Cryopreservation of organoids: Strategies, innovation, and future prospects

Organoid technology has demonstrated unique advantages in multidisciplinary fields such as disease research, tumor drug sensitivity, clinical immunity, drug toxicology, and regenerative medicine. It will become the most promising research tool in translational research. However, the long preparation time of organoids and the lack of high-quality cryopreservation methods limit the further application of organoids. Although the high-quality cryopreservation of small-volume biological samples such as cells and embryos has been successfully achieved, the existing cryopreservation methods for organoids still face many bottlenecks. In recent years, with the development of materials science, cryobiology, and interdisciplinary research, many new materials and methods have been applied to cryopreservation. Several new cryopreservation methods have emerged, such as cryoprotectants (CPAs) of natural origin, ice-controlled biomaterials, and rapid rewarming methods. The introduction of these technologies has expanded the research scope of cryopreservation of organoids, provided new approaches and methods for cryopreservation of organoids, and is expected to break through the current technical bottleneck of cryopreservation of organoids. This paper reviews the progress of cryopreservation of organoids in recent years from three aspects: damage factors of cryopreservation of organoids, new protective agents and loading methods, and new technologies of cryopreservation and rewarming.

Schisandrin B Improves the Hypothermic Preservation of Celsior Solution in Human Umbilical Cord Mesenchymal Stem Cells

BACKGROUND

Human umbilical cord mesenchymal stem cells (hUCMSCs) have emerged as promising therapy for immune and inflammatory diseases. However, how to maintain the activity and unique properties during cold storage and transportation is one of the key factors affecting the therapeutic efficiency of hUCMSCs. Schisandrin B (SchB) has many functions in cell protection as a natural medicine. In this study, we investigated the protective effects of SchB on the hypothermic preservation of hUCMSCs.

METHODS

hUCMSCs were isolated from Wharton's jelly. Subsequently, hUCMSCs were exposed to cold storage (4 °C) and 24-h re-warming. After that, cells viability, surface markers, immunomodulatory effects, reactive oxygen species (ROS), mitochondrial integrity, apoptosis-related and antioxidant proteins expression level were evaluated.

RESULTS

SchB significantly alleviated the cells injury and maintained unique properties such as differentiation potential, level of surface markers and immunomodulatory effects of hUCMSCs. The protective effects of SchB on hUCMSCs after hypothermic storage seemed associated with its inhibition of apoptosis and the anti-oxidative stress effect mediated by nuclear factor erythroid 2-related factor 2 signaling.

CONCLUSION

These results demonstrate SchB could be used as an agent for hypothermic preservation of hUCMSCs.

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.

Effective Hypothermic Storage of Human Pluripotent Stem Cell-Derived Cardiomyocytes Compatible With Global Distribution of Cells for Clinical Applications and Toxicology Testing

To fully explore the potential of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), efficient methods for storage and shipment of these cells are required. Here, we evaluated the feasibility to cold store monolayers and aggregates of functional CMs obtained from different PSC lines using a fully defined clinical-compatible preservation formulation and investigated the time frame that hPSC-CMs could be subjected to hypothermic storage. We showed that two-dimensional (2D) monolayers of hPSC-CMs can be efficiently stored at 4°C for 3 days without compromising cell viability. However, cell viability decreased when the cold storage interval was extended to 7 days. We demonstrated that hPSC-CMs are more resistant to prolonged hypothermic storage-induced cell injury in three-dimensional aggregates than in 2D monolayers, showing high cell recoveries (>70%) after 7 days of storage. Importantly, hPSC-CMs maintained their typical (ultra)structure, gene and protein expression profile, electrophysiological profiles, and drug responsiveness.

SIGNIFICANCE

The applicability of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) in the clinic/industry is highly dependent on the development of efficient methods for worldwide shipment of these cells. This study established effective clinically compatible strategies for cold (4°C) storage of hPSC-CMs cultured as two-dimensional (2D) monolayers and three-dimensional (3D) aggregates. Cell recovery of 2D monolayers of hPSC-CMs was found to be dependent on the time of storage, and 3D cell aggregates were more resistant to prolonged cold storage than 2D monolayers. Of note, it was demonstrated that 7 days of cold storage did not affect hPSC-CM ultrastructure, phenotype, or function. This study provides important insights into the cold preservation of PSC-CMs that could be valuable in improving global commercial distribution of hPSC-CMs.

Cold Preservation of Human Adult Hepatocytes for Liver Cell Therapy

Hepatocyte transplantation is a promising alternative therapy for the treatment of hepatic failure, hepatocellular deficiency, and genetic metabolic disorders. Hypothermic preservation of isolated human hepatocytes is potentially a simple and convenient strategy to provide on-demand hepatocytes in sufficient quantity and of the quality required for biotherapy. In this study, first we assessed how cold storage in three clinically safe preservative solutions (UW, HTS-FRS, and IGL-1) affects the viability and in vitro functionality of human hepatocytes. Then we evaluated whether such cold-preserved human hepatocytes could engraft and repopulate damaged livers in a mouse model of liver failure. Human hepatocytes showed comparable viabilities after cold preservation in the three solutions. The ability of fresh and cold-stored hepatocytes to attach to a collagen substratum and to synthesize and secrete albumin, coagulation factor VII, and urea in the medium after 3 days in culture was also equally preserved. Cold-stored hepatocytes were then transplanted in the spleen of immunodeficient mice previously infected with adenoviruses containing a thymidine kinase construct and treated with a single dose of ganciclovir to induce liver injury. Engraftment and liver repopulation were monitored over time by measuring the blood level of human albumin and by assessing the expression of specific human hepatic mRNAs and proteins in the recipient livers by RT-PCR and immunohistochemistry, respectively. Our findings show that cold-stored human hepatocytes in IGL-1 and HTS-FRS preservative solutions can survive, engraft, and proliferate in a damaged mouse liver. These results demonstrate the usefulness of human hepatocyte hypothermic preservation for cell transplantation.

Supercooling as a viable non-freezing cell preservation method of rat hepatocytes

Supercooling preservation holds the potential to drastically extend the preservation time of organs, tissues and engineered tissue products, and fragile cell types that do not lend themselves well to cryopreservation or vitrification. Here, we investigate the effects of supercooling preservation (SCP at -4(o)C) on primary rat hepatocytes stored in cryovials and compare its success (high viability and good functional characteristics) to that of static cold storage (CS at +4(o)C) and cryopreservation. We consider two prominent preservation solutions a) Hypothermosol (HTS-FRS) and b) University of Wisconsin solution (UW) and a range of preservation temperatures (-4 to -10 (o)C). We find that there exists an optimum temperature (-4(o)C) for SCP of rat hepatocytes which yields the highest viability; at this temperature HTS-FRS significantly outperforms UW solution in terms of viability and functional characteristics (secretions and enzymatic activity in suspension and plate culture). With the HTS-FRS solution we show that the cells can be stored for up to a week with high viability (~56%); moreover we also show that the preservation can be performed in large batches (50 million cells) with equal or better viability and no loss of functionality as compared to smaller batches (1.5 million cells) performed in cryovials.