We have previously shown that
microRNAs (
miRNAs) in nipple discharge are potential diagnostic
biomarkers. In particular, exosomes are present in nipple discharge. Herein, we sought to elucidate the protective role of exosomes on
miRNAs in nipple discharge and investigate the stability of
miRNAs encapsulated in exosomes under degradative conditions. A novel TTMAAlPc-
RNA complex method was used to measure the
RNase concentration in colostrum and nipple discharge. Quantitative real-time polymerase chain reaction was performed to test the stability of exogenous synthetic
miRNAs (cel-lin-4-5p and cel-miR-2-3p) and endogenous
miRNAs (hsa-miR-4732-5p, hsa-miR-3646, hsa-miR-4484, and kshv-miR-K12-5-5p).
RNase was present and functional in colostrum and nipple discharge. Endogenous
miRNAs were more stably expressed compared to exogenous
miRNAs at room temperature and 4°C.
Triton X-100 (1%, 30 min) destroyed the exosomal membrane, causing RNA degradation in colostrum but not in nipple discharge. Therefore, we confirmed that exosomes in colostrum and nipple discharge could protect
miRNAs from degradation by
RNase. Exosomes in nipple discharge may be more resistant to
Triton X-100 lysis compared to those in the colostrum. Exosomal
miRNAs in nipple discharge in
breast cancer are stable under degradative conditions. Differential
Triton X-100 sensitivity of exosomes of nipple discharge and colostrum warrants further investigation.