Alpha smooth muscle actin in the cycling ovary - an immunohistochemical study

In the ovary with its cyclically developing and regressing functional bodies and the associated intense neovascularisation and remodelling, alpha-smooth muscle actin (SMA) immunolocalisation has been frequently used as a marker to establish vessel hierarchy, in angiogenesis studies, or in studies characterising ovarian neoplasms in various species. The present study aims at detection of alpha-SMA-immunolocalisation within all structural components of the cycling bovine ovary in order to complement the hitherto available data. 27 ovaries, mainly of dairy cows ranging from 23 to 118 months of age and displaying all major stages of follicle and corpora lutea development, were collected at the abattoir and subjected to routine HE and trichrome staining as well as alpha-SMA immunohistochemistry. For this purpose, the specimens were pooled to form groups of the respective stage of corpus luteum development. The ovarian stroma displayed a notable alpha-SMA-reactivity, particularly surrounding the functional bodies. The study revealed specialised vascular modifications such as multi-directionally arranged vascular smooth muscle layers, vascular sphincters and distinct epitheloid modifications of the media in ovarian arteries. Alpha-SMA-reactivity of the microcirculation within corpora lutea of various stages allowed inferences on respective angiogenic properties. The findings were discussed focussing on functional interpretations.