Interactions between connective tissue matrix macromolecules

Sellar repair with fibrin sealant and collagen fleece after endoscopic endonasal transsphenoidal surgery

OBJECTIVE

To determine, in patients undergoing sellar repair after endoscopic endonasal transsphenoidal surgery, the clinical efficacy of a combination of fibrin sealant/collagen fleece compared to the use of fibrin sealant or collagen fleece alone, in preventing CSF-related (cerebrospinal fluid) postoperative complications.

METHODS

From a retrospective analysis of our series of 242 consecutive endoscopic transsphenoidal procedures, in 56 out of the 90 cases in which the sella had been repaired, fibrin sealant and/or collagen fleece was employed, both in combination with one or multiple layers of other materials. The incidence of postoperative CSF leaks and the need for a postoperative lumbar drainage in the groups of fibrin sealant or collagen fleece treated patients were compared to the group of patients treated with the fibrin sealant/collagen fleece combination.

RESULTS

In 2 out of 16 fibrin sealant treated patients a postoperative CSF leak presented, and in 6 out of these 16 subjects a postoperative lumbar drainage was necessary; patients who received a fibrin sealant/collagen fleece combination exhibited no detectable postoperative CSF leak, and no postoperative lumbar drainage was used.

CONCLUSIONS

Closure of the sella turcica with fibrin sealant in combination with a collagen fleece is a safe and effective method to prevent CSF fistulas. When used in combination, the collagen fleece enhances the sealing and tissue regeneration properties of the fibrin sealant, thus reducing the incidence of postoperative CSF leaks, obviating the need for a lumbar drain placement.

Enhanced invasive properties exhibited by smooth muscle cells are associated with elevated production of MMP-2 in patients with aortic aneurysms

BACKGROUND

abdominal aortic aneurysms (AAA) are associated with excessive vascular matrix remodelling. Recent findings suggest a systemic overproduction of matrix metalloproteinases-2 (MMP-2) by vascular smooth muscle cells (SMC) may be pivotal aetiologically. SMC migration is facilitated by MMP mediated proteolysis of the basement membrane and extracellular matrix. Our aim was to see if enhanced MMP-2 production by these SMC exhibit increased invasion, in an in vitro model of migration.

METHOD

SMC were derived from inferior mesenteric vein (IMV) harvested from patients undergoing aneurysm repair (n=6) or colectomy for diverticulosis (n=6, control). Using a modified Boyden chamber chemotaxis was measured towards platelet derived growth factor (PDGF) and foetal calf serum (FCS) and invasion through a Matrigel layer. MMP-2 production was quantified by ELISA and gelatin zymography.

RESULTS

chemoattractant studies demonstrated no difference in the effect of PDGF or FCS between the two populations of SMC. However, invasive studies demonstrated a significant increase in the number of migrating SMC isolated from IMV of AAA patients. Analysis of culture media extracts revealed that this difference was associated with a significant increase in production of MMP-2.

CONCLUSION

SMC derived from patients with AAA demonstrate increased invasive properties when compared to a control group. Increased migration appears to be due to overproduction of MMP-2. The enhanced migratory potential of these SMC may lead to extracellular matrix remodelling and subsequent medial disruption demonstrated in the aneurysmal aorta. These data further support evidence of the proteolytic role of MMP-2 in cell migration.

Changes in the cervical extracellular matrix during pregnancy and parturition

The key function of the uterine cervix to maintain pregnancy is biochemically characterized by an increased synthesis of proteins (e.g., collagen), proteoglycans, and glycoproteins (e.g., fibronectin) as well as by defined interactions between these components of the extracellular matrix. In contrast to the slow phase of the cervical ripening process in late pregnancy, cervical dilatation during parturition requires the rapid production and action of catabolic enzymes leading mainly to collagen degradation and changes in its architecture but also to degradation of other fundamental matrix proteins. Evidence suggests that an increased production of TNF-alpha and IL-1 beta, e.g., induces a rise in the expression of endothelial adhesion molecules with subsequent extravasation of neutrophils into the cervical stroma and that the chemotaxis and degranulation of these cells is triggered by an increased concentration of IL-8. Rising concentrations of hyaluronan at this time have been considered as potent inducers of IL-1 beta and TNF-alpha synthesis by various leukocyte populations. The increase in IL-6 synthesis stimulates prostaglandin and leukotriene production causing dilatation of cervical vessels and further promoting the extravasation of leukocytes. The proteases released after degranulation of neutrophils encounter an already destabilized collagenous fiber network. Since a sustained action of proteases may lead to severe tissue damage, this process is strictly limited in time and is controlled by increasing concentrations of tissue inhibitors of protease in the lower uterine segment immediately after delivery. The clinical consequences of this basic research is to develop new concepts in a more causal treatment of cervical pathology during pregnancy and parturition.

Clinical evaluation of the use of citric acid and autologous fibronectin in periodontal surgery

This study evaluated the effects of citric acid demineralization and autologous fibronectin application in association with a modified Widman flap in the treatment of periodontitis. The study population comprised 29 patients under treatment for moderate to advanced periodontitis who reached the one-year posttherapy evaluation. After thorough scaling and root planing, a split mouth design was used in which two quadrants were treated by modified Widman flap alone, and the other two randomly assigned quadrants were treated by modified Widman flap combined with citric acid demineralization and autologous fibronectin application. Fibronectin, which had previously been isolated from the patient's own plasma, was applied with a tuberculin syringe on the citric acid demineralized root surfaces and the inner aspect of the flap. After suturing provided good flap adaptation, additional fibronectin was again applied under the flap and external pressure was applied. Patients were clinically evaluated at baseline and at one year. Statistical evaluation of the data using paired t test and Chi-square analysis indicated that both approaches, modified Widman flap alone or in combination with citric acid and fibronectin, significantly reduced probing pocket depth and increased clinical attachment. However, the changes achieved with citric acid and fibronectin were statistically greater than those obtained with the flap alone. Furthermore, the number of sites gaining 2 mm or more of clinical attachment were significantly increased. The results suggest that the use of citric acid and fibronectin holds promise in promoting reattachment after periodontal therapy.

Effect of citric acid and various concentrations of fibronectin on healing following periodontal flap surgery in dogs

The purpose of this histologic and histometric study was to examine the effect of citric acid and increasing concentrations of fibronectin on new connective tissue attachment following periodontal flap surgery. Full thickness, mucoperiosteal flaps were elevated in six healthy mongrel dogs. Two to 3 mm of alveolar bone were removed along the buccal aspect of the teeth in the mandible and into the interproximal areas of each surgical site. Cementum was removed from the exposed root surfaces and reference notches were inscribed into the roots at the margin of the recontoured bone. Citric acid, pH 1.0, was applied to the instrumented root surfaces for 3 minutes and rinsed with sterile saline. Both the root surfaces and the inner surface of the flap were then bathed in either sterile saline or increasing concentrations (0.38, 0.75 and 1.5 mg/ml saline) or exogenous fibronectin. All the flaps were returned to their original preoperative positions, secured using figure 8 sutures with 4-0 braided silk and allowed to heal. Two dogs per time-point were sacrificed at 1, 2 and 6 weeks after surgery. Block specimens of the surgical sites were demineralized and serial sections prepared for histologic and histometric evaluations. Histologically, tissue sections were examined for: (1) epithelial proliferation and attachment, (2) periodontal fiber organization and maturation, (3) inflammatory cell types, (4) presence or absence of new cementum deposition and (5) degree of vascularity of the tissues. Histometric measurements were taken: (1) from the root surface notch to the apical extent of the junctional epithelium and (2) from the apical extent of the junctional epithelium to the free gingival margin.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell proliferation after flap surgery, root conditioning and fibronectin application

This study evaluated the effects of citric acid demineralization and autologous fibronectin application on cell proliferation after mucoperiosteal flap surgery. Three adult rhesus monkeys were used. After flaps were raised, the roots were surgically exposed and planed. Surfaces on the experimental sides were decalcified with citric acid, and after thorough rinsing, the inner aspect of the flaps and the roots were bathed with 1 ml of autologous plasma fibronectin in normal saline (400 micrograms m/ml) and the flaps sutured. Contralateral teeth, acting as controls, were treated only with the surgical procedure. One hour prior to sacrifice, the animals were injected with an intravenous injection of tritiated thymidine (1 microCi/gm body weight). Surgeries were staggered to produce the following time periods: 3, 7, 15, 21 and 28 days. After processing, autoradiographs were obtained for evaluation, and labeled cells were counted in five compartments at 400 x: (1) oral epithelium, (2) crevicular area, (3) supracrestal connective tissue, (4) coronal periodontal membrane and (5) coronal bone marrow. Forty tissue sections per procedure (20 slides per tooth) were counted and means obtained for the three monkeys. Differences between experimental and control values were statistically evaluated for each component, at each time interval, using pairwise t tests. Fibronectin-treated areas showed significantly increased cellular proliferation (P less than 0.01) during the first 2 weeks, affecting mainly all the supracrestal tissues. Histologically, the establishment of a well-organized fibrinous clot at 3 days was noted in these areas. Results show a faster healing after surgery with the use of citric acid and fibronectin. It was concluded that citric acid followed by fibronectin enhanced cellular proliferation.

The effect of fibronectin therapy and fibronectin deficiency on healing of rat burns and excision wounds

Rats with standardized burns and skin excision wounds were treated i.p. with human fibronectin or swine skin gelatin. Controls received bovine albumin, solvent, or no treatment. Wound healing was assessed by planimetry, additionally plasma fibronectin was determined. Solvent or albumin did not influence the healing process, neither did fibronectin. However, when opsonizing fibronectin was additionally consumed by application of gelatin, a significant retardation of wound healing was observed. The results support the opinion that fibronectin is of essential importance for posttraumatic opsonization of gelatin-like material originating from the damaged tissue.

Masking of antigenic sites of fibronectin by glycosaminoglycans in ethanol-fixed embryonic tissue

We studied the interaction between glycosaminoglycans (GAGs) and fibronectin in the basement membrane of the epiblast in the chicken blastoderm using testicular-hyaluronidase digestion of GAGs either on fixed tissue sections or in vivo after microinjection of the enzyme preparation prior to immunostaining for fibronectin. In the choice of fixatives, special attention was paid to their preservation of GAGs. The controls included alcian-blue staining of serial sections to test the efficiency of the digestion, and incubations in the presence of protease inhibitors to abolish contaminating proteolytic activity in the commercial hyaluronidase preparations. The results indicate that fixation in solutions which preserve GAGs, i.e. ethanolic solutions or aqueous solutions containing cetylpyridinium chloride, allows the immunocytochemical demonstration of fibronectin in the basement membrane of the epiblast at the level of the endophyllic crescent, but masks this glycoprotein at the epithelial-mesenchymal interface. As shown by both approaches, this masking of immunoreactivity is reversible. Moreover, the in vivo clearance of GAGs before fixation shows that the masking at the epithelial-mesenchymal interface is not an experimental peculiarity due to the use of a particular technique, but is the consequence of an interaction between GAGs and fibronectin in that particular area of the basement membrane that is used by mesoblast cells as a substrate for migration. The observation that fibronectin may be masked by GAGs in ethanol-fixed tissue--a commonly used fixation method--may require the re-evaluation of some negative results mentioned in the literature.

Alkaline phosphatase binds to collagen; a hypothesis on the mechanism of extravesicular mineralization in epiphyseal cartilage

Affinity chromatography on Sepharose 4B-collagen gels was used to test the affinity of alkaline phosphatase for collagen. Results indicate that alkaline phosphatase of preosseous cartilage binds to collagen probably by electrostatic interactions, this interaction is inhibited by proteoglycan subunits. These results suggest that, in vivo, the formation of a collagen-alkaline phosphatase complex may be a step of the process leading to cartilage calcification.

Monoclonal antibodies to laminin reveal the heterogeneity of basement membranes in the developing and adult mouse tissues

Two monoclonal antibodies raised against laminin isolated from a mouse parietal yolk sac cell line were used for immunohistochemical studies of basement membranes of the mouse embryo and various fetal and adult tissues. No immunoreactivity with either of the two monoclonal antibodies could be detected in the preimplantation-stage embryos, although it has been shown that these embryos contain extracellular laminin reactive with the conventional polyclonal antilaminin antibodies. Reichert's membrane in early postimplantation stages of development reacted with the monoclonal antibody LAM-I but not with the antibody LAM-II. However, from day 8 of pregnancy onward the Reichert's membrane reacted with both antibodies. Basement membranes of the embryo proper were unreactive with both monoclonal antibodies until day 12 of pregnancy. By day 14 some basement membranes of the fetal tissues became reactive with one or both monoclonal antibodies, whereas others remained still unreactive. In the 17-d fetus and the newborn mouse most of the basement membranes reacted with both monoclonal antibodies, whereas others still reacted with only one. Similar heterogeneity in the immunoreactivity of basement membranes of various tissues was noted in the adult mouse as well. These results indicate that the immunoreactivity of laminin in the extracellular matrix changes during development and that the basement membranes in various anatomic locations display heterogeneity even in the adult mouse.