TLR4 and bacterial infectious disease: We also demonstrated a functional association between gram-negative bacterial infections and NHO development via lipopolysaccharide (LPS), a pathogen associated molecular pattern (PAMP), which exacerbated NHO in a Toll-like receptor-4 (TLR4)-dependent manner in mice.<h4>Methods</h4>Using our mouse model of NHO induced by SCI and muscle injury in mice, we tested the effect of a large array of purified PAMPs post-surgery to mimic fungal, viral and bacterial infections and measured NHO bone volumes by micro-computerized tomography (microCT).