Non-clinical assessment of safety, biodistribution and tumorigenicity of human mesenchymal stromal cells

Next-Generation Sequencing-Based Identification of Enterobacter hormaechei as Causative Agent of High Mortality Disease in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) Mice

NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice, lacking many components of a mature immune system, are at increased risk of disease. General understanding of potential pathogens of these mice is limited. We describe a high mortality disease outbreak caused by an opportunistic bacterial infection in NSG mice. Affected animals exhibited perianal fecal staining, dehydration, and wasting. Histopathologic lesions included a primary necrotizing enterocolitis, with inflammatory and necrotizing lesions also occurring in the liver, kidneys, heart, and brain of some mice. All affected individuals tested negative for known opportunistic pathogens of immunodeficient mice. We initially identified a member of Enterobacter cloacae complex (ECC) in association with the outbreak by traditional diagnostics. ECC was cultured from extraintestinal organs, both with and without histopathologic lesions, suggesting bacteremia. Infrared spectroscopy and MALDI-TOF mass spectrometry demonstrated that isolates from the outbreak shared molecular features and likely a common origin. We subsequently hypothesized that advanced sequencing methods would identify a single species of ECC associated with clinical disease. Using a novel targeted amplicon-based next-generation sequencing assay, we identified Enterobacter hormaechei in association with this outbreak. Knowledge of this organism as a potential opportunistic pathogen in NSG mice is critical for preclinical studies to prevent loss of animals and confounding of research.

Potential role of mesenchymal stem cells in T cell aging

Immunosenescence occurs with progressive age. T cell aging is manifested by immunodeficiency and inflammation. The main mechanisms are thymic involution, mitochondrial dysfunction, genetic and epigenetic alterations, loss of protein stability, reduction of T cell receptor (TCR) repertoire, naïve-memory T cell ratio imbalance, T cell senescence, and lack of effector plasticity. Mesenchymal stem cells (MSCs) are thought to hold great potential as anti-aging therapy. However, the role of MCSs in T cell aging remains elusive. This review makes a tentative summary of the potential role of MSCs in the protection against T cell aging. It might provide a new idea to intervene in the aging of the immune system.

Novel therapies for graft versus host disease with a focus on cell therapies

Graft versus host disease (GVHD) can occur at any period post allogeneic hematopoietic stem cell transplantation as a common clinical complication contributing to significant morbidity and mortality. Acute GVHD develops in approximately 30-50% of patients receiving transplants from matched related donors. High doses of steroids are used as first-line treatment, but are unsuccessful in around 40% of patients, resulting in the diagnosis of steroid-refractory acute GVHD. Consensus has yet to develop for the management of steroid-refractory acute GVHD, and prognosis at six months has been estimated at around 50%. Thus, it is critical to find effective treatments that increase survival of steroid-refractory acute GVHD. This article describes the currently known characteristics, pathophysiology, and treatments for GVHD, with a special focus on recent advances in cell therapies. In particular, a novel cell therapy using decidua stromal cells (DSCs) was recently shown to have promising results for acute GVHD, with improved effectiveness over previous treatments including mesenchymal stromal cells. At the Karolinska Institute, severe acute GVHD patients treated with placenta-derived DSCs supplemented with either 5% albumin or 10% AB plasma displayed a one-year survival rate of 76% and 47% respectively. Furthermore, patients with steroid-refractory acute GVHD, displayed survival rates of 73% with albumin and 31% with AB plasma-supplemented DSCs, compared to the 20% survival rate in the mesenchymal stromal cell control group. Adverse events and deaths were found to be attributed only to complications of hematopoietic stem cell transplant and GVHD, not to the study intervention. ASC Therapeutics, Inc, in collaboration with the Karolinska Institute, will soon initiate a phase 2 multicenter, open-label study to further assess the efficacy and safety of intravenous DSC treatment in sixty patients with Grade II-IV steroid-refractory acute GVHD. This novel cell therapy represents a promising treatment to combat the poor prognosis that steroid-refractory acute GVHD patients currently face.

Evaluation of safety and efficacy of the bone marrow mesenchymal stem cell and gelatin-nano-hydroxyapatite combination in canine femoral defect repair

Femoral shaft fracture is a common bone trauma in dogs. The limitation of mesenchymal stem cells in bone defect applications is that the cell suspension cannot be fixed to the bone defect site. In the study, our objective was to substantiate the combined application of canine bone marrow mesenchymal stem cells (cBMSCs) and gelatin-nano-hydroxyapatite (Gel-nHAP) and evaluate its therapeutic effect on bone defect diseases in dogs. Experiments were performed to evaluate the following: (1) the porosity of Gel-nHAP; (2) the adhesion of cBMSCs to Gel-nHAP; and (3) the effect of Gel-nHAP on cBMSC proliferation. The efficacy and safety of the combination of cBMSC and Gel-nHAP in the repair of femoral shaft defects were evaluated in animal experiments. The results showed that Gel-nHAP supported the attachment of cBMSCs and exhibited good biocompatibility. In the animal bone defect repair experiment, significant cortical bone growth was observed in the Gel-nHAP group at week 8 (p < 0.05) and in the cBMSCs-Gel-nHAP group at week 4 (p < 0.01). We demonstrated that Gel-nHAP could promote the repair of bone defects, and the effect of cBMSC-Gel-nHAP on the repair of bone defects was profound.

Preclinical Evaluation of interferon-gamma primed human Wharton's jelly-derived mesenchymal stem cells

The potential of human mesenchymal stem cells (MSCs) for cell therapy has been investigated in numerous immune-mediated conditions; MSCs are considered one of the most promising cellular therapeutics to treat intractable diseases. Recently, approaches to prime MSCs have been investigated, thereby generating cellular products with enhanced potential for a variety of clinical applications. Interferon-gamma (IFN-γ) priming is a current approach used to increase the therapeutic efficacy of MSCs. In this study, we determined the systemic toxicity, tumorigenicity and biodistribution of IFN-γ-primed Wharton's jelly-derived (WJ)-MSCs in male and female BALB/c-nu/nu mice. There were no deaths or pathologic lesions in the mice treated with 5 × 10⁶ cells/kg IFN-γ-primed MSCs in the repeated dose study. In the tumorigenicity study, one of the subcutaneously treated mice showed bronchioloalveolar adenoma in the lung but tested negative for human-specific anti-mitochondrial antibody, suggesting the spontaneous murine origin of the adenoma. A biodistribution study using real-time quantitative polymerase chain reaction demonstrated the systemic IFN-γ-primed MSC clearance by day 28. Based on the toxicity, biodistribution, and tumorigenicity studies, we concluded that IFN-γ-primed MSCs at 5 × 10⁶ cells/kg do not induce tumor formation and adverse changes.

Mesenchymal stromal cell secretome for traumatic brain injury: Focus on immunomodulatory action

The severity and long-term consequences of brain damage in traumatic brain injured (TBI) patients urgently calls for better neuroprotective/neuroreparative strategies for this devastating disorder. Mesenchymal stromal cells (MSCs) hold great promise and have been shown to confer neuroprotection in experimental TBI, mainly through paracrine mechanisms via secreted bioactive factors (i.e. secretome), which indicates significant potential for a cell-free neuroprotective approach. The secretome is composed of cytokines, chemokines, growth factors, proteins, lipids, nucleic acids, metabolites, and extracellular vesicles; it may offer advantages over MSCs in terms of delivery, safety, and variability of therapeutic response for brain injury. Immunomodulation by molecular factors secreted by MSCs is considered to be a key mechanism involved in their multi-potential therapeutic effects. Regulated neuroinflammation is required for healthy remodeling of central nervous system during development and adulthood. Moreover, immune cells and their secreted factors can also contribute to tissue repair and neurological recovery following acute brain injury. However, a chronic and maladaptive neuroinflammatory response can exacerbate TBI and contribute to progressive neurodegeneration and long-term neurological impairments. Here, we review the evidence for MSC-derived secretome as a therapy for TBI. Our framework incorporates a detailed analysis of in vitro and in vivo studies investigating the effects of the secretome on clinically relevant neurological and histopathological outcomes. We also describe the activation of immune cells after TBI and the immunomodulatory properties exerted by mediators released in the secretome. We then describe how ageing modifies central and systemic immune responses to TBI and discuss challenges and opportunities of developing secretome based neuroprotective therapies for elderly TBI populations. Finally, strategies aimed at modulating the secretome in order to boost its efficacy for TBI will also be discussed.

Safety and tolerability of bone marrow-derived mesenchymal stem cells in lupus animal models and a phase I clinical trial in humans

OBJECTIVE

Several clinical trials aimed at treating various autoimmune diseases, including systemic lupus erythematosus (SLE), by introducing mesenchymal stem cells (MSCs) have been conducted. However, with refractory lupus nephritis (LN), the outcomes of MSC transplantation are not well known, and further validation is required. In particular, data concerning the safety and efficacy of LN treatment using bone marrow-derived MSCs (BM-MSCs) are still lacking.

METHODS

We identified characteristics of BM-MSCs in terms of cell morphology, chromosomal stability, differentiation capacity, and phenotype through cell passages. The in vivo stability of BM-MSCs was evaluated by single-dose and repeated-dose toxicity tests, tumorigenicity tests, and biodistribution tests using lupus mouse models. Based on the encouraging nonclinical results, we conducted a nonrandomized, open-label, single-arm phase I clinical trial to evaluate the tolerability and safety of a single administration of haploidentical allogeneic BM-MSCs (CS20AT04) in seven LN patients (NCT03174587). We used a classical three + three design to find the optimal dosage. The starting dose was 2.0×10⁶ cells/kg and escalated to 3.0×10⁶ cells/kg if there was no dose-limiting toxicity (DLT). Evaluation of the safety and tolerability was assessed 28 days after the infusion, and the maximum tolerated dose was determined.

RESULTS

Properly cultured BM-MSCs showed high proliferation and multipotency, but chromosomal changes were not found. There were two deaths by a rapid administration rate in the high-dose group (2.0×10⁶ cells/head) in a single administration test. BM-MSCs were distributed in the kidneys until Day 7. In the phase I clinical trial, seven LN patients were enrolled. Participants received BM-MSCs through intravenous infusion. There was no DLT at both initial dose (2.0×10⁶ cells/kg) and escalated dose (3.0×10⁶ cells/kg). One patient was not administered the full 2.0×10⁶ cells/kg dose because of a technical error during infusion. This patient did not show DLT. Three adverse events were reported, namely, one diarrhea, one toothache, and one arthralgia, and all were considered NCI-CTC grade I events.

CONCLUSION

We defined the characteristics of BM-MSCs and identified their safety and tolerability in both animal models and a phase I clinical trial. The maximum tolerated dose was determined to be 3.0×10⁶ cells/kg in patients with LN.