Immunohistochemical Analyses on Angiogenesis in a Porcine Von Willebrand Disease Model

Objectives: Women with von Willebrand Disease (VWD) type 3 may develop miscarriage during pregnancy. There is evidence that besides its role in coagulation von Willebrand Factor (VWF) is also involved in angiogenesis and defects of this pathway could play a role in miscarriage. For this reason, VWF as well as proteins with known functions in angiogenesis were analysed by immunohistochemistry of several tissues in a pig model comprising all VWD type 3 genotypes (VWD, heterozygous carriers, wildtype).

Methods: Uterus tissue samples including the endometrium were collected from a total of 6 pigs. Of these, two were affected by VWD type 3, two were heterozygous carriers, and the remaining two were wildtype individuals, which served as controls. Hematoxylin-eosin-staining was implemented for morphological evaluation of the tissues, especially with regard to possible differences in structure and pattern of blood vessels. In a second step immunohistochemical analyses comparing the expression of angiogenic factors including VWF were performed in VWD-animals, genetic carriers and wildtype pigs.

Results: Hematoxylin-eosin-staining of histological sections of the porcine uteri comprising the different genotypes revealed differences in the vascular architecture within the lamina propria. Compared to non pregnant wild type pigs where blood vessels in the lamina propria of the endometrium usually are of smaller caliber (mostly categorized as arterioles, venules and capillaries), the lamina propria of VWD type 3 animals contained multiple large arteries and veins (of the type usually found in the uterine wall). The immunohistochemical analysis for VWF showed almost no VWF expression in the pigs affected by VWD. In wildtype and heterozygous pigs, expression was obvious in the endothelium. A narrow band of VWF expression apically on the epithel cells as well as partial expression in glands was seen only in wildtype pigs, but not in heterozygous pigs. For some, but not all further angiogenic factors analysed, expression differences were present among the porcine VWD genotypes.

Conclusion: The results of our study confirm effects of VWF on the uterine vascular architecture and on the expression of specific angiogenic factors. Pigs affected by VWD showed almost no expression of VWF and the blood vessels within the uterine lamina propria had a surprisingly high percentage of large arteries and veins indicating a crucial role of vWF for uterine angiogenesis. Expression differences among the genotypes were obvious for specific angiogenic factors.