Revisiting the role of mesenchymal stem cells in tuberculosis and other infectious diseases

Mucosal-associated invariant T-cells in pulmonary pathophysiology

PURPOSE OF REVIEW

Mucosal-associated invariant T-cells (MAIT) have been associated with lung cancer and pulmonary infections. The treatment of patients with cancer or infections includes host-directed therapies (HDTs). MAIT play a role in shaping the 'milieu interne' in cancer and infections and this review addresses the biology of MAIT in pulmonary pathophysiology.

RECENT FINDINGS

MAIT represent an attractive target for therapy in pulmonary malignancies and infections. T-cells are often difficult to exploit therapeutically due to the diversity of both T-cell receptor (TCR) repertoire and its ligandome. MAIT-cells are restricted by the major histocompatibility complex class I-related gene protein (MR1) that presents nondefined tumor-associated targets, bacterial products, vitamin and drug derivates. Due to their plasticity in gene expression, MAIT are able to conversely switch from IFN-γ to IL-17 production. Both cytokines play a key role in protective immune responses in infections and malignancies. MAIT-derived production of interleukin (IL)-17/TGF-β shapes the tumor micro-environment (TME), including tissue re-modelling leading to pulmonary fibrosis and recruitment of neutrophils. MAIT contribute to the gut-lung axis associated with clinical improved responses of patients with cancer to checkpoint inhibition therapy. MAIT are at the crossroad of HDTs targeting malignant and infected cells. Clinical presentations of overt inflammation, protective immune responses and tissue re-modeling are reviewed along the balance between Th1, Th2, Th9, and Th17 responses associated with immune-suppression or protective immune responses in infections.

SUMMARY

MAIT shape the TME in pulmonary malignancies and infections. Drugs targeting the TME and HDTs affect MAIT that can be explored to achieve improved clinical results while curbing overt tissue-damaging immune responses.

Huc-MSCs-derived exosomes alleviate non-alcoholic steatohepatitis by regulating macrophages polarization through miR-24-3p/STING axis

BACKGROUND

There's a scarcity of drugs effective against nonalcoholic steatohepatitis (NASH). Exosomes from Human umbilical cord mesenchymal stem cells (huc-MSCs) show potential in managing glycolipid metabolism and the immune response. Therefore, further investigations are required to explore their application in NASH and the underlying mechanisms.

METHODS

C57BL/6J mice were fed with a western diet for 12 weeks to induce NASH, and huc-MSCs exosomes (MSCs-exo) were administered during the feeding period. The effect of MSCs-exo was evaluated by monitoring changes in body weight, fat distribution, blood glucose, and insulin levels, and analyzing pathological alterations in liver tissue. Mechanism investigations were carried out using flow cytometry, immunofluorescence staining, and other experimental techniques.

RESULTS

MSCs-exo could reduce liver fat, inflammation, fibrosis, and improved metabolism to alleviate the progression of NASH. Besides, MSCs-exo could decrease macrophage accumulation in the liver, encouraging M2 over M1 macrophage polarization. Furthermore, our study found that MSCs-exo had a high expression of miR-24-3p, which may regulate macrophage polarization by targeting the interferon-stimulated genes (STING) gene in macrophages, with its overexpression amplifying MSCs-exo's NASH benefits.

CONCLUSIONS

These findings suggest that the therapeutic effect of MSCs-exo on NASH may be attributed to the regulation of macrophage M2 polarization through miR-24-3p targeting STING. This provides a scientific basis for future clinical application.

Circular RNA ZNF277 Sponges miR-378d to Inhibit the Intracellular Survival of Mycobacterium tuberculosis by Upregulating Rab10

Circular RNAs (circRNAs) are covalently closed non-coding RNAs formed by back-splicing, lacking a 5' cap and poly-A tail. They could act as important regulatory factors in the host's anti-tuberculosis immune process, but only a few have been identified, and their molecular mechanisms remain largely unclear. Here, we identified a novel circRNA, circ-ZNF277, which responds to Mycobacterium tuberculosis (Mtb) infection in THP-1 cells. Circ-ZNF277 binds microRNA-378d (miR-378d) in vivo. The expression level of circ-ZNF277 affects the clearance of the intracellular Mtb in THP-1 cells. Mechanistically, more circ-ZNF277 molecules could absorb more miR-378d, thereby competitively activating the NF-κB signaling pathway, promoting the release of pro-inflammatory cytokines including interleukins IL-1β and IL-6, and tumor necrosis factor-α (TNF-α), and inhibiting the survival of intracellular Mtb. Expressing miR-378d or si-Rab10 targeting the transcription of Rab10 could antagonize the effects of overexpression of circ-ZNF277, resulting in the reduced intracellular survival of Mtb. In summary, circ-ZNF277 inhibits the intracellular survival of Mtb via the miR-378d/Rab10 axis. This finding represents a novel mechanism of circular RNA in regulating host immune responses during Mtb infection.

Whole Blood vs Serum-Derived Exosomes for Host and Pathogen-Specific Tuberculosis Biomarker Identification: RNA-Seq-Based Machine-Learning Approach

Mycobacterium tuberculosis (Mtb) remains a leading infectious disease responsible for millions of deaths. RNA sequencing is a rapidly growing technique and a powerful approach to understanding host and pathogen cross-talks via transcriptional responses. However, its application is limited due to the high costs involved.This study is a preliminary attempt to understand host-pathogen cross-talk during TB infection in different TB clinical cohorts using two biological fluids: Whole blood and serum exosomes (EXO). We conducted an RNA-sequencing machine-learning approach using 20 active TB (ATB), 11 latent TB (LTB), three healthy control (HC) whole blood datasets, and two ATB, LTB, and HC serum EXO datasets. During the study, host-derived differentially expressed genes (DEGs) were identified in both whole blood and EXOs, while EXOs were successful in identifying pathogen-derived DEGs only in LTB. The majority of the DEGs in whole blood were up-regulated between ATB and HC, and ATB and LTB, while down-regulated between LTB and HC, which was vice versa for the EXOs, indicating different mechanisms in response to different states of TB infection across the two different biological samples. The pathway analysis revealed that whole blood gene signatures were mainly involved in host immune responses, whereas exosomal gene signatures were involved in manipulating the host's cellular responses and supporting Mtb survival. Overall, identifying both host and pathogen-derived gene signatures in different biological samples for intracellular pathogens like Mtb is vital to decipher the complex interplay between the host and the pathogen, ultimately leading to more successful future interventions.

Beyond antibiotics: mesenchymal stem cells and bacteriophages-new approaches to combat bacterial resistance in wound infections

Wound management is a major global health problem. With the rising incidence of diabetic wounds, accidents, and other injuries, the demand for prompt wound treatment has become increasingly critical. Millions of people suffer from serious, large wounds resulting from major accidents, surgeries, and wars. These wounds require considerable time to heal and are susceptible to infection. Furthermore, chronic wounds, particularly in elderly and diabetic patients, often require frequent medical interventions to prevent complications. Consequently, wound management imposes a significant economic burden worldwide. The complications arising from wound infections can vary from localized issues to systemic effects. The most severe local complication of wound infection is the non-healing, which results from the disruption of the wound-healing process. This often leads to significant pain, discomfort, and psychological trauma for the patient. Systemic complications may include cellulitis, osteomyelitis, and septicemia. Mesenchymal stem cells are characterized by their high capacity for division, making them suitable candidates for the treatment of tissue damage. Additionally, they produce antimicrobial peptides and various cytokines, which enhance their antimicrobial activity. Evidence shows that phages are effective in treating wound-related infections, and phage therapy has proven to be highly effective for patients when administered correctly. The purpose of this article is to explore the use of bacteriophages and mesenchymal stem cells in wound healing and infection management.

Polyketide Synthase 13 (Pks13) Inhibition: A Potential Target for New Class of Anti-tubercular Agents

Tuberculosis is one of the deadly infectious diseases that has resurfaced in multiple/ extensively resistant variants (MDR/XDR), threatening humankind. Today's world has a higher prevalence of tuberculosis (TB) than it has ever had throughout human history. Due to severe adverse effects, the marketed medications are not entirely effective in these forms. So, developing new drugs with a promising target is an immense necessity. Pks13 has emerged as a promising target for the mycobacterium. The concluding step of mycolic acid production involved Pks13, a crucial enzyme that helps form the precursor of mycolic acid via the Claisen-condensation reaction. It has five domains at the active site for targeting the enzyme and is used to test chemical entities for their antitubercular activity. Benzofurans, thiophenes, coumestans, N-phenyl indoles, and β lactones are the ligands that inhibit the Pks13 enzyme, showing potential antitubercular properties.

Management Challenges of Extrapulmonary Nontuberculous Mycobacterial Infection: A Single-Center Case Series and Literature Review

Extrapulmonary nontuberculous mycobacterial (NTM) disease remains largely enigmatic, yet these mycobacteria are increasingly acknowledged as important opportunistic pathogens in humans. Traditionally, NTM infections have been identified across various anatomical locations, with the respiratory system being the most affected and best understood. Historically, extrapulmonary NTM infection was predominantly associated with HIV/AIDS, with Mycobacterium avium lymphadenopathy being the most commonly reported. Today, however, because of the expanding utilization of immunosuppressive therapies and the demographic shift towards an aging population, an increasing number of NTM infections are expected and seen. Hence, a heightened index of suspicion is essential, necessitating a multifaceted approach to identification and drug sensitivity testing to improve treatment outcomes. In extrapulmonary NTM management, expert consultation is strongly recommended to determine the most efficacious treatment regimen, as individualized, patient-tailored therapies are often required. Furthermore, the economic burden of NTM disease is considerable, accompanied by high rates of hospitalization. To optimize the management of these intricate infections, there is an urgent need for comprehensive data on incidence, prevalence, and outcomes. This case-based series delves into the intricate nature of extrapulmonary NTM infections, focusing on both rapid and slow-growing NTM species, and explores therapeutic options, resistance mechanisms, and host-related immunological factors.