In vitro biomaterial priming of human mesenchymal stromal/stem cells : implication of the Src/JAK/STAT3 pathway in vasculogenic mimicry

Mesenchymal stromal/stem cells (MSC) play a crucial role in promoting neovascularization, which is essential for wound healing. They are commonly utilized as an autologous source of progenitor cells in various stem cell-based therapies. However, incomplete MSC differentiation towards a vascular endothelial cell phenotype questions their involvement in an alternative process to angiogenesis, namely vasculogenic mimicry (VM), and the signal transducing events that regulate their in vitro priming into capillary-like structures. Here, human MSC were primed on top of Cultrex matrix to recapitulate an in vitro phenotype of VM. Total RNA was extracted, and differential gene expression assessed through RNA-Seq analysis and RT-qPCR. Transient gene silencing was achieved using specific siRNA. AG490, Tofacitinib, and PP2 pharmacological effects on VM structures were analyzed using the Wimasis software. In vitro VM occurred within 4 h and was prevented by the JAK/STAT3 inhibitors AG490 and Tofacitinib, as well as by the Src inhibitor PP2. RNA-Seq highlighted STAT3 as a signaling hub contributing to VM when transcripts from capillary-like structures were compared to those from cell monolayers. Concomitant increases in IL6, IL1b, CSF1, CSF2, STAT3, FOXC2, RPSA, FN1, and SNAI1 transcript levels suggest the acquisition of a combined angiogenic, inflammatory and epithelial-to-mesenchymal transition phenotype in VM cultures. Increases in STAT3, FOXC2, RPSA, Fibronectin, and Snail protein expression were confirmed during VM. STAT3 and RPSA gene silencing abrogated in vitro VM. In conclusion, in vitro priming of MSC into VM structures requires Src/JAK/STAT3 signaling. This molecular evidence indicates that a clinically viable MSC-mediated pseudo-vasculature process could temporarily support grafts through VM, allowing time for the host vasculature to infiltrate and remodel the injured tissues.