Transamniotic Stem Cell Therapy Modulates Uterine Natural Killer Cell Activity in the Hypoxia Model of Intrauterine Growth Restriction.

Intrauterine growth restriction (IUGR) pathophysiology is driven by abnormal uterine natural killer cell (uNK) activity leading to placental dysfunction. Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) can improve experimental IUGR by mechanisms not fully understood. We sought to examine TRASCET's effects in downstream products of uNKs in a model of IUGR: 15 Sprague-Dawley dams were exposed to alternating hypoxia (10.5% O₂) from gestational day 15 (E15) until term (E21). Their fetuses (n = 189) were divided into four groups. One group remained untreated (n = 52), whereas three groups received volume-matched intraamniotic injections of either saline (sham, n = 44) or a suspension of amniotic fluid-derived MSCs, either in their native state (TRASCET, n = 50) or "primed" to an enhanced antiinflammatory phenotype (TRASCET-Primed, n = 43). Normal fetuses served as controls (n = 33). At term, various analyses were performed, including ELISA for surrogates of placental inflammation and uNK activity. Statistical comparisons included Bonferroni-adjusted criterion. Overall survival from hypoxia was 74% (140/189). Placental efficiency was lower in untreated and sham but normalized in both TRASCET groups (P < 0.01-0.47). Interleukin-17, a stimulator of uNKs, was elevated from normal in all groups (P < 0.01 for all). Interferon-gamma, released from activated uNKs, was elevated in all groups except sham but lower than the untreated in both TRASCET groups (P ≤ 0.01-0.06). Tumor necrosis factor-alpha, also produced by uNKs, was elevated in untreated and sham (P < 0.01 for both), but normalized by TRASCET (P = 0.05) and even lowered from normal in TRASCET-Primed (P < 0.01). Vascular endothelial growth factor, also released by uNKs, was elevated in untreated and sham but lower than normal in both TRASCET groups (P < 0.01 for all). We conclude that TRASCET with MSCs modulates the activity of placental uNKs in experimental IUGR, with distinct effects on their downstream products. This mechanistic insight may inform the development of novel strategies for the management of this disease.