Objective-Tissue factor (TF) initiates coagulation and indirectly triggers thrombin-dependent protease activated receptor (PAR) signaling. The TF-VIIa complex also directly cleaves PAR2 and promotes angiogenesis in vitro in TF cytoplasmic domain-deleted (TF ␦CT ) mice. Here we address the effect of PAR1 and PAR2 deficiency on angiogenesis in vivo. Methods and Results-In hypoxia-driven angiogenesis of oxygen induced retinopathy (OIR), wild-type, PAR1Ϫ/Ϫ , PAR2 Ϫ/Ϫ , and TF ␦CT mice showed a comparable regression of the superficial vascular plexus during the initial exposure of mice to hyperoxia. However, TF ␦CT mice revascularized areas of central vaso-obliteration significantly faster than wild-type animals. Pharmacological inhibition of the TF-VIIa complex, but not of Xa, and blockade of tyrosine kinase receptor pathways with Gleevec reversed accelerated angiogenesis of TF ␦CT mice to revascularization rates observed in wild-type mice. Genetic deletion of PAR2, but not of PAR1, abolished enhanced revascularization of TF ␦CT mice. PAR1 knock-out animals were indistinguishable from wild-type mice in the model of retinal neoangiogenesis and angiogenesis-dependent subcutaneous tumor growth was unaltered in PAR1-and PAR2-deficient animals. Key Words: tissue factor Ⅲ protease activated receptors Ⅲ angiogenesis Ⅲ coagulation Ⅲ thrombin T issue factor (TF), a transmembrane glycoprotein expressed by vascular and myeloid cells, is the primary cellular initiator of blood coagulation. TF exerts its biological activities by forming a catalytic enzyme complex with coagulation factor VIIa. The TF-VIIa complex then triggers coagulation by binding and activating factor X, leading to thrombin-dependent fibrin deposition and platelet activation. Thrombin can exhibit pleiotrophic effects which are typically mediated through G protein-coupled protease activated receptor (PAR) 1 signaling. 1 The TF-VIIa complex also signals directly by cleaving PAR2, but not PAR1. 2,3 However, the relative contributions of direct TF signaling, downstream coagulation activation, and indirect protease signaling to the underlying pathogenesis of cancer progression and angiogenesis, 3 are incompletely defined in vivo. Conclusion-LossTF deficiency results in vascular failure during development 4 and the proangiogenic phenotype of TF cytoplasmic domain deleted (TF ␦CT ) mice provided direct evidence that TF is involved in angiogenesis. 5 Whether direct TF-VIIa signaling is the only relevant pathway to drive angiogenesis in vivo has not been established. Indeed, thrombin-dependent PAR1 signaling stimulates angiogenesis in certain angiogenesis models in vivo, 6 -8 and the partial embryonic lethality of PAR1 knock-out mice attributable to vascular failure resembles the lethal phenotype of TF deficient animals. 9,10 However, the role of PAR1 in postnatal angiogenesis has not been directly addressed in PAR1 knock-out animals.Thrombin and/or TF-signaling pathways are also involved in tumor angiogenesis, 5,11 but production of proangiogenic factors by tumor cell...

No abstract

Skin wound closure occurs when keratinocytes migrate from the edge of the wound and re-epithelialize the epidermis. Their migration takes place primarily before any vascularization is established, that is, under hypoxia, but relatively little is known regarding the factors that stimulate this migration. Hypoxia and an acidic environment are well-established stimuli for cancer cell migration. The carbonic anhydrases (CAs) contribute to tumor cell migration by generating an acidic environment through the conversion of carbon dioxide to bicarbonate and a proton. On this basis, we explored the possible role of CAs in tissue regeneration using mouse skin wound models. We show that the expression of mRNAs encoding CA isoforms IV and IX are increased (~25 × and 4 ×, respectively) during the wound hypoxic period (days 2–5) and that cells expressing CAs form a band-like structure beneath the migrating epidermis. RNA-Seq analysis suggested that the CA IV-specific signal in the wound is mainly derived from neutrophils. Due to the high level of induction of CA IV in the wound, we treated skin wounds locally with recombinant human CA IV enzyme. Recombinant CA IV significantly accelerated wound re-epithelialization. Thus, CA IV could contribute to wound healing by providing an acidic environment in which the migrating epidermis and neutrophils can survive and may offer novel opportunities to accelerate wound healing under compromised conditions.