Short-term assays for mesenchymal stromal cell immunosuppression of T-lymphocytes

Introduction

Trauma patients are susceptible to coagulopathy and dysfunctional immune responses. Mesenchymal stromal cells (MSCs) are at the forefront of the cellular therapy revolution with profound immunomodulatory, regenerative, and therapeutic potential. Routine assays to assess immunomodulation activity examine MSC effects on proliferation of peripheral blood mononuclear cells (PBMCs) and take 3-7 days. Assays that could be done in a shorter period of time would be beneficial to allow more rapid comparison of different MSC donors. The studies presented here focused on assays for MSC suppression of mitogen-stimulated PBMC activation in time frames of 24 h or less.

Methods

Three potential assays were examined-assays of apoptosis focusing on caspase activation, assays of phosphatidyl serine externalization (PS+) on PBMCs, and measurement of tumor necrosis factor alpha (TNFα) levels using rapid ELISA methods. All assays used the same initial experimental conditions: cryopreserved PBMCs from 8 to 10 pooled donors, co-culture with and without MSCs in 96-well plates, and PBMC stimulation with mitogen for 2-72 h.

Results

Suppression of caspase activity in activated PBMCs by incubation with MSCs was not robust and was only significant at times after 24 h. Monitoring PS+ of live CD3+ or live CD4+/CD3+ mitogen-activated PBMCs was dose dependent, reproducible, robust, and evident at the earliest time point taken, 2 h, although no increase in the percentage of PS+ cells was seen with time. The ability of MSC in co-culture to suppress PBMC PS+ externalization compared favorably to two concomitant assays for MSC co-culture suppression of PBMC proliferation, at 72 h by ATP assay, or at 96 h by fluorescently labeled protein signal dilution. TNFα release by mitogen-activated PBMCs was dose dependent, reproducible, robust, and evident at the earliest time point taken, with accumulating signal over time. However, suppression levels with MSC co-culture was reliably seen only after 24 h.

Discussion

Takeaways from these studies are as follows: (1) while early measures of PBMC activation is evident at 2-6 h, immunosuppression was only reliably detected at 24 h; (2) PS externalization at 24 h is a surrogate assay for MSC immunomodulation; and (3) rapid ELISA assay detection of TNFα release by PBMCs is a robust and sensitive assay for MSC immunomodulation at 24 h.

Pooled human bone marrow-derived mesenchymal stromal cells with defined trophic factors cargo promote dermal wound healing in diabetic rats by improved vascularization and dynamic recruitment of M2-like macrophages

Human Mesenchymal Stromal Cells (hMSCs) are a promising source for cell-based therapies. Yet, transition to phase III and IV clinical trials is remarkably slow. To mitigate donor variabilities and to obtain robust and valid clinical data, we aimed first to develop a manufacturing concept balancing large-scale production of pooled hMSCs in a minimal expansion period, and second to test them for key manufacture and efficacy indicators in the clinically highly relevant indication wound healing. Our novel clinical-scale manufacturing concept is comprised of six single donor hMSCs master cell banks that are pooled to a working cell bank from which an extrapolated number of 70,000 clinical doses of 1x10⁶ hMSCs/cm² wound size can be manufactured within only three passages. The pooled hMSC batches showed high stability of key manufacture indicators such as morphology, immune phenotype, proliferation, scratch wound healing, chemotactic migration and angiogenic support. Repeated topical hMSCs administration significantly accelerated the wound healing in a diabetic rat model by delivering a defined growth factor cargo (specifically BDNF, EGF, G-CSF, HGF, IL-1α, IL-6, LIF, osteopontin, VEGF-A, FGF-2, TGF-β, PGE-2 and IDO after priming) at the specific stages of wound repair, namely inflammation, proliferation and remodeling. Specifically, the hMSCs mediated epidermal and dermal maturation and collagen formation, improved vascularization, and promoted cell infiltration. Kinetic analyses revealed transient presence of hMSCs until day (d)4, and the dynamic recruitment of macrophages infiltrating from the wound edges (d3) and basis (d9), eventually progressing to the apical wound on d11. In the wounds, the hMSCs mediated M2-like macrophage polarization starting at d4, peaking at d9 and then decreasing to d11. Our study establishes a standardized, scalable and pooled hMSC therapeutic, delivering a defined cargo of trophic factors, which is efficacious in diabetic wound healing by improving vascularization and dynamic recruitment of M2-like macrophages. This decision-making study now enables the validation of pooled hMSCs as treatment for impaired wound healing in large randomized clinical trials.

Mesenchymal (Stem) Stromal Cells Based as New Therapeutic Alternative in Inflammatory Bowel Disease: Basic Mechanisms, Experimental and Clinical Evidence, and Challenges

Inflammatory bowel diseases (IBD) are an example of chronic diseases affecting 40% of the population, which involved tissue damage and an inflammatory process not satisfactorily controlled with current therapies. Data suggest that mesenchymal stem cells (MSC) may be a therapeutic option for these processes, and especially for IBD, due to their multifactorial approaches such as anti-inflammatory, anti-oxidative stress, anti-apoptotic, anti-fibrotic, regenerative, angiogenic, anti-tumor, or anti-microbial. However, MSC therapy is associated with important limitations as safety issues, handling difficulties for therapeutic purposes, and high economic cost. MSC-derived secretome products (conditioned medium or extracellular vesicles) are therefore a therapeutic option in IBD as they exhibit similar effects to their parent cells and avoid the issues of cell therapy. In this review, we proposed further studies to choose the ideal tissue source of MSC to treat IBD, the implementation of new standardized production strategies, quality controls and the integration of other technologies, such as hydrogels, which may improve the therapeutic effects of derived-MSC secretome products in IBD.

Autologous Infusion of Bone Marrow and Mesenchymal Stromal Cells in Patients with Chronic Obstructive Pulmonary Disease: Phase I Randomized Clinical Trial

Background and Objectives

Chronic obstructive pulmonary disease (COPD) is characterized by the destruction of alveolar walls, chronic inflammation and persistent respiratory symptoms. There is no curative clinical treatment for COPD. In this context, cell-based therapy is a promising therapeutic alternative for COPD. Thus, in this open, controlled and randomized Phase I Clinical Trial, we aimed to assess the safety of the infusion of autologous bone marrow mononuclear cells (BMMC), adipose-derived mesenchymal stromal cells (ADSC) and, especially, the safety of concomitant infusion (co-infusion) of BMMC and ADSC as a new therapeutic alternative for COPD. The rationale for co-infusion of BMMC and ADSC is based on the hypothesis of an additive or synergistic therapeutic effect resulting from this association.

Methods

To achieve the proposed objectives, twenty patients with moderate-to-severe COPD were randomly divided into four groups: control group - patients receiving conventional treatment; BMMC group - patients receiving only BMMC; ADSC group - patients receiving only ADSC, and co-infusion group - patients receiving the concomitant infusion of BMMC and ADSC. Patients were assessed for pulmonary function, biochemical profile, and quality of life over a 12 months follow-up.

Results

No adverse events were detected immediately after the infusion of BMMC, ADSC or co-infusion. In the 12-month follow-up, no causal relationship was established between adverse events and cell therapy procedures. Regarding the efficacy, the BMMC group showed an increase in forced expiratory volume (FEV1) and diffusing capacity for carbon monoxide (DLCO). Co-infusion group showed a DLCO, and gas exchange improvement and a better quality of life.

Conclusion

The results obtained allow us to conclude that cell-based therapy with co-infusion of BMMC and ADSC is a safe procedure and a promising therapeutic for COPD. However, additional studies with a greater number of patients are needed before randomized and controlled Phase III clinical trials can be implemented.

Mesenchymal Stem Cells as a Cornerstone in a Galaxy of Intercellular Signals: Basis for a New Era of Medicine

Around 40% of the population will suffer at some point in their life a disease involving tissue loss or an inflammatory or autoimmune process that cannot be satisfactorily controlled with current therapies. An alternative for these processes is represented by stem cells and, especially, mesenchymal stem cells (MSC). Numerous preclinical studies have shown MSC to have therapeutic effects in different clinical conditions, probably due to their mesodermal origin. Thereby, MSC appear to play a central role in the control of a galaxy of intercellular signals of anti-inflammatory, regenerative, angiogenic, anti-fibrotic, anti-oxidative stress effects of anti-apoptotic, anti-tumor, or anti-microbial type. This concept forces us to return to the origin of natural physiological processes as a starting point to understand the evolution of MSC therapy in the field of regenerative medicine. These biological effects, demonstrated in countless preclinical studies, justify their first clinical applications, and draw a horizon of new therapeutic strategies. However, several limitations of MSC as cell therapy are recognized, such as safety issues, handling difficulties for therapeutic purposes, and high economic cost. For these reasons, there is an ongoing tendency to consider the use of MSC-derived secretome products as a therapeutic tool, since they reproduce the effects of their parent cells. However, it will be necessary to resolve key aspects, such as the choice of the ideal type of MSC according to their origin for each therapeutic indication and the implementation of new standardized production strategies. Therefore, stem cell science based on an intelligently designed production of MSC and or their derivative products will be able to advance towards an innovative and more personalized medical biotechnology.

More Human BM-MSC With Similar Subpopulation Composition and Functional Characteristics Can Be Produced With a GMP-Compatible Fabric Filter System Compared to Density Gradient Technique

Background

Mesenchymal stromal cells (MSCs), multipotent progenitors that can be isolated from a variety of different tissues, are becoming increasingly important as cell therapeutics targeting immunopathologies and tissue regeneration. Current protocols for MSC isolation from bone marrow (BM) rely on density gradient centrifugation (DGC), and the production of sufficient MSC doses is a critical factor for conducting clinical MSC trials. Previously, a Good Manufacturing Practice (GMP)–compatible non-woven fabric filter device system to isolate MSCs was developed to increase the MSC yield from the BM. The aim of our study was to compare high-resolution phenotypic and functional characteristics of BM-MSCs isolated with this device and with standard DGC technology.

Methods

Human BM samples from 5 donors were analyzed. Each sample was divided equally, processing by DGC, and with the filter device. Stem cell content was assessed by quantification of colony-forming units fibroblasts (CFU-F). Immunophenotype was analyzed by multicolor flow cytometry. In vitro trilineage differentiation potential, trophic factors, and IDO-1 production were assessed. Functionally, immunomodulatory potential, wound healing, and angiogenesis were assayed in vitro.

Results

The CFU-F yield was 15-fold higher in the MSC preparations isolated with the device compared to those isolated by DGC. Consequently, the MSC yield that could be manufactured at passage 3 per mL collected BM was more than 10 times higher in the device group compared to DGC (1.65 × 10⁹ vs. 1.45 × 10⁸). The immunomodulatory potential and IDO-1 production showed donor-to-donor variabilities without differences between fabric filter-isolated and DGC-isolated MSCs. The results from the wound closure assays, the tube formation assays, and the trilineage differentiation assays were similar between the groups with respect to the isolation method. Sixty-four MSC subpopulations could be quantified with CD140a⁺CD119⁺CD146⁺ as most common phenotype group, and CD140a⁺CD119⁺CD146⁺MSCA-1^–CD106^–CD271^– and CD140a⁺CD119⁺CD146^–MSCA-1^–CD106^–CD271^– as most frequent MSC subpopulations. As trophic factors hepatocyte growth factor, epidermal growth factor, brain-derived neurotrophic factor, angiopoietin-1, and vascular endothelial growth factor A could be detected in both groups with considerable variability between donors, but independent of the respective MSC isolation technique.

Conclusion

The isolation of MSCs using a GMP-compatible fabric filter system device resulted in higher yield of CFU-F, producing substantially more MSCs with similar subpopulation composition and functional characteristics as MSCs isolated by DGC.

Neglected No More: Emerging Cellular Therapies in Traumatic Injury

Traumatic injuries are a leading cause of death and disability in both military and civilian populations. Given the complexity and diversity of traumatic injuries, novel and individualized treatment strategies are required to optimize outcomes. Cellular therapies have potential benefit for the treatment of acute or chronic injuries, and various cell-based pharmaceuticals are currently being tested in preclinical studies or in clinical trials. Cellular therapeutics may have the ability to complement existing therapies, especially in restoring organ function lost due to tissue disruption, prolonged hypoxia or inflammatory damage. In this article we highlight the current status and discuss future directions of cellular therapies for the treatment of traumatic injury. Both published research and ongoing clinical trials are discussed here.

Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have attracted great interest in the field of regenerative medicine. They can home to damaged tissue, where they can exert pro-regenerative and anti-inflammatory properties. These therapeutic effects involve the secretion of growth factors, cytokines, and chemokines. Moreover, the functions of MSCs could be mediated by extracellular vesicles (EVs) that shuttle various signaling messengers. Although preclinical studies and clinical trials have demonstrated promising therapeutic results, the efficiency and the safety of MSCs need to be improved. After transplantation, MSCs face harsh environmental conditions, which likely dampen their therapeutic efficacy. A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed. The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment. In this review, we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs. As stated above, EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation. As a result, this novel type of cell-free therapy may be safer and more efficient than the whole cell product. We will, therefore, also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs.

Improving Stem Cell Clinical Trial Design and Conduct: Development of a Quality Assessment Tool for Stem Cell Clinical Trials

Background

Clinical trials are at the cornerstone of evidence-based stem cell therapies, but the quality assessment for designing and conduct these sometimes-complex studies are scarce of evidence. This study is aimed at developing a handy quality assessment tool for stem cell clinical trials, enhancing capacity of the self-regulate overall quality, and participating protection.

Methods

The framework of quality assessment tool was based on the PQRS (progress-quality-regulation-scientific) quality assessment tool, and detailed quality indicators were developed by leader group discussion, expert consulting, and literature review. Stem cell clinical trials were retrieved from the International Clinical Trials Registry Platform, and corresponding quality indicators were assessed and extracted. The validity and feasibility of conceptual quality assessment tool were further evaluated by using structural equation modeling.

Results

The quality assessment tool for stem cell clinical trials contains four critical quality attributes, including participant protection, scientific value, quality control, and stem cell products, and 9 observed quality indicators. From 11 primary clinical trial registries in the International Clinical Trials Registry Platform, 9410 stem cell trial registrations were identified, and 1036 studies were eligible for publications and protocols screening. After reviewed full text, 37 studies were included in the validity and feasibility evaluation: 32 studies were completed, and 3 studies terminated early. Most of the studies (83.79%) were in the early phase, and 63.16% of the studies were investigator-initiated trial. To further tested for validity, the critical quality attributes and quality indicators (QIs) between expertise further validated by the SEM method, which showed a good fit for the model (chi − square = 26.008; P = 0.353; TLI = 0.967; CFI = 0.978; RMSEA = 0.048). Compared with exploratory trials, evaluating using the quality assessment tool, confirmatory trials performed similarly in participant protection, scientific value, and quality control, but lower in stem cell products.

Conclusions

The results of critical quality attributes and quality indicators between expertise and confirmatory validation analysis are basically consistent, indicating the feasibility and validity of applying this quality assessment tool for overall quality evaluation of stem cell trials.

Human Mesenchymal Stromal Cell (MSC) Characteristics Vary Among Laboratories When Manufactured From the Same Source Material: A Report by the Cellular Therapy Team of the Biomedical Excellence for Safer Transfusion (BEST) Collaborative

Background

Culture-derived mesenchymal stromal cells (MSCs) exhibit variable characteristics when manufactured using different methods and different source materials. The purpose of this study was to assess the impact on MSC characteristics when different laboratories propagated MSCs from cultures initiated with BM aliquots derived from the same donor source material.

Methods and Methods

Five aliquots from each of three different BM donors were distributed to five independent laboratories. Three laboratories plated whole BM and two laboratories a mononuclear BM cell fraction. Four laboratories cultured in media supplemented with fetal bovine serum (FBS) and one laboratory used human platelet lysate (hPL). Initial cell seeding densities (i.e., P0) ranged from 19.7 × 10³/cm²–282 × 10³/cm² and for second seeding (i.e., P1) 0.05 × 10³–5.1 × 10³ cells/cm². Post-thawed MSCs from each laboratory were analyzed for cell viability, immunophenotype, tri-lineage differentiation, fibroblast colony-forming units (CFU-F), gene expression, and immunosuppressive activity.

Results

Transit times from BM collection to receipt by laboratories located in the United States ranged from 16.0–30.0 h and from 41.5–71.5 h for a laboratory in Asia. Post-thaw culture derived MSCs rom BM #1, #2, and #3 exhibited viabilities that ranged from 74–92%, 61–96%, and 23–90%, respectively. CFU activity from BM #1, #2, and #3 per 200 MSCs plated averaged 45.1 ± 21.4, 49.3 ± 26.8 and 14.9 ± 13.3, respectively. No substantial differences were observed in immunophenotype, and immunosuppressive activities. Global gene expression profiles of MSCs revealed transcriptome differences due to different inter-laboratory methods and to donor source material with the center effects showing greater molecular differences than source material.

Conclusion

Functional and molecular differences exist among MSCs produced by different centers even when the same BM starting material is used to initiate cultures. These results indicated that manufacturing of MSCs by five independent centers contributed more to MSC variability than did the source material of the BM used in this study. Thus, emphasizing the importance of establishing worldwide standards to propagate MSCs for clinical use.

Fibrous Dysplasia/McCune-Albright Syndrome: A Rare, Mosaic Disease of Gα s Activation

Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) is a rare disorder of striking complexity. It arises from somatic, gain-of-function mutations in GNAS, leading to mosaic Gα s activation and inappropriate production of intracellular cyclic adenosine monophosphate (cAMP). The clinical phenotype is largely determined by the location and extent of affected tissues, and the pathophysiological effects of Gα s activation within these tissues. In bone, Gα s activation results in impaired differentiation of skeletal stem cells, leading to discrete skeletal lesions prone to fracture, deformity, and pain. Extraskeletal manifestations include a variable combination of hyperpigmented macules and hyperfunctioning endocrinopathies. Distinctive age-related changes in disease development has key effects on histologic, radiographic, and clinical features. FD/MAS thus presents along a uniquely broad clinical spectrum, and the resulting challenges in diagnosis and management can be difficult for clinicians. This review presents FD/MAS in the context of a mosaic disorder of Gα s activation, providing an intellectual framework within which to understand, evaluate, and treat this interesting disease. It includes a comprehensive summary of current understanding of FD/MAS pathogenesis, and a detailed discussion of clinical presentation and management. Critical areas of unmet need are highlighted, including discussion of key challenges and potential solutions to advance research and clinical care in FD/MAS.

Recent advances in understanding mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are among of the most studied cell type for cellular therapy thanks to the ease of isolation, cultivation, and the high ex vivo expansion potential. In 2018, the European Medicines Agency finally granted the first marketing authorization for an MSC product. Despite the numerous promising results in preclinical studies, translation into routine practice still lags behind: therapeutic benefits of MSCs are not as satisfactory in clinical trial settings as they appear to be in preclinical models. The bench-to-bedside-and-back approach and careful evaluation of discrepancies between preclinical and clinical results have provided valuable insights into critical components of MSC manufacturing, their mechanisms of action, and how to evaluate and quality-control them. We sum up these past developments in the introductory section (“Mesenchymal stromal cells: name follows function”). From the huge amount of information, we then selected a few examples to illustrate challenges and opportunities to improve MSCs for clinical purposes. These include tissue origin of MSCs, MSC culture conditions, immune compatibility, and route of application and dosing. Finally, we add some information on MSC mechanisms of action and translation into potency assays and give an outlook on future perspectives raising the question of whether the future clinical product may be cell-based or cell-derived.

Use of Multipotent Mesenchymal Stromal Cells, Fibrin, and Scaffolds in the Production of Clinical Grade Bone Tissue Engineering Products

Tissue engineering products (TEP) are a new type of medicines resulting from the combination of cells, scaffolds, and/or signalling factors, which can be used for the regeneration of damaged tissues thus opening new avenues for the treatment of complex conditions. However, such combination of biologically active elements, particularly living cells, poses an unprecedented challenge for their production under pharmaceutical standards.In the methods presented here, we formulated two types of TEP based on the use of multipotent mesenchymal stromal cells with osteogenic potential combined with osteoinductive and osteoconductive bony particles from tissue bank embedded in a fibrin hydrogel that, altogether, can induce the generation of new tissue while adapting to the diverse architecture of bony defects. In agreement with pharmaceutical quality and regulatory requirements, procedures presented herein can be performed in compliance with current good manufacturing practices and be readily implemented in straightforward facilities at hospitals and academic institutions.

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.

Compliance with Good Manufacturing Practice in the Assessment of Immunomodulation Potential of Clinical Grade Multipotent Mesenchymal Stromal Cells Derived from Wharton's Jelly

Background: The selection of assays suitable for testing the potency of clinical grade multipotent mesenchymal stromal cell (MSC)-based products and its interpretation is a challenge for both developers and regulators. Here, we present a bioprocess design for the production of Wharton’s jelly (WJ)-derived MSCs and a validated immunopotency assay approved by the competent regulatory authority for batch release together with the study of failure modes in the bioprocess with potential impact on critical quality attributes (CQA) of the final product. Methods: The lymphocyte proliferation assay was used for determining the immunopotency of WJ-MSCs and validated under good manufacturing practices (GMP). Moreover, failure mode effects analysis (FMEA) was used to identify and quantify the potential impact of different unexpected situations on the CQA. Results: A production process based on a two-tiered cell banking strategy resulted in batches with sufficient numbers of cells for clinical use in compliance with approved specifications including MSC identity (expressing CD73, CD90, CD105, but not CD31, CD45, or HLA-DR). Remarkably, all batches showed high capacity to inhibit the proliferation of activated lymphocytes. Moreover, implementation of risk management tools led to an in-depth understanding of the manufacturing process as well as the identification of weak points to be reinforced. Conclusions: The bioprocess design showed here together with detailed risk management and the use of a robust method for immunomodulation potency testing allowed for the robust production of clinical-grade WJ-MSCs under pharmaceutical standards.