Hepatocyte growth factor : Studies on local and systemic release and effects during infectious disease; in vivo and in vitro

Abstract: The interaction of mesenchymal and epithelial cells that occurs after organ injuries results in enhanced production of cytokines, such as hepatocyte growth factor (HGF). HGF is a glycoprotein with unique properties that contribute to wound healing after injuries. In the present thesis, the release and role of HGF during infectious diseases have been investigated with particular emphasis on pneumonia and meningitis. First, a standard method for serum handling of HGF was determined. It was shown that HGF was stable in the serum after separation and several freeze-thaw cycles, keeping at room temperature for several hours or storage at -70 °C for several months, shaking or adding heparin and albumin did not affect HGF levels in serum. However, for reliable results whole blood had to be separated within one hour after venipuncture at room temperature or kept at 4-8 °C in the case of longer storage before separation. Following this standard method, the concentration of HGF during infectious diseases was studied. In another study we had previously shown that levels of HGF in serum increased during the acute phase of several infectious diseases. In this thesis a simultaneous enhanced production of HGF locally at the site of injury was studied. It was shown that concentration of HGF increased locally in cerebrospinal fluid during meningitis. Levels of HGF were significantly higher during bacterial meningitis than viral meningitis and concentration of HGF in cerebrospinal fluid might be used as a tool in diagnosis of bacterial meningitis. It was shown an enhanced local production of HGF in exhaled breath condensate in pneumonia that did not decrease significantly after 4 weeks in spite of the fact that the patient had recovered clinically and in the X-ray controls. This might show a long repair and healing process after pneumonia. Serum levels of HGF were significantly higher in pneumonia caused by Streptococcus pneumoniae than in other causes of pneumonia. In pneumonia, serum levels ofHGF decreased within 48 hours after efficient antibiotic therapy was started and normalized at convalescence. However, the levels of HGF in serum increased when treatment was ineffective and no clinical improvement was observed. When the appropriate therapy was initiated, the levels of HGF decreased followed by clinical recovery. Serum levels of HGF were able to predict therapy results at least as reliably as CRP within 48 hours after treatment. Thus HGF was shown to be a diagnostic moment for acute bacterial infections, and following levels of HGF in serum may perhaps be used as a prognostic marker in the course of treatment of infectious diseases such as pneumonia. The physiological effects of HGF on chronic leg ulcers(> 1 år) in 11 elderly patients were studied and an enhanced microcirculation that was significantly correlated to the healing percentage was observed after local HGF treatment. The infected ulcers that received a combined treatment of HGF and appropriate antibiotic responded with a high percentage of healing in three patients with chronic leg ulcers that had not responded to other treatments (including antibiotics) previously. The effect of HGF on injured mouse melanoma cell monolayer was investigated in vitro and showed that HGF caused migration of neighbouring cells towards the nude injured area in a dose-dependent manner. Concomitant morphogenic effects were observed. The actin structure in the cytoskeleton was changed by HGF treatment as studied by confocal microscopy. According to these results it could be cocluded that injuries caused by infectious organisms enhance the local and systemic production of HGF. This might be beneficial in healing of damage after such injuries. Determination of natural HGF in serum might be used as a diagnostic and prognostic marker during infectious diseases. Exogenous administration of recombinant HGF could be a beneficial treatment for injuries such as chronic leg ulcers particularly combined with the appropriate antibiotic in the case of obvious infection.