Thawed Mesenchymal Stem Cell Product Shows Comparable Immunomodulatory Potency to Cultured Cells In Vitro and in Polymicrobial Septic Animals

Transplantation of olfactory mucosa mesenchymal stromal cells repairs spinal cord injury by inducing microglial polarization

STUDY DESIGN

Animal studies OBJECTIVES: To evaluate the therapeutic effect of olfactory mucosa mesenchymal stem cell (OM-MSCs) transplantation in mice with spinal cord injury (SCI) and to explore the mechanism by which OM-MSCs inhibit neuroinflammation and improve SCI.

SETTING

Xiangya Hospital, Central South University; Affiliated Hospital of Guangdong Medical University.

METHODS

Mice (C57BL/6, female, 6-week-old) were randomly divided into sham, SCI, and SCI + OM-MSC groups. The SCI mouse model was generated using Allen's method. OM-MSCs were immediately delivered to the lateral ventricle after SCI using stereotaxic brain injections. One day prior to injury and on days 1, 5, 7, 14, 21, and 28 post-injury, the Basso Mouse Scale and Rivlin inclined plate tests were performed. Inflammation and microglial polarization were evaluated using histological staining, immunofluorescence, and qRT-PCR.

RESULTS

OM-MSCs originating from the neuroectoderm have great potential in the management of SCI owing to their immunomodulatory effects. OM-MSCs administration improved motor function, alleviated inflammation, promoted the transformation of the M1 phenotype of microglia into the M2 phenotype, facilitated axonal regeneration, and relieved spinal cord injury in SCI mice.

CONCLUSIONS

OM-MSCs reduced the level of inflammation in the spinal cord tissue, protected neurons, and repaired spinal cord injury by regulating the M1/M2 polarization of microglia.

Study of the Effect of Wild-Type and Transiently Expressing CXCR4 and IL-10 Mesenchymal Stromal Cells in a Mouse Model of Peritonitis

Sepsis due to peritonitis is a process associated with an inflammatory state. Mesenchymal stromal cells (MSCs) modulate the immune system due to the paracrine factors released and may be a therapeutic alternative. Three treatment groups were developed in a murine model of peritonitis to verify the effect of human adipose mesenchymal stem cell (hASCs). Additionally, a temporary modification was carried out on them to improve their arrival in inflamed tissues (CXCR4), as well as their anti-inflammatory activity (IL-10). The capacity to reduce systemic inflammation was studied using a local application (peritoneal injection) as a treatment route. Comparisons involving the therapeutic effect of wild-type ASCs and ASCs transiently expressing CXCR4 and IL-10 were carried out with the aim of generating an improved anti-inflammatory response for sepsis in addition to standard antibiotic treatment. However, under the experimental conditions used in these studies, no differences were found between both groups with ASCs. The peritoneal administration of hASCs or genetically modified hASCs constitutes an efficient and safe therapy in our model of mouse peritonitis.

Therapeutic effect of adipose-derived mesenchymal stem cells in a porcine model of abdominal sepsis

BACKGROUND

The term sepsis refers to a complex and heterogeneous syndrome. Although great progress has been made in improving the diagnosis and treatment of this condition, it continues to have a huge impact on morbidity and mortality worldwide. Mesenchymal stem cells are a population of multipotent cells that have immunomodulatory properties, anti-apoptotic effects, and antimicrobial activity. We studied these capacities in a porcine model of peritoneal sepsis.

METHODS

We infused human adipose-derived mesenchymal stem cells (ADSCs) into a porcine model of peritoneal sepsis. Twenty piglets were treated with antibiotics alone (control group) or antibiotics plus peritoneal infusion of ADSCs at a concentration of 2 × 106 cells/kg or 4 × 106 cells/kg (low- and high-dose experimental groups, respectively). The animals were evaluated at different time points to determine their clinical status, biochemical and hematologic parameters, presence of inflammatory cytokines and chemokines in blood and peritoneal fluid, and finally by histologic analysis of the organs of the peritoneal cavity.

RESULTS

One day after sepsis induction, all animals presented peritonitis with bacterial infection as well as elevated C-reactive protein, haptoglobin, IL-1Ra, IL-6, and IL-1b. Xenogeneic ADSC infusion did not elicit an immune response, and peritoneal administration of the treatment was safe and feasible. One day after infusion, the two experimental groups showed a superior physical condition (e.g., mobility, feeding) and a significant increase of IL-10 and TGF-β in blood and a decrease of IL-1Ra, IL-1b, and IL-6. After 7 days, all animals treated with ADSCs had better results concerning blood biomarkers, and histopathological analysis revealed a lower degree of inflammatory cell infiltration of the organs of the peritoneal cavity.

CONCLUSIONS

Intraperitoneal administration of ADSCs as an adjuvant therapy for sepsis improves the outcome and diminishes the effects of peritonitis and associated organ damage by regulating the immune system and reducing intra-abdominal adhesions in a clinically relevant porcine model of abdominal sepsis.

Efferocytosis of viable versus heat-inactivated MSC induces human monocytes to distinct immunosuppressive phenotypes

BACKGROUND

Immunomodulation by mesenchymal stromal cells (MSCs) can occur through trophic factor mechanisms, however, intravenously infused MSCs are rapidly cleared from the body yet a potent immunotherapeutic response is still observed. Recent work suggests that monocytes contribute to the clearance of MSCs via efferocytosis, the body's natural mechanism for clearing dead and dying cells in a non-inflammatory manner. This begs the questions of how variations in MSC quality affect monocyte phenotype and if viable MSCs are even needed to elicit an immunosuppressive response.

METHODS

Herein, we sought to dissect MSC's trophic mechanism from their efferocytic mechanisms and determine if the viability of MSCs prior to efferocytosis influences the resultant phenotype of monocytes. We cultured viable or heat-inactivated human umbilical cord MSCs with human peripheral blood mononuclear cells for 24 h and observed changes in monocyte surface marker expression and secretion profile. To isolate the effect of efferocytosis from MSC trophic factors, we used cell separation techniques to remove non-efferocytosed MSCs before challenging monocytes to suppress T-cells or respond to inflammatory stimuli. For all experiments, viable and heat-inactivated efferocytic-licensing of monocytes were compared to non-efferocytic-licensing control.

RESULTS

We found that monocytes efferocytose viable and heat-inactivated MSCs equally, but only viable MSC-licensed monocytes suppress activated T-cells and suppression occurred even after depletion of residual MSCs. This provides direct evidence that monocytes that efferocytose viable MSCs are immunosuppressive. Further characterization of monocytes after efferocytosis showed that uptake of viable-but not heat inactivated-MSC resulted in monocytes secreting IL-10 and producing kynurenine. When monocytes were challenged with LPS, IL-2, and IFN-γ to simulate sepsis, monocytes that had efferocytosed viable MSC had higher levels of IDO while monocytes that efferocytosed heat inactivated-MSCs produced the lowest levels of TNF-α.

CONCLUSION

Collectively, these studies show that the quality of MSCs efferocytosed by monocytes polarize monocytes toward distinctive immunosuppressive phenotypes and highlights the need to tailor MSC therapies for specific indications.

Mesenchymal stem cells induce dynamic immunomodulation of airway and systemic immune cells in vivo but do not improve survival for mice with H1N1 virus-induced acute lung injury

Introduction: Influenza A virus (IAV)-induced acute lung injury (ALI) is characterized by pronounced proinflammatory activation and respiratory lung dysfunction. In this study, we performed deep immune profiling on airway and circulating immune cells to examine the effect of immunomodulation and therapeutic outcomes of mesenchymal stem cells (MSCs) therapy in mice with IAV-induced ALI. Methods: Animals were inoculated intranasally with H1N1 IAV, followed by intravenous administration of vehicle, or human clinical-grade, bone marrow-derived MSCs 24-h later, and monitored for six days to evaluate the survival. In another set of animals, bronchoalveolar lavage (BAL) fluid and whole blood were collected three days after infection for flow or mass cytometry (CyTOF) immune profiling analysis. Results: Immune cell population and phenotypic shifts in blood were mapped by CyTOF. Increases were observed in granulocytes and myeloid-derived cells in blood from vehicle-treated animals. While MSC treatment accentuated changes in these populations, naïve B, antibody-secreting B cells, and T cells were decreased in MSC-treated animals at day 3. Compared to sham animals, IAV infection induced a significant 5.5-fold increase in BAL total cell counts, including CD4⁺ and CD8⁺ T cells, CD19⁺ B cells, CD11b + Ly6G + neutrophils, and CD11b + Ly6C + monocytes. MSC treatment significantly decreased BAL total cell counts in IAV-infected mice, specifically the number of infiltrating CD4⁺ T cells and CD11b + Ly6G + neutrophils. In contrast, there were increases in CD8⁺ T cells, B cells, and monocytes in the alveolar space in MSC-treated animals. Phenotypic immune cell profiling of blood and BAL revealed a significantly higher proportion of the monocyte population with the M2 phenotype (CD206) in MSC-treated animals; however, this failed to confer protective effects in the survival of infected mice or reduce viral titer in the lung. Further investigation revealed that MSCs were susceptible to IAV infection, leading to increased cell death and potentially affecting their efficacy. Conclusion: These findings provided in vivo evidence that MSCs promote the selective recruitment of immune cells to the site of infection during IAV infection, with reductions in proinflammatory phenotypes. However, MSCs offered no survival benefit in IAV-infected animals, possibly due to MSCs' H1N1 IAV susceptibility and subsequent cell death.

Comparative Analysis of the Therapeutic Effects of Fresh and Cryopreserved Human Umbilical Cord Derived Mesenchymal Stem Cells in the Treatment of Psoriasis

Psoriasis, an inflammatory autoimmune skin disease, is characterized by scaly white or erythematous plaques, which severely influence patients' quality of life and social activities. Mesenchymal stem cells derived from the human umbilical cord (UCMSCs) represent a promising therapeutic approach for psoriasis because of its unique superiority in ethical agreeableness, abundant source, high proliferation capacity, and immunosuppression. Although cryopreservation provided multiple benefits to the cell therapy, it also greatly compromised clinical benefits of MSCs due to impaired cell functions. The current study aims to evaluate the therapeutic efficacy of cryopreserved UCMSCs in a mouse model of psoriasis as well as in patients with psoriasis. Our results showed that cryopreserved and fresh UCMSCs have comparable effects on the suppression of psoriasis-like symptoms such as thickening, erythema, and scaling, and serum IL-17 A secretion in mice model of psoriasis. Moreover, psoriatic patients injected with cryopreserved UCMSCs had a significant improvement in the Psoriasis Area and Severity Index (PASI), Physician Global Assessment (PGA), and Patient Global Assessments (PtGAs) scores compared to baseline values. Mechanically, cryopreserved UCMSCs markedly inhibit the proliferation of PHA-activated PBMCs, type 1 T helper (Th1) and type 17 T helper (Th17) cell differentiation and secretion of inflammatory cytokines including IFN-γ, TNF-a and IL-17 A in PBMCs stimulated by anti-CD3/CD28 beads. Taken together, these data indicated that cryopreserved UCMSCs exhibited great beneficial effect on psoriasis. Thus, cryopreserved UCMSCs can be systemically administered as ''off-the-shelf'' cell product for psoriasis therapy. Trial Registration ChiCTR1800019509. Registered on November 15, 2018-Retrospectively registered, http://www.chictr.org.cn/ .

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.

Prophylactic Administration of Mesenchymal Stromal Cells Does Not Prevent Arrested Lung Development in Extremely Premature-Born Non-Human Primates

Premature birth is a leading cause of childhood morbidity and mortality and often followed by an arrest of postnatal lung development called bronchopulmonary dysplasia. Therapies using exogenous mesenchymal stromal cells (MSC) have proven highly efficacious in term-born rodent models of this disease, but effects of MSC in actual premature-born lungs are largely unknown. Here, we investigated thirteen non-human primates (baboons; Papio spp.) that were born at the limit of viability and given a single, intravenous dose of ten million human umbilical cord tissue-derived MSC per kilogram or placebo immediately after birth. Following two weeks of human-equivalent neonatal intensive care including mechanical ventilation, lung function testing and echocardiographic studies, lung tissues were analyzed using unbiased stereology. We noted that therapy with MSC was feasible, safe and without signs of engraftment when administered as controlled infusion over 15 minutes, but linked to adverse events when given faster. Administration of cells was associated with improved cardiovascular stability, but neither benefited lung structure, nor lung function after two weeks of extrauterine life. We concluded that a single, intravenous administration of MSC had no short- to mid-term lung-protective effects in extremely premature-born baboons, sharply contrasting data from term-born rodent models of arrested postnatal lung development and urging for investigations on the mechanisms of cell-based therapies for diseases of prematurity in actual premature organisms.

M. Rocco P, Cuenca J. Safety and efficacy of clinical-grade, cryopreserved menstrual blood mesenchymal stromal cells in experimental acute respiratory distress syndrome

Background: Treatment for critical care conditions, such as acute respiratory distress syndrome (ARDS), requires ready-to-administer injectable mesenchymal stromal cells (MSCs). A validated cryopreserved therapy based on MSCs derived from menstrual blood (MenSCs) is an attractive option that offers advantages over freshly cultured cells and allows its use as an off-the-shelf therapy in acute clinical conditions. The main goal of this study is to provide evidence on the impact of cryopreservation on different biological functions of MenSCs and to determine the optimal therapeutic dose, safety, and efficacy profile of clinical-grade, cryopreserved (cryo)-MenSCs in experimental ARDS. Methods: Biological functions of fresh versus cryo-MenSCs were compared in vitro. The effects of cryo-MenSCs therapy were evaluated in vivo in ARDS-induced (Escherichia coli lipopolysaccharide) C57BL/6 mice. After 24 h, the animals were treated with five doses ranging from 0.25×10⁵ to 1.25×10⁶ cells/animal. At 2 and 7 days after induction of ARDS, safety and efficacy were evaluated. Results: Clinical-grade cryo-MenSCs injections improved lung mechanics and reduced alveolar collapse, tissue cellularity, and remodelling, decreasing elastic and collagen fiber content in alveolar septa. In addition, administration of these cells modulated inflammatory mediators and promoted pro-angiogenic and anti-apoptotic effects in lung-injured animals. More beneficial effects were observed with an optimal dose of 4×10⁶ cells/Kg than with higher or lower doses. Conclusion: From a translational perspective, the results showed that clinical-grade cryopreserved MenSCs retain their biological properties and exert a therapeutic effect in mild to moderate experimental ARDS. The optimal therapeutic dose was well-tolerated, safe, and effective, favouring improved lung function. These findings support the potential value of an off-the-shelf MenSCs-based product as a promising therapeutic strategy for treating ARDS.

Comparison of adhesion of thawed and cultured synovial mesenchymal stem cells to the porcine meniscus and the relevance of cell surface microspikes

BACKGROUND

Placement of a cultured synovial mesenchymal stem cell (MSC) suspension on a repaired meniscus for 10 min accelerated meniscus repair. Upon placement of the MSC suspension on the meniscus, microspikes projecting from the MSC surface trap meniscus fibers and promote MSC adhesion. Thawed cryopreserved MSCs are preferred materials for meniscus repair, as they can be transplanted without additional culture. However, the adhesion ability of thawed cryopreserved MSCs is unknown. Here, we compared the proportion of cultured versus thawed MSCs adhering to a porcine meniscus immediately and 10 min after placement. We also investigated the relationship between adhesion and the number of microspikes on the synovial MSCs.

METHODS

Synovial MSCs were prepared from the knees of four donors with osteoarthritis. The "cultured MSCs" were thawed MSCs that were re-cultured and suspended in PBS for transplantation. A similarly prepared suspension was cryopreserved, thawed again, suspended in PBS, and used without further culture as the "thawed MSCs." MSCs with at least three microspikes in SEM images were defined as microspike-positive MSCs. Porcine meniscus surfaces were abraded, cut into a cylindrical shape, and treated with MSC suspension. Non-adherent cells were counted immediately and again 10 min after placement to calculate the adhesion proportion.

RESULTS

The proportion of microspike-positive MSCs was significantly higher in thawed (53 ± 3%) than in cultured (28 ± 5%) MSC suspensions. MSC adhesion to the meniscus was significantly better for the thawed than for the cultured MSC suspensions immediately after placement on the meniscus, but no differences were detected after 10 min. The proportion of MSCs with microspikes in the cell suspension was significantly correlated with the proportion of adhered MSCs immediately after the placement, but not 10 min later. Addition of FBS to the cryopreservation medium promoted a concentration-dependent increase in the proportion of microspike-positive cells.

CONCLUSIONS

Thawed MSCs adhered better than cultured MSCs immediately after placement, but adhesion was similar for both MSC preparations after 10 min. Immediately after placement, the presence of microspikes was associated with better adhesion of synovial MSCs to the meniscus.

Proceedings of the ISCT scientific signature series symposium, "Advances in cell and gene therapies for lung diseases and critical illnesses": International Society for Cell & Gene Therapy, Burlington VT, US, July 16, 2021

The ISCT Scientific Signature Series Symposium "Advances in Cell and Gene Therapies for Lung Diseases and Critical Illnesses" was held as an independent symposium in conjunction with the biennial meeting, "Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases," which took place July 12-15, 2021, at the University of Vermont. This is the third Respiratory System-based Signature Series event; the first 2, "Tracheal Bioengineering, the Next Steps" and "Cellular Therapies for Pulmonary Diseases and Critical Illnesses: State of the Art of European Science," took place in 2014 and 2015, respectively. Cell- and gene-based therapies for respiratory diseases and critical illnesses continue to be a source of great promise and opportunity. This reflects ongoing advancements in understanding of the mechanisms by which cell-based therapies, particularly those using mesenchymal stromal cells (MSCs), can mitigate different lung injuries and the increasing sophistication with which preclinical data is translated into clinical investigations. This also reflects continuing evolution in gene transfer vectors, including those designed for in situ gene editing in parallel with those targeting gene or cell replacement. Therefore, this symposium convened global thought leaders in a forum designed to catalyze communication and collaboration to bring the greatest possible innovation and value of cell- and gene-based therapies for patients with respiratory diseases and critical illnesses.

Comparison of freshly cultured versus cryopreserved mesenchymal stem cells in animal models of inflammation: A pre-clinical systematic review

Background:

Mesenchymal stem cells (MSCs) are multipotent cells that demonstrate therapeutic potential for the treatment of acute and chronic inflammatory-mediated conditions. Although controversial, some studies suggest that MSCs may lose their functionality with cryopreservation which could render them non-efficacious. Hence, we conducted a systematic review of comparative pre-clinical models of inflammation to determine if there are differences in in vivo measures of pre-clinical efficacy (primary outcomes) and in vitro potency (secondary outcomes) between freshly cultured and cryopreserved MSCs.

Methods:

A systematic search on OvidMEDLINE, EMBASE, BIOSIS, and Web of Science (until January 13, 2022) was conducted. The primary outcome included measures of in vivo pre-clinical efficacy; secondary outcomes included measures of in vitro MSC potency. Risk of bias was assessed by the SYRCLE ‘Risk of Bias’ assessment tool for pre-clinical studies.

Results:

Eighteen studies were included. A total of 257 in vivo pre-clinical efficacy experiments represented 101 distinct outcome measures. Of these outcomes, 2.3% (6/257) were significantly different at the 0.05 level or less; 2 favoured freshly cultured and 4 favoured cryopreserved MSCs. A total of 68 in vitro experiments represented 32 different potency measures; 13% (9/68) of the experiments were significantly different at the 0.05 level or less, with seven experiments favouring freshly cultured MSC and two favouring cryopreserved MSCs.

Conclusions:

The majority of preclinical primary in vivo efficacy and secondary in vitro potency outcomes were not significantly different (p<0.05) between freshly cultured and cryopreserved MSCs. Our systematic summary of the current evidence base may provide MSC basic and clinical research scientists additional rationale for considering a cryopreserved MSC product in their pre-clinical studies and clinical trials as well as help identify research gaps and guide future related research.

Funding:

Ontario Institute for Regenerative Medicine

Poly(I:C) Enhances Mesenchymal Stem Cell Control of Myeloid Cells From COVID-19 Patients

Mesenchymal stem cells (MSCs) are being studied for the treatment of COVID-19-associated critical illness, due to their immunomodulatory properties. Here, we hypothesized that viral mimic-priming improves MSCs’ abilities to rebalance the dysregulated immune responses in COVID-19. Transcriptome analysis of poly(I:C)-primed MSCs (pIC-MSCs) showed upregulation of pathways in antiviral and immunomodulatory responses. Together with increased expression of antiviral proteins such as MX1, IFITM3, and OAS1, these changes translated to greater effector functions in regulating monocytes and granulocytes while further enhancing MSCs’ ability to block SARS-CoV-2 pseudovirus entry into epithelial cells. Most importantly, the addition of pIC-MSCs to COVID-19 patient whole blood significantly reduced inflammatory neutrophils and increased M2 monocytes while enhancing their phagocytic effector function. We reveal for the first time that MSCs can be primed by Toll-like receptor 3 agonist to improve their ability to rebalance the dysregulated immune responses seen in severe SARS-CoV-2 infection.

•

Viral stimuli mimic enhances MSC’s antiviral and immunomodulatory molecular profile

•

pIC-primed MSCs inhibit SARS-CoV2 pseudovirus entry into epithelial cells

•

pIC-MSCs recalibrate dysregulated cellular response in COVID patient’s whole blood

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.

Application of engineered extracellular vesicles for targeted tumor therapy

All cells, including prokaryotes and eukaryotes, could release extracellular vesicles (EVs). EVs contain many cellular components, including RNA, and surface proteins, and are essential for maintaining normal intercellular communication and homeostasis of the internal environment. EVs released from different tissues and cells exhibit excellent properties and functions (e.g., targeting specificity, regulatory ability, physical durability, and immunogenicity), rendering them a potential new option for drug delivery and precision therapy. EVs have been demonstrated to transport antitumor drugs for tumor therapy; additionally, EVs' contents and surface substance can be altered to improve their therapeutic efficacy in the clinic by boosting targeting potential and drug delivery effectiveness. EVs can regulate immune system function by affecting the tumor microenvironment, thereby inhibiting tumor progression. Co-delivery systems for EVs can be utilized to further improve the drug delivery efficiency of EVs, including hydrogels and liposomes. In this review, we discuss the isolation technologies of EVs, as well as engineering approaches to their modification. Moreover, we evaluate the therapeutic potential of EVs in tumors, including engineered extracellular vesicles and EVs' co-delivery systems.

Technologies such as microfluidics can improve EVs isolation efficiency.

Engineering technologies can improve EVs drug loading efficiency and tumor targeting.

EVs-based drug co-delivery systems are being developed, such as those with liposomes and hydrogels.

OUP accepted manuscript

Bronchopulmonary dysplasia (BPD) is a life-threatening condition in preterm infants with few effective therapies. Mesenchymal stem or stromal cells (MSCs) are a promising therapeutic strategy for BPD. The ideal MSC source for BPD prevention is however unknown. The objective of this study was to compare the regenerative effects of MSC obtained from bone marrow (BM) and umbilical cord tissue (UCT) in an experimental BPD model. In vitro, UCT-MSC demonstrated greater proliferation and expression of anti-inflammatory cytokines as compared to BM-MSC. Lung epithelial cells incubated with UCT-MSC conditioned media (CM) had better-wound healing following scratch injury. UCT-MSC CM and BM-MSC CM had similar pro-angiogenic effects on hyperoxia-exposed pulmonary microvascular endothelial cells. In vivo, newborn rats exposed to normoxia or hyperoxia (85% O₂) from postnatal day (P) 1 to 21 were given intra-tracheal (IT) BM or UCT-MSC (1 × 10⁶ cells/50 μL), or placebo (PL) on P3. Hyperoxia PL-treated rats had marked alveolar simplification, reduced lung vascular density, pulmonary vascular remodeling, and lung inflammation. In contrast, administration of both BM-MSC and UCT-MSC significantly improved alveolar structure, lung angiogenesis, pulmonary vascular remodeling, and lung inflammation. UCT-MSC hyperoxia-exposed rats however had greater improvement in some morphometric measures of alveolarization and less lung macrophage infiltration as compared to the BM-MSC-treated group. Together, these findings suggest that BM-MSC and UCT-MSC have significant lung regenerative effects in experimental BPD but UCT-MSC suppresses lung macrophage infiltration and promotes lung epithelial cell healing to a greater degree.

Comparative Bioactivity Analysis for Off-the-Shelf and Culture-Rescued Umbilical Cord-Derived Mesenchymal Stem/Stromal Cells in a Xeno- and Serum-Free Culture System

We recently reported a standardized xeno- and serum-free culture platform to isolate and expand umbilical cord-derived mesenchymal stem/stromal cells (UC-MSCs). Comparing populations from the same passage, cells that were cryopreserved and culture-rescued exhibited characteristics similar to those of their fresh counterparts, continuously cultured cells without interim cryopreservation. The culture rescue after thawing allowed for the cells to be fully recovered. However, since it would be more cost-effective and timesaving if cryopreserved cells can be used as an off-the-shelf product, we set out to compare the bioactivity of freshly thawed UC-MSCs versus culture-rescued UC-MSCs of the same batch that were recultured for an additional passage under our xeno- and serum-free protocol. UC-MSCs showed high viability in both the freshly thawed and the re-cultured group. Both populations displayed a similar proliferation capacity which is indicated by a comparable population doubling time and colony-forming ability. Both freshly thawed and culture-rescued UC-MSCs expressed the characteristic immunophenotype and were capable of differentiating into osteocytes, chondrocytes, and adipocytes. On the other hand, culture-rescued cells appeared to be more potent in immunosuppression than freshly thawed cells. In conclusion, freshly thawed and culture-rescued cell products share comparable bioactivity in cell growth and proliferation, immunophenotype, and differentiation potential. However, the culture-rescued cells that were allowed to grow for an additional passage appear to display a more favorable immunomodulatory potential when compared to their freshly thawed parent cells.

Mesenchymal stromal cell therapeutic potency is dependent upon viability, route of delivery, and immune match

Culture-adapted bone marrow mesenchymal stromal cells (MSCs) deploy paracrine anti-inflammatory and tissue regenerative functionalities that can be harnessed as a living cell pharmaceutical product. Independent of clinical indication, a near majority of human clinical trials administer MSC IV, often with an allogeneic MSC cell product immediately after thawing from cryostorage. Despite hundreds of studies in a wide assortment of inflammatory, degenerative, and acute tissue injury syndromes, human clinical outcomes often fail to mirror promising rigorously conducted preclinical animal studies. Using a mouse model of toxic colitis, we demonstrate that replication fit MSCs harvested in log phase of growth have substantial impact on colitis clinical and pathologic endpoints when delivered subcutaneously or intraperitoneally, whereas the maximum tolerated IV bolus dosing failed to do so. We also demonstrate that heat-inactivated MSCs lose all therapeutic utility and the observation is mirrored by use of viable MSC administered immediately postthaw from cryostorage. Using luciferase transgenic MSC as donor cells, we demonstrate that transient in vivo engraftment is severely compromised when MSCs are dead or thawed and further demonstrate that MSC redosing is feasible in relapsing colitis, but only syngeneic MSCs lead to sustained improvement of clinical endpoints. These data support the notion that pharmaceutical potency of MSC requires viability and functional fitness. Reciprocally, IV administration of thawed MSC products may be biased against positive clinical outcomes for treatment of colitis and that extravascular administration of syngeneic, fit MSCs allows for effect in a recurrent therapy model.

Thawed cryopreserved synovial mesenchymal stem cells show comparable effects to cultured cells in the inhibition of osteoarthritis progression in rats

Intra-articular injections of mesenchymal stem cells (MSCs) can inhibit the progression of osteoarthritis (OA). Previous reports have used cultured MSCs, but the ability to use thawed cryopreserved MSC stocks would be highly advantageous. Our purpose was to elucidate whether thawed cryopreserved MSCs show comparable inhibitory effects on OA progression in rats to those obtained with cultured MSCs. Cultured rat synovial MSCs or thawed MSCs were compared for in vitro viability and properties. The inhibitory effect of thawed MSCs on OA progression was evaluated by injecting cryopreservation fluid and thawed MSCs in meniscectomized rats. Cartilage degeneration was assessed using gross finding and histological scores. Cultured MSCs were then injected into one knee and thawed MSCs into the contralateral knee of the same individual to compare their effects. Cultured MSCs and MSCs thawed after cryopreservation had comparable in vitro colony formation and chondrogenic potentials. In the rat OA model, the gross finding and histological scores were significantly lower in the thawed MSC group than in the cryopreservation fluid group at 8 weeks. Finally, cartilage degeneration did not differ significantly after injection of cultured and thawed MSCs. In conclusion, thawed MSCs showed comparable inhibitory effects on OA progression to cultured MSCs.

Influence of Hypothermic Storage Fluids on Mesenchymal Stem Cell Stability: A Comprehensive Review and Personal Experience

Mesenchymal stem cells have generated a great deal of interest due to their potential use in regenerative medicine and tissue engineering. Examples illustrating their therapeutic value across various in vivo models are demonstrated in the literature. However, some clinical trials have not proved their therapeutic efficacy, showing that translation into clinical practice is considerably more difficult and discrepancies in clinical protocols can be a source of failure. Among the critical factors which play an important role in MSCs’ therapeutic efficiency are the method of preservation of the stem cell viability and various characteristics during their storage and transportation from the GMP production facility to the patient’s bedside. The cell storage medium should be considered a key factor stabilizing the environment and greatly influencing cell viability and potency and therefore the effectiveness of advanced therapy medicinal product (ATMP) based on MSCs. In this review, we summarize data from 826 publications concerning the effect of the most frequently used cell preservation solutions on MSC potential as cell-based therapeutic medicinal products.

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.

Mesenchymal stem/stromal cell-based therapy: mechanism, systemic safety and biodistribution for precision clinical applications

Mesenchymal stem/stromal cells (MSCs) are a promising resource for cell-based therapy because of their high immunomodulation ability, tropism towards inflamed and injured tissues, and their easy access and isolation. Currently, there are more than 1200 registered MSC clinical trials globally. However, a lack of standardized methods to characterize cell safety, efficacy, and biodistribution dramatically hinders the progress of MSC utility in clinical practice. In this review, we summarize the current state of MSC-based cell therapy, focusing on the systemic safety and biodistribution of MSCs. MSC-associated risks of tumor initiation and promotion and the underlying mechanisms of these risks are discussed. In addition, MSC biodistribution methodology and the pharmacokinetics and pharmacodynamics of cell therapies are addressed. Better understanding of the systemic safety and biodistribution of MSCs will facilitate future clinical applications of precision medicine using stem cells.

Gene engineered mesenchymal stem cells: greater transgene expression and efficacy with minicircle vs. plasmid DNA vectors in a mouse model of acute lung injury

BACKGROUND

Acute lung injury (ALI) and in its severe form, acute respiratory distress syndrome (ARDS), results in increased pulmonary vascular inflammation and permeability and is a major cause of mortality in many critically ill patients. Although cell-based therapies have shown promise in experimental ALI, strategies are needed to enhance the potency of mesenchymal stem cells (MSCs) to develop more effective treatments. Genetic modification of MSCs has been demonstrated to significantly improve the therapeutic benefits of these cells; however, the optimal vector for gene transfer is not clear. Given the acute nature of ARDS, transient transfection is desirable to avoid off-target effects of long-term transgene expression, as well as the potential adverse consequences of genomic integration.

METHODS

Here, we explored whether a minicircle DNA (MC) vector containing human angiopoietin 1 (MC-ANGPT1) can provide a more effective platform for gene-enhanced MSC therapy of ALI/ARDS.

RESULTS

At 24 h after transfection, nuclear-targeted electroporation using an MC-ANGPT1 vector resulted in a 3.7-fold greater increase in human ANGPT1 protein in MSC conditioned media compared to the use of a plasmid ANGPT1 (pANGPT1) vector (2048 ± 567 pg/mL vs. 552.1 ± 33.5 pg/mL). In the lipopolysaccharide (LPS)-induced ALI model, administration of pANGPT1 transfected MSCs significantly reduced bronchoalveolar lavage (BAL) neutrophil counts by 57%, while MC-ANGPT1 transfected MSCs reduced it by 71% (p < 0.001) by Holm-Sidak's multiple comparison test. Moreover, compared to pANGPT1, the MC-ANGPT1 transfected MSCs significantly reduced pulmonary inflammation, as observed in decreased levels of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2). pANGPT1-transfected MSCs significantly reduced BAL albumin levels by 71%, while MC-ANGPT1-transfected MSCs reduced it by 85%.

CONCLUSIONS

Overall, using a minicircle vector, we demonstrated an efficient and sustained expression of the ANGPT1 transgene in MSCs and enhanced the therapeutic effect on the ALI model compared to plasmid. These results support the potential benefits of MC-ANGPT1 gene enhancement of MSC therapy to treat ARDS.

MSC Based Therapies to Prevent or Treat BPD-A Narrative Review on Advances and Ongoing Challenges

Bronchopulmonary dysplasia (BPD) remains one of the most devastating consequences of preterm birth resulting in life-long restrictions in lung function. Distorted lung development is caused by its inflammatory response which is mainly provoked by mechanical ventilation, oxygen toxicity and bacterial infections. Dysfunction of resident lung mesenchymal stem cells (MSC) represents one key hallmark that drives BPD pathology. Despite all progress in the understanding of pathomechanisms, therapeutics to prevent or treat BPD are to date restricted to a few drugs. The limited therapeutic efficacy of established drugs can be explained by the fact that they fail to concurrently tackle the broad spectrum of disease driving mechanisms and by the huge overlap between distorted signal pathways of lung development and inflammation. The great enthusiasm about MSC based therapies as novel therapeutic for BPD arises from the capacity to inhibit inflammation while simultaneously promoting lung development and repair. Preclinical studies, mainly performed in rodents, raise hopes that there will be finally a broadly acting, efficient therapy at hand to prevent or treat BPD. Our narrative review gives a comprehensive overview on preclinical achievements, results from first early phase clinical studies and challenges to a successful translation into the clinical setting.

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.

Mesenchymal Stromal Cells' Therapy for Polyglutamine Disorders: Where Do We Stand and Where Should We Go?

Polyglutamine (polyQ) diseases are a group of inherited neurodegenerative disorders caused by the expansion of the cytosine-adenine-guanine (CAG) repeat. This mutation encodes extended glutamine (Q) tract in the disease protein, resulting in the alteration of its conformation/physiological role and in the formation of toxic fragments/aggregates of the protein. This group of heterogeneous disorders shares common molecular mechanisms, which opens the possibility to develop a pan therapeutic approach. Vast efforts have been made to develop strategies to alleviate disease symptoms. Nonetheless, there is still no therapy that can cure or effectively delay disease progression of any of these disorders. Mesenchymal stromal cells (MSC) are promising tools for the treatment of polyQ disorders, promoting protection, tissue regeneration, and/or modulation of the immune system in animal models. Accordingly, data collected from clinical trials have so far demonstrated that transplantation of MSC is safe and delays the progression of some polyQ disorders for some time. However, to achieve sustained phenotypic amelioration in clinics, several treatments may be necessary. Therefore, efforts to develop new strategies to improve MSC's therapeutic outcomes have been emerging. In this review article, we discuss the current treatments and strategies used to reduce polyQ symptoms and major pre-clinical and clinical achievements obtained with MSC transplantation as well as remaining flaws that need to be overcome. The requirement to cross the blood-brain-barrier (BBB), together with a short rate of cell engraftment in the lesioned area and low survival of MSC in a pathophysiological context upon transplantation may contribute to the transient therapeutic effects. We also review methods like pre-conditioning or genetic engineering of MSC that can be used to increase MSC survival in vivo, cellular-free approaches-i.e., MSC-conditioned medium (CM) or MSC-derived extracellular vesicles (EVs) as a way of possibly replacing the use of MSC and methods required to standardize the potential of MSC/MSC-derived products. These are fundamental questions that need to be addressed to obtain maximum MSC performance in polyQ diseases and therefore increase clinical benefits.