Maura Porta, Ph.D.

The main current interest of our lab is the epigenetic memory of pregnancy in the uterine smooth muscles. During pregnancy, hormonal and mechanical stimulations induce profound changes in the uterus. The apoptotic process of involution reverses these changes during the postpartum period. We hypothesize that a trace of these changes, a memory of pregnancy, is preserved in the form of epigenetic variations of the uterine DNA. In particular, we are interested in the myometrium, the smooth muscle component of the uterine wall. Epidemiological studies have shown that parity is associated with increased intensity of postpartum contractions, increased risk for uterine atony, and decreased incidence in dysmenorrhea and leiomyomas. All these effects are suggestive of enduring pregnancy-induced modifications of the myometrial function (without excluding the possibility of epigenetic changes in other components of the reproductive tract, like, for example, the endometrium). The purpose of this project is to investigate how myometrial contractility is modified by parity. Here we adopted a three-tier approach, combining motility experiments, with ELISA, western blot, immunofluorescence, and RT-PCR experiments, and epigenetic studies. The motility study will test the response of the myometrium from virgin/first time pregnant (V/Preg1) and proven breeders/second time pregnant (PB/Preg2) female rats to endogenous and exogenous modulators targeting contractility regulatory pathways. We will conduct these measurements in uterine myometrium of non-pregnant rats, during late pregnancy (day 20 of the rat gestation, E20), pregnancy at term (day 22 of the rat gestation, E22), pregnant in labor (after the birth of the first pup, E22L), and during involution (2 days postpartum, Inv). Preliminary data show that indeed the non-pregnant myometrial tissue from proven breeder rats have a stronger response to oxytocin and a weaker response to terbutaline. Other drugs we plan to test in our motility experiments are PGF2alpha, carbachol, phenylephrine, and nifedipine. We will then investigate the mRNA and protein expression of the receptors of those agents that elicited differential responses in myometrial tissues from V/Preg1 and PB/Preg2. Finally, we will use the results of the DNA methylation analysis to either support or provide additional explanations for the motility and molecular biology data. This research is expected to enhance our understanding of the mechanisms underlying the lasting impact of pregnancy on the myometrial function. This will ultimately lead to advances in healthcare for women before, during, and after pregnancy. In addition, it will provide excellent opportunity for Midwestern university students to be exposed to and develop a passion for biomedical sciences.

A new research project in collaboration with Dr. Isabel Martinez Pena y Valenzuela centers on the hypothesis that Bisphenol A (BPA) enriched diet and high fat diet disrupt uterine function. The quality of the food and the variety of chemicals humans and other animals are exposed to as a consequence of modern commercial and agricultural practices can affect different aspects of health. Our project thus well harmonizes with MWU One Health initiative. Preliminary results show that BPA, a known xenoestrogen commonly found in plastics, epoxy resins, and thermal paper, responds abnormally to oxytocin, which could ultimately cause disruption of pregnancy and preterm labor.

Another area of interest thati is currently suspended but that we might return to in the future, is the study of ryanodine receptors calcium release channels and other sarcoplasmic reticulum channels and their role in cardiac muscle contraction.At the basis of striated muscle contraction there is a phenomenon called excitation-contraction coupling (ECC). A depolarizing stimulus across the plasma membrane of myocytes and muscle fibers induces opening of voltage gated calcium channels (L-type calcium channels, also known as dihydropyridine receptors, DHPR). The ensuing inward calcium current in cardiac myocytes activates ryanodine receptors calcium release channels (RyRs), which allow diffusion of calcium from the sarcoplasmic reticulum (SR) to the cytosol. The combination of calcium entry from the extracellular fluid and from the SR makes it possible for the intracellular calcium levels to rise markedly in a very restricted time frame. This calcium-induced calcium release is quickly terminated, but a definitive mechanism for this event has not yet been fully elucidated. A possible explanation for this behavior can be evinced by investigating an interesting aspect or RyR activity: their ability to work in teams. RyR's are grouped in geometrically organized arrays on the SR membrane and in order to generate a uniform and fast rise in intracellular calcium;they must operate synchronously. We call this phenomenon coupled (or coordinated) gating. It is possible to study this property in artificial planar lipid bilayers, because this complex architecture can be partially retained, under certain circumstances, once the SR is broken apart into the microsomes we use for our reconstitutions.
We are interested in identifying the proteins involved in couple gating. We hypothesized that the immature RyR's arrays of neonatal myocytes lack some of the key proteins required to coordinate channel function. Hence, we propose to verify this hypothesis by comparing adult and neonatal RyR's in bilayers as well as in cells through confocal microscopy and molecular biology assays.

Earlier Projects:
Calcium signaling in the myometrium
Heart development