Annexin A1 Contained in Extracellular Vesicles Promotes the Activation of Keratinocytes by Mesoglycan Effects: An Autocrine Loop Through FPRs.

We have recently demonstrated that mesoglycan, a fibrinolytic compound, may be a promising pro-healing drug for skin wound repair. We showed that mesoglycan induces migration, invasion, early differentiation, and translocation to the membrane of keratinocytes, as well as the secretion of annexin A1 (ANXA1), further involved in keratinocytes activation. These events are triggered by the syndecan-4 (SDC4)/PKCα pathway. SDC4 also participates to the formation and secretion of microvesicles (EVs) which may contribute to wound healing. EVs were isolated from HaCaT cells, as human immortalized keratinocytes, and then characterised by Western blotting, Field Emission-Scanning Electron Microscopy, and Dynamic Light Scattering. Their autocrine effects were investigated by Wound-Healing/invasion assays and confocal microscopy to analyse cell motility and differentiation, respectively. Here, we found that the mesoglycan increased the release of EVs which amplify its same effects. ANXA1 contained in the microvesicles is able to promote keratinocytes motility and differentiation by acting on Formyl Peptide Receptors (FPRs). Thus, the extracellular form of ANXA1 may be considered as a link to intensify the effects of mesoglycan. In this study, for the first time, we have identified an interesting autocrine loop ANXA1/EVs/FPRs in human keratinocytes, induced by mesoglycan.

Annexin A1 May Induce Pancreatic Cancer Progression as a Key Player of Extracellular Vesicles Effects as Evidenced in the In Vitro MIA PaCa-2 Model System.

Pancreatic Cancer (PC) is one of the most aggressive malignancies worldwide. As annexin A1 (ANXA1) is implicated in the establishment of tumour metastasis, the role of the protein in PC progression as a component of extracellular vesicles (EVs) has been investigated. EVs were isolated from wild type (WT) and ANXA1 knock-out (KO) PC cells and then characterised by multiple approaches including Western blotting, Field Emission-Scanning Electron Microscopy, and Dynamic Light Scattering. The effects of ANXA1 on tumour aggressiveness were investigated by Wound-Healing and invasion assays and microscopic analysis of the Epithelial to Mesenchymal Transition (EMT). The role of ANXA1 on angiogenesis was also examined in endothelial cells, using similar approaches. We found that WT cells released more EVs enriched in exosomes than those from cells lacking ANXA1. Notably, ANXA1 KO cells recovered their metastatic potential only when treated by WT EVs as they underwent EMT and a significant increase of motility. Similarly, human umbilical vein endothelial cells (HUVEC) migrated and invaded more rapidly when treated by WT EVs whereas ANXA1 KO EVs weakly induced angiogenesis. This study suggests that EVs-related ANXA1 is able to promote cell migration, invasion, and angiogenesis, confirming the relevance of this protein in PC progression.