Common mechanisms of physiological and pathological rupture events in biology: novel insights into mammalian ovulation and beyond

Ovulation is a cyclical biological rupture event fundamental to fertilisation and endocrine function. During this process, the somatic support cells that surround the germ cell undergo a remodelling process that culminates in breakdown of the follicle wall and release of a mature egg. Ovulation is driven by known proteolytic and inflammatory pathways as well as structural alterations to the follicle vasculature and the fluid-filled antral cavity. Ovulation is one of several types of systematic remodelling that occur in the human body that can be described as rupture. Although ovulation is a physiological form of rupture, other types of rupture occur in the human body which can be pathological, physiological, or both. In this review, we use intracranial aneurysms and chorioamniotic membrane rupture as examples of rupture events that are pathological or both pathological and physiological, respectively, and compare these to the rupture process central to ovulation. Specifically, we compared existing transcriptomic profiles, immune cell functions, vascular modifications, and biomechanical forces to identify common processes that are conserved between rupture events. In our transcriptomic analysis, we found 12 differentially expressed genes in common among two different ovulation data sets and one intracranial aneurysm data set. We also found three genes that were differentially expressed in common for both ovulation data sets and one chorioamniotic membrane rupture data set. Combining analysis of all three data sets identified two genes (Angptl4 and Pfkfb4) that were upregulated across rupture systems. Some of the identified genes, such as Rgs2, Adam8, and Lox, have been characterised in multiple rupture contexts, including ovulation. Others, such as Glul, Baz1a, and Ddx3x, have not yet been characterised in the context of ovulation and warrant further investigation as potential novel regulators. We also identified overlapping functions of mast cells, macrophages, and T cells in the process of rupture. Each of these rupture systems share local vasoconstriction around the rupture site, smooth muscle contractions away from the site of rupture, and fluid shear forces that initially increase and then decrease to predispose one specific region to rupture. Experimental techniques developed to study these structural and biomechanical changes that underlie rupture, such as patient-derived microfluidic models and spatiotemporal transcriptomic analyses, have not yet been comprehensively translated to the study of ovulation. Review of the existing knowledge, transcriptomic data, and experimental techniques from studies of rupture in other biological systems yields a better understanding of the physiology of ovulation and identifies avenues for novel studies of ovulation with techniques and targets from the study of vascular biology and parturition.

Automated summary

Ovulation is a fundamental biological event that involves the rupture of follicle wall and release of mature egg. This process is driven by proteolytic and inflammatory pathways, as well as structural alterations to the vasculature and cavity of the follicle. Comparisons with other rupture events, such as intracranial aneurysms and chorioamniotic membrane rupture, reveal common processes and differentially expressed genes. Understanding the physiology of ovulation through analysis of transcriptomic data and experimental techniques from studies of rupture in other biological systems can provide insights for future studies and novel targets in the field of reproductive biology.