Immunoexpression of vascular endothelial growth factor and vWF-regulating angiogenesis in cyclic corpus luteum of Indian buffalo.

The present study was conducted to localize the immunoexpression of VEGF-A (Vascular Endothelial Growth Factor) and von Willebrand factor (vWF) in corpora lutea of healthy buffaloes (24) collected from local slaughterhouses. CL collected were categorized into early (stage I, 1-5 days, n = 6), mid (stage II, 6-11 days, n = 6), late luteal phase (stage III, 12 to 16 days, n = 6) and regressing phase (stage IV, 17 to 20 days, n = 6). The percent positive immunostaining for VEGF-A was significantly (p < 0.05) higher in mid-luteal phase than the other three stages of CL. However, it was higher in early luteal phase as well indicated intense angiogenesis in both early and mid-luteal phases. The number of capillary endothelium expressing vWF was significantly (p < 0.05) highest in mid-luteal phase among all the phases. However, in late luteal phase, the percent area positive for VEGF-A immunostaining was reduced but it was significantly (p < 0.05) higher than corpus albicans phase. Thus, in regressing phase or corpus albicans, it was lowest and reduced considerably. However, in late luteal phase, the number of capillaries with vWF immunoexpression reduced significantly (p < 0.05) but it was lowest in corpus albicans phase. Therefore, the immunotaining pattern for VEGF-A and vWF concluded that there was a spositive linear correlation between the two, that is, as the VEGF-A expression was increased, the number of vWF positive capillaries also increased and vice versa. The VEGF-A expressed by the luteal parenchyma in different stages of development and regression of corpus luteum was thus observed to be involved in promoting the angiogenesis and luteal cell proliferation as supported by vWF expressed by endothelium of proliferating capillaries in buffalo corpus luteum throughout the estrous cycle.