Mesenchymal stromal cell variables influencing clinical potency: the impact of viability, fitness, route of administration and host predisposition.

The International Society for Cell & Gene Therapy mesenchymal stromal cell (MSC) committee has been an interested observer of community interests in all matters related to MSC identity, mechanism of action, potency assessment and etymology, and it has regularly contributed to this conversation through a series of MSC pre-conferences and committee publications dealing with these matters. Arising from these reflections, the authors propose that an overlooked and potentially disruptive perspective is the impact of in vivo persistence on potency that is not predicted by surrogate cellular potency assays performed in vitro and how this translates to in vivo outcomes. Systemic delivery or extravascular implantation at sites removed from the affected organ system seems to be adequate in affecting clinical outcomes in many pre-clinical murine models of acute tissue injury and inflammatory pathology, including the recent European Medicines Agency-approved use of MSCs in Crohn-related fistular disease. The authors further propose that MSC viability and metabolic fitness likely dominate as a potency quality attribute, especially in recipients poised for salutary benefits as defined by emerging predictive biomarkers of response.

Cell-based therapies for coronavirus disease 2019: proper clinical investigations are essential.

The serious consequences of the global coronavirus disease 2019 (COVID-19) pandemic have prompted a rapid global response to develop effective therapies that can lessen disease severity in infected patients. Cell-based approaches, primarily using mesenchymal stromal cells (MSCs), have demonstrated a strong safety profile and possible efficacy in patients with acute respiratory distress syndrome (ARDS), but whether these therapies are effective for treating respiratory virus-induced ARDS is unknown. According to the World Health Organization International Clinical Trials Registry Platform and the National Institutes of Health ClinicalTrials.gov databases, 27 clinical investigations of MSC-based cell therapy approaches have begun in China since the onset of the COVID-19 outbreak, with a growing number of academic and industry trials elsewhere as well. Several recent published reports have suggested potential efficacy; however, the available data presented are either anecdotal or from incomplete, poorly controlled investigations. Therefore, although there may be a potential role for MSCs and other cell-based therapies in treatment of COVID-19, these need to be investigated in a rationally designed, controlled approach if safety and efficacy are to be demonstrated accurately. The authors urge that the field proceed by finding a balance between swift experimentation and communication of results and scientifically coherent generation and analysis of clinical data.

Progression in patients with low- and intermediate-1-risk del(5q) myelodysplastic syndromes is predicted by a limited subset of mutations.

A high proportion of patients with lower-risk del(5q) myelodysplastic syndromes will respond to treatment with lenalidomide. The median duration of transfusion-independence is 2 years with some long-lasting responses, but almost 40% of patients progress to acute leukemia by 5 years after starting treatment. The mechanisms underlying disease progression other than the well-established finding of small TP53-mutated subclones at diagnosis remain unclear. We studied a longitudinal cohort of 35 low- and intermediate-1-risk del(5q) patients treated with lenalidomide (n=22) or not (n=13) by flow cytometric surveillance of hematopoietic stem and progenitor cell subsets, targeted sequencing of mutational patterns, and changes in the bone marrow microenvironment. All 13 patients with disease progression were identified by a limited number of mutations in TP53, RUNX1, and TET2, respectively, with PTPN11 and SF3B1 occurring in one patient each. TP53 mutations were found in seven of nine patients who developed acute leukemia, and were documented to be present in the earliest sample (n=1) and acquired during lenalidomide treatment (n=6). By contrast, analysis of the microenvironment, and of hematopoietic stem and progenitor cells by flow cytometry was of limited prognostic value. Based on our data, we advocate conducting a prospective study aimed at investigating, in a larger number of cases of del(5q) myelodysplastic syndromes, whether the detection of such mutations before and after lenalidomide treatment can guide clinical decision-making.

International Society for Cellular Therapy perspective on immune functional assays for mesenchymal stromal cells as potency release criterion for advanced phase clinical trials.

Mesenchymal stromal cells (MSCs) as a pharmaceutical for ailments characterized by pathogenic autoimmune, alloimmune and inflammatory processes now cover the spectrum of early- to late-phase clinical trials in both industry and academic sponsored studies. There is a broad consensus that despite different tissue sourcing and varied culture expansion protocols, human MSC-like cell products likely share fundamental mechanisms of action mediating their anti-inflammatory and tissue repair functionalities. Identification of functional markers of potency and reduction to practice of standardized, easily deployable methods of measurements of such would benefit the field. This would satisfy both mechanistic research as well as development of release potency assays to meet Regulatory Authority requirements for conduct of advanced clinical studies and their eventual registration. In response to this unmet need, the International Society for Cellular Therapy (ISCT) addressed the issue at an international workshop in May 2015 as part of the 21st ISCT annual meeting in Las Vegas. The scope of the workshop was focused on discussing potency assays germane to immunomodulation by MSC-like products in clinical indications targeting immune disorders. We here provide consensus perspective arising from this forum. We propose that focused analysis of selected MSC markers robustly deployed by in vitro licensing and metricized with a matrix of assays should be responsive to requirements from Regulatory Authorities. Workshop participants identified three preferred analytic methods that could inform a matrix assay approach: quantitative RNA analysis of selected gene products; flow cytometry analysis of functionally relevant surface markers and protein-based assay of secretome. We also advocate that potency assays acceptable to the Regulatory Authorities be rendered publicly accessible in an "open-access" manner, such as through publication or database collection.

Intranasal delivery of central nervous system-retargeted human mesenchymal stromal cells prolongs treatment efficacy of experimental autoimmune encephalomyelitis.

Treatment with mesenchymal stromal cells (MSCs) is currently of interest for a number of diseases including multiple sclerosis. MSCs are known to target inflamed tissues, but in a therapeutic setting their systemic administration will lead to few cells reaching the brain. We hypothesized that MSCs may target the brain upon intranasal administration and persist in central nervous system (CNS) tissue if expressing a CNS-targeting receptor. To demonstrate proof of concept, MSCs were genetically engineered to express a myelin oligodendrocyte glycoprotein-specific receptor. Engineered MSCs retained their immunosuppressive capacity, infiltrated into the brain upon intranasal cell administration, and were able to significantly reduce disease symptoms of experimental autoimmune encephalomyelitis (EAE). Mice treated with CNS-targeting MSCs were resistant to further EAE induction whereas non-targeted MSCs did not give such persistent effects. Histological analysis revealed increased brain restoration in engineered MSC-treated mice. In conclusion, MSCs can be genetically engineered to target the brain and prolong therapeutic efficacy in an EAE model.

Treatment with mesenchymal stromal cells is a risk factor for pneumonia-related death after allogeneic hematopoietic stem cell transplantation.

We performed a retrospective cohort study to find out whether the use of reduced-intensity conditioning (RIC) might reduce the risk of early death from pneumonia. Pneumonia-associated deaths were evaluated in 691 hematopoietic stem cell transplantation (HSCT) patients. The majority had a hematological malignancy (n = 504) and an HLA-matched donor (n = 584). RIC was given to 336 patients and myeloablative conditioning (MAC) to 355. Data concerning radiology, culture and autopsy results were evaluated together with risk factors for death related to pneumonia within or after 100 d after HSCT (early and overall pneumonia). In 60 patients, pneumonia contributed to death (early n = 17). The cumulative incidence of early pneumonia-related death was 2.8% and 2.1% in MAC and RIC patients, respectively. The cumulative incidence of overall pneumonia-related death was 8.2% and 10.5%, respectively. In 40 patients, (67%) an etiology could be established, with 19 patients having proven or probable mold infection. In the multivariate analyses, acute graft-versus-host disease (GVHD) grades II-IV, cytomegalovirus (CMV) infection and having received mesenchymal stromal cells (MSCs) were factors associated with overall pneumonia-related death. Bacteremia and a previous HSCT were associated with early pneumonia-related death. RIC did not reduce the incidence of early death associated with pneumonia. Acute GVHD II-IV, CMV infection and MSC treatment were factors associated with pneumonia-related death. Mold infection was the most common contributor to pneumonia-related death in HSCT patients.

Donor cell-derived acute myeloid leukemia after second allogenic cord blood transplantation in a patient with Fanconi anemia.

DCL following hematopoietic stem cell transplantation has been reported in approximately 5% of all leukemic relapses. There have been several reports on DCL, mainly AML after umbilical cord blood transplantation. In this case study, we present a young boy diagnosed with Fanconi anemia who underwent an umbilical cord blood transplantation. Because of the graft failure, he was retransplanted one month later, also with a cord blood transplant. Two years after the second transplant, he developed AML, where 100% of the cells were of female donor origin. The donor, a now 14-yr-old female, was recently reported healthy.

The Coronavirus Pandemic: A Pitfall or a Fast Track for Validating Cell Therapy Products?

The global COVID-19 pandemic has prompted urgent need for potential therapies for severe respiratory consequences resulting from coronavirus infection. New therapeutic agents that will attenuate ongoing inflammation and at the same time promote regeneration of injured lung epithelial cells are urgently needed. Cell-based therapies, primarily involving mesenchymal stromal cells (MSCs) and their derivatives, are currently investigated worldwide for SARS-CoV-2-induced lung diseases. A significant number of academic centers and companies globally have already initiated such trials. However, at a time of unprecedented need, it is also foreseen that families and caregivers will seek all available options, including access to cell-based and other investigational products, even before proven safety and efficacy as well as regulatory approval. This should not be an excuse for opportunists to sell or advertise unproven therapies of any kind. "Compassionate use" should be conducted in the context of a clinical investigation framed by strict ethical and regulatory permissions, with the goal of obtaining mechanistic information wherever possible.

Treatment of vocal fold scarring with autologous bone marrow-derived human mesenchymal stromal cells-first phase I/II human clinical study: commentary to response.

We would like to thank for the interest for the article and comments in the response. We believe that cell therapy may offer a treatment for severe voice problems in patients with vocal fold scarring and MSC treatment is a valuable alternative.

Treatment of vocal fold scarring with autologous bone marrow-derived human mesenchymal stromal cells-first phase I/II human clinical study.

BACKGROUND: Vocal fold (VF) scarring, caused by surgery or inflammation, often results in severe voice problems or aphonia. Effective lasting treatment is lacking. Previous in vitro and in vivo animal studies reported positive effects on VF scar resolution with mesenchymal stromal cell (MSC) implantation. The principal aim of this study was to examine safety aspects and secondly treatment efficacy vocal fold function in patients with VF scarring and severe voice problems. METHODS: In this open-label phase I/II study, 16 patients were treated with surgical scar resection followed by injection of autologous MSCs (0.5-2 × 106 MSCs/patient). Patients were monitored 1 year for serious adverse events (SAE) or minor complications. Therapeutic efficacy on treated VFs was evaluated by measurement of VF vibrations using high-speed laryngoscopy (HSL) and phonation pressure threshold (PTP) for elasticity and VF function. Patients self-reported voice change using the Voice Handicap Index (VHI). RESULTS: No SAE or minor side effects were reported. Video ratings of VF vibrations and digitized analysis of HSL and PTP were significantly improved for 62-75% of the patients (depending on parameter). Two patients showed deteriorated VF vibrations, but improved PTP. VHI was significantly improved in 8 patients, with the remaining experiencing no significant change. CONCLUSIONS: The results indicate that local injection of autologous MSC into scarred VFs with severe voice problems may offer a safe and feasible therapeutic option. VF vibration and elasticity were improved in approximately two thirds of treated patients. This clinical study is registered in clinicaltrials.gov (ID: NCT01981330). Retrospective registration of first patient (20130511). https//: register.clinicaltrials.gov/.

Different outcome of allogeneic transplantation in myelofibrosis using conventional or reduced-intensity conditioning regimens.

Allogeneic haematopoietic stem cell transplantation remains the only curative treatment of myelofibrosis with myeloid metaplasia (MMM). Previous reports have indicated significant treatment-related mortality (TRM) for patients transplanted after myeloablative conditioning but superior survival has been reported after reduced-intensity conditioning (RIC). We report the results of a survey of all allogeneic transplantations for MMM performed in Sweden at six transplant units between 1982 and 2004. Twenty-seven patients were transplanted; 17 with a myeloablative conditioning regimen and 10 with RIC. The median age was 50 years (5-63 years) at transplantation. After a median follow up of 55 months, 20 patients are alive. TRM was 10% in the RIC group and 30% in the myeloablative group. There was no difference in survival for high or low-risk patients according to Cervantes score or between sibling and unrelated donor transplantations.

Human mesenchymal stem cells do not differentiate into cardiomyocytes in a cardiac ischemic xenomodel.

AIM: As the capability of human mesenchymal stem cells (hMSC) to engraft, differentiate and improve myocardial function cannot be studied in humans, exploration was performed in a xenomodel. METHODS: The rats were divided into three groups depending on the type of rats used (Rowett nude (RNU) or Fischer rats +/- immunosuppression). Different groups were treated with intramyocardial injection of hMSC (1-2 million) either directly or three days after ligation of the left anterior descending artery (LAD). Myocardial function was investigated by echocardiography. The hMSC were identified with fluorescence in situ hybridization and myocardial differentiation was assessed by immunohistochemistry. RESULTS: When hMSC were injected directly after LAD ligation they could be identified in half (8/16) of the RNU rats (without immunosuppression) at 4 weeks. When injected 3 days after LAD ligation in immunosuppressed RNU rats they were identified in all (6/6) rats at 6 weeks. The surviving hMSC showed signs of differentiation into fibroblasts. No cardiomyocyte differentiation was observed. There was no difference in myocardial function in treated animals compared to controls. CONCLUSIONS: The hMSC survived in this xenomodel up to 6 weeks. However, hMSC required implantation into immunoincompetent animals as well as immunosuppression to survive, indicating that these cells are otherwise rejected. Furthermore, these cells did not differentiate into cardiomyocytes nor did they improve heart function in this xenomodel.

Graft-versus-host disease is associated with a lower relapse incidence after hematopoietic stem cell transplantation in patients with acute lymphoblastic leukemia.

To determine the graft-versus-leukemia effect after hematopoietic stem cell transplantation (HSCT), we studied 199 patients with acute lymphoblastic leukemia who underwent transplantation at Huddinge University Hospital between 1981 and 2001. Seventy-four patients were in first complete remission (CR1), and 125 were in later stages of the disease. Most patients had an HLA-identical sibling donor. Conditioning consisted mainly of total body irradiation and cyclophosphamide, and graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and methotrexate. Acute GVHD developed in 143 patients and chronic GVHD in 67. The 5-year probability of relapse and relapse-free survival (RFS) were 32% and 49%, respectively, in patients in CR1, as compared with 53% and 33% in those with more advanced disease. In the multivariate risk factor analysis of relapse, we found that the absence of chronic GVHD (P<.001), absence of herpes simplex virus infection after HSCT (P=.003), combination prophylaxis with methotrexate and cyclosporine (P=.01), and >6 weeks from the diagnosis to CR (P=.025) were independent risk factors for relapse after HSCT. Factors associated with a better relapse-free survival were chronic GVHD (P<.001), ABO blood group mismatch (P=.006), younger patient age (P=.01), and an HLA-matched donor (P=.01). The association between herpes simplex virus infection and a low frequency of relapse is a new observation and may indicate that viral antigens play a role in the induction of an antileukemic effect.

Allogenic stem cell transplantation for nonmalignant disorders using matched unrelated donors.

We here report 25 patients with nonmalignant disorders, ie, severe aplastic anemia (SAA, n = 12) or inborn errors of metabolism (IEM, n = 13), who underwent allogeneic hematopoietic stem cell transplantation (HSCT) from unrelated high-resolution typed HLA-A, -B, and -DRbeta1 identical donors. One patient had an HLA-B subtype-mismatched donor. Conditioning for SAA mainly consisted of cyclophosphamide and total body irradiation, and that for IEM consisted of busulfan and cyclophosphamide. All patients received antithymocyte globulin during conditioning. After HSCT, they were given cyclosporine combined with methotrexate for immunosuppression. Two patients rejected their grafts: 1 died of pneumonia, and the other was successfully regrafted. The cumulative incidence of acute graft-versus-host disease grades II to IV was 24%, whereas chronic graft-versus-host disease occurred in 21%. The 5-year survival rates were 83% in the SAA group and 85% in those with IEM. We conclude that HSCT with HLA-A, -B, and -DRbeta1 genomically matched unrelated donors in combination with antithymocyte globulin in the conditioning regimen gives encouraging results in patients with SAA or IEM.