Multiple infusions of mesenchymal stromal cells induce sustained remission in children with steroid-refractory, grade III-IV acute graft-versus-host disease

Human umbilical cord-derived mesenchymal stromal cells for the treatment of steroid refractory grades III-IV acute graft-versus-host disease with long-term follow-up

Introduction

Mesenchymal stromal cells (MSCs) have been extensively studied as a potential treatment for steroid refractory acute graft-versus-host disease (aGVHD). However, the majority of clinical trials have focused on bone marrow-derived MSCs.

Methods

In this study, we report the outcomes of 86 patients with grade III-IV (82.6% grade IV) steroid refractory aGVHD who were treated with human umbilical cord-derived mesenchymal stromal cells (UC-MSCs). The patient cohort included 17 children and 69 adults. All patients received intravenous infusions of UC-MSCs at a dose of 1 × 106 cells per kg body weight, with a median of 4 infusions (ranging from 1 to 16).

Results

The median time between the onset of aGVHD and the first infusion of UC-MSCs was 7 days (ranging from 3 to 88 days). At day 28, the overall response (OR) rate was 52.3%. Specifically, 24 patients (27.9%) achieved complete remission, while 21 (24.4%) exhibited partial remission. The estimated survival probability at 100 days was 43.7%. Following a median follow-up of 108 months (ranging from 61 to 159 months), the survival rate was approximately 11.6% (10/86). Patients who developed acute lower GI tract and liver GVHD exhibited poorer OR rates at day 28 compared to those with only acute lower GI tract GVHD (22.2% vs. 58.8%; p= 0.049). No patient experienced serious adverse events.

Discussion

These finding suggest that UC-MSCs are safe and effective in both children and adults with steroid refractory aGVHD. UC-MSCs could be considered as a feasible treatment option for this challenging conditon. (NCT01754454).

New investigational drugs for steroid-refractory acute graft-versus-host disease: a review of the literature

INTRODUCTION

Steroid-refractory acute graft-versus-host disease (SR-aGVHD) remains a formidable obstacle in the field of allogeneic hematopoietic cell transplantation (allo-HCT), significantly contributing to patient morbidity and mortality. The current therapeutic landscape for SR-aGVHD is limited, often yielding suboptimal results, thereby emphasizing the urgent need for innovative and effective treatments.

AREAS COVERED

In light of the pivotal REACH2 trial, ruxolitinib phosphate, a Janus kinase inhibitor, has gained prominence as the standard treatment for SR-aGVHD. Nevertheless, a considerable number of patients either do not respond to or cannot tolerate this therapy. This review delves into emerging treatments for SR-aGVHD, including mesenchymal stromal cells (MSCs), fecal microbiota transplantation (FMT), CD3/CD7 blockade, neihulizumab, begelomab, tocilizumab, and vedolizumab. While some of these agents have shown encouraging results in early-phase trials, issues such as treatment-related toxicities and inconsistent responses in larger studies highlight the necessity for ongoing research.

EXPERT OPINION

Current trials exploring new agents and combination therapies offer hope for fulfilling the unmet clinical needs in SR-aGVHD, potentially leading to more effective and precise treatment strategies.

Repeated Infusions of Bone-Marrow-Derived Mesenchymal Stem Cells over 8 Weeks for Steroid-Refractory Chronic Graft-versus-Host Disease: A Prospective, Phase I/II Clinical Study

Chronic graft-versus-host disease (cGVHD) is a long-term complication of allogeneic hematopoietic stem cell transplantation associated with poor quality of life and increased morbidity and mortality. Currently, there are several approved treatments for patients who do not respond to steroids, such as ruxolitinib. Nevertheless, a significant proportion of patients fail second-line treatment, indicating the need for novel approaches. Mesenchymal stem cells (MSCs) have been considered a potential treatment approach for steroid-refractory cGVHD. To evaluate the safety and efficacy of repeated infusions of MSCs, we administered intravenous MSCs every two weeks to ten patients with severe steroid-refractory cGVHD in a prospective phase I clinical trial. Each patient received a total of four doses, with each dose containing 1 × 106 cells/kg body weight from the same donor and same passage. Patients were assessed for their response to treatment using the 2014 National Institutes of Health (NIH) response criteria during each visit. Ten patients with diverse organ involvement were enrolled, collectively undergoing 40 infusions as planned. Remarkably, the MSC infusions were well tolerated without severe adverse events. Eight weeks after the initial MSC infusion, all ten patients showed partial responses characterized by the amelioration of clinical symptoms and enhancement of their quality of life. The overall response rate was 60%, with a complete response rate of 20% and a partial response (PR) rate of 40% at the last follow-up. Overall survival was 80%, with a median follow-up of 381 days. Two patients died due to relapse of their primary disease. Immunological analyses revealed a reduction in inflammatory markers, including Suppression of Tumorigenicity 2 (ST2), C-X-C motif chemokine ligand (CXCL)10, and Secreted phosphoprotein 1(SPP1), following the MSC treatment. Repeated MSC infusions proved to be both feasible and safe, and they may be an effective salvage therapy in patients with steroid-refractory cGVHD. Further large-scale clinical studies with long-term follow-up are needed in the future to determine the role of MSCs in cGVHD.

Extracellular vesicles derived from bovine adipose-derived mesenchymal stromal cells enhance in vitro embryo production from lesioned ovaries

BACKGROUND AND AIMS

Ovum pick-up (OPU) is an intrinsic step of in vitro fertilization procedures. Nevertheless, it can cause ovarian lesions and compromise female fertility in bovines. Recently, we have shown that intraovarian injection of adipose-derived mesenchymal stromal cells (AD-MSCs) effectively preserves ovarian function in bovines. Given that MSC-derived extracellular vesicles (MSC-EVs) have been shown to recapitulate several therapeutic effects attributed to AD-MSCs and that they present logistic and regulatory advantages compared to AD-MSCs, we tested whether MSC-EVs would also be useful to treat OPU-induced lesions.

METHODS

MSC-EVs were isolated from the secretome of bovine AD-MSCs, using ultrafiltration (UF) and ultracentrifugation methods. The MSC-EVs were characterized according to concentration and mean particle size, morphology, protein concentration and EV markers, miRNA, mRNA, long noncoding RNA profile, total RNA yield and potential for induction of the proliferation and migration of bovine ovarian stromal cells. We then investigated whether intraovarian injection of MSC-EVs obtained by UF would reduce the negative effects of acute OPU-induced ovarian lesions in bovines. To do so, 20 animals were divided into 4 experimental groups (n = 5), submitted to 4 OPU cycles and different experimental treatments including vehicle only (G1), MSC-EVs produced by 7.5 × 106 AD-MSCs (G2), MSC-EVs produced by 2.5 × 106 AD-MSCs (G3) or 3 doses of MSC-EVs produced by 2.5 × 106 AD-MSCs, injected after OPU sessions 1, 2 and 3 (G4).

RESULTS

Characterization of the MSC-EVs revealed that the size of the particles was similar in the different isolation methods; however, the UF method generated a greater MSC-EV yield. MSC-EVs processed by both methods demonstrated a similar ability to promote cell migration and proliferation in ovarian stromal cells. Considering the higher yield and lower complexity of the UF method, UF-MSC-EVs were used in the in vivo experiment. We evaluated three therapeutic regimens for cows subjected to OPU, noting that the group treated with three MSC-EV injections (G4) maintained oocyte production and increased in vitro embryo production, compared to G1, which presented compromised embryo production following the OPU-induced lesions.

CONCLUSIONS

MSC-EVs have beneficial effects both on the migration and proliferation of ovarian stromal cells and on the fertility of bovines with follicular puncture injury in vivo.

Mesenchymal stromal cells in the treatment of pediatric hematopoietic cell transplantation-related complications (graft vs. host disease, hemorrhagic cystitis, graft failure and poor graft function): a single center experience

Objectives

To describe mesenchymal stromal cells (MSCs) in the treatment of hematopoietic stem cell transplantation (HSCT) complications and to assess its safety and efficacy.

Methods

Single-center retrospective study (2016-2023). Patients under 20 years who received MSCs for the treatment of HSCT-related complications were included.

Results

Thirty patients (53.7% boys), median age at transplant 11 years (range 2-19) were included. MSCs indications were: graft-vs.-host disease (GVHD) in 18 patients (60%), of them 13 had acute GVHD (43.3%) and 5 chronic GVHD (16.7%); Grade 3-4 hemorrhagic cystitis (HC) in 4 (13.3%); poor graft function (PGF) in 6 (20%), 5 of them receiving MSCs with a CD34 stem cell-boost coinfusion; graft failure (GF) in 2 (6.7%), to enhance engraftment after a subsequent HSCT. Infusion-related-adverse-events were not reported. Overall response (OR) was 83% (25/30); 44% of responders (11/25) showed complete response (CR). OR for GVHD, HC, PGF and GF was 83.3%, 100%, 66.7% and 100% respectively. Response rate was 40% (95% CI: 20-55) and 79% (95% CI: 57-89) at 15 and 30 days. With a median follow-up of 21 months (IQR11-52.5), overall survival (OS) was 86% (95% CI: 74-100) and 79% (95% CI: 65-95) at 6 and 12 months post-MSCs infusion.

Conclusion

In our study, the most frequent indication of MSCs was refractory aGVHD (43.3%). Response rates were high (OR 83%) and safety profile was good.

Cell-based Therapies for Acute Respiratory Distress Syndrome: Where Are We Now?

There is considerable interest in the potential for cell-based therapies, particularly mesenchymal stromal cells (MSCs) and their products, as a therapy for acute respiratory distress syndrome (ARDS). MSCs exert effects via diverse mechanisms including reducing excessive inflammation by modulating neutrophil, macrophage and T-cell function, decreasing pulmonary permeability and lung edema, and promoting tissue repair. Clinical studies indicate that MSCs are safe and well tolerated, with promising therapeutic benefits in specific clinical settings, leading to regulatory approvals of MSCs for specific indications in some countries.This perspective reassesses the therapeutic potential of MSC-based therapies for ARDS given insights from recent cell therapy trials in both COVID-19 and in 'classic' ARDS, and discusses studies in graft-vs.-host disease, one of the few licensed indications for MSC therapies. We identify important unknowns in the current literature, address challenges to clinical translation, and propose an approach to facilitate assessment of the therapeutic promise of MSC-based therapies for ARDS.

Understanding and treatment of cutaneous graft-versus-host-disease

The skin is the outermost mechanical barrier where dynamic immune reactions take place and is the most commonly affected site in both acute and chronic graft-versus-host disease (GVHD). If not properly treated, pain and pruritis resulting from cutaneous GVHD can increase the risk of secondary infection due to erosions, ulcerations, and damage of underlying tissues. Furthermore, resulting disfiguration can cause distress and significantly impact patients' quality of life. Thus, a deeper understanding of skin-specific findings of GVHD is needed. This review will highlight some promising results of recent pre-clinical studies on the pathophysiology of skin GVHD and summarize the diagnostic and staging/grading procedures according to the clinical manifestations of skin GVHD. In addition, we will summarize outcomes of various GVHD treatments, including skin-specific response rates.

Potential optimized route for mesenchymal stem cell transplantation in a rat model of cerebral palsy

Cerebral palsy (CP) is a movement and posture disorder that affects over 50 million people worldwide. Human umbilical cord-derived mesenchymal stem cell (hUC-MSC) transplantation has emerged as an attractive therapeutic strategy for CP. The administration route appears to be crucial for hUC-MSC to provide adequate neuroprotection. Wistar rats were given hypoxia-ischemia to make the CP model on postnatal day 5. On postnatal day 21, DiR-labeled hUC-MSC were transplanted into the CP rats by intravenous, intrathecal, and lateral ventricle for cell tracking. Uninfused CP rats served as the negative control. The motor behavioral and pathological alteration was analyzed 11, 25, and 39 days after transplantation to assess motor function, immune inflammation, neurotrophy, and endogenous repair. In vivo imaging tracking techniques revealed that intravenous infusion resulted in fewer transplanted cells in the target brain than intrathecal and lateral ventricle infusion (p＜0.05). Three different routes of hUC-MSC infusion improved the motor function of CP rats (p＜0.05). At 11 days post-infusion, intrathecal infusion outperformed intravenous with a significant neurotrophic and oligodendrocyte maturation effect (p＜0.05). Intrathecal infusion equaled lateral ventricle infusion after 25 days. At 39 days post-infusion, lateral ventricle infusion exceeded intravenous and intrathecal infusion with a significant immunosuppressive effect (p＜0.05). Considering the improved effect and less trauma shown early in the intrathecal infusion, repeated intrathecal administration may ultimately lead to the greatest benefit.

Treatment of steroid-refractory graft versus host disease in children

Systemic steroids are still the first-line approach in acute graft-versus-host disease (aGvHD), and the backbone of chronic GvHD management. Refractoriness to steroid represent a major cause of morbidity and non-relapse mortality after hematopoietic stem cell transplantation (HSCT). In both backgrounds, several second-line immunosuppressive agents have been tested with variable results in terms of efficacy and toxicity. Solid evidence regarding these approaches is still lacking in the pediatric setting where results are mainly derived from adult experiences. Furthermore, the number of treated patients is limited and the incidence of acute and chronic GvHD is lower, resulting in a very heterogeneous approach to this complication by pediatric hematologists. Some conventional therapies and anti-cytokine monoclonal antibodies used in the adult setting have been evaluated in children. In recent years, the increasing understanding of the biological mechanisms underpinning the pathogenesis of GvHD justified the efforts toward the adoption of targeted therapies and non-pharmacologic approaches, with higher response rates and lower immunosuppressive effects. Moreover, many questions regarding the precise timing and setting in which to integrate these new approaches remain unanswered. This Review aims to critically explore the current evidence regarding novel approaches to treat SR-GvHD in pediatric HSCT recipients.

Development of a Robust Consensus Modeling Approach for Identifying Cellular and Media Metabolites Predictive of Mesenchymal Stromal Cell Potency

Mesenchymal stromal cells (MSCs) have shown promise in regenerative medicine applications due in part to their ability to modulate immune cells. However, MSCs demonstrate significant functional heterogeneity in terms of their immunomodulatory function because of differences in MSC donor/tissue source, as well as non-standardized manufacturing approaches. As MSC metabolism plays a critical role in their ability to expand to therapeutic numbers ex vivo, we comprehensively profiled intracellular and extracellular metabolites throughout the expansion process to identify predictors of immunomodulatory function (T-cell modulation and indoleamine-2,3-dehydrogenase (IDO) activity). Here, we profiled media metabolites in a non-destructive manner through daily sampling and nuclear magnetic resonance (NMR), as well as MSC intracellular metabolites at the end of expansion using mass spectrometry (MS). Using a robust consensus machine learning approach, we were able to identify panels of metabolites predictive of MSC immunomodulatory function for 10 independent MSC lines. This approach consisted of identifying metabolites in 2 or more machine learning models and then building consensus models based on these consensus metabolite panels. Consensus intracellular metabolites with high predictive value included multiple lipid classes (such as phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins) while consensus media metabolites included proline, phenylalanine, and pyruvate. Pathway enrichment identified metabolic pathways significantly associated with MSC function such as sphingolipid signaling and metabolism, arginine and proline metabolism, and autophagy. Overall, this work establishes a generalizable framework for identifying consensus predictive metabolites that predict MSC function, as well as guiding future MSC manufacturing efforts through identification of high-potency MSC lines and metabolic engineering.

A review of the application of mesenchymal stem cells in the field of hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is an effective treatment for many malignant hematological diseases. Mesenchymal stem cells (MSCs) are nonhematopoietic stem cells with strong self-renewal ability and multidirectional differentiation potential. They have the characteristics of hematopoietic support, immune regulation, tissue repair and regeneration, and homing. Recent studies have shown that HSCT combined with MSC infusion can promote the implantation of hematopoietic stem cells and enhance the reconstruction of hematopoietic function. Researchers have also found that MSCs have good preventive and therapeutic effects on acute and chronic graft-versus-host disease (GVHD), but there is still a lack of validation in large-sample randomized controlled trials. When using MSCs clinically, it is necessary to consider their dose, source, application time, application frequency and other relevant factors, but the specific impact of the above factors on the efficacy of MSCs still needs further clinical trial research. This review introduces the clinical roles of MSCs and summarizes the most recent progress concerning the use of MSCs in the field of HSCT, providing references for the later application of the combination of MSCs and HSCT in hematological diseases.

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.

TITLE: New therapeutic approaches in pediatric diseases: Mesenchymal stromal cell and mesenchymal stromal cell-derived extracellular vesicles as new drugs

Mesenchymal Stromal Cell (MSC) clinical applications have been widely reported and their therapeutic potential has been documented in several diseases. MSCs can be isolated from several human tissues and easily expanded in vitro, they are able to differentiate in a variety of cell lineages, and they are known to interact with most immunological cells, showing immunosuppressive and tissue repair properties. Their therapeutic efficacy is closely associated with the release of bioactive molecules, namely Extracellular Vesicles (EVs), effective as their parental cells. EVs isolated from MSCs act by fusing with target cell membrane and releasing their content, showing a great potential for the treatment of injured tissues and organs, and for the modulation of the host immune system. EV-based therapies provide, as major advantages, the possibility to cross the epithelium and blood barrier and their activity is not influenced by the surrounding environment. In the present review, we deal with pre-clinical reports and clinical trials to provide data in support of MSC and EV clinical efficacy with particular focus on neonatal and pediatric diseases. Considering pre-clinical and clinical data so far available, it is likely that cell-based and cell-free therapies could become an important therapeutic approach for the treatment of several pediatric diseases.

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.

Harnessing and honing mesenchymal stem/stromal cells for the amelioration of graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is a deterministic curative procedure for various hematologic disorders and congenital immunodeficiency. Despite its increased use, the mortality rate for patients undergoing this procedure remains high, mainly due to the perceived risk of exacerbating graft-versus-host disease (GVHD). However, even with immunosuppressive agents, some patients still develop GVHD. Advanced mesenchymal stem/stromal cell (MSC) strategies have been proposed to achieve better therapeutic outcomes, given their immunosuppressive potential. However, the efficacy and trial designs have varied among the studies, and some research findings appear contradictory due to the challenges in characterizing the in vivo effects of MSCs. This review aims to provide real insights into this clinical entity, emphasizing diagnostic, and therapeutic considerations and generating pathophysiology hypotheses to identify research avenues. The indications and timing for the clinical application of MSCs are still subject to debate.

Safety and efficacy of mesenchymal stromal cell therapy for multi-drug-resistant acute and late-acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation

Graft versus host disease (GvHD) remains a significant risk for mortality and morbidity following allogeneic hematopoietic stem cell transplantation (HSCT). A growing literature supports successful applications of mesenchymal stromal cells (MSCs) for the treatment of steroid-refractory acute GvHD (aGvHD). However, there is limited knowledge about the effects of MSC treatment on late-acute GvHD (late aGvHD). In this article, we present our multicenter study on the safety and efficacy of MSC therapy for patients with steroid-refractory late aGvHD in comparison to those with aGvHD. The outcome measures include non-relapse mortality (NRM) and survival probability over a 2-year follow-up. The study includes a total of 76 patients with grades III-IV aGvHD (n = 46) or late aGvHD (n = 30), who had been treated with at least two lines of steroid-containing immunosuppressive therapy. Patients received weekly adipose or umbilical cord-derived MSC infusions at a dose of median 1.55 (ranging from 0.84 to 2.56) × 10⁶/kg in the aGvHD group, and 1.64 (ranging from 0.85 to 2.58) × 10⁶/kg in the late aGvHD group. This was an add-on treatment to ongoing conventional pharmaceutical management. In the aGvHD group, 23 patients received one or two infusions, 20 patients had 3-4, and three had ≥ 5. Likewise, in the late aGvHD group, 20 patients received one or two infusions, nine patients had 3-4, and one had ≥ 5. MSC was safe without acute or late adverse effects in 76 patients receiving over 190 infusions. In aGvHD group, 10.9% of the patients had a complete response (CR), 23.9% had a partial response (PR), and 65.2% had no response (NR). On the other hand, in the late aGvHD group, 23.3% of the patients had CR, 36.7% had PR, and the remaining 40% had NR. These findings were statistically significant (p = 0.031). Also, at the 2-year follow-up, the cumulative incidence of NRM was significantly lower in patients with late aGvHD than in patients with aGvHD at 40% (95% CI, 25-62%) versus 71% (95% CI, 59-86%), respectively (p = 0.032). In addition, the probability of survival at 2 years was significantly higher in patients with late aGvHD than in the aGvHD group at 59% (95% CI, 37-74%) versus 28% (95% CI, 13-40%), respectively (p = 0.002). To our knowledge, our study is the first to compare the safety and efficacy of MSC infusion(s) for the treatment of steroid-resistant late aGVHD and aGVHD. There were no infusion-related adverse effects in either group. The response rate to MSC therapy was significantly higher in the late aGvHD group than in the aGvHD group. In addition, at the 2-year follow-up, the survival and NRM rates were more favorable in patients with late aGVHD than in those with aGVHD. Thus, the results are encouraging and warrant further studies to optimize MSC-based treatment for late aGVHD.

International society for cell & gene therapy stem cell engineering committee: Cellular therapies for the treatment of graft-versus-host-disease after hematopoietic stem cell transplant

BACKGROUND AIMS

Allogeneic hematopoietic stem cell transplant is a curative approach for many malignant and non-malignant hematologic conditions. Despite advances in its prevention and treatment, the morbidity and mortality related to graft-versus-host disease (GVHD) remains. The mechanisms by which currently used pharmacologic agents impair the activation and proliferation of potentially alloreactive T cells reveal pathways essential for the detrimental activities of these cell populations. Importantly, these same pathways can be important in mediating the graft-versus-leukemia effect in recipients transplanted for malignant disease. This knowledge informs potential roles for cellular therapies such as mesenchymal stromal cells and regulatory T cells in preventing or treating GVHD. This article reviews the current state of adoptive cellular therapies focused on GVHD treatment.

METHODS

We conducted a search for scientific literature in PubMed® and ongoing clinical trials in clinicaltrial.gov with the keywords "Graft-versus-Host Disease (GVHD)," "Cellular Therapies," "Regulatory T cells (Tregs)," "Mesenchymal Stromal (Stem) Cells (MSCs)," "Natural Killer (NK) Cells," "Myeloid-derived suppressor cells (MDSCs)," and "Regulatory B-Cells (B-regs)." All the published and available clinical studies were included.

RESULTS

Although most of the existing clinical data focus on cellular therapies for GVHD prevention, there are observational and interventional clinical studies that explore the potential for cellular therapies to be safe modalities for GVHD treatment while maintaining the graft-versus-leukemia effect in the context of malignant diseases. However, there are multiple challenges that limit the broader use of these approaches in the clinical scenario.

CONCLUSIONS

There are many ongoing clinical trials to date with the promise to expand our actual knowledge on the role of cellular therapies for GVHD treatment in an attempt to improve GVHD-related outcomes in the near future.

Functional enhancement strategies to potentiate the therapeutic properties of mesenchymal stromal cells for respiratory diseases

Respiratory diseases remain a major health concern worldwide because they subject patients to considerable financial and psychosocial burdens and result in a high rate of morbidity and mortality. Although significant progress has been made in understanding the underlying pathologic mechanisms of severe respiratory diseases, most therapies are supportive, aiming to mitigate symptoms and slow down their progressive course but cannot improve lung function or reverse tissue remodeling. Mesenchymal stromal cells (MSCs) are at the forefront of the regenerative medicine field due to their unique biomedical potential in promoting immunomodulation, anti-inflammatory, anti-apoptotic and antimicrobial activities, and tissue repair in various experimental models. However, despite several years of preclinical research on MSCs, therapeutic outcomes have fallen far short in early-stage clinical trials for respiratory diseases. This limited efficacy has been associated with several factors, such as reduced MSC homing, survival, and infusion in the late course of lung disease. Accordingly, genetic engineering and preconditioning methods have emerged as functional enhancement strategies to potentiate the therapeutic actions of MSCs and thus achieve better clinical outcomes. This narrative review describes various strategies that have been investigated in the experimental setting to functionally potentiate the therapeutic properties of MSCs for respiratory diseases. These include changes in culture conditions, exposure of MSCs to inflammatory environments, pharmacological agents or other substances, and genetic manipulation for enhanced and sustained expression of genes of interest. Future directions and challenges in efficiently translating MSC research into clinical practice are discussed.

A unique immune signature in blood separates therapy-refractory from therapy-responsive acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is an immune cell‒driven, potentially lethal complication of allogeneic hematopoietic stem cell transplantation affecting diverse organs, including the skin, liver, and gastrointestinal (GI) tract. We applied mass cytometry (CyTOF) to dissect circulating myeloid and lymphoid cells in children with severe (grade III-IV) aGVHD treated with immune suppressive drugs alone (first-line therapy) or in combination with mesenchymal stromal cells (MSCs; second-line therapy). These results were compared with CyTOF data generated in children who underwent transplantation with no aGVHD or age-matched healthy control participants. Onset of aGVHD was associated with the appearance of CD11b+CD163+ myeloid cells in the blood and accumulation in the skin and GI tract. Distinct T-cell populations, including TCRγδ+ cells, expressing activation markers and chemokine receptors guiding homing to the skin and GI tract were found in the same blood samples. CXCR3+ T cells released inflammation-promoting factors after overnight stimulation. These results indicate that lymphoid and myeloid compartments are triggered at aGVHD onset. Immunoglobulin M (IgM) presumably class switched, plasmablasts, and 2 distinct CD11b- dendritic cell subsets were other prominent immune populations found early during the course of aGVHD in patients refractory to both first- and second-line (MSC-based) therapy. In these nonresponding patients, effector and regulatory T cells with skin- or gut-homing receptors also remained proportionally high over time, whereas their frequencies declined in therapy responders. Our results underscore the additive value of high-dimensional immune cell profiling for clinical response evaluation, which may assist timely decision-making in the management of severe aGVHD.

Mesenchymal stem cells-derived secretome and extracellular vesicles: perspective and challenges in cancer therapy and clinical applications

Stem cell-based therapies have been foreshowed as a promising therapeutic approach for the treatment of several diseases. However, in the cancer context, results obtained from clinical studies were found to be quite limited. Deeply implicated in inflammatory cues, Mesenchymal, Neural, and Embryonic Stem Cells have mainly been used in clinical trials as a vehicle to deliver and stimulate signals in tumors niche. Although these stem cells have shown some therapeutical promises, they still face several challenges, including their isolation, immunosuppression potential, and tumorigenicity. In addition, regulatory and ethical concerns limit their use in several countries. Mesenchymal stem cells (MSC) have emerged as a gold standard adult stem cell medicine tool due to their distinctive characteristics, such as self-renewal and potency to differentiate into numerous cell types with lower ethical restrictions. Secreted extracellular vesicles (EVs), secretomes, and exosomes play a crucial role in mediating cell-to-cell communication to maintain physiological homeostasis and influence pathogenesis. Due to their low immunogenicity, biodegradability, low toxicity, and ability to transfer bioactive cargoes across biological barriers, EVs and exosomes were considered an alternative to stem cell therapy through their immunological features. MSCs-derived EVs, exosomes, and secretomes showed regenerative, anti-inflammatory, and immunomodulation properties while treating human diseases. In this review, we provide an overview of the paradigm of MSCs derived exosomes, secretome, and EVs cell-free-based therapies, we will focus on MSCs-derived components in anti-cancer treatment with decreased risk of immunogenicity and toxicity. Astute exploration of MSCs may lead to a new opportunity for efficient therapy for patients with cancer.

Allogeneic Mesenchymal Stromal Cells as a Global Pediatric Prospective Approach in the Treatment of Respiratory Failure Associated with Surfactant Protein C Dysfunction

Mesenchymal stromal cells (MSCs) have been proposed as a new therapeutic strategy to treat congenital and acquired respiratory system diseases. We describe a case report of an 18-month-old male patient with progressive chronic respiratory failure, associated with mutations of the surfactant protein C gene (SFTPC) due to c.289G > T variant p.Gly97Ser (rs927644577) and c.176A > G variant (p.His59Arg), submitted to repeated intravenous infusions of allogeneic bone marrow (BM) MSCs. The clinical condition of the patient was monitored. Immunologic studies before and during MSC treatment were performed. No adverse events related to the MSC infusions were recorded. Throughout the MSC treatment period, the patient showed a growth recovery. Starting the second infusion, the patient experienced an improvement in his respiratory condition, with progressive adaptation to mechanical ventilation. After the third infusion, five hours/die of spontaneous breathing was shown, and after infusion IV, spontaneous ventilation for 24/24 h was recorded. A gradual decrease of lymphocytes and cell subpopulations was observed. No variations in the in vitro T cell response to PHA were determined by MSC treatment as well as for the in vitro B cell response. A decrease in IFN-γ, TNF-α, and IL-10 levels was also detected. Even though we cannot exclude an improvement of pulmonary function due to the physiological maturation, the well-known action of MSCs in the repair of lung tissue, together with the sequence of events observed in our patient, may support the therapeutic role of MSCs in this clinical condition. However, further investigations are necessary to confirm the result and long-term follow-up will be mandatory to confirm the benefits on the pulmonary condition.

Efficacy and Safety of Mesenchymal Stromal Cells Therapy for COVID-19 Infection: A Systematic Review and Meta-analysis

BACKGROUND

Coronavirus disease 2019 (COVID-19) is an infectious respiratory disease prevalent worldwide with a high mortality rate, and there is currently no specific medicine to treat patients.

OBJECTIVE

We aimed to assess the safety and efficacy of stem cell therapy for COVID-19 by providing references for subsequent clinical treatments and trials.

METHOD

We systematically searched PubMed, Embase, Cochrane, and Web of Science, using the following keywords: "stem cell" or "stromal cell" and "COVID-19." Controlled clinical trials published in English until 24th August 2021 were included. We followed the PRISMA guidelines and used Cochrane Collaboration's tool for assessing the risk of bias. We analysed the data using a fixed-effect model.

RESULTS

We identified 1779 studies, out of which eight were eligible and included in this study. Eight relevant studies consisted of 156 patients treated with stem cells and 144 controls (300 individuals in total). There were no SAEs associated with stem cell therapy in all six studies, and no significant differences in AEs (p = 0.09, I² = 40%, OR = 0.53, 95% CI: 0.26 to 1.09) between the experimental group and control group were observed. Moreover, the meta-analysis found that stem cell therapy effectively reduced the high mortality rate of COVID-19 (14/156 vs. 43/144; p<0.0001, I2 = 0%, OR=0.18, 95% CI: 0.08 to 0.41).

CONCLUSION

This study suggests that MSCs therapy for COVID-19 has shown some promising results in safety and efficacy. It effectively reduces the high mortality rate of COVID-19 and does not increase the incidence of adverse events.

Mesenchymal stroma/stem cells: Haematologists' friend or foe?

Mesenchymal stromal cells (MSCs) are non-haematopoietic cells found in fetal and adult organs, that play important roles in tissue repair, inflammation and immune modulation. MSCs residing in the bone marrow interact closely with haematopoietic cells and comprise an important component of the microenvironment supporting haematopoiesis, in both health and disease states. Since their identification in 1970, basic scientific and preclinical research efforts have shed light on the role of MSCs in the regulation of haematopoiesis and evoked interest in their clinical application in haematopoietic stem cell transplantation (HSCT) and malignant haematology. Over the last two decades, these research efforts have led to numerous clinical trials, which have established the safety of MSC therapy; however, the optimal mode of administration and the benefit remain inconclusive. In this paper, we will review the clinical experience with use of MSCs in HSCT for enhancement of engraftment, prevention and treatment of graft-versus-host disease and haemorrhagic cystitis. Then, we will discuss the contradictory evidence regarding tumour-promoting versus tumour-suppressing effects of MSCs in haematological malignancies, which may have relevance for future clinical applications.

Human umbilical cord mesenchymal stem cells ameliorate erectile dysfunction in rats with diabetes mellitus through the attenuation of ferroptosis

Background

Erectile dysfunction (ED), as one of the most prevalent consequences in male diabetic patients, has a serious impact on men's physical and mental health, and the treatment effect of diabetic mellitus erectile dysfunction (DMED) is often worse. Therefore, the development of a novel therapeutic approach is urgent. As stem cells with high differentiation potential, human umbilical cord mesenchymal stem cells (HUCMSCs) have been widely used in the treatment of diseases in other systems, and are expected to be a promising strategy for the treatment of DMED. In this study, we investigated the role of HUCMSCs in managing erectile function in rat models of type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) and compared the effects of two different injection methods.

Methods

T1DM and T2DM ED rats were given labelled HUCMSCs by corpus cavernosum injection and tail vein injection, respectively. ICP and MAP were monitored simultaneously by electrical stimulation four weeks after injection to indicate the erectile function of rats. To track the development and colonisation capabilities of stem cells, we performed EdU assay with penile tissue. The histological changes of the penis were observed by hematoxylin–eosin staining, and Masson’s trichrome staining was conducted to evaluate the smooth muscle content and the degree of fibrosis in the rat penis. Then, we employed specific kits to measure the level of NO, cGMP, MDA, SOD and Fe in penis. Electron transmission microscopy was implemented to observe morphology of mitochondria. Besides, western blot and immunofluorescence staining were performed to demonstrate the expression of ferroptosis-related genes.

Results

We found that HUCMSCs improved erectile function in T1DM and T2DM ED rats, with no difference in efficacy between corpus cavernosum injection and tail vein injection. The EdU assay revealed that only a tiny percentage of HUCMSCs colonised the corpus cavernosum, while smooth muscle in the penis expanded and collagen decreased following HUCMSC injection. Moreover, the levels of oxidative stress in the penis of the rats given HUCMSCs were dramatically reduced, as was the tissue iron content. HUCMSCs normalised mitochondrial morphology within corpus cavernosum smooth muscle cells (CCSMCs), which were characteristically altered by high glucose. Furthermore, the expression of ferroptosis inhibitory genes SLC7A11 and GPX4 was obviously elevated in CCSMCs after stem cell management, but the abundances of ACSL4, LPCAT3 and ALOX15 showed the polar opposite tendency.

Conclusions

HUCMSCs can effectively and safely alleviate erectile dysfunction in T1DM and T2DM ED rats, while restoring erectile function by attenuating diabetes-induced ferroptosis in CCSMCs. Additionally, this study provides significant evidence for the development of HUCMSCs as a viable therapeutic strategy for DMED.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03147-w.

CD146 Defines a Mesenchymal Stromal Cell Subpopulation with Enhanced Suppressive Properties

Mesenchymal stromal cells (MSCs) are largely known for their immune-suppressive capacity, hence, their common use in the control of unwanted inflammation. However, novel concepts related to their biology, combined with the urgent need to identify MSC subpopulations with enhanced suppressive properties, drive the search for isolation protocols optimized for clinical applications. We show, in this study, that MSCs expressing high CD146 levels exhibit altered surface expression profiles of CD44 and secrete elevated levels of interleukin (IL)-6, amongst other factors. In addition, CD146^hi MSCs surpass the polyclonal parental populations in inhibiting alloreactive T cells in vitro, in both a soluble- and cell-contact-dependent manner. Despite the lack of CD146^hi MSC-mediated activation of peritoneal macrophages to release the suppressive factor IL-10 in vitro, their administration in animals with graft-versus-host disease alleviates inflammation and leads to 40% survival rate up to 7 weeks post-transplantation. This pronounced inhibitory property is driven by CD146-mediated in situ efferocytosis by myeloid cells. Altogether, this study provides the impetus to adopt an isolation protocol for MSCs based on a CD146 expression profile before their therapeutic use and suggests a major role played by CD146 as a novel “eat-me” signal, capable of enhancing MSC uptake by competent phagocytes.

Is there a role for stem cell therapy in erectile dysfunction secondary to cavernous nerve injury? Network meta-analysis from animal studies and human trials

Introduction:

We carried out systematic review and network meta-analysis to investigate the role of stem cell therapy (SCT) in the management of erectile dysfunction (ED) secondary to cavernous nerve injury in rats and post-radical prostatectomy (RP) in humans.

Patients and Methods:

The protocol was registered with PROSPERO database. We searched studies analyzing the efficacy of SCT for ED due to bilateral cavernous nerve injury (BCNI) in rats using Healthcare Databases Advanced Search (HDAS) Export software (MEDLINE, EMBASE, Scopus) from inception to September 2020. The outcome measurements, for 29 animal studies, were intracavernosal pressure (ICP), ICP/MAP (mean arterial pressure) ratio, and histological/molecular changes. All three available human trials evaluating SCT in post-RP ED were assessed for International Index for Erectile Function (IIEF) Score and Erection Hardness Score (EHS).

Results:

For ICP measurement, animal studies were divided into adipose-derived stem cells (ADSCs) subgroup and bone marrow–derived stem cells (BMSCs) subgroup. Pooled analysis of these studies showed a beneficial effect of SCT in improving erectile function in rats with BCNI using network meta-analysis (95% confidence interval, CI; p < 0.001). There was an increase in ICP/MAP ratio in stem cell groups (including co-intervention) compared with control BCNI group. Histological and molecular evaluation of penile tissue revealed an increase in neuronal nitric oxide synthase (nNOS), smooth muscle content, and anti-apoptotic activity. Human trials revealed improved IIEF (70–150% from baseline at 6 months) and EHS (80–200% from baseline).

Conclusion:

Our results confirm that SCT does improve the erectile function in rats having cavernous nerve injury. Similarly, early human results have shown promising results.

PROSPERO registration ID:

CRD42020201343.

Mesenchymal Stromal Cells for Enhancing Hematopoietic Engraftment and Treatment of Graft-Versus-Host Disease, Hemorrhages and Acute Respiratory Distress Syndrome

Mesenchymal stromal cells (MSCs) possess profound immunomodulatory and regenerative properties that are of clinical use in numerous clinical indications with unmet medical need. Common sources of MSCs include among others, bone marrow (BM), fat, umbilical cord, and placenta-derived decidua stromal cells (DSCs). We here summarize our more than 20-years of scientific experience in the clinical use of MSCs and DSCs in different clinical settings. BM-MSCs were first explored to enhance the engraftment of autografts in hematopoietic cell transplantation (HCT) and osteogenesis imperfecta around 30 years ago. In 2004, our group reported the first anti-inflammatory use of BM-MSCs in a child with grade IV acute graft-versus-host disease (GvHD). Subsequent studies have shown that MSCs appear to be more effective in acute than chronic GvHD. Today BM-MSC-therapy is registered for acute GvHD in Japan and for GvHD in children in Canada and New Zeeland. MSCs first home to the lung following intravenous injection and exert strong local and systemic immunomodulatory effects on the host immune system. Thus, they were studied for ameliorating the cytokine storm in acute respiratory distress syndrome (ARDS). Both, MSCs and DSCs were used to treat SARS-CoV-2 coronavirus-induced disease 2019 (COVID-19)-induced ARDS. In addition, they were also used for other novel indications, such as pneumomediastinum, colon perforation, and radiculomyelopathy. MSC and DSCs trigger coagulation and were thus explored to stop hemorrhages. DSCs appear to be more effective for acute GvHD, ARDS, and hemorrhages, but randomized studies are needed to prove superiority. Stromal cell infusion is safe, well tolerated, and only gives rise to a slight fever in a limited number of patients, but no major side effects have been reported in multiple safety studies and metaanalysis. In this review we summarize current evidence from in vitro studies, animal models, and importantly our clinical experience, to support stromal cell therapy in multiple clinical indications. This encloses MSC's effects on the immune system, coagulation, and their safety and efficacy, which are discussed in relation to prominent clinical trials within the field.

Mesenchymal stromal cells plus basiliximab, calcineurin inhibitor as treatment of steroid-resistant acute graft-versus-host disease: a multicenter, randomized, phase 3, open-label trial

BACKGROUND

Steroid-resistant (SR) acute graft-versus-host disease (aGVHD) lacks standard second-line treatment. Mesenchymal stromal cells (MSCs) have potential efficacy in SR aGVHD. We aimed to assess the efficacy and safety of MSCs combined with basiliximab and calcineurin inhibitor as second-line therapy for SR aGVHD.

METHODS

A randomized phase 3 trial involved 203 SR aGVHD patients at nine centers in China (September 2014-March 2019). Participants were randomized at a 1:1 ratio to receive second-line therapy with (n = 101) or without (n = 102) MSCs. The primary endpoint was the overall response (OR) at day 28. Secondary and safety endpoints included durable OR at day 56, failure-free survival, overall survival (OS), chronic GVHD (cGVHD), infection, hematological toxicity and relapse.

RESULTS

Of 203 patients, 198 (97.5%; mean age, 30.1 years; 40.4% women) completed the study. The OR at day 28 was higher in the MSC group than the control group (82.8% [82 patients] vs. 70.7% [70]; odds ratio, 2.00; 95% confidence interval [CI], 1.01-3.94; P = 0.043). The durable OR at day 56 was also higher in the MSC group (78.8% [78 patients] vs. 64.6% [64]; odds ratio, 2.02; 95% CI, 1.08-3.83; P = 0.027). The median failure-free survival was longer in the MSC group compared with control (11.3 months vs. 6.0 months; hazard ratio (HR) 0.68; 95% CI, 0.48-0.95, P = 0.024). The 2-year cumulative incidence of cGVHD was 39.5% (95% CI, 29.3-49.4%) and 62.7% (51.4-72.1%) in the MSC and control groups (HR 0.55, 95% CI, 0.36-0.84; P = 0.005). Within 180 days after study treatments, the most common grade 3 and 4 adverse events were infections (65 [65.7%] in the MSC group vs. 78 [78.8%] in the control group) and hematological toxicity (37 [37.4%] vs. 53 [53.5%]). The 3-year cumulative incidence of tumor relapse was 10.1% (95% CI, 5.2-17.1) and 13.5% (7.5-21.2%) in the MSC and control groups, respectively (HR 0.75, 95% CI, 0.34-1.67, P = 0.610).

CONCLUSIONS

MSCs plus second-line treatments increase the efficacy of SR aGVHD, decrease drug toxicity of second-line drugs and cGVHD without increasing relapse, and are well-tolerated. MSCs could be recommended as a second-line treatment option for aGVHD patients. Trial registration clinicaltrials.gov identifier: NCT02241018. Registration date: September 16, 2014, https://clinicaltrials.gov/ct2/show/NCT02241018 .

Current status of clinical trials assessing mesenchymal stem cell therapy for graft versus host disease: a systematic review

Background

Graft-versus-host disease (GVHD) is a common fatal complication of hematopoietic stem cell transplantation (HSCT), where steroids are used as a treatment option. However, there are currently no second-line treatments for patients that develop steroid-resistance (SR). Mesenchymal stem cells (MSCs) have immunomodulatory functions and can exert immunosuppressive effects on the inflammatory microenvironment. A large number of in vitro experiments have confirmed that MSCs can significantly inhibit the proliferation or activation of innate and adaptive immune cells. In a mouse model of GVHD, MSCs improved weight loss and increased survival rate. Therefore, there is great promise for the clinical translation of MSCs for the prevention or treatment of GVHD, and several clinical trials have already been conducted to date.

Main body

In this study, we searched multiple databases and found 79 clinical trials involving the use of MSCs to prevent or treat GVHD and summarized the characteristics of these clinical trials, including study design, phase, status, and locations. We analyzed the results of these clinical trials, including the response and survival rates, to enable researchers to obtain a comprehensive understanding of the field’s progress, challenges, limitations, and future development trends. Additionally, factors that might result in inconsistencies in clinical trial results were discussed.

Conclusion

In this study, we attempted to analyze the clinical trials for MSCs in GVHD, identify the most suitable group of patients for MSC therapy, and provide a new perspective for the design of such trials in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02751-0.

New Perspectives to Improve Mesenchymal Stem Cell Therapies for Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is one of the leading causes of acute liver injury. Many factors may contribute to the susceptibility of patients to this condition, making DILI a global medical problem that has an impact on public health and the pharmaceutical industry. The use of mesenchymal stem cells (MSCs) has been at the forefront of regenerative medicine therapies for many years, including MSCs for the treatment of liver diseases. However, there is currently a huge gap between these experimental approaches and their application in clinical practice. In this concise review, we focus on the pathophysiology of DILI and highlight new experimental approaches conceived to improve cell-based therapy by the in vitro preconditioning of MSCs and/or the use of cell-free products as treatment for this liver condition. Finally, we discuss the advantages of new approaches, but also the current challenges that must be addressed in order to develop safer and more effective procedures that will allow cell-based therapies to reach clinical practice, enhancing the quality of life and prolonging the survival time of patients with DILI.

A comprehensive report of long-term stability data for a range ATMPs: A need to develop guidelines for safe and harmonized stability studies

BACKGROUND AIMS

Advanced therapy medicinal products (ATMPs) are novel drugs based on genes, cells or tissues developed to treat many different diseases. Stability studies of each new ATMP need to be performed to define its shelf life and guarantee efficacy and safety upon infusion, and these are presently based on guidelines originally drafted for standard pharmaceutical drugs, which have properties and are stored in conditions quite different from cell products. The aim of this report is to provide evidence-based information for stability studies on ATMPs that will facilitate the interlaboratory harmonization of practices in this area.

METHODS

We have collected and analyzed the results of stability studies on 19 different cell-based experimental ATMPs, produced by five authorized cell factories forming the Lombardy "Plagencell network" for use in 36 approved phase I/II clinical trials; most were cryopreserved and stored in liquid nitrogen vapors for 1 to 13 years.

RESULTS

The cell attributes collected in stability studies included cell viability, immunophenotype and potency assays, in particular immunosuppression, cytotoxicity, cytokine release and proliferation/differentiation capacity. Microbiological attributes including sterility, endotoxin levels and mycoplasma contamination were also analyzed. All drug products (DPs), cryopreserved in various excipients containing 10% DMSO and in different primary containers, were very stable long term at <-150°C and did not show any tendency for diminished viability or efficacy for up to 13.5 years.

CONCLUSIONS

Our data indicate that new guidelines for stability studies, specific for ATMPs and based on risk analyses, should be drafted to harmonize practices, significantly reduce the costs of stability studies without diminishing safety. Some specific suggestions are presented in the discussion.

Therapeutic Mesenchymal Stem/Stromal Cells: Value, Challenges and Optimization

Cellular therapy aims to replace damaged resident cells by restoring cellular and molecular environments suitable for tissue repair and regeneration. Among several candidates, mesenchymal stem/stromal cells (MSCs) represent a critical component of stromal niches known to be involved in tissue homeostasis. In vitro, MSCs appear as fibroblast-like plastic adherent cells regardless of the tissue source. The therapeutic value of MSCs is being explored in several conditions, including immunological, inflammatory and degenerative diseases, as well as cancer. An improved understanding of their origin and function would facilitate their clinical use. The stemness of MSCs is still debated and requires further study. Several terms have been used to designate MSCs, although consensual nomenclature has yet to be determined. The presence of distinct markers may facilitate the identification and isolation of specific subpopulations of MSCs. Regarding their therapeutic properties, the mechanisms underlying their immune and trophic effects imply the secretion of various mediators rather than direct cellular contact. These mediators can be packaged in extracellular vesicles, thus paving the way to exploit therapeutic cell-free products derived from MSCs. Of importance, the function of MSCs and their secretome are significantly sensitive to their environment. Several features, such as culture conditions, delivery method, therapeutic dose and the immunobiology of MSCs, may influence their clinical outcomes. In this review, we will summarize recent findings related to MSC properties. We will also discuss the main preclinical and clinical challenges that may influence the therapeutic value of MSCs and discuss some optimization strategies.

OUP accepted manuscript

Graft versus host disease (GVHD) is a severe complication after allogenic hematopoietic cell transplantation (HSCT). Several clinical trials have reported the use of mesenchymal stromal cells (MSCs) for the treatment of GVHD. In March 2008, the Andalusian Health Care System launched a compassionate use program to treat steroid-resistant GVHD with MSC. Clinical-grade MSC were obtained under GMP conditions. MSC therapy was administered intravenously in four separate doses of 1 × 10⁶ cells/kg. Sixty-two patients, 45 males (7 children) and 17 females (2 children), received the treatment. Patients had a median age of 39 years (range: 7–66) at the time of the allogenic HSCT. The overall response was achieved in 58.7% of patients with acute (a)GVHD. Two years’ survival for aGVHD responders was 51.85%. The overall response for patients with chronic (c)GVHD was 65.50% and the 2-year survival rate for responders was 70%. Age at the time of HSCT was the only predictor found to be inversely correlated with survival in aGVHD. Regarding safety, four adverse events were reported, all recovered without sequelae. Thus, analysis of this compassionate use experience shows MSC to be an effective and safe therapeutic option for treating refractory GVHD, resulting in a significant proportion of patients responding to the therapy.

Protective and pathological roles of regulatory immune cells in human cytomegalovirus infection following hematopoietic stem cell transplantation

Human cytomegalovirus (HCMV) is ubiquitously prevalent. Immune system in healthy individuals is capable of controlling HCMV infection; however, HCMV can be life-threatening for immunocompromised individuals, such as transplant recipients. Both innate and adaptive immune systems are critically involved in the HCMV infection. Recent studies have indicated that regulatory immune cells which play essential roles in maintaining a healthy immune environment are closely related to immune response in HCMV infection. However, the exact role of regulatory immune cells in immune regulation and homoeostasis during the battle between HCMV and host still requires further research. In this review, we highlight the protective and pathological roles of regulatory immune cells in HCMV infection following hematopoietic stem cell transplantation (HSCT).

Mesenchymal Stromal Cells for the Treatment of Graft Versus Host Disease

Graft versus host disease (GvHD) is a life-threating complication of allogeneic hematopoietic stem cell transplantation, which is initially treated with high dose corticosteroids. Approximately 50% of acute GvHD cases are resistant to steroid treatment, and two-year mortality rates in those steroid-resistant patients exceed 80%. Chronic GvHD necessitates prolonged corticosteroid use, which is typically associated with limited efficacy and troublesome adverse effects. No agent has yet been established as an optimal second line therapy for either acute or chronic GvHD, but mesenchymal stromal cells (MSCs) have shown substantial promise. MSCs promote an immunosuppressive and immunoregulatory environment via multifactorial mechanisms, including: secretion of proteins/peptides/hormones; transfer of mitochondria; and transfer of exosomes or microvesicles containing RNA and other molecules. A large number of clinical studies have investigated MSCs from various sources as a treatment for acute and/or chronic GvHD. MSCs are generally safe and well tolerated, and most clinical studies have generated encouraging efficacy results, but response rates have varied. Confounding factors include variability in MSC donor types, production methodology and dose regimens, as well as variations in study design. It is well-established that extensive culture expansion of primary donor-derived MSCs leads to marked changes in functionality, and that there is a high level of inter-donor variability in MSC properties. However, recent manufacturing innovations may be capable of overcoming these problems. Further adequately powered prospective studies are required to confirm efficacy and establish the place of MSC therapy in the treatment of this condition.

Mesenchymal stromal cells in wound healing applications: role of the secretome, targeted delivery and impact on recessive dystrophic epidermolysis bullosa treatment

Mesenchymal stromal cells (MSCs) are multi-potent stromal-derived cells capable of self-renewal that possess several advantageous properties for wound healing, making them of interest to the field of dermatology. Research has focused on characterizing the unique properties of MSCs, which broadly revolve around their regenerative and more recently discovered immunomodulatory capacities. Because of ease of harvesting and expansion, differentiation potential and low immunogenicity, MSCs have been leading candidates for tissue engineering and regenerative medicine applications for wound healing, yet results from clinical studies have been variable, and promising pre-clinical work has been difficult to reproduce. Therefore, the specific mechanisms of how MSCs influence the local microenvironment in distinct wound etiologies warrant further research. Of specific interest in MSC-mediated healing is harnessing the secretome, which is composed of components known to positively influence wound healing. Molecules released by the MSC secretome can promote re-epithelialization and angiogenesis while inhibiting fibrosis and microbial invasion. This review focuses on the therapeutic interest in MSCs with regard to wound healing applications, including burns and diabetic ulcers, with specific attention to the genetic skin disease recessive dystrophic epidermolysis bullosa. This review also compares various delivery methods to support skin regeneration in the hopes of combating the poor engraftment of MSCs after delivery, which is one of the major pitfalls in clinical studies utilizing MSCs.

Dissecting the relationship between antimicrobial peptides and mesenchymal stem cells

Among the various biological properties presented by Mesenchymal Stem Cells (MSCs), their ability to control the immune response and fight pathogen infection through the production of antimicrobial peptides (AMPs) have been the subject of intense research in recent years. AMPs secreted by MSCs exhibit activity against a wide range of microorganisms, including bacteria, fungi, yeasts, and viruses. The main AMPs produced by these cells are hepcidin, cathelicidin LL-37, and β-defensin-2. In addition to acting against pathogens, those AMPs have also been shown to interact with MSCs to modulate MSC proliferation, migration, and regeneration, indicating that such peptides exert a more diverse biological effect than initially thought. In the present review, we discuss the production of AMPs by MSCs, revise the multiple functions of these peptides, including their influence over MSCs, and present an overview of clinical situations in which the antimicrobial properties of MSCs may be explored for therapy. Finally, we discuss possibilities of combining MSCs and AMPs to generate improved therapeutic strategies.

Mesenchymal stromal cells: Putative microenvironmental modulators become cell therapy

An exceptional safety profile has been shown in a large number of cell therapy clinical trials that use mesenchymal stromal cells (MSCs). However, reliable potency assays are still lacking to predict MSC immunosuppressive efficacy in the clinical setting. Nevertheless, MSCs are approved in Japan and Europe for the treatment of graft-versus-host and Crohn's fistular diseases, but not in the United States for any clinical indication. We discuss potential mechanisms of action for the therapeutic effects of MSC transplantation, experimental models that dissect tissue modulating function of MSCs, and approaches for identifying MSC effects in vivo by integrating biomarkers of disease and MSC activity.

Challenges, highlights, and opportunities in cellular transplantation: A white paper of the current landscape

Although cellular transplantation remains a relatively small field compared to solid organ transplantation, the prospects for advancement in basic science and clinical care remain bountiful. In this review, notable historical events and the current landscape of the field of cellular transplantation are reviewed with an emphasis on islets (allo- and xeno-), hepatocytes (including bioartificial liver), adoptive regulatory immunotherapy, and stem cells (SCs, specifically endogenous organ-specific and mesenchymal). Also, the nascent but rapidly evolving field of three-dimensional bioprinting is highlighted, including its major processing steps and latest achievements. To reach its full potential where cellular transplants are a more viable alternative than solid organ transplants, fundamental change in how the field is regulated and advanced is needed. Greater public and private investment in the development of cellular transplantation is required. Furthermore, consistent with the call of multiple national transplant societies for allo-islet transplants, the oversight of cellular transplants should mirror that of solid organ transplants and not be classified under the unsustainable, outdated model that requires licensing as a drug with the Food and Drug Administration. Cellular transplantation has the potential to bring profound benefit through progress in bioengineering and regenerative medicine, limiting immunosuppression-related toxicity, and providing markedly reduced surgical morbidity.

Off-the-shelf bone marrow-derived mesenchymal stem cell treatment for acute graft-versus-host disease: real-world evidence

Temcell is a cryopreserved, human bone marrow-derived mesenchymal stem cell (MSC) product approved for the treatment of patients of all ages with acute graft-versus-host disease (GVHD). Initial experience with Temcell in a real-world setting from a cellular therapy registry in Japan is presented. A total of 381 consecutive patients were enrolled since its approval in 2016. The median cell number infused was 2.00 × 106/kg. The most common number of infusions was 8 in 100 patients. Of the 306 evaluable patients, the overall response rate (ORR) on day 28 after the start of MSC therapy was 56%. Of the 151 evaluable patients who received it as second-line therapy following first-line steroid therapy for classic acute GVHD, the ORR was 61%. Liver involvement of GVHD and ≥14 days from first-line steroid therapy to second-line MSC therapy was associated with a lower ORR. Day 28 ORR, patient age, GVHD grade, GVHD organ involvement, and a number of GVHD therapies before MSC therapy were associated with nonrelapse mortality. Overall survival at 6 months in 381 patients was 40%. This study suggests that Temcell is one of the treatment options for steroid-refractory acute GVHD until a new treatment with survival benefit is developed.

Characterization of Bone Marrow Progenitor Cell Uterine Engraftment and Transdifferentiation

Regeneration of uterine tissue is an important physiological process that allows for maintenance of fertility after menstruation or pregnancy. Stem cells, especially bone marrow-derived progenitors, play a crucial role in this regeneration. Here, we describe the conversion of DsRed-labeled bone marrow-derived stem cells (BMDSCs) into specific uterine cell types with both differentiated and stem cell properties in a murine model. Irradiated recipient mice underwent bone marrow transplant with DsRed-expressing BMDSCs and were analyzed for engraftment and differentiation of BMDSCs in the uterus after 2, 6, and 16 weeks. Microarray and qRT-PCR analysis of bone marrow-derived cells obtained from the uterus identified upregulation of markers indicating a contribution to the population of stromal, epithelial, endothelial, and muscle cells, followed by a late expansion of epithelial cells. Other engrafted BMDSCs in the uterus were characterized by the continued expression of specific stem cell markers such as Sca1, CD44, CD146, and CD133, indicating the some BMDSCs remain as progenitor cells. BMDSCs established in recipient mice by the 16th week were sorted by flow cytometry using DsRed and progenitor cell surface markers. In vitro cell culture studies showed that single sorted cells had clonogenic properties. These results suggest that engrafted BMDSCs in the uterus had both a stem cell component and were able to differentiate into several differentiated cell types. The pool of progenitor cells likely continues to supply differentiated uterine cells in the process of uterine repair and remodeling.

Treatment of Steroid-Refractory Acute Graft-Versus-Host Disease Using Commercial Mesenchymal Stem Cell Products

Acute graft-versus-host disease (GVHD) is a life-threatening complication that can develop after allogeneic hematopoietic stem cell transplantation. In particular, the prognosis of patients with steroid-refractory acute GVHD is extremely poor. Ryoncil™ (remestemcel-L), a human bone marrow-derived mesenchymal stem cell (MSC) product, failed to show superiority over placebo in patients with steroid-refractory acute GVHD, but it was approved for use in pediatric patients in Canada and New Zealand based on the results of a subgroup analysis. Temcell^®, an equivalent manufactured MSC product to remestemcel-L, was approved in Japan based on small single-arm studies by using a regulation for regenerative medicine in 2016. The efficacy of Temcell was evaluated in 381 consecutive patients treated with Temcell during the initial 3 years after its approval. Interestingly, its real-world efficacy was found to be equivalent to that observed in a prospective study of remestemcel-L with strict eligibility criteria. In this article, the potential of MSC therapy in the treatment of acute GVHD is discussed. A meticulous comparison of studies of remestemcel-L and Temcell, remestemcel-L/Temcell and ruxolitinib, and remestemcel-L/Temcell and thymoglobulin showed that the precise position of remestemcel-L/Temcell therapy in the treatment of acute GVHD remains to be determined.

Infusion of Mesenchymal Stem Cells to Treat Graft Versus Host Disease: the Role of HLA-G and the Impact of its Polymorphisms

Hematopoietic stem-cell transplantation is widely performed for the treatment of hematologic diseases and is increasingly being used for the experimental treatment of various autoimmune diseases. Despite the rapid evolution of this therapy, the mortality rate of patients undergoing this procedure is still high, mainly due to the development of graft versus host disease (GvHD). Even with the administration of immunosuppressive therapy, some patients manifest the chronic form of the disease. For these cases, infusion of mesenchymal stem cells (MSCs) was proposed as a therapeutic strategy, considering the immunosuppressive potential of these cells. This review describes the main results obtained in cell therapy with MSCs for the treatment of GvHD. Despite the encouraging results found, some points differed among the studies. Although the factors that influence the different results are uncertain, some investigators have suggested that variations in immunosuppressive molecules are responsible for these divergences. We highlight the key role of the HLA-G gene in modulating the immune response, and the importance of the polymorphisms and alleles of this gene associated with the outcome of the transplants. We suggest that the HLA-G gene and its polymorphisms be analyzed as a factor in selecting the MSCs to be used in treating GvHD, given its strong immunosuppressive role.

Reduction of Graft-versus-Host-Disease in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) Mice by Cotransplantation of Syngeneic Human Umbilical Cord-Derived Mesenchymal Stromal Cells

Graft-versus-host disease (GVHD) is one of the major complications following hematopoietic stem cell transplantation, which remains the sole curative therapy for many malignant diseases of the hematopoietic system. The immunomodulatory potential of mesenchymal stromal cells (MSCs) to treat GVHD is currently being tested in various preclinical and clinical trials. Because the results of the preclinical and clinical trials on the use of MSCs to treat GVHD have not been consistent, we analyzed the potential beneficial effects of syngeneic versus allogenic treatment, culture expansion of MSCs, and various MSC cell doses and time points of MSC transplantation in a murine GVHD model. We established the murine GVHD model based on the transplantation of umbilical cord blood-derived hematopoietic stem cells (UC-HSCs) and used this model to assess the therapeutic potential of umbilical cord blood-derived MSCs (UC-MSCs). The use of HSC and MSC populations derived from the same donor allowed us to exclude third-party cells and test the UC-HSCs and UC-MSCs in a matched setting. Moreover, we were able to compare various doses, transplantation time points, and the influence of culture expansion of MSCs on the impact of treatment. This resulted in 16 different treatment groups. The most efficient setting for treatment of UC-HSC-induced GVHD reactions was based on the simultaneous administration of 1 × 10⁶ culture-expanded, syngeneically matched UC-MSCs. This therapy effectively reduced the number of CD8⁺ T cells in the blood, protected the mice from weight loss, and prolonged their survival until the end of observation period. Taken together, our data show beneficial effects of (1) syngeneic over allogeneic UC-HSCs and UC-MSCs, (2) culture-expanded cells over freshly isolated primary cells, (3) simultaneous over sequential administration, and (4) high doses of UC-MSCs. The animal model of GVHD established here is now available for more detailed studies, including a comparative analysis of the efficacy of MSCs derived from alternative sources, such as adipose tissue and bone marrow.

Research Progress on Strategies that can Enhance the Therapeutic Benefits of Mesenchymal Stromal Cells in Respiratory Diseases With a Specific Focus on Acute Respiratory Distress Syndrome and Other Inflammatory Lung Diseases

Recent advances in cell based therapies for lung diseases and critical illnesses offer significant promise. Despite encouraging preclinical results, the translation of efficacy to the clinical settings have not been successful. One of the possible reasons for this is the lack of understanding of the complex interaction between mesenchymal stromal cells (MSCs) and the host environment. Other challenges for MSC cell therapies include cell sources, dosing, disease target, donor variability, and cell product manufacturing. Here we provide an overview on advances and current issues with a focus on MSC-based cell therapies for inflammatory acute respiratory distress syndrome varieties and other inflammatory lung diseases.

Extended Treatment With Mesenchymal Stromal Cells-Frankfurt am Main in a Pediatric Patient With Steroid-refractory Acute Gastrointestinal Graft-Versus-Host Disease: Case Report and Review of the Literature

In acute graft-versus-host disease (aGVHD) following allogeneic hematopoietic stem cell transplantation, there are various options available after the failure of initial steroid therapy. Since the publication of the first study in 2008, mesenchymal stromal cells (MSCs) have also been used with increasing frequency, including in pediatric patients with steroid-refractory aGVHD, and the manufacturing process has undergone further development. MSC-Frankfurt am Main (MSC-FFM, Obnitix), which is manufactured from pooled mononuclear bone marrow cells from 8 donors using a standardized process, resulted in a response rate of 84% in children with steroid-refractory aGVHD. We report on a 13-year-old female patient with acute myeloid leukemia who received Obnitix as a third-line treatment for gastrointestinal (GI) aGVHD in a life-threatening situation. The patient was initially given a total of 4 Obnitix infusions as per the regulatory approval, with her symptoms improving from day 9 after the first infusion. The second cycle of 4 Obnitix infusions followed due to persistent severe protein-losing enteropathy and resulted in complete remission. A systematic review of the literature on MSC in pediatric patients with steroid-refractory aGVHD confirms that MSC treatment beyond 4 weeks is employed in accordance with treatment protocols or on a case-by-case basis. To summarize, aGVHD activity can be checked endoscopically in patients with persistent GI symptoms and a second Obnitix cycle can then be administered if appropriate, with the goal of achieving complete remission. Future studies should also investigate the potential influence of tissue repair properties as an element in MSCs' efficacy in GI aGVHD.

A Large-Scale Bank of Organ Donor Bone Marrow and Matched Mesenchymal Stem Cells for Promoting Immunomodulation and Transplant Tolerance

Induction of immune tolerance for solid organ and vascular composite allografts is the Holy Grail for transplantation medicine. This would obviate the need for life-long immunosuppression which is associated with serious adverse outcomes, such as infections, cancers, and renal failure. Currently the most promising means of tolerance induction is through establishing a mixed chimeric state by transplantation of donor hematopoietic stem cells; however, with the exception of living donor renal transplantation, the mixed chimerism approach has not achieved durable immune tolerance on a large scale in preclinical or clinical trials with other solid organs or vascular composite allotransplants (VCA). Ossium Health has established a bank of cryopreserved bone marrow (BM), termed "hematopoietic progenitor cell (HPC), Marrow," recovered from deceased organ donor vertebral bodies. This new source for hematopoietic cell transplant will be a valuable resource for treating hematological malignancies as well as for inducing transplant tolerance. In addition, we have discovered and developed a large source of mesenchymal stem (stromal) cells (MSC) tightly associated with the vertebral body bone fragment byproduct of the HPC, Marrow recovery process. Thus, these vertebral bone adherent MSC (vBA-MSC) are matched to the banked BM obtained from each donor, as opposed to third-party MSC, which enhances safety and potentially efficacy. Isolation and characterization of vBA-MSC from over 30 donors has demonstrated that the cells are no different than traditional BM-MSC; however, their abundance is >1,000-fold higher than obtainable from living donor BM aspirates. Based on our own unpublished data as well as reports published by others, MSC facilitate chimerism, especially at limiting hematopoietic stem and progenitor cell (HSPC) numbers and increase safety by controlling and/or preventing graft-vs.-host-disease (GvHD). Thus, vBA-MSC have the potential to facilitate mixed chimerism, promote complementary peripheral immunomodulatory functions and increase safety of BM infusions. Both HPC, Marrow and vBA-MSC have potential use in current VCA and solid organ transplant (SOT) tolerance clinical protocols that are amenable to "delayed tolerance." Current trials with HPC, Marrow are planned with subsequent phases to include vBA-MSC for tolerance of both VCA and SOT.

Erectile Dysfunction Treatment Using Stem Cells: A Review

Erectile dysfunction (ED) is a disorder that affects the quality of life and the sexual relations of more than half of the male population aged over 40 years. The prediction regarding the incidence of ED is devastating as it is expected that this disorder will affect more than 300 million men in the next five years. Several studies have suggested the use of stem cells for the treatment of ED and showed that this type of treatment is promising in terms of damaged tissue repair as well as of clinical efficacy; however, there are several gaps in the knowledge and evidence is lacking. In order to highlight a few of them in this review, we performed a research of the literature focusing on currently available clinical studies regarding the clinical efficacy of stem cell administration for the treatment of ED. We reviewed the methods of administration, the cell types used in the performed clinical trials and the safety and efficiency of such procedures. We conclude that there are rapidly expanding and promising results from the reported clinical studies indicating that stem cells could indeed be a potential treatment for patients with ED although more studies are necessary.