E. I. Ratner

Urokinase Plasminogen Activator in Injured Adventitia Increases the Number of Myofibroblasts and Augments Early Proliferation

Myofibroblasts are involved in vessel remodeling during the development of hypertension as well as after angioplasty and aortocoronary grafting, but the mechanisms of myofibroblastic phenotypic modulation are not fully elucidated. We assessed the role of urokinase plasminogen activator (uPA) and its proteolytic activity in myofibroblast differentiation and the early proliferation following mechanical injury of the rat carotid adventitia. The effects of perivascular application of recombinant uPA (r-uPA), proteolytically inactive r-uPA(H/Q) and uPA neutralizing antibody were evaluated 4 days after surgical injury to the adventitia. The phenotype of adventitial cells was assessed using anti-α-smooth muscle actin (α-SM actin) antibody, anti-SM heavy chain myosin, anti-high-molecular-weight caldesmon, anti-smoothelin and anti-ED-1 antibodies, proliferation by the expression of proliferating cell nuclear antigen, and the size of the adventitia by quantitative morphometry. Four days after injury, the intensive immunostaining for urokinase appeared in the rat carotid artery adventitia. At the same time, the frequency of α-SM actin-positive adventitial cells was 1.8 ± 1.1% in uninjured arteries and 25.2 ± 5.4% in injured arteries (p < 0.05), and the respective frequency of ED-1-positive cells 1.5 ± 1.1 and 25.0 ± 5.2%. The application of exogenous r-uPA doubled the numbers of α-SM actin-positive adventitial cells to 55.7 ± 6.8% (p < 0.05). ED-1-positive cells and proliferating cell nuclear antigen-positive cells as well as the size of the adventitia were also significantly increased after r-uPA compared with injury alone. In contrast, the proteolytically inactive r-uPA(H/Q) did not affect any parameters. The application of uPA neutralizing antibody attenuated the frequency of α-SM actin-positive cells to 12.6 ± 3.5% (p < 0.05), the frequency of ED-1-positive cells, and the numbers of adventitial cells. r-uPA stimulation of cultured human skin fibroblasts significantly increased the α-SM actin content in a concentration-dependent manner. In contrast, r-uPA(H/Q) did not induce changes in α-SM actin content. We conclude that uPA, which is upregulated in the injured adventitia, can augment adventitial cell accumulation, including myofibroblasts, and adventitia growth early after injury of the rat carotid artery adventitia by mechanisms involving proteolysis.

Latent Inflammation and Insulin Resistance in Adipose Tissue

Obesity is a growing problem in modern society and medicine. It closely associates with metabolic disorders such as type 2 diabetes mellitus (T2DM) and hepatic and cardiovascular diseases such as nonalcoholic fatty liver disease, atherosclerosis, myocarditis, and hypertension. Obesity is often associated with latent inflammation; however, the link between inflammation, obesity, T2DM, and cardiovascular diseases is still poorly understood. Insulin resistance is the earliest feature of metabolic disorders. It mostly develops as a result of dysregulated insulin signaling in insulin-sensitive cells, as compared to inactivating mutations in insulin receptor or signaling proteins that occur relatively rare. Here, we argue that inflammatory signaling provides a link between latent inflammation, obesity, insulin resistance, and metabolic disorders. We further hypothesize that insulin-activated PI3-kinase pathway and inflammatory signaling mediated by several IκB kinases may constitute negative feedback leading to insulin resistance at least in the fat tissue. Finally, we discuss perspectives for anti-inflammatory therapies in treating the metabolic diseases.

Urokinase stimulates production of matrix metalloproteinase-9 in fibroblasts with involvement of reactive oxygen species.

In cultured fibroblasts, urokinase stimulated expression of MMP-9 and generation of ROS, while antioxidant ebselen abolished the stimulating effect of urokinase on MMP-9 expression. sTNF-α produced similar and more pronounced stimulating effect. The data showed that urokinase could regulate MMP-9 expression via ROS generation in fibroblasts, which can play an important role in stimulation of their migration and development of constrictor (negative) vascular remodeling due to thickening of the adventitia.

Urokinase increases the content and activity of matrix metalloproteinases 2 and 9 during in vivo constrictive arterial remodeling.

Perivascular application of urokinase to ballooned artery stimulating the formation of neointima and constrictive arterial remodeling increased the content and activity of matrix metalloproteinases 2 and 9 in vivo. Application of recombinant tissue plasminogen produced no such changes. It was demonstrated that urokinase stimulates expression of matrix metalloproteinases in vivo.

Urokinase stimulates inflammatory response in damaged vascular wall during in vivo arterial remodeling

Perivascular application of urokinase to the ballooned artery promoted the growth of neointima and constrictive remodeling of the vessel and stimulated the inflammatory response in the damaged vascular wall in vivo. Recombinant tissue plasminogen activator did not induce these changes. Our results indicate that urokinase is involved in the regulation of the inflammatory response during in vivo remodeling of the damaged vascular wall.

Modulation of the Inflammatory Status of Macrophages and Their Paracrine Effect on the Sensitivity of Adipocytes to Insulin with Sirtuin and PPARγ Receptor Activators

We studied the effect of SIRT1 deacetylase and PPARγ receptor activators on proinflammatory (M1), anti-inflammatory (M2) polarization of RAW264.7 macrophages and their modulating effects on insulin sensitivity of adipocytes. In M1 macrophages, the expression of TNFα and CXCL9, secretion of CXCL11, ROS generation, and content of dendritic-like cells were elevated. In M2 macrophages, expression of IGF-1 and ALOX15 factors was enhanced. SIRT1 activator (DCHC) and PPARγ receptor ligand (rosiglitazone) reduced expression of inflammatory markers TNFα and CXCL9 and increased expression of IGF-1 and ALOX15. SIRT1 inhibitor Ex527 increased the proportion of dendritic cells in macrophage populations. The paracrine effect of M1-macrophage-conditioned media attenuated insulin-dependent phosphorylation of threonine (Thr308) in Akt kinase and enhanced phosphorylation of serine (Ser473). This effect was attenuated by DCHC and rosiglitazone.

C-Kit Cardiac Progenitor Cell Based Cell Sheet Improves Vascularization and Attenuates Cardiac Remodeling following Myocardial Infarction in Rats

The adult heart contains small populations of multipotent cardiac progenitor cells (CPC) that present a convenient and efficient resource for treatment of myocardial infarction. Several clinical studies of direct CPC delivery by injection have already been performed but showed low engraftment rate that limited beneficial effects of procedure. «Cell sheet» technology has been developed to facilitate longer retention of grafted cells and show new directions for cell-based therapy using this strategy. In this study we hypothesized that СPC-based cell sheet transplantation could improve regeneration after myocardial infarction. We demonstrated that c-kit+ CPC were able to form cell sheets on temperature-responsive surfaces. Cell sheet represented a well-organized structure, in which CPC survived, retained ability to proliferate, expressed progenitor cell marker Gata-4 formed connexin-43+ gap junctions, and were surrounded by significant amount of extracellular matrix proteins. Transplantation of cell sheets after myocardial infarction resulted in CPC engraftment as well as their proliferation, migration, and differentiation; cell sheets also stimulated neovascularization and cardiomyocyte proliferation in underlining myocardium and ameliorated left ventricular remodeling. Obtained data strongly supported potential use of CPC sheet transplantation for repair of damaged heart.

Regulatory Effects of Urokinase on Mesenchymal Stromal Cell Migration, Proliferation, and Matrix Metalloproteinase Secretion

We studied the effect of urokinase, its recombinant forms, and domain fragments on migration and proliferation of adipose tissue mesenchymal stromal cells (MSCs) and MMP secretion by these cells. Urokinase, but not its recombinant forms, slightly induced directed migration of MSCs. Spontaneous migration of MSCs increased under the action of urokinase or its isolated kringle domain. Migration induced by platelet-derived growth factor was inhibited by proteolytically inactive form of urokinase, the kringle domain, and blocking antibody to urokinase receptor. Urokinase, its proteolytically inactive form, and kringle domain produced no effect on MSC proliferation. In contrast to platelet-derived growth factor, all urokinase forms induced secretion of MMP-9 by MSCs.