Investigational Use of Mesenchymal Stem/Stromal Cells and Their Secretome as Add-On Therapy in Severe Respiratory Virus Infections: Challenges and Perspectives.

Serious manifestations of respiratory virus infections such as influenza and coronavirus disease 2019 (COVID-19) are associated with a dysregulated immune response and systemic inflammation. Treating the immunological/inflammatory dysfunction with glucocorticoids, Janus kinase inhibitors, and monoclonal antibodies against the interleukin-6 receptor has significantly reduced the risk of respiratory failure and death in hospitalized patients with severe COVID-19, but the proportion of those requiring invasive mechanical ventilation (IMV) and dying because of respiratory failure remains elevated. Treatment of severe influenza-associated pneumonia and acute respiratory distress syndrome (ARDS) with available immunomodulators and anti-inflammatory compounds is still not recommended. New therapies are therefore needed to reduce the use of IMV and the risk of death in hospitalized patients with rapidly increasing oxygen demand and systemic inflammation who do not respond to the current standard of care. This paper provides a critical assessment of the published clinical trials that have tested the investigational use of intravenously administered allogeneic mesenchymal stem/stromal cells (MSCs) and MSC-derived secretome with putative immunomodulatory/antiinflammatory/regenerative properties as add-on therapy to improve the outcome of these patients. Increased survival rates are reported in 5 of 12 placebo-controlled or open-label comparative trials involving patients with severe and critical COVID-19 and in the only study concerning patients with influenza-associated ARDS. Results are encouraging but inconclusive for the following reasons: small number of patients tested in each trial; differences in concomitant treatments and respiratory support; imbalances between study arms; differences in MSC source, MSC-derived product, dosing and starting time of the investigational therapy; insufficient/inappropriate reporting of clinical data. Solutions are proposed for improving the clinical development plan, with the aim of facilitating regulatory approval of the MSC-based investigational therapy for life-threatening respiratory virus infections in the future. Major issues are the absence of a biomarker predicting responsiveness to MSCs and MSC-derived secretome and the lack of pharmacoeconomic evaluations.

Mesenchymal Stem/Stromal Cells: INTERIM REPORT FROM THE NEPHSTROM MULTI-CENTRE, RANDOMISED, DOUBLE-BLIND, PLACEBO-CONTROLLED PHASE-1B CLINICAL TRIAL OF A NOVEL MESENCHYMAL STROMAL CELL THERAPY IN PROGRESSIVE DIABETIC KIDNEY DISEASE

Background & Aim: Funded in 2015, the NEPHSTROM EU-H2020 consortium aimed to translate pre-clinical evidence of efficacy of “off-the-shelf” intravenous (i.v.) allogeneic mesenchymal stromal cells (allo-MSC) in diabetic nephropathy to early-phase clinical investigation in patients with progressive diabetic kidney disease (DKD). Methods, Results & Conclusion: Methods: The trial IMP, NEPHSTROM ORBCEL-M, consists of cryopreserved, CD362-selected bone marrow allo-MSCs or matching placebo (cryopreservation fluid). The protocol for a multi-site, randomised, placebo-controlled, double- blind, dose-escalation phase-1b clinical trial in adults with DKD due to type 2 diabetes was designed collaboratively by a group of academic nephrologists and cell therapy specialists from Italy, the UK, Ireland and the Netherlands. Inclusion criteria included age 40-85 yrs and type 2 diabetes with evidence of progressive DKD [eGFR 25- 55mL/min/1.73m2, urine albumin creatinine ratio >88mg/g and rapid eGFR decline or ≥15% risk of ESRD within 5 years]. Three dose cohorts were planned, each with n=12 NEPHSTROM ORBCEL-M recipients + n=4 Placebo recipients and 18 months follow-up. Results: Following regulatory approval of the trial dossier through the EMA’s Voluntary Harmonisation Procedure and ethical approvals at the Sponsor site (Bergamo, Italy) and three other sites (Galway, Ireland;Birmingham and Belfast, UK), the NEPHSTROM trial (NCT02585622) opened March 2018. To date, 27 patients have been treated and 14 have completed the trial protocol. We report here our (as-yet blinded) experiences with the first fixed-dose cohort (80x10e6 cells/placebo i.v.), consisting of 16 subjects enrolled at 3 sites and followed for 18 months. The trial intervention proved safe, with one quickly-resolved infusion reaction and no subsequent SAEs ascribed to the IMP. Two patients died of unrelated causes between 12 and 18 months. Serial serum assays for anti-HLA antibodies indicated no persistent allo-immune sensitisation. NEPHSTROM ORBCEL-M effects on trends in eGFR, true GFR (iohexol clearance), albuminuria, serum/plasma inflammatory biomarkers and immune cell profiles will be analysed after unblinding. Following DSMB approval and COVID-19-related trial pauses, 11 second dose cohort subjects (160x10e6 cells/placebo i.v.) have been treated and are undergoing follow-up with no IMP-related adverse events to date. Conclusion: A novel, off-the-shelf, i.v. allo-MSC IMP has thus far proven safe and feasible in adults with progressive DKD.

The clinical efficacy and safety of mesenchymal stromal cells for patients with COVID-19: A systematic review and meta-analysis of randomized controlled trials.

OBJECTIVES: This meta-analysis of randomized controlled trials (RCTs) investigated the usefulness of mesenchymal stromal cells (MSCs) to treat patients with COVID-19. METHODS: PubMed, Embase, Ovid MEDLINE, the Cochrane Library, and Clinicaltrials.gov were searched for RCTs published before November 7, 2021. Only RCTs that compared the clinical efficacy and safety of MSCs with other alternative treatments or placebos in the treatment of patients with COVID-19 were included. RESULTS: Six RCTs were included, in which the MSC and control groups consisted of 158 and 135 patients, respectively. The patients who received MSCs had a significantly lower 28-day mortality rate (7.6% vs 21.5%; OR, 0.18; 95% CI, 0.06-0.52; I2 = 0%) and significantly higher clinical improvement rate (OR, 6.05; 95% CI, 2.31-15.83; I2 = 0%) than the controls. The patients who received MSCs were associated with a similar risk of adverse events (AEs) and serious AEs to the control group (AEs: OR, 33; 95% CI, 0.09-1.18; I2 = 59%; serious AEs: OR, 0.30; 95% CI, 0.02-4.41; I2 = 53%). CONCLUSIONS: MSC treatment may help to improve the clinical outcomes of patients with COVID-19. In addition, MSC treatment appears to be a safe therapeutic option for patients with COVID-19.

Nebulized exosomes derived from allogenic adipose tissue mesenchymal stromal cells in patients with severe COVID-19: a pilot study.

BACKGROUND: Existing clinical studies supported the potential efficacy of mesenchymal stromal cells as well as derived exosomes in the treatment of COVID-19. We aimed to explore the safety and efficiency of aerosol inhalation of the exosomes derived from human adipose-derived MSCs (haMSC-Exos) in patients with COVID-19. METHODS: The MEXCOVID trial is a phase 2a single-arm, open-labelled, interventional trial and patients were enrolled in Jinyintan Hospital, Wuhan, China. Eligible 7 patients were assigned to receive the daily dose of haMSCs-Exos (2.0 × 108 nano vesicles) for consecutively 5 days. The primary outcomes included the incidence of prespecified inhalation-associated events and serious adverse events. We also observed the demographic data, clinical characteristics, laboratory results including lymphocyte count, levels of D-dimer and IL-6 as well as chest imaging. RESULTS: Seven severe COVID-19 related pneumonia patients (4 males and 3 females) were enrolled and received nebulized haMSC-Exos. The median age was 57 year (interquartile range (IQR), 43 year to 70 year). The median time from onset of symptoms to hospital admission and administration of nebulized haMSC-Exos was 30 days (IQR, 15 days to 40 days) and 54 d (IQR, 34 d to 69 d), respectively. All COVID-19 patients tolerated the haMSC-Exos nebulization well, with no evidence of prespecified adverse events or clinical instability during the nebulization or during the immediate post-nebulization period. All patients presented a slight increase of serum lymphocyte counts (median as 1.61 × 109/L vs. 1.78 × 109/L). Different degrees of resolution of pulmonary lesions after aerosol inhalation of haMSC-Exos were observed among all patients, more obviously in 4 of 7 patients. CONCLUSIONS: Our trial shows that a consecutive 5 days inhalation dose of clinical grade haMSC-Exos up to a total amount of 2.0 × 109 nano vesicles was feasible and well tolerated in seven COVID-19 patients, with no evidence of prespecified adverse events, immediate clinical instability, or dose-relevant toxicity at any of the doses tested. This safety profile is seemingly followed by CT imaging improvement within 7 days. Further trials will have to confirm the long-term safety or efficacy in larger population. TRIAL REGISTRATION: MEXCOVID, NCT04276987.

How to Make Sense out of 75,000 Mesenchymal Stromal Cell Publications?

Mesenchymal stromal cells have been the subject of an expanding number of studies over the past decades. Today, over 75,000 publications are available that shine light on the biological properties and therapeutic effects of these versatile cells in numerous pre-clinical models and early-phase clinical trials. The massive number of papers makes it hard for researchers to comprehend the whole field, and furthermore, they give the impression that mesenchymal stromal cells are wonder cells that are curative for any condition. It is becoming increasingly difficult to dissect how and for what conditions mesenchymal stromal cells exhibit true and reproducible therapeutic effects. This article tries to address the question how to make sense of 75,000, and still counting, publications on mesenchymal stromal cells.

SARS-CoV-2 Exposed Mesenchymal Stromal Cell from Congenital Pulmonary Airway Malformations: Transcriptomic Analysis and the Expression of Immunomodulatory Genes.

The inflammatory response plays a central role in the complications of congenital pulmonary airway malformations (CPAM) and severe coronavirus disease 2019 (COVID-19). The aim of this study was to evaluate the transcriptional changes induced by SARS-CoV-2 exposure in pediatric MSCs derived from pediatric lung (MSCs-lung) and CPAM tissues (MSCs-CPAM) in order to elucidate potential pathways involved in SARS-CoV-2 infection in a condition of exacerbated inflammatory response. MSCs-lung and MSCs-CPAM do not express angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TRMPSS2). SARS-CoV-2 appears to be unable to replicate in MSCs-CPAM and MSCs-lung. MSCs-lung and MSCs-CPAM maintained the expression of stemness markers MSCs-lung show an inflammatory response (IL6, IL1B, CXCL8, and CXCL10), and the activation of Notch3 non-canonical pathway; this route appears silent in MSCs-CPAM, and cytokine genes expression is reduced. Decreased value of p21 in MSCs-lung suggested no cell cycle block, and cells did not undergo apoptosis. MSCs-lung appears to increase genes associated with immunomodulatory function but could contribute to inflammation, while MSCs-CPAM keeps stable or reduce the immunomodulatory receptors expression, but they also reduce their cytokines expression. These data indicated that, independently from their perilesional or cystic origin, the MSCs populations already present in a patient affected with CPAM are not permissive for SARS-CoV-2 entry, and they will not spread the disease in case of infection. Moreover, these MSCs will not undergo apoptosis when they come in contact with SARS-CoV-2; on the contrary, they maintain their staminality profile.

May mesenchymal stem cell transplantation be a solution for COVID-19 induced cytokine storm?

The recently emergent disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), transmitted by droplets and aerosols, was named coronavirus disease 2019 (COVID-19) by World Health Organization. Predominantly, the disease progress is asymptomatic or mild, but one-fifth of the patients advance to severe or critical illness. In severe COVID-19 patients, type-2 T helper cells release numerous cytokines; this excessive immune response is named as cytokine storm. The cytokine storm, which is the hallmark of the COVID-19 induced by the disease and aggravates due to lack of proper immune response, similar to SARS and Middle East respiratory syndrome (MERS), and the disease status may progress forward to acute respiratory distress syndrome (ARDS), systemic inflammatory response syndrome, multi-organ dysfunction syndrome, and death. Mesenchymal stromal cell transplantation is up-and-coming in treating many diseases such as HIV, hepatitis B, influenza, coronavirus diseases (SARS, MERS), lung injuries, and ARDS. Upon closer inspection on respiratory diseases, COVID-19, influenza, SARS, and MERS have similarities in pathogenesis, especially cytokine and immune response profiles. These comparable features in terms of the cytokine storm will provide hints for the treatment of COVID-19.

Mesenchymal stem cell-based therapy and exosomes in COVID-19: current trends and prospects.

Novel coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2. The virus causes an exaggerated immune response, resulting in a cytokine storm and acute respiratory distress syndrome, the leading cause of COVID-19-related mortality and morbidity. So far, no therapies have succeeded in circumventing the exacerbated immune response or cytokine storm associated with COVID-19. Mesenchymal stem cells (MSCs), through their immunomodulatory and regenerative activities, mostly mediated by their paracrine effect and extracellular vesicle production, have therapeutic potential in many autoimmune, inflammatory, and degenerative diseases. In this paper, we review clinical studies on the use of MSCs for COVID-19 treatment, including the salutary effects of MSCs on the pathophysiology of COVID-19 and the immunomodulation of the cytokine storm. Ongoing clinical trial designs, cell sources, dose and administration, and populations are summarized, and the paracrine mode of benefit is discussed. We also offer suggestions for optimizing MSC-based therapies, including genetic engineering, strategies for cell surface modification, nanotechnology applications, and combination therapies.

Engineering mesenchymal stromal cells with neutralizing and anti-inflammatory capability against SARS-CoV-2 infection.

The emergence of the novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to the pandemic of coronavirus disease 2019 (COVID-19), which has markedly affected global health and the economy. Both uncontrolled viral replication and a proinflammatory cytokine storm can cause severe tissue damage in patients with COVID-19. SARS-CoV-2 utilizes angiotensin-converting enzyme 2 (ACE2) as its entry receptor. In this study, we generated ACE2 extracellular domain-Fc and single-chain variable fragment-interleukin 6 (IL-6) single-chain variable fragment against IL-6 receptor (scFv-IL6R)-Fc fusion proteins to differentially neutralize viruses and ameliorate the cytokine storm. The human ACE2 (hACE2)1-740-Fc fusion protein showed a potent inhibitory effect on pseudo-typed SARS-CoV-2 entry and a good safety profile in mice. In addition, scFv-IL6R-Fc strongly blocked IL-6 signal activation. We also established a mesenchymal stromal cell (MSC)-based hACE21-740-Fc and scFv-IL6R-Fc delivery system, which could serve as a potential therapy strategy for urgent clinical needs of patients with COVID-19.

Mesenchymal stromal cell secretome in liver failure: Perspectives on COVID-19 infection treatment.

Due to their immunomodulatory potential and release of trophic factors that promote healing, mesenchymal stromal cells (MSCs) are considered important players in tissue homeostasis and regeneration. MSCs have been widely used in clinical trials to treat multiple conditions associated with inflammation and tissue damage. Recent evidence suggests that most of the MSC therapeutic effects are derived from their secretome, including the extracellular vesicles, representing a promising approach in regenerative medicine application to treat organ failure as a result of inflammation/fibrosis. The recent outbreak of respiratory syndrome coronavirus, caused by the newly identified agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has forced scientists worldwide to use all available instruments to fight the infection, including the inflammatory cascade caused by this pandemic disease. The use of MSCs is a valid approach to combat organ inflammation in different compartments. In addition to the lungs, which are considered the main inflammatory target for this virus, other organs are compromised by the infection. In particular, the liver is involved in the inflammatory response to SARS-CoV-2 infection, which causes organ failure, leading to death in coronavirus disease 2019 (COVID-19) patients. We herein summarize the current implications derived from the use of MSCs and their soluble derivatives in COVID-19 treatment, and emphasize the potential of MSC-based therapy in this clinical setting.

Effects of mesenchymal stromal cell-derived extracellular vesicles in acute respiratory distress syndrome (ARDS): Current understanding and future perspectives.

Acute respiratory distress syndrome (ARDS) is a devastating and life-threatening syndrome that results in high morbidity and mortality. Current pharmacologic treatments and mechanical ventilation have limited value in targeting the underlying pathophysiology of ARDS. Mesenchymal stromal cells (MSCs) have shown potent therapeutic advantages in experimental and clinical trials through direct cell-to-cell interaction and paracrine signaling. However, safety concerns and the indeterminate effects of MSCs have resulted in the investigation of MSC-derived extracellular vesicles (MSC-EVs) due to their low immunogenicity and tumorigenicity. Over the past decades, soluble proteins, microRNAs, and organelles packaged in EVs have been identified as efficacious molecules to orchestrate nearby immune responses, which attenuate acute lung injury by facilitating pulmonary epithelium repair, reducing acute inflammation, and restoring pulmonary vascular leakage. Even though MSC-EVs possess similar bio-functional effects to their parental cells, there remains existing barriers to employing this alternative from bench to bedside. Here, we summarize the current established research in respect of molecular mechanisms of MSC-EV effects in ARDS and highlight the future challenges of MSC-EVs for clinical application.

Efficacy of mesenchymal stromal cells and cellular products in improvement of symptoms for COVID-19 and similar lung diseases.

At the end of 2019, respiratory coronavirus diseases 2019 (COVID-19) appeared and spread rapidly in the world. Besides several mutations, the outcome of this pandemic was the death up to 15% of hospitalized patients. Mesenchymal stromal cell therapy as a therapeutic strategy seemed successful in treatment of several diseases. Not only mesenchymal stromal cells of several tissues, but also their secreted extracellular vesicles and even secretome indicated beneficial therapeutic function. All of these three options were studied for treatment of COVID-19 as well as those respiratory diseases that have similar symptom. Fortunately, most of the outcomes were promising and optimistic. In this paper, we review in-vivo and clinical studies which have been used different sources of mesenchymal stromal cell, secreted extracellular vesicles, and secretome to improve and treat symptoms of COVID-19 and similar lung diseases.

Mesenchymal stromal cells for acute respiratory distress syndrome (ARDS), sepsis, and COVID-19 infection: optimizing the therapeutic potential.

Introduction: Mesenchymal stromal (stem) cell (MSC) therapies are emerging as a promising therapeutic intervention in patients with Acute Respiratory Distress Syndrome (ARDS) and sepsis due to their reparative, immunomodulatory, and antimicrobial properties.Areas covered: This review provides an overview of Mesenchymal stromal cells (MSCs) and their mechanisms of effect in ARDS and sepsis. The preclinical and clinical evidence to support MSC therapy in ARDS and sepsis is discussed. The potential for MSC therapy in COVID-19 ARDS is discussed with insights from respiratory viral models and early clinical reports of MSC therapy in COVID-19. Strategies to optimize the therapeutic potential of MSCs in ARDS and sepsis are considered including preconditioning, altered gene expression, and alternative cell-free MSC-derived products, such as extracellular vesicles and conditioned medium.Expert opinion: MSC products present considerable therapeutic promise for ARDS and sepsis. Preclinical investigations report significant benefits and early phase clinical studies have not highlighted safety concerns. Optimization of MSC function in preclinical models of ARDS and sepsis has enhanced their beneficial effects. MSC-derived products, as cell-free alternatives, may provide further advantages in this field. These strategies present opportunity for the clinical development of MSCs and MSC-derived products with enhanced therapeutic efficacy.

Promising role for mesenchymal stromal cells in coronavirus infectious disease-19 (COVID-19)-related severe acute respiratory syndrome?

Mesenchymal stromal cells (MSC) have immune regulatory and tissue regenerative properties. MSCs are being studied as a therapy option for many inflammatory and immune disorders and are approved to treat acute graft-versus-host disease (GvHD). The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic and associated coronavirus infectious disease-19 (COVID-19) has claimed many lives. Innovative therapies are needed. Preliminary data using MSCs in the setting of acute respiratory distress syndrome (ARDS) in COVID-19 are emerging. We review mechanisms of action of MSCs in inflammatory and immune conditions and discuss a potential role in persons with COVID-19.

The Coronavirus Pandemic (SARS-CoV-2): New Problems Demand New Solutions, the Alternative of Mesenchymal (Stem) Stromal Cells.

Mesenchymal (stem) stromal cells (MSC) can be a therapeutic alternative for COVID-19 considering their anti-inflammatory, regenerative, angiogenic, and even antimicrobial capacity. Preliminary data point to therapeutic interest of MSC for patients with COVID-19, and their effect seems based on the MSC's ability to curb the cytokine storm caused by COVID-19. In fact, promising clinical studies using MSC to treat COVID-19, are currently underway. For this reason, now is the time to firmly consider new approaches to MSC research that addresses key issues, like selecting the most optimal type of MSC for each indication, assuming the heterogeneity of the donor-dependent MSC and the biological niche where MSC are located.