Mesenchymal stem cells and infectious diseases: Smarter than drugs

Highly Cytocompatible Polylactic Acid Based Electrospun Microfibers Loaded with Silver Nanoparticles Generated onto Chestnut Shell Lignin for Targeted Antibacterial Activity and Antioxidant Action

Electrospun (e-spun) fibers are generally regarded as powerful tools for cell growth in tissue regeneration applications, and the possibility of imparting functional properties to these materials represents an increasingly pursued goal. We report herein the preparation of hybrid materials in which an e-spun d,l-polylactic acid matrix, to which chitosan or crystalline nanocellulose was added to improve hydrophilicity, was loaded with different amounts of silver(0) nanoparticles (AgNP) generated onto chestnut shell lignin (CSL) (AgNP@CSL). A solvent-free mechanochemical method was used for efficient (85% of the theoretical value by XRD analysis) Ag(0) production from the reduction of AgNO3 by lignin. For comparison, e-spun fibers containing CSL alone were also prepared. SEM and TEM analyses confirmed the presence of AgNP@CSL (average size 30 nm) on the fibers. Different chemical assays indicated that the AgNP@CSL containing fibers exhibited marked antioxidant properties (EC50 1.6 ± 0.1 mg/mL, DPPH assay), although they were halved with respect to those of the CSL containing fibers, as expected because of the efficient silver ion reduction. All the fibers showed high cytocompatibility toward human mesenchymal stem cells (hMSCs) representative of the self-healing process, and their antibacterial properties were tested against the pathogens Escherichia coli (E. coli), Staphylococcus epidermidis, and Pseudomonas aeruginosa. Finally, competitive surface colonization as simulated by cocultures of hMSC and E. coli showed that AgNP@CSL loaded fibers offered the cells a targeted protection from infection, thus well balancing cytocompatibility and antibacterial properties.

Synergic effect of combined xenogeneic mesenchymal stem cells and ceftriaxone on acute septic arthritis

BACKGROUND

This study tested the hypothesis that combined ceftriaxone (Cef) and human umbilical cord-derived mesenchymal stem cells (HUCDMSCs) was better than either therapy for alleviating acute septic arthritis (ASA).

METHODS AND RESULTS

Adult-male C57BL/6 mice were categorized into control group (Clt), group A (ASA only), group B [ASA + Cef (5 mg/kg, IM per day, at days 2 to 16 after ASA induction)], group C [ASA + HUCDMSCs (5 × 105 per mice at days 2, 3, 4 after ASA induction)], and group D (ASA + Cef + HUCDMSCs). Animals were euthanized by day 28. The result demonstrated that the body weight was significantly lower, whereas the ratio of kidney or spleen weight to WB, circulatory WBC count, bacterial colony-formation-unit from circulatory/kidney extraction were significantly higher in group A than in other groups (all P < .001). The proinflammatory cytokines (IL-6/TNF-α) of knee joint fluid were lowest in Clt and significantly and progressively reduced from groups A to D, whereas the circulatory levels of these 2 parameters at the time points of days 3/7/28 exhibited an identical pattern as knee joint fluid among the groups (all P-value < .0001). The scores of vertebral-bone destructions/inflamed synovium were lowest in Clt, highest in group A, significantly higher in group C than in groups B/D, and significantly higher in group C than in group D (all P < .0001).

CONCLUSION

Combined antibiotics and Cef and HUCDMSCs was superior to just one therapy for suppressing circulatory and tissue levels of inflammation and knee joint destruction in ASA.

Bone marrow stromal cell-derived hepcidin has antimicrobial and immunomodulatory activities

Bone marrow stromal cells (BMSCs) have immunomodulatory activities in numerous species and have been used in clinical trials. BMSCs also make antibacterial agents. Since hepcidin is known to have antimicrobial effects in fish, we wondered if it might also be used as an antimicrobial agent by mammalian BMSCs. In the present study, we show hepcidin expression in both mouse (mBMSC) and human BMSCs (hBMSC). We observed a hBMSC hepcidin-dependent degradation of ferroportin in HEK-293 reporter cells in vitro. In human and mouse bone marrows (BM) we detected hepcidin-positive BMSCs in close proximity to hematopoietic progenitors. The conditioned culture medium of hBMSCs significantly reduced bacterial proliferation that was partially blocked by a hepcidin-neutralizing antibody. Similarly, medium in which hepcidin-deficient (Hamp-/-) mouse BMSCs had been grown was significantly less effective in reducing bacterial counts than the medium of wild-type cells. In a zymosan-induced peritonitis mouse model we found that mBMSC-derived hepcidin reduced the number of invading polymorphonuclear (PMN) cells in the peritoneal cavity. Our results show that BMSC-derived hepcidin has antimicrobial properties in vitro and also reduces inflammation in vivo. We conclude that hepcidin should be added to the expanding arsenal of agents available to BMSCs to fight infections and inflammation.

Activated mesenchymal stem cells increase drug susceptibility of methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa

Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are major causes of hospital-acquired infections and sepsis. Due to increasing antibiotic resistance, new treatments are needed. Mesenchymal stem cells (MSCs) have antimicrobial effects, which can be enhanced by preconditioning with antibiotics. This study investigated using antibiotics to strengthen MSCs against MRSA and P. aeruginosa. MSCs were preconditioned with linezolid, vancomycin, meropenem, or cephalosporin. Optimal antibiotic concentrations were determined by assessing MSC survival. Antimicrobial effects were measured by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antimicrobial peptide (AMP) gene expression. Optimal antibiotic concentrations for preconditioning MSCs without reducing viability were 1 μg/mL for linezolid, meropenem, and cephalosporin and 2 μg/mL for vancomycin. In MIC assays, MSCs preconditioned with linezolid, vancomycin, meropenem, or cephalosporin inhibited MRSA or P. aeruginosa growth at lower concentrations than non-preconditioned MSCs (p ≤ 0.001). In MBC assays, preconditioned MSCs showed enhanced bacterial clearance compared to non-preconditioned MSCs, especially when linezolid and vancomycin were used against MRSA (p ≤ 0.05). Preconditioned MSCs showed increased expression of genes encoding the antimicrobial peptide genes hepcidin and LL-37 compared to non-preconditioned MSCs. The highest hepcidin expression was seen with linezolid and vancomycin preconditioning (p ≤ 0.001). The highest LL-37 expression was with linezolid preconditioning (p ≤ 0.001). MSCs' preconditioning with linezolid, vancomycin, meropenem, or cephalosporin at optimal concentrations enhances their antimicrobial effects against MRSA and P. aeruginosa without compromising viability. This suggests preconditioned MSCs could be an effective adjuvant treatment for antibiotic-resistant infections. The mechanism may involve upregulation of AMP genes.

Potential antibacterial activity and healing effect of topical administration of bone marrow and adipose mesenchymal stem cells encapsulated in collagen-fibrin hydrogel scaffold on full-thickness burn wound infection caused by Pseudomonas aeruginosa

Burns injuries are prone to hospital-acquired infections, and Pseudomonas aeruginosa is one of the most common causes of mortality and morbidity in patients with burn injuries. Thus, this study aimed to analyze the effects of topical treatment with bone marrow (BM-MSC) and adipose mesenchymal stem cells (AD-MSC) encapsulated in collagen and fibrin scaffolds in a Balb/c model of burn wound infection. Extraction of stem cells from adipose and bone marrow tissue of rats was performed and cells were characterized using standard methods. Then, collagen, fibrin and collagen-fibrin scaffolds were constructed and the extracted cells were encapsulated in all three scaffolds. Then, 3rd degree burn was induced in mice and 1.5 × 108 (CFU/ml) of P. aeruginosa was introduced to the burn wound. Subsequently, after 24 h of inducing wound infection, encapsulated MSCs were introduced as dressings to burn wound infection and microbial load as well as rate of wound infection healing was measured. The results of this study showed that the use of BM-MSC and AD-MSC encapsulated in collagen-fibrin scaffold reduced the bacteria load down to 54 and 21 CFU/gr, respectively (P < 0.05). Moreover, BM-MSC and AD-MSC encapsulated in collagen-fibrin showed 80% and 75% wound healing, respectively (P < 0.05). Also, we found no significant between cell origin and healing. Encapsulation of MSCs into collagen-fibrin scaffolds could be effective not only against P. aeruginosa infection, but also healing and regeneration of burn wound.

Overview of strategies to improve the antibacterial property of dental implants

The increasing number of peri-implant diseases and the unsatisfactory results of conventional treatment are causing great concern to patients and medical staff. The effective removal of plaque which is one of the key causes of peri-implant disease from the surface of implants has become one of the main problems to be solved urgently in the field of peri-implant disease prevention and treatment. In recent years, with the advancement of materials science and pharmacology, a lot of research has been conducted to enhance the implant antimicrobial properties, including the addition of antimicrobial coatings on the implant surface, the adjustment of implant surface topography, and the development of new implant materials, and significant progress has been made in various aspects. Antimicrobial materials have shown promising applications in the prevention of peri-implant diseases, but meanwhile, there are some shortcomings, which leads to the lack of clinical widespread use of antimicrobial materials. This paper summarizes the research on antimicrobial materials applied to implants in recent years and presents an outlook on the future development.

Statistical study of clinical trials with stem cells and their function in skin wound

Mesenchymal stem cells (MSCs) have been known as a reliable and effective source to repair damaged tissues. The differentiation and self-renewal ability, easy access, immune system modulation capability, and important role in the process of repairing wounds have caused using these cells extensively in wound healing. In this review study, the role of MSCs is debated about different diseases especially in repairing skin wounds. This review article was obtained from 75 basic and trial articles on the PubMed, Google Scholar, and Clinical Trials databases between 2000 and 2022. MSCs are capable of migrating to the wound site and are effective in all stages of wound healing. These cells differentiate into skin cells and also inhibit inflammatory responses, proliferation, and differentiation cells through paracrine messages. They stimulate locally resident precursors, leading to angiogenesis, epithelial regeneration, and granular tissue formation. During maturation stages, these cells decrease fibrosis tissue formation and wound contraction and increase collagen expression and wound tensile strength. The molecular factors of the lesion site change function of these cells and cause MSCs to create a wound healing microenvironment instead of a fibrotic microenvironment. Currently, significant advances have been achieved in the delivery of MSCs to wound sites. These cells are injected intravenously or intradermally, with or without a scaffold. They are also used in the form of spray or hydrogels. Furthermore, the extracellular vesicles and the synergistic environment of these cells alone are effective. Forthcoming studies could lead to more effective treatment strategies for the use of MSCs in wound healing.

Salmonella enhances osteogenic differentiation in adipose-derived mesenchymal stem cells

The potential of mesenchymal stem cells (MSCs) for tissue repair and regeneration has garnered great attention. While MSCs are likely to interact with microbes at sites of tissue damage and inflammation, like in the gastrointestinal system, the consequences of pathogenic association on MSC activities have yet to be elucidated. This study investigated the effects of pathogenic interaction on MSC trilineage differentiation paths and mechanisms using model intracellular pathogen Salmonella enterica ssp enterica serotype Typhimurium. The examination of key markers of differentiation, apoptosis, and immunomodulation demonstrated that Salmonella altered osteogenic and chondrogenic differentiation pathways in human and goat adipose-derived MSCs. Anti-apoptotic and pro-proliferative responses were also significantly upregulated (p &lt; 0.05) in MSCs during Salmonella challenge. These results together indicate that Salmonella, and potentially other pathogenic bacteria, can induce pathways that influence both apoptotic response and functional differentiation trajectories in MSCs, highlighting that microbes have a potentially significant role as influencers of MSC physiology and immune activity.

The effect of mesenchymal stem cell-derived supernatant nasal administration on lung inflammation and immune response in BCG-vaccinated BALB/c mice

Mesenchymal stem cells (MSCs) are among the known cells that can control and modulate immune responses in different circumstances, including autoimmune diseases. Also, various studies have shown that they can prevent and reduces the pulmonary inflammation caused by infectious agents. In the case of tuberculosis and inflammation caused by BCG, the granuloma has destructive effects and improper orientation of the immune response. Therefore, it is possible to prevent airway damage by preventing harmful inflammatory responses and guiding the immune system responses. This study investigates the role of nasal administration of MSCs supernatant by designing an inflammatory model in the BALB/c mice lung with BCG. MSCs are isolated from mice adipose tissue in this study and evaluated for their phenotypic and differentiation properties. After the third passage, these cells' condition medium (CM) was collected. 20 mice were divided into four groups. Group 1 receive BCG (10⁷ CFU in 5 ml volume for 15 min) nasal administration. Group 2 treated with CM, and group 3 initially were treated with CM (in 5 ml volume for 15 min) and, after 24 h, treated with BCG nasal administration. CM treatment was continued every five days for one month. The fourth group of mice was treated with PBS nasal administration of CM and BCG. One week after the last administration, the lung tissue of mice in each group was pathologically examined. In addition, secretion of IL1-β, IL-6, TNF-α, TGF-β, and IL-10 in the alveolar fluid and secretion of IL-4 and IFN-γ cytokines in the supernatant of splenocytes was evaluated by ELISA. The TNF-α/IL-10 ratio in the alveolar lung fluid of the BCG received group is 2/9 and decreased to 0.58 after successive CM treatment. Therefore, it can be concluded that inflammatory responses to BCG infection in the presence of CM are balanced and pave the way for the induction of effective immune responses by reducing lung tissue damage.

Role of Serum Inflammatory Cytokines in Sepsis Rats Following BMSCs Transplantation: Protein Microarray Analysis

Bone marrow stromal cells (BMSCs) have emerged as a potential therapy for sepsis, yet the underlying mechanisms remain unclear. In this study, we investigated the effects of BMSCs on serum inflammatory cytokines in a rat model of lipopolysaccharide (LPS)-induced sepsis. Sepsis was induced by intravenous injection of LPS, followed by transplantation of BMSCs. We monitored survival rates for 72 h and evaluated organ functions, histopathological changes, and cytokines expression. Sepsis rats showed decreased levels of white blood cells, platelets, lymphocyte ratio, and oxygen partial pressure, along with increased levels of neutrophil ratio, carbon dioxide partial pressure, lactic acid, alanine aminotransferase, and aspartate aminotransferase. Histologically, lung, intestine, and liver tissues exhibited congestion, edema, and infiltration of inflammatory cells. However, after BMSCs treatment, there was improvement in organ functions, histopathological injuries, and survival rates. Protein microarray analysis revealed significant changes in the expression of 12 out of 34 inflammatory cytokines. These findings were confirmed by enzyme-linked immunosorbent assay. Pro-inflammatory factors, such as interleukin-1β (IL-1β), IL-1α, tumor necrosis factor-α (TNF-α), tissue inhibitor of metal protease 1 (TIMP-1), matrix metalloproteinase 8 (MMP-8), Leptin, and L-selectin were upregulated in sepsis, whereas anti-inflammatory and growth factors, including IL-4, β-nerve growth factor (β-NGF), ciliary neurotrophic factor (CNTF), interferon γ (IFN-γ), and Activin A were downregulated. BMSCs transplantation led to a decrease in pro-inflammatory cytokines and an increase in anti-inflammatory and growth factors. We summarized relevant molecular signaling pathways that resulted from cytokines in BMSCs for treating sepsis. Our results illustrated that BMSCs could promote tissue repair and improve organ functions and survival rates in sepsis through modulating cytokine networks.

Adipose-Derived Stromal Cells for Chronic Wounds: Scientific Evidence and Roadmap Toward Clinical Practice

Chronic wounds, ie, non-healing ulcers, have a prevalence of ~1% in the general population. Chronic wounds strongly affect the quality of life and generate considerable medical costs. A fraction of chronic wounds will heal within months of appropriate treatment; however, a significant fraction of patients will develop therapy-refractory chronic wounds, leading to chronic pain, infection, and amputation. Given the paucity of therapeutic options for refractory wounds, cell therapy and in particular the use of adipose-derived stromal cells (ASC) has emerged as a promising concept. ASC can be used as autologous or allogeneic cells. They can be delivered in suspension or in 3D cultures within scaffolds. ASC can be used without further processing (stromal vascular fraction of the adipose tissue) or can be expanded in vitro. ASC-derived non-cellular components, such as conditioned media or exosomes, have also been investigated. Many in vitro and preclinical studies in animals have demonstrated the ASC efficacy on wounds. ASC efficiency appears to occurs mainly through their regenerative secretome. Hitherto, the majority of clinical trials focused mainly on safety issues. However more recently, a small number of randomized, well-controlled trials provided first convincing evidences for a clinical efficacy of ASC-based chronic wound therapies in humans. This brief review summarizes the current knowledge on the mechanism of action, delivery and efficacy of ASC in chronic wound therapy. It also discusses the scientific and pharmaceutical challenges to be solved before ASC-based wound therapy enters clinical reality.

TLR-activated mesenchymal stromal cell therapy and antibiotics to treat multi-drug resistant Staphylococcal septic arthritis in an equine model

BACKGROUND

Rapid development of antibiotic resistance necessitates advancement of novel therapeutic strategies to treat infection. Mesenchymal stromal cells (MSC) possess antimicrobial and immunomodulatory properties, mediated through antimicrobial peptide secretion and recruitment of innate immune cells including neutrophils and monocytes. TLR-3 activation of human, canine and equine MSC has been shown to enhance bacterial killing and clearance in vitro, in rodent Staphylococcal biofilm infection models and dogs with spontaneous multi-drug-resistant infections. The objective of this study was to determine if intra-articular (IA) TLR-3-activated MSC with antibiotics improved clinical parameters and reduced bacterial counts and inflammatory cytokine concentrations in synovial fluid (SF) of horses with induced septic arthritis.

METHODS

Eight horses were inoculated in one tarsocrural joint with multidrug-resistant Staphylococcus aureus (S. aureus). Bone marrow-derived MSC from three unrelated donors were activated with TLR-3 agonist polyinosinic, polycytidylic acid (pIC). Recipient horses received MSC plus vancomycin (TLR-MSC-VAN), or vancomycin (VAN) alone, on days 1, 4, 7 post-inoculation and systemic gentamicin. Pain scores, quantitative bacterial counts (SF, synovium), SF analyses, complete blood counts, cytokine concentrations (SF, plasma), imaging changes (MRI, ultrasound, radiographs), macroscopic joint scores and histologic changes were assessed. Results were reported as mean ± SEM.

RESULTS

Pain scores (d7, P=0.01, 15.2±0.2 vs. 17.9±0.5), ultrasound (d7, P=0.03, 9.0±0.6 vs. 11.8±0.5), quantitative bacterial counts (SF d7, P=0.02, 0±0 vs. 3.4±0.4; synovium P=0.003, 0.4±0.4 vs. 162.7±18.4), systemic neutrophil (d4, P=0.03, 4.6±0.6 vs. 7.8±0.6) and serum amyloid A (SAA) (d4, P=0.01, 1,106.0±659.0 vs. 2,858.8±141.3; d7, P=0.02, 761.8±746.2 vs. 2,357.3±304.3), and SF lactate (d7, P<0.0001, 5.4±0.2 vs. 15.0±0.3), SAA (endterm, P=0.01, 0.0 vs. 2,094.0±601.6), IL-6 (P=0.03, 313.0±119.2 vs. 1,328.2±208.9), and IL-18 (P=0.02, 11.1±0.5 vs. 13.3±3.8) were improved in TLR-MSC-VAN vs. VAN horses. Study limitations include the small horse sample size, short study duration, and lack of additional control groups.

CONCLUSIONS

Combined TLR-activated MSC with antibiotic therapy may be a promising approach to manage joint infections with drug resistant bacteria.

Scanning Probe Microscopy Bone Marrow Determination of Steogenic Differentiation of Mesenchymal Stem Cells

To address the question of determining the osteogenic differentiation of mesenchymal stem cells, the bone marrow studies were performed using probe microscopy. All adherent bone marrow was used to isolate the bone marrow mesenchymal stem cells and expanded and purified in vitro. Its morphology under an inverted microscope was observed. We used Zuogui Pills to differentiate the separation methods. Alcian blue staining, modified calcium cobalt alkaline phosphatase staining, and neuron-specific enolase immunohistochemical staining were performed. The experimental results are shown below. The morphology of the isolated and purified cells was analyzed with an inverted microscope, and the isolated and purified cells were analyzed with Zuogui Pill. Alcian blue staining, modified calcium cobalt alkaline phosphatase staining, and neuron-specific enolase immunohistochemical staining confirmed that the cells differentiated into cartilage and osteoblasts, and the cell structure and morphology were similar to those of the bone marrow mesenchymal stem cells. The results showed that the adherent mode of cells obtained from the whole bone marrow was the rat bone marrow mesenchymal stem cells, and the Zuogui Pills could induce multidirectional differences in the bone marrow mesenchymal stem cells.

Human Mesenchymal Stem/Stromal Cells in Immune Regulation and Therapy

Studies of mesenchymal stem (or stromal) cells (MSCs) have moved from bedside to bench and back again. The stromal cells or fibroblasts are found in all tissues and participate in building the extracellular matrix (ECM). Bone marrow (BM)-derived MSCs have been studied for more than 50 years and have multiple roles. They function as stem cells and give rise to bone, cartilage, and fat in the BM (these are stem cells); support hematopoiesis (pericytes); and participate in sensing environmental changes and balancing pro- and anti-inflammatory conditions. In disease states, they migrate to sites of injury and release cytokines, hormones, nucleic acids depending on the microenvironment they find. Clinicians have begun to exploit these properties of BM, adipose tissue, and umbilical cord MSCs because they are easy to harvest and expand in culture. In this review, I describe the uses to which MSCs have been put, list ongoing clinical trials by organ system, and outline how MSCs are thought to regulate the innate and adaptive immune systems. I will discuss some of the reasons why clinical applications are still lacking. Much more work will have to be done to find the sources, doses, and culture conditions needed to exploit MSCs optimally and learn their healing potential. They are worth the effort.

Bone marrow mesenchymal stem cells offer an immune-privileged niche to Cutibacterium acnes in case of implant-associated osteomyelitis

Considered as some of the most devastating complications, Cutibacterium acnes (C. acnes)-related osteomyelitis are among the hardest infections to diagnose and treat. Mesenchymal stem cells (MSCs) secrete number of immunomodulatory and antimicrobial soluble factors, making them an attractive treatment for bacterial infection. In this study, we examined MSCs/C. acnes interaction and analyzed the subsequent MSCs and bacteria's behaviors. Human bone marrow-derived MSCs were infected by C. acnes clinical strain harvested from non-infected bone site. Following 3 h of interaction, around 4% of bacteria were found in the intracellular compartment. Infected MSCs increased the secretion of prostaglandin E2 and indolamine 2,3 dioxygenase immunomodulatory mediators. Viable intracellular bacteria analyzed by infrared spectroscopy and atomic force microscopy revealed deep modifications in the wall features. In comparison with unchallenged bacteria, the viable intracellular bacteria showed (i) an increase in biofilm formation on orthopaedical-based materials, (ii) an increase in the invasiveness of osteoblasts and (iii) persistence in macrophage, suggesting the acquisition of virulence factors. Overall, these results showed a direct impact of C. acnes on bone marrow-derived MSCs, suggesting that blocking the C. acnes/MSCs interactions may represent an important new approach to manage chronic osteomyelitis infections. STATEMENT OF SIGNIFICANCE: The interaction of bone commensal C. acnes with bone marrow mesenchymal stem cells induces modifications in C. acnes wall characteristics. These bacteria increased (i) the biofilm formation on orthopaedical-based materials, (ii) the invasiveness of bone forming cells and (iii) the resistance to macrophage clearance through the modification of the wall nano-features and/or the increase in catalase production.

Stem Cells Therapy for COVID-19: A Systematic Review and Meta-Analysis

Introduction: Vaccination seems to be a good solution for preventing and controlling coronavirus disease (COVID-19) pandemic, but still there are some challenges in COVID-19 vaccination. Investigating new therapeutic options for COVID-19 is necessary. The current study aimed to evaluate the safety and efficacy of stem cells in treating patients with COVID-19.

Methods: We reviewed the relevant scientific literature published up to April 1, 2021. The pooled risk ratio (RR) with 95% CI was assessed using a fixed or random-effect model. We considered P < 0.05 as statistically significant for publication bias. Data were analyzed by Comprehensive Meta-Analysis software, Version 2.0 (Biostat, Englewood, NJ).

Results: After reviewing 1,262 records, we identified 10 studies that met the inclusion criteria. The analysis showed that stem cell therapy could significantly reduce the mortality rate (RR 0.471, 95% CI: 0.270–0.821) and morbidity (RR 0.788, 95% CI: 0.626–0.992) in patients with COVID-19; compared with the control group.

Conclusions: The present study suggests that stem cell therapy has a remarkable effect on reducing mortality and morbidity of patients with COVID-19. Further large-scale studies are needed to approve these results. Defining a protocol for stem cell therapy in patients with COVID-19 can lead to achieving the best clinical outcomes.

Regulation of the mesenchymal stem cell fate by interleukin-17: Implications in osteogenic differentiation

Bone regeneration is a tightly regulated process that ensures proper repair and functionality after injury. The delicate balance between bone formation and resorption is governed by cytokines and signaling molecules released during the inflammatory response. Interleukin (IL)-17A, produced in the early phase of inflammation, influences the fate of osteoprogenitors. Due to their inherent capacity to differentiate into osteoblasts, mesenchymal stem/stromal cells (MSCs) contribute to bone healing and regeneration. This review presents an overview of IL-17A signaling and the leading cellular and molecular mechanisms by which it regulates the osteogenic differentiation of MSCs. The main findings demonstrating IL-17A’s influence on osteoblastogenesis are described. To this end, divergent information exists about the capacity of IL-17A to regulate MSCs’ osteogenic fate, depending on the tissue context and target cell type, along with contradictory findings in the same cell types. Therefore, we summarize the data showing both the pro-osteogenic and anti-osteogenic roles of IL-17, which may help in the understanding of IL-17A function in bone repair and regeneration.

Immunomodulatory effects of mesenchymal stem cell-conditioned media on lipopolysaccharide of Vibrio cholerae as a vaccine candidate

BACKGROUND

Vibrio cholerae is the causative agent of cholera, which is commonly associated with high morbidity and mortality, and presents a major challenge to healthcare systems throughout the world. Lipopolysaccharide (LPS) is required for full protection against V. cholerae but can induce inflammation and septic shock. Mesenchymal stem cells (MSCs) are currently used to treat infectious and inflammatory diseases. Therefore, this study aimed to evaluate the immune-modulating effects of the LPS-MSC-conditioned medium (CM) on V. cholerae LPS immunization in a murine model.

METHODS

After preconditioning MSCs with LPS, mice were immunized intraperitoneally on days 0 and 14 with the following combinations: LPS + LPS-MSC-CM; detoxified LPS (DLPS) + MSC-CM; LPS + MSC sup; LPS; LPS-MSC-CM; MSC supernatant (MSC sup); and PBS. The mouse serum and saliva samples were collected to evaluate antibody (serum IgG and saliva IgA) and cytokine responses (TNF-α, IL-10, IL-6, TGF-β, IL-4, IL-5, and B-cell activating factor (BAFF)).

RESULTS

The LPS + LPS-MSC-CM significantly increased total IgG and IgA compared to other combinations (P < 0.001). TNF-α levels, in contrast to IL-10 and TGF-β, were reduced significantly in mice receiving the LPS + LPS-MSC-CM compared to mice receiving only LPS. IL-4, IL-5, and BAFF levels significantly increased in mice receiving increased doses of LPS + LPS-MSC-CM compared to those who received only LPS. The highest vibriocidal antibody titer (1:64) was observed in LPS + LPS-MSC-CM-immunized mice and resulted in a significant improvement in survival in infant mice infected by V. cholerae O1.

CONCLUSIONS

The LPS-MSC-CM modulates the immune response to V. cholerae LPS by regulating inflammatory and anti-inflammatory responses and inducing vibriocidal antibodies, which protect neonate mice against V. cholerae infection.

The role of interferon-gamma and interferon-gamma receptor in tuberculosis and nontuberculous mycobacterial infections

Mycobacterium tuberculosis (Mtb) and nontuberculous mycobacteria (NTM) remain the leading causes of lung disease and mortality worldwide. Interferon-gamma (IFN-γ) and its receptor (IFN-γR) play a key role in mediating immunity against Mtb and NTM. This study was conducted as a systematic review; all information was collected from databases such as: PubMed, Scopus, Medline, SID, and medical databases. Finally, all the collected data were reviewed, and all content was categorized briefly. There is growing evidence that IFN-γ plays an important role in host defense against these two intracellular pathogens by activating macrophages. In addition, IFN-γ has been shown to be an integral part of various antibacterial methods such as granuloma formation and phagosome-lysosome fusion, both of which lead to the death of intracellular Mycobacterium. As a result, its absence is associated with overgrowth of intracellular pathogens and disease caused by Mtb or Mycobacterium nontuberculosis. We also look at the role of IFN-γR in Mtb or NTM because IFN-γ acts through IFN-γR. Finally, we introduce new approaches to the treatment of M. tuberculosis complex (MTC) and NTM disease, such as cell and gene-based therapies that work by modulating IFN-γ and IFN-γR.

Staphylococcus aureus Vaccine Research and Development: The Past, Present and Future, Including Novel Therapeutic Strategies

Staphylococcus aureus is one of the most important human pathogens worldwide. Its high antibiotic resistance profile reinforces the need for new interventions like vaccines in addition to new antibiotics. Vaccine development efforts against S. aureus have failed so far however, the findings from these human clinical and non-clinical studies provide potential insight for such failures. Currently, research is focusing on identifying novel vaccine formulations able to elicit potent humoral and cellular immune responses. Translational science studies are attempting to discover correlates of protection using animal models as well as in vitro and ex vivo models assessing efficacy of vaccine candidates. Several new vaccine candidates are being tested in human clinical trials in a variety of target populations. In addition to vaccines, bacteriophages, monoclonal antibodies, centyrins and new classes of antibiotics are being developed. Some of these have been tested in humans with encouraging results. The complexity of the diseases and the range of the target populations affected by this pathogen will require a multipronged approach using different interventions, which will be discussed in this review.

Mesenchymal stem cells support delivery and boost the efficacy of oncolytic reoviruses in TC-1 tumor cells

Cancer has remained a major health problem around the world. Mesenchymal stem cells (MSCs)-based therapy exhibits a therapeutic effect via different mechanisms. By using MSCs as carrier cells, the major problem of clearance of oncolytic viruses is resolved by neutralizing antibodies before they react with cancer cells. The aim of this study was to characterize the effect of infected MSCs by reovirus type-3 Dearing (T3D) for in vitro cancer therapy. Adipose-derived MSCs (AD-MSCs) were infected with reovirus T3D and its biological properties were evaluated. Then, the effects of reovirus-infected AD-MSCs on cytokine profile, nitric oxide (NO) production, and apoptosis induction in TC-1 cells were assessed. Our results indicated that the differentiation potential of AD-MSCs was affected by reovirus. However, phenotypes were not affected after infection. Then, the effects of reovirus-infected AD-MSCs in TC-1 cells showed an increased amount of tumor necrosis factor-alpha (TNF-α) and NO production and a decreased amount of transforming growth factor-beta 1 (TGF-β1) and interleukin-10 (IL-10). Moreover, apoptosis significantly increased via coculturing of TC-1 cells with infected AD-MSCs, compared with control, and both internal and external apoptosis pathways are activated in experimental groups. In conclusion, the data showed that with increasing TNF-α and NO production and reducing IL-10 and TGF-β production, AD-MSCs can enhance the oncolytic effect of reovirus in cancer cells. Furthermore, the results suggested that AD-MSCs can be used as effective carrier cells candidate for reovirus T3D to maximize their anticancer cell activity.

Recent Trends in Multipotent Human Mesenchymal Stem/Stromal Cells: Learning from History and Advancing Clinical Applications

Early cell biology reports demonstrated the presence of cells with stem-like properties in bone marrow, with both hematopoietic and mesenchymal lineages. Over the years, various investigations have purified and characterized mesenchymal stromal/stem cells (MSCs) from different human tissues as cells with multilineage differentiation potential under the appropriate conditions. Due to their appealing characteristics and versatile potentials, MSCs are leveraged in many applications in medicine such as oncology, bioprinting, and as recent as therapeutics discovery and innovation for COVID-19. To date, studies indicate that MSCs have varied differentiation capabilities into different cell types, and demonstrate immunomodulating and anti-inflammatory properties. Different microenvironments or niche for MSCs and their resulting heterogeneity may influence attendant cellular behavior and differentiation capacity. The potential clinical applications of MSCs and exosomes derived from these cells have led to an avalanche of research reports on their properties and hundreds of clinical trials being undertaken. There is ample reason to think, as discussed in this expert review that the future looks bright and promising for MSC research, with many clinical trials under way to ascertain their clinical utility. This review provides a synthesis of the latest advances and trends in MSC research to allow for broad and critically informed use of MSCs. Early observations of the presence of these cells in the bone marrow and their remarkable differentiation capabilities and immunomodulation are also presented.

Impact of Three Different Serum Sources on Functional Properties of Equine Mesenchymal Stromal Cells

Culture and expansion of equine mesenchymal stromal cells (MSCs) are routinely performed using fetal bovine serum (FBS) as a source of growth factors, nutrients, and extracellular matrix proteins. However, the desire to minimize introduction of xenogeneic bovine proteins or pathogens and to standardize cellular products intended for clinical application has driven evaluation of alternatives to FBS. Replacement of FBS in culture for several days before administration has been proposed to reduce antigenicity and potentially prolong survival after injection. However, the functional consequences of MSC culture in different serum types have not been fully evaluated. The objective of this study was to compare the immunomodulatory and antibacterial properties of MSCs cultured in three serum sources: FBS or autologous or allogeneic equine serum. We hypothesized that continuous culture in FBS would generate MSCs with improved functionality compared to equine serum and that there would not be important differences between MSCs cultured in autologous vs. allogeneic equine serum. To address these questions, MSCs from three healthy donor horses were expanded in medium with FBS and then switched to culture in FBS or autologous or allogeneic equine serum for 72 h. The impact of this 72-h culture period in different sera on cell viability, cell doubling time, cell morphology, bactericidal capability, chondrogenic differentiation, and production of cytokines and antimicrobial peptides was assessed. Altering serum source did not affect cell viability or morphology. However, cells cultured in FBS had shorter cell doubling times and secreted more interleukin 4 (IL-4), IL-5, IL-17, RANTES, granulocyte–macrophage colony-stimulating factor, fibroblast growth factor 2, eotaxin, and antimicrobial peptide cathelicidin/LL-37 than cells cultured in either source of equine serum. Cells cultured in FBS also exhibited greater spontaneous bactericidal activity. Notably, significant differences in any of these parameters were not observed when autologous vs. allogeneic equine serum was used for cell culture. Chondrogenic differentiation was not different between different serum sources. These results indicate that MSC culture in FBS will generate more functional cells based on a number of parameters and that the theoretical risks of FBS use in MSC culture should be weighed against the loss of MSC function likely to be incurred from culture in equine serum.

MSCs and Inflammatory Cells Crosstalk in Regenerative Medicine: Concerted Actions for Optimized Resolution Driven by Energy Metabolism

Mesenchymal stromal cells (MSCs) are currently widely used in cell based therapy regarding to their remarkable efficacy in controlling the inflammatory status in patients. Despite recent progress and encouraging results, inconstant therapeutic benefits are reported suggesting that significant breakthroughs in the understanding of MSCs immunomodulatory mechanisms of action remains to be investigated and certainly apprehended from original point of view. This review will focus on the recent findings regarding MSCs close relationship with the innate immune compartment, i.e. granulocytes and myeloid cells. The review will also consider the intercellular mechanism of communication involved, such as factor secretion, cell-cell contact, extracellular vesicles, mitochondria transfer and efferocytosis. Immune-like-properties of MSCs supporting part of their therapeutic effect in the clinical setting will be discussed, as well as their potentials (immunomodulatory, anti-bacterial, anti-inflammatory, anti-oxidant defenses and metabolic adaptation…) and effects mediated, such as cell polarization, differentiation, death and survival on various immune and tissue cell targets determinant in triggering tissue regeneration. Their metabolic properties in term of sensing, reacting and producing metabolites influencing tissue inflammation will be highlighted. The review will finally open to discussion how ongoing scientific advances on MSCs could be efficiently translated to clinic in chronic and age-related inflammatory diseases and the current limits and gaps that remain to be overcome to achieving tissue regeneration and rejuvenation.

Toll-like receptor activation of equine mesenchymal stromal cells to enhance antibacterial activity and immunomodulatory cytokine secretion

OBJECTIVE

To evaluate effects of Toll-like and nucleotide-binding oligomerization domain (NOD)-like receptor (TLR, NLR) ligand stimulation of equine mesenchymal stromal cells (MSCs) on antibacterial and immunomodulatory properties in vitro.

STUDY DESIGN

Controlled laboratory study.

SAMPLE POPULATION

Equine bone-marrow-derived MSCs (three horses).

METHODS

MSCs were stimulated with TLR (polyinosinic:polycytidylic acid [pIC] and lipopolysaccharide [LPS]) and NLR agonists (γ-d-Glu-mDAP [IE-DAP]) for 2 h, and plated at 1 × 10⁵ cells/well 24 h. MSC-conditioned media (MSC-CM) were collected and assessed for antimicrobial peptide cathelicidin/LL-37 production, bactericidal action against multidrug-resistant planktonic and biofilm Staphylococcus aureus and neutrophil phagocytosis. Bacterial growth was measured by plating bacteria and counting viable colonies, reading culture absorbance, and live-dead staining with confocal microscopy imaging. Following initial comparison of activating stimuli, TLR3-agonist pIC protocols (cell density during activation and plating, culture time, %serum) were further optimized for bactericidal activity and secretion of interleukin-8 (IL-8), monocyte-chemoattractant-protein (MCP-1), and cathelicidin/LL37.

RESULTS

MSCs stimulation with pIC (p = .004) and IE-DAP (p = .03) promoted increased bactericidal activity, evidenced by reduced viable planktonic colony counts. PIC stimulation (2 × 10⁶ cells/ml, 2 h, 10 μg/ml) further suppressed biofilm formation (p = .001), enhanced neutrophil bacterial phagocytosis (p = .009), increased MCP-1 secretion (p < .0001), and enhanced cathelicidin/LL-37 production, which was apparent when serum concentration in media was reduced to 1% (p = .01) and 2.5% (p = .05).

CONCLUSION

TLR-3 pIC MSCs activation was most effective to enhance antibacterial and cytokine responses, which were affected by serum reduction.

CLINICAL SIGNIFICANCE

In vitro TLR-3 activation of equine MSCs tested here may be a strategy to improve antibacterial properties of MSCs to treat antibiotic-resistant infections.

Mesenchymal stromal cells for the treatment of ocular autoimmune diseases

Mesenchymal stromal cells, commonly referred to as MSCs, have emerged as a promising cell-based therapy for a range of autoimmune diseases thanks to several therapeutic advantages. Key among these are: 1) the ability to modulate innate and adaptive immune responses and to promote tissue regeneration, 2) the ease of their isolation from readily accessible tissues and expansion at scale in culture, 3) their low immunogenicity enabling use as an allogeneic "off-the-shelf" product, and 4) MSC therapy's safety and feasibility in humans, as demonstrated in more than one thousand clinical trials. Evidence from preclinical studies and early clinical trials indicate the therapeutic potential of MSCs and their derivatives for efficacy in ocular autoimmune diseases such as autoimmune uveoretinitis and Sjögren's syndrome-related dry eye disease. In this review, we provide an overview of the current understanding of the therapeutic mechanisms of MSCs, and summarize the results from preclinical and clinical studies that have used MSCs or their derivatives for the treatment of ocular autoimmune diseases. We also discuss the challenges to the successful clinical application of MSC therapy, and suggest strategies for overcoming them.

How microbes read the map: Effects of implant topography on bacterial adhesion and biofilm formation

Microbes have remarkable capabilities to attach to the surface of implanted medical devices and form biofilms that adversely impact device function and increase the risk of multidrug-resistant infections. The physicochemical properties of biomaterials have long been known to play an important role in biofilm formation. More recently, a series of discoveries in the natural world have stimulated great interest in the use of 3D surface topography to engineer antifouling materials that resist bacterial colonization. There is also increasing evidence that some medical device surface topographies, such as those designed for tissue integration, may unintentionally promote microbial attachment. Despite a number of reviews on surface topography and biofilm control, there is a missing link between how bacteria sense and respond to 3D surface topographies and the rational design of antifouling materials. Motivated by this gap, we present a review of how bacteria interact with surface topographies, and what can be learned from current laboratory studies of microbial adhesion and biofilm formation on specific topographic features and medical devices. We also address specific biocompatibility considerations and discuss how to improve the assessment of the anti-biofilm performance of topographic surfaces. We conclude that 3D surface topography, whether intended or unintended, is an important consideration in the rational design of safe medical devices. Future research on next-generation smart antifouling materials could benefit from a greater focus on translation to real-world applications.

Mesenchymal Stromal Cells as Potential Antimicrobial for Veterinary Use-A Comprehensive Review

The emergence of “superbugs” resistant to antimicrobial medications threatens populations both veterinary and human. The current crisis has come about from the widespread use of the limited number of antimicrobials available in the treatment of livestock, companion animal, and human patients. A different approach must be sought to find alternatives to or enhancements of present conventional antimicrobials. Mesenchymal stromal cells (MSC) have antimicrobial properties that may help solve this problem. In the first part of the review, we explore the various mechanisms at work across species that help explain how MSCs influence microbial survival. We then discuss the findings of recent equine, canine, and bovine studies examining MSC antimicrobial properties in which MSCs are found to have significant effects on a variety of bacterial species either alone or in combination with antibiotics. Finally, information on the influence that various antimicrobials may have on MSC function is reviewed. MSCs exert their effect directly through the secretion of various bioactive factors or indirectly through the recruitment and activation of host immune cells. MSCs may soon become a valuable tool for veterinarians treating antimicrobial resistant infections. However, a great deal of work remains for the development of optimal MSC production conditions and testing for efficacy on different indications and species.

Mesenchymal stem cells prevent overwhelming inflammation and reduce infection severity via recruiting CXCR3+ regulatory T cells

Objectives

Mesenchymal stem cells (MSCs) have shown great potential in treating autoimmune diseases (ADs). Unlike the traditional immunosuppressants, which inadvertently impair patients' antimicrobial immunity, MSCs reduce the incidence and duration of respiratory infection. However, the underlying mechanisms are unknown.

Methods

To investigate how MSCs regulate the lung immunity and improve the defence against respiratory infection, we infected MSC‐treated wild‐type and lupus‐prone mice with Haemophilus influenzae intranasally and determined the clearance of bacteria. Tissue damage and inflammatory cytokines were measured by H&E staining and ELISA separately. Immune cell subsets in the tissues were analysed by flow cytometry.

Results

MSC pretreatment prevented overwhelming inflammation and accelerated bacterial clearance in both wild‐type and lupus‐prone mice. Tregs increased dramatically in the lung after MSC treatment. Adoptive transfer of Tregs isolated from MSC‐treated mice offered similar protection, while deletion of Tregs abrogated the protective effects of MSCs. The majority of the intravenously injected MSCs were engulfed by lung phagocytes, which in turn produced CXCL9 and CXCL10 and recruited tremendous CXCR3⁺ Tregs into the lung. Compared with their CXCR3⁻ counterparts, CXCR3⁺ Tregs displayed enhanced proliferation and stronger inhibitory functions. Neutralisation of CXCL9 and CXCL10 significantly downregulated the migration of CXCR3⁺ Tregs and eliminated the benefits of MSC pretreatment.

Conclusion

Here, we showed that by recruiting CXCR3⁺ Tregs, MSC treatment restricted the overactivation of inflammatory responses and prevented severe symptoms caused by infection. By discovering this novel property of MSCs, our study sheds light on optimising long‐term immunosuppressive regimen for autoimmune diseases and other immune disorders.

Biopolymers-calcium phosphate antibacterial coating reduces the pathogenicity of internalized bacteria by mesenchymal stromal cells

A multifunctional material system that kills bacteria and drives bone healing is urgently sought to improve bone prosthesis. Herein, the osteoinductive coating made of calcium phosphate/chitosan/hyaluronic acid, named Hybrid, was proposed as an antibacterial substrate for stromal cell adhesion. This Hybrid coating possesses a contact-killing effect reducing by 90% the viability of Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa) strains after 48 h of contact. In addition to the production of immunomodulatory mediators, Wharton's jelly (WJ-SCs), dental pulp (DPSCs) and bone marrow (BM-MSCs) derived stromal cells were able to release antibacterial and antibiofilm agents effective against S. aureus and P. aeruginosa strains, respectively. Studying the effect of the Hybrid coating on the internalization of S. aureus by the stromal cells, in acute-mimicking bone infection, highlighted an increase in the bacteria internalization by DPSCs and BM-MSCs when cultured on the Hybrid coating versus uncoated glass. Despite the internalization, Hybrid coating showed a beneficial effect by reducing the pathogenicity of the internalized bacteria. The formation of biofilm was reduced by at least 50% in comparison to internalized bacteria by stromal cells on uncoated glass. This work opens the route for the development of innovative antibacterial coatings by taking into account the internalization of bacteria by stromal cells.

Immunomodulation and Regeneration Properties of Dental Pulp Stem Cells: A Potential Therapy to Treat Coronavirus Disease 2019

The coronavirus disease 2019 (COVID-19) pandemic, originating from Wuhan, China, is known to cause severe acute respiratory symptoms. The occurrence of a cytokine storm in the lungs is a critical step in the disease pathogenesis, as it causes pathological lesions, pulmonary edema, and acute respiratory distress syndrome, potentially resulting in death. Currently, there is no effective treatment that targets the cytokine storm and helps regenerate the damaged tissue. Mesenchymal stem cells (MSCs) are known to act as anti-inflammatory/immunomodulatory candidates and activate endogenous regeneration. As a result, MSC therapy is a potential treatment approach for COVID-19. Intravenous injection of clinical-grade MSCs into COVID-19 patients can induce an immunomodulatory response along with improved lung function. Dental pulp stem cells (DPSCs) are considered a potential source of MSCs for immunomodulation, tissue regeneration, and clinical application. Although some current clinical trials have treated COVID-19 patients with DPSCs, this therapy has not been approved. Here, we review the potential use of DPSCs and their significance in the development of a therapy for COVID-19.

Obesity and COVID-19: Molecular Mechanisms Linking Both Pandemics

The coronavirus disease 2019 COVID-19 pandemic is rapidly spreading worldwide and is becoming a major public health crisis. Increasing evidence demonstrates a strong correlation between obesity and the COVID-19 disease. We have summarized recent studies and addressed the impact of obesity on COVID-19 in terms of hospitalization, severity, mortality, and patient outcome. We discuss the potential molecular mechanisms whereby obesity contributes to the pathogenesis of COVID-19. In addition to obesity-related deregulated immune response, chronic inflammation, endothelium imbalance, metabolic dysfunction, and its associated comorbidities, dysfunctional mesenchymal stem cells/adipose-derived mesenchymal stem cells may also play crucial roles in fueling systemic inflammation contributing to the cytokine storm and promoting pulmonary fibrosis causing lung functional failure, characteristic of severe COVID-19. Moreover, obesity may also compromise motile cilia on airway epithelial cells and impair functioning of the mucociliary escalators, reducing the clearance of severe acute respiratory syndrome coronavirus (SARS-CoV-2). Obese diseased adipose tissues overexpress the receptors and proteases for the SARS-CoV-2 entry, implicating its possible roles as virus reservoir and accelerator reinforcing violent systemic inflammation and immune response. Finally, anti-inflammatory cytokines like anti-interleukin 6 and administration of mesenchymal stromal/stem cells may serve as potential immune modulatory therapies for supportively combating COVID-19. Obesity is conversely related to the development of COVID-19 through numerous molecular mechanisms and individuals with obesity belong to the COVID-19-susceptible population requiring more protective measures.

Combinational therapy with antibiotics and antibiotic-loaded adipose-derived stem cells reduce abscess formation in implant-related infection in rats

Implant-related infection is difficult to treat without extended antibiotic courses. However, the long-term use of antibiotics has led to the development of multidrug- and methicillin-resistant Staphylococcusaureus. Thus, alternatives to conventional antibiotic therapy are needed. Recently, mesenchymal stem cells have been shown to have antimicrobial properties. This study aimed to evaluate the antimicrobial activity and therapeutic effect of local treatment with antibiotic-loaded adipose-derived stem cells (ADSCs) plus an antibiotic in a rat implant-associated infection model. Liquid chromatography/tandem mass spectrometry revealed that ADSCs cultured in the presence of ciprofloxacin for 24 h showed time-dependent antibiotic loading. Next, we studied the therapeutic effects of ADSCs and ciprofloxacin alone or in combination in an implant-related infection rat model. The therapeutic effects of ADSCs plus antibiotics, antibiotics, and ADSCs were compared with no treatment as a control. Rats treated with ADSCs plus ciprofloxacin had the lowest modified osteomyelitis scores, abscess formation, and bacterial burden on the implant among all groups (P < 0.05). Thus, local treatment with ADSCs plus an antibiotic has an antimicrobial effect in implant-related infection and decrease abscess formation. Thus, our findings indicate that local administration of ADSCs with antibiotics represents a novel treatment strategy for implant-associated osteomyelitis.

Evaluation of Nisin and LL-37 Antimicrobial Peptides as Tool to Preserve Articular Cartilage Healing in a Septic Environment

Cartilage repair still represents a challenge for clinicians and only few effective therapies are nowadays available. In fact, surgery is limited by the tissue poor self-healing capacity while the autologous transplantation is often forsaken due to the poor in vitro expansion capacity of chondrocytes. Biomaterials science offers a unique alternative based on the replacement of the injured tissue with an artificial tissue-mimicking scaffold. However, the implantation surgical practices and the scaffold itself can be a source of bacterial infection that currently represents the first reason of implants failure due to the increasing antibiotics resistance of pathogens. So, alternative antibacterial tools to prevent infections and consequent device removal are urgently required. In this work, the role of Nisin and LL-37 peptides has been investigated as alternative to antibiotics to their antimicrobial performances for direct application at the surgical site or as doping chemicals for devices aimed at articular cartilage repair. First, peptides cytocompatibility was investigated toward human mesenchymal stem cells to determine safe concentrations; then, the broad-range antibacterial activity was verified toward the Gram-positive Staphylococcus aureus and Staphylococcus epidermidis as well as the Gram-negative Escherichia coli and Aggregatibacter actinomycetemcomitans pathogens. The peptides selective antibacterial activity was verified by a cells-bacteria co-culture assay, while chondrogenesis was assayed to exclude any interference within the differentiation route to simulate the tissue repair. In the next phase, the experiments were repeated by moving from the cell monolayer model to 3D cartilage-like spheroids to revisit the peptides activity in a more physiologically relevant environment model. Finally, the spheroid model was applied in a perfusion bioreactor to simulate an infection in the presence of circulating peptides within a physiological environment. Results suggested that 75 μg/ml Nisin can be considered as a very promising candidate since it was shown to be more cytocompatible and potent against the investigated bacteria than LL-37 in all the tested models.

Medicinal signaling cells: A potential antimicrobial drug store

Medicinal signaling cells (MSCs) are multipotent cells derived from mammalian bone marrow and periosteum that can be extended in culture. They can keep their ability in vitro to form a variety of mesodermal phenotypes and tissues. Over recent years, there has been great attention over MSCs since they can impact the organ transplantation as well as autoimmune and bacterial diseases. MSCs can secrete different bioactive factors such as growth factors, antimicrobial peptides/proteins and cytokines that can suppress the immune system and prevent infection via direct and indirect mechanisms. Moreover, MSCs are able to increase bacterial clearance in sepsis models by producing antimicrobial peptides such as defensins, cathelicidins, lipocalin and hepcidin. It is the aim of the present review to focus on the antibacterial effector functions of MSCs and their mechanisms of action against the pathogenic microbes.

Use of Autologous Cord Blood Mononuclear Cells Infusion for the Prevention of Bronchopulmonary Dysplasia in Extremely Preterm Neonates: A Study Protocol for a Placebo-Controlled Randomized Multicenter Trial [NCT03053076]

Background: Despite the rapid advance of neonatal care, bronchopulmonary dysplasia (BPD) remains a significant burden for the preterm population, and there is a lack of effective intervention. Stem cell depletion because of preterm birth is regarded as one of the underlying pathological mechanisms for the arrest of alveolar and vascular development. Preclinical and small-sample clinical studies have proven the efficacy and safety of stem cells in treating and preventing lung injury. However, there are currently no randomized clinical trials (RCTs) investigating the use of autologous cord blood mononuclear cells (ACBMNC) for the prevention of BPD in premature infants. The purpose of this study is to investigate the effects of infusion of ACBMNC for the prevention of BPD in preterm neonates <28 weeks. Methods: In this prospective, randomized controlled double-blind multi-center clinical trial, 200 preterm neonates <28 weeks gestation will be randomly assigned to receive intravenous ACBMNC infusion (5 × 107 cells/kg) or placebo (normal saline) within 24 h after birth in a 1:1 ratio using a central randomization system. The primary outcome will be survival without BPD at 36 weeks of postmenstrual age or at discharge, whichever comes first. The secondary outcomes will include the mortality rate, other common preterm complication rates, respiratory support duration, length, and cost of hospitalization, and long-term outcomes after a 2-year follow-up. Conclusion: This will be the first randomized, controlled, blinded trial to evaluate the efficacy of ACBMNC infusion as a prevention therapy for BPD. The results of this trial will provide valuable clinical evidence for recommendations on the management of BPD in extremely preterm infants. Clinical Trial Registration: ClinicalTrials.gov, NCT03053076, registered 02/14/2017, retrospectively registered, https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S0006WN4&selectaction=Edit&uid=U0002PLA&ts=2&cx=9y23d4 (Additional File 2).

Interaction of Cutibacterium acnes with human bone marrow derived mesenchymal stem cells: a step toward understanding bone implant- associated infection development

Crosstalk between mesenchymal stem cells (MSCs) and bacteria plays an important role in regulating the regenerative capacities of MSCs, fighting infections, modulating immune responses and maintaining tissue homeostasis. Commensal Cutibacterium acnes (C. acnes) bacterium becomes an opportunistic pathogen causing implant-associated infections. Herein, we examined MSCs/C. acnes interaction and analysed the subsequent bacteria and MSCs behaviours following infection. Human bone marrow derived MSCs were infected by two clinical and one laboratory C. acnes strains. Following 3h of interaction, all bacterial strains were able to invade MSCs. Viable intracellular bacteria acquired virulence factors by increasing biofilm formation and/or by affecting macrophage phagocytosis. Although the direct and indirect (through neutrophil stimulation) antibacterial effects of the MSCs secretome were not enhanced following C. acnes infection, ELISA analysis revealed that C. acnes clinical strains are able to license MSCs to become immunosuppressive cell-like by increasing the secretion of IL-6, IL-8, PGE-2, VEGF, TGF-β and HGF. Overall, these results showed a direct impact of C. acnes on bone marrow derived MSCs, providing new insights into the development of C. acnes during implant-associated infections. STATEMENT OF SIGNIFICANCE: The originality of this work relies on the study of relationship between human bone marrow derived mesenchymal stem cells (MSCs) phenotype and C. acnes clinical strains virulence following cell infection. Our major results showed that C. acnes are able to invade MSCs, inducing a transition of commensal to an opportunistic pathogen behaviour. Although the direct and indirect antibacterial effects were not enhanced following C. acnes infection, secretome analysis revealed that C. acnes clinical strains were able to license MSCs to become immunosuppressive and anti-fibrotic cell-like. These results showed a direct impact of C. acnes on bone marrow derived MSCs, providing new insights into the development of C. acnes during associated implant infections.

Bone Marrow-Derived Mesenchymal Stromal Cells (MSCs) Modulate the Inflammatory Character of Alveolar Macrophages from Sarcoidosis Patients

Sarcoidosis is a devastating inflammatory disease affecting many organs, especially the lungs and lymph nodes. Bone marrow-derived mesenchymal stromal cells (MSCs) can “reprogram” various types of macrophages towards an anti-inflammatory phenotype. We wanted to determine whether alveolar macrophages from sarcoidosis subjects behave similarly by mounting an anti-inflammatory response when co-cultured with MSCs. Fifteen sarcoidosis and eight control subjects underwent bronchoscopy and bronchoalveolar lavage (BAL). Unselected BAL cells (70–94% macrophages) were isolated and cultured with and without MSCs from healthy adults. Following stimulation of the cultured cells with lipopolysaccharide, the medium was removed to measure interleukin 10 and tumor necrosis factor alpha (IL-10 and TNF-α). In two additional sarcoidosis subjects, flow cytometry was used to study intracellular cytokines and surface markers associated with alveolar macrophages to confirm the results. Unselected BAL cells from sarcoidosis subjects co-cultured with MSCs showed a reduction in TNF-α (pro-inflammatory M1) and an increase in IL-10 (anti-inflammatory M2) in 9 of 11 samples studied. Control subject samples showed few, if any, differences in cytokine production. Unselected BAL cells from two additional patients analyzed by flow cytometry confirmed a switch towards an anti-inflammatory state (i.e., M1 to M2) after co-culture with MSCs. These results suggest that, similarly to other macrophages, alveolar macrophages also respond to MSC contacts by changing towards an anti-inflammatory phenotype. Based on our results, we hypothesize that mesenchymal stromal cells applied to the airways might alleviate lung inflammation and decrease steroid need in patients with sarcoidosis.

Antibacterial and antibiofilm activity of bone marrow-derived human mesenchymal stem cells secretome against Vibrio cholerae

The ability of V. cholerae to survive and spread in the aquatic environment combined with the scarcity of effective antimicrobial agents, especially those effective against multidrug-resistant strains highlights the need for alternative non-antibiotic approaches for the treatment of V. cholerae infections. The aim of this study was to specifically examine the potential direct effect of unstimulated MSC secretome on V. cholerae killing and biofilm formation as a representative of non-invasive enteric bacterial pathogen. The bmMSCs were characterized by the presence of CD44 and CD73 and the absence of CD45 and CD34 molecular markers. Moreover, self-regeneration and differentiation capacity of MSCs into adipocytes and osteogenic lineages was assessed by immunohistology (IHC) method. The antibacterial activity of unstimulated MSCs supernatant against V. cholerae in broth microdilution assay decreased the bacterial suspension from 10⁸ CFU/ml to 10⁷ CFU/ml and showed a significant antimicrobial activity in a dose-dependent manner at dilutions of 1:8 to 1:128 (P < 0.05). The role of MSC secretome without preconditioning in the prevention of biofilm formation was assessed through plate-crystal violet assay and showed high antibiofilm activity against V. cholerae also in dose-dependent manner. As antibacterial mechanisms of MSC secretome are different from conventional antibiotics, together with its antibiofilm activity, proposes its application as a novel therapeutic approach combatting multi-drug resistant pathogens with no fear of developing antimicrobial resistance.

Autologous cord blood cell infusion in preterm neonates safely reduces respiratory support duration and potentially preterm complications

Preterm birth and its complications are the leading cause of neonatal death. The main underlying pathological mechanisms for preterm complications are disruption of the normal maturation processes within the target tissues, interrupted by premature birth. Cord blood, as a new and convenient source of stem cells, may provide new, promising options for preventing preterm complications. This prospective, nonrandomized placebo controlled study aimed at investigating the effect of autologous cord blood mononuclear cells (ACBMNC) for preventing preterm associated complications. Preterm infants less than 35 weeks gestational age were assigned to receive ACBMNC (5 × 10⁷ cells/kg) intravenous or normal saline within 8 hours after birth. Preterm complication rates were compared between two groups to demonstrate the effect of ACBMNC infusion in reducing preterm complications. Fifteen preterm infants received ACBMNC infusion, and 16 infants were assigned to the control group. There were no significant differences when comparing mortality and preterm complication rates before discharge. However, ACBMNC infusion demonstrated significant decreases in duration of mechanical ventilation (3.2 days vs 6.41 days, P = .028) and oxygen therapy (5.33 days vs 11.31 days, P = .047). ACBMNC infusion was effective in reducing respiratory support duration in very preterm infants. Due to the limited number of patients enrolled, powered randomized controlled trials are needed to better define its efficacy.

Repeated intravenous injection of adipose tissue derived mesenchymal stem cells enhances Th1 immune responses in Leishmania major-infected BALB/c mice

Mesenchymal stem cell (MSCs) therapy are among new strategies that are used to combat infections through immunomodulation. Cell number, route and frequency of injection and the duration of exposure to the infectious agent are of the main factors to determine the effectiveness of cell therapy. The current study was aimed to assess the effect of multiple intravenous (i.v.) injection of adipose tissue derived (AD)-MSCs on immune response of Leishmania (L.) major-infected BALB/c mice. Therefore, infected mice received AD-MSCs four times during the early phase of infection through i.v. route. They were then monitored weekly for footpad swelling and lesion development. Parasite burden, nitric oxide (NO) and cytokine production were measured in the spleen and lymph node 90 days post-infection. Delayed lesion development, significant reduction in footpad swelling and lower parasite burden in the spleen of AD-MSCs-treated mice showed the relative effect of AD-MSCs therapy in the control of L. major dissemination. In addition, MSCs were able to manage direct cytokine responses toward T-helper 1 (Th1). Although the level of interleukin (IL)-10 was still higher than the associated level of tumor necrosis factor (TNF)-α, a shift towards higher level of TNF-α was also observed.

Biological Scaffolds for Abdominal Wall Repair: Future in Clinical Application?

Millions of abdominal wall repair procedures are performed each year for primary and incisional hernias both in the European Union and in the United States with extremely high costs. Synthetic meshes approved for augmenting abdominal wall repair provide adequate mechanical support but have significant drawbacks (seroma formation, adhesion to viscera, stiffness of abdominal wall, and infection). Biologic scaffolds (i.e., derived from naturally occurring materials) represent an alternative to synthetic surgical meshes and are less sensitive to infection. Among biologic scaffolds, extracellular matrix scaffolds promote stem/progenitor cell recruitment in models of tissue remodeling and, in the specific application of abdominal wall repair, have enough mechanical strength to support the repair. However, many concerns remain about the use of these scaffolds in the clinic due to their higher cost of production compared with synthetic meshes, despite having the same recurrence rate. The present review aims to highlight the pros and cons of using biologic scaffolds as surgical devices for abdominal wall repair and present possible improvements to widen their use in clinical practice.

Adipose-Derived Stromal Cells Are Capable of Restoring Bone Regeneration After Post-Traumatic Osteomyelitis and Modulate B-Cell Response

Bone infections are a frequent cause for large bony defects with a reduced healing capacity. In previous findings, we could already show diminished healing capacity after bone infections, despite the absence of the causing agent, Staphylococcus aureus. Moreover, these bony defects showed reduced osteoblastogenesis and increased osteoclastogenesis, meaning elevated bone resorption ongoing with an elevated B‐cell activity. To overcome the negative effects of this postinfectious inflammatory state, we tried to use the regenerative capacity of mesenchymal stem cells derived from adipose tissue (adipose‐derived stem cells [ASCs]) to improve bone regeneration and moreover were curious about immunomodulation of applicated stem cells in this setting. Therefore, we used our established murine animal model and applicated ASCs locally after sufficient debridement of infected bones. Bone regeneration and resorption as well as immunological markers were investigated via histology, immunohistochemistry, Western blot, and fluorescence‐activated cell scanning (FACS) analysis and μ‐computed tomography (CT) analysis. Interestingly, ASCs were able to restore bone healing via elevation of osteoblastogenesis and downregulation of osteoclasts. Surprisingly, stem cells showed an impact on the innate immune system, downregulating B‐cell population. In summary, these data provide a fascinating new and innovative approach, supporting bone healing after bacterial infections and moreover gain insights into the complex ceremony of stem cell interaction in terms of bone infection and regeneration. stem cells translational medicine2019;8:1084–1091

Concise Review: Mesenchymal Stem Cells: From Roots to Boost

It was shown as long as half a century ago that bone marrow is a source of not only hematopoietic stem cells, but also stem cells of mesenchymal tissues. Then the term "mesenchymal stem cells" (MSCs) was coined in the early 1990s, and more than a decade later, the criteria for defining MSCs have been released by the International Society for Cellular Therapy. The easy derivation from a variety of fetal and adult tissues and undemanding cell culture conditions made MSCs an attractive research object. It was followed by the avalanche of reports from preclinical studies on potentially therapeutic properties of MSCs, such as immunomodulation, trophic support and capability for a spontaneous differentiation into connective tissue cells, and differentiation into the majority of cell types upon specific inductive conditions. Although ontogenesis, niche, and heterogeneity of MSCs are still under investigation, there is a rapid boost of attempts at clinical applications of MSCs, especially for a flood of civilization-driven conditions in so quickly aging societies, not only in the developed countries, but also in the populous developing world. The fields of regenerative medicine and oncology are particularly extensively addressed by MSC applications, in part due to the paucity of traditional therapeutic options for these highly demanding and costly conditions. There are currently almost 1,000 clinical trials registered worldwide at ClinicalTrials.gov, and it seems that we are starting to witness the snowball effect with MSCs becoming a powerful global industry; however, the spectacular effects of MSCs in the clinic still need to be shown. Stem Cells 2019;37:855-864.

Recent Advances in Non-Conventional Antimicrobial Approaches for Chronic Wound Biofilms: Have We Found the 'Chink in the Armor'?

Chronic wounds are a major healthcare burden, with huge public health and economic impact. Microbial infections are the single most important cause of chronic, non-healing wounds. Chronic wound infections typically form biofilms, which are notoriously recalcitrant to conventional antibiotics. This prompts the need for alternative or adjunct ‘anti-biofilm’ approaches, notably those that account for the unique chronic wound biofilm microenvironment. In this review, we discuss the recent advances in non-conventional antimicrobial approaches for chronic wound biofilms, looking beyond standard antibiotic therapies. These non-conventional strategies are discussed under three groups. The first group focuses on treatment approaches that directly kill or inhibit microbes in chronic wound biofilms, using mechanisms or delivery strategies distinct from antibiotics. The second group discusses antimicrobial approaches that modify the biological, chemical or biophysical parameters in the chronic wound microenvironment, which in turn enables the disruption and removal of biofilms. Finally, therapeutic approaches that affect both, biofilm bacteria and microenvironment factors, are discussed. Understanding the advantages and limitations of these recent approaches, their stage of development and role in biofilm management, could lead to new treatment paradigms for chronic wound infections. Towards this end, we discuss the possibility that non-conventional antimicrobial therapeutics and targets could expose the ‘chink in the armor’ of chronic wound biofilms, thereby providing much-needed alternative or adjunct strategies for wound infection management.

Bovine fetal mesenchymal stem cells exert antiproliferative effect against mastitis causing pathogen Staphylococcus aureus

Staphylococcus aureus is the most commonly isolated pathogen from clinical bovine mastitis samples and a difficult pathogen to combat. Mesenchymal stem cells (MSC) are multipotent progenitor cells equipped with a variety of factors that inhibit bacterial growth. The aim of the present study was to evaluate the in vitro antibacterial potential against S. aureus of conditioned medium (CM) from MSC derived from fetal bovine bone marrow (BM-MSC) and adipose tissue (AT-MSC). BM-MSC, AT-MSC and fetal fibroblasts (FB) cultures were activated by infection with S. aureus. Bacterial growth was evaluated in presence of CM, concentrated CM (CCM), activated CM (ACM) and concentrated ACM (CACM) from BM-MSC, AT-MSC and FB. Gene expression of β-defensin 4A (bBD-4A), NK-lysine 1 (NK1), cathelicidin 2 (CATHL2), hepcidin (HEP) and indoleamine 2,3 dioxygenase (IDO) and protein expression of bBD-4A were determined in activated and non-activated cells. The majority of BM-MSC and AT-MSC expressed CD73, Oct4 and Nanog, and were negative for CD34. Growth of S. aureus decreased when it was exposed to CM from BM-MSC, AT-MSC and FB. Moreover, growth of S. aureus in CCM, ACM and CACM was lower compared to controls of CM from BM-MSC and AT-MSC. Activated AT-MSC increased mRNA levels of bBD4A and NK1, and protein levels of bBD4A in CM. Thus, CM from fetal bovine BM-MSC and AT-MSC has the capacity to reduce in average ~30% of S. aureus relative growth under in vitro conditions. The in vitro antibacterial effect of fetal bovine MSC may be mediated by bBD4A and NK1 activity.

Mesenchymal stromal cells from infants with simple polydactyly modulate immune responses more efficiently than adult mesenchymal stromal cells

Bone marrow-derived stromal cells or mesenchymal stromal cells (BMSCs or MSCs, as we will call them in this work) are multipotent progenitor cells that can differentiate into osteoblasts, adipocytes and chondrocytes. In addition, MSCs have been shown to modulate the function of a variety of immune cells. Donor age has been shown to affect the regenerative potential, differentiation, proliferation and anti-inflammatory potency of MSCs; however, the impact of donor age on their immunosuppressive activity is unknown. In this study, we evaluated the ability of MSCs derived from very young children and adults on T-cell suppression and cytokine secretion by monocytes/macrophages. MSCs were obtained from extra digits of children between 10 and 21 months and adults between 28 and 64 years of age. We studied cell surface marker expression, doubling time, lineage differentiation potential and immunosuppressive function of the MSCs. Young MSCs double more quickly and differentiate into bone and fat cells more efficiently than those from older donors. They also form more and dense colonies of fibroblasts (colony forming unit-fibroblast [CFU-F]). MSCs from both young and adult subjects suppressed T-cell proliferation in a mitogen-induced assay at 1:3 and 1:30 ratios. At a 1:30 ratio, however, MSCs from adults did not, but MSCs from infants did suppress T-cell proliferation. In the mixed lymphocyte reaction assay, MSCs from infants produced similar levels of suppression at all three MSC/T-cell ratios, but adult MSCs only inhibited T-cell proliferation at a 1:3 ratio. Cytokine analyses of co-cultures of MSCs and macrophages showed that both adult and young MSCs suppress tumor necrosis factor alpha (TNF-α) and induce interleukin-10 (IL-10) production in macrophage co-culture assay in a similar manner. Overall, this work shows that developing MSCs display a higher level of immunosuppression than mature MSCs.

Mesenchymal stromal cells: a novel therapy for the treatment of chronic obstructive pulmonary disease?

COPD is characterised by tissue destruction and inflammation. Given the lack of curative treatments and the progressive nature of the disease, new treatments for COPD are highly relevant. In vitro cell culture and animal studies have demonstrated that mesenchymal stromal cells (MSCs) have the capacity to modify immune responses and to enhance tissue repair. These properties of MSCs provided a rationale to investigate their potential for treatment of a variety of diseases, including COPD. Preclinical models support the hypothesis that MSCs may have clinical efficacy in COPD. However, although clinical trials have demonstrated the safety of MSC treatment, thus far they have not provided evidence for MSC efficacy in the treatment of COPD. In this review, we discuss the rationale for MSC-based cell therapy in COPD, the main findings from in vitro and in vivo preclinical COPD model studies, clinical trials in patients with COPD and directions for further research.