Do cryopreserved mesenchymal stromal cells display impaired immunomodulatory and therapeutic properties?

Adipose-derived mesenchymal stromal cells in clinical trials: Insights from single-cell studies

Mesenchymal Stromal Cells (MSCs) offer tremendous potential for the treatment of various diseases and their healing properties have been explored in hundreds of clinical trials. These trails primarily focus on immunological and neurological disorders, as well as regenerative medicine. Adipose tissue is a rich source of mesenchymal stromal cells and methods to obtain and culture adipose-derived MSCs (AD-MSCs) have been well established. Promising results from pre-clinical testing of AD-MSCs activity prompted clinical trials that further led to the approval of AD-MSCs for the treatment of complex perianal fistulas in Crohn's disease and subcutaneous tissue defects. However, AD-MSC heterogeneity along with various manufacturing protocols or different strategies to boost their activity create the need for standardized quality control procedures and safety assessment of the intended cell product. High-resolution transcriptomic methods have been recently gaining attention, as they deliver insight into gene expression profiles of individual cells, helping to deconstruct cellular hierarchy and differentiation trajectories, and to understand cell-cell interactions within tissues. This article presents a comprehensive overview of completed clinical trials evaluating the safety and efficacy of AD-MSC treatment, together with current single-cell studies of human AD-MSC. Furthermore, our work emphasizes the increasing significance of single-cell research in elucidating the mechanisms of cellular action and predicting their therapeutic effects.

Mesenchymal stem cells biological and biotechnological advances: Implications for clinical applications

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem cells that are able to differentiate into multiple lineages including bone, cartilage, muscle and fat. They hold immunomodulatory properties and therapeutic ability to treat multiple diseases, including autoimmune and chronic degenerative diseases. In this article, we reviewed the different biological properties, applications and clinical trials of MSCs. Also, we discussed the basics of manufacturing conditions, quality control, and challenges facing MSCs in the clinical setting.

METHODS

Extensive review of the literature was conducted through the databases PubMed, Google Scholar, and Cochrane. Papers published since 2015 and covering the clinical applications and research of MSC therapy were considered. Furthermore, older papers were considered when referring to pioneering studies in the field.

RESULTS

The most widely studied stem cells in cell therapy and tissue repair are bone marrow-derived mesenchymal stem cells. Adipose tissue-derived stem cells became more common and to a lesser extent other stem cell sources e.g., foreskin derived MSCs. MSCs therapy were also studied in the setting of COVID-19 infections, ischemic strokes, autoimmune diseases, tumor development and graft rejection. Multiple obstacles, still face the standardization and optimization of MSC therapy such as the survival and the immunophenotype and the efficiency of transplanted cells. MSCs used in clinical settings displayed heterogeneity in their function despite their extraction from healthy donors and expression of similar surface markers.

CONCLUSION

Mesenchymal stem cells offer a rising therapeutic promise in various diseases. However, their potential use in clinical applications requires further investigation.

Utilization of Hydrogels in Mesenchymal Stem Cell-Based Therapy for Kidney Diseases

Kidney diseases are major global health problems, with high prevalence and mortality. However, current treatment strategies for kidney diseases fail to achieve satisfactory efficacy. Mesenchymal stem cell (MSC)-based therapy has been a promising strategy for treating kidney diseases. Preclinical studies have proven their safety and effectiveness in treating acute kidney injury (AKI) and chronic kidney disease (CKD), but the outcomes of clinical trials have shown very limited clinical efficacy. A variety of innovative approaches have been proposed to enhance the therapeutic potential of MSCs, and hydrogels are attractive candidates. Hydrogels are three-dimensional (3D) networks formed by hydrophilic polymers of natural or synthetic origin with diverse physical and chemical properties. They have been widely applied in the field of drug delivery and regenerative medicine, including MSC-based therapy. Many studies have proven that hydrogels can improve the therapeutic efficacy of MSCs for kidney diseases, but there are still challenges limiting the widespread application of this method. In this review, we introduce the application of MSCs in kidney diseases and the factors that influence therapeutic efficiency and focus on the beneficial effects of hydrogels in MSC-based therapy for AKI and CKD.

Research progress on optimization of in vitro isolation, cultivation and preservation methods of dental pulp stem cells for clinical application

Due to high proliferative capacity, multipotent differentiation, immunomodulatory abilities, and lack of ethical concerns, dental pulp stem cells (DPSCs) are promising candidates for clinical application. Currently, clinical research on DPSCs is in its early stages. The reason for the failure to obtain clinically effective results may be problems with the production process of DPSCs. Due to the different preparation methods and reagent formulations of DPSCs, cell characteristics may be affected and lead to inconsistent experimental results. Preparation of clinical-grade DPSCs is far from ready. To achieve clinical application, it is essential to transit the manufacturing of stem cells from laboratory grade to clinical grade. This review compares and analyzes experimental data on optimizing the preparation methods of DPSCs from extraction to resuscitation, including research articles, invention patents and clinical trials. The advantages and disadvantages of various methods and potential clinical applications are discussed, and factors that could improve the quality of DPSCs for clinical application are proposed. The aim is to summarize the current manufacture of DPSCs in the establishment of a standardized, reliable, safe, and economic method for future preparation of clinical-grade cell products.

Mesenchymal stromal cells for improvement of cardiac function following acute myocardial infarction: a matter of timing

Acute myocardial infarction (AMI) is the leading cause of cardiovascular death and remains the most common cause of heart failure. Reopening of the occluded artery, i.e., reperfusion, is the only way to save the myocardium. However, the expected benefits of reducing infarct size are disappointing due to the reperfusion paradox, which also induces specific cell death. These ischemia-reperfusion (I/R) lesions can account for up to 50% of final infarct size, a major determinant for both mortality and the risk of heart failure (morbidity). In this review, we provide a detailed description of the cell death and inflammation mechanisms as features of I/R injury and cardioprotective strategies such as ischemic postconditioning as well as their underlying mechanisms. Due to their biological properties, the use of mesenchymal stromal/stem cells (MSCs) has been considered a potential therapeutic approach in AMI. Despite promising results and evidence of safety in preclinical studies using MSCs, the effects reported in clinical trials are not conclusive and even inconsistent. These discrepancies were attributed to many parameters such as donor age, in vitro culture, and storage time as well as injection time window after AMI, which alter MSC therapeutic properties. In the context of AMI, future directions will be to generate MSCs with enhanced properties to limit cell death in myocardial tissue and thereby reduce infarct size and improve the healing phase to increase postinfarct myocardial performance.

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.

Freeze-Dried Mesenchymal Stem Cells: From Bench to Bedside. Review

This review describes the freeze-dried mesenchymal stem cells (MSCs) and their ability to restore damaged tissues and organs. An analysis of the literature shows that after the lyophilization MSCs retain >80% of paracrine factors and that the mechanism of their action on the restoration of damaged tissues and organs is similar to the mechanism of action of paracrine factors in fresh and cryopreserved mesenchymal stem cells. Based on the own materials, the use of paracrine factors of freeze-dried MSCs in vivo and in vitro for the treatment of various diseases of organs and tissues has shown to be effective. The study also discusses about the advantages and disadvantages of freeze-dried MSCs versus cryopreserved MSCs. However, for the effective use of freeze-dried MSCs in clinical practice, a more detailed study of the mechanism of interaction of paracrine factors of freeze-dried MSCs with target cells and tissues is required. It is also necessary to identify possible other specific paracrine factors of freeze-dried MSCs. In addition, develop new therapeutic strategies for the use of freeze-dried MSCs in regenerative medicine and tissue bioengineering.

Long-Term Cryopreservation May Cause Genomic Instability and the Premature Senescence of Cells

Cryopreservation is an essential step for utilizing various cell types for biological research and medical purposes. At the same time, there is a lack of data on the effect of cryopreservation, especially when prolonged, on the karyotype of cells. In the present work, we analyzed the genetic stability of cells subjected to a cryopreservation procedure. The objects were immortalized Chinese hamster lung fibroblasts (CHL V-79 RJK line) and human endometrial mesenchymal stem/stromal cells (eMSCs). We showed that short-term cryopreservation in liquid nitrogen for up to 6 months did not affect the karyotype stability of CHL V-79 RJK and eMSCs. On the contrary, karyotyping of G-banded metaphase chromosomes in cells underwent 10-year cryopreservation, which revealed genomic instability in both cell lines associated with the variability of chromosome number in cells, random chromosomal rearrangements, and condensation disorder in homologs. In addition, we found out that long-term cryopreservation of eMSCs does not affect the expression of their typical surface markers and morphology, but results in a significant reduction in proliferative potential and early manifestation of cellular senescence features upon eMSCs culturing. Thus, we concluded that the long-term cryopreservation of cells of different types and biological origin can lead to irreversible changes of their karyotype and acceleration of cellular senescence.

Factors Defining Human Adipose Stem/Stromal Cell Immunomodulation in Vitro

Human adipose tissue-derived stem/stromal cells (hASCs) are adult multipotent mesenchymal stem/stromal cells with immunomodulatory capacities. Here, we present up-to-date knowledge on the impact of different experimental and donor-related factors on hASC immunoregulatory functions in vitro. The experimental determinants include the immunological status of hASCs relative to target immune cells, contact vs. contactless interaction, and oxygen tension. Factors such as the ratio of hASCs to immune cells, the cellular context, the immune cell activation status, and coculture duration are also discussed. Conditioning of hASCs with different approaches before interaction with immune cells, hASC culture in xenogenic or xenofree culture medium, hASC culture in two-dimension vs. three-dimension with biomaterials, and the hASC passage number are among the experimental parameters that greatly may impact the hASC immunosuppressive potential in vitro, thus, they are also considered. Moreover, the influence of donor-related characteristics such as age, sex, and health status on hASC immunomodulation in vitro is reviewed. By analysis of the literature studies, most of the indicated determinants have been investigated in broad non-standardized ranges, so the results are not univocal. Clear conclusions cannot be drawn for the fine-tuned scenarios of many important factors to set a standard hASC immunopotency assay. Such variability needs to be carefully considered in further standardized research. Importantly, field experts' opinions may help to make it clearer.

Mesenchymal Stem Cells: A Promising Treatment for Thymic Involution

The thymus is the main immune organ in the body. However, the thymus gradually degenerates in early life, leading to a reduction in T-cell production and a decrease in immune function. Mesenchymal stem cells (MSCs) are a promising alternative for the treatment of thymus senescence due to their homing ability to the site of inflammation and their paracrine, anti-inflammatory, and antioxidant properties. However, the heterogeneity, difficulty of survival in vivo, short residence time, and low homing efficiency of the injected MSCs affect the clinical therapeutic effect. This article reviews strategies to improve the efficacy of mesenchymal stem cell therapy, including the selection of appropriate cell doses, transplantation frequency, and interval cycles. The survival rate of MSCs can be improved to some extent by improving the infusion mode of MSCs, such as simulating the in vivo environment, applying the biological technology of hydrogels and microgels, and iron oxide labeling technology, which can improve the curative effect and homing of MSCs, promote the regeneration of thymic epithelial cells, and restore the function of the thymus.

Characterization of CRISPR/Cas9-edited human placental allogenic stromal cells with low tissue factor expression and reduced thrombotic effects

The tissue factor (TF/CD142) expressed by mesenchymal stromal cells (MSCs) has been regarded as a safety concern in clinical applications as it may trigger thrombosis when MSCs administered intravenously. Human placental allogenic stromal cells (ASCs) are culture-expanded, undifferentiated MSC-like cells derived from full-term postpartum placenta and possess immunomodulatory and pro-angiogenic activities, however, express TF. Here we performed CRISPR/Cas9-mediated TF gene knock out (TFKO) in ASCs, leading to significantly lower TF expression, activity and thrombotic effects. ASCs' characteristics including expansion, expression of phenotypic markers and secretory profile remained unchanged in edited cells, and their immunomodulatory activities, which are functionally relevant to therapeutic applications, were not affected upon TFKO. Taken together, this study provides a feasible strategy which could improve the clinical safety features of MSC-based cell therapy by CRISRP/Cas9-mediated TF gene knock out.

Identification of a fundamental cryoinjury mechanism in MSCs and its mitigation through cell-cycle synchronization prior to freezing

Clinical development of cellular therapies, including mesenchymal stem/stromal cell (MSC) treatments, has been hindered by ineffective cryopreservation methods that result in substantial loss of post-thaw cell viability and function. Proposed solutions to generate high potency MSC for clinical testing include priming cells with potent cytokines such as interferon gamma (IFNγ) prior to cryopreservation, which has been shown to enhance post-thaw function, or briefly culturing to allow recovery from cryopreservation injury prior to administering to patients. However, both solutions have disadvantages: cryorecovery increases the complexity of manufacturing and distribution logistics, while the pleiotropic effects of IFNγ may have uncharacterized and unintended consequences on MSC function. To determine specific cellular functions impacted by cryoinjury, we first evaluated cell cycle status. It was discovered that S phase MSC are exquisitely sensitive to cryoinjury, demonstrating heightened levels of delayed apoptosis post-thaw and reduced immunomodulatory function. Blocking cell cycle progression at G0/G1 by growth factor deprivation (commonly known as serum starvation) greatly reduced post-thaw dysfunction of MSC by preventing apoptosis induced by double-stranded breaks in labile replicating DNA that form during the cryopreservation and thawing processes. Viability, clonal growth and T cell suppression function were preserved at pre-cryopreservation levels and were no different than cells prior to freezing or frozen after priming with IFNγ. Thus, we have developed a robust and effective strategy to enhance post-thaw recovery of therapeutic MSC.

Opportunities and challenges: mesenchymal stem cells in the treatment of multiple sclerosis

Multiple sclerosis (MS) was once considered an untreatable disease. Through years of research, many drugs have been discovered and are widely used for the treatment of MS. However, the current treatment can only alleviate the clinical symptoms of MS and has serious side effects. Mesenchymal stem cells (MSCs) provide neuroprotection by migrating to injured tissues, suppressing inflammation, and fostering neuronal repair. Therefore, MSCs therapy holds great promise for MS treatment. This review aimed to assess the feasibility and safety of use of MSCs in MS treatment as well as its development prospect in clinical treatment by analysing the existing clinical studies.

Comparison of Cryopreservation Media for Mesenchymal Stem Cell Spheroids

Multipotent mesenchymal stromal/stem cell (MSC) spheroids generated in three-dimensional culture are of considerable interest as a novel therapeutic tool for regenerative medicine. However, the lack of reliable methods for storing MSC spheroids represents a significant roadblock to their successful use in the clinic. An ideal storage medium for MSC spheroids should function as both a vehicle for delivery and a cryoprotectant during storage of spheroids for use at a later time. In this study, we compared the outcomes after subjecting MSC spheroids to a freeze/thaw cycle in three Good Manufacturing Practices-grade cryopreservation media, CryoStor10 (CS10), Stem-Cellbanker (SCB), and Recovery Cell Culture Freezing Media (RFM) or conventional freezing medium (CM) (CM, Dulbecco's modified Eagle's medium containing 20% fetal bovine serum and 10% dimethyl sulfoxide) as a control for 2 months. The endpoints tested were viability, morphology, and expression of stem cell markers and other relevant genes. The results of LIVE/DEAD™ assays and annexin V/propidium iodide staining suggested that viability was relatively higher after one freeze/thaw cycle in CS10 or SCB than after freeze/thaw in CM or RFM. Furthermore, the relative "stemness" and expression of MSC markers were similar with or without freeze/thaw in CS10. Scanning electron microscopy also indicated that the surface morphology of MSC spheroids was well preserved after cryopreservation in CS10. Thus, even though it was tested for a short-term period, we suggest that CS10, which has been approved for clinical use by the U.S. Food and Drug Association, is a promising cryopreservation medium that would facilitate the development of MSC spheroids for future clinical use.

Secretome as a Tool to Treat Neurological Conditions: Are We Ready?

Due to their characteristics, mesenchymal stem cells (MSCs) are considered a potential therapy for brain tissue injury or degeneration. Nevertheless, despite the promising results observed, there has been a growing interest in the use of cell-free therapies in regenerative medicine, such as the use of stem cell secretome. This review provides an in-depth compilation of data regarding the secretome composition, protocols used for its preparation, as well as existing information on the impact of secretome administration on various brain conditions, pointing out gaps and highlighting relevant findings. Moreover, due to the ability of MSCs to respond differently depending on their microenvironment, preconditioning of MSCs has been used to modulate their composition and, consequently, their therapeutic potential. The different strategies used to modulate the MSC secretome were also reviewed. Although secretome administration was effective in improving functional impairments, regeneration, neuroprotection, and reducing inflammation in brain tissue, a high variability in secretome preparation and administration was identified, compromising the transposition of preclinical data to clinical studies. Indeed, there are no reports of the use of secretome in clinical trials. Despite the existing limitations and lack of clinical data, secretome administration is a potential tool for the treatment of various diseases that impact the CNS.

Improved Cryopreservation of Human Induced Pluripotent Stem Cell (iPSC) and iPSC-derived Neurons Using Ice-Recrystallization Inhibitors

Human induced pluripotent stem cells (iPSCs) and iPSC-derived neurons (iPSC-Ns) represent a differentiated modality toward developing novel cell-based therapies for regenerative medicine. However, the successful application of iPSC-Ns in cell-replacement therapies relies on effective cryopreservation. In this study, we investigated the role of ice recrystallization inhibitors (IRIs) as novel cryoprotectants for iPSCs and terminally differentiated iPSC-Ns. We found that one class of IRIs, N-aryl-D-aldonamides (specifically 2FA), increased iPSC post-thaw viability and recovery with no adverse effect on iPSC pluripotency. While 2FA supplementation did not significantly improve iPSC-N cell post-thaw viability, we observed that 2FA cryopreserved iPSC-Ns re-established robust neuronal network activity and synaptic function much earlier compared to CS10 cryopreserved controls. The 2FA cryopreserved iPSC-Ns retained expression of key neuronal specific and terminally differentiated markers and displayed functional electrophysiological and neuropharmacological responses following treatment with neuroactive agonists and antagonists. We demonstrate how optimizing cryopreservation media formulations with IRIs represents a promising strategy to improve functional cryopreservation of iPSCs and post-mitotic iPSC-Ns, the latter of which have been challenging to achieve. Developing IRI enabling technologies to support an effective cryopreservation and an efficiently managed cryo-chain is fundamental to support the delivery of successful iPSC-derived therapies to the clinic.

Marrow-Derived Autologous Stromal Cells for the Restoration of Salivary Hypofunction (MARSH): A pilot, first-in-human study of interferon gamma-stimulated marrow mesenchymal stromal cells for treatment of radiation-induced xerostomia

BACKGROUND AIMS

Xerostomia, or the feeling of dry mouth, is a significant side effect of radiation therapy for patients with head and neck cancer (HNC). Preliminary data suggest that mesenchymal stromal/stem cells (MSCs) can improve salivary function. We performed a first-in-human pilot study of interferon gamma (IFNγ)-stimulated autologous bone marrow-derived MSCs, or MSC(M), for the treatment of radiation-induced xerostomia (RIX). Here we present the primary safety and secondary efficacy endpoints.

METHODS

A single-center pilot clinical trial was conducted investigating the safety and tolerability of autologous IFNγ-stimulated MSC(M). The study was conducted under an approved Food and Drug Administration Investigational New Drug application using an institutional review board-approved protocol (NCT04489732). Patients underwent iliac crest bone marrow aspirate and MSC(M) were isolated, cultured, stimulated with IFNγ and cryopreserved for later use. Banked cells were thawed and allowed to recover in culture before patients received a single injection of 10 × 106 MSC(M) into the right submandibular gland under ultrasound guidance. The primary objective was determination of safety and tolerability by evaluating dose-limiting toxicity (DLT). A DLT was defined as submandibular pain >5 on a standard 10-point pain scale or any serious adverse event (SAE) within 1 month after injection. Secondary objectives included analysis of efficacy as measured by salivary quantification and using three validated quality of life instruments. Quantitative results are reported as mean and standard deviation.

RESULTS

Six patients with radiation-induced xerostomia who had completed radiation at least 2 years previously (average 7.8 years previously) were enrolled in the pilot study. The median age was 71 (61-74) years. Five (83%) patients were male. Five patients (83%) were treated with chemoradiation and one patient (17%) with radiation alone. Grade 1 pain was seen in 50% of patients after submandibular gland injection; all pain resolved within 4 days. No patients reported pain 1 month after injection, with no SAE or other DLTs reported 1 month after injection. The analysis of secondary endpoints demonstrated a trend of increased salivary production. Three patients (50%) had an increase in unstimulated saliva at 1 and 3 months after MSC(M) injection. Quality of life surveys also showed a trend toward improvement.

CONCLUSIONS

Injection of autologous IFNγ-stimulated MSC(M) into a singular submandibular gland of patients with RIX is safe and well tolerated in this pilot study. A trend toward an improvement in secondary endpoints of salivary quantity and quality of life was observed. This first-in-human study provides support for further investigation into IFNγ-stimulated MSC(M) injected in both submandibular glands as an innovative approach to treat RIX and improve quality of life for patients with HNC.

Stem cell-based therapy for COVID-19

While The World Health Organization (WHO) has announced that COVID-19 is no longer a public health emergency of international concern(PHEIC), the risk of reinfection and new emerging variants still makes it crucial to study and work towards the prevention of COVID-19. Stem cell and stem cell-like derivatives have shown some promising results in clinical trials and preclinical studies as an alternative treatment option for the pulmonary illnesses caused by the COVID-19 and can be used as a potential vaccine. In this review, we will systematically summarize the pathophysiological process and potential mechanisms underlying stem cell-based therapy in COVID-19, and the registered COVID-19 clinical trials, and engineered extracellular vesicle as a potential vaccine for preventing COVID-19.

Interactions of mesenchymal stromal/stem cells and immune cells following MSC-based therapeutic approaches in rheumatoid arthritis

Rheumatoid arthritis (RA) is considered to be a degenerative and progressive autoimmune disorder. Although several medicinal regimens are used to treat RA, potential adverse events such as metabolic disorders and increased risk of infection, as well as drug resistance in some patients, make it essential to find an effective and safe therapeutic approach. Mesenchymal stromal/stem cells (MSCs) are a group of non-hematopoietic stromal cells with immunomodulatory and inhibitory potential. These cells exert their regulatory properties through direct cell-to-cell interactions and paracrine effects on various immune and non-immune cells. As conventional therapeutic approaches for RA are limited due to their side effects, and some patients became refractory to the treatment, MSCs are considered as a promising alternative treatment for RA. In this review, we introduced various experimental and clinical studies conducted to evaluate the therapeutic effects of MSCs on animal models of arthritis and RA patients. Then, possible modulatory and suppressive effects of MSCs on different innate and adaptive immune cells, including dendritic cells, neutrophils, macrophages, natural killer cells, B lymphocytes, and various subtypes of T cells, were categorized and summarized. Finally, limitations and future considerations for the efficient application of MSCs as a therapeutic approach in RA patients were presented.

Autoantibodies from patients with kidney allograft vasculopathy stimulate a proinflammatory switch in endothelial cells and monocytes mediated via GPCR-directed PAR1-TNF-α signaling

Non-HLA-directed regulatory autoantibodies (RABs) are known to target G-protein coupled receptors (GPCRs) and thereby contribute to kidney transplant vasculopathy and failure. However, the detailed underlying signaling mechanisms in human microvascular endothelial cells (HMECs) and immune cells need to be clarified in more detail. In this study, we compared the immune stimulatory effects and concomitant intracellular and extracellular signaling mechanisms of immunoglobulin G (IgG)-fractions from kidney transplant patients with allograft vasculopathy (KTx-IgG), to that from patients without vasculopathy, or matched healthy controls (Con-IgG). We found that KTx-IgG from patients with vasculopathy, but not KTx-IgG from patients without vasculopathy or Con-IgG, elicits HMEC activation and subsequent upregulation and secretion of tumor necrosis factor alpha (TNF-α) from HMECs, which was amplified in the presence of the protease-activated thrombin receptor 1 (PAR1) activator thrombin, but could be omitted by selectively blocking the PAR1 receptor. The amount and activity of the TNF-α secreted by HMECs stimulated with KTx-IgG from patients with vasculopathy was sufficient to induce subsequent THP-1 monocytic cell activation. Furthermore, AP-1/c-FOS, was identified as crucial transcription factor complex controlling the KTx-IgG-induced endothelial TNF-α synthesis, and mircoRNA-let-7f-5p as a regulatory element in modulating the underlying signaling cascade. In conclusion, exposure of HMECs to KTx-IgG from patients with allograft vasculopathy, but not KTx-IgG from patients without vasculopathy or healthy Con-IgG, triggers signaling through the PAR1-AP-1/c-FOS-miRNA-let7-axis, to control TNF-α gene transcription and TNF-α-induced monocyte activation. These observations offer a greater mechanistic understanding of endothelial cells and subsequent immune cell activation in the clinical setting of transplant vasculopathy that can eventually lead to transplant failure, irrespective of alloantigen-directed responses.

Optimized reagents for immunopotency assays on mesenchymal stromal cells for clinical use

Multipotent mesenchymal stromal cells (MSC) offer new therapeutic opportunities based on their ability to modulate an imbalanced immune system. Immunomodulatory potency is typically demonstrated in vitro by measuring the presence of surrogate markers (i.e., indoleamine-2,3-dioxygenase, IDO; tumor necrosis factor receptor type 1, TNFR1) and/or functional assays in co-cultures (i.e., inhibition of lymphoproliferation, polarization of macrophages). However, the biological variability of reagents used in the latter type of assays leads to unreliable and difficult to reproduce data therefore making cross-comparison between batches difficult, both at the intra- and inter-laboratory levels. Herein, we describe a set of experiments aiming at the definition and validation of reliable biological reagents as a first step towards standardization of a potency assay. This approach is based on the co-culture of Wharton's jelly (WJ)-derived MSC and cryopreserved pooled peripheral blood mononuclear cells. Altogether, we successfully defined a robust and reproducible immunopotency assay based on previously described methods incorporating substantial improvements such as cryopreservation of multiple vials of pooled peripheral blood mononuclear cells (PBMC) from 5 individual donors that enable a number of tests with same reagents, also reducing waste of PBMC from individual donors and therefore contributing to a more efficient and ethical method to use substances of human origin (SoHO). The new methodology was successfully validated using 11 batches of clinical grade MSC,WJ. Methods described here contribute to minimize PBMC donor variability while reducing costs, streamlining assay setup and convenience and laying the foundations for harmonization of biological reagents usage in standardized immunopotency assays for MSC. HIGHLIGHTS: • The use of pools of peripheral blood mononuclear cells (PBMCs) in potency assays contributes to robust and reproducible results, which is key in the assessment of mesenchymal stroma cells (MSC) potency for batch release. • Cryopreservation of PBMCs does not impact negatively on their activation and proliferation abilities. • Cryopreserved pools of PBMC constitutes convenient off-the-shelf reagents for potency assays. • Cryopreservation of pooled PBMCs from multiple donors is a way to reduce waste of donated PBMC and its associated costs, as well as reducing the impact of individual donor variability of substances of human origin (SoHO).

Comparative Analysis of Biological Signatures between Freshly Preserved and Cryo-Preserved Bone Marrow Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) can differentiate into multiple connective tissue lineages, including osteoblasts, chondrocytes, and adipocytes. MSCs secrete paracrine molecules that are associated with immunomodulation, anti-fibrotic effects, and angiogenesis. Due to their orchestrative potential, MSCs have been therapeutically applied for several diseases. An important aspect of this process is the delivery of high-quality MSCs to patients at the right time, and cryo-biology and cryo-preservation facilitate the advancement of the logistics thereof. This study aimed to compare the biological signatures between freshly preserved and cryo-preserved MSCs by using big data sourced from the Pharmicell database. From 2011 to 2022, data on approximately 2300 stem cell manufacturing cases were collected. The dataset included approximately 60 variables, including viability, population doubling time (PDT), immunophenotype, and soluble paracrine molecules. In the dataset, 671 cases with no missing data were able to receive approval from an Institutional Review Board and were analyzed. Among the 60 features included in the final dataset, 20 were selected by experts and abstracted into two features by using a principal component analysis. Circular clustering did not introduce any differences between the two MSC preservation methods. This pattern was also observed when using viability, cluster of differentiation (CD) markers, and paracrine molecular indices as inputs for unsupervised analysis. The individual average PDT and cell viability at most passages did not differ according to the preservation method. Most immunophenotypes (except for the CD14 marker) and paracrine molecules did not exhibit different mean levels or concentrations between the frozen and unfrozen MSC groups. Collectively, the biochemical signatures of the cryo-preserved and unfrozen bone marrow MSCs were comparable.

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.

Expanded Hemodialysis ameliorates uremia-induced impairment of vasculoprotective KLF2 and concomitant proinflammatory priming of endothelial cells through an ERK/AP1/cFOS-dependent mechanism

Aims

Expanded hemodialysis (HDx) therapy with improved molecular cut-off dialyzers exerts beneficial effects on lowering uremia-associated chronic systemic microinflammation, a driver of endothelial dysfunction and cardiovascular disease (CVD) in hemodialysis (HD) patients with end-stage renal disease (ESRD). However, studies on the underlying molecular mechanisms are still at an early stage. Here, we identify the (endothelial) transcription factor Krüppel-like factor 2 (KLF2) and its associated molecular signalling pathways as key targets and regulators of uremia-induced endothelial micro-inflammation in the HD/ESRD setting, which is crucial for vascular homeostasis and controlling detrimental vascular inflammation.

Methods and results

First, we found that human microvascular endothelial cells (HMECs) and other typical endothelial and kidney model cell lines (e.g. HUVECs, HREC, and HEK) exposed to uremic serum from patients treated with two different hemodialysis regimens in the Permeability Enhancement to Reduce Chronic Inflammation II (PERCI-II) crossover clinical trial - comparing High-Flux (HF) and Medium Cut-Off (MCO) membranes - exhibited strongly reduced expression of vasculoprotective KLF2 with HF dialyzers, while dialysis with MCO dialyzers led to the maintenance and restoration of physiological KLF2 levels in HMECs. Mechanistic follow-up revealed that the strong downmodulation of KLF2 in HMECs exposed to uremic serum was mediated by a dominant engagement of detrimental ERK instead of beneficial AKT signalling, with subsequent AP1-/c-FOS binding in the KLF2 promoter region, followed by the detrimental triggering of pleiotropic inflammatory mediators, while the introduction of a KLF2 overexpression plasmid could restore physiological KLF2 levels and downmodulate the detrimental vascular inflammation in a mechanistic rescue approach.

Conclusion

Uremia downmodulates vasculoprotective KLF2 in endothelium, leading to detrimental vascular inflammation, while MCO dialysis with the novel improved HDx therapy approach can maintain physiological levels of vasculoprotective KLF2.

Fetal Muse-based therapy prevents lethal radio-induced gastrointestinal syndrome by intestinal regeneration

BACKGROUND

Human multilineage-differentiating stress enduring (Muse) cells are nontumorigenic endogenous pluripotent-like stem cells that can be easily obtained from various adult or fetal tissues. Regenerative effects of Muse cells have been shown in some disease models. Muse cells specifically home in damaged tissues where they exert pleiotropic effects. Exposition of the small intestine to high doses of irradiation (IR) delivered after radiotherapy or nuclear accident results in a lethal gastrointestinal syndrome (GIS) characterized by acute loss of intestinal stem cells, impaired epithelial regeneration and subsequent loss of the mucosal barrier resulting in sepsis and death. To date, there is no effective medical treatment for GIS. Here, we investigate whether Muse cells can prevent lethal GIS and study how they act on intestinal stem cell microenvironment to promote intestinal regeneration.

METHODS

Human Muse cells from Wharton's jelly matrix of umbilical cord (WJ-Muse) were sorted by flow cytometry using the SSEA-3 marker, characterized and compared to bone-marrow derived Muse cells (BM-Muse). Under gas anesthesia, GIS mice were treated or not through an intravenous retro-orbital injection of 50,000 WJ-Muse, freshly isolated or cryopreserved, shortly after an 18 Gy-abdominal IR. No immunosuppressant was delivered to the mice. Mice were euthanized either 24 h post-IR to assess early small intestine tissue response, or 7 days post-IR to assess any regenerative response. Mouse survival, histological stainings, apoptosis and cell proliferation were studied and measurement of cytokines, recruitment of immune cells and barrier functional assay were performed.

RESULTS

Injection of WJ-Muse shortly after abdominal IR highly improved mouse survival as a result of a rapid regeneration of intestinal epithelium with the rescue of the impaired epithelial barrier. In small intestine of Muse-treated mice, an early enhanced secretion of IL-6 and MCP-1 cytokines was observed associated with (1) recruitment of monocytes/M2-like macrophages and (2) proliferation of Paneth cells through activation of the IL-6/Stat3 pathway.

CONCLUSION

Our findings indicate that a single injection of a small quantity of WJ-Muse may be a new and easy therapeutic strategy for treating lethal GIS.

Adipose tissue-derived human mesenchymal stromal cells can better suppress complement lysis, engraft and inhibit acute graft-versus-host disease in mice

BACKGROUND

Acute graft-versus-host disease (aGvHD) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT). Transplantation of immunosuppressive human mesenchymal stromal cells (hMSCs) can protect against aGvHD post-HSCT; however, their efficacy is limited by poor engraftment and survival. Moreover, infused MSCs can be damaged by activated complement, yet strategies to minimise complement injury of hMSCs and improve their survival are limited.

METHODS

Human MSCs were derived from bone marrow (BM), adipose tissue (AT) and umbilical cord (UC). In vitro immunomodulatory potential was determined by co-culture experiments between hMSCs and immune cells implicated in aGvHD disease progression. BM-, AT- and UC-hMSCs were tested for their abilities to protect aGvHD in a mouse model of this disease. Survival and clinical symptoms were monitored, and target tissues of aGvHD were examined by histopathology and qPCR. Transplanted cell survival was evaluated by cell tracing and by qPCR. The transcriptome of BM-, AT- and UC-hMSCs was profiled by RNA-sequencing. Focused experiments were performed to compare the expression of complement inhibitors and the abilities of hMSCs to resist complement lysis.

RESULTS

Human MSCs derived from three tissues divergently protected against aGvHD in vivo. AT-hMSCs preferentially suppressed complement in vitro and in vivo, resisted complement lysis and survived better after transplantation when compared to BM- and UC-hMSCs. AT-hMSCs also prolonged survival and improved the symptoms and pathological features of aGvHD. We found that complement-decay accelerating factor (CD55), an inhibitor of complement, is elevated in AT-hMSCs and contributed to reduced complement activation. We further report that atorvastatin and erlotinib could upregulate CD55 and suppress complement in all three types of hMSCs.

CONCLUSION

CD55, by suppressing complement, contributes to the improved protection of AT-hMSCs against aGvHD. The use of AT-hMSCs or the upregulation of CD55 by small molecules thus represents promising new strategies to promote hMSC survival to improve the efficacy of transplantation therapy. As complement injury is a barrier to all types of hMSC therapy, our findings are of broad significance to enhance the use of hMSCs for the treatment of a wide range of disorders.

Lysis and phenotypic modulation of mesenchymal stromal cells upon blood contact triggers anti-inflammatory skewing of the peripheral innate immune repertoire

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are used to treat immune-related disorders, including graft-versus-host disease. Upon intravenous infusion, MSCs trigger the instant blood-mediated inflammatory response, resulting in activation of both complement and coagulation cascades, and are rapidly cleared from circulation. Despite no/minimal engraftment, long-term immunoregulatory properties are evident. The aim of this study was to establish the effects of blood exposure on MSC viability and immunomodulatory functions.

METHODS

Human, bone marrow derived MSCs were exposed to human plasma +/- heat inactivation or whole blood. MSC number, viability and cellular damage was assessed using the JC-1 mitochondrial depolarization assay and annexin V staining. C3c binding and expression of the inhibitory receptors CD46, CD55 and CD59 and complement receptors C3aR and C5aR were evaluated by flow cytometry. MSCs pre-exposed to plasma were cultured with peripheral blood mononuclear cells (PBMCs) and monocyte subsets characterized by flow cytometry. The PBMC and MSC secretome was assessed using enzyme-linked immunosorbent assays against tumor necrosis factor alpha, interleukin (IL)-6 and IL-10. Monocyte recruitment towards the MSC secretome was evaluated using Boyden chambers and screened for chemotactic factors including monocyte chemoattractant protein (MCP)-1. MSC effects on the peripheral immune repertoire was also evaluated in whole blood by flow cytometry.

RESULTS

Plasma induced rapid lysis of 57% of MSCs, which reduced to 1% lysis with heat inactivation plasma. Of those cells that were not lysed, C3c could be seen bound to the surface of the cells, with a significant swelling of the MSCs and induction of cell death. The MSC secretome reduced monocyte recruitment, in part due to a reduction in MCP-1, and downregulated PBMC tumor necrosis factor alpha secretion while increasing IL-6 levels in the co-culture supernatant. A significant decrease in CD14⁺ monocytes was evident after MSC addition to whole blood alongside a significant increase in IL-6 levels, with those remaining monocytes demonstrating an increase in classical and decrease in non-classical subsets. This was accompanied by a significant increase in both mononuclear and polymorphonuclear myeloid-derived suppressor cells.

CONCLUSIONS

This study demonstrates that a significant number of MSCs are rapidly lysed upon contact with blood, with those surviving demonstrating a shift in their phenotype, including a reduction in the secretion of monocyte recruitment factors and an enhanced ability to skew the phenotype of monocytes. Shifts in the innate immune repertoire, towards an immunosuppressive profile, were also evident within whole blood after MSC addition. These findings suggest that exposure to blood components can promote peripheral immunomodulation via multiple mechanisms that persists within the system long after the infused MSCs have been cleared.

Systematic review and meta-analysis of cell therapy for COVID-19: global clinical trial landscape, published safety/efficacy outcomes, cell product manufacturing and clinical delivery

During the pandemic of severe respiratory distress syndrome coronavirus 2 (SARS-CoV2), many novel therapeutic modalities to treat Coronavirus 2019 induced disease (COVID-19) were explored. This study summarizes 195 clinical trials of advanced cell therapies targeting COVID-19 that were registered over the two years between January 2020 to December 2021. In addition, this work also analyzed the cell manufacturing and clinical delivery experience of 26 trials that published their outcomes by July 2022. Our demographic analysis found the highest number of cell therapy trials for COVID-19 was in United States, China, and Iran (N=53, 43, and 19, respectively), with the highest number per capita in Israel, Spain, Iran, Australia, and Sweden (N=0.641, 0.232, 0,223, 0.194, and 0.192 trials per million inhabitants). The leading cell types were multipotent mesenchymal stromal/stem cells (MSCs), natural killer (NK) cells, and mononuclear cells (MNCs), accounting for 72%, 9%, and 6% of the studies, respectively. There were 24 published clinical trials that reported on infusions of MSCs. A pooled analysis of these MSC studies found that MSCs provide a relative risk reduction for all-cause COVID-19 mortality of RR=0.63 (95% CI 0.46 to 0.85). This result corroborates previously published smaller meta-analyses, which suggested that MSC therapy demonstrated a clinical benefit for COVID-19 patients. The sources of the MSCs used in these studies and their manufacturing and clinical delivery methods were remarkably heterogeneous, with some predominance of perinatal tissue-derived products. Our results highlight the important role that cell therapy products may play as an adjunct therapy in the management of COVID-19 and its related complications, as well as the importance of controlling key manufacturing parameters to ensure comparability between studies. Thus, we support ongoing calls for a global registry of clinical studies with MSC products that could better link cell product manufacturing and delivery methods to clinical outcomes. Although advanced cell therapies may provide an important adjunct treatment for patients affected by COVID-19 in the near future, preventing pathology through vaccination still remains the best protection to date. We conducted a systematic review and meta-analysis of advanced cell therapy clinical trials as potential novel treatment for COVID-19 (resulting from SARS-CoV-2 coronavirus infection), including analysis of the global clinical trial landscape, published safety/efficacy outcomes (RR/OR), and details on cell product manufacturing and clinical delivery. This study had a 2-year observation interval from start of January 2020 to end of December 2021, including a follow-up period until end of July to identify published outcomes, which covers the most vivid period of clinical trial activity, and is also the longest observation period studied until today. In total, we identified 195 registered advanced cell therapy studies for COVID-19, employing 204 individual cell products. Leading registered trial activity was attributed to the USA, China, and Iran. Through the end of July 2022, 26 clinical trials were published, with 24 out of 26 articles employing intravenous infusions (IV) of mesenchymal stromal/stem cell (MSC) products. Most of the published trials were attributed to China and Iran. The cumulative results from the 24 published studies employing infusions of MSCs indicated an improved survival (RR=0.63 with 95% Confidence Interval 0.46 to 0.85). Our study is the most comprehensive systematic review and meta-analysis on cell therapy trials for COVID-19 conducted to date, clearly identifying the USA, China, and Iran as leading advanced cell therapy trial countries for COVID-19, with further strong contributions from Israel, Spain, Australia and Sweden. Although advanced cell therapies may provide an important adjunct treatment for patients affected by COVID-19 in the future, preventing pathology through vaccination remains the best protection.

ROCK inhibition enhanced hepatocyte liver engraftment by retaining membrane CD59 and attenuating complement activation

Hepatocyte transplantation can be an effective treatment for patients with certain liver-based metabolic disorders and liver injuries. Hepatocytes are usually infused into the portal vein, from which hepatocytes migrate into the liver and integrate into the liver parenchyma. However, early cell loss and poor liver engraftment represent major hurdles to sustaining the recovery of diseased livers after transplantation. In the present study, we found that ROCK (Rho-associated kinase) inhibitors significantly enhanced in vivo hepatocyte engraftment. Mechanistic studies suggested that the isolation of hepatocytes caused substantial degradation of cell membrane proteins, including the complement inhibitor CD59, probably due to shear stress-induced endocytosis. ROCK inhibition by ripasudil, a clinically used ROCK inhibitor, can protect transplanted hepatocytes by retaining cell membrane CD59 and blocking the formation of the membrane attack complex. Knockdown of CD59 in hepatocytes eliminates ROCK inhibition-enhanced hepatocyte engraftment. Ripasudil can accelerate liver repopulation of fumarylacetoacetate hydrolase-deficient mice. Our work reveals a mechanism underlying hepatocyte loss after transplantation and provides immediate strategies to enhance hepatocyte engraftment by inhibiting ROCK.

Mesenchymal stromal cells in hepatic fibrosis/cirrhosis: from pathogenesis to treatment

Hepatic fibrosis/cirrhosis is a significant health burden worldwide, resulting in liver failure or hepatocellular carcinoma (HCC) and accounting for many deaths each year. The pathogenesis of hepatic fibrosis/cirrhosis is very complex, which makes treatment challenging. Endogenous mesenchymal stromal cells (MSCs) have been shown to play pivotal roles in the pathogenesis of hepatic fibrosis. Paradoxically, exogenous MSCs have also been used in clinical trials for liver cirrhosis, and their effectiveness has been observed in most completed clinical trials. There are still many issues to be resolved to promote the use of MSCs in the clinic in the future. In this review, we will examine the controversial role of MSCs in the pathogenesis and treatment of hepatic fibrosis/cirrhosis. We also investigated the clinical trials involving MSCs in liver cirrhosis, summarized the parameters that need to be standardized, and discussed how to promote the use of MSCs from a clinical perspective.

Contrariety of Human Bone Marrow Mesenchymal Stromal Cell Functionality in Modulating Circulatory Myeloid and Plasmacytoid Dendritic Cell Subsets

Mesenchymal Stromal Cells (MSCs) derived from bone marrow are widely tested in clinical trials as a cellular therapy for potential inflammatory disorders. The mechanism of action of MSCs in mediating immune modulation is of wide interest. In the present study, we investigated the effect of human bone-marrow-derived MSCs in modulating the circulating peripheral blood dendritic cell responses through flow cytometry and multiplex secretome technology upon their coculture ex vivo. Our results demonstrated that MSCs do not significantly modulate the responses of plasmacytoid dendritic cells. However, MSCs dose-dependently promote the maturation of myeloid dendritic cells. Mechanistic analysis showed that dendritic cell licensing cues (Lipopolysaccharide and Interferon-gamma) stimulate MSCs to secret an array of dendritic cell maturation-associated secretory factors. We also identified that MSC-mediated upregulation of myeloid dendritic cell maturation is associated with the unique predictive secretome signature. Overall, the present study demonstrated the dichotomy of MSC functionality in modulating myeloid and plasmacytoid dendritic cells. This study provides clues that clinical trials need to investigate if circulating dendritic cell subsets in MSC therapy can serve as potency biomarkers.

Current perspectives on mesenchymal stromal cell therapy for graft versus host disease

Graft versus host disease (GvHD) is the clinical condition in which bone marrow-derived mesenchymal stromal cells (MSCs) have been most frequently studied. In this review, we summarize the experience from clinical trials that have paved the way to translation. While MSC-based therapy has shown an exceptional safety profile, identifying potency assays and disease biomarkers that reliably predict the capacity of a specific MSC batch to alleviate GvHD has been difficult. As GvHD diagnosis and staging are based solely on clinical criteria, individual patients recruited in the same clinical trial may have vastly different underlying biology, obscuring trial outcomes and making it difficult to determine the benefit of MSCs in subgroups of patients. An accumulating body of evidence indicates the importance of considering not only the cell product but also patient-specific biomarkers and/or immune characteristics in determining MSC responsiveness. A mode of action where intravascular MSC destruction is followed by monocyte-efferocytosis-mediated skewing of the immune repertoire in a permissive inflammatory environment would both explain why cell engraftment is irrelevant for MSC efficacy and stress the importance of biologic differences between responding and nonresponding patients. We recommend a combined analysis of clinical outcomes and both biomarkers of disease activity and MSC potency assays to identify patients with GvHD who are likely to benefit from MSC therapy.

Banking of perinatal mesenchymal stem/stromal cells for stem cell-based personalized medicine over lifetime: Matters arising

Mesenchymal stromal/stem cells (MSCs) are currently applied in regenerative medicine and tissue engineering. Numerous clinical studies have indicated that MSCs from different tissue sources can provide therapeutic benefits for patients. MSCs derived from either human adult or perinatal tissues have their own unique advantages in their medical practices. Usually, clinical studies are conducted by using of cultured MSCs after thawing or short-term cryopreserved-then-thawed MSCs prior to administration for the treatment of a wide range of diseases and medical disorders. Currently, cryogenically banking perinatal MSCs for potential personalized medicine for later use in lifetime has raised growing interest in China as well as in many other countries. Meanwhile, this has led to questions regarding the availability, stability, consistency, multipotency, and therapeutic efficiency of the potential perinatal MSC-derived therapeutic products after long-term cryostorage. This opinion review does not minimize any therapeutic benefit of perinatal MSCs in many diseases after short-term cryopreservation. This article mainly describes what is known about banking perinatal MSCs in China and, importantly, it is to recognize the limitation and uncertainty of the perinatal MSCs stored in cryobanks for stem cell medical treatments in whole life. This article also provides several recommendations for banking of perinatal MSCs for potentially future personalized medicine, albeit it is impossible to anticipate whether the donor will benefit from banked MSCs during her/his lifetime.

Bioengineered tissue and cell therapy products are efficiently cryopreserved with pathogen-inactivated human platelet lysate-based solutions

BACKGROUND

There remains much interest in improving cryopreservation techniques for advanced therapy medicinal products (ATMPs). Recently, human platelet lysate (hPL) has emerged as a promising candidate to replace fetal bovine serum (FBS) as a xeno-free culture supplement for the expansion of human cell therapy products. Whether hPL can also substitute for FBS in cryopreservation procedures remains poorly studied. Here, we evaluated several cryoprotective formulations based on a proprietary hPL for the cryopreservation of bioengineered tissues and cell therapy products.

METHODS

We tested different xenogeneic-free, pathogen-inactivated hPL (ihPL)- and non-inactivated-based formulations for cryopreserving bioengineered tissue (cellularized nanostructured fibrin agarose hydrogels (NFAHs)) and common cell therapy products including bone marrow-derived mesenchymal stromal cells (BM-MSCs), human dermal fibroblasts (FBs) and neural stem cells (NSCs). To assess the tissue and cellular properties post-thaw of NFAHs, we analyzed their cell viability, identity and structural and biomechanical properties. Also, we evaluated cell viability, recovery and identity post-thaw in cryopreserved cells. Further properties like immunomodulation, apoptosis and cell proliferation were assessed in certain cell types. Additionally, we examined the stability of the formulated solutions. The formulations are under a bidding process with MD Bioproducts (Zurich, Switzerland) and are proprietary.

RESULTS

Amongst the tissue-specific solutions, Ti5 (low-DMSO and ihPL-based) preserved the viability and the phenotype of embedded cells in NFAHs and preserved the matrix integrity and biomechanical properties similar to those of the standard cryopreservation solution (70% DMEM + 20% FBS + 10% DMSO). All solutions were stable at - 20 °C for at least 3 months. Regarding cell-specific solutions, CeA maintained the viability of all cell types > 80%, preserved the immunomodulatory properties of BM-MSCs and promoted good recovery post-thaw. Besides, both tested solutions were stable at - 20 °C for 18 months. Finally, we established that there is a 3-h window in which thawed NFAHs and FBs maintain optimum viability immersed in the formulated solutions and at least 2 h for BM-MSCs.

CONCLUSIONS

Our results show that pathogen-inactivated solutions Ti5 allocated for bioengineered tissues and CeA allocated for cells are efficient and safe candidates to cryopreserve ATMPs and offer a xenogeneic-free and low-DMSO alternative to commercially available cryoprotective solutions.

Rapid and effective preparation of clonal bone marrow-derived mesenchymal stem/stromal cell sheets to reduce renal fibrosis

Allogeneic "off-the-shelf" mesenchymal stem/stromal cell (MSC) therapy requires scalable, quality-controlled cell manufacturing and distribution systems to provide clinical-grade products using cryogenic cell banking. However, previous studies report impaired cell function associated with administering freeze-thawed MSCs as single cell suspensions, potentially compromising reliable therapeutic efficacy. Using long-term culture-adapted clinical-grade clonal human bone marrow MSCs (cBMSCs) in this study, we engineered cBMSC sheets in 24 h to provide rapid preparation. We then sought to determine the influence of cBMSC freeze-thawing on both in vitro production of pro-regenerative factors and in vivo ability to reduce renal fibrosis in a rat model compared to freshly harvested cBMSCs. Sheets from freeze-thawed cBMSCs sheets exhibited comparable in vitro protein production and gene expression of pro-regenerative factors [e.g., hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and interleukin 10 (IL-10)] to freshly harvested cBMSC sheets. Additionally, freeze-thawed cBMSC sheets successfully suppressed renal fibrosis in vivo in an established rat ischemia-reperfusion injury model. Despite previous studies reporting that freeze-thawed MSCs exhibit impaired cell functions compared to fresh MSC single cell suspensions, cell sheets engineered from freeze-thawed cBMSCs do not exhibit impaired cell functions, supporting critical steps toward future clinical translation of cBMSC-based kidney disease treatment.

Research progress in clinical trials of stem cell therapy for stroke and neurodegenerative diseases

The incidence of stroke and neurodegenerative diseases is gradually increasing in modern society, but there is still no treatment that is effective enough. Stem cells are cells that can reproduce (self-renew) and differentiate into the body, which have shown significance in basic research, while doctors have also taken them into clinical trials to determine their efficacy and safety. Existing clinical trials mainly include middle-aged and elderly patients with stroke or Parkinson's disease (mostly 40-80 years old), mainly involving injection of mesenchymal stem cells and bone marrow mesenchymal stem cells through the veins and the putamen, with a dosage of mostly 106-108 cells. The neural and motor functions of the patients were restored after stem cell therapy, and the safety was found to be good during the follow-up period of 3 months to 5 years. Here, we review all clinical trials and the latest advances in stroke, Alzheimer's disease, and Parkinson's disease, with the hope that stem cell therapy will be used in the clinic in the future to achieve effective treatment rates and benefit patients.

Cryoprotection in Human Mesenchymal Stromal/Stem Cells: Synergistic Impact of Urea and Glucose

Standard freezing protocols of clinically relevant cell lines commonly employ agents such as fetal bovine serum and dimethyl sulfoxide, which are a potential concern from both a regulatory and a patient safety perspective. The aim of this work was to develop formulations with safe and well tolerated excipients for the (cryo-) preservation of cell therapy products. We evaluated the cryoprotective capabilities of urea and glucose through measurements of cell metabolic activity. Freezing of clinically relevant human mesenchymal stromal/stem cells and human dermal fibroblasts at ≤ - 65°C at equimolar ratios of urea and glucose resulted in comparable viabilities to established dimethyl sulfoxide. Pre-incubation of human mesenchymal stromal/stem cells in trehalose and addition of mannitol and sucrose to the formulation further enhanced cell viability after freeze-thaw stress. Other cell types assessed (A549 and SK-N-AS) could not satisfactorily be preserved with urea and glucose, highlighting the need for tailored formulations to sustain acceptable cryopreservation.

Mesenchymal stem cells in the treatment of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a disease caused by mutations in different genes resulting in mild, severe, or lethal forms. With no cure, researchers have investigated the use of cell therapy to correct the underlying molecular defects of OI. Mesenchymal stem cells (MSCs) are of particular interest because of their differentiation capacity, immunomodulatory effects, and their ability to migrate to sites of damage. MSCs can be isolated from different sources, expanded in culture, and have been shown to be safe in numerous clinical applications. This review summarizes the preclinical and clinical studies of MSCs in the treatment of OI. Altogether, the culmination of these studies show that MSCs from different sources: 1) are safe to use in the clinic, 2) migrate to fracture sites and growth sites in bone, 3) engraft in low levels, 4) improve clinical outcome but have a transient effect, 5) have a therapeutic effect most likely due to paracrine mechanisms, and 6) have a reduced therapeutic potential when isolated from patients with OI.

Mesenchymal Stromal/Stem Cell (MSC)-Based Vector Biomaterials for Clinical Tissue Engineering and Inflammation Research: A Narrative Mini Review

Mesenchymal stromal/stem cells (MSCs) have the ability of self-renewal, the potential of multipotent differentiation, and a strong paracrine capacity, which are mainly used in the field of clinical medicine including dentistry and orthopedics. Therefore, tissue engineering research using MSCs as seed cells is a current trending directions. However, the healing effect of direct cell transplantation is unstable, and the paracrine/autocrine effects of MSCs cannot be effectively elicited. Tumorigenicity and heterogeneity are also concerns. The combination of MSCs as seed cells and appropriate vector materials can form a stable cell growth environment, maximize the secretory features of stem cells, and improve the biocompatibility and mechanical properties of vector materials that facilitate the delivery of drugs and various secretory factors. There are numerous studies on tissue engineering and inflammation of various biomaterials, mainly involving bioceramics, alginate, chitosan, hydrogels, cell sheets, nanoparticles, and three-dimensional printing. The combination of bioceramics, hydrogels and cell sheets with stem cells has demonstrated good therapeutic effects in clinical applications. The application of alginate, chitosan, and nanoparticles in animal models has also shown good prospects for clinical applications. Three-dimensional printing technology can circumvent the shortage of biomaterials, greatly improve the properties of vector materials, and facilitate the transplantation of MSCs. The purpose of this narrative review is to briefly discuss the current use of MSC-based carrier biomaterials to provide a useful resource for future tissue engineering and inflammation research using stem cells as seed cells.

Synovial Fluid Derived from Human Knee Osteoarthritis Increases the Viability of Human Adipose-Derived Stem Cells through Upregulation of FOSL1

Knee osteoarthritis (Knee OA) is an irreversible condition that causes bone deformity and degeneration of the articular cartilage that comprises the joints, resulting in chronic pain and movement disorders. The administration of cultured adipose-derived stem cells (ADSCs) into the knee joint cavity improves the clinical symptoms of Knee OA; however, the effect of synovial fluid (SF) filling the joint cavity on the injected ADSCs remains unclear. In this study, we investigated the effect of adding SF from Knee OA patients to cultured ADSCs prepared for therapeutic use in an environment that mimics the joint cavity. An increase in the viability of ADSCs was observed following the addition of SF. Gene expression profiling of SF-treated ADSCs using DNA microarrays revealed changes in several genes involved in cell survival. Of these genes, we focused on FOSL1, which is involved in the therapeutic effect of ADSCs and the survival and proliferation of cancer stem cells. We confirmed the upregulation of FOSL1 mRNA and protein expression using RT-PCR and western blot analysis, respectively. Next, we knocked down FOSL1 in ADSCs using siRNA and observed a decrease in cell viability, indicating the involvement of FOSL1 in the survival of ADSCs. Interestingly, in the knockdown cells, ADSC viability was also decreased by SF exposure. These results suggest that SF enhances cell viability by upregulating FOSL1 expression in ADSCs. For therapy using cultured ADSCs, the therapeutic effect of ADSCs may be further enhanced if an environment more conducive to the upregulation of FOSL1 expression in ADSCs can be established.

Immunomodulation by placenta-derived decidua stromal cells. Role of histocompatibility, accessory cells and freeze-thawing

BACKGROUND AIMS

Human placenta-derived decidua stromal cells (DSCs) are newly introduced stromal cells that have successfully been used in several clinical trials for the treatment of acute inflammatory diseases. Despite published data about DSCs, deeper exploration of mechanisms of action and crosstalk with other immune cells need to be explored.

METHODS

In mixed lymphocyte culture (MLC), the splenocytes from Balb/c or B6 mice were stimulated using mitogen (concanavalin A), allogeneic (B6 or Balb/c splenocytes) or xenogeneic activation with human peripheral blood mononuclear cells.

RESULTS

When 10% of the mouse bone marrow-derived-MSC, being autologous, allogeneic or haploidentical (from F1), was added, >95% inhibition was seen. Using human (h)-DSCs, the inhibitory capacity was a median 68% as a xenogeneic immunomodulatory cell when used in mitogen and allogeneic setting in mice MLC. However, when human peripheral blood mononuclear cells were used as stimulator for mouse splenocyte (xenogeneic MLC), hDSC showed a median inhibition of 88%. We explored the presence and function of monocytes in the immunomodulatory function of stromal cells. CD14+ monocyte cells reduced the immunosuppressive effect by hDSC. hDSCs did not show any inhibitory effect on natural killer cell activation and proliferation by interleukin-2. In contrast DSCs increased natural killer proliferation by a median of 58%. Fresh or frozen-thawed hDSCs had similar inhibitory effects on human T-cell proliferation (both allo-stimulation and mitogen stimulation) in vitro. Cell viability at room temperature during 24 h was similar using fresh or freeze-thawed DSCs.

CONCLUSIONS

To conclude, histocompatibility and CD14+ monocyte cells had an impact on hDSC immunomodulation but frozen-thawed or freshly prepared cells did not.

Extracellular vesicles rejuvenate the microenvironmental modulating function of recipient tissue-specific mesenchymal stem cells in osteopenia treatment

Systemic transplantation of mesenchymal stem cells (MSCs), such as bone marrow MSCs (BMMSCs) and stem cells from human exfoliated deciduous teeth (SHED), is considered a prominent treatment for osteopenia. However, the mechanism of action of the transplanted MSCs has been poorly elucidated. In the recipient target tissue, including bone and bone marrow, only a few donor MSCs can be detected, suggesting that the direct contribution of donor MSCs may not be expected for osteopenia treatment. Meanwhile, secretomes, especially contents within extracellular vesicles (EVs) released from donor MSCs (MSC-EVs), play key roles in the treatment of several diseases. In this context, administrated donor MSC-EVs may affect bone-forming function of recipient cells. In this review, we discuss how MSC-EVs contribute to bone recovery recipient tissue in osteopenia. We also summarize a novel mechanism of action of systemic administration of SHED-derived EVs (SHED-EVs) in osteopenia. We found that reduced telomerase activity in recipient BMMSCs caused the deficiency of microenvironmental modulating function, including bone and bone marrow-like niche formation and immunomodulation in estrogen-deficient osteopenia model mice. Systemic administration of SHED-EVs could exert therapeutic effects on bone reduction via recovering the telomerase activity, leading to the rejuvenation of the microenvironmental modulating function in recipient BMMSCs, as seen in systemic transplantation of SHED. RNase-preconditioned donor SHED-EVs diminished the therapeutic benefits of administrated SHED-EVs in the recipient osteopenia model mice. These facts suggest that MSC-EV therapy targets the recipient BMMSCs to rejuvenate the microenvironmental modulating function via telomerase activity, recovering bone density. We then introduce future challenges to develop the reproducible MSC-EV therapy in osteopenia.

Therapeutic potential of mesenchymal stromal/stem cells in critical-care patients with systemic inflammatory response syndrome

BACKGROUND

Despite notable advances in the support and treatment of patients admitted to the intensive care unit (ICU), the management of those who develop a systemic inflammatory response syndrome (SIRS) still constitutes an unmet medical need.

MAIN BODY

Both the initial injury (trauma, pancreatitis, infections) and the derived uncontrolled response promote a hyperinflammatory status that leads to systemic hypotension, tissue hypoperfusion and multiple organ failure. Mesenchymal stromal/stem cells (MSCs) are emerging as a potential therapy for severe ICU patients due to their potent immunomodulatory, anti-inflammatory, regenerative and systemic homeostasis-regulating properties. MSCs have demonstrated clinical benefits in several inflammatory-based diseases, but their role in SIRS needs to be further explored.

CONCLUSION

In the current review, after briefly overviewing SIRS physiopathology, we explore the potential mechanisms why MSC therapy could aid in the recovery of this condition and the pre-clinical and early clinical evidence generated to date.

Effects of human placenta cryopreservation on molecular characteristics of placental mesenchymal stromal cells

Cryopreservation of placenta tissue for long-term storage provides the opportunity in the future to isolate mesenchymal stromal cells that could be used for cell therapy and regenerative medicine. Despite being widely used, the established cryopreservation protocols for freezing and thawing still raise concerns about their impact on molecular characteristics, such as epigenetic regulation. In our study, we compared the characteristics of human placental mesenchymal stromal cells (hPMSCs) isolated from fresh (native) and cryopreserved (cryo) placenta tissue. We assessed and compared the characteristics of native and cryo hPMSCs such as morphology, metabolic and differentiation potential, expression of cell surface markers, and transcriptome. No significant changes in immunophenotype and differentiation capacity between native and cryo cells were observed. Furthermore, we investigated the epigenetic changes and demonstrated that both native and cryo hPMSCs express only slight variations in the epigenetic profile, including miRNA levels, DNA methylation, and histone modifications. Nevertheless, transcriptome analysis defined the upregulation of early-senescence state-associated genes in hPMSCs after cryopreservation. We also evaluated the ability of hPMSCs to improve pregnancy outcomes in mouse models. Improved pregnancy outcomes in a mouse model confirmed that isolated placental cells both from native and cryo tissue have a positive effect on the restoration of the reproductive system. Still, the native hPMSCs possess better capacity (up to 66%) in comparison with cryo hPMSCs (up to 33%) to restore fertility in mice with premature ovarian failure. Our study demonstrates that placental tissue can be cryopreserved for long-term storage with the possibility to isolate mesenchymal stromal cells that retain characteristics suitable for therapeutic use.

Placenta‐derived mesenchymal stromal cells as a treatment for refractory chronic gingivostomatitis in cats: eight cases (2018)

OBJECTIVES

The aim of this case series was to collect preliminary data on safety and efficacy of treating cats suffering from refractory feline chronic gingivostomatitis with a single intravenous therapy of cryopreserved placenta-derived mesenchymal stromal cells.

MATERIALS AND METHODS

We planned the prospective inclusion of cats suffering from refractory chronic gingivostomatitis in three veterinary clinics. All cats received a single infusion of 10×10⁶ cryopreserved cells. Follow-up evaluations were done at day 15 and at 2-, 3- and 6-months following infusion. Clinical disease severity was evaluated by dental specialists using a published stomatitis disease activity index scoring system coupled with an owners' assessment questionnaire.

RESULTS

All eight cats attended all follow up visits. Cryopreserved ready-to-use placenta-derived cells administered systemically were safe and resulted in notable clinical improvement in all cats as reported by stomatitis disease activity index scoring and owner's survey.

CLINICAL SIGNIFICANCE

Infusion of cryopreserved freshly thawed placenta-derived mesenchymal stromal cells appears to promote clinical and consequently behavioural benefits in cats with refractory chronic gingivostomatitis after having undergone full-mouth or premolar-molar tooth extraction. Future randomised studies are required to confirm safety and efficacy of this treatment.

Cryopreservation does not change the performance and characteristics of allogenic mesenchymal stem cells highly over-expressing a cytoplasmic therapeutic transgene for cancer treatment

Background

Mesenchymal stem cells (MSCs) driven gene directed enzyme prodrug therapy is a promising approach to deliver therapeutic agents to target heterogenous solid tumours. To democratize such a therapy, cryopreservation along with cold chain transportation is an essential part of the logistical process and supply chain. Previously, we have successfully engineered MSCs by a non-viral DNA transfection approach for prolonged and exceptionally high expression of the fused transgene cytosine deaminase, uracil phosphoribosyl transferase and green fluorescent protein (CD::UPRT::GFP). The aim of this study was to determine the effects of cryopreservation of MSCs engineered to highly overexpress this cytoplasmic therapeutic transgene.

Methods

Modified MSCs were preserved in a commercially available, GMP-grade cryopreservative—CryoStor10 (CS10) for up to 11 months. Performance of frozen-modified MSCs was compared to freshly modified equivalents in vitro. Cancer killing potency was evaluated using four different cancer cell lines. Migratory potential was assessed using matrigel invasion assay and flow cytometric analysis for CXCR4 expression. Frozen-modified MSC was used to treat canine patients via intra-tumoral injections, or by intravenous infusion followed by a daily dose of 5-flucytosine (5FC).

Results

We found that cryopreservation did not affect the transgene expression, cell viability, adhesion, phenotypic profile, and migration of gene modified canine adipose tissue derived MSCs. In the presence of 5FC, the thawed and freshly modified MSCs showed comparable cytotoxicity towards one canine and three human cancer cell lines in vitro. These cryopreserved cells were stored for about a year and then used to treat no-option-left canine patients with two different types of cancers and notably, the patients showed progression-free interval of more than 20 months, evidence of the effectiveness in treating spontaneously occurring cancers.

Conclusion

This study supports the use of cryopreserved, off-the-shelf transiently transfected MSCs for cancer treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03198-z.

Adverse events, side effects and complications in mesenchymal stromal cell-based therapies

Numerous clinical studies have shown a wide clinical potential of mesenchymal stromal cells (MSCs) application. However, recent experience has accumulated numerous reports of adverse events and side effects associated with MSCs therapy. Furthermore, the strategies and methods of MSCs therapy did not change significantly in recent decades despite the clinical impact and awareness of potential complications. An extended understanding of limitations could lead to a wider clinical implementation of safe cell therapies and avoid harmful approaches. Therefore, our objective was to summarize the possible negative effects observed during MSCs-based therapies. We were also aimed to discuss the risks caused by weaknesses in cell processing, including isolation, culturing, and storage. Cell processing and cell culture could dramatically influence cell population profile, change protein expression and cell differentiation paving the way for future negative effects. Long-term cell culture led to accumulation of chromosomal abnormalities. Overdosed antibiotics in culture media enhanced the risk of mycoplasma contamination. Clinical trials reported thromboembolism and fibrosis as the most common adverse events of MSCs therapy. Their delayed manifestation generally depends on the patient's individual phenotype and requires specific awareness during the clinical trials with obligatory inclusion in the patient' informed consents. Finally we prepared the safety checklist, recommended for clinical specialists before administration or planning of MSCs therapy.