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Treating the Placenta with a Nanoparticle-Encapsulated Mitochondrial Antioxidant Improves Placental Function and Fetal Cardiomyocyte Development in a Rat Model of Prenatal Hypoxia
- Author / Creator
- Ganguly, Esha
Introduction: Pregnancy complications associated with prenatal hypoxia have been linked to the development of cardiovascular disease in adult offspring. Prenatal hypoxia (due to maternal or placental hypoxia) has been shown to increase placental oxidative stress and impair placental function in a sex-specific manner, thereby affecting fetal development. Studies suggest that prenatal hypoxia can reduce mitochondrial respiratory capacity, which in turn, could lead to placental dysfunction and impaired fetal organ development. Recently, we, together with our collaborators, have demonstrated that prenatal hypoxia-induced placental oxidative stress can impair development of key fetal organ system (such as the brain) through the release of placenta-derived factors into the fetal circulation. However, the effects of placenta-derived factors on fetal cardiomyocyte development are yet to be determined. Given that oxidative stress is central to placental dysfunction and altered fetal organ development, placental function may be improved by the use of an antioxidant. However, drug use in pregnancy is restricted due to potential adverse effects on the fetus should transplacental passage occur. Thus, the main objective of my PhD studies was to improve placental function without direct drug exposure to the fetus in order to avoid off-target effects during development. I assessed a placenta-targeted innovative treatment strategy using a mitochondrial-targeted antioxidant (MitoQ) encapsulated into biodegradable nanoparticles (nMitoQ) as a delivery system, which diffuses into the placental syncytium to release the antioxidant treatment within the placenta without crossing the placental basal membrane to reach the fetus. I tested whether this placenta-targeted nMitoQ treatment targeted in hypoxic dams improved placental oxidative stress and placental morphology and function. In addition, I assessed whether nMitoQ treatment in hypoxic dams prevents fetal programming of cardiac diseases via the release of placenta-derived factors.
Methods: Pregnant Sprague-Dawley rats were intravenously injected with saline or nMitoQ (100µl of 125 μM) on gestational day (GD) 15 and exposed to either normoxia (21% O2) or hypoxia (11% O2) from GD15-21. On GD21, placentae from both sexes were collected for detection of oxygenation, superoxide, nitrotyrosine, nitric oxide, CD31 (endothelial cell marker), and maternal and fetal blood spaces, Vegfa and Igf2 expression in the placental labyrinth zone. In a second set of experiments, on GD21, male and female placental labyrinth zones were collected for mitochondrial functional assessments. To assess the effects of placenta-derived factors on fetal cardiomyocyte development in vitro, on GD21, male and female placentae were harvested, placed in culture, and conditioned media (containing placental-derived factors) was collected after 24h. Male and female cardiomyocytes from control dam fetuses were incubated with same sex placental conditioned media.
Results: nMitoQ treatment reduced the prenatal hypoxia-induced increase in placental superoxide levels in both male and female placentae but improved oxygenation in only female placentae. Without altering nitric oxide levels, nMitoQ treatment reduced nitrotyrosine levels in hypoxic female placentae. Prenatal hypoxia reduced placental Vegfa and Igf2 expression along with reduced maternal and fetal blood spaces and fetal capillaries area in the labyrinth zone from both sexes, while nMitoQ increased Vegfa and Igf2 expression only in hypoxic female placentae. Prenatal hypoxia reduced mitochondrial complex IV activity in male placentae, which was improved by nMitoQ treatment. Interestingly, in females, nMitoQ had no effect on placental mitochondrial function, but prenatal hypoxia increased contribution of the N-pathway (through complex I) and decreased contribution of the S-pathway (through complex II). nMitoQ treatment led to increased oxygenation in hearts and livers of hypoxic female fetuses, whereas oxygenation was improved in hearts but not livers of nMitoQ treated prenatally hypoxic male fetuses. Furthermore, factors derived from hypoxic placentae of dams treated with nMitoQ prevented increases in the percentage of binucleated cardiomyocytes (marker of terminal differentiation) and the size of mononucleated and binucleated cardiomyocytes (sign of hypertrophy).
Conclusion: In summary, my studies suggests that treatment strategies targeted against placental oxidative stress can improve placental function in complicated pregnancies and may prevent fetal programming of cardiac disease. However, the mechanisms (i.e. changes in placental morphological and mitochondrial functional capacity) were distinct between males and females. Thus, sex differences need to be taken into account when developing placenta-targeted therapeutic strategies to improve fetal development in complicated pregnancies.
- Graduation date
- Spring 2021
- Type of Item
- Doctor of Philosophy
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