Deficient Skeletal Muscle Regeneration after Injury Induced by a Clostridium perfringens Strain Associated with Gas Gangrene

Clostridium perfringens phospholipase C, an archetypal bacterial virulence factor, induces the formation of extracellular traps by human neutrophils

Neutrophil extracellular traps (NETs) are networks of DNA and various microbicidal proteins released to kill invading microorganisms and prevent their dissemination. However, a NETs excess is detrimental to the host and involved in the pathogenesis of various inflammatory and immunothrombotic diseases. Clostridium perfringens is a widely distributed pathogen associated with several animal and human diseases, that produces many exotoxins, including the phospholipase C (CpPLC), the main virulence factor in gas gangrene. During this disease, CpPLC generates the formation of neutrophil/platelet aggregates within the vasculature, favoring an anaerobic environment for C. perfringens growth. This work demonstrates that CpPLC induces NETosis in human neutrophils. Antibodies against CpPLC completely abrogate the NETosis-inducing activity of recombinant CpPLC and C. perfringens secretome. CpPLC induces suicidal NETosis through a mechanism that requires calcium release from inositol trisphosphate receptor (IP3) sensitive stores, activation of protein kinase C (PKC), and the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) pathways, as well as the production of reactive oxygen species (ROS) by the metabolism of arachidonic acid. Proteomic analysis of the C. perfringens secretome identified 40 proteins, including a DNAse and two 5´-nucleotidases homologous to virulence factors that could be relevant in evading NETs. We suggested that in gas gangrene this pathogen benefits from having access to the metabolic resources of the tissue injured by a dysregulated intravascular NETosis and then escapes and spreads to deeper tissues. Understanding the role of NETs in gas gangrene could help develop novel therapeutic strategies to reduce mortality, improve muscle regeneration, and prevent deleterious patient outcomes.

Cannabidiol and Nano-Selenium Increase Microvascularization and Reduce Degenerative Changes in Superficial Breast Muscle in C. perfringens-Infected Chickens

Here, we demonstrated the potential of Cannabis-derived cannabidiol (CBD) and nanosized selenium (nano-Se) for the modulation of microvascularization and muscle fiber lesions in superficial breast muscle in C. perfringens-challenged chickens. The administration of CBD resulted in a decreased number of atrophic fibers (3.13 vs. 1.13/1.5 mm²) compared with the control, whereas nano-Se or both substances resulted in a decreased split fiber number (4.13 vs. 1.55/1.5 mm²) and in a lower number of necrotic myofibers (2.38 vs. 0.69/1.5 mm²) in breast muscle than the positive control. There was a significantly higher number of capillary vessels in chickens in the CBD+Nano-Se group than in the control and positive control groups (1.31 vs. 0.97 and 0.98, respectively). Feeding birds experimental diets lowered the activity of DNA damage repair enzymes, including 3,N4-ethenodeoxycytosine (by 39.6%), 1,N6-ethenodeoxyadenosine (by 37.5%), 8-oxo-guanine (by 36.2%), formamidopyrimidine (fapy)-DNA glycosylase (by 56.2%) and human alkyl adenine DNA glycosylase (by 40.2%) in the ileal mucosa, but it did not compromise the blood mitochondrial oxygen consumption rate (-2.67 OD/min on average). These findings indicate a potential link between gut mucosa condition and histopathological changes in superficial pectoral muscle under induced inflammation and show the ameliorative effect of CBD and nano-Se in this cross-talk due to their protection from mucosal DNA damage.

Regulatory T cells-centered regulatory networks of skeletal muscle inflammation and regeneration

As the understanding of skeletal muscle inflammation is increasingly clarified, the role of Treg cells in the treatment of skeletal muscle diseases has attracted more attention in recent years. A consensus has been reached that the regulation of Treg cells is the key to completing the switch of inflammation and repair of skeletal muscle, whose presence directly determine the repairing quality of the injured skeletal muscle. However, the functioning process of Treg cells remains unreported, thereby making it necessary to summarize the current role of Treg cells in skeletal muscle. In this review, the characteristics, origins, and cellular kinetics of these Treg cells are firstly described; Then, the relationship between Treg cells and muscle satellite cells (MuSCs), conventional T cells (Tconv) is discussed (the former is involved in the entire repair and regeneration process, while the latter matters considerably in causing most skeletal muscle autoimmune diseases); Next, focus is placed on the control of Treg cells on the phenotypic switch of macrophages, which is the key to the switch of inflammation; Finally, factors regulating the functional process of Treg cells are analyzed, and a regulatory network centered on Treg cells is summarized. The present study summarizes the cell-mediated interactions in skeletal muscle repair over the past decade, and elucidates the central role of regulatory T cells in this process, so that other researchers can more quickly and comprehensively understand the development and direction of this very field. It is believed that the hereby proposed viewpoints and problems can provide fresh visions for the latecomers.

The regenerative potential of Pax3/Pax7 on skeletal muscle injury

Background

Skeletal muscle mishaps are the most well-known incidents in society, especially among athletes and the military population. From the various urgency, this accident needs to be cured more quickly. However, the current treatment still has some shortcomings and is less effective. In this case, Paired box 3 and Paired box 7 (Pax3/Pax7) proteins that induce stem cells could potentially be an alternative treatment for skeletal muscle injuries. This paper aimed to analyse the potential treatment of Pax3/Pax7 proteins inducing the stem cell for skeletal muscle injuries.

The main body of the abstract

We did a narrative review by gathering several scientific journals from several leading platforms like PubMed and Scopus. As common accidents, skeletal muscle disease could be due to workplace and non-workplace causes. The highest risk occurs in the athlete and military environment. The treatment of current skeletal muscle injuries is protection, rest, ice, compression, and elevation (PRICE), non-steroidal anti-inflammatory drugs (NSAIDs), and mechanical stimulation. However, it is considered less effective, especially in NSAIDs, inhibiting myogenic cell proliferation. The current finding indicates that the stem cells have markers known as Pax3/Pax7. The role of both markers in muscle injury, Pax3/Pax7, as transcription factors will induce cell division by H3K4 methylation mechanisms and chromatin modifications that stimulate gene activation.

Conclusion

Regulation by Pax3/Pax7 factors that affect stem cells and stem cell proliferation is one of the alternative treatments. This regulation can accelerate the healing of injury victims, especially injuries to the skeletal muscles. Finally, after being compared, Pax3/Pax7 induces stem cells to have the potential to be one of the skeletal muscle injury treatments.

Keywords

Pax3 and Pax7, Pax3/Pax7, Skeletal muscle, Athlete, Stem cells, Cell proliferation, Injuries.

[Study on the interaction between Clostridium perfringens and the host]

Clostridium perfringens type A causes gas gangrene, which is a serious disease caused by wound infection. α-Toxin produced by C. perfringens is known to be the primary pathogenic factor of gas gangrene. Although it has been proposed to induce tissue damage by impairing the host immune system and peripheral circulation, sufficient findings have not been obtained to explain the high virulence of C. perfringens. For the purpose of elucidating the pathogenic mechanism of this bacterium, I focused on the disease progressions such as the bacterial colonization, muscle tissue destruction and repair, and sepsis. In this review, focusing on the action of α-toxin, it will be explained together with the latest research results that the toxin suppresses the activation of the host immune response, represents toxicity to vascular endothelial cells, induces peripheral circulatory disorders due to hematopoietic disorders, inhibits muscle tissue repair, and induces excessive immune response. These mechanisms suggest that α-toxin acts in multiple steps to disrupt host defense and that C. perfringens attacks the host with a highly sophisticated mechanism. It is expected that the onset mechanism of gas gangrene would be elucidated, and I hope that new therapeutic strategies are developed.

The Role of Macrophages During Mammalian Tissue Remodeling and Regeneration Under Infectious and Non-Infectious Conditions

Several infectious pathologies in humans, such as tuberculosis or SARS-CoV-2, are responsible for tissue or lung damage, requiring regeneration. The regenerative capacity of adult mammals is limited to few organs. Critical injuries of non-regenerative organs trigger a repair process that leads to a definitive architectural and functional disruption, while superficial wounds result in scar formation. Tissue lesions in mammals, commonly studied under non-infectious conditions, trigger cell death at the site of the injury, as well as the production of danger signals favouring the massive recruitment of immune cells, particularly macrophages. Macrophages are also of paramount importance in infected injuries, characterized by the presence of pathogenic microorganisms, where they must respond to both infection and tissue damage. In this review, we compare the processes implicated in the tissue repair of non-infected versus infected injuries of two organs, the skeletal muscles and the lungs, focusing on the primary role of macrophages. We discuss also the negative impact of infection on the macrophage responses and the possible routes of investigation for new regenerative therapies to improve the recovery state as seen with COVID-19 patients.

Prolonged field care for traumatic extremity injuries: defining a role for biologically focused technologies

Extremity injuries occur frequently during warfare. While traditionally treated in definitive clinics, the future battlefield is projected to be different in a variety of ways, and there will likely be a shift towards prolonged field care (PFC) for treating extremity traumas. PFC is defined as field medical care that is applied beyond “doctrinal planning time-lines” by a tactical medical practitioner in order to decrease patient mortality and morbidity. At present, there is an urgent need to develop biologically focused technologies for treating extremity injuries in the PFC setting. Herein, the case is made for why rapid advancements in PFC is critical to achieve optimal care for injured Service members in the future, and important design criteria for developing next-generation biologically focused technologies. Finally, a case example—i.e., Gustilo Type III fracture—is presented to illustrate how these biologically focused technologies could be utilized to treat an extremity injury within a PFC environment.

Clostridium perfringens as Foodborne Pathogen in Broiler Production: Pathophysiology and Potential Strategies for Controlling Necrotic Enteritis

Clostridium perfringens (Cp.) is the cause of human foodborne desease. Meat and poultry products are identified as the main source of infection for humans. Cp. can be found in poultry litter, feces, soil, dust, and healthy birds' intestinal contents. Cp. strains are known to secrete over 20 identified toxins and enzymes that could potentially be the principal virulence factors, capable of degrading mucin, affecting enterocytes, and the small intestine epithelium, involved in necrotic enteritis (NE) pathophysiology, also leading to immunological responses, microbiota modification and anatomical changes. Different environmental and dietary factors can determine the colonization of this microorganism. It has been observed that the incidence of Cp-associated to NE in broilers has increased in countries that have stopped using antibiotic growth promoters. Since the banning of such antibiotic growth promoters, several strategies for Cp. control have been proposed, including dietary modifications, probiotics, prebiotics, synbiotics, phytogenics, organic acids, and vaccines. However, there are aspects of the pathology that still need to be clarified to establish better actions to control and prevention. This paper reviews the current knowledge about Cp. as foodborne pathogen, the pathophysiology of NE, and recent findings on potential strategies for its control.

Clostridium perfringens α-toxin inhibits myogenic differentiation of C2C12 myoblasts

Clostridium perfringens type A is the causative agent of clostridial myonecrosis, and α-toxin has been reported to be responsible for the pathogenesis. Recently, it was reported that regeneration of skeletal muscle after C. perfringens-induced muscle disorders is delayed, but the detailed mechanisms have not been elucidated. Here, we tested whether α-toxin impairs the differentiation of C2C12 myoblasts, a useful cell line to study muscle growth, maturation, and regeneration in vitro. α-Toxin dose-dependently inhibited myotube formation in C2C12 cultures after induction of their differentiation by horse serum. Also, immunoblot analysis revealed that α-toxin dose-dependently decreases the expressions of two skeletal muscle differentiation markers, myogenic differentiation 1 (MyoD) and myogenin. These results demonstrate that α-toxin impairs the myogenic differentiation of C2C12 myoblasts. To reveal the mechanism behind α-toxin-mediated impairment of myogenic differentiation, we focused on ceramide production since α-toxin is known to promote the formation of ceramide by its sphingomyelinase activity. Immunofluorescent analysis revealed that ceramide production is accelerated by treatment with α-toxin. Furthermore, a synthetic cell-permeable ceramide analog, C₂-ceramide, inhibited myotube formation in C2C12 cells and decreased the expressions of MyoD and myogenin, suggesting that accelerated ceramide production is involved in the α-toxin-mediated blockage of myogenic differentiation. Together, our results illustrate that the impairment of myogenic differentiation by α-toxin might be crucial for the pathogenesis of C. perfringens to delay regeneration of severely damaged skeletal muscles.

Clostridium perfringens α-toxin specifically induces endothelial cell death by promoting ceramide-mediated apoptosis

Clostridium perfringens type A-induced gas gangrene is characterized by severe myonecrosis, and α-toxin has been revealed to be a major virulence factor involved in the pathogenesis. However, the detailed mechanism is unclear. Here, we show that CD31⁺ endothelial cell counts decrease in muscles infected with C. perfringens in an α-toxin-dependent manner. In vitro experiments revealed that α-toxin preferentially and rapidly induces the death of human umbilical vein endothelial cells (HUVECs) compared with C2C12 murine muscle cells. The toxin induces apoptosis of HUVECs by increasing ceramide. Furthermore, the specificity might be dependent on differences in the sensitivity to ceramide between these cell lines. Together, our results suggest that α-toxin-induced endothelial cell death promotes severe myonecrosis and is involved in the pathogenesis of C. perfringens.