Fig. 4.

TrkB does not influence endogenous trophoblast proliferation. First-trimester explants were cultured for 24 h in serum-free conditions and then incubated with the TrkB inhibitory peptide cyclotraxin-B (500 nM to 2 μM) for a further 24 h. Sections were stained using an anti-phospho-TrkB antibody to confirm the inhibitory effect of the peptide (a) or with an anti-Ki67 antibody to assess proliferation. Three random areas from each placenta were counted, and the number of Ki67-positive cells was expressed as a percentage of the total number of cytotrophoblasts (median and IQR) of at least five independent experiments (b). Kruskal–Wallis test of variance followed by Dunn’s multiple comparison post hoc test was used to assess significant (p < 0.05) differences between the groups. ST syncytiotrophoblast, CT cytotrophoblast. Scale bars 50 μm