Amniotic fluid mesenchymal stromal cells from early stages of embryonic development have higher self-renewal potential.

Amniotic fluid (AF) is a rich source of mesenchymal stromal cells (MSCs) that have the ability to differentiate into multiple lineages rendering them a promising and powerful tool for regenerative medicine. However, information regarding the differences among AFMSCs derived from different gestational stages is limited. In the present study, AFMSCs derived from 125 pregnant rats at four embryonic day (E) stages (E12, E15, E18, and E21) were isolated and cultured. The primary E15 cells were the smallest in size and the easiest to culture and usually grew in a spherical shape that resembled the growth morphology of embryonic stem cells (ESCs). Once adhered, the E12 and E15 AFMSCs grew faster and could be passaged more than 60 times while still maintaining a continuous proliferative state; however, AFMSCs derived from E18 and E21 could normally be maintained for only 10 passages. To identify the possible reasons for this difference, RT-qPCR was used to examine several genes associated with self-renewal ability and cell origin. The Sox2 expression levels indicated that AFMSCs from E12 and E15 possessed stronger self-renewal capability. The K19, Col2A1, FGF5, AFP, and SPC expression levels indicated there were mixed-population cells co-existing in the AFMSC culture. In conclusion, E15 cells were easier to culture than E12 cells, could be passaged more often, and had a higher Sox2 expression than E18 or E21 cells. The E15-derived AFMSCs had higher viability and proliferative capacity than cells from the later stages. Therefore, AF cells from the early stages could be a good choice for exploring potential treatments involving AFMSCs.