Cloning and localization of heparanase in bovine placenta

Heparanase (HPA) degrades heparan sulfate proteoglycan in the extracellular matrix. To understand its role during implantation and placental development in bovine placentae, we cloned and characterized a full-length cDNA encoding bovine HPA and identified HPA localization in placentae. A full-length bovine HPA cDNA was cloned with a 1635 nucleotide open-reading-frame corresponding to a protein of 545 amino acids. The predicted amino acid sequence shares 80.0% and 76.5% identity with human and rat HPA, respectively. In placentomes of 60 and 210 days' gestation, in situ hybridization demonstrated HPA mRNA expression in binucleate cells. Binucleate cells may be a source of HPA throughout gestation in bovine placentae; they may assume specific role(s) in foetal and maternal dialogue. Western blot analysis of bovine placental extracts (day 60) was performed using anti-bovine HPA antibody prepared by immunization of rabbits with synthetic peptide conjugate corresponding to amino acid residues 474-489 of bovine HPA; it showed two immunoreactive proteins with approximate molecular weights of 55 kDa and 65 kDa. Further, immunofluoresence double staining of HPA and placental lactogen (PL) revealed that binucleate cells expressing HPA had immunoreactivity of PL. These results suggest that HPA is specifically expressed in bovine placental binucleate cells and that it may take migratory roles in placentogenesis for degrading the extracellular matrix.