LOCALIZATION OF HUMAN PLACENTA LYSYL OXIDASE ON HUMAN PLACENTA, SKIN AND AORTA BY IMMUNOELECTRONMICROSCOPY

Polyclonal antibodies to human placenta lysyl oxidase (Kuivaniemi et al., 1984) were used to localize the enzyme at ultrastructural level in human placenta, skin and aorta, by using the indirect immunogold method. The antibodies were tested on thin sections of tissues fixed and embedded in various experimental conditions. With all methods employed, the immunoreaction was always positive on collagen fibers in all tissues examined, independently of the age of the subjects. In placenta, the reaction was also slightly positive on matrix microfilaments and cells. In dermis, fibroblasts and elastin were scarcely positive in a normalS day-old child, in a child with skin hyperelasticity, and in two babies with osteogenesis imperfecta type II; whereas they were negative in two 16 and 40 year-old normal subjects. In aorta, the immunoreaction was always positive on collagen, scarcely positive on cells and on elastin of a 24 week-old fetus, of a normal child, and of two babies who died of complications associated with O.I. type II; on the contrary, the reaction was negative on cells and elastin fibers of a 16 week-old fetus, and of a normal 19 year-old girl. When present on elastin, gold particles were localized mostly inside the fibers. Contrary to what was observed by Kagan and coworkers on bovine aorta by using antibodies against aortic lysyl oxidase (Kagan et al., 1986), no specific localization of gold particles could be observed on or adjacent to the elastin/associated microfibrils. The results indicate that antibodies raised against placenta lysyl oxidase recognize collagen-associated as well as elastin-associated epitopes. However, the immunoreaction on elastin was scarce in the tissues of young subjects and practically null on adult tissues. This might suggest an age-related expression of the enzyme as far as elastin is concerned, or the presence of slightly different enzyme species for collagen and elastin, or a masking of elastin-associated lysyl oxidase epitopes in adults by other components of the elastin fiber. © 1989, Gustav Fischer Verlag · Stuttgart · New York. All rights reserved.