The Role of High Molecular Weight Kininogen (Fitzgerald Factor) in the Activation of Various Plasma Proteolytic Enzyme Systems

Bovine high molecular weight kininogen (bHMWK) partially corrects the aPTT of Fitzgerald-trait plasma, which is congenitally deficient in HMWK. The relationship between the structure and activity of HMWK was clarified by studying the effects of different fragments of bHMWK on the aPTT of Fitzgerald-trait plasma. The peptides studied, all in equimolar concentrations, were lys-bradykinin-free HMWK, bradyk In In-fragment 1-2-tree HMWK, heavy chain, fragment 1 -2-Hght chain, and light chain. Bradykinin- fragment 1-2-free HMWK, heavy chain, and light chain have little or no correcting activity upon Eitzgeraldtrait plasma aPTT. Fragment 1-2 light chain has the same correcting activity as intact bHMWK, while that of lysbradykinin-free HMWK appears to be higher. Both fragment 1-2 and fragment 2 inhibit the clotting time of normal human plasma. On a molar basis, fragment 2 is a more active inhibitor than fragment 1-2. Bovine plasma kallikrein released kinins from both bHMWK and hHMWK; however, while the correcting activity of bHMWK was completely destroyed after sixty minutes of incubation, that of hHMWK was fully retained. These data suggest that: (1) the active part of bHMWK is comprised of the fragment 1-2 light chain portion; (2) fragment 1-2 or fragment 2 is the binding site to negatively charged surfaces, while the light chain interacts with other components of the surface-mediated reactions; and (3) bovine plasma kallikrein releases kinins but probably does not cause the release of fragment 1-2 from hHMWK

Human Cord Blood-Derived AC133+ Progenitor Cells Preserve Endothelial Progenitor Characteristics after Long Term In Vitro Expansion

Stem cells/progenitors are central to the development of cell therapy approaches for vascular ischemic diseases. The crucial step in rescuing tissues from ischemia is improvement of vascularization that can be achieved by promoting neovascularization. Endothelial progenitor cells (EPCs) are the best candidates for developing such an approach due to their ability to self-renew, circulate and differentiate into mature endothelial cells (ECs). Studies showed that intravenously administered progenitors isolated from bone marrow, peripheral or cord blood home to ischemic sites. However, the successful clinical application of such transplantation therapy is limited by low quantities of EPCs that can be generated from patients. Hence, the ability to amplify the numbers of autologous EPCs by long term in vitro expansion while preserving their angiogenic potential is critically important for developing EPC based therapies. Therefore, the objective of this study was to evaluate the capacity of cord blood (CB)-derived AC133+ cells to differentiate, in vitro, towards functional, mature endothelial cells (ECs) after long term in vitro expansion.We systematically characterized the properties of CB AC133+ cells over the 30 days of in vitro expansion. During 30 days of culturing, CB AC133+ cells exhibited significant growth potential that was manifested as 148-fold increase in cell numbers. Flow cytometry and immunocytochemistry demonstrated that CB AC133+ cells' expression of endothelial progenitor markers was not affected by long term in vitro culturing. After culturing under EC differentiation conditions, cells exhibited high expression of mature ECs markers, such as CD31, VEGFR-2 and von Willebrand factor, as well as the morphological changes indicative of differentiation towards mature ECs. In addition, throughout the 30 day culture cells preserved their functional capacity that was demonstrated by high uptake of DiI fluorescently conjugated-acetylated-low density lipoprotein (DiI-Ac-LDL), in vitro and in vivo migration towards chemotactic stimuli and in vitro tube formation.These studies demonstrate that primary CB AC133+ culture contained mainly EPCs and that long term in vitro conditions facilitated the maintenance of these cells in the state of commitment towards endothelial lineage