Abstract Background Tissue Factor (TF) is a transmembrane glycoprotein classically known as the initiator of coagulation but also plays a critical role in angiogenesis. Adipose-derived stem cells (ASCs) express TF and contribute to vascular remodeling, yet excessive TF can increase procoagulant risk. Understanding how TF signaling drives ASC-mediated neovascularization is key for the safe development of cell-based therapies. Methods Human ASCs were cultured or treated with conditioned media and microvesicles (MVs) derived from HMEC-1 with differential TF expression (siTF, upTF). Tube formation assays, western blot, and immunofluorescence for SMAD2/3 phosphorylation were performed. The effects of recombinant TF and Activin A, as well as pharmacologic blockade of PAR2 and Activin A signaling, were evaluated. MVs were characterized by nanoparticle tracking, TEM, and coagulation activity assays. Results TF expression in ASCs was upregulated by endothelial conditioned medium and TF-rich MVs, enhancing the formation and stability of tube-like networks. TF silencing or inhibition of PAR2 abrogated these effects, while recombinant TF partially rescued angiogenic capacity. Activin A secretion by HMEC-1 cooperated with TF signaling, converging on SMAD2/3 activation to stabilize tubular structures. Combining TF and Activin A stimulation maximized angiogenic network stability, whereas dual blockade disrupted tube formation. Conclusions Our findings identify a cooperative signaling axis between TF–PAR–SMAD3 and Activin A–SMAD2 that governs ASC-mediated angiogenesis. This dual mechanism integrates coagulation-linked and TGFβ-related pathways to promote stable vascular network formation. Targeting this balance may optimize ASC-based regenerative therapies while minimizing thrombogenic risk.
Urgell et al. (Fri,) studied this question.