Increasing expression of tissue plasminogen activator and plasminogen activator inhibitor type 2 in dog gingival tissues with progressive inflammation

Urokinase and tissue-type plasminogen activators (u-PA and t-PA) are serine proteases that convert plasminogen into plasmin, which degrades matrix pro teins and activates metalloproteinases. The PAs are balanced by specific in hibitors (PAI-1 and PAI-2). Local production of t-PA and PAI-2 was recently demonstrated in human gingival tissues. The aim now was to investigate the production; and localization of t-PA and PAI-2 in gingival tissues from do gs in three well-defined periodontal conditions; clinically healthy gingiva , chronic gingivitis and an initial stage of ligature-induced loss of attac hment. At the start of the experiment the gingiva showed clear signs of inf lammation. Clinically healthy gingiva were obtained after 21 days period of intense oral hygiene. Attachment loss was induced by placing rubber ligatu res around the neck of some teeth. Biopsies were taken from areas represent ing the different conditions and prepared for in situ hybridization and imm unohistochemistry. In clinically healthy gingiva both t-PA mRNA and antigen were expressed in a thin outer layer of the sulcular and junctional epithe lia. No t-PA signals or staining were seen in connective tissue. Both mRNA signaling and immunostaining for t-PA were stronger in chronic gingivitis. In areas with loss of attachment, t-PA mRNA as well as antigen were found i n the sulcular and junctional epithelia to a similar degree as in gingiviti s. Occasionally the connective tissue was involved, especially in connectio n with vessels. PAI-2 mRNA was seen in a thin outer layer of the sulcular a nd junctional epithelia in clinically healthy gingiva, but no signals were seen in connective tissue. PAI-2 antigen was found primarily in the outer l ayer of the sulcular and junctional epithelia. Some cells in the connective tissue were stained. In gingvitis, PAI-2 signals were mainly found in the same locations, but more intense and extending towards the connective tissu e. Immunostaining was seen in the outer half of the sulcular and junctional epithelia as well as in the upper part of the connective tissue, close to the sulcular epithelium. In sites with loss of attachment, PAI-2 mRNA was f ound throughout the sulcular and junctional epithelia, as was the antigen, which stained intensely. No PAI-2 mRNA was seen in connective tissue; the a ntigen was found scattered, especially near vessels. This study shows that the expression of both t-PA and PAI-2 increases with experimental gingival inflammation in the dog, and furthermore, the two techniques demonstrate a strong correlation between the topographical distribution of the site of pr otein synthesis and the tissue location of the antigens for both t-PA and P AI-2. The distribution correlates well with previous findings in humans. (C ) 2000 Elsevier Science Ltd. All rights reserved.