Comparative study of compact bone tissue microstructure between non-transgenic and transgenic rabbits with WAP-hFVIII...

The aim of this study was to investigate differences in compact bone tissue microstructure between New Zealand White transgenic rabbits with human blood clotting factor VIII gene and the non-transgenic ones. The transgene was under the transcriptional control of the whey acidic protein (WAP) promoter. Altogether, 42 femora were analysed. Specimens were prepared using standard histological equipment, producing thin sections approximately 80-100 microm. Areas, perimeters, minimum and maximum diameters of vascular canals of primary osteons, Haversian canals and secondary osteons were measured. Our results indicate the basic structural pattern of the bone tissue was primary vascular longitudinal in both groups of rabbits. However, a fibrolamellar bone tissue was identified only in the transgenic rabbits. The measured variables of the vascular canals of the primary osteons, the Haversian canals and the secondary osteons were higher in transgenic rabbits in comparison with non-transgenic ones in most cases and the differences were often statistically significant (P < 0.01; P < 0.001). More significant differences were noticed in males (transgenic versus non-transgenic). However, it is not easy to find the real cause of the changes. Despite the fact that no hFVIII mRNA expression was found in the analysed bone of transgenic rabbits, we presume that the observed differences could be associated with transgenesis. In this article, we discuss possible associations between transgene integration as well as aneuploidy and/or observed microstructural changes in compact bone tissue.