The effects of oxygen concentration on in vitro output of prostaglandin E2 and interleukin-6 from human fetal membranes

Single-cell transcriptomics analysis showing functional heterogeneity in decidual stromal cells during labor

To investigate the heterogeneity of decidual stromal cells (DSCs) and their functional alterations during delivery, we conducted single-cell RNA sequencing analysis to characterize the transcriptomic profiles of DSCs before and after labor onset. According to their transcriptomic profiles, DSCs (6382 cells) were clustered into five subgroups with different functions. Similar to stromal cells, cells in cluster 1 were involved in cell substrate adhesion. On the other hand, cells in clusters 2 and 3 were enriched in signal transduction-related genes. Labor onset led to significant alterations in many pathways, including the activator protein 1 pathway (all clusters), as well as in the response to lipopolysaccharide (clusters 1-3). The downregulated genes were involved in coagulation, ATP synthesis, and oxygen homeostasis, possibly reflecting the oxygen and energy balance during delivery. Our findings highlight that peripartum DSCs are heterogeneous and play multiple roles in labor.

Oxygen Tension Strongly Influences Metabolic Parameters and the Release of Interleukin-6 of Human Amniotic Mesenchymal Stromal Cells In Vitro

The human amniotic membrane (hAM) has been used for tissue regeneration for over a century. In vivo (in utero), cells of the hAM are exposed to low oxygen tension (1-4% oxygen), while the hAM is usually cultured in atmospheric, meaning high, oxygen tension (20% oxygen). We tested the influence of oxygen tensions on mitochondrial and inflammatory parameters of human amniotic mesenchymal stromal cells (hAMSCs). Freshly isolated hAMSCs were incubated for 4 days at 5% and 20% oxygen. We found 20% oxygen to strongly increase mitochondrial oxidative phosphorylation, especially in placental amniotic cells. Oxygen tension did not impact levels of reactive oxygen species (ROS); however, placental amniotic cells showed lower levels of ROS, independent of oxygen tension. In contrast, the release of nitric oxide was independent of the amniotic region but dependent on oxygen tension. Furthermore, IL-6 was significantly increased at 20% oxygen. To conclude, short-time cultivation at 20% oxygen of freshly isolated hAMSCs induced significant changes in mitochondrial function and release of IL-6. Depending on the therapeutic purpose, cultivation conditions of the cells should be chosen carefully for providing the best possible quality of cell therapy.

Effect of oxygen tension on bacteria-stimulated cytokine production by fetal membranes

AIM

Tissue culture studies indicate that bacterial products stimulate the production of proinflammatory cytokines by reproductive tissues. However, most of these studies have been performed under room air conditions, supplemented with 5% CO₂. In this study, we tested whether O₂ tension affects bacteria-stimulated cytokine production by extra-placental fetal membranes.

METHODS

Cultures of full-thickness membranes, isolated choriodecidua, and isolated amnion were exposed to bacteria and incubated under 21% (room air) or 5% O₂ for 18 h. Cytokine concentrations in conditioned medium was quantified by immunoassay.

RESULTS

Culture under 5% O₂ increased production of interleukin (IL)-1β and tumor necrosis factor (TNF)-α, but reduced IL-10 and IL-6 production by full membranes. Isolated choriodecidua responded to 5% O₂ with increased IL-1β production and reduced IL-6 production, but had no effect on TNF-α and IL-10 production was not detected. No effect of O₂ tension on IL-1β or IL-6 production by isolated amnion was detected, however, Escherichia coli-stimulated IL-10, TNF-α and IL-8 production was enhanced by culture under 5% O₂.

CONCLUSIONS

Increased oxygen tension reduces the pro-inflammatory responsiveness of cell cultures to E. coli and promotes an anti-inflammatory cytokine profile. Differential effects of O₂ tension on choriodecidua and amnion suggests a network of paracrine factors that regulate cytokine levels in response to changes in O₂ tension.

Comparison of LPS-stimulated release of cytokines in punch versus transwell tissue culture systems of human gestational membranes

BACKGROUND

Cytokine signaling within the amnionic, chorionic and decidual extraplacental gestational membranes plays an important role in membrane rupture and the timing of birth. The predominant in vitro explant culture system for evaluating cytokine induction in human gestational membranes has been the free-floating biopsy punch culture. Punch systems have been used to investigate the impact of various toxicants, pharmaceuticals and genetic variation on expression of pro-inflammatory cytokines. More recently, a dual compartment transwell culture system has been developed that more closely mimics the intrauterine compartment. The current study compares these two systems with respect to release of pro- and anti-inflammatory cytokines in response to lipopolysaccharide (LPS), a model stimulant.

METHODS

Tissue samples were exposed to 100 ng/ml LPS for 12 h and cytokines were measured by ELISA. Data are expressed as increase relative to non-treated controls.

RESULTS

Levels of interleukin-6 increased in punch culture medium samples to a significantly greater extent (34.2 fold) compared with medium from transwell cultures in the amnion (6.6 fold) or choriodecidual (7.1 fold) compartments. Interleukin-8 also showed a significantly greater induction in punch (4.8 fold) than transwell amnion (1.6 fold) or choriodecidual (1.7 fold) samples. The anti-inflammatory interleukin-10 showed a significant difference between punch (36.5 fold) and transwell amnion (15.4 fold) samples, but no difference was observed between punch and transwell choriodecidual (28.5 fold) samples. Neither interleukin-1beta nor tumor necrosis factor-alpha (TNF-alpha) showed a significant difference between the punch and transwell samples.

CONCLUSIONS

These results indicate that the pattern of LPS-stimulated cytokine release from gestational membranes in vitro depends on the culture system used, confounding comparisons of studies that use different gestational membrane culture systems to study inflammatory responses.