Evidence for keratin proteins in normal and abnormal human meibomian fluids

Hyperkeratinization of meibomian glands has been postulated to cause gland dysfunction. Recent investigations on rabbits show that keratin proteins are indeed present in the meibomian fluids of these animals. In this report we present our findings on the presence of these water-insoluble proteins in human meibomian secretions. 6 anti-cytokeratin antibodies, CK8, 18, 19, CK7, CK8, CK14, CK19 and AE1/AE3 were used against the keratin proteins expressed from the human meibomian fluids. Using the immunoblotting (dot blot) technique, abnormal waxy meibomian fluids obtained from subjects diagnosed to have meibomian gland dysfunction (MGD) were compared to normal clear meibomian fluids. The results show that keratins are present in a higher concentration (10%) in the abnormal human meibomian excreta as compared to the normals. Even though the presence of protein markers for keratinization in the abnormal meibomian excreta were not shown, the increased presence of keratin proteins in the abnormal meibomian fluids suggests that, in MGD patients, hyperkeratinization of ductal epithelium may have taken place. More keratin proteins (possibly those of higher molecular weights) were produced in addition to the keratin proteins normally produced by the duct epithelium. The increased amount of keratin proteins in the abnormal meibomian fluids may be explained by the susceptibility of duct epithelium to undergo the process of hyperkeratinization as postulated by other researchers.