Mitochondria-Mediated Intercellular Communication: Unveiling the Immunomodulatory Properties of Amniotic Epithelial Cells

Intercellular mitochondrial transfer has attracted great attention in various biomedical fields, including stem cell biology. Understanding the role of this phenomenon in the dialogue between stem and immune cells is essential to grasp the mechanisms leading to immune cell reprogramming, tissue damage and repair, and tumor development. Amniotic Epithelial Cells (AEC) represent an attractive stem cell source, exerting a notable pro-regenerative effect on injured tendons, primarily through the modulation of the early inflammatory phase by controlling different sets of immune cells. While most of the efforts have focused on the molecular mechanisms behind AEC paracrine immune-suppressive action, this study aims to explore their mitochondrial transfer to immune cells after the first evidence of hAEC mitochondria donation to H2O2-damaged cells. The obtained results reveal, for the first time, the presence of functional mitochondria on AEC-derived conditioned media (CM). In detail, ultracentrifugation of CM allowed to fraction EVs containing mitochondria as characterized by WB and FACS. The AEC-EVs compared with CM supernatant showed an enhanced immunosuppressive effect by dumping the activation of PBMC and NFAT pathway in CD3/CD28-stimulated Jurkat cells. Moreover, confocal microscope analysis revealed the transfer of mitochondria to PBMCs exposed to AEC-EVs. Of note, this process was blocked by an anti-CD44-neutralising antibody, which also significantly inhibited the immune-suppressive action of AEC-EVs. Overall, these findings elucidate the mitochondria-mediated intercellular communication between AEC and immune cells as one of the key processes involved in their immunomodulatory properties, opening new insights for targeted therapeutics aimed at enhancing tendon regeneration.