SCAP-derived conditioned medium demonstrates potent antibacterial activity against E. coli and S. aureus, comparable to gentamicin.

The escalating crisis of antimicrobial resistance necessitates novel therapeutic strategies beyond conventional antibiotics. Bacterial infections, particularly those caused by common pathogens like Staphylococcus aureus and Escherichia coli, pose significant clinical challenges, leading to increased morbidity and mortality. Mesenchymal stem cells (MSCs) have emerged as a promising avenue due to their inherent immunomodulatory and regenerative capacities. Specifically, MSCs secrete a rich array of growth factors and cytokines, which have recently been recognized for potent antibacterial properties, offering a potential antibiotic-sparing approach to combat drug-resistant pathogens.

This in vitro study evaluated the antibacterial properties of stem cells from apical papilla (SCAPs) and their conditioned medium (CM) against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Researchers used colony count (CFU) and disk diffusion assays to assess antibacterial activity. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined through serial dilutions of SCAP-CM and HFF-CM (human foreskin fibroblast conditioned medium) as a control. Gene expression of antibacterial and immunomodulatory factors was analyzed by qRT-PCR in SCAPs and HFFs in response to bacterial exposure.

Both SCAPs and human foreskin fibroblasts (HFFs) exhibited antibacterial activity in CFU and disk diffusion assays, but SCAP-CM demonstrated significantly greater efficacy. The minimum bactericidal concentration (MBC) of SCAP-CM against both E. coli and S. aureus was 2.5 mg/ml. In stark contrast, the MBCs for HFF-CM were 80 mg/ml against E. coli and 320 mg/ml against S. aureus, highlighting SCAP-CM's superior potency. SCAPs showed increased expression of antibacterial and immunomodulatory genes in response to both bacterial strains. Conversely, HFFs displayed reduced IL1β expression and variable changes in IL6 and TNFα depending on the bacterial strain. The study partially attributed the observed antibacterial effect to the secretion of the LL-37 peptide. > These findings confirm that SCAPs exhibit potent antibacterial activity against both Gram-negative and Gram-positive bacteria, mediated by soluble immunoregulatory factors, with inhibitory effects comparable to gentamicin.