Introduction: The passage of inflammatory cells from the systemic circulation into tissue via transendothelial migration is a vital step in the mammalian inflammatory response. In instances of inappropriate activation of the immune system, prevention of cell trafficking is an attractive target for the design of potential anti-inflammatory therapies.

Heparanase is an endoglycosidase that preferentially degrades heparan sulphate proteoglycans. These proteoglycans are found on the surface of vascular endothelium and throughout the extracellular matrix and are involved in regulation of cell trafficking. Heparanase is initially transcribed as an inactive pro-enzyme which requires cleavage and processing into an active dimer (Fairbanks et al., 1999).

The human heparanase enzyme has been shown to play a role in tumour cell (Uno et al., 2001) and T-cell (Lider et al., 1990) migration. Therefore, we have explored the effects of exogenous active (HPA) and pro- (pro-HPA) heparanase in an in vivo rodent model of peritoneal inflammation.

Methods: Male Sprague-dawley rats (200g, n=6 per group) were treated by intra peritoneal injection with vehicle (saline, 1ml), IL-1ß (20ng), human recombinant HPA (10µg), pro-HPA (10µg) or a combination of the above. Animals were then monitored for 4h before being killed by CO₂ exposure and cervical dislocation. 20ml of saline were then injected into the peritoneal cavity and the area gently massaged for 1 minute. 10ml of lavage fluid was recovered from the opened peritoneal cavity and centrifuged for 5 minutes at 200 x g. Cell pellets were then resuspended in 10ml of modified Hank's balanced salts solution. Total cell numbers from each sample were determined by counting in a haemocytometer. In addition to this, Diff-Quik^TM stained cytospin preparations were used for differential cell counting.

Results: All data were analysed using Dunnett's multiple comparison test. IL-1ß caused a significant increase in peritoneal cell recruitment (1.12 x 10⁶ ± 28.6 x 10³ vs. 28.4 x 10⁵± 4.3 x 10³ total cells, IL-1 vs saline, p<0.05) comprising mainly neutrophils (55% ±2%). Both HPA and Pro-HPA also caused a significant increase in total peritoneal cell number (98.6 x 10 ⁵ ± 26.7 x 10 ³ and 1.62 x 10 6 ± 1.4 x 10 3, respectively, p<0.05). These infiltrates consisted largely of mononuclear cells in both instances, although a significant (p<0.05) increase in neutrophil numbers was also observed, compared to saline treated animals (34.1% and 26.5% for HPA and Pro-HPA respectively vs. 4.6% for saline). Co-administration of IL-1ß with either HPA or Pro-HPA did not further augment the inflammatory response seen in response to IL-1ß alone, nor did the cellular composition of the inflammatory infiltrate change significantly from that observed in IL-1ß treated animals.Conclusions: These data suggest a role for mammalian heparanase in cell infiltration and inflammation. Also, they support the possible inhibition of heparanase as a therapeutic target for inflammatory conditions.

Fairbanks et al. (1999) J. Biol. Chem. 274 : 29587-29590.
Lider et al. (1990) Eur. Journal Immunol. 20 : 7855-7860.
Uno et al. (2001) Cancer Res. 61 : 7855-7860.