The Antimicrobial Properties of Equine Mesenchymal Stromal Cells as a Biological Alternative to Antibiotics

Presented by: Charlotte Marx

 

Authors: Charlotte Marx, Rebecca M. Harman, Gerlinde R. Van de Walle

Affiliations: Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University 235 Hungerford Hill Road, Ithaca NY 14853

Introduction: Antibiotics are commonly used in veterinary medicine to treat infectious diseases caused by bacteria. However, when microorganisms develop resistance, previously successful drugs are no longer effective, creating a need for alternative approaches to fight bacterial infections. Mesenchymal stromal cells (MSC) are multipotent progenitor cells that can be isolated, expanded in culture, and used therapeutically.

Hypothesis / Objectives: We hypothesize that factors secreted by MSC can be used as an addition to antibiotics based on their ability to (i) directly inhibit bacterial growth and (ii) by altering their secretory pattern after bacterial challenge.

Materials and Methods: We assessed the efficacy of equine MSC secreted factors, delivered in the form of conditioned medium (CM), to inhibit the growth of bacteria by measuring bacterial growth in the presence or absence of CM. To assess whether the MSC CM is more efficient after bacterial challenge, we measured bacterial growth in presence of CM from MSC which were pre-exposed to bacteria.

Results: We found that MSC CM can directly inhibit the growth of various equine wound-related bacteria, including E. coli, P. aeruginosa and A. baumannii (gram-negative), and S. aureus and A. viridans (gram-positive). MSC CM was not only found to inhibit the growth of planktonic bacteria, but even more important, also the formation of biofilms. Interestingly, we found that while CM from “naïve” MSC does not inhibit the growth of S. epidermidis (gram-positive), CM from MSC pre-exposed to these bacteria could inhibit growth, suggesting that MSC respond to bacterial exposure via altering their secretory pattern.

Conclusions: Based on these encouraging results, we propose that equine MSC could be a useful therapy for horse cutaneous wounds, in part due to the direct and indirect anti-microbial properties of MSC secreted factors.

Acknowledgements, Funding, and Conflicts of Interest: There are no conflicts of interests.
This project was supported by:
Agriculture and Food Research Initiative Competitive Grant no. 2018-67015-28309 from the USDA National Institute of Food and Agriculture
The Harry M. Zweig Memorial Fund for Equine Research