Digital PCR quantification of DNA, RNA and extracellular microRNA of mouse oocytes

Despite numerous advances in in vitro fertilization (IVF) techniques since its first success in 1978, almost half of the patients treated remain childless. The multifactorial nature of IVF treatment means that success is dependent on variables, including the quality of oocytes. Therefore, new technologies are needed to objectively and quantitatively examine how each oocyte can be selected or optimized to achieve for the best possible outcomes for patients. Here, we report an optimized digital polymerase chain reaction (dPCR) for direct absolute quantification of nucleic acids within 3.5 h without the need for sample extraction or purification. Using individual oocytes, the developed method demonstrated absolute quantification with a linear dynamic range of 0.65 - 33 copies/{micro}L (r2=0.999), high accuracy and excellent reproducibility of <10% relative standard deviation. The method then identified the variable expression of Gapdh (0.72-16.95 copies/oocyte), Hprt1 (1.05-19.05 copies/oocyte) and ATPase 6, (5.55-32358.15 copies/oocyte) in ovaries even from the same mouse. Finally, dPCR was used to validate extracellular microRNAs from oocytes incubated with a toxic unsaturated very-long chained ceramide. This study therefore shows the feasibility of dPCR for the rapid and sensitive absolute quantification of DNA/RNA and extracellular miRNA for the study of oocytes.