Immunohistological and biochemical evidence for a role for hyaluronic acid in the growth and development of the placenta.

A monoclonal antibody, designated NDOG1, has been used to stain a series of human and monkey placentae as well as several adult human tissues using immunoperoxidase techniques. In early placentae, NDOG1 was found to stain extracellular material associated with proliferating, extravillous cytotrophoblast cell columns and with the cytotrophoblast shell at the feto-maternal junction. The immunohistology suggests that NDOG1 antigen may be secreted by the anchoring cytotrophoblast into the immediately adjacent maternal tissues. NDOG1 antibody also shows extracellular staining in the stroma of early human placentae and reacted with the apical villous syncytiotrophoblast plasma membrane throughout pregnancy. Biochemical experiments demonstrated that extracts of this latter membrane contained NDOG1 antigenic activity which was susceptible to digestion with bovine testicular hyaluronidase. Hyaluronic acid was the only glycosaminoglycan found in this membrane, thereby implying a reaction between NDOG1 antibody and hyaluronic acid. Whilst no such direct interaction could be demonstrated in vitro, NDOG1 was shown to compete with two other antibodies which themselves demonstrated specificity for hyaluronic acid. The proposed identity between the NDOG1 antigen and hyaluronic acid is discussed particularly in terms of placentation where the distribution of NDOG1 staining may confirm the role of hyaluronic acid in providing an open matrix structure during stages of cell proliferation, migration and invasion.