The effect of magnetic field during freezing and thawing of rat bone marrow-derived mesenchymal stem cells

An oscillating magnetic field suppresses ice-crystal growth during rapid freezing of muscle tissue of mice

Regenerative medicine would benefit from a safe and efficient cryopreservation method to prevent the structural disruption caused by ice-crystal formation in cells and tissue. Various attempts have been made to overcome this problem, one of which is the use of an oscillating magnetic field (OMF). However, the underlying mechanism is unclear. In this study, to evaluate the effect of an OMF on ice-crystal formation in the leg muscles of mice, we used to use the frozen-section method with a slower freezing rate than is, usual which resulted in ice crystals forming in the tissue. We assessed the mean size and number per unit area of intracellular ice holes in sections of muscle tissue, with and without OMF. Ice-crystal growth was reduced in frozen tissue subjected to OMF. Furthermore, we evaluated the structure and function of proteins in frozen tissue subjected to OMF by immunostaining using an anti-dystrophin antibody and by enzymatic histochemistry for NADH-TR and myosin ATPase. The results imply that the ability of OMF to suppress ice-crystal growth might be related to their stabilization of bound water in biomolecules during freezing.

Effect of Static Magnetic Field Assisted Thawing on Physicochemical Quality and Microstructure of Frozen Beef Tenderloin

Although freezing is the most common and widespread way to preserve food for a long time, the accumulation of microstructural damage caused by ice crystal formation during freezing and recrystallization phenomena during thawing tends to degrade the quality of the product. Thus, the side effects of the above processes should be avoided as much as possible. To evaluate the effect of different magnetic field strength assisted thawing (MAT) on beef quality, the indicators associated with quality of MAT-treated (10-50 Gs) samples and samples thawed without an external magnetic field were compared. Results indicated that the thawing time was reduced by 21.5-40% after applying MAT. Meat quality results demonstrated that at appropriate magnetic field strengths thawing loss, TBARS values, cooking loss, and shear force were significantly decreased. Moreover, by protecting the microstructure of the muscle, MAT significantly increased the a∗ value and protein content. MAT treatment significantly improved the thawing efficiency and quality of frozen beef, indicating its promising application in frozen meat thawing.

Novel synergistic freezing methods and technologies for enhanced food product quality: A critical review

Freezing has a long history as an effective food preservation method, but traditional freezing technologies have quality limitations, such as the potential for water loss and/or shrinkage and/or nutrient loss, etc. in the frozen products. Due to enhanced quality preservation and simpler thawing operation, synergistic technologies for freezing are emerging as the optimal methods for frozen food processing. This article comprehensively reviewed the recently developed synergistic technologies for freezing and pretreatment, for example, ultrasonication, cell alive system freezing, glass transition temperature regulation, high pressure freezing, pulsed electric field pretreatment, osmotic pretreatment, and antifreeze protein pretreatment, etc. The mechanisms and applications of these techniques are outlined briefly here. Though the application of new treatments in freezing is relatively mature, reducing the energy consumption in the application of these new technologies is a key issue for future research. It is also necessary to consider scale-up issues involved in large-scale applications as much of the research effort so far is limited to laboratory or pilot scale. For future development, intelligent freezing should be given more attention. Freezing should automatically identify and respond to different freezing conditions according to the nature of different materials to achieve more efficient freezing. PRACTICAL APPLICATION: This paper provides a reference for subsequent production and research, and analyzes the advantages and disadvantages of different novel synergistic technologies, which points out the direction for subsequent industry development and research. At the same time, it provides new ideas for the freezing industry.

Bovine-Derived Xenografts Immobilized With Cryopreserved Stem Cells From Human Adipose and Dental Pulp Tissues Promote Bone Regeneration: A Radiographic and Histological Study

Adipose tissue-derived stem cells (ADSCs) and dental pulp stem cells (DPSCs) have become promising sources for bone tissue engineering. Our study aimed at evaluating bone regeneration potential of cryopreserved ADSCs and DPSCs combined with bovine-derived xenografts with 10% porcine collagen. In vitro studies revealed that although DPSCs had higher proliferative abilities, ADSCs exhibited greater mineral depositions and higher osteogenic-related gene expression, indicating better osteogenic differentiation potential of ADSCs. After applying cryopreserved ADSCs and DPSCs in a critical-sized calvarial defect model, both cryopreserved mesenchymal stem cells significantly improved bone volume density and new bone area at 2, 4, and 8 weeks. Furthermore, the combined treatment with ADSCs and xenografts was more efficient in enhancing bone repair processes compared to combined treatment with DPCSs at all-time points. We also evaluated the sequential early bone healing process both histologically and radiographically, confirming a high agreement between these two methods. Based on these results, we propose grafting of the tissue-engineered construct seeded with cryopreserved ADSCs as a useful strategy in accelerating bone healing processes.

Evaluation of the effects of weak oscillating magnetic fields applied during freezing on systems of different complexity

The effects of weak oscillating magnetic fields (OMFs ≤7 mT at 50 Hz) on freezing were studied in three systems of different complexity. To do so, ferric chloride solutions, lactate dehydrogenase (LDH), and minced hake muscle experimentally infected with Anisakis L3 were frozen with and without OMF application. OMFs did not affect freezing kinetics of either ferric chloride solutions or minced hake muscle. LDH activity, Anisakis mortality, and water-holding capacity of the hake muscle after thawing were not affected by OMF either. Further studies are needed to evaluate the effectiveness of stronger OMFs in a wider frequency range.

Effect of the Cell Alive System on nerve tissue cryopreservation

Effective cellular cryopreservation while maintaining high cell viability is achieved by preventing intracellular and extracellular ice crystal formation using the Cells Alive System (CAS), a programmed freezer that applies a magnetic field. Here, the optimal temperature settings of the CAS were determined using rat sciatic nerves as a model tissue. Firstly, it was found that Schwann cell survival was increased by pre-cooling the samples in the ice crystal formation zone, increasing the freeze-thaw speed, and freezing-thawing in a magnetic field. Secondly, the setting (intensity and frequency) of the magnetic field at freezing-thawing was changed, and the optimum magnetic field strength was determined by evaluating cell viability. At the set temperature excluding previous studies, the minimum temperature was set to - 50 °C and kept frozen for 15 min, and then thawed immediately. The highest cell viability (27%) was achieved at 0.67 mT (intensity 3 [29.6 V] and frequency setting 10 [60 Hz]). The effects of the freeze-thaw program were assessed using transplanted sciatic nerve tissues removed after 2, 4, and 8 weeks. Anterior tibial muscle wet weight increased at 8 weeks in the control (without freezing) and after freezing-thawing in a magnetic field, compared to that without a magnetic field. Fluorescence staining of the sciatic nerve with anti-S100 antibodies revealed that Schwann cell counts increased at the transplanted site (at 8 weeks) of nerves that were freeze-thawed in a magnetic field. Overall, the CAS prevented ice crystal formation in rat sciatic nerves and could be used to maintain cell viability during cryopreservation.

Magnetic field and nano-scaffolds with stem cells to enhance bone regeneration

Novel strategies utilizing magnetic nanoparticles (MNPs) and magnetic fields are being developed to enhance bone tissue engineering efficacy. This article first reviewed cutting-edge research on the osteogenic enhancements via magnetic fields and MNPs. Then the current developments in magnetic strategies to improve the cells, scaffolds and growth factor deliveries were described. The magnetic-cell strategies included cell labeling, targeting, patterning, and gene modifications. MNPs were incorporated to fabricate magnetic composite scaffolds, as well as to construct delivery systems for growth factors, drugs and gene transfections. The novel methods using magnetic nanoparticles and scaffolds with magnetic fields and stem cells increased the osteogenic differentiation, angiogenesis and bone regeneration by 2-3 folds over those of the controls. The mechanisms of magnetic nanoparticles and scaffolds with magnetic fields and stem cells to enhance bone regeneration were identified as involving the activation of signaling pathways including MAPK, integrin, BMP and NF-κB. Potential clinical applications of magnetic nanoparticles and scaffolds with magnetic fields and stem cells include dental, craniofacial and orthopedic treatments with substantially increased bone repair and regeneration efficacy.

Cells in the Non-Uniform Magnetic World: How Cells Respond to High-Gradient Magnetic Fields

Imagine cells that live in a high-gradient magnetic field (HGMF). Through what mechanisms do the cells sense a non-uniform magnetic field and how such a field changes the cell fate? We show that magnetic forces generated by HGMFs can be comparable to intracellular forces and therefore may be capable of altering the functionality of an individual cell and tissues in unprecedented ways. We identify the cellular effectors of such fields and propose novel routes in cell biology predicting new biological effects such as magnetic control of cell-to-cell communication and vesicle transport, magnetic control of intracellular ROS levels, magnetically induced differentiation of stem cells, magnetically assisted cell division, or prevention of cells from dividing. On the basis of experimental facts and theoretical modeling we reveal timescales of cellular responses to high-gradient magnetic fields and suggest an explicit dependence of the cell response time on the magnitude of the magnetic field gradient.

Effect of cryopreservation on proliferation and differentiation of periodontal ligament stem cell sheets

BACKGROUND

Cryopreservation has been extensively applied to the long-term storage of a diverse range of biological materials. However, no comprehensive study is currently available on the cryopreservation of periodontal ligament stem cell (PDLSC) sheets which have been suggested as excellent transplant materials for periodontal tissue regeneration. The aim of this study is to investigate the effect of cryopreservation on the structural integrity and functional viability of PDLSC sheets.

METHODS

PDLSC sheets prepared from extracted human molars were divided into two groups: the cryopreservation group (cPDLSC sheets) and the freshly prepared control group (fPDLSC sheets). The cPDLSC sheets were cryopreserved in a solution consisting of 90% fetal bovine serum and 10% dimethyl sulfoxide for 3 months. Cell viability and cell proliferation rates of PDLSCs in both groups were evaluated by cell viability assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, respectively. The multilineage differentiation potentials of the cells were assessed by von Kossa staining and Oil Red O staining. The chromosomal stability was examined by karyotype analysis. Moreover, the cell sheets in each group were transplanted subcutaneously into the dorsal site of nude mice, after which Sirius Red staining was performed to analyze the efficiency of tissue regeneration.

RESULTS

The PDLSCs derived from both groups of cell sheets showed no significant difference in their viability, proliferative capacities, and multilineage differentiation potentials, as well as chromosomal stability. Furthermore, transplantation experiments based on a mouse model demonstrated that the cPDLSC sheets were equally effective in generating viable osteoid tissues in vivo as their freshly prepared counterparts. In both cases, the regenerated tissues showed similar network patterns of bone-like matrix.

CONCLUSIONS

Our results offer convincing evidence that cryopreservation does not alter the biological properties of PDLSC sheets and could enhance their clinical utility in tissue regeneration.