The influence of freezing and storage on the characteristics and functions of human mesenchymal stromal cells isolated for clinical use

Optimizing cryopreservation conditions for use of fucosylated human mesenchymal stromal cells in anti-inflammatory/immunomodulatory therapeutics

Mesenchymal stem/stromal cells (MSCs) are being increasingly used in cell-based therapies due to their broad anti-inflammatory and immunomodulatory properties. Intravascularly-administered MSCs do not efficiently migrate to sites of inflammation/immunopathology, but this shortfall has been overcome by cell surface enzymatic fucosylation to engender expression of the potent E-selectin ligand HCELL. In applications of cell-based therapies, cryopreservation enables stability in both storage and transport of the produced cells from the manufacturing facility to the point of care. However, it has been reported that cryopreservation and thawing dampens their immunomodulatory/anti-inflammatory activity even after a reactivation/reconditioning step. To address this issue, we employed a variety of methods to cryopreserve and thaw fucosylated human MSCs derived from either bone marrow or adipose tissue sources. We then evaluated their immunosuppressive properties, cell viability, morphology, proliferation kinetics, immunophenotype, senescence, and osteogenic and adipogenic differentiation. Our studies provide new insights into the immunobiology of cryopreserved and thawed MSCs and offer a readily applicable approach to optimize the use of fucosylated human allogeneic MSCs as immunomodulatory/anti-inflammatory therapeutics.

Biopolymer gels as components of protective medium for cryopreservation of spermatogonial stem cells

Biopolymer gels attract a lot of attention in a field of biothechnology due to their excellent compatibility and degradation. Their application is also promising for cryopreservation of spermatogonial stem cells (SSCs) which is so necessary to preserve the fertility of young patients. The aim of the study was to determine the effectiveness of biopolymer gels as a component of cryopreservation medium for SSCs of immature rats at the stage of exposure to cryoprotectants. It was found that 30-min exposure to cryopreservation media based on collagen or fibrin gel with an addition of 5% Me₂SO or 6% glycerol did not lead to significant changes in membrane integrity, cytochrome C content, metabolic, mitochondrial and antioxidant activities in SSCs compared to the control (Leibovitz-based cryomedium). But fibrin gel more than collagen reduced the toxic effects of Me₂SO and glycerol on SSCs increasing exposure time up to 45 min without significant changes in cell viability. The same cryoprotectants in Leibovitz-based media showed significant toxicity starting from the 15th minute of exposure. Necrosis was the main cause of cell death at this stage of cryopreservation in all experimental groups. The obtained results can be used to optimize SSC cryopreservation protocols for further cell autotransplantation for spermatogenesis initiation in boys who undergo gonadotoxic therapy in prepubertal age.

Overview of current adipose-derived stem cell (ADSCs) processing involved in therapeutic advancements: flow chart and regulation updates before and after COVID-19

Adipose-derived stem cells (ADSCs) have raised big interest in therapeutic applications in regenerative medicine and appear to fulfill the criteria for a successful cell therapy. Their low immunogenicity and their ability to self-renew, to differentiate into different tissue-specific progenitors, to migrate into damaged sites, and to act through autocrine and paracrine pathways have been altogether testified as the main mechanisms whereby cell repair and regeneration occur. The absence of standardization protocols in cell management within laboratories or facilities added to the new technologies improved at patient's bedside and the discrepancies in cell outcomes and engraftment increase the limitations on their widespread use by balancing their real benefit versus the patient safety and security. Also, comparisons across pooled patients are particularly difficult in the fact that multiple medical devices are used and there is absence of harmonized assessment assays despite meeting regulations agencies and efficient GMP protocols. Moreover, the emergence of the COVID-19 breakdown added to the complexity of implementing standardization. Cell- and tissue-based therapies are completely dependent on the biological manifestations and parameters associated to and induced by this virus where the scope is still unknown. The initial flow chart identified for stem cell therapies should be reformulated and updated to overcome patient infection and avoid significant variability, thus enabling more patient safety and therapeutic efficiency. The aim of this work is to highlight the major guidelines and differences in ADSC processing meeting the current good manufacturing practices (cGMP) and the cellular therapy-related policies. Specific insights on standardization of ADSCs proceeding at different check points are also presented as a setup for the cord blood and bone marrow.

The impact of cryopreservation on bone marrow-derived mesenchymal stem cells: a systematic review

Mesenchymal stem cells (MSCs) represent an invaluable asset for the field of cell therapy. Human Bone marrow-derived MSCs (hBM-MSCs) are one of the most commonly used cell types in clinical trials. They are currently being studied and tested for the treatment of a wide range of diseases and conditions. The future availability of MSCs therapies to the public will require a robust and reliable delivery process. Cryopreservation represents the gold standard in cell storage and transportation, but its effect on BM-MSCs is still not well established. A systematic review was conducted to evaluate the impact of cryopreservation on BM-MSCs and to attempt to uncover the reasons behind some of the controversial results reported in the literature. Forty-one in vitro studies were analysed, and their results organised according to the cell attributes they assess. It was concluded that cryopreservation does not affect BM-MSCs morphology, surface marker expression, differentiation or proliferation potential. However, mixed results exist regarding the effect on colony forming ability and the effects on viability, attachment and migration, genomic stability and paracrine function are undefined mainly due to the huge variabilities governing the cryopreservation process as a whole and to the lack of standardised assays.

Efficacy of mesenchymal stem cell therapy in systolic heart failure: a systematic review and meta-analysis

Background

Heart failure (HF) is the end stage of most heart disease. Mesenchymal stem cells (MSCs), with their specific biological effects, have been applied in several clinical trials to evaluate the efficacy in HF therapy. We performed this meta-analysis to review the clinical evidence of their therapeutic effect on HF.

Methods

Three databases were searched. The outcomes of interest were death, readmission, the 6-min walk test (6MWT), New York Heart Association (NYHA) class and left ventricular ejection fraction (LVEF). The relative risk (RR) and weighted mean difference (WMD) were calculated to evaluate the effects of MSCs on HF compared to placebo.

Results

A total of nine studies were included, involving 612 patients who underwent MSCs or placebo treatment. The overall rate of death showed a trend of reduction of 36% (RR [CI] = 0.64 [0.35, 1.16], p = 0.143) in the MSC treatment group. The incidence of readmission was reduced by 34% (RR [CI] = 0.66 [0.51, 0.85], p = 0.001). The patients in the MSC treatment group realised an average of 40.44 m (WMD [95% CI] = 40.44 m [19.07, 61.82], p < 0.0001) improvement in 6MWT. The NYHA class was reduced obviously in the MSC group (WMD [95% CI] = − 0.42 [− 0.64, − 0.20], p < 0.0001). The changes of LVEF from baseline were significantly more than 5.25% (WMD [95% CI] = 5.25 [3.58, 6.92], p < 0.0001) in the MSCs group, unlike in the placebo group.

Conclusions

Our results suggested that MSC treatment is an effective therapy for HF by improving the prognosis and exercise capacity. SCs derived from allosomes have superior therapeutic effects, and intracoronary injection is the optimum MSC delivery approach. Short-term cryopreservation is feasible in MSCs storage or transport.

Influence of patient related factors on number of mesenchymal stromal cells reached after in vitro culture expansion for clinical treatment

BACKGROUND

Number of stromal cells injected in patients with ischaemic heart disease (IHD) may be of importance for the treatment efficacy, which in turn may be influenced by various patient-related factors. In this study, we investigate whether patient-related factors influence the number of autologous stromal cells reached after in vitro culture expansion for clinical therapy.

METHODS

Culture expansion data from 111 patients with IHD treated with autologous stromal cells in three clinical trials were used. We correlated the final cell count after two passages of cultivation with different patient factors.

RESULTS

There was a significant relation between body mass index (BMI) and the number of adipose derived stromal cells (ASCs) reached after culture expansion and for all patients included into the three studies (r = 0.375, p = .019 and r = 0.200, p = .036, respectively). Moreover, there was a significantly higher number of ASCs reached in patients with hypertension compared to those without hypertension and for all patients overall (68.8 ± 39.6 × 10⁶ vs. 39.1 ± 23.6 × 10⁶, p = .020 and 62.0 ± 55.0 × 10⁶ vs. 29.0 ± 19.3 × 10⁶, p < .001, respectively). The same tendency was seen with bone marrow derived mesenchymal stromal cells (MSCs) in patients with hypertension compared to those without hypertension (58.4 ± 61.8 × 10⁶ vs. 22.6 ± 13.3 × 10⁶, p < .001) and in males compared to females (56.4 ± 61.5 × 10⁶ vs. 30.9 ± 27.9 × 10⁶, p = .041). Moreover, a significant negative correlation between left ventricular ejection fraction and number of MSCs was found (r = -0.287, p = .017).

CONCLUSIONS

Patient related factors such as BMI, hypertension and gender may influence the number of MSCs reached after in vitro culture expansion.

Preservation media, durations and cell concentrations of short-term storage affect key features of human adipose-derived mesenchymal stem cells for therapeutic application

Background

Adipose-derived mesenchymal stem cells (ADSCs) have shown great potential in the treatment of various diseases. However, the optimum short-term storage condition of ADSCs in 2∼8 °C is rarely reported. This study aimed at optimizing a short-term storage condition to ensure the viability and function of ADSCs before transplantation.

Methods

Preservation media and durations of storage were evaluated by cell viability, apoptosis, adhesion ability and colony-forming unit (CFU) capacity of ADSCs. The abilities of cell proliferation and differentiation were used to optimize cell concentrations. Optimized preservation condition was evaluated by cell surface markers, cell cycle and immunosuppressive capacity.

Results

A total of 5% human serum albumin in multiple electrolytes (ME + HSA) was the optimized medium with high cell viability, low cluster rate, good adhesion ability and high CFU capacity of ADSCs. Duration of storage should be limited to 24 h to ensure the quality of ADSCs before transplantation. A concentration of 5 × 10⁶ cells/ml was the most suitable cell concentration with low late stage apoptosis, rapid proliferation and good osteogenic and adipogenic differentiation ability. This selected condition did not change surface markers, cell cycle, indoleamine 2, 3-dioxygenase 1 (IDO1) gene expression and kynurenine (Kyn) concentration significantly.

Discussion

In this study, ME + HSA was found to be the best medium, most likely due to the supplement of HSA which could protect cells, the physiological pH (7.4) of ME and sodium gluconate ingredient in ME which could provide energy for cells. Duration should be limited to 24 h because of reduced nutrient supply and increased waste and lactic acid accumulation during prolonged storage. To keep cell proliferation and limit lactic acid accumulation, the proper cell concentration is 5× 10⁶ cells/ml. Surface markers, cell cycle and immunosuppressive capacity did not change significantly after storage using the optimized condition, which confirmed our results that this optimized short-term storage condition of MSCs has a great potential for the application of cell therapy.

The proliferative potential of human cardiac stem cells was unaffected after a long-term cryopreservation of tissue blocks

BACKGROUND

Human c-kit-positive cardiac stem cells (CSCs) have been used to treat patients suffering from ischemic cardiomyopathy. This study aimed to investigate whether a long-term storage of cardiac tissues would influence the growth potential of the subsequently isolated CSCs.

METHODS

A total of 34 fresh samples were obtained from various cardiac regions [right atrium (RA), left atrium (LA), and/or left ventricle (LV)] of 21 patients. From 12 of these patients, 18 samples kept frozen for ~2 years were employed to prepare and characterize the CSCs. After confirming the specificity of the cell sorting by c-kit immunolabeling, the growth rate (number of doublings per day), BrdU positivity, and colony forming unit (CFU) were measured in each CSC population; the values were compared among distinct cardiac regions as well as between fresh and frozen tissues from which CSCs were derived.

RESULTS

Among independent measurements indicating growth potential, the growth rate and BrdU positivity remarkably correlated in freshly prepared CSCs. The cells obtained from every examined region displayed a high proliferative capacity with the growth rate of 0.48±0.19 and the BrdU positivity of 15.0%±7.6%. The right atrial CSCs tended to show a greater growth than those in the other two areas. Similarly, the CSCs were isolated from tissue blocks, cryopreserved for ~2 years, and compared with CSCs derived from the fresh specimens of the same patients. Importantly, we were able to obtain and culture CSCs from every frozen material, and their proliferative potential, represented by the growth rate of 0.47±0.22 and the BrdU positivity of 13.7%±7.9%, was not inferior to that of the freshly prepared cells.

CONCLUSIONS

The long-term cryopreservation of cardiac tissues did not affect the growth potential of the derivative CSCs. Our findings should expand the therapeutic applications of these cells over a longer time span.

Cryobanking Mesenchymal Stem Cells

Cryopreservation and storage of culture-expanded mesenchymal stem cells (MSCs) is essential for a biobank to maintain a collection of cell lines for research and clinical use. Optimization of cryopreservation protocols and methods to minimize damage to cells during freezing and thawing is critical to ensure reliable availability of viable cells. Controlling the freezing rate and the use of appropriate cryoprotectant, as well as stable storage temperature, can minimize the negative effects on cell viability. In this chapter, protocols for cryopreserving MSCs are described.

Comparison of Mesenchymal Stem Cell Surface Markers from Bone Marrow Aspirates and Adipose Stromal Vascular Fraction Sites

The objective of this study was to subjectively evaluate the harvest of two areas of adipose collection and three areas of bone marrow collection as potential sites for clinical harvest of adipose stromal vascular fraction (SVF) and bone marrow concentrate for clinical use by quantifying the amount of tissue harvested, subjective ease of harvest, the variation of each site, and determining the cell surface marker characteristics using commercially available antibodies. Bone marrow and adipose tissue samples were collected from 10 adult mixed breed dogs. Adipose tissue was collected from the caudal scapular region and falciform fat ligament. Bone marrow aspirates were collected from the ilium, humerus, and tibia. Tissues were weighed (adipose) or measured by volume (bone marrow), processed to isolate the SVF or bone marrow concentrate, and flow cytometry was performed to quantitate the percentage of cells that were CD90, CD44 positive, and CD45 negative. Sites and tissue types were compared using matched pairs t-test. Subjectively subcutaneous fat collection was the most difficult and large amounts of tissue dissection were necessary. Additionally the subcutaneous area yielded less than the goal amount of tissue. The bone marrow harvest ranged from 10 to 27.5 ml. Adipose tissue had the highest concentration of cells with CD90⁺, CD44⁺, and CD45⁻ markers (P < 0.05), and bone marrow had the highest total number of these cells at harvest (P < 0.05). Variation was high for all sites, but the adipose collection yielded more consistent results. These results describe the relative cellular components in the SVF of adipose tissue and bone marrow as defined by the biomarkers chosen. Although bone marrow yielded higher absolute cell numbers on average, adipose tissue yielded more consistent results. Fat from the falciform ligament was easily obtained with less dissection and therefore created less perceived relative patient trauma.

Mesenchymal stromal cells derived from various tissues: Biological, clinical and cryopreservation aspects

Originally isolated from bone marrow, mesenchymal stromal cells (MSCs) have since been obtained from various fetal and post-natal tissues and are the focus of an increasing number of clinical trials. Because of their tremendous potential for cellular therapy, regenerative medicine and tissue engineering, it is desirable to cryopreserve and bank MSCs to increase their access and availability. A remarkable amount of research and resources have been expended towards optimizing the protocols, freezing media composition, cooling devices and storage containers, as well as developing good manufacturing practices in order to ensure that MSCs retain their therapeutic characteristics following cryopreservation and that they are safe for clinical use. Here, we first present an overview of the identification of MSCs, their tissue sources and the properties that render them suitable as a cellular therapeutic. Next, we discuss the responses of cells during freezing and focus on the traditional and novel approaches used to cryopreserve MSCs. We conclude that viable MSCs from diverse tissues can be recovered after cryopreservation using a variety of freezing protocols, cryoprotectants, storage periods and temperatures. However, alterations in certain functions of MSCs following cryopreservation warrant future investigations on the recovery of cells post-thaw followed by expansion of functional cells in order to achieve their full therapeutic potential.

The mesenchymal stromal cell magic bullet finds yet another target

Rojas and colleagues have presented an exciting paper demonstrating yet another relevant preclinical setting in which the mesenchymal stromal cell has a potential therapeutic application. What is particularly interesting about this study is that it addresses a disease, blood-borne systemic sepsis, which has multiple complex host responses and involves a variety of disparate organs and immune cell types. Here, the authors focus on how this injury relates more specifically to the lung, with quite dramatic improvements in several assessed injury parameters. Where does this latest demonstration of mesenchymal stromal cell efficacy leave us with regard to getting these cell therapies to the acute respiratory distress syndrome patient?

Expanded cryopreserved mesenchymal stromal cells as an optimal source for graft-versus-host disease treatment

Mesenchymal stromal cells (MSC) are fibroblast-like cells present in different types of tissues. Their immunomodulatory potential represents a promising method for post-transplant immunotherapy in the treatment of GVHD (graft-versus-host disease) with suboptimal response to standard immunosuppression. In this study we tested influence of 1-8 month-long cryopreservation on ability of MSC to suppress activation of non-specifically stimulated lymphocytes. We did not observe any changes in proliferation capacity of MSC after thawing. Lymphocytes metabolic activity was inhibited by 30% and number of dividing cells was three times smaller in the presence of MSC. Two activation markers were studied (CD25 and CD69) to confirm preservation of functional cell integrity. Expression of CD25 antigen on CD3(+)CD4(+) and CD3(+)CD4(-) cells was decreased in all co-cultivated samples. Level of CD69 expression on CD3(+)CD4(+) cells was lower in samples with added MSC (10-15% on day +2) but without reaching statistical significance. The lower expression (approximately 5%) was observed also on CD4-cells. The study confirms the preservation of immunomodulatory properties of cryopreserved and re-expanded MSC. Aliquots with cryopreserved cells can represent an optimal source for a quick preparation of MSC cell product with the possibility to apply the same cells repeatedly.

Mesenchymal stem cells for regenerative therapy: optimization of cell preparation protocols

Administration of bone marrow-derived mesenchymal stem cells (MSCs) is an innovative approach for the treatment of a range of diseases that are not curable by current therapies including heart failure. A number of clinical trials have been completed and many others are ongoing; more than 2,000 patients worldwide have been administered with culture-expanded allogeneic or autologous MSCs for the treatment of various diseases, showing feasibility and safety (and some efficacy) of this approach. However, protocols for isolation and expansion of donor MSCs vary widely between these trials, which could affect the efficacy of the therapy. It is therefore important to develop international standards of MSC production, which should be evidence-based, regulatory authority-compliant, of good medical practice grade, cost-effective, and clinically practical, so that this innovative approach becomes an established widely adopted treatment. This review article summarizes protocols to isolate and expand bone marrow-derived MSCs in 47 recent clinical trials of MSC-based therapy, which were published after 2007 onwards and provided sufficient methodological information. Identified issues and possible solutions associated with the MSC production methods, including materials and protocols for isolation and expansion, are discussed with reference to relevant experimental evidence with aim of future clinical success of MSC-based therapy.

Autotransplantation of mesenchymal stromal cells from bone-marrow to heart in patients with severe stable coronary artery disease and refractory angina--final 3-year follow-up

BACKGROUND

The study assessed long-term safety and efficacy of intramyocardial injection of autologous bone-marrow derived mesenchymal stromal cells (BMMSCs) in patients with severe stable coronary artery disease (CAD) and refractory angina.

METHODS

Thirty-one patients with severe stable CAD and refractory angina were included. Patients had reversible myocardial ischemia and no further revascularization options. Autologous BMMSCs were isolated, culture expanded and stimulated with vascular endothelial growth-factor to facilitate endothelial differentiation. BMMSCs were injected into an ischemic, viable region of the myocardium. Patients were followed for 3 years.

RESULTS

We found significant clinical improvements in exercise time (p=0.0016), angina class (CCS) (p<0.0001), weekly number of angina attacks (p<0.0001) and use of nitroglycerine from (p=0.0017). In the Seattle Angina Questionnaire there were significant improvements in physical limitation score, angina stability score, angina frequency score and quality of life score (all p<0.0001). When comparing all hospital admissions from 3 years before to 3 years after treatment, we observed highly reduced admission rates for stable angina (p<0.0001), revascularization (p=0.003) and overall cardiovascular disease (p<0.0001). No early or late side-effects of the treatment were observed.

CONCLUSIONS

The final 3-year follow-up data after intramyocardial injection of autologous BMMSCs, in patients with severe CAD and refractory angina, demonstrated sustained clinical effects, reduced hospital admissions for cardiovascular disease and excellent long-term safety. The results indicate that autotransplantation of BMMSCs to the heart does not only improve symptoms but also slows down disease progression.

Gene therapy approaches to regenerating bone

Bone formation and regeneration therapies continue to require optimization and improvement because many skeletal disorders remain undertreated. Clinical solutions to nonunion fractures and osteoporotic vertebral compression fractures, for example, remain suboptimal and better therapeutic approaches must be created. The widespread use of recombinant human bone morphogenetic proteins (rhBMPs) for spine fusion was recently questioned by a series of reports in a special issue of The Spine Journal, which elucidated the side effects and complications of direct rhBMP treatments. Gene therapy - both direct (in vivo) and cell-mediated (ex vivo) - has long been studied extensively to provide much needed improvements in bone regeneration. In this article, we review recent advances in gene therapy research whose aims are in vivo or ex vivo bone regeneration or formation. We examine appropriate vectors, safety issues, and rates of bone formation. The use of animal models and their relevance for translation of research results to the clinical setting are also discussed in order to provide the reader with a critical view. Finally, we elucidate the main challenges and hurdles faced by gene therapy aimed at bone regeneration as well as expected future trends in this field.

Effect of different freezing rates during cryopreservation of rat mesenchymal stem cells using combinations of hydroxyethyl starch and dimethylsulfoxide

Background

Mesenchymal stem cells (MSCs) are increasingly used as therapeutic agents as well as research tools in regenerative medicine. Development of technologies which allow storing and banking of MSC with minimal loss of cell viability, differentiation capacity, and function is required for clinical and research applications. Cryopreservation is the most effective way to preserve cells long term, but it involves potentially cytotoxic compounds and processing steps. Here, we investigate the effect of decreasing dimethyl sulfoxide (DMSO) concentrations in cryosolution by substituting with hydroxyethyl starch (HES) of different molecular weights using different freezing rates. Post-thaw viability, phenotype and osteogenic differentiation capacity of MSCs were analysed.

Results

The study confirms that, for rat MSC, cryopreservation effects need to be assessed some time after, rather than immediately after thawing. MSCs cryopreserved with HES maintain their characteristic cell surface marker expression as well as the osteogenic, adipogenic and chondrogenic differentiation potential. HES alone does not provide sufficient cryoprotection for rat MSCs, but provides good cryoprotection in combination with DMSO, permitting the DMSO content to be reduced to 5%. There are indications that such a combination would seem useful not just for the clinical disadvantages of DMSO but also based on a tendency for reduced osteogenic differentiation capacity of rat MSC cryopreserved with high DMSO concentration. HES molecular weight appears to play only a minor role in its capacity to act as a cryopreservation solution for MSC. The use of a ‘straight freeze’ protocol is no less effective in maintaining post-thaw viability of MSC compared to controlled rate freezing methods.

Conclusion

A 5% DMSO / 5% HES solution cryopreservation solution using a ‘straight freeze’ approach can be recommended for rat MSC.

Direct intramyocardial mesenchymal stromal cell injections in patients with severe refractory angina: one-year follow-up

In patients with stable coronary artery disease (CAD) and refractory angina, we performed direct intramyocardial injections of autologous mesenchymal stromal cells (MSC) and followed the safety and efficacy of the treatment for 12 months. A total of 31 patients with stable CAD, moderate to severe angina, normal left ventricular ejection fraction, and no further revascularization options were included. Bone marrow MSCs were isolated and culture expanded for 6-8 weeks and then stimulated with vascular endothelial growth factor (VEGF) for 1 week. The 12-month follow-up demonstrated that it was safe to culture expand MSCs and use the cells for clinical treatment. The patients' maximal metabolic equivalent (MET) during exercise increased from 4.23 MET at baseline to 4.72 MET at 12-month follow-up (p < 0.001), Canadian Cardiovascular Society Class (CCS) was reduced from 3.0 to 0.8 (p < 0.001), angina attacks per week from 13.8 to 3.2 (p < 0.001), and nitroglycerin consumption from 10.7 to 3.4 per week (p < 0.001). In addition, Seattle Angina Questionnaire (SAQ) evaluations demonstrated highly significant improvements in physical limitation, angina stability, angina frequency, and quality of life (p < 0.001 for all). It is safe in the intermediate/long term to treat patients with stable CAD using autologous culture expanded MSCs. Previously reported, early and highly significant improvements in exercise capacity and clinical symptoms persist after 12 months. The results are encouraging, and a larger controlled study is warranted.

Collection and propagation methods for mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are derived from adult mesenchymal tissues and have the ability to undergo differentiation into bone, cartilage, and fat, and have therefore attracted great interest in regenerative medicine. Many isolation and culture methods have been described, making comparison between laboratories and quality-control protocols difficult. A uniform protocol to characterize equine MSC has recently been proposed, aiming to introduce consistency across the equine stem cell research field. This article reviews the published techniques for collection and propagation of equine MSC, focusing on bone marrow-derived and adipose-derived cells.

Evaluation of bone marrow-derived mesenchymal stem cells after cryopreservation and hypothermic storage in clinically safe medium

Achievements in tissue engineering using mesenchymal stem cells (MSC) demand a clinically acceptable "off-the-shelf" cell therapy product. Efficacy of cryopreservation of human bone marrow-derived MSC in clinically safe, animal product-free medium containing 2%, 5%, and 10% dimethyl sulfoxide (DMSO) was evaluated by measuring cell recovery, viability, apoptosis, proliferation rate, expression of a broad panel of MSC markers, and osteogenic differentiation. Rate-controlled freezing in CryoStor media was performed in a programmable cell freezer. About 95% of frozen cells were recovered as live cells after freezing in CryoStor solutions with 5% and 10% DMSO followed by storage in liquid nitrogen for 1 month. Cell recovery after 5 months storage was 72% and 80% for 5% and 10% DMSO, respectively. Measurements of caspase 3 activity demonstrated that 15.5% and 12.8% of cells after 1 month and 18.3% and 12.9% of cells after 5 months storage in 5% and 10% DMSO, respectively, were apoptotic. Proliferation of MSC recovered after cryopreservation was measured during 2 weeks post-plating. Proliferation rate was not compromised and was even enhanced. Cryopreservation did not alter expression of MSC markers. Quantitative analysis of alkaline phosphatase (ALP) activity, ALP surface expression and Ca⁺⁺ deposition in previously cryopreserved MSC and then differentiated for 3 weeks in osteogenic medium demonstrated the same degree of osteogenic differentiation as in unfrozen parallel cultures. Cell viability and functional parameters were analyzed in MSC after short-term storage at 4°C in HypoThermosol-FRS solution, also free of animal products. Hypothermic storage for 2 and 4 days resulted in about 100% and 85% cell recovery, respectively, less than 10% of apoptotic cells, and normal proliferation, marker expression, and osteogenic potential. Overall, our results demonstrate that human MSC could be successfully cryopreserved for banking and clinical applications and delivered to the bedside in clinically safe protective reagents.

Mesenchymal stromal cells for cell therapy: besides supporting hematopoiesis

Mesenchymal stromal cells (MSC) have attracted the attention of scientists and clinicians due to their self-renewal, capacity for multipotent differentiation, and immunomodulatory properties. Some essential problems remain to be solved before the clinical application of MSC. Platelet lysate (PL) has recently been used as a substitute for FBS in MSC amplification in vitro to achieve clinically applicable numbers of MSC. In addition to promising trials in regenerative medicine, such as in the treatment of major bone defects and myocardial infarction, MSC have shown therapeutic effect other than direct hematopoiesis support in hematopoietic reconstruction. It has been confirmed that MSC promote hematopoietic cell engraftment and immune recovery after allogeneic hematopoietic stem cell transplantation, probably through the provision of cytokines, matrix proteins, and cell-to-cell contacts. Their suppressive effects on immune cells, including T cells, B cells, NK cells and DC cells, suggest MSCs as a novel therapy for GVHD and other autoimmune disorders. These cells thus present as promising candidates for cellular therapy in the fields of regenerative medicine, allogeneic hematopoietic stem cell transplantation, and autoimmune disorders.

Optimization of cryopreservation procedures for porcine endothelial progenitor cells

Endothelial progenitor cells (EPCs) provide a powerful option for therapeutic use in ischemic diseases. The cell therapy-induced vasculogenesis requires sufficient homogeneous cells, and cryopreservation is a prerequisite for long-term storage and quality assurance of EPCs. The aim of this study was to optimize cryopreservation protocols of EPCs derived from porcine bone marrow. Bone marrow-derived mononuclear cells (MNCs) were isolated by density centrifugation and differentiated into EPCs. The first passage EPCs were frozen by using different methodologies, and after cryopreservation the thawed cells were cultured to the fourth passage. The recovery efficiency and functions of these cells were evaluated by determination of cell viability, proliferation and migration. We found the optimal conditions for cryopreservation of EPCs as follows: (i) a cryopreservation medium consisting of 10% dimethylsulphoxide (DMSO) in combination with 50% fetal bovine serum (FBS); (ii) using a controlled freezing rate at 5°C/min; (iii) at an optimal density of 5×10⁶/ml for cryopreserved EPCs; (iv) a storage temperature of -156°C. Under these conditions we demonstrated that EPCs could be stored in mechanical freezer for up to 18 months after cryopreservation without losing their phenotypic characteristics and biological functions.

Mesenchymal stromal cell derived endothelial progenitor treatment in patients with refractory angina

AIMS

We evaluated the feasibility, safety and efficacy of intra-myocardial injection of autologous mesenchymal stromal cells derived endothelial progenitor cell (MSC) in patients with stable coronary artery disease (CAD) and refractory angina in this first in man trial.

METHODS AND RESULTS

A total of 31 patients with stable CAD, moderate to severe angina and no further revascularization options, were included. Bone marrow MSC were isolated and culture expanded for 6-8 weeks. It was feasible and safe to establish in-hospital culture expansion of autologous MSC and perform intra-myocardial injection of MSC. After six months follow-up myocardial perfusion was unaltered, but the patients increased exercise capacity (p < 0.001), reduction in CCS Class (p < 0.001), angina attacks (p < 0.001) and nitroglycerin consumption (p < 0.001), and improved Seattle Angina Questionnaire (SAQ) evaluations (p < 0.001). For all parameters there was a tendency towards improved outcome with increasing numbers of cells injected. In the MRI substudy: ejection fraction (p < 0.001), systolic wall thickness (p = 0.03) and wall thickening (p = 0.03) all improved.

CONCLUSIONS

The study demonstrated that it was safe to treat patients with stable CAD with autologous culture expanded MSC. Moreover, MSC treated patients had significant improvement in left ventricular function and exercise capacity, in addition to an improvement in clinical symptoms and SAQ evaluations.

Stem cells therapy for cardiovascular repair in ischemic heart disease: How to predict and secure optimal outcome?

Coronary artery disease is a growing problem worldwide. Early treatment with stabilizing drugs and revascularization by percutaneous coronary intervention or by-pass surgery has reduced the mortality significantly, but it is still the most common cause of death and a major cause of hospital admissions in industrialized countries. Treatment with stem cells with the potential to regenerate the damaged myocardium is a relatively new approach. However, the results from clinical studies on stem cell therapy for cardiac regeneration in patients with acute or chronic ischemic heart disease have been inconsistent. Some of the discrepancy could be due differences in study designs or patient selection. The review will based on conducted clinical stem cell trials try to elucidate how to predict and personalize this new treatment approach.

Cryopreservation and revival of mesenchymal stromal cells

Over the past few years, the pace of preclinical stem cell research is astonishing and adult stem cells have become the subject of intense research. Due to the presence of promising supporting preclinical data, human clinical trials for stem cell regenerative treatment of various diseases have been initiated. As there has been a precedent for the use of bone marrow stem cells in the treatment of hematological malignancies and ischemic heart diseases through randomized clinical safety and efficacy trials, the development of new therapies based on culture-expanded human mesenchymal stromal cells (MSCs) opens up new possibilities for cell therapy. To facilitate these applications, cryopreservation and long-term storage of MSCs becomes an absolute necessity. As a result, optimization of this cryopreservation protocol is absolutely critical. The major challenge during cellular cryopreservation is the lethality associated with the cooling and thawing processes. The major objective is to minimize damage to cells during low temperature freezing and storage and the use of a suitable cryoprotectant. The detrimental effects of cellular cryopreservation can be minimized by controlling the cooling rate, using better cryoprotective agents, maintaining appropriate storage temperatures, and controlling the cell thawing rate. As is described in this chapter, human MSCs can either be frozen in cryovials or in freezing bags together with cryopreserve solutions containing dimethyl sulfoxide (DMSO).

Hypoxic preconditioning induces the expression of prosurvival and proangiogenic markers in mesenchymal stem cells

Stem cells transplanted to the ischemic myocardium usually encounter massive cell death within a few days of therapy. Hypoxic preconditioning (HPC) is currently employed as a strategy to prepare stem cells for increased survival and engraftment in the heart. However, HPC of stem cells has provided varying results, supposedly due to the differences in the oxygen concentration, duration of exposure, and passage conditions. In the present study, we determined the effect of HPC on rat mesenchymal stem cells (MSCs) exposed to 0.5% oxygen concentration for 24, 48, or 72 h. We evaluated the expression of prosurvival, proangiogenic, and functional markers such as hypoxia-inducible factor-1α, VEGF, phosphorylated Akt, survivin, p21, cytochrome c, caspase-3, caspase-7, CXCR4, and c-Met. MSCs exposed to 24-h hypoxia showed reduced apoptosis on being subjected to severe hypoxic conditions. They also had significantly higher levels of prosurvival, proangiogenic, and prodifferentiation proteins when compared with longer exposure (72 h). Cells taken directly from the cryopreserved state did not respond effectively to the 24-h HPC as those that were cultured under normoxia before HPC. Cells cultured under normoxia before HPC showed decreased apoptosis, enhanced expression of connexin-43, cardiac myosin heavy chain, and CD31. The preconditioned cells were able to differentiate into the cardiovascular lineage. The results suggest that MSCs cultured under normoxia before 24-h HPC are in a state of optimal expression of prosurvival, proangiogenic, and functional proteins that may increase the survival and engraftment in the infarct heart. These results could provide further insights into optimal preparation of MSCs which would greatly influence the effectiveness of cell therapy in vivo.

Mesenchymal stromal cell and mononuclear cell therapy in heart disease

Despite progress in percutaneous coronary intervention, bypass surgery and drug therapy, rates of mortality and morbidity after acute coronary syndrome are high due to ventricular remodeling and heart failure. Mesenchymal stromal cells (MSCs) from adult bone marrow or adipose tissue are considered potential candidates for therapeutic regenerative treatment in cardiovascular disease. Recent animal studies have demonstrated that MSCs can induce neovascularization and improve myocardial function in postinfarction myocardial ischemic hearts. This review will focus on the present preclinical and clinical knowledge about the use of mononuclear cells and MSCs for cardiac regenerative medicine, the source of MSCs for clinical use and problems to consider when conducting clinical MSC therapy.

Serial in vivo imaging of the porcine heart after percutaneous, intramyocardially injected 111In-labeled human mesenchymal stromal cells

This pilot trial aimed to investigate the utilization of (111)In-labeling of mesenchymal stromal cells (MSC) for in vivo tracking after intramyocardial transplantation in a xenotransplantation model with gender mismatched cells. Human male MSC were expanded ex vivo and labeled with (111)In-tropolone. Ten female pigs were included. The labeled cells were transplanted intramyocardially using a percutaneous injection system. The (111)In activity was determined using gamma camera imaging. Excised hearts were analyzed by fluorescence in situ hybridization (FISH) and microscopy. Gamma camera imaging revealed focal cardiac (111)In accumulations up to 6 days after injection (N = 4). No MSC could be identified with FISH, and microscopy identified widespread acute inflammation. Focal (111)In accumulation, inflammation but no human MSC were similarly seen in pigs (N = 2) after immunosuppression. A comparable retention of (111)In activity was observed after intramyocardial injection of (111)In-tropolone (without cells) (N = 2), but without sign of myocardial inflammation. Injection of labeled non-viable cells (N = 1) also led to high focal (111)In activity up to 6 days after intramyocardial injection. As a positive control of the FISH method, we identified labeled cells both in culture and immediately after cell injection in one pig. This pilot trial suggests that after intramyocardial injection (111)In stays in the myocardium despite possible disappearance of labeled cells. This questions the clinical use of (111)In-labeled cells for tracking. The results further suggest that xenografting of human MSC into porcine hearts leads to inflammation contradicting previous studies implying a special immunoprivileged status for MSC.

Mesenchymal stem cells in hematopoietic stem cell transplantation

Mesenchymal stromal/stem cells (MSC) of bone marrow (BM) origin not only provide the supportive microenvironmental niche for hematopoietic stem cells (HSC) but are capable of differentiating into various cell types of mesenchymal origin, such as bone, fat and cartilage. In vitro and in vivo data suggest that MSC have low inherent immunogenicity, modulate/suppress immunologic responses through interactions with immune cells, and home to damaged tissues to participate in regeneration processes through their diverse biologic properties. MSC derived from BM are being evaluated for a wide range of clinical applications, including disorders as diverse as myocardial infarction and newly diagnosed diabetes mellitus type 1. However, their use in HSC transplantation, either for enhancement of hematopoietic engraftment or for treatment/prevention of graft-versus-host disease, is far ahead of other indications. Ease of isolation and ex vivo expansion of MSC, combined with their intriguing immunomodulatory properties and their impressive record of safety in a wide variety of clinical trials, make these cells promising candidates for further investigation.

Liquid storage of marrow stromal cells

BACKGROUND

Marrow stromal cells (MSCs) for clinical trials are inevitably stored before administration, but little is known about the effects of storage on MSCs. The effects of short-term liquid storage on the in vitro function of MSCs intended for a clinical trial were studied.

STUDY DESIGN AND METHODS

Early-passage human MSCs were suspended in 0.9% saline or culture medium and stored at 4 degrees C or room temperature for up to 72 hours followed by assessment of cell loss, viability, and growth in culture.

RESULTS

When stored in saline at 4 degrees C, MSC counts decreased by 5% to 20%, MSC viability decreased 17% to 37%, and MSC growth decreased 65% to 100% after 24-hour storage. Similar results were obtained by MSC storage at room temperature or in Dulbecco's modified Eagle's medium or by addition of 1% human serum albumin (HSA) from two manufacturers. Storage of MSCs in saline with HSA from a third manufacturer maintained MSC viability at prestorage levels and improved poststorage MSC growth versus saline (32 +/- 9% vs. 9 +/- 9%; p < 0.05) or saline with two other HSA preparations (4 +/- 4 and 8 +/- 11%; p < 0.05).

CONCLUSION

MSCs stored at 4 degrees C or room temperature, in saline or culture medium, rapidly become nonviable. HSA preparations vary significantly in their ability to maintain poststorage MSC viability and growth. These results provide insight regarding the effects of storage on MSCs and indicate the need to screen HSA preparations before their use as additives to preserve MSCs during short-term liquid storage.

Timing of granulocyte-colony stimulating factor treatment after acute myocardial infarction and recovery of left ventricular function: results from the STEMMI trial

BACKGROUND

Granulocyte-colony stimulating factor (G-CSF) therapy after ST-elevation myocardial infarction (STEMI) have not demonstrated impact on systolic recovery compared to placebo. However, recent studies suggest that timing of G-CSF therapy is crucial.

METHODS

Timing of G-CSF treatment was analyzed in the STEMMI MRI subpopulation including 54 patients with STEMI treated with primary percutaneous coronary intervention (PCI) <12 h after symptom onset. Patients were randomized to double blind treatment with G-CSF (10 microg/kg/day) or placebo. Treatment was initiated from 17 to 65 h (mean 30) after PCI. Left ventricular ejection fraction (LVEF) was evaluated with MRI.

RESULTS

Recovery of LVEF from baseline to 6 months was not associated with time from PCI to G-CSF. An identical improvement in LVEF was found in the placebo group and the G-CSF group (p=0.8). There was no correlation between time from PCI to G-CSF and maximum plasma concentration of CD34+ cells (r=-0.3, p=0.1). Similar results were found from data on recovery of the infarction size and change in the systolic wall thickening.

CONCLUSIONS

In the time window from 17 to 65 h after STEMI treated with PCI, the timing of G-CSF treatment does not seem to affect the recovery of LVEF. It remains to be determined if very early, or very late G-CSF treatment might be effective.

Therapeutic applications of mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are multipotent cells that can be derived from many different organs and tissues. They have been demonstrated to play a role in tissue repair and regeneration in both preclinical and clinical studies. They also have remarkable immunosuppressive properties. We describe their application in settings that include the cardiovascular, central nervous, gastrointestinal, renal, orthopaedic and haematopoietic systems. Manufacturing of MSC for clinical trials is also discussed. Since tissue matching between MSC donor and recipient does not appear to be required, MSC may be the first cell type able to be used as an "off-the-shelf" therapeutic product.