MMP9 and osteomyelitis: In osteomyelitis, infections can increase the activity of MMP9 and the release of various pro-inflammatory factors such as IL1β, which in turn worsens the degree of inflammation and promotes the progression of osteomyelitis.[39] Studies have shown that MMP9 is highly expressed in neutrophils of DFU, particularly in intravascular and peripheral tissues at the skin lesions of DFU.