Abstract: To investigate the distribution pattern of mesenchymal stem cells (MSCs) in human placentas by immunofluorescence staining and immunohistochemical staining. MethodsFresh normal term placental tissues were taken from cesarean section without medical indication, and based on the central zone(A), the intermediate zone(B), the marginal zone(C), the chorionic plate layer(a), the middle layer(b) and the basal layer(c), they were divided into 9 groups: the Aa, Ab, Ac, Ba, Bb, Bc, Ca, Cb and Cc groups. Then, serial section, immunofluorescence staining and immunohistochemical staining were used to study the expressions of CD166, D44 and CD29. The HPIAS1000 colored image analysis system was used to analyze distribution of positive expression cells. ResultsCD166, CD44 and CD29 positive cells were mainly concentrated in the area under vascular endothelial cells and in the stroma surrounding the vessel. There were many strongly positive cells in the intermediate zone and the middle layer of the placenta (Ab) and few positive cells in the marginal zone(C). ConclusionCD166, CD44 and CD29 positive cells could be found in every position in human placentas, but were mainly distributed in the intermediate zone and the middle layer of the placenta (Ab).

Key words: Mesenchymal stem cells, Placenta, Location, Staining