(A) Representative flow cytometry plots showing uterine NK (uNK) cell purity following 18 hours of culture. (B) Immunoblot showing decorin in uNK cell conditioned media (CM) from 3 distinct obese uNK cell cultures. Decidual tissue (Decidua) and control media (RPMI) function as positive and negative controls, respectively. Molecular weights (kDa) are shown to the left. (C) A schematic representation of the experimental procedure and timeline: CM = conditioned medium; DCN Ab = decorin-neutralizing antibody; d = day. (D) Quantification of extravillous trophoblast (EVT) column outgrowth in control (Con) and uNK cell CM–treated (uNK CM) placental explants in the presence or absence of a decorin-blocking antibody (DCN Ab). Outgrowth is calculated as the difference in column length (μm) at 48 and 0 hours. Explant assays were performed in duplicate using placental villi from 3 independent placentae (n = 12 to 14 columns per condition). (E) Representative images of placental villous explants cultured in control media, or in uNK CM with/without DCN Ab at 0 and 48 hours of culture. Inverted images of explants (invert) provide better contrast, where “villi” indicates placental villi, and hashed lines represent the EVT column base (white) and invasive extremity (black). Scale bars: 100 μm. Quantification (F) and representative images (G) of EVT column outgrowth following treatment with (n = 10 columns) or without (n = 10 columns) 20 μg/ml recombinant decorin (DCN). Placental explants were established from 4 independent placentae. (H) Representative images showing proliferative (Ki67⁺; red) and apoptotic (caspase-cleaved cytokeratin-18⁺ [K18⁺]; green) trophoblasts within EVT columns. The trophoblast marker keratin-7 (K7) is labeled white and nuclei are stained with DAPI (blue). Scale bars: 100 μm. The percentage of (I) proliferative and (J) apoptotic trophoblasts in DCN-untreated/treated cultures, calculated as the number of Ki67⁺ or cleaved cytokeratin-18⁺ cells into numbers of trophoblasts (K7⁺ cells). Results are presented as scatter plots with the indicated median values shown as horizontal lines. Statistical analyses between groups were performed using a nonparametric 2-tailed Mann-Whitney t test.