November 16, 2021

What is the molecular basis for parturition

Birth. Aging. Death. Three points in the life cycle. But before Aging and Death there is Reproduction allowing life to go on in a never-ending cycle.  Babies are born, the grow up, have children, age and then die. Life goes on through children, generation after generation. Individual cells also age and die. But before they die, they are able to divide, grow and proliferate. This process goes on in individuals at the beginning of life and continue until the death. Thus, birth and death are intertwined. Scientists studying parturition (birth) point out that aging of an individual starts in utero and they believe that the aging process in the fetal membranes contributes to the initiation of the complex biochemical cascades that end in birth of offspring.  The cells of the fetal membranes age and at some point, die. Science has learned a great deal about parturition by studying the complicated process in animals. We know many things about the human complex pathways leading to birth,  including the role of reproductive hormones and the complex and redundant cascades that trigger the functional progesterone withdrawal prior to the onset of labor and the molecular events that transition the myometrium from a relaxed quiescent state to coordinated uterine contractions that dilate a soft cervix enabling the fetus to be born. We understand the complexities of the changes in the cervical tissue a tissue consisting of some cells but predominately collagen and other extracellular components enabling the cervix to dilate. There is increased understanding that there is role for what is called a sterile inflammation – the release of cells and chemicals such as cytokines,  prostaglandins and other molecules that work to remodel the uterine tissues. There is also an understanding of how the fetus contributes to its own birth through the fetal adrenal axis. Now scientists are beginning to appreciate how the senescence of the fetal membranes sets the stage. This senescence comes about by a programmed clock that ensures that parturition is initiated in each mammalian species at the time when the fetus is developmentally mature. Programmed aging of the fetal membranes leading to the death of cells releases compounds that initiate and orchestrate the many signals for parturition across different uterine compartments of myometrium, decidua, cervix to initiate the birth process. Reproductive science now understands that term birth and preterm birth are triggered by different initiation cascades. We need to understand how this leads to the final pathways that are critical for preterm and term birth. We know much but we need to know more, most of all we need to know how the various pathways are integrated. For this reason, The Campion Fund and The Reproductive and Developmental Biology Laboratory of the National Institute of Environmental Health Sciences are hosting a meeting on the Science of Parturition in February, 2023.  The Campion Fund blogs will highlight some of the recent studies on this topic throughout the coming year.

Phyllis Leppert