MMP1 and keratoconus: Several molecular and proteomics studies (193–196) have also demonstrated the upregulation of certain tear proteins and inflammatory molecules in keratoconus, including interleukin-6, TNF-alpha, matrix metalloproteinases (MMP)-1,−3,−7,−9, and−13, lipocalin-1, neutrophil-defensin 1 precursor, mammaglobulin-B precursor, and keratin types 1 and 2, suggesting that inflammation plays a role in the pathogenesis of keratoconus.