Beneficial Effects of Thrombomodulin on the Therapeutic Potential of Early Endothelial Progenitor Cells – Mechanism and Application
Date Issued
2012
Date
2012
Author(s)
Li, Jiun-Yi
Abstract
During embryogenesis, a close regional and functional development of peripheral blood and vascular cells suggest the existence of a common origin, the putative hemangioblast. Circulating angioblasts, so-called endothelial progenitor cells (EPC), from human peripheral blood which was able to differentiate in vitro into endothelial cells (EC). EPC significantly contributed to neoangiogenesis after tissue ischemia in vivo and multiple studies have confirmed the pivotal role of EPC in tissue angiogenesis. Accumulated preclinical and clinical data suggest that introduction of exogenous vascular progenitor cells promote vascularization and improve organ function.
Thrombomodulin (TM) is an type I transmembrane glycoprotein containing 5 distinct domains: an NH2-terminal lectin-like region (designated D1), a domain with 6 epidermal growth factor–like modules (D2), an glycosylation site–rich domain (D3), a transmembrane domain (D4), and a cytoplasmic tail domain (D5). TM is well known as a molecule to be an anticoagulant. Subsequent reports showed that TM has various biological roles, including contribution to cell adhesion, migration, proliferation, and anti-inflammation. Recent studies examining recombinant TM domains indicated that the TM domains 2 and 3 (TMD23) contributes to angiogenesis. Because EPCs also participate in angiogenesis, this raised the possibility that human EPCs may express and release TM to facilitate angiogenesis.
In this study, a comprehensive investigation on the behavior of early EPC under TMD23 treatment will be performed. The physiological outcomes in the capacity of angiogenesis will be evaluated by the animal model of hind-limb ischemia. Results showed that TM was expressed and released by human EPCs cultured from peripheral blood mononuclear cells (PBMCs). Addition of TMD23 (100 ng/mL) to the cultured PBMCs increased the colony-forming units, chemotactic motility, matrix metalloproteinase activity, and interleukin-8 secretion but decreased tumor necrosis factor-α (TNF-α) release. Analysis of the signal pathway showed that TMD23 activated Akt. Inhibition of phosphatidylinositol-3 kinase–Akt blocked the effects of TMD23 on chemotactic motility, matrix metalloproteinase-9, interleukin-8, and TNF-α. In hindlimb ischemia mice, laser Doppler perfusion imaging of the ischemic limb during the 21 days after arterial ligation showed that the perfusion recovered best with intraperitoneal infusion of TMD23 plus local injection of early EPCs, followed by either infusion of TMD23 or injection of the cells. Animals without either treatment had the worst results. Animals treated with TMD23 also had lower circulating and tissue levels of TNF-α. In conclusion, TM is expressed and released by human circulating EPCs. Exogenous TMD23 enhances the angiogenic potential of early EPCs in vitro through activation of phosphatidylinositol-3 kinase-Akt pathway. Coadministration of TMD23 plus early EPCs augments therapeutic angiogenesis of the EPCs in ischemic tissues.
Subjects
endothelial progenitor cell
peripheral blood mononuclear cell
thrombomodulin
tumor necrosis factor-α
matrix metalloproteinase
Phosphatidylinositol-3 kinase
Type
thesis
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