Characterizing the "sweet spot" for the preservation of a T-cell line using osmolytes

L-Proline as a Cryoprotective Agent for the Preservation of Galea Spixii Skin Fibroblasts

Somatic cell biobanking is a promising strategy for developing reproductive techniques. Although cryopreservation, a technique used for creating biobanks, has been performed on Galea spixii, structural and physiological damage to its cells highlight the need to optimize the cryoprotective solution being used. Therefore, the osmoprotective activity of 5 mM L-proline was evaluated as an alternative cryoprotectant for G. spixii fibroblast conservation. The concentration was defined based on previous studies conducted on mammalian cells. Cells derived from the skin of six individuals were cultured until the fifth passage were cryopreserved under the following treatments: (i) control (non-cryopreserved); (ii) a solution with 10% dimethyl sulfoxide (Me2SO), 10% fetal bovine serum (FBS), and 0.2 M sucrose; (iii) a solution with 10% Me2SO, 10% FBS, and 5 mM L-proline; and (iv) a solution with 10% Me2SO, 10% FBS, 0.2 M sucrose, and 5 mM L-proline. Tests were conducted to analyze cell morphology, viability, metabolism, proliferation, and apoptosis; reactive oxygen species (ROS) levels; and mitochondrial membrane activity (ΔΨm). A reduction in the number of viable cells (72.3% ± 1.2%) was observed in the sucrose-containing group compared to the control (86.7% ± 2.0%) and L-proline (88.4% ± 1.8% and 87.8% ± 2.1%) groups. After apoptotic analysis, a reduction in the number of viable cells was observed in the group with sucrose alone (74.6% ± 4.1%) compared to the control group (88.2% ± 1.1%). The ROS levels (1.03 ± 0.5 and 1.07 ± 0.5, respectively) and ΔΨm values (0.99 ± 0.42 and 1.22 ± 0.73, respectively) observed in the groups with L-proline were similar to that observed in the control group (1.00 ± 0.5 and 1.00 ± 0.4, respectively). Moreover, no difference was observed between groups for cell morphology, metabolism, or proliferation. Thus, L-proline is a cryoprotectant agent that can be used during G. spixii fibroblast cryopreservation, alone or with sucrose. In addition, we developed an adequate biobank for G. spixii, whereby stored cells could be used for reproductive techniques.

Adoptive NK Cell Therapy - a Beacon of Hope in Multiple Myeloma Treatment

Major advances in the treatment of multiple myeloma (MM) have been achieved by effective new agents such as proteasome inhibitors, immunomodulatory drugs, or monoclonal antibodies. Despite significant progress, MM remains still incurable and, recently, cellular immunotherapy has emerged as a promising treatment for relapsed/refractory MM. The emergence of chimeric antigen receptor (CAR) technology has transformed immunotherapy by enhancing the antitumor functions of T cells and natural killer (NK) cells, leading to effective control of hematologic malignancies. Recent advancements in gene delivery to NK cells have paved the way for the clinical application of CAR-NK cell therapy. CAR-NK cell therapy strategies have demonstrated safety, tolerability, and substantial efficacy in treating B cell malignancies in various clinical settings. However, their effectiveness in eliminating MM remains to be established. This review explores multiple approaches to enhance NK cell cytotoxicity, persistence, expansion, and manufacturing processes, and highlights the challenges and opportunities associated with CAR-NK cell therapy against MM. By shedding light on these aspects, this review aims to provide valuable insights into the potential of CAR-NK cell therapy as a promising approach for improving the treatment outcomes of MM patients.

A study on the relationship between the crystallization characteristics of quenched droplets and the effect of cell cryopreservation with Raman spectroscopy

The cryopreservation method of microdroplets has steadily become widely employed in the cryopreservation of microscale biological samples such as various types of cells due to its fast cooling rate, significant reduction of the concentration of cryoprotectants, and practical liquid handling method. However, it is still necessary to consider the corresponding relationship between droplet size and concentration and the impact of crystallization during the cooling process on cell viability. The key may be a misunderstanding of the influencing factors of crystallization and vitrification behavior with concentration during cooling on the ultimate cell viability, which may be attributable to the inability to analyze the freezing state inside the microdroplets. Therefore, in this work, an in situ Raman observation system for droplet quenching was assembled to obtain Raman spectra in the frozen state, and the spectral characteristics of the crystallization and vitrification processes of microdroplets with varied concentrations and volumes were investigated. Furthermore, the degree of crystallization inside the droplets was quantitatively analyzed, and it was found that the ratio of the crystalline peak to hydrogen bond shoulder could clearly distinguish the degree of crystallization and the vitrified state, and the Raman crystallization characteristic parameters gradually increased with the decrease of concentrations. By obtaining the cooling curve and the overall cooling rate of quenching droplets, the vitrification state of the microdroplets was confirmed by theoretical analysis of the cooling characteristics of a DMSO solution system. In addition, the effect of cell cryopreservation was investigated using the microdroplet quenching device, and it was found that the key to cell survival during the quenching process of low-concentration microdroplets was dominated by the cooling rate and the internal crystallization degree, while the main influencing factor on high concentration was the toxic effect of a protective agent. In general, this work introduces a new nondestructive evaluation and analysis method for the cryopreservation of quenching microdroplets.

Cryoprotective Mechanism of DMSO Induced by the Inhibitory Effect on Eutectic NaCl Crystallization

Cryopreservation is a critical procedure in autologous hematopoietic stem cell transplantation. Dimethyl sulfoxide (DMSO) is the cryoprotectant of choice. Optimization of the cryopreservation protocol in the past revealed a dramatic loss of cell viability associated with a reduction of the DMSO concentration below 2 vol % in the freezing medium. The cryoprotective mechanism of DMSO is usually ascribed to the ability to suppress ice formation and reduce the adverse effects of the freeze-concentrated solution. This work proposes an alternative hypothesis considering the detrimental impact of NaCl eutectic crystallization on cell viability. Thermoanalytical and microstructural analysis of the DMSO effect on eutectic phase transformation of cryoprotective mixtures revealed a correlation between the loss of cell viability and eutectic NaCl crystallization. DMSO inhibits the eutectic crystallization of NaCl and preserves cell viability. Thermodynamic description of the inhibitory action and possible mechanism of cryoinjury are provided.

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.

Current challenges in the manufacture of clinical-grade autologous whole cell vaccines for hematological malignancies

Autologous whole cell vaccines use a patient's own tumor cells as a source of antigen to elicit an anti-tumor immune response in vivo. Recently, the authors conducted a systematic review of clinical trials employing these products in hematological cancers that showed a favorable safety profile and trend toward efficacy. However, it was noted that manufacturing challenges limit both the efficacy and clinical implementation of these vaccine products. In the current literature review, the authors sought to define the issues surrounding the manufacture of autologous whole cell products for hematological cancers. The authors describe key factors, including the acquisition, culture, cryopreservation and transduction of malignant cells, that require optimization for further advancement of the field. Furthermore, the authors provide a summary of pre-clinical work that informs how the identified challenges may be overcome. The authors also highlight areas in which future basic research would be of benefit to the field. The goal of this review is to provide a roadmap for investigators seeking to advance the field of autologous cell vaccines as it applies to hematological malignancies.

Cryopreservation of NK and T Cells Without DMSO for Adoptive Cell-Based Immunotherapy

Dimethylsufoxide (DMSO) being universally used as a cryoprotectant in clinical adoptive cell-therapy settings to treat hematological malignancies and solid tumors is a growing concern, largely due to its broad toxicities. Its use has been associated with significant clinical side effects-cardiovascular, neurological, gastrointestinal, and allergic-in patients receiving infusions of cell-therapy products. DMSO has also been associated with altered expression of natural killer (NK) and T-cell markers and their in vivo function, not to mention difficulties in scaling up DMSO-based cryoprotectants, which introduce manufacturing challenges for autologous and allogeneic cellular therapies, including chimeric antigen receptor (CAR)-T and CAR-NK cell therapies. Interest in developing alternatives to DMSO has resulted in the evaluation of a variety of sugars, proteins, polymers, amino acids, and other small molecules and osmolytes as well as modalities to efficiently enable cellular uptake of these cryoprotectants. However, the DMSO-free cryopreservation of NK and T cells remains difficult. They represent heterogeneous cell populations that are sensitive to freezing and thawing. As a result, clinical use of cryopreserved cell-therapy products has not moved past the use of DMSO. Here, we present the state of the art in the development and use of cryopreservation options that do not contain DMSO toward clinical solutions to enable the global deployment of safer adoptively transferred cell-based therapies.

Formulation Considerations for Autologous T Cell Drug Products

Genetically modified autologous T cells have become an established immunotherapy in the fight against cancer. The manufacture of chimeric antigen receptor (CAR) and αβ-T cell receptor (TCR) transduced T cells poses unique challenges, including the formulation, cryopreservation and fill-finish steps, which are the focus of this review. With an increasing number of marketing approvals for CAR-T cell therapies, comparison of their formulation design and presentation for administration can be made. These differences will be discussed alongside the emergence of automated formulation and fill-finish processes, the formulation design space, Monte Carlo simulation applied to risk analysis, primary container selection, freezing profiles and thaw and the use of dimethyl sulfoxide and alternative solvents/excipients as cryopreservation agents. The review will conclude with a discussion of the pharmaceutical solutions required to meet the simplification of manufacture and flexibility in dosage form for clinical treatment.

Natural deep eutectic systems for nature-inspired cryopreservation of cells

Natural deep eutectic systems (NADES) are emerging as potential cryoprotective agents (CPA) for cell preservation. In this investigation, we develop an optimized CPA formulation using trehalose-glycerol NADES (T:G) diluted in Normosol-R and supplemented with isoleucine. Differential scanning calorimetry (DSC) is used to define the thermophysical properties of NADES-based solutions, and Raman spectroscopy is used to characterize the effect of NADES on ice formation and hydrogen bonding. Jurkat cells are cryopreserved in each solution, and post-thaw cell recovery, apoptosis, and growth are quantified. Raman spectra and heat maps show that NADES suppresses both ice formation and dehydration of the nonfrozen region. Supplementing NADES with isoleucine does not affect the solution's thermophysical properties but significantly improves the cells' survival and proliferation post-thaw. The study indicates that thermophysical properties of CPA solutions alone cannot predict optimal cell survival, suggesting that stabilization of biological structures by CPAs may play a role in successful cryopreservation.

Differential Evolution for the Optimization of DMSO-Free Cryoprotectants: Influence of Control Parameters

This study presents the influence of control parameters including population (NP) size, mutation factor (F), crossover (Cr), and four types of differential evolution (DE) algorithms including random, best, local-to-best, and local-to-best with self-adaptive (SA) modification for the purpose of optimizing the compositions of dimethylsufloxide (DMSO)-free cryoprotectants. Post-thaw recovery of Jurkat cells cryopreserved with two DMSO-free cryoprotectants at a cooling rate of 1 °C/min displayed a nonlinear, four-dimensional structure with multiple saddle nodes, which was a suitable training model to tune the control parameters and select the most appropriate type of differential evolution algorithm. Self-adaptive modification presented better performance in terms of optimization accuracy and sensitivity of mutation factor and crossover among the four different types of algorithms tested. Specifically, the classical type of differential evolution algorithm exhibited a wide acceptance to mutation factor and crossover. The optimization performance is more sensitive to mutation than crossover and the optimization accuracy is proportional to the population size. Increasing population size also reduces the sensitivity of the algorithm to the value of the mutation factor and crossover. The analysis of optimization accuracy and convergence speed suggests larger population size with F > 0.7 and Cr > 0.3 are well suited for use with cryopreservation optimization purposes. The tuned differential evolution algorithm is validated through finding global maximums of other two DMSO-free cryoprotectant formulation datasets. The results of these studies can be used to help more efficiently determine the optimal composition of multicomponent DMSO-free cryoprotectants in the future.

Dimethyl sulfoxide-free cryopreservation for cell therapy: A review

Cell-based therapeutics promise to transform the treatment of a wide range of diseases including cancer, genetic and degenerative disorders, or severe injuries. Many of the commercial and clinical development of cell therapy products require cryopreservation and storage of cellular starting materials, intermediates and/or final products at cryogenic temperature. Dimethyl sulfoxide (Me₂SO) has been the cryoprotectant of choice in most biobanking situations due to its exceptional performance in mitigating freezing-related damages. However, there is concern over the toxicity of Me₂SO and its potential side effects after administration to patients. Therefore, there has been growing demand for robust Me₂SO-free cryopreservation methods that can improve product safety and maintain potency and efficacy. This article provides an overview of the recent advances in Me₂SO-free cryopreservation of cells having therapeutic potentials and discusses a number of key challenges and opportunities to motivate the continued innovation of cryopreservation for cell therapy.

Understanding the freezing responses of T cells and other subsets of human peripheral blood mononuclear cells using DSMO-free cryoprotectants

BACKGROUND

This study examined the freezing responses of peripheral blood mononuclear cells (PBMCs) and specific white blood cell subsets contained therein when cryopreserved in three combinations of osmolytes composed of sugars, sugar alcohols and amino acids.

METHODS

A differential evolution algorithm with multiple objectives was used to optimize cryoprotectant composition and thus the post-thaw recoveries for both helper and cytotoxicity T cells simultaneously.

RESULTS

The screening of various formulations using a differential evolution algorithm showed post-thaw recoveries greater than 80% for the two subsets of T cells. The phenotypes and viabilities of PBMC subsets were characterized using flow cytometry. Significant differences between the post-thaw recovery for helper T cells and cytotoxic T cells were observed. Statistical models were used to analyze the importance of individual osmolytes and interactions between post-thaw recoveries of three subsets of T cell including helper T cells, cytotoxic T cells and natural killer T cells. The statistical model indicated that the preferred concentration levels of osmolytes and interaction modes were distinct between the three subsets studied. PBMCs were cultured for 72 h post-thaw to determine the stability of the cells. Because post-thaw apoptosis is a significant concern for lymphocytes, apoptosis of helper T cell and cytotoxic T cells frozen in a DMSO-free cryoprotectant was analyzed immediately post-thaw and 24 h post-thaw. Both cell types showed a decrease in cell viability 24 h post-thaw compared with immediately post-thaw. Helper T cell viability dropped 17%, and cytotoxic T cells had a 10% drop in viability. Immediately post-thaw, both cell types had >30% of cells in early apoptosis, but after 24 h the number of cells in early apoptosis decreased to below 20%.

CONCLUSION

This study helped us identify the freezing responses of different human PBMC subsets using combinations of osmolytes.

Cryopreservation of Human iPS Cell Aggregates in a DMSO-Free Solution-An Optimization and Comparative Study

Human induced pluripotent stem cells (hiPSCs) are an important cell source for regenerative medicine products. Effective methods of preservation are critical to their clinical and commercial applications. The use of a dimethyl sulfoxide (DMSO)-free solution containing all non-toxic molecules offers an effective alternative to the conventional DMSO and alleviates pain points associated with the use of DMSO in the cryopreservation of hiPSCs. Both hiPSCs and cells differentiated from them are commonly multicellular systems, which are more sensitive to stresses of freezing and thawing than single cells. In this investigation, low-temperature Raman spectroscopy visualized freezing behaviors of hiPSC aggregates in different solutions. These aggregates exhibited sensitivity to undercooling in DMSO-containing solutions. We demonstrated the ability to replace DMSO with non-toxic molecules, improve post-thaw cell survival, and reduce sensitivity to undercooling. An accelerated optimization process capitalized on the positive synergy among multiple DMSO-free molecules, which acted in concert to influence ice formation and protect cells during freezing and thawing. A differential evolution algorithm was used to optimize the multi-variable, DMSO-free preservation protocol in 8 experiments. hiPSC aggregates frozen in the optimized solution did not exhibit the same sensitivity to undercooling as those frozen in non-optimized solutions or DMSO, indicating superior adaptability of the optimized solution to different freezing modalities and unplanned deviations. This investigation shows the importance of optimization, explains the mechanisms and advantages of a DMSO-free solution, and enables not only improved cryopreservation of hiPSCs but potentially other cell types for translational regenerative medicine.

Preservation of cell-based immunotherapies for clinical trials

In the unique supply chain of cellular therapies, preservation is important to keep the cell product viable. Many factors in cryopreservation affect the outcome of a cell therapy: (i) formulation and introduction of a freezing medium, (ii) cooling rate, (iii) storage conditions, (iv) thawing conditions and (v) post-thaw processing. This article surveys clinical trials of cellular immunotherapy that used cryopreserved regulatory, chimeric antigen receptor or gamma delta T cells, dendritic cells or natural killer (NK) cells. Several observations are summarized from the given information. The aforementioned cell types have been similarly frozen in media containing 5-10% dimethyl sulfoxide (DMSO) with plasma, serum or human serum albumin. Two common freezing methods are an insulated freezing container such as Nalgene Mr. Frosty and a controlled-rate freezer at a cooling rate of -1°C/min. Water baths at approximately 37°C have been commonly used for thawing. Post-thaw processing of cryopreserved cells varied greatly: some studies infused the cells immediately upon thawing; some diluted the cells in a carrier solution of varying formulation before infusion; some washed cells to remove cryoprotective agents; and others re-cultured cells to recover cell viability or functionality lost due to cryopreservation. Emerging approaches to preserving cellular immunotherapies are also described. DMSO-free formulations of the freezing media have demonstrated improved preservation of cell viability in T lymphocytes and of cytotoxic function in natural killer cells. Saccharides are a common type of molecule used as an alternative cryoprotective agent to DMSO. Improving methods of preservation will be critical to growth in the clinical use of cellular immunotherapies.

The role of preservation in the variability of regenerative medicine products

Regenerative medicine (RM) has the potential to restore or establish normal function of cells, tissues and organs that have been lost due to age, disease or injury. It is common for the site of raw material collection, site of manufacture and site of clinical use to be different for RM products, and at the same time cells must remain viable and functional during transportation among different sites. Freezing products down to cryogenic temperatures along with cold chain transportation has become an effective method of preserving RM products. The quality of RM products along this supply chain represents the cumulative effects of all of the processing steps and all of the reagents used in the process. A variety of sources of variability in the preservation of RM products can result in both cell losses and greater variability in the quality of RM products. The purpose of this article is to review the sources of variability in the preservation process as well as the methods by which variability can be controlled or avoided.

Characterizing modes of action and interaction for multicomponent osmolyte solutions on Jurkat cells

This study examined the post-thaw recovery of Jurkat cells cryopreserved in three combinations of five osmolytes including trehalose, sucrose, glycerol, mannitol, and creatine. Cellular response was characterized using low-temperature Raman spectroscopy, and variation of post-thaw recovery was analyzed using statistical modeling. Combinations of osmolytes displayed distinct trends of post-thaw recovery, and a nonlinear relationship between compositions and post-thaw recovery was observed, suggesting interactions not only between different solutes but also between solutes and cells. The post-thaw recovery for optimized cryoprotectants in different combinations of osmolytes at a cooling rate of 1°C/min was comparable to that measured with 10% dimethyl sulfoxide. Statistical modeling was used to understand the importance of individual osmolytes as well as interactions between osmolytes on post-thaw recovery. Both higher concentrations of glycerol and certain interactions between sugars and glycerol were found to typically increase the post-thaw recovery. Raman images showed the influence of osmolytes and combinations of osmolytes on ice crystal shape, which reflected the interactions between osmolytes and water. Differences in the composition also influenced the presence or absence of intracellular ice formation, which could also be detected by Raman. These studies help us understand the modes of action for cryoprotective agents in these osmolyte solutions.

Characterizing the "sweet spot" for the preservation of a T-cell line using osmolytes

This study examined the post-thaw recovery of Jurkat cells cryopreserved in single osmolyte solutions containing sucrose, glycerol or isoleucine, as well as in a combination of the three osmolytes. Cell response was determined using low temperature Raman Spectroscopy and variation in post-thaw recovery with composition was analyzed using statistical modeling. Post-thaw recovery of Jurkat cells in single osmolyte was low. A combination of the osmolytes displayed a non-linear relationship between composition and post-thaw recovery, suggesting that interactions exist between the different solutes. The post-thaw recovery for an optimized multicomponent solution was comparable to that observed using 10% dimethyl sulfoxide and a cooling rate of 1 °C/min. Statistical modeling was used to characterize the importance of each osmolyte in the combination and test for interactions between osmolytes. Higher concentrations of glycerol increase post-thaw recovery and interactions between sucrose and glycerol, as well as sucrose and isoleucine improve post-thaw recovery. Raman images clearly demonstrated that damaging intracellular ice formation was observed more often in the presence of single osmolytes as well as non-optimized multi-component solution compositions.