Mesenchymal Stromal/Stem Cell and Minocycline-Loaded Hydrogels Inhibit the Growth of Staphylococcus aureus that Evades Immunomodulation of Blood-Derived Leukocytes.

Mesenchymal stromal/stem cells (MSCs) have demonstrated favorable wound healing properties in addition to their differentiation capacity. MSCs encapsulated in biomaterials such as gelatin and polyethylene glycol (PEG) composite hydrogels have displayed an immunophenotype change that leads to the release of cytokines and growth factors to accelerate wound healing. However, therapeutic potential of implanted MSC-loaded hydrogels may be limited by non-specific protein adsorption that facilitates adhesion of bacterial pathogens such as planktonic Staphylococcus aureus (SA) to the surface with subsequent biofilm formation resistant to immune cell recognition and antibiotic activity. In this study, we demonstrate that blood-derived primary leukocytes and bone marrow-derived MSCs cannot inhibit colony-forming abilities of planktonic or biofilm-associated SA. However, we show that hydrogels loaded with MSCs and minocycline significantly inhibit colony-forming abilities of planktonic SA while maintaining MSC viability and multipotency. Our results suggest that minocycline and MSC-loaded hydrogels may decrease the bioburden of SA at implant sites in wounds, and may improve the wound healing capabilities of MSC-loaded hydrogels.