Neovascularization of the corpus luteum of rats during the estrus cycle

Publisher Website
Google Scholar
Abstract
In order to elucidate the chronological morphological changes of the corpus luteum (CL) of rats, as a physiological angio‐genesis model, the CL of rat ovaries was studied light microscopically using periodic acid methenamine silver staining (PAM) and immunostaining for type IV collagen, laminin, thrombomodulin (TM), factor VIII related antigen (factor VIII) and α‐smooth muscle actin (α‐SMA). The CL was also studied electron microscopically. Female Wistar‐lmamichi rats were used, which have a regular 4‐day estrous cycle. The histological changes of the CL were observed in 6‐hour intervals from 4h before the ovulation to 28h post‐ovulation during the estrous cycle. Once the basement membrane (BM) of the follicle disintegrated following ovulation, developing capillaries entered into the CL and formed a vascular lumen with a surrounding BM, which showed positive for PAM staining, type IV collagen and laminin. The developing capillaries in the CL showed a weakly positive reaction for TM and factor VIII, but were negative for α‐SMA. However, the appearance of immature pericytes around the well‐developed capillary was obvious with electron microscopy. The study reported here provides detailed descriptions of anglogenesis during luteinization. It is concluded that the angiogenesis of the CL begins at the time of destruction of the BM of the ovarian follicle, and that the capillary BM appears when the capillary forms its lumen. Moreover, it was demonstrated that the capillary does not develop into an arteriole during luteinization.