Profiling pro-inflammatory proteases as biomolecular signature of material-induced subcutaneous host response in immuno-competent mice

Abstract

Proteases are important modulators of inflammation, but they remain understudied in material-induced immune response, which is critical to clinical success of biomedical implants. Herein, we comprehensively profile molecular expression and proteolytic activity of three distinct proteases, namely neutrophil elastase, matrix metalloproteinases (MMP), cysteine cathepsins (cathepsin-K and cathepsin-B), in the subcutaneous host response of immuno-competent mice against different biomaterial implants. Quantitative non-invasive monitoring with activatable fluorescent probes reveals that different microparticulate materials induce distinct levels of protease activity with degradable PLGA inducing the strongest signal compared to nondegradable materials such as polystyrene and silica oxide. Furthermore, protein expression of selected proteases, attributable to both their inactive and active forms, notably deviates from their activities associated only with their active forms. Protease activity exhibits positive correlations with protein expression of proinflammatory cytokines TNF-α and IL-6 but negative correlation with pro-fibrotic cytokine TGF-β1. This study also demonstrates the predictive utility of protease activity as a non-invasive, pro-inflammatory parameter for evaluation of the anti-inflammatory effects of model bioactive compounds on material-induced host response. Overall, our findings provide new insights into protease presence in material-induced immune responses, facilitating future biomaterial assessment to evoke appropriate host responses for implant applications.