New stem cell treatment for MRSA superbug explored

MADRID, 20 Sep. (EUROPA PRESS) -

Researchers from the Baker Institute for Animal Health, which is part of the Cornell University School of Veterinary Medicine, in the United States, detail in a relevant ex vivo model how the treatment of wounds with the secretion of a type of stem cell called mesenchymal stromal cell (MSC) effectively reduced methicillin-resistant Staphylococcus aureus (MRSA) and stimulated surrounding skin cells to create a defense against the bacterial invader.

The 'S. aureus' has become a major health problem because these bacteria can become a threat in certain circumstances, such as in immunosuppressed patients or in environments with infected wounds, and because they have become resistant to many antibiotics, the only drugs available to treat infections. bacterial infections at the moment.

This study, published in STEM CELLS Translational Medicine (SCTM), however, could help change this situation, as it points to a possible new approach to treat one of the most dangerous strains of the bacteria, MRSA. Although many people carry MRSA without serious consequences, for those whose health is compromised this so-called "superbug" can be deadly.

MSCs are stem cells that can be isolated from bone marrow, adipose tissue, blood, and other tissue sources. "Initially, the use of MSCs for tissue regeneration was advocated based on their ability to differentiate into various tissue types. For this reason, injected MSCs were expected to colonize the site of injury, differentiate into the type of appropriate tissue and regenerate damaged tissue," explains Gerlinde R. Van de Walle, associate professor of microbiology and immunology at Cornell and corresponding author of the study.

"However, studies are revealing that only a small part of the administered MSCs is actually incorporated into the injured tissue," he continues. "For this reason, it is generally accepted that the beneficial effects on tissue repair and regeneration are rather indirect, depending on the paracrine effects of what these cells secrete."

The researcher highlights that "this intriguing finding opens up new therapeutic perspectives based on the development of cell-free regenerative therapies that use the MSC secretome, which includes both soluble factors and factors released in extracellular vesicles. These cell-free therapies could be safe alternatives." and potentially more advantageous by overcoming the risks and obstacles associated with allogeneic use of one's own cells."

Although MSCs have been shown to reduce inflammation in multiple studies, none have yet been conducted investigating the effects of the MSC secretome on skin cell antimicrobial defense mechanisms or testing their efficacy on skin biofilms. a physiologically relevant equine skin model.

Horses were used for the study because, explains Dr Van de Walle, "In both horses and humans, certain types of chronic wounds are often resistant to therapy and cause a variety of complications, resulting in high morbidity and mortality with a significant economic impact".

The team began by establishing an equine skin biofilm model. (Biofilms are "communities" of microorganisms that grow on surfaces. In this state, bacteria are well protected against antibiotics, even if they are not resistant.)

Skin samples were cultured over a period of three days from freshly collected equine skin. No significant increase in cell death or decrease in epidermal thickness was observed during the culture period.

An infected wound model was then created by making uniform wounds on the skin samples and inoculating them with MRSA or its non-antibiotic resistant counterpart, 'S. aureus' sensitive to methicillin (MSSA). Wounds were then treated for 24 hours with antibiotics, DMEM (negative control), or MSC secretome. At the end of the treatment period, the bacterial load was measured by evaluating the colony-forming units (CFU) per gram of tissue.

"The results showed that factors secreted by MSCs significantly decreased SARM viability in our novel skin model," reports Charlotte Marx, first author of the study. "Furthermore, we showed that equine MSC secretions increase SARM activity antimicrobial activity of skin cells by stimulating immune responses from surrounding resident skin cells.

"Taken together," she adds, "these data contribute to our understanding of the antimicrobial properties of the MSC secretome and further support the value of s-based treatments."