【Objectives】 To isolate and identify exosomes from human amniotic fluid and determine their RNA concentration

hence provide a potential biomarker for prenatal diagnosis of fetal kidney disease and evaluation of fetal kidney function. 【Methods】Using routine amniocentesis to acquire 10 mL of amniotic fluid respectively from eight gravidas in the second trimester. The amniotic fluid was subjected to differential centrifugation in order to obtain the purified exosomal pellet. Exosomes were identified by using transmission electron microscopy (TEM)

flow cytometry (FCM)

and confocal laser scanning microscope (CLSM). TRIzol was applied to extract RNA from exosomes. The concentration of total RNA was determined through ultraviolet spectrophotometer. 【Results】 A pure exosomal population was present with typical cup-shaped morphology

surrounded by a two-layer lipid membrane

and varying in size between 40 nm -100 nm under TEM. Negative staining effect was manifested both surround and inside the exosomes. We confirmed the presence of exosomes through its specific marker by FCM with anti-CD24 antibody

with a positive rate of (92.23±3.8)%. Fluorescent light emitted by FITC mouse anti-human CD24 antibodies binding to the exosomes was observed surrounding the latex beads under CLSM. The concentration of RNA from amniotic fluid were 28.67 ng/μL

30.02 ng/μL

37.57 ng/μL

21.08 ng/μL

49.41 ng/μL

24.57 ng/μL

24.24 ng/μL

and 26.77 ng/μL

with the average amount of 30.29 ng/μL. 【Conclusion】 Expression of kidney-specific CD24 molecule on exosomes from human amniotic fluid could serve as an evidence of its origination from the fetal kidneys. RNA in exosomes could be used as a novel material for the prenatal diagnosis of fetal kidney diseases and to evaluate fetal kidney function in the future.