Mesenchymal stem/stromal cell-based therapies for severe viral pneumonia: therapeutic potential and challenges

Adipose-Derived Mesenchymal Stem Cells Attenuate Immune Reactions Against Pig Decellularized Bronchi Engrafted into Rat Tracheal Defects

Decellularized scaffolds are promising biomaterials for tissue and organ reconstruction; however, strategies to effectively suppress the host immune responses toward these implants, particularly those without chemical crosslinking, remain warranted. Administration of mesenchymal stem cells is effective against immune-mediated inflammatory disorders. Herein, we investigated the effect of isogeneic abdominal adipose-derived mesenchymal stem/stromal cells (ADMSCs) on xenogeneic biomaterial-induced immunoreactions. Peripheral bronchi from pigs, decellularized using a detergent enzymatic method, were engrafted onto tracheal defects of Brown Norway (BN) rats. BN rats were implanted with native pig bronchi (Xenograft group), decellularized pig bronchi (Decellularized Xenograft), or Decellularized Xenograft and ADMSCs (Decellularized Xenograft+ADMSC group). In the latter group, ADMSCs were injected intravenously immediately post implantation. Harvested graft implants were assessed histologically and immunohistochemically. We found that acute rejections were milder in the Decellularized Xenograft and Decellularized Xenograft+ADMSC groups than in the Xenograft group. Mild inflammatory cell infiltration and reduced collagen deposition were observed in the Decellularized Xenograft+ADMSC group. Additionally, ADMSC administration decreased CD8+ lymphocyte counts but increased CD163+ cell counts. In the Decellularized Xenograft+ADMSC group, serum levels of vascular endothelial growth factor and IL-10 were elevated and tissue deposition of IgM and IgG was low. The significant immunosuppressive effects of ADMSCs illustrate their potential use as immunosuppressive agents for xenogeneic biomaterial-based implants.

A Systematic Review of Gene Expression Studies in Critically Ill Patients with Sepsis and Community-Acquired Pneumonia

(1) Background: Sepsis is present in nearly 90% of critically ill patients with community-acquired pneumonia (CAP). This systematic review updates the information on studies that have assessed gene expression profiles in critically ill septic patients with CAP. (2) Methods: We searched for studies that satisfied the following criteria: (a) expression profile in critically ill patients with sepsis due to CAP, (b) presence of a control group, and (c) adult patients. Over-representation analysis was performed with clusterProfiler using the Hallmark and Reactome collections. (3) Results: A total of 4312 differentially expressed genes (DEGs) and sRNAs were included in the enrichment analysis. In the Hallmark collection, genes regulated by nuclear factor kappa B in response to tumor necrosis factor, genes upregulated by signal transducer and activator of transcription 5 in response to interleukin 2 stimulation, genes upregulated in response to interferon-gamma, genes defining the inflammatory response, a subgroup of genes regulated by MYC-version 1 (v1), and genes upregulated during transplant rejection were significantly enriched in critically ill septic patients with CAP. Moreover, 88 pathways were identified in the Reactome database. (4) Conclusions: This study summarizes the reported DEGs in critically ill septic patients with CAP and investigates their functional implications. The results highlight the complexity of immune responses during CAP.

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.

Key Role of Mesenchymal Stromal Cell Interaction with Macrophages in Promoting Repair of Lung Injury

Lung macrophages (Mφs) are essential for pulmonary innate immunity and host defense due to their dynamic polarization and phenotype shifts. Mesenchymal stromal cells (MSCs) have secretory, immunomodulatory, and tissue-reparative properties and have shown promise in acute and chronic inflammatory lung diseases and in COVID-19. Many beneficial effects of MSCs are mediated through their interaction with resident alveolar and pulmonary interstitial Mφs. Bidirectional MSC-Mφ communication is achieved through direct contact, soluble factor secretion/activation, and organelle transfer. The lung microenvironment facilitates MSC secretion of factors that result in Mφ polarization towards an immunosuppressive M2-like phenotype for the restoration of tissue homeostasis. M2-like Mφ in turn can affect the MSC immune regulatory function in MSC engraftment and tissue reparatory effects. This review article highlights the mechanisms of crosstalk between MSCs and Mφs and the potential role of their interaction in lung repair in inflammatory lung diseases.

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.

RGD-Hydrogel Improves the Therapeutic Effect of Bone Marrow-Derived Mesenchymal Stem Cells on Phosgene-Induced Acute Lung Injury in Rats

Mesenchymal stem cells (MSCs) have promising potential in the treatment of various diseases, such as the therapeutic effect of bone marrow-derived MSCs for phosgene-induced acute lung injury (P-ALI). However, MSC-related therapeutics are limited due to poor cell survival, requiring appropriate MSC delivery systems to maximise therapeutic capacity. Biomaterial RGD-hydrogel is a potential cell delivery vehicle as it can mimic the natural extracellular matrix and provide cell adhesion support. The application of RGD-hydrogel in the MSC treatment of respiratory diseases is scarce. This study reports that RGD-hydrogel has good biocompatibility and can increase the secretion of Angiopoietin-1, hepatocyte growth factor, epidermal growth factor, vascular endothelial cell growth factor, and interleukin-10 in vitro MSCs. The hydrogel-encapsulated MSCs could further alleviate P-ALI and show better cell survival in vivo. Overall, RGD-hydrogel could improve the MSC treatment of P-ALI by modulating cell survival and reparative activities. It is exciting to see more and more ways to unlock the therapeutic potential of MSCs.