Chapter 10. Methods for evaluating uteroplacental angiogenesis and their application using animal models

Vascular perfusion with fluorescent labeled lectin to study ovarian functions

The aim of this study was to optimize a method to visualize tissue vascularity by perfusing the local vascular bed with a fluorescently labeled lectin, combined with immunofluorescent labeling of selected vascular/tissue markers. Ovaries with the pedicle were obtained from adult non-pregnant ewes. Immediately after collection, the ovarian artery was perfused with phosphate buffered saline (PBS) to remove blood cells, followed by perfusion with PBS containing fluorescently labeled Griffonia (Bandeiraea) simplicifolia (BS1) lectin. Then, half of ovary was fixed in formalin and another half in Carnoy's fixative. BS1 was detected in blood vessels in ovaries fixed in formalin, but not in Carnoy's fixative. Formalin fixed tissue was used for immunofluorescence staining of two markers of tissue function and/or structure, Ki67 and smooth muscle cell actin (SMCA). Ki67 was detected in granulosa and theca cells, luteal and stromal tissue, and a portion of Ki67 staining was co-localized with blood vessels. SMCA was detected in pericytes within the capillary system, in blood vessels in all ovarian compartments, and in the stroma. Thus, blood vessel perfusion with fluorescently labeled lectin combined with immunohistochemistry, microscopy, and imaging techniques provide an excellent tool to study angiogenesis, vascular architecture, and organ structures and function in physiological and pathological conditions.

Role of the pre- and post-natal environment in developmental programming of health and productivity

The concept that developmental insults (for example, poor pre- or postnatal nutrition) can have long-term consequences on health and well-being of the offspring has been termed developmental programming. In livestock, developmental programming affects production traits, including growth, body composition, and reproduction. Although low birth weight was used as a proxy for compromised fetal development in the initial epidemiological studies, based on controlled studies using livestock and other animal models in the last two decades we now know that developmental programming can occur independently of any effects on birth weight. Studies in humans, rodents, and livestock also have confirmed the critical role of the placenta in developmental programming. In addition, the central role of epigenetic regulation in developmental programming has been confirmed. Lastly, relatively simple therapeutic/management strategies designed to 'rescue' placental development and function are being developed to minimize the effects of developmental programming on health and productivity of humans, livestock, and other mammals.

Maternal and fetal microvasculature in sheep placenta at several stages of gestation

Maternal and fetal microvasculature was studied in ewes at days 50, 90 and 130 of gestation using microvascular corrosion casting and scanning electron microscopy. Microvascular corrosion casts of caruncles at day 50 were cup-shaped with a centrally located cavity. Branches of radial arteries entered the caruncle from its base and ramified on the maternal surface of the caruncle. Stem arteries broke into an extensive mesh of capillaries forming crypts on the fetal surface. The architecture of the caruncle at day 90 was similar to what was found at day 50 but the vascularity and the depth of the crypts increased in correspondence to increased branching of fetal villi. The substance of the caruncle was thicker at day 130 compared with day 50, with no remarkable difference compared with day 90. Capillary sinusoids of irregular form and diameter were observed on the fetal surface of the caruncle at all stages. These sinusoids may reduce blood flow resistance and subsequently increase transplacental exchange capacity. A microvascular corrosion cast of the cotyledon was cup-shaped with wide and narrow sides. Cotyledonary vessels entered and left the cotyledon from the narrow side. A cotyledonary artery gave proximal collateral branches immediately after entering the cotyledon and then further branched to supply the remaining portion of the cotyledon. Vessel branches broke into a mesh of capillaries forming the fetal vascular villi. Fetal villi that were nearest to the center of the cotyledon were the longest. Capillaries forming villi were in the form of a web-like mesh, were irregular in size and had sinusoidal dilations. The architecture of the cotyledon at day 90 was similar to day 50, but the vascularity increased. Branching of the fetal villi became more abundant. This extensive branching presumably allows a higher degree of invasion and surface contact to maternal tissues. At day 130, the distal portions of the fetal villi showed low ridges and troughs to increase the surface area for diffusion. Branching of fetal villi appears to influence the elaboration of maternal crypts in all stages of gestation. However, correspondence between crypts and villi is restricted to distal portions of fetal villi.