Persistent Müllerian duct syndrome (PMDS) in the Polish free-ranged bull populations of the European bison (Bison bonasus L.)

• Vestigial uteri were identified in the bulls of the European bison.
• Morphological structure of the vestigial male uterus varied in each bull.
• Uterine protein profiles were similar in all males and the control female.
• Uterine estrogen concentration was similar in the males and the control female.
• Various mutations of the AMH and AMHR2 genes were identified in the bulls.

This study describes the diversity of vestigial male uteri of the European bison (Eb) examined for: (1) morphology, (2) glycoprotein localization, (3) total protein and glycoprotein profiles, (4) steroid concentrations, and (5) PMDS based on the mutation of AMH and AMHR2 genes. Uteri of adult bulls (5–12 years old) were compared to a uterus of a juvenile female (6 months old). Male uterine proteins were analyzed in parallel to secretory endometrial proteins of pseudo-pregnant pig (PsEND) and BSA used as profile-controls. Hematoxylin/eosin-staining revealed the diversity of male uterine morphology, including lumen size/shape, endometrial (END) gland density, luminal knob-like epithelial structures and multiple intrauterine cells proliferating within the lumen. PAS-staining revealed the presence of glycoproteins restricted to luminal epithelial cells and END glands. Heterologous total protein PAGE-profiles (20–66 kDa) revealed two dominant fractions (66 and 45 kDa), similar to PAS-profiles (67 and 47 kDa) in male and female uterine tissues. In male uterine tissues, androstendione and progesterone, but not testosterone, estrone or estradiol concentrations were lower than in the female. Sequencing of AMH- and AMHR2-like amplicons allowed identification of these gene mutations in Eb. Our results provide novel data regarding PMDS, demonstrating the diversity of uterine morphology, glycoprotein mass/profile, steroid concentration and AMH/AMHR2 mutations in Eb bulls.