Researchers have carried out the most comprehensive profiling of human placental miRNA expression to date, in the hope of driving the development of a non-invasive test to check pregnancy health.
The placenta is an organ that develops in the uterus during pregnancy. It is vital for the transfer of nutrients, gases and wastes between a mother and her foetus. It is now recognised that robust characterisation of normal human placental development can provide insights into pregnancy health and detect any dysfunctions that may lead to complications.
Placental microRNAs
MicroRNAs (miRNAs) are increasingly being viewed as significant regulators of placental development. They are a class of non-coding RNA involved in the regulation of gene expression and are typically around 20-24 nucleotides in length.
Over the last decade, the study of miRNAs has helped scientists to understand developmental pathways within human tissues in greater depth. In particular, many studies have shed light on placental miRNAs and how they potentially target various maternal cells to provide intracellular communication between the mother and the foetus. Perhaps the most significant discovery is that miRNAs of placental origin are continually released in the mother’s bloodstream throughout her pregnancy. Therefore, this indicates that circulating miRNAs have the potential to be used as biomarkers targets for placental function during pregnancy.
However, it is currently difficult to obtain samples during pregnancy in a non-invasive manner, and so investigations into the role of placental miRNAs have been limited. Additionally, there is no comprehensive reference set of miRNA expression data during early pregnancy that can be used for the development of pregnancy health biomarkers.
Generating placental miRNA profiles
Recently, a team of scientists from the University of Adelaide attempted to accurately profile the miRNA landscape of the human placenta and published their findings in Taylor and Francis Online. The group generated a cohort of miRNA expression profiles using a combination of 96 placentas and maternal plasma samples, which were taken at different time points during the participants’ pregnancies.
In total, 637 expressed miRNAs were identified. Over 370 of the miRNAs were differentially expressed between placentas from pregnancies of 6-10 weeks versus 11-23 weeks, indicating that the expression of miRNAs shifts as the placenta matures. These proportional changes in the expression of placenta-specific miRNA were also reflected in the blood plasma samples.
The importance of studying placental miRNAs
This research is the most comprehensive attempt to accurately profile the miRNA landscape of the human placenta to date. The placental tissue dataset, generated using high-throughput sequencing, was substantially larger than any other previous reports. Unsurprisingly, the data presented in this study will now act as a clinically important reference set for miRNA expression during placental development and function. This is particularly true for the early placental developmental time points, which have rarely been explored historically.
The success of this study suggests that profiling miRNA expression in placental tissue and blood plasma samples could underpin the advent of minimally invasive methods for monitoring pregnancy health. Moving forward, the placental biology field will need to continue to deepen their research into miRNAs as biomarkers of pregnancy health to assess their clinical utility and to pave the way for improving patient outcomes.
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