Apoptosis and Remodeling in Ovary of Water Deer and Sika Deer at Pregnant and Non-pregnant Stages

Background: Many studies have been conducted on the sika deer, an extinct species in Korea, to analyze the physiological characteristics of restoration and reproductive physiological characteristics. The reproductive physiological mechanisms of water deer and sika deer, especially the function, morphological changes, and ovarian characteristics, are unknown. Objective: We aimed to study the differences in the reproductive physiology of water deer and sika deer and determine the difference in function through ovarian morphological analysis and cell remodeling. Methods: Water deer and sika deer ovaries were collected during the estrus and pregnancy seasons from the Korean Peninsula and Russia–Korean Peninsula border, respectively, and analyzed. Morphological analysis and in situ zymography were conducted to confirm the activity of matrix metalloproteinases (MMPs), analyze the immunofluorescence of Casp-3 protein, and assess the morphological changes in the ovaries. Results: The results of the analysis confirmed the ovaries of water deer and sika deer to be morphologically different. The corpus luteum of sika deer showed large differences in size and morphology compared to water deer, and many changes were also observed in the corpus luteum cells. However, the activity of MMPs and apoptosis in the follicles of sika deer were higher than those of water deer. Water deer and sika deer showed similar corpus luteum patterns during estrus and pregnancy. Conclusion: In our study, morphological differences were found to be present between water deer and sika deer ovaries; however, cell remodeling demonstrated a similar pattern. Therefore, the endocrine function and reproductive efficiency for reproduction would be similar.