Systematic Review of Histopathological Bottlenose Dolphin (Tursiops truncates) Placental Alterations Correlated to Healthy Neonates and Perinatal Mortality Events

In mammals, placentation is associated with several steps of vascular adaptations throughout pregnancy. These vascular changes occur both on the maternal and fetal sides, consisting of maternal uterine spiral arteries remodeling and placental vasculogenesis and angiogenesis, respectively. Placental angiogenesis is a pivotal process for efficient fetomaternal exchanges and placental development. This process is finely controlled throughout pregnancy, and it involves ubiquitous and pregnancy-specific angiogenic factors. We describe placentae from 12 bottlenose dolphin (Tursiops truncates) mothers, of which 8 were from females with uncomplicated pregnancies, and the remaining (4) were associated with various maternal and fetal disorders. Only in two cases, perinatal mortality occurred. The purpose of this study was to describe the various microscopic findings in the placentae, and to correlate them with various clinical abnormalities. Formalin-fixed, paraffin-embedded tissue sections were used which were stained with hematoxylin and eosin, and by IHC. This study found a significantly increased prevalence of calcifications, syncytial knots, infarcts and fibrinoid necrosis in cases of probable Pregnancy Induced Hypertension (PIH), as compared to cases of Normal Gestation (NG). Also, the prevalence of sclerotic villi, syncytial knots and chorangiosis suggest some possible cases of Gestational Diabetes Mellitus (GDM) than in cases of NG. In addition, the prevalence of sclerotic villi, syncytial knots, infarcts and fibrinoid necrosis was significantly more in cases of maternal mild or moderate anemia (MA) than in cases of NG. Overall, the study showed several significant microscopic findings in placentae from mothers and/or foetuses affected by various pathological processes. IHC revealed constant absence of Toxoplasma gondii infection, and different levels and patterns of expression of endocrine gland derived vascular endothelial growth factor (EG-VEGF) or prokineticin 1 (PROK1). PROK1 has emerged as specific placental angiogenic factor that controls many aspects of normal and pathological placental angiogenesis. Upon the histopathological lesions documented, we suspected that in dolphin MA, PIH, and probably GDM may be present and understimated problems. Placental examination, particularly by an accurate histological exam, provides information of the type and severity of the condition complicating the pregnancy.