The high affinity heparin-binding domain and the V region of fibronectin mediate invasion of human oral squamous cell carcinoma cells in vitro

Fibronectin is an extracellular matrix molecule composed of repeating subunits that create functional domains. These domains contain multiple binding sites for heparin and for various cell-surface receptors that modulate cell function. To examine the role that the high affinity heparin-binding region and the alternatively spliced V region of fibronectin play in tumor invasion, we expressed and purified four complementary recombinant fibronectin proteins. These proteins either included or excluded the alternatively spliced V region and contained either a mutated, non-functional high affinity heparin-binding domain (Hep-) or an unmutated heparin-binding domain (Hep+). Cultured oral squamous cell carcinoma cells were assayed for invasion into a Matrigel/collagen matrix supplemented with these four purified recombinant proteins, and for spreading and motility on plastic. Increased invasion was observed in gels supplemented with the V-Hep+ protein when compared with the V-Hep- protein. Inclusion of the V region in the proteins enhanced the invasion and migration associated with both Hep+ and Hep- proteins, whereas cell spreading was enhanced with the Hep+ recombinant proteins. These data demonstrate that both the high affinity heparin-binding domain and the V region of fibronectin play important roles in invasion, motility, and spreading of oral squamous cell carcinoma cells.

Cocaine-associated rapid gingival recession and dental erosion. A case report

This case report chronicles the clinical presentation and unusual response to treatment of a patient with rapid gingival recession and dental erosion secondary to local cocaine application. The initial clinical diagnosis was necrotizing ulcerative periodontitis; only after several years of therapy did the patient voluntarily inform one of the therapists that cocaine had been regularly applied to the affected gingival sites. This case illustrates the importance of including cocaine application to gingival tissues in a differential diagnosis in cases of rapid gingival recession and dental erosion of unknown etiology.

Fibronectin and fibronectin fragments modulate the expression of proteinases and proteinase inhibitors in human periodontal ligament cells

Fragments of the matrix molecule fibronectin (FN) have been shown to modulate tissue remodeling activity by inducing matrix metalloproteinases (MMPs) in synovial fibroblasts. These molecules could contribute to the tissue degradation that occurs during periodontal disease if they also modulate the expression of proteinases in cells of the periodontal ligament (PDL). We tested the hypothesis that FN and specific FN fragments induce the expression of specific proteinases in PDL cells. Using substrate zymograms, reverse zymograms and Western immunoblots, we found that PDL cells constitutively express 72 kDa gelatinase, urokinase-type plasminogen activator (uPA) and at least three inhibitors whose molecular masses correspond to those of the tissue inhibitors of metalloproteinases (TIMPs). A fourth, previously uncharacterized, proteinase inhibitor of approximately 22 kDa was also observed in some cell isolates. PDL cells, when exposed to a 120 kDa proteolytic FN fragment containing the cell-binding domain, were induced to express collagenase and stromelysin and also demonstrated an increased secretion of the serine proteinase uPA. Expression of collagenase increased with increasing concentrations (0.001 microM-1 microM) of the 120 kDa FN fragment. This fragment also induced the expression of a 20 kDa inhibitor, but not of the higher-molecular-mass inhibitors, in PDL cells. The observed alterations in proteinases were associated specifically with the 120 kDa FN fragment, since similar responses were not seen when PDL cells were exposed to either a 60 kDa heparin-binding FN fragment or a 45 kDa collagen/gelatin-binding FN fragment. PDL cells exposed to intact FN did not express the proteinases induced by the 120 kDa fragment but did express 92 kDa gelatinase and the 20 kDa proteinase inhibitor. These data suggest that FN and specific FN fragments can differentially induce the expression of proteinases in PDL cells. Thus, functional regions of FN may modulate many of the functions of PDL cells that contribute to periodontal disease, wound healing and maintenance of extracellular matrix in periodontal tissues.