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Abstract Background There remains much interest in improving cryopreservation techniques for advanced therapy medicinal products (ATMPs). Recently, human platelet lysate (hPL) has emerged as a promising candidate to replace fetal bovine serum (FBS) as a xeno-free culture supplement for the expansion of human cell therapy products. Whether hPL can also substitute for FBS in cryopreservation procedures remains poorly studied. Here, we evaluated several cryoprotective formulations based on a proprietary hPL for the cryopreservation of bioengineered tissues and cell therapy products. Methods We tested different xenogeneic-free, pathogen-inactivated hPL (ihPL)- and non-inactivated-based formulations for cryopreserving bioengineered tissue (cellularized nanostructured fibrin agarose hydrogels (NFAHs)) and common cell therapy products including bone marrow-derived mesenchymal stromal cells (BM-MSCs), human dermal fibroblasts (FBs) and neural stem cells (NSCs). To assess the tissue and cellular properties post-thaw of NFAHs, we analyzed their cell viability, identity and structural and biomechanical properties. Also, we evaluated cell viability, recovery and identity post-thaw in cryopreserved cells. Further properties like immunomodulation, apoptosis and cell proliferation were assessed in certain cell types. Additionally, we examined the stability of the formulated solutions. The formulations are under a bidding process with MD Bioproducts (Zurich, Switzerland) and are proprietary. Results Amongst the tissue-specific solutions, Ti5 (low-DMSO and ihPL-based) preserved the viability and the phenotype of embedded cells in NFAHs and preserved the matrix integrity and biomechanical properties similar to those of the standard cryopreservation solution (70% DMEM + 20% FBS + 10% DMSO). All solutions were stable at − 20 °C for at least 3 months. Regarding cell-specific solutions, CeA maintained the viability of all cell types > 80%, preserved the immunomodulatory properties of BM-MSCs and promoted good recovery post-thaw. Besides, both tested solutions were stable at − 20 °C for 18 months. Finally, we established that there is a 3-h window in which thawed NFAHs and FBs maintain optimum viability immersed in the formulated solutions and at least 2 h for BM-MSCs. Conclusions Our results show that pathogen-inactivated solutions Ti5 allocated for bioengineered tissues and CeA allocated for cells are efficient and safe candidates to cryopreserve ATMPs and offer a xenogeneic-free and low-DMSO alternative to commercially available cryoprotective solutions.

Background: There remains much interest in improving cryopreservation techniques for advanced therapy medicinal products (ATMPs). Recently, human platelet lysate (hPL) has emerged as a promising candidate to replace fetal bovine serum (FBS) as a xeno-free culture supplement for the expansion of human cell therapy products. Whether hPL can also substitute for FBS in cryopreservation procedures remains poorly studied. Here, we evaluated several cryoprotective formulations based on a proprietary hPL for the cryopreservation of bioengineered tissues and cell therapy products. Methods: We tested different xenogeneic-free, pathogen-inactivated hPL (ihPL)- and non-inactivated-based formulations for cryopreserving bioengineered tissue (cellularized nanostructured fibrin agarose hydrogels (NFAHs)) and common cell therapy products including bone marrow-derived mesenchymal stromal cells (BM-MSCs), human dermal fibroblasts (FBs) and neural stem cells (NSCs). To assess the tissue and cellular properties post-thaw of NFAHs, we analyzed their cell viability, identity and structural and biomechanical properties. Also, we evaluated cell viability, recovery and identity post-thaw in cryopreserved cells. Further properties like immunomodulation, apoptosis and cell proliferation were assessed in certain cell types. Additionally, we examined the stability of the formulated solutions. The formulations are under a bidding process with MD Bioproducts (Zurich, Switzerland) and are proprietary. Results: Amongst the tissue-specific solutions, Ti5 (low-DMSO and ihPL-based) preserved the viability and the phenotype of embedded cells in NFAHs and preserved the matrix integrity and biomechanical properties similar to those of the standard cryopreservation solution (70% DMEM + 20% FBS + 10% DMSO). All solutions were stable at − 20 °C for at least 3 months. Regarding cell-specific solutions, CeA maintained the viability of all cell types > 80%, preserved the immunomodulatory properties of BM-MSCs and promoted good recovery post-thaw. Besides, both tested solutions were stable at − 20 °C for 18 months. Finally, we established that there is a 3-h window in which thawed NFAHs and FBs maintain optimum viability immersed in the formulated solutions and at least 2 h for BM-MSCs. Conclusions: Our results show that pathogen-inactivated solutions Ti5 allocated for bioengineered tissues and CeA allocated for cells are efficient and safe candidates to cryopreserve ATMPs and offer a xenogeneic-free and low-DMSO alternative to commercially available cryoprotective solutions. [ABSTRACT FROM AUTHOR]

Aims: The use of primary hepatocytes in pharmacological and toxicological research as well as for clinical and biotechnological applications requires adequate storage options for these cells. However, hepatocytes are very susceptible to cryopreservation injury. Based on experience in hypothermic storage of hepatocytes, we, in this study, aimed to optimize hepatocyte cryopreservation. Materials and Methods: Rat hepatocytes were cryopreserved in serum-containing cell culture medium or in serum-free solutions optimized for hypothermic storage, all with 10% dimethyl sulfoxide, using a standard protocol (−1°C/min in a controlled-rate freezer). After rapid thawing, cells were seeded in supplemented Leibovitz-15 cell culture medium without further purification steps. Cell attachment and metabolic activity were assessed. Results: Cell attachment (37% ± 15% vs. 9% ± 7% of noncryopreserved control cells) and metabolic activity (resazurin reduction: 47% ± 23% vs. 25% ± 8%; glucose release: 44% ± 6% vs. 15% ± 7%; and urea production: 31% ± 16% vs. 5% ± 8%) were significantly higher after cryopreservation in the new solution compared to cryopreservation in cell culture medium. Experiments with modified solutions suggested that the protective effect of the new solution is multifactorial. Conclusions: In summary, significant improvement of cell attachment and function compared to cell culture medium was achieved after cryopreservation in serum-free hepatocyte cold storage solution. [ABSTRACT FROM AUTHOR]

Cryopreservation is the only long-term storage option for the storage of vessels and vascular constructs. However, endothelial barrier function is almost completely lost after cryopreservation in most established cryopreservation solutions. We here aimed to improve endothelial function after cryopreservation using the 2D-model of porcine aortic endothelial cell monolayers. The monolayers were cryopreserved in cell culture medium or cold storage solutions based on the 4°C vascular preservation solution TiProtec®, all supplemented with 10% DMSO, using different temperature gradients. After short-term storage at −80°C, monolayers were rapidly thawed and re-cultured in cell culture medium. Thawing after cryopreservation in cell culture medium caused both immediate and delayed cell death, resulting in 11 ± 5% living cells after 24 h of re-culture. After cryopreservation in TiProtec and chloride-poor modifications thereof, the proportion of adherent viable cells was markedly increased compared to cryopreservation in cell culture medium (TiProtec: 38 ± 11%, modified TiProtec solutions ≥ 50%). Using these solutions, cells cryopreserved in a sub-confluent state were able to proliferate during re-culture. Mitochondrial fragmentation was observed in all solutions, but was partially reversible after cryopreservation in TiProtec and almost completely reversible in modified solutions within 3 h of re-culture. The superior protection of TiProtec and its modifications was apparent at all temperature gradients; however, best results were achieved with a cooling rate of −1°C/min. In conclusion, the use of TiProtec or modifications thereof as base solution for cryopreservation greatly improved cryopreservation results for endothelial monolayers in terms of survival and of monolayer and mitochondrial integrity. [ABSTRACT FROM AUTHOR]

Scale-up of a cell-manufacturing system involves an extension of the filling process time because of the increased number of vials to be filled with the cells suspended in a cryopreservation solution. As the solution includes cryoprotective agents such as dimethyl sulfoxide that is toxic to cells, a longer processing time has an adverse impact on the quality of cell products. Therefore, understanding the related cell-decay kinetics is a major challenge for the development of robust and scalable cell-manufacturing systems. In this study, a new set of performance indices were defined to quantify the state and potential of cells suspended in a cryopreservation solution, i.e., the survival ratio of cells suspended in cryopreservation solution was provided for the cell state estimation, and the recovery ratio of cells after freezing and thawing, the attachment efficiency of cells after seeding, and the specific growth rate of surviving cells were provided for the cell potential estimation. Using these indices, the time-dependencies of cell viability variation in human induced pluripotent (hiPSCs) and human mesenchymal stem cells (hMSCs) suspended in a cryopreservation solution were investigated. Based on the obtained kinetic data, strategies for developing and controlling cell-manufacturing systems were discussed. [ABSTRACT FROM AUTHOR]

It was shown that the use of low-toxic cryopreservative based on glycerol (endocellular protectant), hydroxyethyl starch (exocellular protectant), and 3-hydroxy-6-methyl-2-ethylpyridine succinate (restoring component) makes it possible to preserve nucleated blood cells in a viable state at −40°C. [ABSTRACT FROM AUTHOR]

Intense metabolism and fast exhaustion of the energy potential of nucleate blood cells at positive temperatures substantially reduce the duration of their storage in a viable state. However, this transfusion environment is extremely necessary for clinical purposes. The popular method of cell preservation at an ultralow temperature (−196°C) is limited in application because of the use of liquid nitrogen, special equipment, and trained engineering staff. The goal of this study was to develop an efficient and simple method of leukocyte preservation at near-zero temperatures (+2°–0°C) using a standard household refrigerator and a novel cryopreservation solution. [ABSTRACT FROM AUTHOR]