Formation and activation of fibroblast spheroids depend on fibronectin-integrin interaction.

Clustering of fibroblasts into spheroids induces a massive proinflammatory, proteolytic and growth-factor response, named nemosis, which promotes tumor cell invasiveness and differentiation of leukemia cells. We have now sought to investigate mechanisms leading to the formation of multicellular spheroids and subsequent activation of fibroblasts (nemosis). Cell lines either lacking fibronectin expression (FN-/-) or expressing FN with a mutated integrin-binding site (FNRGE/RGE) were unable to form compact spheroids.

Cell-cell contact activation of fibroblasts increases the expression of matrix metalloproteinases.

Background: We recently found that direct homotypic cell-cell contacts between human dermal fibroblasts induce a novel form of cell activation leading to non-apoptotic programmed cell death. As the major features of this process we identified massive induction of cyclo-oxygenase-2 and production of inflammatory prostaglandins. On the surface of the decomposing spheroids, activation of the major extracellular proteolytic cascade, plasminogen activation, associated with surface exposure of alpha-enolase, took place.

High concentrations of plasminogen activator inhibitor-1 in lungs of preterm infants with respiratory distress syndrome.

Background: Among preterm infants, respiratory distress syndrome (RDS) is characterized by the presence of intraalveolar fibrin deposition. Fibrin monomers inhibit surfactant function effectively. However, little is known about potential disturbances of intraalveolar fibrinolysis in RDS.

Plasminogen activators and their inhibitors in human saliva and salivary gland tissue.

The purpose of this study was to identify plasminogen activators (PA) and their specific inhibitors in human cell-free saliva and to investigate their expression in salivary gland tissue. Saliva samples were obtained from 34 patients visiting a neurological out-patient department. The activities of tissue and urokinase plasminogen activators (tPA and uPA, respectively), the relative inhibition of tPA, and the amounts of plasminogen activator inhibitors 1 and 2 (PAI-1 and PAI-2, respectively) in cell-free saliva were studied.

Plasminogen activators and their inhibitor gene expression in cutaneous NF1-related neurofibromas.

Cutaneous neurofibromatosis 1 (NF1)-related neurofibromas are benign tumors and composed of Schwann cells, perineurial cells and/or fibroblasts, endothelial cells, mast cells and macrophages. Extracellular proteolysis namely plasminogen activation (PA) operates in many tissue destructive processes. We wanted to study plasminogen activators, urokinase (uPA) and tissue type (tPA) and their inhibitor PAI-1, which have not earlier been studied comprehensively in cutaneous NF1-related tumors.

Co-localization of human herpes virus 6 and tissue plasminogen activator in multiple sclerosis brain tissue.

Background: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system of unknown etiology. Several viruses have been suggested as playing a role in the pathogenesis of MS. The aim of this study was to investigate the interrelationship of human herpesvirus 6 (HHV-6) and plasminogen activation at the cellular level in MS plaques.

Epithelial tissue-type plasminogen activator expression, unlike that of urokinase, its receptor, and plasminogen activator inhibitor-1, is increased in chronic venous ulcers.

Background: The plasminogen activation system represents a potent mechanism of extracellular proteolysis and is an essential component of normal wound healing. It has also been implicated in the pathogenesis of chronic, nonhealing ulcers. Traditionally, urokinase-type plasminogen activator (uPA) has been associated with pericellular proteolytic activity involved in tissue remodelling processes, and tissue-type plasminogen activator (tPA) mainly with intravascular fibrinolysis.

Biodegradable tube implants in experimental glaucoma surgery in the rabbit.

Although ocular drainage implants are manufactured from biocombatible materials to reduce foreign-body reaction, the formation of excessive scar tissue around the implant is a common cause for implant failure. In this study, the suitability of poly(D, L-lactide-co-glycolide) copolymer, impregnated with an antiproliferative agent retinoic acid, was evaluated as a material for biodegradable tubular implants, as well as the duration and magnitude of the intraocular pressure reduction obtained with the prototype implant. Subconjunctivally placed retinoid-impregnated polymer particles caused a milder inflammatory reaction than plain polymer, and the layer of connective tissue around the material was thinner after the follow-up period of 60 d.

Plasminogen activation in neurofibromatosis 2-associated and sporadic schwannomas.

Background: Schwannomas are usually benign tumours which occur sporadically or in association with neurofibromatosis 2 (NF2), an autosomal dominant disorder. Invasiveness and higher proliferative potential compared to sporadic tumours are features of NF2-associated schwannomas.

Method: We studied urokinase (uPA), tissue-type plasminogen activator (tPA), urokinase receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1) expression by in situ hybridization and by immunohistochemistry in 14 NF2 and 15 sporadic patients with 34 schwannomas.

uPA, tPA and PAI-1 mRNA expression in periretinal membranes.

Purpose: Formation of periretinal membranes occurs in proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR) and includes cell migration, proliferation, extracellular matrix formation and tissue contraction, processes in which plasminogen activation (PA) system is involved.

Methods: Twenty PVR, PDR or pucker membranes were examined to identify the cells with cell specific markers and to detect the expression of urokinase (uPA), tissue-type plasminogen activator (tPA) or plasminogen activator inhibitor-1 (PAI-1) by in situ hybridization and by immunohistochemistry.

Results: In PVR, uPA, tPA and PAI-1 were expressed by retinal pigment epithelial (RPE) cells, macrophages or retinal glial cells.

Urokinase, tissue-type plasminogen activator and plasminogen activator inhibitor-1 expression in severely stenosed and occluded vein grafts with thrombosis.

Intimal hyperplasia and subsequent thrombotic occlusions limit the success of vascular reconstructive procedures. Plasminogen activation in situ may be an important factor affecting re-stenosis of the graft. Tissue specimens from eight patients with failing or failed infra-inguinal vein bypasses and three specimens from normal veins were harvested to study urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) by in situ hybridization and immunohistochemistry.

Differential effects of acute and chronic wound fluids on urokinase-type plasminogen activator, urokinase-type plasminogen activator receptor, and tissue-type plasminogen activator in cultured human keratinocytes and fibroblasts.

The effect of wound fluids collected from acute well-healing wounds and chronic nonhealing venous leg ulcers on the plasminogen activation system of keratinocyte and fibroblast cell cultures was studied in a simplified wound-healing model. Acute wound fluid was collected from donor sites of split skin grafts at different time points representing the progressive healing of the wound. Urokinase-type plasminogen activator, tissue-type plasminogen activator, urokinase-type plasminogen activator receptor, and plasminogen activator inhibitor 1 expression were studied.

Tissue plasminogen activator gene expression in multiple sclerosis brain tissue.

Recent studies have implicated tissue-type plasminogen activator (tPA) in neurodegeneration. We studied multiple sclerosis (MS) brain tissue for tPA gene and protein expression in comparison with reference tissue, by in situ hybridisation and immunohistochemistry. MS is characterised by demyelination in the central nervous system.

Transforming growth factor beta induces urokinase receptor expression in cultured retinal pigment epithelial cells.

The effect of transforming growth factor-beta1 (TGF-beta1) and interferon-gamma (IFN-gamma) was studied on urokinase receptor (uPAR) expression of cultured human retinal pigment epithelial (RPE) cells. Human RPE cells were incubated with 1, 5 or 10 ng/ml of TGF-beta1 or with 10, 100 or 1,000 IU/ml of IFN-gamma to measure total cellular uPAR protein and released uPAR by enzyme immunoassay. uPAR at cell surface was measured by flow cytometric analysis at 8, 12, 24 and 48 h.

Interferons and retinoids enhance and dexamethasone suppresses urokinase-mediated plasminogen activation in promyelocytic leukemia cells.

All-trans retinoic acid (RA) has been successfully used in the treatment of patients with acute promyelocytic leukemia (APL). It induces differentiation of APL cells and reduces the bleeding tendency in APL patients. It has been proposed that plasminogen activation could affect the fibrinolytic balance in patients with leukemia.

Plasminogen activator inhibitor-1 in neointima of vein grafts: its role in reduced fibrinolytic potential and graft failure.

Background: Intimal smooth muscle cell proliferation is an underlying pathogenetic mechanism for neointimal hyperplasia and consequent vein graft failure. This study characterizes the expression of tissue-type plasminogen activator (TPA), urokinase-type plasminogen activator (UPA), and plasminogen activator inhibitor-1 (PAI-1) in hyperplastic vein grafts and normal venous tissue.

Methods And Results: Failing graft and control vein specimens from 14 donors were homogenized, and TPA and PAI-1 were quantified with ELISA.

Plasminogen activation in epiretinal membranes.

Background: Formation of epiretinal membranes occurs in proliferative vitreoretinopathy, macular pucker and after penetrating trauma. Epiretinal membrane formation includes cell migration and proliferation, extracellular matrix formation and tissue contraction. Generally in scar tissue formation, the production of new extracellular matrix occurs concomitantly with its proteolytic degradation, resulting in continuous tissue remodelling.

Cerebrospinal fluid activity of tissue plasminogen activator in patients with neurological diseases.

Aim: To study cerebrospinal fluid (CSF) activity of tissue plasminogen activator (tPA) in patients with neurological diseases.

Methods: CSF tPA and urokinase (uPA) activities were studied using an immunocapture assay and zymography in 44 patients with neurological disease and 20 reference subjects. The patient group comprised three patients with meningitis, 21 with encephalitis, nine with acute lymphoblastic (n = 7) and myeloid (n = 2) leukaemia, seven with multiple sclerosis, three with facial paresis, and one with polyradiculitis.

Keratinocyte growth factor enhances urokinase-type plasminogen activator activity in HPV16 DNA-immortalized human uterine exocervical epithelial cells.

We recently demonstrated that keratinocyte growth factor (KGF), a fibroblast-derived growth factor, induced anchorage-independent growth of HPV16 DNA-immortalized human uterine exocervical epithelial cells (HCE16/3 cell line) in soft agarose assay. We have now studied whether KGF might also regulate the plasminogen activator (PA) system, another transformation parameter related to cell invasiveness. HCE16/3 cells were found to produce urokinase-type PA (uPA) and small amounts of tissue-type PA (tPA) as determined by immunocapture assay.

Proteinases in subretinal fluid.

Background: Degradation of the extracellular matrix by secreted proteases is connected to cell migration and proliferation in invasive growth and in scar tissue formation. In retinal detachment, retinal pigment epithelium (RPE) cells loosened from their monolayer are often seen in the subretinal fluid (SRF) and the vitreous, where they may participate in the scar tissue formation of proliferative vitreoretinopathy. To evaluate the role of SRF constituents on the release of RPE cells, we analyzed SRF in patients with retinal detachment for the presence of enzymes able to degrade extracellular matrix.

Secretion of plasminogen activators by cells cultured from subretinal fluid.

Secretion of plasminogen activators was examined in 11 cells cultures from subretinal fluid of patients with retinal detachment. The plasminogen activator production was compared to 4 retinal pigment epithelial cell cultures from post-mortem donors with no known retinal pathology. Plasminogen activator activity was evaluated by zymography and was corrected for the total cell protein in the cultures.

Alpha- and gamma-interferon inhibit plasminogen activator inhibitor-1 gene expression in human retinal pigment epithelial cells.

The effect of interferons IFN-alpha and IFN-gamma on the production of plasminogen activators (PAs) and plasminogen activator inhibitors (PAIs) was examined in human retinal pigment epithelial (RPE) cells in culture. Cultures of human RPE cells were incubated with either of the interferons for 48-96 h. The cell cultures were assayed using mRNA analysis and solid-phase immunocapture assay.

Retinal pigment epithelial cells secrete urokinase-type plasminogen activator and its inhibitor PAI-1.

Secretion of plasminogen activators and their inhibitors was examined in cultures of human retinal pigment epithelial (RPE) cells. The methods employed were zymography and reverse zymography, solid-phase immunocapture assay, metabolic labeling followed by immunoprecipitation, and immunofluorescence. The results showed that these cells produce urokinase-type plasminogen activator (u-PA) and a plasminogen activator inhibitor (PAI) which is immunologically and biochemically similar to PAI-1.