MRSA (methicillin-resistant Staphylococcus aureus) is a well known superbug, a pathogenic microbe that can cause serious or fatal infections, which are resistant to treatment with standard antibiotics. Researchers have been searching for new ways to treat antibiotic-resistant infections including those caused by MRSA, which killed about 10,000 Americans in 2017. Drug-resistant pathogens continue to cause many fatal infections, and the problem is expected to get worse. Scientists may have found a new way to attack these infections.
Reporting in STEM CELLS Translational Medicine, researchers determined that mesenchymal stromal cells (MSCs) release molecules that can be used to reduce the level of MRSA in wounds, and promote the natural defenses of surrounding skin cells.
MSCs are a type of stem cell found in several tissues including bone marrow, fat, and blood. Scientists hypothesized that MSCs could be used in tissue regeneration because they have the ability to become several different types of cells; they could be injected where an injury occured, and would make new cells to repair the damage, said corresponding study author Gerlinde R. Van de Walle, DVM, PhD, an associate professor of microbiology and immunology at Cornell.
“However, studies are revealing that only a small portion of administered MSCs actually incorporate into injured tissue." Thus, researchers have begun to think that the cells are having an indirect effect, and healing damage through the molecules they secrete, their secretome, added Walle. It may be possible to create cell-free therapies that pose less risk using what we know about the secretome, Walle continued.
In this study, the researchers utilized the MSC secretome to treat a horse model of skin injury. Like humans, horses can develop chronic wounds that may resist therapy and cause complications, "leading to high morbidity and mortality with significant economic impact,” said Walle.
Equine skin samples were collected and grown, then given an infection with MRSA or a Staph that is not antibiotic resistant, methicillin-sensitive S. aureus (MSSA). The models were treated with the MSC secretome, antibiotics, or an inert chemical. The MSC treatment lowered MRSA levels.
“The results showed that secreted factors from the MSCs significantly decreased the viability of MRSA in our novel skin model,” said first study author Charlotte Marx, DVM, PhD. “Moreover, we demonstrated that equine MSC secretions increase the antimicrobial activity of the skin cells by stimulating immune responses of the surrounding resident skin cells."
The study authors suggested that this research could help reduce the use of antibiotics in both humans and animals, which could help stymie the growth and spread of antibiotic resistance.