Expression of plasminogen activator and plasminogen activator inhibitor mRNA in human fibroblasts grown on different substrates

Cell growth and protein formation on various microcarriers

A large number of microcarriers are commercially available. The capability of cells to successfully proliferate on microcarriers varies with cell lines and media. Choosing the right microcarrier for a particular cell line is more than a choice of a microcarrier. It is part of an integrated process design. A detailed picture of cell growth and product formation will not only be essential in identifying the kind of microcarrier, but also in determining other parts of the process, such as operation mode and media. Our initial screening on thirteen microcarriers showed that cultures on some microcarriers reached a low cell density but high cell-specific productivity, and high density microcarrier cultures have a low specific productivity. The result is a similar product output per unit volume and time for these two types of cultures. An ideal culture system shall have increased volumetric productivity at elevated cell density. This requires the process goal to be incorporated as early as cell line construction and screening. A high output process can then be realized through high density culture.

Synthesis, regulation and production of urokinase using mammalian cell culture: a comprehensive review

Urokinase, a serine protease, catalyzes the conversion of plasminogen to plasmin, which is responsible for dissolution of clots in blood vessels. It is an important drug for treatment of thromboembolic disease. Production of urokinase by mammalian cell culture has the following important steps: synthesis, regulation and secretion. Production and accumulation of this product in a bioreactor is a real challenge for biochemical engineers. Considerable information at molecular level needs to be understood for production of urokinase in order to correlate different parameters, which in turn can maximize the productivity. This information will be highlighted in this review. Moreover, urokinase production is a product-inhibited process. Therefore, in situ urokinase separation strategy is required to operate a bioreactor at its maximum urokinase formation rate. Integrated urokinase production and isolation processes developed recently will also be discussed briefly in this review.

Induction of the plasminogen activator system accompanies peripheral nerve regeneration after sciatic nerve crush

Peripheral nerve regeneration is dependent on the ability of regenerating neurites to migrate through cellular debris and altered extracellular matrix at the injury site, grow along the residual distal nerve sheath conduit, and reinnervate synaptic targets. In cell culture, growth cones of regenerating axons secrete proteases, specifically plasminogen activators (PAs), which are believed to facilitate growth cone movement by digesting extracellular matrices and cell adhesions. In this study, the PA system was shown to be specifically activated in sensory neurons after sciatic nerve crush in adult mice. The number of sensory neurons expressing urokinase PA receptor (uPAR) mRNA levels increased above sham levels by 8 hr after crush, whereas the number of sensory neurons expressing uPA and tissue PA (tPA) mRNAs was significantly increased by 3 d after crush. PA mRNA levels were also increased at the crush site, with uPA mRNA elevated by 8 hr after crush and tPA and uPAR mRNA levels markedly increased by 7 d. PA-dependent enzymatic activity was significantly increased from 1 to 7 d after crush in nerves that had been crushed compared with uncrushed nerves. Immunohistochemistry showed that tPA was localized within regenerating axons of the sciatic nerve. There were no significant changes in plasminogen activator inhibitor 1 activity between crush and sham after the injury. These results clearly demonstrated that after injury the PA system was rapidly induced in sensory neurons, where it may play an important role in nerve regeneration in vivo.

Plasminogen activator inhibitor-1 in acute hyperoxic mouse lung injury

Hyperoxia-induced lung disease is associated with prominent intraalveolar fibrin deposition. Fibrin turnover is tightly regulated by the concerted action of proteases and antiproteases, and inhibition of plasmin-mediated proteolysis could account for fibrin accumulation in lung alveoli. We show here that lungs of mice exposed to hyperoxia overproduce plasminogen activator inhibitor-1 (PAI-1), and that PAI-1 upregulation impairs fibrinolytic activity in the alveolar compartment. To explore whether increased PAI-1 production is a causal or only a correlative event for impaired intraalveolar fibrinolysis and the development of hyaline membrane disease, we studied mice genetically deficient in PAI-1. We found that these mice fail to develop intraalveolar fibrin deposits in response to hyperoxia and that they are more resistant to the lethal effects of hyperoxic stress. These observations provide clear and novel evidence for the pathogenic contribution of PAI-1 in the development of hyaline membrane disease. They identify PAI-1 as a major deleterious mediator of hyperoxic lung injury.

Modulation of adhesive properties of DEAE-dextran with laminin

Human squamous epithelial cells produce lower amounts of laminin and fibronectin when cultured on DEAE-dextran than when cultured on gelatin-coated polystyrene (Biotechnol. Bioeng., 33:1235). The epithelial cells also spread much more slowly on DEAE-dextran than they do on gelatin-coated polystyrene. To determine if the low level of matrix production by cells grown on DEAE-dextran contributed to the slowness of cell spreading on this substrate, microcarriers made from DEAE-dextran were treated with exogenous laminin (10 micrograms/cm2 of surface area) and then examined for ability to support cell adhesion. Squamous epithelial cells spread as rapidly on the laminin-treated DEAE-dextran as they did on gelatin-coated polystyrene (much more rapidly than on untreated DEAE-dextran). This indicates 1) that laminin can bind to DEAE-dextran in a fashion that is biologically usable by anchorage-dependent cells, and 2) that when laminin is bound to DEAE-dextran, the failure of squamous epithelial cells to rapidly spread is overcome. These data support the hypothesis that failure of the cells to synthesize an intact extracellular matrix on DEAE-dextran is responsible, at least in part, for the slowness with which cells spread on this substrate.