and a DMSO/Plasma-Lyte A liquidus curve were determined using DSC. The cryomicroscopic studies revealed that an ice nucleation temperature of -6°C, close to the equilibrium freezing temperatures of cryoformulations, led to more intracellular dehydration and less intracellular ice formation during freezing compared to either a lower ice nucleation temperature (-10 °C) or uncontrolled ice nucleation. The cell membrane integrity and post thaw viability in bulk cryopreservation consistently demonstrated the advantage of the higher ice nucleation temperature, and the correlation between the cellular events and cell viability.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Elevated fucose content enhances the cryoprotective performance of anionic polysaccharides

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

"Drying effect" of fructus aurantii components and the mechanism of action based on network pharmacology and in vitro pharmacodynamic validation

Background: Fructus aurantii (FA) is the dried, unripe fruit of the plant Citrus aurantium L. and its cultivated varieties. We investigated the drying effect of FA components and how this drying affect is achieved. Methods: We employed systems pharmacology to predict the components and targets of FA that produce its drying effect. These predictions were verified by computer simulation and animal experiments. In the latter, we measured the bodyweight, water consumption, urine output, fecal water content, rate of salivary secretion, and cross-sectional area of the long axis of the submandibular gland of mice. Immunohistochemistry was used to measure expression of aquaporin (AQP)5 in the submandibular gland, AQP2 in the kidney, and AQP3 in the colon. ELISA kits were used to measure the horizontal variation of cyclic adenosine monsophosphate (cAMP), cyclic guanosine monophosphate (cGMP) and interferon-γ. Results: Sixty-seven potentially active components of FA were screened out. FA could produce a drying effect after regulating 214 targets through 66 active components. A total of 870 gene ontology (GO) terms and 153 signaling pathways were identified. The hypoxia inducible factor-1 signaling pathway, phosphoinositide 3-kinase-protein kinase B (PI3K-AKT) signaling pathway, calcium signaling pathway, and Ras signaling pathway may have important roles in the drying effect of FA. Four components of FA were identified: sinensetin, tangeretin, 5-demethylnobiletin and chrysin. These four components could increase the serum level of interferon-γ and ratio of cyclic adenosine monophosphate:cyclic guanosine monophosphate in mice, and affect their water consumption, urine output, fecal water content and rate of salivary secretion. Conclusion: Four components of FA (tangeretin, sinensetin, chrysin, 5-Demethylmobiletin) were closely related to the Janus kinase-signal transducer and activator of transcription-3 (JAK-STAT3), PI3K-AKT, and the other signaling pathways. They can regulate the protein expression of JAK2, STAT3, PI3K, lymphocyte cell-specific protein-tyrosine kinase, vascular endothelial growth factor A, and protein kinase B1, affect water metabolism in the body and, finally, result in a drying effect.

Natural Cryoprotective and Cytoprotective Agents in Cryopreservation: A Focus on Melatonin

Cryoprotective and cytoprotective agents (Cytoprotective Agents) are fundamental components of the cryopreservation process. This review presents the essentials of the cryopreservation process by examining its drawbacks and the role of cytoprotective agents in protecting cell physiology. Natural cryoprotective and cytoprotective agents, such as antifreeze proteins, sugars and natural deep eutectic systems, have been compared with synthetic ones, addressing their mechanisms of action and efficacy of protection. The final part of this article focuses melatonin, a hormonal substance with antioxidant properties, and its emerging role as a cytoprotective agent for somatic cells and gametes, including ovarian tissue, spermatozoa and spermatogonial stem cells.

Cryopreservation of undifferentiated and differentiated human neuronal cells

The effective use of human-derived cells that are difficult to freeze, such as parenchymal cells and differentiated cells from stem cells, is crucial. A stable supply of damage-sensitive cells, such as differentiated neuronal cells, neurons, and glial cells can contribute considerably to cell therapy. We developed a serum-free freezing solution that is effective for the cryopreservation of differentiated neuronal cells. The quality of the differentiated and undifferentiated SK-N-SH cells was determined based on cell viability, live-cell recovery rate, and morphology of cultured cells, to assess the efficacy of the freezing solutions. The viability and recovery rate of the differentiated SK-N-SH neuronal cells were reduced by approximately 1.5-folds compared to that of the undifferentiated SK-N-SH cells. The viability and recovery rate of the differentiated SK-N-SH cells were remarkably different between the freezing solutions containing 10% DMSO and that containing 10% glycerol. Cryoprotectants such as fetal bovine serum (FBS), antifreeze proteins (sericin), and sugars (maltose), are essential for protecting against freeze damage in differentiated neuronal cells and parenchymal cells. Serum-free alternatives (sericin and maltose) could increase safety during cell transplantation and regenerative medicine. Considering these, we propose an effective freezing solution for the cryopreservation of neuronal cells.

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The timing of freezing during cell differentiation.

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More effective serum-free freezing solution for differentiated neuronal cells.

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Improving the quality of damage-sensitive cells, such as differentiated neuronal cells.

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.

Reduced dimethyl sulfoxide concentrations successfully cryopreserve human hematopoietic stem cells with multi-lineage long-term engraftment ability in mice

BACKGROUND AIMS

The cryopreservation of hematopoietic stem cells (HSCs) in dimethyl sulfoxide (DMSO) is used widely, but DMSO toxicity in transplant patients and the effects of DMSO on the normal function of cryopreserved cells are concerns. To address these issues, in vitro and clinical studies have explored using reduced concentrations of DMSO for cryopreservation. However, the effect of reducing DMSO concentration on the efficient cryopreservation of HSCs has not been directly measured.

METHODS

Cryopreservation of human bone marrow using 10%, 7.5% and 5% DMSO concentrations was examined. Cell counting, flow cytometry and colony assays were used to analyze different cell populations. The recovery of stem cells was enumerated using extreme limiting dilution analysis of long-term multi-lineage engraftment in immunodeficient mice. Four different methods of analyzing human engraftment were compared to ascertain stem cell engraftment: (i) engraftment of CD33⁺ myeloid, CD19⁺ B-lymphoid, CD235a⁺ erythroid and CD34⁺ progenitors; (ii) engraftment of the same four populations plus CD41⁺CD42b⁺ platelets; (iii) engraftment of CD34⁺⁺CD133⁺ cells; and (iv) engraftment of CD34⁺⁺CD38^- cells.

RESULTS

Hematopoietic colony-forming, CD34^++/+, CD34⁺⁺CD133⁺ and CD34⁺⁺CD38^- cells were as well preserved with 5% DMSO as they were with the higher concentrations tested. The estimates of stem cell frequencies made in the xenogeneic transplant model did not show any significant detrimental effect of using lower concentrations of DMSO. Comparison of the different methods of gauging stem cell engraftment in mice led to different estimates of stem cell numbers, but overall, all measures found that reduced concentrations of DMSO supported the cryopreservation of HSCs.

CONCLUSION

Cryopreservation of HSCs in DMSO concentrations as low as 5% is effective.