Methodologies for Scalable Production of High-Quality Purified Small Extracellular Vesicles from Conditioned Medium.

The development of an extracellular vesicles (EV)-based therapeutic product requires the implementation of reproducible and scalable, purification protocols for clinical-grade EV. Commonly used isolation methods including ultracentrifugation, density gradient centrifugation, size exclusion chromatography, and polymer-based precipitation, faced limitations such as yield efficiency, EV purity, and sample volume. We developed a GMP-compatible method for the scalable production, concentration, and isolation of EV through a strategy involving, tangential flow filtration (TFF). We applied this purification method for the isolation of EV from conditioned medium (CM) of cardiac stromal cells, namely cardiac progenitor cells (CPC) which has been shown to possess potential therapeutical application in heart failure. Conditioned medium collection and EV isolation using TFF demonstrated consistent particle recovery (~1013 particle/mL) enrichment of small/medium-EV subfraction (range size 120-140 nm). EV preparations achieved a 97% reduction of major protein-complex contaminant and showed unaltered biological activity. The protocol describes methods to assess EV identity and purity as well as procedures to perform downstream applications including functional potency assay and quality control tests. The large-scale manufacturing of GMP-grade EV represents a versatile protocol that can be easily applied to different cell sources for wide range of therapeutic areas.

Efficacy of Intraoperative Vein Graft Storage Solutions in Preserving Endothelial Cell Integrity during Coronary Artery Bypass Surgery.

(1) Introduction: Intraoperative preservation solutions for saphenous vein grafts may influence the endothelial structure and increase the risk of graft failure after coronary surgery. The aim of the study was to compare the efficacy of three solutions in maintaining the endothelial cell integrity of venous segments. (2) Methods: We tested the efficacy of physiological saline solution (PSS), heparinized autologous blood (HAB) and DuraGraft® in preserving the endothelium of vein segments by evaluating the degree of endothelial cell apoptosis. Two incubation times (2 and 4 h from harvesting) were used for each solution. The quantification of apoptotic cells was computed as the intensity nuclei/intensity area ratio. (3) Results: After 2 h of ischemia, the degree of apoptosis decreased progressively across the use of DuraGraft, HAB and PSS (p = 0.004), although only the difference between DuraGraft and PSS yielded a statistical significance (p = 0.002). After 4 h, a similar decrease in apoptosis was shown across the three media; however, statistical significance was not reached. The analysis of the elapsed time (2 or 4 h of incubation) showed that this was a relevant factor in maintaining the endothelial structural integrity independently from the storage solution (test for interaction of media and time p = 0.010). (4) Conclusion: Within 2 h of incubation, endothelial structural integrity depended on the incubating medium. DuraGraft better protected the SVG against ischemic-induced apoptosis when compared to saline solution. Prolonged ischemia was associated with extended endothelium damage and none of the studied solutions protected the vein graft.

GMP-Grade Methods for Cardiac Progenitor Cells: Cell Bank Production and Quality Control.

Cardiac explant-derived cells (cEDC), also referred as cardiac progenitors cells (CPC) (Barile et al., Cardiovasc Res 103(4):530-541, 2014; Barile et al., Cardiovasc Res 114(7):992-1005, 2018), represent promising candidates for the development of cell-based therapies, a novel and interesting treatment for cardioprotective strategy in heart failure (Kreke et al., Expert Rev Cardiovasc Ther 10(9):1185-1194, 2012). CPC have been tested in a preclinical setting for direct cell transplantation and tissue engineering or as a source for production of extracellular vesicles (EV) (Oh et al., J Cardiol 68(5):361-367, 2016; Barile et al., Eur Heart J 38(18):1372-1379, 2017; Rosen et al., J Am Coll Cardiol 64(9):922-937, 2014). CPC cultured as cardiospheres derived cells went through favorable Phase 1 and 2 studies demonstrating safety and possible efficacy (Makkar et al., Lancet 379(9819):895-904, 2012; Ishigami et al., Circ Res 120(7):1162-1173, 2017; Ishigami et al., Circ Res 116 (4):653-664, 2015; Tarui et al., J Thorac Cardiovasc Surg 150(5):1198-1207, 1208 e1191-1192, 2015). In this context and in view of clinical applications, cells have to be prepared and released according to Good Manufacturing Practices (GMP) (EudraLex-volume 4-good manufacturing practice (GMP) guidelines-Part I-basic requirements for medicinal products. http://ec.europa.eu/health/documents/eudralex/vol-4 ; EudraLex-volume 4-good manufacturing practice (GMP) guidelines-Part IV-guidelines on good manufacturing practices specific to advanced therapy medicinal products. http://ec.europa.eu/health/documents/eudralex/vol-4 ). This chapter describes GMP-grade methods for production and testing of a CPC Master Cell Bank (MCB), consisting of frozen aliquots of cells that may be used either as a therapeutic product or as source for the manufacturing of Exo for clinical trials.The MCB production method has been designed to isolate and expand CPC from human cardiac tissue in xeno-free conditions (Andriolo et al., Front Physiol 9:1169, 2018). The quality control (QC) methods have been implemented to assess the safety (sterility, endotoxin, mycoplasma, cell senescence, tumorigenicity) and identity/potency/purity (cell count and viability, RT-PCR, immunophenotype) of the cells (Andriolo et al., Front Physiol 9:1169, 2018).

Exosomes From Human Cardiac Progenitor Cells for Therapeutic Applications: Development of a GMP-Grade Manufacturing Method.

Exosomes, nanosized membrane vesicles secreted by cardiac progenitor cells (Exo-CPC), inhibit cardiomyocyte apoptosis under stress conditions, promote angiogenesis in vitro, and prevent the early decline in cardiac function after myocardial infarction in vivo in preclinical rat models. The recognition of exosome-mediated effects has moved attempts at developing cell-free approaches for cardiac repair. Such approaches offer major advantages including the fact that exosomes can be stored as ready-to-use agents and delivered to patients with acute coronary syndromes. The aim of the present work was the development of a good manufacturing practice (GMP)-grade method for the large-scale preparation of Exo-CPC as a medicinal product, for a future clinical translation. A GMP-compliant manufacturing method was set up, based on large-scale cell culture in xeno-free conditions, collection of up to 8 l of exosome-containing conditioned medium and isolation of Exo-CPC through tangential flow filtration. Quality control tests were developed and carried out to evaluate safety, identity, and potency of both cardiac progenitor cells (CPC) as cell source and Exo-CPC as final product (GMP-Exo-CPC). CPC, cultured in xeno-free conditions, showed a lower doubling-time than observed in research-grade condition, while producing exosomes with similar features. Cells showed the typical phenotype of mesenchymal progenitor cells (CD73/CD90/CD105 positive, CD14/CD20/CD34/CD45/HLA-DR negative), and expressed mesodermal (TBX5/TBX18) and cardiac-specific (GATA4/MESP1) transcription factors. Purified GMP-Exo-CPC showed the typical nanoparticle tracking analysis profile and expressed main exosome markers (CD9/CD63/CD81/TSG101). The GMP manufacturing method guaranteed high exosome yield (>1013 particles) and consistent removal (≥97%) of contaminating proteins. The resulting GMP-Exo-CPC were tested for safety, purity, identity, and potency in vitro, showing functional anti-apoptotic and pro-angiogenic activity. The therapeutic efficacy was validated in vivo in rats, where GMP-Exo-CPC ameliorated heart function after myocardial infarction. Our standardized production method and testing strategy for large-scale manufacturing of GMP-Exo-CPC open new perspectives for reliable human therapeutic applications for acute myocardial infarction syndrome and can be easily applied to other cell sources for different therapeutic areas.

Effect of Bone Marrow-Derived Mononuclear Cell Treatment, Early or Late After Acute Myocardial Infarction: Twelve Months CMR and Long-Term Clinical Results.

RATIONALE: Intracoronary delivery of autologous bone marrow-derived mononuclear cells (BM-MNC) may improve remodeling of the left ventricle (LV) after acute myocardial infarction (AMI). OBJECTIVE: To demonstrate long-term efficacy of BM-MNC treatment after AMI. METHODS AND RESULTS: In a multicenter study, we randomized 200 patients with large AMI in a 1:1:1 pattern into an open-labeled control and 2 BM-MNC treatment groups. In the BM-MNC groups, cells were either administered 5 to 7 days (early) or 3 to 4 weeks (late) after AMI. Cardiac magnetic resonance imaging was performed at baseline and after 12 months. The current analysis investigates the change from baseline to 12 months in global LV ejection fraction, LV volumes, scar size, and N-terminal pro-brain natriuretic peptide values comparing the 2 treatment groups with control in a linear regression model. Besides the complete case analysis, multiple imputation analysis was performed to address for missing data. Furthermore, the long-term clinical event rate was computed. The absolute change in LV ejection fraction from baseline to 12 months was -1.9±9.8% for control (mean±SD), -0.9±10.5% for the early treatment group, and -0.7±10.1% for the late treatment group. The difference between the groups was not significant, both for complete case analysis and multiple imputation analysis. A combined clinical end point occurred equally in all the groups. Overall, 1-year mortality was low (2.25%). CONCLUSIONS: Among patients with AMI and LV dysfunction, treatment with BM-MNC either 5 to 7 days or 3 to 4 weeks after AMI did not improve LV function at 12 months, compared with control. The results are limited by an important drop out rate. CLINICAL TRIAL REGISTRATION INFORMATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00355186.

Quality Control Assays for Clinical-Grade Human Mesenchymal Stromal Cells: Methods for ATMP Release.

Mesenchymal stromal/stem cells (MSC) are promising candidates for the development of cell-based therapies for various diseases and are currently being evaluated in a number of clinical trials (Sharma et al., Transfusion 54:1418-1437, 2014; Ikebe and Suzuki, Biomed Res Int 2014:951512, 2014). MSC for therapeutic applications are classified as advanced therapy medicinal products (ATMP) (Regulation (EC) No 1394/2007 of the European Parliament and of the Council of 13 November 2007 on advanced therapy medicinal products and amending Directive 2001/83/EC and Regulation (EC) No 726/2004) and must be prepared according to good manufacturing practices ( http://ec.europa.eu/health/documents/eudralex/vol-4 ). They may be derived from different starting materials (mainly bone marrow (BM), adipose tissue, or cord blood) and applied as fresh or cryopreserved products, in the autologous as well as an allogeneic context (Sharma et al., Transfusion 54:1418-1437, 2014; Ikebe and Suzuki, Biomed Res Int 2014:951512, 2014; Sensebé and Bourin, Transplantation 87(9 Suppl):S49-S53, 2009). In any case, they require an approved and well-defined panel of assays in order to be released for clinical use.This chapter describes analytical methods implemented and performed in our cell factory as part of the release strategy for an ATMP consisting of frozen autologous BM-derived MSC. Such methods are designed to assess the safety (sterility, endotoxin, and mycoplasma assays) and identity/potency (cell count and viability, immunophenotype and clonogenic assay) of the final product. Some assays are also applied to the biological starting material (sterility) or carried out as in-process controls (sterility, cell count and viability, immunophenotype, clonogenic assay).The validation strategy for each analytical method is described in the accompanying Chapter 20 .

Quality Control Assays for Clinical-Grade Human Mesenchymal Stromal Cells: Validation Strategy.

The present chapter focuses on the validation of the following analytical methods for the control of mesenchymal stromal cells (MSC) for cell therapy clinical trials: Microbiological control for cellular product Endotoxin assay Mycoplasma assay Cell count and viability Immunophenotype Clonogenic potential (CFU-F assay) In our lab, these methods are in use for product release, process control or control of the biological starting materials. They are described in detail in the accompanying Chapter 19.For each method, validation goals and strategy are presented, and a detailed experimental scheme is proposed.

Bone marrow-derived cells for cardiovascular cell therapy: an optimized GMP method based on low-density gradient improves cell purity and function.

BACKGROUND: Cardiovascular cell therapy represents a promising field, with several approaches currently being tested. The advanced therapy medicinal product (ATMP) for the ongoing METHOD clinical study ("Bone marrow derived cell therapy in the stable phase of chronic ischemic heart disease") consists of fresh mononuclear cells (MNC) isolated from autologous bone marrow (BM) through density gradient centrifugation on standard Ficoll-Paque. Cells are tested for safety (sterility, endotoxin), identity/potency (cell count, CD45/CD34/CD133, viability) and purity (contaminant granulocytes and platelets). METHODS: BM-MNC were isolated by density gradient centrifugation on Ficoll-Paque. The following process parameters were optimized throughout the study: gradient medium density; gradient centrifugation speed and duration; washing conditions. RESULTS: A new manufacturing method was set up, based on gradient centrifugation on low density Ficoll-Paque, followed by 2 washing steps, of which the second one at low speed. It led to significantly higher removal of contaminant granulocytes and platelets, improving product purity; the frequencies of CD34+ cells, CD133+ cells and functional hematopoietic and mesenchymal precursors were significantly increased. CONCLUSIONS: The methodological optimization described here resulted in a significant improvement of ATMP quality, a crucial issue to clinical applications in cardiovascular cell therapy.

Combined delivery of bone marrow-derived mononuclear cells in chronic ischemic heart disease: rationale and study design.

BACKGROUND: Treatment with bone marrow-derived mononuclear cells (BM-MNC) may improve left ventricular (LV) function in patients with chronic ischemic heart disease (IHD). Delivery method of the cell product may be crucial for efficacy. HYPOTHESIS: We aimed to demonstrate that the combination of intramyocardial and intracoronary injection of BM-MNC is safe and improves LV function in patients with chronic IHD. METHODS: After a safety/feasibility phase of 10 patients, 54 patients will be randomly assigned in a 1:1:1 pattern to 1 control and 2 BM-MNC treatment groups. The control group will be treated with state-of-the-art medical management. The treatment groups will receive either exclusively intramyocardial injection or a combination of intramyocardial and intracoronary injection of autologous BM-MNC. Left ventricular function as well as scar size, transmural extension, and regional wall-motion score will be assessed by cardiac magnetic resonance imaging studies at baseline and after 6 months. The primary endpoint is the change in global LV ejection fraction by cardiac magnetic resonance from 6 months to baseline. RESULTS: The results, it is hoped, will have important clinical impact and provide essential information to improve the design of future regenerative-medicine protocols in cardiology. CONCLUSIONS: As cell delivery may play an important role in chronic IHD, we aim to demonstrate feasibility and efficacy of a combined cell-delivery approach in patients with decreased LV function.

Intracoronary injection of bone marrow-derived mononuclear cells early or late after acute myocardial infarction: effects on global left ventricular function.

BACKGROUND: Intracoronary administration of autologous bone marrow-derived mononuclear cells (BM-MNC) may improve remodeling of the left ventricle (LV) after acute myocardial infarction. The optimal time point of administration of BM-MNC is still uncertain and has rarely been addressed prospectively in randomized clinical trials. METHODS AND RESULTS: In a multicenter study, we randomized 200 patients with large, successfully reperfused ST-segment elevation myocardial infarction in a 1:1:1 pattern into an open-labeled control and 2 BM-MNC treatment groups. In the BM-MNC groups, cells were administered either early (i.e., 5 to 7 days) or late (i.e., 3 to 4 weeks) after acute myocardial infarction. Cardiac magnetic resonance imaging was performed at baseline and after 4 months. The primary end point was the change from baseline to 4 months in global LV ejection fraction between the 2 treatment groups and the control group. The absolute change in LV ejection fraction from baseline to 4 months was -0.4±8.8% (mean±SD; P=0.74 versus baseline) in the control group, 1.8±8.4% (P=0.12 versus baseline) in the early group, and 0.8±7.6% (P=0.45 versus baseline) in the late group. The treatment effect of BM-MNC as estimated by ANCOVA was 1.25 (95% confidence interval, -1.83 to 4.32; P=0.42) for the early therapy group and 0.55 (95% confidence interval, -2.61 to 3.71; P=0.73) for the late therapy group. CONCLUSIONS: Among patients with ST-segment elevation myocardial infarction and LV dysfunction after successful reperfusion, intracoronary infusion of BM-MNC at either 5 to 7 days or 3 to 4 weeks after acute myocardial infarction did not improve LV function at 4-month follow-up. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00355186.

Bone marrow derived stem cells in regenerative medicine as advanced therapy medicinal products.

Bone marrow derived stem cells administered after minimal manipulation represent an important cell source for cell-based therapies. Clinical trial results, have revealed both safety and efficacy of the cell reinfusion procedure in many cardiovascular diseases. Many of these early clinical trials were performed in a period before the entry into force of the US and European regulation on cell-based therapies. As a result, conflicting data have been generated on the effectiveness of those therapies in certain conditions as acute myocardial infarction. As more academic medical centers and private companies move toward exploiting the full potential of cell-based medicinal products, needs arise for the development of the infrastructure necessary to support these investigations. This review describes the regulatory environment surrounding the production of cell based medicinal products and give practical aspects for cell isolation, characterization, production following Good Manufacturing Practice, focusing on the activities associated with the investigational new drug development.

Cell-based therapy for myocardial repair in patients with acute myocardial infarction: rationale and study design of the SWiss multicenter Intracoronary Stem cells Study in Acute Myocardial Infarction (SWISS-AMI).

BACKGROUND: Recent studies report that intracoronary administration of autologous bone marrow mononucleated cells (BM-MNCs) may improve remodeling of the left ventricle after acute myocardial infarction (AMI). Subgroup analysis suggest that early treatment between days 4 and 7 after AMI is probably most effective; however, the optimal time point of intracoronary cell administration has never been addressed in clinical trials. Furthermore, reliable clinical predictors are lacking for identifying patients who are thought to have most benefit from cellular therapy. STUDY DESIGN: In a multicenter trial, 192 patients with AMI successfully treated by percutaneous coronary intervention (PCI) of the infarct-related artery will be randomized in a 1:1:1 pattern to 1 control and 2 BM-MNC treatment groups. The control group will be treated with state-of-the-art medical management. The treatment groups will receive intracoronary administration of autologous BM-MNC at 5 to 7 days or 3 to 4 weeks after the initial event, respectively. Left ventricular function as well as scar size, transmural extension, and regional wall motion score will be assessed by cardiac magnetic resonance (CMR) studies at baseline and after 4 and 12 months. METHODS: Fifty milliliters of bone marrow will be harvested by aspiration from the iliac crest and then carried by courier to a centralized cell processing facility. The mononucleated cell fraction will be isolated by density gradient centrifugation, washed, and resuspended in 10 mL of injection medium. The cells will be characterized by fluorescence-activated cell sorting analysis and tested for sterility and potency both "in vitro" and "in vivo." Bone marrow MNC will then be reinfused directly in the infarct-related coronary artery. END POINTS: The primary end point is the change in global left ventricular (LV) ejection fraction by CMR at 4 months as compared to baseline. Comparisons will then be made between each of the prespecified therapy subgroups (early and late after AMI) and the control group. Secondary end points include change in infarct size, change in regional myocardial thickness, and wall motion at 4 and 12 months compared to baseline. Infarct extension (size and transmural extension), time delay to PCI, and coronary flow characteristics after PCI will be assessed as potential predictors of LV remodeling and change after cell therapy. Major adverse cardiac events (MACE) (death, myocardial infarction, coronary revascularization, rehospitalization for heart failure) will be assessed at 4, 12, and 24 months and time to MACE will be estimated. DISCUSSION: With the present study, we aim to determine the optimal time point of intracoronary administration of autologous BM-MNC after AMI on LV remodeling.

A practical approach for the validation of sterility, endotoxin and potency testing of bone marrow mononucleated cells used in cardiac regeneration in compliance with good manufacturing practice.

BACKGROUND: Main scope of the EU and FDA regulations is to establish a classification criterion for advanced therapy medicinal products (ATMP). Regulations require that ATMPs must be prepared under good manufacturing practice (GMP). We have validated a commercial system for the determination of bacterial endotoxins in compliance with EU Pharmacopoeia 2.6.14, the sterility testing in compliance with EU Pharmacopoeia 2.6.1 and a potency assay in an ATMP constituted of mononucleated cells used in cardiac regeneration. METHODS: For the potency assay, cells were placed in the upper part of a modified Boyden chamber containing Endocult Basal Medium with supplements and transmigrated cells were scored. The invasion index was expressed as the ratio between the numbers of invading cells relative to cell migration through a control insert membrane. For endotoxins, we used a commercially available system based on the kinetic chromogenic LAL-test. Validation of sterility was performed by direct inoculation of TSB and FTM media with the cell product following Eu Ph 2.6.1 guideline. RESULTS AND DISCUSSION: The calculated MVD and endotoxin limit were 780x and 39 EU/ml respectively. The 1:10 and 1:100 dilutions were selected for the validation. For sterility, all the FTM cultures were positive after 3 days. For TSB cultures, Mycetes and B. subtilis were positive after 5 and 3 days respectively. The detection limit was 1-10 colonies. A total of four invasion assay were performed: the calculated invasion index was 28.89 +/- 16.82% (mean +/- SD). CONCLUSION: We have validated a strategy for endotoxin, sterility and potency testing in an ATMP used in cardiac regeneration. Unlike pharmaceutical products, many stem-cell-based products may originate in hospitals where personnel are unfamiliar with the applicable regulations. As new ATMPs are developed, the regulatory framework is likely to evolve. Meanwhile, existing regulations provide an appropriate structure for ensuring the safety and efficacy of the next generation of ATMPs. Personnel must be adequately trained on relevant methods and their application to stem-cell-based products.