Antimicrobial activity of canine adipose tissue-derived Mesenchymal Stromal Cells lyosecretome
Mesenchymal Stromal Cells (MSCs) are widely studied in regenerative medicine because of their unique biological properties. The MSC-derived secretome is a cell-free product containing soluble factors and extracellular vesicles that mediate many of the biological properties of MSCs, including immunomodulatory and antimicrobial activities. This study aimed to evaluate the antimicrobial activity of a freeze-dried secretome derived from canine adipose tissue MSCs (canine lyosecretome, c-Lyo) against pathogens relevant to canine infections. The antimicrobial activity of c-Lyo was assessed using minimal inhibitory concentration (MIC) assays against six bacterial species (Escherichia coli, Salmonella enterica subsp. enterica serovar Typhimurium, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus pseudintermedius and Pseudomonas aeruginosa) and one yeast (Malassezia pachydermatis). Potential interactions between c-Lyo and commonly used veterinary antimicrobials (gentamicin, amoxicillin, enrofloxacin, and ketoconazole) were evaluated using checkerboard assays (CkA). Proteomic characterization of the c-Lyo and transcriptomic analysis of canine MSCs were also conducted to explore molecular mechanisms underlying antimicrobial activity. The results demonstrated that c-Lyo exerts antimicrobial activity against all tested microorganisms, with variable sensitivity among species. CkA exhibited predominantly additive interactions with conventional antimicrobials and occasional synergistic effects, with no evidence of antagonism. Proteomic and transcriptomic analyses supported the presence of antimicrobial peptides and immune-related pathways that potentially contribute to both direct antimicrobial activity and the modulation of host defense mechanisms. These findings indicate that c-Lyo may represent a promising cell-free biologic approach for antimicrobial strategies in veterinary medicine. Overall design: RNA-seq profiles of primary adipose-derived canine mesenchymal stromal Cells