DETECTION OF ELASTIN IN THE HUMAN FETAL MEMBRANES - PROPOSED MOLECULAR-BASIS FOR ELASTICITY

The human fetal membranes provide a sterile biomechanical container wh ich adjust by growth to mid-pregnancy to the increase in fetal size, a nd by elasticity to the forceful movements of the fetus. The molecular basis for this elasticity is not known, yet reduced elasticity may le ad to their premature rupture and preterm birth, a major problem in pe rinatal medicine. Classically, elastin confers the property of elastic recoil to elastic fibres which are assembled from a family of tropoel astin precursors. These are covalently cross-linked to form insoluble elastin by formation of desmosine and isodesmosine, catalysed by the e nzyme lysyl oxidase. The amnion, chorion and decidua were shown by Nor thern analysis and RT-PCR to contain detectable levels of tropoelastin mRNA and the mRNA encoding lysyl oxidase. The proteins encoded by the se mRNAs were also identified by Western blotting and immunolocalizati on. Further, insoluble elastin was extracted from the human fetal memb ranes and shown by comparison to elastin preparations from other elast ic tissues to have a reasonable desmosine content. Finally, scanning e lectron microscopy confirmed the presence of multiple layers of an app arently very thin elastic system in this tissue. This biochemical and histopathologic study has demonstrated therefore that the human fetal membranes synthesize and deposit a novel elastic fibre. The presence o f such an elastic system in these tissues provides, for the first time , a probable molecular basis for the elastic properties of this tissue . (C) 1997 W. B. Saunders Company Ltd.