Equine platelet lysate shows potential as a broad-spectrum antimicrobial that would offer an alternative to traditional antibiotics for the treatment of bacterial infection in horses, according to researchers in the US.
Biological products derived from platelets have been extensively studied as potential therapies because they are a rich source of bioactive elements such as growth factors, which are thought to promote the healing of injured tissues.
Once platelets are collected and concentrated, several techniques can be used to promote the release of the desired agents. These are captured in what is known as a platelet releasate or platelet lysate, which is rich in growth factors and cytokines. This product can be further refined in the lab to remove cellular debris.
University of Georgia researchers Julie Gordon, Sonsiray Álvarez-Narváez and John Peroni noted that, in horses, most platelet-derived products currently used for therapeutic purposes are generated on an as-needed basis from the same patient in which they will be used.
In contrast, the study team established a large-scale process to produce platelet lysate from multiple donor animals. It is made in the laboratory and pooled from a minimum of three donors, then stored until required.
The researchers have already shown that pooled platelet lysate is more effective at suppressing cell-mediated inflammation than that obtained from individual horses, possibly because it contains a more consistent balance of effector proteins.
The researchers, reporting in the journal Frontiers in Veterinary Science, said there is mounting evidence to suggest that, in addition to being well-known regulators of thrombosis and inflammation, platelets also function in the host response to infection.
“Platelets kill bacteria by producing oxygen metabolites such as superoxide, hydrogen peroxide, and hydroxyl free radicals. Moreover, platelets participate in antibody-dependent cell cytotoxicity against microbial pathogens.”
Based on this evidence, the study team set off to explore the potential antimicrobial effects of platelet lysate, given the risks of some bacterial infections to horses and the need for effective substitutes for traditional antibiotics. “In fact, the rapid rise of antibiotic resistance in bacterial pathogens is a paramount global health crisis that has considerable implications for both human and animal health.
“The prolonged and indiscriminate use of traditional antibiotics is one of many factors contributing to the development of resistant bacteria, further increasing the pressure to develop alternative antimicrobial strategies.”
The authors devised a laboratory experiment to define the antimicrobial properties of platelet lysate on four selected strains of bacteria in a laboratory setting: gram-positive Staphylococcus aureus subsp. aureus and Enterococcus faecalis, and the gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa.
Results showed that platelet lysate did not support bacterial growth, and in fact significantly reduced bacterial content compared to normal growth media. All strains tested exhibited a slower growth rate and lower yield in the presence of the platelet lysate.
“The specific effects of platelet lysate were unique for each bacterial strain. In the cases of E. coli and P. aeruginosa, higher amounts of platelet lysate had a greater effect, while this was not true for S. aureus or E. faecalis.”
Furthermore, the onset of exponential growth was delayed for E. coli and P. aeruginosa in the presence of platelet lysate, which has significant clinical implications for developing a dosing schedule.
“In conclusion,” they wrote, “our findings demonstrate the potential value of platelet lysate as a broad-spectrum antimicrobial that would offer an alternative to traditional antibiotics for the treatment of bacterial infection in equine species.”
Their findings, they said, suggest that platelet lysate deserves more detailed analysis to determine its potential as an antimicrobial.
This, together with its known anti-inflammatory effects, could define platelet lysate as a multi-functional treatment, helping to control both inflammation and infection to promote the healing process.
Gordon J, Álvarez-Narváez S and Peroni JF (2021) Antimicrobial Effects of Equine Platelet Lysate. Front. Vet. Sci. 8:703414. doi: 10.3389/fvets.2021.703414