Temporal Variations in Density and Distribution of Neutrophils with Associated Morphological Changes in Uterus at All Stages of Estrus Cycle in Mice

Uterus is an important reproductive organ that undergoes proliferative, degenerative, repair and regenerative changes in its histological tunics during different stages of estrous cycle. These changes are temporal and are tightly regulated by the ovarian hormones. Derangements in remodeling is the reason for pathological conditions such as endometritis, endometriosis etc., The objective of the present study is to report on the % relative endometrial surface area, neutrophil density and their distribution in uterus at all stages of estrus cycle in normal mice to help understand the pathologies in unterine remodeling by abnormal neutrophil recruitment. All these temporo-spatial events are detected using Histomorphological, micro-morphometrical and immunohistochemical techniques. Our studies revealed that histomorphological variations were more pronounced in endometrium than other tunics. Histomorphometric studies found that the % relative endometrial surface area was maximum during late proestrus and early estrus. It reduced to its minimum levels in the middle of metestrus and was immediately restored within 6hrs. Histological and immunohistochemical studies confirmed that neutrophils were present during all stages of the estrus cycle. Their influx and density was maximum at early metestrus and was minimum at late metestrus. Their density were moderate and static thereafter until early proestrus. These findings suggested that the rate of infiltration of neutrophils in to uterus is a controlled and stage specific process. Their complex role of inflammation, phagocytosis and endometrial repair in remodeling the uterus may be dependent on the uterine microenvironment at a given time point.