Comprehensive study of hydrostatic pressure treated human umbilical cord blood cells via response surface method

Amelioration of the survival parameters of cryopreserved samples after thawing has already been addressed through several techniques including vitrification to avoid the formation of ice cores. However, this approach cannot be followed in the case of samples with higher volumes. Hydrostatic pressure (HP) treatment has been proven to increase some qualifying parameters (e.g., motility, insemination efficiency) of certain biological samples. Accordingly, the preparation of umbilical cord blood (UCB) samples through an active (mechanical) pre-stressing process to increase the survival rate of cryopreserved samples can be regarded as a novel strategy that calls for basic experimental studies. The goal of our study was to assess the effects of HP treatment on the qualifying parameters (DNA fragmentation by agarose gel electrophoresis and capillary electrophoresis, Total Nucleotide Cell (TNC) count, CD34+/CD45+ count, and superoxide dismutase activity (SOD) of human umbilical cord blood (UCB) derived cells). The experimental arrangement was set to provide data for response-surface analysis to take into account the common effects of the individual variables of pressure and time exposure. 3D visualization of experimental data revealed that 50-min long HP treatment at 12.5 MPa can significantly (α = 0.05) enhance white blood cell (WBC) and CD34+/CD45+ cell counts. However no DNA fragmentation was observed even at higher pressures, SOD activity was triggered over 15.0 MPa. As a conclusion, HP treatment may contribute to the optimal cryopreservation of UCB cells by significantly increasing WBC and CD34+/CD45+ cell counts without adverse effects neither on DNA stability nor on triggering SOD activity.

Cryopreservation of Peripheral Blood Stem Cells Using a Box-in-Box Cooling Device

The cooling process is critical for the cryopreservation of human hematopoietic stem cells (HSCs). Currently, programmed freezing methods and uncontrolled cooling methods are in use, both having obvious disadvantages. In this article, a novel device termed Box-in-Box (BIB) was developed and evaluated by in vitro cryopreservation tests in 2 different operation modes ("against-side" mode for Group I (n = 10), and "in-middle" mode for Group II (n = 10), respectively), and compared with an uncontrolled cooling method (Group III (n = 7), Styrofoam boxes) as well as a conventional programmed freezer method (Group IV (n = 10), CryoMed TM 1010, Cryogenic Tech., FL). Recorded temperature profiles of samples cryopreserved with BIB show that a consistent cooling procedure with a rate around -1°C to -3.5°C/min can be achieved during their transfer from room temperature to an -80°C freezer. Statistical analysis of the stem cell population recovery, survival, and colony generation recovery shows that there is no significant difference (P > 0.26) among the methods using the BIB or programmed freezer (Group I, Group II, and Group IV), and their related deviations are smaller than the uncontrolled cooling rate method (Group III). Methods using the BIB (Group I and Group II) generated significantly better cell survival rate (P < 0.01) than the uncontrolled cooling rate method (Group III). The results indicate that the controlled cooling rate methods (BIB or CryoMed PF) are more consistent and reliable for clinical use. Considering the advantages of low cost, durability, and no liquid nitrogen consumption for the cooling process, the BIB can be a good alternative to the programmed freezers for the cryopreservation of HSCs.

Quantifying loss of CD34+ cells collected by apheresis after processing for freezing and post-thaw

INTRODUCTION

CD34(+) cells collected for autologous bone marrow transplantation (BMT) are usually quantified in the apheresis product after collection, but the necessity to repeat these measures post-thaw is controversial.

METHODS

We examined the loss of CD34(+) cells after collection, preparation for freezing and post-thaw in apheresis products collected for BMT.

RESULTS

Median number of CD34(+) cells collected per unit was 1.61×10(6)/kg, viability: 97-100%. This number decreased to 1.38×10(6)/kg, viability: 96-100% before freezing and was 1.17×10(6)/kg post-thaw. Viability decreased to 86-98%. The relative loss of viable PBHPC showed an inverse correlation with the ratio "CD34(+) cells/total nucleated cells" (r=-0.45; p=<0.0005). This relative loss was largest in patients with Hodgkin's lymphoma.

CONCLUSION

Cryopreservation and thawing of PBHPCs in leukapheresis products provokes a small but significant stem cell loss. So, quantification of viable CD34(+) cells post-thaw is important, especially in poorly mobilizing patients. Besides, the ratio "CD34(+) cells/total nucleated cells" after leukapheresis is an important parameter for prediction of neutrophil recovery after BMT.

On the application of active learning and Gaussian processes in postcryopreservation cell membrane integrity experiments

Biological cell cryopreservation permits storage of specimens for future use. Stem cell cryostorage in particular is fast becoming a broadly spread practice due to their potential for use in regenerative medicine. For the optimal cryopreservation process, ultralow temperatures are needed. However, elevated temperatures are often unavoidable in a typical sample handling cycle which in turn negatively affects the postcryopreservation integrity of cells. In this paper, we present an application of active learning using an underlying Gaussian Process (GP) model in an experimental study on postcryopreservation membrane integrity response to a range of elevated temperature conditions. We tailored this technique for the current investigation and developed an algorithm which enabled identification of the sampling locations for the experiments in order to obtain the highest information return about the process from a limited size sample set. We applied this algorithm in the experimental study investigating the effects of severe temperature elevation (ranging from -40 to 20 °C) over a short term event (48 hours) on the postcryopreservation membrane integrity of Mesenchymal Stem Cells (MSCs) derived from human bone marrow. The algorithm showed excellent performance by selecting the locations which maximized the reduction of variance of the process response estimate. An approximating GP model developed from this experimental data shows that the elevated temperatures during cryopreservation have an imminent detrimental effect on cell integrity.

Development of a reliable low-cost controlled cooling rate instrument for the cryopreservation of hematopoietic stem cells

BACKGROUND AIMS

An optimal cooling rate is one of the critical factors influencing the survival of cells during cryopreservation. We describe a novel device, called the box-in-box, that has been developed for optimal cryopreservation of human hematopoietic stem cells (HSC).

METHODS

This work presents the design of the device, a mathematical formulation describing the expected temperature histories of samples during the freezing process, along with actual experimental results of thermal profile tests. In experiments, when the box-in-box device was transferred from room temperature to a -80 degrees C freezer, a cooling rate of -1 to -3.5 degrees C/min, which has been widely used for the cryopreservation of HSC, was achieved. In order to evaluate this device further, HSC cryopreservation was compared between the box-in-box device and a commercially available controlled-rate freezer (CryoMed).

RESULTS

The experimental data, including total cell population and CD34(+) hematopoietic progenitor cell recovery rates, viability and cell culture colony assays, showed that the box-in-box worked as well as the CryoMed instrument. There was no significant difference in either survival rate or the culture/colony outcome between the two devices.

CONCLUSIONS

The box-in-box device can work as a cheap, durable, reliable and maintenance-free instrument for the cryopreservation of HSC. This concept of a box-in-box may also be adapted to other cooling rates to support cryopreservation of a wide variety of tissues and cells.

Trehalose and trehalose-based polymers for environmentally benign, biocompatible and bioactive materials

Trehalose is a non-reducing disaccharide that is found in many organisms but not in mammals. This sugar plays important roles in cryptobiosis of selaginella mosses, tardigrades (water bears), and other animals which revive with water from a state of suspended animation induced by desiccation. The interesting properties of trehalose are due to its unique symmetrical low-energy structure, wherein two glucose units are bonded face-to-face by 1→1-glucoside links. The Hayashibara Co. Ltd., is credited for developing an inexpensive, environmentally benign and industrial-scale process for the enzymatic conversion of α-1,4-linked polyhexoses to α,α-d-trehalose, which made it easy to explore novel food, industrial, and medicinal uses for trehalose and its derivatives. Trehalose-chemistry is a relatively new and emerging field, and polymers of trehalose derivatives appear environmentally benign, biocompatible, and biodegradable. The discriminating properties of trehalose are attributed to its structure, symmetry, solubility, kinetic and thermodynamic stability and versatility. While syntheses of trehalose-based polymer networks can be straightforward, syntheses and characterization of well defined linear polymers with tailored properties using trehalose-based monomers is challenging, and typically involves protection and deprotection of hydroxyl groups to attain desired structural, morphological, biological, and physical and chemical properties in the resulting products. In this review, we will overview known literature on trehalose’s fascinating involvement in cryptobiology; highlight its applications in many fields; and then discuss methods we used to prepare new trehalose-based monomers and polymers and explain their properties.