Beyond membrane integrity: Assessing the functionality of human umbilical vein endothelial cells after cryopreservation

Reducing dimethyl sulfoxide content in Jurkat cell formulations suitable for cryopreservation

Cell-based medicinal products (CBMPs) are usually cryopreserved in formulations containing up to 10 % dimethyl sulfoxide (Me2SO) at temperatures below -145 °C. Although Me2SO effectively protects cells during the freezing process, it can be damaging to cells at ambient temperatures and lead to side effects in patients. The aim of this study was to reduce the amount of Me2SO in cryopreservation formulations for an immortalized T cell line (Jurkat cells). A design of experiment (DoE) approach was applied for formulation development using seven different excipients, i.e., Me2SO, trehalose, sorbitol, proline, ectoine, poloxamer 188 (P188) and poly vinyl pyrrolidone 40 (PVP). A DoE model was generated to predict optimal formulations resulting in a high post-thaw viability and a high glass transition temperature of the formulation to allow for frozen storage without the use of liquid nitrogen. Subsequently a stability study was performed with promising lead candidates over three months at storage temperatures of -145 °C, -80 °C, -40 °C. Three benchmark solutions were used, i.e., Cryostor CS10, CryoSOfree as well as 10 % Me2SO in Roswell Park Memorial Institute Medium (RPMI). The excipient affecting the post-thaw viability of Jurkat cells the most was, as expected, Me2SO, which led to increased viabilities at higher concentrations. Most formulations resulted in similar viabilities for cells stored at -145 °C and -80 °C, whereas samples stored at -40 °C did not survive. In general, benchmark formulations resulted in slightly higher viabilities than the tested formulations. Furthermore, cell samples stored at -80 °C were recultivated in cell culture and the viability was assessed after 24h. The cell viability after 24h was much lower compared to the cells analyzed directly post-thaw, indicating that freeze-thaw damages continue to unfold after thawing. In summary, several promising excipients and combinations thereof, e.g., trehalose and PVP, were identified for the cryopreservation of Jurkat cells with reduced concentrations of Me2SO or Me2SO-free cryopreservation. Additionally, storage at -80 °C is possible for the developed formulations.

Effects of different cryopreservation parameters on the differences between trypan blue and fluorescent SYTO 13/GelRed assays

Post-thaw cell viability assessment is very important in cryopreservation because it is the main assessment method used to optimize cryopreservation protocols for each cell type; hence, having standardized accurate, quick, and reliable assays for post-thaw cell viability measurements is of utmost importance. The trypan blue exclusion assay and nucleic-acid-binding fluorescence-based assays are two different methods for cell viability assessment. Both assays identify cells with damaged membranes by whether they let a compound enter the cell. In this study, these two assays are compared in the context of cryopreservation and the impacts of important cryopreservation parameters on the differences in measurements are investigated. H9c2 myoblasts were cryopreserved with different freezing protocols. Cell membrane integrities were measured immediately after thaw as well as after cryoprotectant removal by a hemocytometer-based trypan blue dye exclusion assay and a dual fluorometric SYTO 13/GelRed assay; and the results were compared. This study quantifies how (i) the absence or presence of different cryoprotectants, (ii) different cell-cryoprotectant incubation conditions, and (iii) the presence or removal of cryoprotectants after thaw affect the differences between these two viability assays.

Anti-Ferroptotic Treatment Deteriorates Myocardial Infarction by Inhibiting Angiogenesis and Altering Immune Response

Mammalian cardiomyocytes have limited regenerative ability. Cardiac disease, such as congenital heart disease and myocardial infarction, causes an initial loss of cardiomyocytes through regulated cell death (RCD). Understanding the mechanisms that govern RCD in the injured myocardium is crucial for developing therapeutics to promote heart regeneration. We previously reported that ferroptosis, a non-apoptotic and iron-dependent form of RCD, is the main contributor to cardiomyocyte death in the injured heart. To investigate the mechanisms underlying the preference for ferroptosis in cardiomyocytes, we examined the effects of anti-ferroptotic reagents in infarcted mouse hearts. The results revealed that the anti-ferroptotic reagent did not improve neonatal heart regeneration, and further compromised the cardiac function of juvenile hearts. On the other hand, ferroptotic cardiomyocytes played a supportive role during wound healing by releasing pro-angiogenic factors. The inhibition of ferroptosis in the regenerating mouse heart altered the immune and angiogenic responses. Our study provides insights into the preference for ferroptosis over other types of RCD in stressed cardiomyocytes, and guidance for designing anti-cell-death therapies for treating heart disease.

Systematic cryopreservation study of cardiac myoblasts in suspension

H9c2 myoblasts are a cell line derived from embryonic rat heart tissue and demonstrate the ability to differentiate to cardiac myotubes upon reduction of the serum concentration (from 10% to 1%) and addition of all-trans retinoic acid in the growth medium. H9c2 cells are increasingly being used as an easy-to-culture proxy for some functions of cardiomyocytes. The cryobiology of cardiac cells including H9c2 myoblasts has not been studied as extensively as that of some cell types. Consequently, it is important to characterize the cryobiological response and systematically develop well-optimized cryopreservation protocols for H9c2 cells to have optimal and consistent viability and functionality after thaw for high quality studies with this cell type. In this work, an interrupted slow cooling protocol (graded freezing) was applied to characterize H9c2 response throughout the cooling profile. Important factors that affect the cell response were examined, and final protocols that provided the highest post-thaw viability are reported. One protocol uses the common cryoprotectant dimethyl sulfoxide combined with hydroxyethyl starch, which will be suitable for applications in which the presence of dimethyl sulfoxide is not an issue; and the other protocol uses glycerol as a substitute when there is a desire to avoid dimethyl sulfoxide. Both protocols achieved comparable post-thaw viabilities (higher than 80%) based on SYTO 13/GelRed flow cytometry results. H9c2 cells cryopreserved by either protocol showed ability to differentiate to cardiac myotubes comparable to fresh (unfrozen) H9c2 cells, and their differentiation to cardiac myotubes was confirmed with i) change in cell morphology, ii) expression of cardiac marker troponin I, and iii) increase in mitochondrial mass.

Temperature Dependence of Membrane Permeability Parameters for Five Cell Types Using Nonideal Thermodynamic Assumptions to Mathematically Model Cryopreservation Protocols

Cryopreservation is the process of preserving biological matter at subzero temperatures for long-term storage. During cryopreservation, cells are susceptible to various injuries that can be mitigated by controlling the cooling and warming profiles and cryoprotective agent (CPA) addition and removal procedures. Mathematical modeling of the changing cell volume at different temperatures can greatly reduce the experiments needed to optimize cryopreservation protocols. Such mathematical modeling requires as inputs the cell membrane permeabilities to water and CPA and the osmotically inactive fraction of the cell. Since the intra- and extracellular solutions are generally thermodynamically nonideal, our group has been incorporating the osmotic virial equation to model the solution thermodynamics that underlie the cell volume change equations, adding the second and third osmotic virial coefficients of the grouped intracellular solute to the cell osmotic parameters that must be measured. In our previous work, we reported methods to obtain cell osmotic parameters at room temperature by fitting experimental cell volume kinetic data with equations that incorporated nonideal solution thermodynamics assumptions. Since the relevant cell volume excursions occur at different temperatures, the temperature dependence of the osmotic parameters plays an important role. In this work, we present a new two-part fitting method to obtain five cell-type-specific parameters (water permeability, dimethyl sulfoxide permeability, osmotically inactive fraction, and the second and third osmotic virial coefficients of the intracellular solution) from experimental measurements of equilibrium cell volume and cell volume as a function of time at room temperature and 0 °C for five cell types, namely, human umbilical vein endothelial cells (HUVECs), H9c2 rat myoblasts, porcine corneal endothelial cells (PCECs), the Jurkat T-lymphocyte cell line, and human cerebral microvascular endothelial cells (hCMECs/D3 cell line). The fitting method in this work is based on both equilibrium and kinetic cell volume data, enabling us to solve some technical challenges and expand our previously reported measurement technique to 0 °C. Finally, we use the measured parameters to model the cell volume changes for a HUVEC cryopreservation protocol to demonstrate the impact of the nonideal thermodynamic assumptions on predicting the changing cell volume during freezing and thawing.

A Comprehensive Look at In Vitro Angiogenesis Image Analysis Software

One of the complex challenges faced presently by tissue engineering (TE) is the development of vascularized constructs that accurately mimic the extracellular matrix (ECM) of native tissue in which they are inserted to promote vessel growth and, consequently, wound healing and tissue regeneration. TE technique is characterized by several stages, starting from the choice of cell culture and the more appropriate scaffold material that can adequately support and supply them with the necessary biological cues for microvessel development. The next step is to analyze the attained microvasculature, which is reliant on the available labeling and microscopy techniques to visualize the network, as well as metrics employed to characterize it. These are usually attained with the use of software, which has been cited in several works, although no clear standard procedure has been observed to promote the reproduction of the cell response analysis. The present review analyzes not only the various steps previously described in terms of the current standards for evaluation, but also surveys some of the available metrics and software used to quantify networks, along with the detection of analysis limitations and future improvements that could lead to considerable progress for angiogenesis evaluation and application in TE research.

Cryopreservation of human cerebral microvascular endothelial cells with glycerol

The cryopreservation of human cerebral microvascular endothelial cells (hCMEC) has facilitated their commercial availability for research studying the blood-brain barrier. The currently employed cryopreservation protocol uses 10% dimethyl sulfoxide (Me2SO) in cell medium, or 5% Me2SO in 95% fetal bovine serum (FBS) as cryoprotective agents (CPAs). However, Me2SO is toxic to cells and FBS is animal-derived and not chemically defined, so reducing the concentrations of these components is desirable. Recently, we showed that cryopreserving hCMEC in cell medium with 5% Me2SO and 6% hydroxyethyl starch (HES) results in over 90% post-thaw cell viability. This previous work was performed using an interrupted slow cooling (graded freezing) approach followed by SYTO13/GelRed staining to assay for membrane integrity. In this paper, we repeated graded freezing of hCMEC in cell medium containing 5% Me2SO and 6% HES, but this time using Calcein AM/propidium iodide staining to ensure that the stain is an equivalent alternative to SYTO13/GelRed for assessment of cell viability, and that results are comparable to those previously published. Next, using graded freezing experiments and Calcein AM/propidium iodide staining, we examined the effectiveness of non-toxic glycerol as a CPA at different concentrations, loading times, and cooling rates. The cryobiological response of hCMEC was used to develop a protocol that optimizes both the permeating and non-permeating capabilities of glycerol. HCMEC in cell medium loaded with 10% glycerol for 1 h at room temperature, ice nucleated at -5 °C and held for 3 min, and then cooled at -1 °C/min to -30 °C before plunging into liquid nitrogen had post-thaw viability of 87.7% ± 1.8%. Matrigel tube formation assay and immunocytochemical staining of junction protein ZO-1 were carried out on post-thaw hCMEC to ensure that the cryopreserved cells were viable and functional, in addition to being membrane-intact.

Comparison of cell viability methods for human mesenchymal/stromal stem cells and human A549 lung carcinoma cells after freeze-thaw stress

For the safety and efficacy of frozen cell therapy products, determination of cellular viability is key. However, results of cell viability measurements do not only depend on the cell line or on the inflicted stress, but also on the assay used, making inter-experimental comparisons difficult. The aim of this study was thus to assess commonly used viability assays in clinically relevant human mesenchymal/stromal stem cells and human A549 lung carcinoma cells. Post freeze-thaw stress viability and proliferation were evaluated under different conditions using trypan blue, acridine orange/DAPI stain, alamarBlue, ATP, and neutral red assays. Significant differences in cell viability between metabolic assays were observed, likely due to their distinct intrinsic detection mechanisms. Membrane-integrity based assays generally overestimated cell viabilities in this study. Furthermore, noticeable differences in inter-assay sensitivities were observed. These differences highlight that cell viability methods should be meticulously selected and their associated results carefully interpreted in a relevant context to ensure reliable conclusions. Indeed, although cell membrane integrity based assays are a popular choice to determine cellular quality attributes after freezing and thawing, we demonstrate that metabolic assays may be more suitable in this context.

Inducible miR-1224 silences cerebrovascular Serpine1 and restores blood flow to the stroke-affected site of the brain

The α-tocotrienol (TCT) form of natural vitamin E is more potent than the better known α-tocopherol against stroke. Angiographic studies of canine stroke have revealed beneficial cerebrovascular effects of TCT. This work seeks to understand the molecular basis of such effect. In mice, TCT supplementation improved perfusion at the stroke-affected site by inducing miR-1224. miRNA profiling of a laser-capture-microdissected stroke-affected brain site identified miR-1224 as the only vascular miR induced. Lentiviral knockdown of miR-1224 significantly blunted the otherwise beneficial effects of TCT on stroke outcomes. Studies on primary brain microvascular endothelial cells revealed direct angiogenic properties of miR-1224. In mice not treated with TCT, advance stereotaxic delivery of an miR-1224 mimic to the stroke site markedly improved stroke outcomes. Mechanistic studies identified Serpine1 as a target of miR-1224. Downregulation of Serpine1 augmented the angiogenic response of the miR-1224 mimic in the brain endothelial cells. The inhibition of Serpine1, by dietary TCT and pharmacologically, increased cerebrovascular blood flow at the stroke-affected site and protected against stroke. This work assigns Serpine1, otherwise known to be of critical significance in stroke, a cerebrovascular function that worsens stroke outcomes. miR-1224-dependent inhibition of Serpine1 can be achieved by dietary TCT as well as by the small-molecule inhibitor TM5441.

Cryopreservation and post-thaw characterization of dissociated human islet cells

The objective of this study is to optimize the cryopreservation of dissociated islet cells and obtain functional cells that can be used in single-cell transcriptome studies on the pathology and treatment of diabetes. Using an iterative graded freezing approach we obtained viable cells after cooling in 10% dimethyl sulfoxide and 6% hydroxyethyl starch at 1°C/min to -40°C, storage in liquid nitrogen, rapid thaw, and removal of cryoprotectants by serial dilution. The expression of epithelial cell adhesion molecule declined immediately after thaw, but recovered after overnight incubation, while that of an endocrine cell marker (HPi2) remained high after cryopreservation. Patch-clamp electrophysiology revealed differences in channel activities and exocytosis of various islet cell types; however, exocytotic responses, and the biophysical properties of voltage-gated Na+ and Ca2+ channels, are sustained after cryopreservation. Single-cell RNA sequencing indicates that overall transcriptome and crucial exocytosis genes are comparable between fresh and cryopreserved dispersed human islet cells. Thus, we report an optimized procedure for cryopreserving dispersed islet cells that maintained their membrane integrity, along with their molecular and functional phenotypes. Our findings will not only provide a ready source of cells for investigating cellular mechanisms in diabetes but also for bio-engineering pseudo-islets and islet sheets for modeling studies and potential transplant applications.

The transfer temperature from slow cooling to cryogenic storage is critical for optimal recovery of cryopreserved mammalian cells

Cryopreservation is a key step for the effective delivery of many cell therapies and for the maintenance of biological materials for research. The preservation process must be carefully controlled to ensure maximum, post-thaw recovery using cooling rates slow enough to allow time for cells to cryodehydrate sufficiently to avoid lethal intracellular ice. This study focuses on determining the temperature necessary at the end of controlled slow cooling before transfer to cryogenic storage which ensures optimal recovery of the processed cell samples. Using nucleated, mammalian cell lines derived from liver (HepG2), ovary (CHO) and bone tissue (MG63) this study has shown that cooling must be controlled to -40°C before transfer to long term storage to ensure optimal cell recovery. No further advantage was seen by controlling cooling to lower temperatures. These results are consistent with collected differential scanning calorimetry data, that indicated the cells underwent an intracellular, colloidal glass transition between -49 and -59°C (Tg’i) in the presence of the cryoprotective agent dimethyl sulfoxide (DMSO). The glass forms at the point of maximum cryodehydration and no further cellular dehydration is possible. At this point the risk of lethal intracellular ice forming on transfer to ultra-low temperature storage is eliminated. In practice it may not be necessary to continue slow cooling to below this temperature as optimal recovery at -40°C indicates that the cells have become sufficiently dehydrated to avoid further, significant damage when transferred into ultra-low temperature storage.

Bioactive Decellularized Extracellular Matrix Derived from 3D Stem Cell Spheroids under Macromolecular Crowding Serves as a Scaffold for Tissue Engineering

Scaffolds for tissue engineering aim to mimic the native extracellular matrix (ECM) that provides physical support and biochemical signals to modulate multiple cell behaviors. However, the majority of currently used biomaterials are oversimplified and therefore fail to provide a niche required for the stimulation of tissue regeneration. In the present study, 3D decellularized ECM (dECM) scaffolds derived from mesenchymal stem cell (MSC) spheroids and with intricate matrix composition are developed. Specifically, application of macromolecular crowding (MMC) to MSC spheroid cultures facilitate ECM assembly in a 3D configuration, resulting in the accumulation of ECM and associated bioactive components. Decellularized 3D dECM constructs produced under MMC are able to adequately preserve the microarchitecture of structural ECM components and are characterized by higher retention of growth factors. This results in a stronger proangiogenic bioactivity as compared to constructs produced under uncrowded conditions. These dECM scaffolds can be homogenously populated by endothelial cells, which direct the macroassembly of the structures into larger cell-carrying constructs. Application of empty scaffolds enhances intrinsic revascularization in vivo, indicating that the 3D dECM scaffolds represent optimal proangiogenic bioactive blocks for the construction of larger engineered tissue constructs.

Controlled Release of Cryoprotectants by Near-Infrared Irradiation for Improved Cell Cryopreservation

Cryopreservation is essential to store living cells and tissues for future use while maintaining the proper levels of cell functions. The use of cryoprotective agents (CPAs) to inhibit intracellular ice formation during cryopreservation is vital for cell survival, but the addition and removal of CPAs and ice recrystallization during rewarming will cause fatal injury to cells. The conventional CPA loading and unloading methods generate osmotic shocks and cause mechanical injury to biological samples, and the conventional method of rewarming using a water bath also leads to ice recrystallization and devitrification. A new CPA-loaded microparticle-based method for loading and photothermal rewarming under near-infrared (NIR) laser irradiation was proposed to overcome these difficulties. We have successfully achieved the controlled release of CPAs (2 M EG, 2 M PG, and 0.5 M trehalose) with a graphene oxide (GO, 0.04% w/v) core from a 1.5% (w/v) sodium alginate shell to the human umbilical vein endothelial cells (HUVECs) within 60 s using NIR laser irradiation (808 nm Lasever at 5000 mW/cm²) and successfully recovered the CPA-loaded cells with 0.04% (w/v) GO in 8-10 s using the same NIR irradiation. The results show that this method achieved 25% higher viability of HUVECs compared to the conventional method. In short, this study proposes a new approach for achieving controlled CPA loading to cells with a photothermal-induced strategy for cell cryopreservation.

Cryopreservation of human cerebral microvascular endothelial cells and astrocytes in suspension and monolayers

The blood-brain barrier (BBB) keeps pathogens and toxins out of the brain but also impedes the entry of pharmaceuticals. Human cerebral microvascular endothelial cells (hCMECs) and astrocytes are the main functional cell components of the BBB. Although available commercially as cryopreserved cells in suspension, improvements in their cryopreservation and distribution as cryopreserved monolayers could enhance BBB in vitro studies. Here, we examined the response to slow cooling and storage in liquid nitrogen of immortalized hCMEC/D3 cells and human primary astrocytes in suspension and in monolayers. HCMEC/D3 cells in suspension cryopreserved in 5% dimethyl sulfoxide (DMSO) and 95% fetal bovine serum or in 5% DMSO and 6% hydroxyethyl starch (HES) showed post-thaw membrane integrities above 90%, similar to unfrozen control. Cryopreservation did not affect the time-dependent ability of hCMEC/D3 cells to form tubes on Matrigel. Primary astrocytes in suspension cryopreserved in the presence of 5% DMSO and 6% HES had improved viability over those cryopreserved in 10% DMSO. Monolayers of single cultures or co-cultures of hCMEC/D3 cells and astrocytes on fibronectin-coated Rinzl coverslips retained membrane integrities and metabolic function, after freezing in 5% DMSO, 6% HES, and 2% chondroitin sulfate, that were comparable to those of unfrozen controls even after overnight incubation. Rinzl is better than glass or Thermanox as an underlying solid substrate for cryopreserving hCMEC/D3 monolayers. Cryopreserved hCMEC/D3 monolayers expressed the junction proteins ZO-1 and claudin-5 similar to their unfrozen counterparts. Hence, we describe improved cryopreservation protocols for hCMEC/D3 cells and astrocytes in suspension, and a novel protocol for the cryopreservation of monolayers of hCMEC/D3 cells and astrocytes as single cultures or co-cultures that could expand their distribution for research on disease modeling, drug screening, and targeted therapy pertaining to the BBB.

An Overview of In Vitro, In Vivo, and Computational Techniques for Cancer-Associated Angiogenesis Studies

Angiogenesis is a crucial area in scientific research because it involves many important physiological and pathological processes. Indeed, angiogenesis is critical for normal physiological processes, including wound healing and embryonic development, as well as being a component of many disorders, such as rheumatoid arthritis, obesity, and diabetic retinopathies. Investigations of angiogenic mechanisms require assays that can activate the critical steps of angiogenesis as well as provide a tool for assessing the efficacy of therapeutic agents. Thus, angiogenesis assays are key tools for studying the mechanisms of angiogenesis and identifying the potential therapeutic strategies to modulate neovascularization. However, the regulation of angiogenesis is highly complex and not fully understood. Difficulties in assessing the regulators of angiogenic response have necessitated the development of an alternative approach. In this paper, we review the standard models for the study of tumor angiogenesis on the macroscopic scale that include in vitro, in vivo, and computational models. We also highlight the differences in several modeling approaches and describe key advances in understanding the computational models that contributed to the knowledge base of the field.

Determination of In Vitro Membrane Permeability by Analysis of Intracellular and Extracellular Fluorescein Signals in Renal Cells

BACKGROUND/AIM

The structural integrity of the eukaryotic cytoplasmic membrane is of crucial importance for its cell biological function and thus for the survival of the cell. Physical and chemical noxae can interact in various ways with components of the cytoplasmic membrane, influence its permeability and thus mediate toxic effects. In the study presented, changes in membrane permeability were quantified by intracellular accumulation of a fluorescent dye and by the release of the fluorescent dye from dye-loaded cells.

MATERIALS AND METHODS

Non-malignant (RC-124) and malignant (786-O, Caki-1) renal cells were permeabilized with different concentrations of Triton X-100. The permeability of the membrane was determined at the single-cell level by the uptake of the dye into the cell inner by flow cytometry. In addition, a fluorescence plate reader was used to detect and quantify the release of the dye into the cell culture supernatant.

RESULTS

Both malignant and non-malignant cells showed a dose-dependent alteration of membrane permeability after treatment with Triton X-100. In the presence of the fluorescent dye, significantly more dye was introduced into the permeabilized cells compared to control incubations. Vice versa, Triton X-100-treated and dye-loaded cells released significantly more dye into the cell culture supernatant.

CONCLUSION

The combination of measurement of intracellular accumulated and extracellular released dye can quantifiably detect changes in membrane permeability due to cell-membrane damage. The combination of two different measurement methods offers additional value in reliable detection of membrane-damaging, potentially toxic influences.

Platelet vesicles are potent inflammatory mediators in red blood cell products and washing reduces the inflammatory phenotype

BACKGROUND

Studies suggest that washing red cell concentrates (RCCs) to remove soluble mediators and/or inflammatory components, such as extracellular vesicles (EVs), may lead to better clinical outcomes. This study tested the hypothesis that non-red blood cell (RBC) generated vesicles in RCC are potent inflammatory mediators in vitro and washing RCCs can reduce these vesicles and subsequently decrease the inflammatory activity of RCCs.

STUDY DESIGN AND METHODS

Sixteen RCCs were pooled and split into four groups based on pre-wash storage time (Day 2 or 14; n = 4/group). Each group was tested 24 hours and 7 days post-wash. Characteristics of RBCs and EVs, cytokines released by monocytes, and expression of human umbilical vein endothelial cells (HUVECs) adhesion molecules were assessed.

RESULTS

All RCCs meet quality standards for hemolysis, hematocrit, and hemoglobin. Washing did not remove residual platelets from RCCs but led to a significant reduction in platelet-EV count regardless of the group. Supernatant of RCCs washed on Day 14 and stored for 24 hours had significantly lower concentrations of RBC-EVs and white blood cell EVs compared to unwashed controls. Supernatant of unwashed RCCs showed higher production of inflammatory cytokines/chemokines MCP-1, IL-8, and TNF-α, and heightened expression of HUVEC VCAM-1, which were significantly reduced by washing. Spiking washed RCC supernatants with platelet-EVs showed significant increase in IL-8, MCP-1, VCAM-1, and E-selection in groups washed on Day 14.

CONCLUSIONS

Platelet-EVs in RCCs are associated with pro-inflammatory activity. As washing significantly reduced RCC immunomodulatory activity, implementation of this process may improve transfusion outcomes.

Immune Complexes Impaired Glomerular Endothelial Cell Functions in Lupus Nephritis

Lupus nephritis (LN) is one of the most common and severe complications of lupus. However, the mechanisms for renal damage have not been well elucidated. There are evidences show that glomerular endothelial cells (GECs) are damaged in LN. Immune complexes can deposit in subendothelial area and could affect GEC functions. In the present study, we used heat-aggregated gamma globulin (HAGG) to simulate immune complexes and investigated their effects on GEC functions. Our results revealed that HAGG impaired different aspect of the GEC functions. HAGG changed cell morphology, upregulated the expression of active caspase-3, inhibited angiogenesis, and increased NO production in GECs. These results provide new clues for the mechanisms of renal damage and the pathology of LN.

New Approach to Cryopreservation of Primary Noncultivated Human Umbilical Vein Endothelium in Biobanking

It is widely accepted that endothelial dysfunction (ED) is a common feature and a risk factor for cardiovascular diseases and metabolic disorders. Cultures of human umbilical vein endothelial cells (HUVECs) are routinely used in cell-based models to study in vitro molecular and cellular mechanisms of development of different aspects of ED. The methods of the HUVEC extraction and expansion are well developed and standardized. However, when large collections of samples are needed for certain projects, or when samples from a rare population of patients should be collected for future experimental use, HUVEC samples should be transferred to a biobank to be saved in liquid nitrogen for a long period of time until the required collection is completed. This scenario is not always convenient since it requires a lot of effort, a large quantity of expensive culture reagents with limited expiration periods, and sometimes special facilities and well-trained cell biologists among the biobank staff. In this project, we evaluated a method of HUVEC cryopreservation, where the stage of cell culturing and expansion before the transfer of samples to the biobank is eliminated. A total of 55 samples of umbilical cord (UC) were obtained from women immediately after delivery. A primary endothelium pellet derived from 17 UC samples was isolated, frozen, and placed in long-term storage in a liquid nitrogen freezer. Other samples were used to obtain HUVEC cultures. We have demonstrated that cryopreservation of primary endothelium pellets from UC veins without culturing and expansion steps does not affect the physiological features of HUVECs. This new approach would improve the efficiency of biobanking logistics, especially in the case of banking of large collections of endothelial samples.

Multiple Mechanisms Drive Calcium Signal Dynamics around Laser-Induced Epithelial Wounds

Epithelial wound healing is an evolutionarily conserved process that requires coordination across a field of cells. Studies in many organisms have shown that cytosolic calcium levels rise within a field of cells around the wound and spread to neighboring cells, within seconds of wounding. Although calcium is a known potent second messenger and master regulator of wound-healing programs, it is unknown what initiates the rise of cytosolic calcium across the wound field. Here we use laser ablation, a commonly used technique for the precision removal of cells or subcellular components, as a tool to investigate mechanisms of calcium entry upon wounding. Despite its precise ablation capabilities, we find that this technique damages cells outside the primary wound via a laser-induced cavitation bubble, which forms and collapses within microseconds of ablation. This cavitation bubble damages the plasma membranes of cells it contacts, tens of microns away from the wound, allowing direct calcium entry from extracellular fluid into damaged cells. Approximately 45 s after this rapid influx of calcium, we observe a second influx of calcium that spreads to neighboring cells beyond the footprint of cavitation. The occurrence of this second, delayed calcium expansion event is predicted by wound size, indicating that a separate mechanism of calcium entry exists, corresponding to cell loss at the primary wound. Our research demonstrates that the damage profile of laser ablation is more similar to a crush injury than the precision removal of individual cells. The generation of membrane microtears upon ablation is consistent with studies in the field of optoporation, which investigate ablation-induced cellular permeability. We conclude that multiple types of damage, including microtears and cell loss, result in multiple mechanisms of calcium influx around epithelial wounds.

Expansion and cryopreservation of porcine and human corneal endothelial cells

Impairment of the corneal endothelium causes blindness that afflicts millions worldwide and constitutes the most often cited indication for corneal transplants. The scarcity of donor corneas has prompted the alternative use of tissue-engineered grafts which requires the ex vivo expansion and cryopreservation of corneal endothelial cells. The aims of this study are to culture and identify the conditions that will yield viable and functional corneal endothelial cells after cryopreservation. Previously, using human umbilical vein endothelial cells (HUVECs), we employed a systematic approach to optimize the post-thaw recovery of cells with high membrane integrity and functionality. Here, we investigated whether improved protocols for HUVECs translate to the cryopreservation of corneal endothelial cells, despite the differences in function and embryonic origin of these cell types. First, we isolated endothelial cells from pig corneas and then applied an interrupted slow cooling protocol in the presence of dimethyl sulfoxide (Me₂SO), with or without hydroxyethyl starch (HES). Next, we isolated and expanded endothelial cells from human corneas and applied the best protocol verified using porcine cells. We found that slow cooling at 1 °C/min in the presence of 5% Me₂SO and 6% HES, followed by rapid thawing after liquid nitrogen storage, yields membrane-intact cells that could form monolayers expressing the tight junction marker ZO-1 and cytoskeleton F-actin, and could form tubes in reconstituted basement membrane matrix. Thus, we show that a cryopreservation protocol optimized for HUVECs can be applied successfully to corneal endothelial cells, and this could provide a means to address the need for off-the-shelf cryopreserved cells for corneal tissue engineering and regenerative medicine.

Human and Swine Dental Pulp Stem Cells Form a Vascularlike Network after Angiogenic Differentiation in Comparison with Endothelial Cells: A Quantitative Analysis

INTRODUCTION

The aim of this study was to quantify vascular network formation capacity after angiogenic induction of human and swine dental pulp stem cells (DPSCs) in comparison with endothelial cells.

METHODS

Primary human DPSCs or swine DPSCs were induced in endothelial growth medium for 7 days. The expression of the endothelial marker von Willebrand factor was determined by immunostaining. Induced DPSCs (iDPSCs) and noninduced DPSCs (niDPSCs) were seeded at different cell numbers onto Matrigel (BD Biosciences, San Jose, CA) for vascular network formation assays and analyzed after 4, 8, 12, and 18 hours in comparison with human microvascular endothelial cells (hMECs). Quantitative analysis of vascular tubule formation was performed using ImageJ software (National Institutes of Health, Bethesda, MD). The vascular network formation was also conducted by coculturing of niDPSCs and iDPSCs.

RESULTS

Von Willebrand factor was detected by immunofluorescence in both niDPSCs and iDPSCs (human and swine). Time-lapse microscopic observation showed that the vascular network was formed by iDPSCs but not niDPSCs. After 4 hours, iDPSCs showed vascular network formation, whereas niDPSCs started to aggregate and formed clusters. Human iDPSCs displayed a similar capacity to form vascular networks in Matrigel compared with hMECs based on quantitative analysis. Swine iDPSCs had a higher capacity compared with human iDPSCs or hMECs (P < .05) in forming the network structures including segments, nodes, and mesh. A coculture experiment showed that human niDPSCs colocalized on the angiogenic tubules and vascular networks that were formed by human iDPSCs.

CONCLUSIONS

Our findings indicate that iDPSCs in combination with their noninduced counterparts may be used as a future clinical strategy for enhancing angiogenesis during the process of pulp-dentin regeneration.

Improved Cryopreservation of Human Umbilical Vein Endothelial Cells: A Systematic Approach

Cryopreservation of human umbilical vein endothelial cells (HUVECs) facilitated their commercial availability for use in vascular biology, tissue engineering and drug delivery research; however, the key variables in HUVEC cryopreservation have not been comprehensively studied. HUVECs are typically cryopreserved by cooling at 1 °C/min in the presence of 10% dimethyl sulfoxide (DMSO). We applied interrupted slow cooling (graded freezing) and interrupted rapid cooling with a hold time (two-step freezing) to identify where in the cooling process cryoinjury to HUVECs occurs. We found that linear cooling at 1 °C/min resulted in higher membrane integrities than linear cooling at 0.2 °C/min or nonlinear two-step freezing. DMSO addition procedures and compositions were also investigated. By combining hydroxyethyl starch with DMSO, HUVEC viability after cryopreservation was improved compared to measured viabilities of commercially available cryopreserved HUVECs and viabilities for HUVEC cryopreservation studies reported in the literature. Furthermore, HUVECs cryopreserved using our improved procedure showed high tube forming capability in a post-thaw angiogenesis assay, a standard indicator of endothelial cell function. As well as presenting superior cryopreservation procedures for HUVECs, the methods developed here can serve as a model to optimize the cryopreservation of other cells.