Infected wound healing could be helped by factors secreted by mesenchymal stromal cells.
Mention “bacteria” and we tend to think of the individual microorganisms that we see growing in laboratory cultures (the so-called “planktonic” forms.) However, in nature, it is more common for bacteria to form biofilms – communities of different microbes that become embedded in a slimy extracellular matrix. Biofilms protect the microbes from both antibacterial substances and the immune response of the host.
Biofilms contribute to chronic inflammation and delayed healing of wounds, and are not readily detectable using current routine diagnostic methods. However, biofilm infections should be suspected in equine limb wounds that are not healing as expected. Treatment is based on repeated debridement and application of topical antimicrobial therapy.
Mesenchymal stromal cells (MSCs) are cells, isolated from different sites, that can differentiate into other types of cells. They take part in the inflammatory, proliferative, and remodelling phases of tissue repair.
Previous work has shown that secretions from MSCs promote wound repair by stimulating fibroblast migration in the skin and promoting the development of new blood vessels. They also have antibacterial properties.
A recent study looked at the effect of mesenchymal stromal cells on biofilms.
Research by Charlotte Marx and colleagues at the Cornell University College of Veterinary Medicine looked at the effect of mesenchymal stromal cells on biofilms, using an equine skin explant model.
They found that secreted factors from equine MSC (collectively referred to as the MSC secretome) significantly decreased the viability of methicillin-resistant Staphylococcus aureus (MRSA) in mature biofilms.
The researchers also showed that equine MSCs secrete the cytokine CCL2 that boosts the antimicrobial activity of equine keratinocytes by stimulating the production of cathelicidin and ß-defensin.
Reporting their work in the journal Tissue Engineering and Regenerative Medicine, they concluded: “Collectively, these data contribute to our understanding of the MSC secretome’s anti-microbial properties, both directly by killing bacteria and indirectly by stimulating immune responses of surrounding resident skin cells, thus further supporting the value of MSC secretome-based treatments for infected wounds.”
Charlotte Marx, Sophia Gardner, Rebecca M. Harman, Bettina Wagner, Gerlinde R. Van de Walle. Mesenchymal stromal cell-secreted CCL2 promotes antibacterial defense mechanisms through increased antimicrobial peptide expression in keratinocytes. Tissue Engineering and Regenerative Medicine (2021) Vol 10 (12) pp1666-1679