Mesenchymal Stem Cells and Tuberculosis: Clinical Challenges and Opportunities

Human mesenchymal stromal cells inhibit Mycobacterium avium replication in clinically relevant models of lung infection

INTRODUCTION

Novel therapeutic strategies are urgently needed for Mycobacterium avium complex pulmonary disease (MAC-PD). Human mesenchymal stromal cells (MSCs) can directly inhibit MAC growth, but their effect on intracellular bacilli is unknown. We investigated the ability of human MSCs to reduce bacterial replication and inflammation in MAC-infected macrophages and in a murine model of MAC-PD.

METHODS

Human monocyte-derived macrophages (MDMs) were infected with M. avium Chester strain and treated with human bone marrow-derived MSCs. Intracellular and extracellular colony-forming units (CFUs) were counted at 72 hours. Six-week-old female balb/c mice were infected by nebulisation of M. avium Chester. Mice were treated with 1×106 intravenous human MSCs or saline control at 21 and 28 days post-infection. Lungs, liver and spleen were harvested 42 days post-infection for bacterial counts. Cytokines were quantified by ELISA.

RESULTS

MSCs reduced intracellular bacteria in MDMs over 72 hours (median 35% reduction, p=0.027). MSC treatment increased extracellular concentrations of prostaglandin E2 (PGE2) (median 10.1-fold rise, p=0.002) and reduced tumour necrosis factor-α (median 28% reduction, p=0.025). Blocking MSC PGE2 production by cyclo-oxygenase-2 (COX-2) inhibition with celecoxib abrogated the antimicrobial effect, while this was restored by adding exogenous PGE2. MSC-treated mice had lower pulmonary CFUs (median 18% reduction, p=0.012), but no significant change in spleen or liver CFUs compared with controls.

CONCLUSION

MSCs can modulate inflammation and reduce intracellular M. avium growth in human macrophages via COX-2/PGE2 signalling and inhibit pulmonary bacterial replication in a murine model of chronic MAC-PD.

Mesenchymal stromal cell-based therapy in lung diseases; from research to clinic

Recent studies demonstrated that mesenchymal stem cells (MSCs) are important for the cell-based therapy of diseased or injured lung due to their immunomodulatory and regenerative properties as well as limited side effects in experimental animal models. Preclinical studies have shown that MSCs have also a remarkable effect on the immune cells, which play major roles in the pathogenesis of multiple lung diseases, by modulating their activity, proliferation, and functions. In addition, MSCs can inhibit both the infiltrated immune cells and detrimental immune responses in the lung and can be used in treating lung diseases caused by a virus infection such as Tuberculosis and SARS-COV-2. Moreover, MSCs are a source for alveolar epithelial cells such as type 2 (AT2) cells. These MSC-derived functional AT2-like cells can be used to treat and diminish serious lung disorders, including acute lung injury, asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis in animal models. As an alternative MSC-based therapy, extracellular vesicles that are derived from MSC-derived can be employed in regenerative medicine. Herein, we discussed the key research findings from recent clinical and preclinical studies on the functions of MSCs in treating some common and well-studied lung diseases. We also discussed the mechanisms underlying MSC-based therapy of well-studied lung diseases, and the recent employment of MSCs in both the attenuation of lung injury/inflammation and promotion of the regeneration of lung alveolar cells after injury. Finally, we described the role of MSC-based therapy in treating major pulmonary diseases such as pneumonia, COPD, asthma, and idiopathic pulmonary fibrosis (IPF).

Mesenchymal stem cells-derived extracellular vesicles for therapeutics of renal tuberculosis

Extrapulmonary tuberculosis with a renal involvement can be a manifestation of a disseminated infection that requires therapeutic intervention, particularly with a decrease in efficacy of conventional regimens. In the present study, we investigated the therapeutic potency of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) in the complex anti-tuberculosis treatment (ATT). A rabbit model of renal tuberculosis (rTB) was constructed by injecting of the standard strain Mycobacterium tuberculosis H37Rv into the cortical layer of the kidney parenchyma. Isolated rabbit MSC-EVs were intravenously administered once as an addition to standard ATT (isoniazid, pyrazinamide, and ethambutol). The therapeutic efficacy was assessed by analyzing changes of blood biochemical biomarkers and levels of anti- and pro-inflammatory cytokines as well as by renal computed tomography with subsequent histological and morphometric examination. The therapeutic effect of therapy with MSC-EVs was shown by ELISA method that confirmed a statistically significant increase of the anti-inflammatory and decrease of pro-inflammatory cytokines as compared to conventional treatment. In addition, there is a positive trend in increase of ALP level, animal weigh, and normalization of ADA activity that can indicate an improvement of kidney state. A significant reduction of the area of specific and interstitial inflammation indicated positive affect of MSC-EVs that suggests a shorter duration of ATT. The number of MSC-EVs proteins (as identified by mass-spectometry analysis) with anti-microbial, anti-inflammatory and immunoregulatory functions reduced the level of the inflammatory response and the severity of kidney damage (further proved by morphometric analysis). In conclusion, MSC-EVs can be a promising tool for the complex treatment of various infectious diseases, in particularly rTB.

Comparison of Autografts and Biodegradable 3D-Printed Composite Scaffolds with Osteoconductive Properties for Tissue Regeneration in Bone Tuberculosis

Tuberculosis remains one of the major health problems worldwide. Besides the lungs, tuberculosis affects other organs, including bones and joints. In the case of bone tuberculosis, current treatment protocols include necrectomy in combination with conventional anti-tuberculosis therapy, followed by reconstruction of the resulting bone defects. In this study, we compared autografting and implantation with a biodegradable composite scaffold for bone-defect regeneration in a tuberculosis rabbit model. Porous three-dimensional composite materials were prepared by 3D printing and consisted of poly(ε-caprolactone) filled with nanocrystalline cellulose modified with poly(glutamic acid). In addition, rabbit mesenchymal stem cells were adhered to the surface of the composite scaffolds. The developed tuberculosis model was verified by immunological subcutaneous test, real-time polymerase chain reaction, biochemical markers and histomorphological study. Infected animals were randomly divided into three groups, representing the infection control and two experimental groups subjected to necrectomy, anti-tuberculosis treatment, and plastic surgery using autografts or 3D-composite scaffolds. The lifetime observation of the experimental animals and analysis of various biochemical markers at different time periods allowed the comparison of the state of the animals between the groups. Micro-computed tomography and histomorphological analysis enabled the evaluation of osteogenesis, inflammation and cellular changes between the groups, respectively.

Histoplasma capsulatum modulates the immune response, affects proliferation and differentiation, and induces apoptosis of mesenchymal stromal cells

Mesenchymal stromal cells (MSC) have been widely used not only for tissue regeneration but also for the treatment of various diseases; however, it has been shown that infection of MSCs by different pathogens can attenuate their intrinsic immunomodulatory properties, affecting the proliferation and differentiation of these cells. Currently, the mechanisms by which MSCs respond to pathogen invasion are poorly understood. Therefore, the objective of the present study was to determine if the infection of bone marrow-derived MSCs, with yeasts of the pathogenic fungus Histoplasma capsulatum affects the activation, differentiation and/or proliferation of the MSCs. The results indicate that MSCs have the ability to phagocytose H. capsulatum yeasts but do not exert a notable antifungal effect. On the contrary, the infection of the MSCs with this fungal pathogen not only modulates the expression of inflammatory mediators by a mechanism dependent on TLR2, TLR4 and Dectin-1 but also affects the viability and differentiation capacity of the MSCs. These findings suggest that infection of MSCs by H. capsulatum could not only affect haematopoiesis but also modulate the immune response in the infected host and, furthermore, these MSCs could provide a niche for the fungus, allowing it to persist and evade the immune response of the host.

Antibiotic Resistance to Mycobacterium tuberculosis and Potential Use of Natural and Biological Products as Alternative Anti-Mycobacterial Agents

Background: Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (Mtb). TB treatment is based on the administration of three major antibiotics: isoniazid, rifampicin, and pyrazinamide. However, multi-drug resistant (MDR) Mtb strains are increasing around the world, thus, allowing TB to spread around the world. The stringent response is demonstrated by Mtb strains in order to survive under hostile circumstances, even including exposure to antibiotics. The stringent response is mediated by alarmones, which regulate bacterial replication, transcription and translation. Moreover, the Mtb cell wall contributes to the mechanism of antibiotic resistance along with efflux pump activation and biofilm formation. Immunity over the course of TB is managed by M1-macrophages and M2-macrophages, which regulate the immune response against Mtb infection, with the former exerting inflammatory reactions and the latter promoting an anti-inflammatory profile. T helper 1 cells via secretion of interferon (IFN)-gamma, play a protective role in the course of TB, while T regulatory cells secreting interleukin 10, are anti-inflammatory. Alternative therapeutic options against TB require further discussion. In view of the increasing number of MDR Mtb strains, attempts to replace antibiotics with natural and biological products have been object of intensive investigation. Therefore, in this review the anti-Mtb effects exerted by probiotics, polyphenols, antimicrobial peptides and IFN-gamma will be discussed. All the above cited compounds are endowed either with direct antibacterial activity or with anti-inflammatory and immunomodulating characteristics.

Alternatives to Antibiotics against Mycobacterium abscessus

Mycobacterium abscessus complex is extremely difficult to treat. Intrinsic and acquired bacterial resistance makes this species one of the most challenging pathogens and treatments last from months to years, associated with potential risky antibiotic toxicity and a high number of failures. Nonantibiotic antimicrobial agents against this microorganism have recently been studied so as to offer an alternative to current drugs. This review summarizes recent research on different strategies such as host modulation using stem cells, photodynamic therapy, antibiofilm therapy, phage therapy, nanoparticles, vaccines and antimicrobial peptides against M. abscessus both in vitro and in vivo.

Mesenchymal stem/stromal cells in the pathogenesis and regenerative therapy of inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) represent a group of chronic inflammatory disorders of the gastrointestinal (GI) tract including ulcerative colitis (UC), Crohn’s disease (CD), and unclassified IBDs. The pathogenesis of IBDs is related to genetic susceptibility, environmental factors, and dysbiosis that can lead to the dysfunction of immune responses and dysregulated homeostasis of local mucosal tissues characterized by severe inflammatory responses and tissue damage in GI tract. To date, extensive studies have indicated that IBDs cannot be completely cured and easy to relapse, thus prompting researchers to find novel and more effective therapeutics for this disease. Due to their potent multipotent differentiation and immunomodulatory capabilities, mesenchymal stem/stromal cells (MSCs) not only play an important role in regulating immune and tissue homeostasis but also display potent therapeutic effects on various inflammatory diseases, including IBDs, in both preclinical and clinical studies. In this review, we present a comprehensive overview on the pathological mechanisms, the currently available therapeutics, particularly, the potential application of MSCs-based regenerative therapy for IBDs.

Mesenchymal Stem Cell-Derived Exosome Therapy of Microbial Diseases: From Bench to Bed

Microbial diseases are a global health threat, leading to tremendous casualties and economic losses. The strategy to treat microbial diseases falls into two broad categories: pathogen-directed therapy (PDT) and host-directed therapy (HDT). As the typical PDT, antibiotics or antiviral drugs directly attack bacteria or viruses through discerning specific molecules. However, drug abuse could result in antimicrobial resistance and increase infectious disease morbidity. Recently, the exosome therapy, as a HDT, has attracted extensive attentions for its potential in limiting infectious complications and targeted drug delivery. Mesenchymal stem cell-derived exosomes (MSC-Exos) are the most broadly investigated. In this review, we mainly focus on the development and recent advances of the application of MSC-Exos on microbial diseases. The review starts with the difficulties and current strategies in antimicrobial treatments, followed by a comprehensive overview of exosomes in aspect of isolation, identification, contents, and applications. Then, the underlying mechanisms of the MSC-Exo therapy in microbial diseases are discussed in depth, mainly including immunomodulation, repression of excessive inflammation, and promotion of tissue regeneration. In addition, we highlight the latest progress in the clinical translation of the MSC-Exo therapy, by summarizing related clinical trials, routes of administration, and exosome modifications. This review will provide fundamental insights and future perspectives on MSC-Exo therapy in microbial diseases from bench to bedside.