Human amnion epithelial cells and secretome drive the generation of tolerogenic macrophages and decidua-like NK cells with lower proliferative capability and higher effector functions

Abstract

Background & Aim

Pregnancy is characterized by major immunomodulatory strategies. We previously reported different immune regulatory properties offered by amnion epithelial cells (AEC), isolated from term human placentae. Once transplanted in immune-competent recipients, AEC engrafted and survived, boosting the innate capacity for regeneration. Previous reports described AEC interaction with immune cells (B and T) promoting anti-inflammatory phenotypes, such as regulatory T cells.

Methodology

Now, we investigated AEC effects on macrophages and NK cells. Since AEC therapeutic potential is not mediated by intact cells only, we tested the ability of AEC secretome (AES) to modulate NK and macrophage proliferation, phenotype and functions.

Results

The amount of NK cells was reduced in the presence of AES. The expression of CD57, NKG2C, CD16, and TIGIT was downregulated, whereas the expression of NKG2A, NKp30, NKp46, and NKp44 increased. FACS analysis of surface CD107a expression revealed NK cell cytotoxicity increased (from 12.9% to 27.8%) upon exposure to AES., and cytotoxicity towards K562 cells (26.9%) increased almost 3-fold (73.7%).

Similarly, M2 macrophages increased in a dose-dependent manner. However, such effect was mainly mediated by soluble factors, such as M-CSF, and the vesicular component (AEC-derived EVs) failed to induce M2 polarisation. The extracellular vesicles and proteins released by primary human AECs were quantified by targeted proximity extension assay and several protein of interest, such as VEGF, IL-12B, or M-CSF, were found constitutively expressed, even in hypoxic conditions.

Conclusion

Our preliminary results suggested that secretome of AEC may drive the generation of NK cells with decreased proliferative ability and expression of senescence/exhaustion markers (CD57, NKG2C and TIGIT) and increased cytotoxicity receptor expression (NKG2A, NKp30, NKp44 and NKp46). Accordingly, such NK cells are more cytotoxic against leukemia target cells.

Collectively, our findings support the allogeneic transplantation of human AEC and their active role in local immune regulation, particularly in medical conditions where macrophage response needs to be modulated and contained.

Based on these and largely described immunomodulatory effects on adaptive and innate immune cells, allogeneic AEC-based treatments without immunosuppressants are legitimate, as well as novel cyto-therapeutic strategies for inflammatory disorders and auto-immune conditions.