Cryopreservation as a Key Element in the Successful Delivery of Cell-Based Therapies-A Review

Cryopreservation is a key enabling technology in regenerative medicine that provides stable and secure extended cell storage for primary tissue isolates and constructs and prepared cell preparations. The essential detail of the process as it can be applied to cell-based therapies is set out in this review, covering tissue and cell isolation, cryoprotection, cooling and freezing, frozen storage and transport, thawing, and recovery. The aim is to provide clinical scientists with an overview of the benefits and difficulties associated with cryopreservation to assist them with problem resolution in their routine work, or to enable them to consider future involvement in cryopreservative procedures. It is also intended to facilitate networking between clinicians and cryo-researchers to review difficulties and problems to advance protocol optimization and innovative design.

Effect of Cryopreservation on Autologous Chimeric Antigen Receptor T Cell Characteristics

As clinical applications for chimeric antigen receptor T cell (CART) therapy extend beyond early phase trials, commercial manufacture incorporating cryopreservation steps becomes a logistical necessity. The effect of cryopreservation on CART characteristics is unclear. We retrospectively evaluated the effect of cryopreservation on product release criteria and in vivo characteristics in 158 autologous CART products from 6 single-center clinical trials. Further, from 3 healthy donor manufacturing runs, we prospectively identified differentially expressed cell surface markers and gene signatures among fresh versus cryopreserved CARTs. Within 2 days of culture initiation, cell viability of the starting fraction (peripheral blood mononuclear cells [PBMNCs]) decreased significantly in the cryo-thawed arm compared to the fresh arm. Despite this, PBMNC cryopreservation did not affect final CART fold expansion, transduction efficiency, CD3%, or CD4:CD8 ratios. In vivo CART persistence and clinical responses did not differ among fresh and cryopreserved final products. In healthy donors, compared to fresh CARTs, early apoptotic cell-surface markers were significantly elevated in cryo-thawed CARTs. Cryo-thawed CARTs also demonstrated significantly elevated expression of mitochondrial dysfunction, apoptosis signaling, and cell cycle damage pathways. Cryopreservation during CART manufacture is a viable strategy, based on standard product release parameters. The clinical impact of cryopreservation-related subtle micro-cellular damage needs further study.

Cryopreservation of Hematopoietic Stem Cells: Emerging Assays, Cryoprotectant Agents, and Technology to Improve Outcomes

Hematopoietic stem cell (HSC) therapy is widely used to treat a growing number of hematological and non-hematological diseases. Cryopreservation of HSCs allows for cells to be transported from the site of processing to the site of clinical use, creates a larger window of time in which cells can be administered to patients, and allows sufficient time for quality control and regulatory testing. Currently, HSCs and other cell therapies conform to the same cryopreservation techniques as cells used for research purposes: cells are cryopreserved in dimethyl sulfoxide (DMSO) at a slow cooling rate. As a result, HSC therapy can result in numerous adverse symptoms in patients due to the infusion of DMSO. Efforts are being made to improve the cryopreservation of HSCs for clinical use. This review discusses advances in the cryopreservation of HSCs from 2007 to the present. The preclinical development of new cryoprotectants and new technology to eliminate cryoprotectants after thawing are discussed in detail. Additional cryopreservation considerations are included, such as cooling rate, storage temperature, and cell concentration. Preclinical cell assessment and quality control are discussed, as well as clinical studies from the past decade that focus on new cryopreservation protocols to improve patient outcomes.

Flow cytometric analyses of the viability, surface marker expression and function of lymphocytes from children following cryopreservation

Flow cytometric analysis is important for the investigation and clinical preparation of lymphocytes from children. However, the strict requirement of cell freshness and inter‑assay variability limits the application of this methodology for pediatric investigations. Therefore, it is necessary to identify a reliable cryopreservative method capable of maintaining high cell viability and proper cell function in lymphocytes from children. In the present study, eight commonly‑used cell cyropreservative methods were used, and their effects on cell viability, surface marker expression and cell function were examined. In addition, how these methods affect the distribution of T‑cell receptor Vβ subfamilies were also determined. The results of the present study provided valuable experimental evidence, based on which the optimal method for the cryopreservation of lymphocytes from children in pediatric investigations and clinical applications can be selected.

Algorithm-driven optimization of cryopreservation protocols for transfusion model cell types including Jurkat cells and mesenchymal stem cells

This investigation describes the use of a differential evolution (DE) algorithm to optimize cryopreservation solution compositions and cooling rates for specific cell types. Jurkat cells (a lymphocyte model cell type) and mesenchymal stem cells (MSCs) were combined with non-DMSO solutions at concentrations dictated by a DE algorithm. The cells were then frozen in 96-well plates at DE algorithm-dictated cooling rates in the range 0.5-10°C/min. The DE algorithm was iterated until convergence resulted in identification of an optimum solution composition and cooling rate, which occurred within six to nine generations (seven to 10 experiments) for both cell types. The optimal composition for cryopreserving Jurkat cells included 300 mm trehalose, 10% glycerol and 0.01% ectoine (TGE) at 10°C/min. The optimal composition for cryopreserving MSCs included 300 mm ethylene glycol, 1 mm taurine and 1% ectoine (SEGA) at 1°C/min. High-throughput concentration studies verified the optimum identified by the DE algorithm. Vial freezing experiments showed that experimental solutions of TGE at 10°C/min resulted in significantly higher viability for Jurkat cells than DMSO at 1°C/min, while experimental solutions of SEGA at 10°C/min resulted in significantly higher recovery for MSCs than DMSO at 1°C/min; these results were solution- and cell type-specific. Implementation of the DE algorithm permits optimization of multicomponent freezing solutions in a rational, accelerated fashion. This technique can be applied to optimize freezing conditions, which vary by cell type, with significantly fewer experiments than traditional methods. Copyright © 2016 John Wiley & Sons, Ltd.

Cryopreservation in Closed Bag Systems as an Alternative to Clean Rooms for Preparations of Peripheral Blood Stem Cells

Autologous and allogeneic stem cell transplantation (SCT) represents a therapeutic option widely used for hematopoietic malignancies. One important milestone in the development of this treatment strategy was the development of effective cryopreservation technologies resulting in a high quality with respect to cell viability as well as lack of contamination of the graft.Stem cell preparations have been initially performed within standard laboratories as it is routinely still the case in many countries. With the emergence of cleanrooms, manufacturing of stem cell preparations within these facilities has become a new standard mandatory in Europe. However, due to high costs and laborious procedures, novel developments recently emerged using closed bag systems as reliable alternatives to conventional cleanrooms. Several hurdles needed to be overcome including the addition of the cryoprotectant dimethylsulfoxide (DMSO) as a relevant manipulation. As a result of the development, closed bag systems proved to be comparable in terms of product quality and patient outcome to cleanroom products. They also comply with the strict regulations of good manufacturing practice.With closed systems being available, costs and efforts of a cleanroom facility may be substantially reduced in the future. The process can be easily extended for other cell preparations requiring minor modifications as donor lymphocyte preparations. Moreover, novel developments may provide solutions for the production of advanced-therapy medicinal products in closed systems.