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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. [ABSTRACT FROM AUTHOR]

Tumour necrosis factor‐α (TNF‐α) is a cytokine that plays multiple important roles in corpus luteum (CL). Immunolocalization of expression of TNF‐α in CL of buffalo was studied in different stages of its development and regression. Corpus luteum of healthy buffaloes (24) was collected from local slaughterhouses and categorized into early (stage I, 1–5 days, n = 6), mid (stage II, 6–11 days, n = 6), late luteal (stage III, 12–16 days, n = 6) and regressing phase (stage IV, 17–20 days, n = 6). In earliest phase of cyclic CL, per cent immunoexpression of TNF‐α was significantly (p <.05) lower as compared to all phases with its expression being restricted to few developing luteal cells, usually in neutrophils. A significantly (p <.05) higher number of neutrophils with TNF‐α immunoexpression were observed as compared to mid‐luteal phase that indicated its role in initiation of angiogenesis at this stage. TNF‐α immunoexpression almost doubled in mid‐luteal phase, but the number of neutrophils exhibiting TNF‐α was significantly (p <.05) lower with respect to all phases of CL. Immunoexpression percentage in late luteal phase increased sharply being significantly (p <.05) higher than earlier two phases of CL. In regressing phase, per cent immunostaining was maximum with highly significant (p <.05) difference as compared to all other stages, observed in all degrading luteal cells, abundant immune cells, that is neutrophils and macrophages which finally led to apoptosis and phagocytosis. Immunoexpression of TNF‐α in early luteal phases served its role in initiation of angiogenesis, and its intense expression in regressing phase of CL suggested a shift in its role to apoptosis and structural luteal regression signifying both luteotropic and luteolytic roles in buffalo. This is probably the first study of its kind in buffaloes. [ABSTRACT FROM AUTHOR]