Levels and molecular forms of MMP‐7 (matrilysin‐1) and MMP‐8 (collagenase‐2) in diseased human peri‐implant sulcular fluid
Authors: Kivelä‐Rajamäki Marjo , Maisi Päivi , Srinivas Ravi , Tervahartiala Taina , Teronen Olli , Husa Ville , Salo Tuula , Sorsa Timo 
Published: November 2003

Objectives:  Matrix metalloproteinases (MMPs) play crucial role in various tissue destructive inflammatory processes by degrading almost all peri‐cellular and basement membrane components. MMP‐8 (collagenase‐2) is the major MMP in periodontitis. MMP‐7 (matrilysin‐1), in addition to its ability to degrade matrix and basement membrane components, activates other latent pro‐MMPs and defensins, host cell‐derived antimicrobial cryptidins. The aim of the present study was to characterize the relationship, levels and molecular forms of MMP‐8 and MMP‐7 in diseased peri‐implant sulcular fluid (PISF).

Materials and methods:  Seventy‐two human dental implant fluid samples were collected with filter paper strips from peri‐implant sulci from healthy and untreated diseased implant sites. Gingival index (GI) and/or bone resorption (BR) were also recorded. Western immunoblot method with polyclonal anti‐human‐MMP‐8 and monoclonal anti‐human‐MMP‐7 antibodies was used, and immunoreactivities were quantified with computer scanning program. The effects of MMP inhibitors (doxycycline, chemically modified tetracycline‐3, clodronate, CTT‐peptide and marimastat) were studied on the activity of recombinant human matrilysin‐1 (MMP‐7) using β‐casein degradation assay.

Results:  The levels of active forms of MMP‐8 and MMP‐7 were significantly elevated in diseased PISF in relation to healthy PISF. Furthermore, MMP‐8 and MMP‐7 levels correlated significantly to each other and GI. MMP‐8 was present not only as bands corresponding to 75‐kDa polymorphonuclear leukocyte (PMN) ‐type pro‐ and 65‐kDa active forms, but also as 55‐kDa non‐PMN‐type pro‐ and 45‐kDa active forms. Immunoreactivities > 80 kDa most likely represented dimeric and/or inhibitor‐bound MMP‐8 complexes and the low molecular weight (< 30 kDa) species were apparently degraded fragments. In diseased PISF, 19–21‐kDa active MMP‐7 and 28–30‐kDa pro‐MMP‐7 species were detected, and the active 19–21‐kDa forms of MMP‐7 predominated in diseased PISF. Doxycycline (50 µm and 250 µm), chemically modified non‐antimicrobial tetracycline (CMT‐3) (50 µm and 100 µm), clodronate (a bisphosphonate, 20 µm and 500 µm) and the cyclic CTT (CTTHWGFTLC)‐peptide (125 µm and 250 µm), all known broad‐spectrum or selective MMP‐inhibitors, did not inhibit the activity of human recombinant MMP‐7; only marimastat (1 µm and 5 µm) inhibited MMP‐7.

Discussion:  Increased immunoreactivities of the active MMP‐8 and MMP‐7 species in PISF from diseased peri‐implantitis lesions eventually reflect the stage and course of peri‐implantitis; MMP‐7 may potentially act as MMP‐8 and defensin activator in diseased PISF.

Conclusion:  The elevated levels of MMP‐8 and matrilysin‐1/MMP‐7 were identified in active forms in diseased PISF, but MMP‐7 was less prominent. MMP inhibitors, potential future tissue protective drugs, seemingly do not interfere with the defensive antibacterial action of MMP‐7.