Isolation and partial sequencing of potentially odontoblast-specific/enriched rat cDNA clones obtained by suppression subtractive hybridization

Odontoblasts, which are responsible for dentine formation, are known to synthesize unique gene products such as dentine sialophosphoprotein. To further identify and clone novel odontoblast-specific genes, a suppression subtractive hybridization technique was used here. Differentially or predominantly expressed cDNAs in odontoblasts of rat incisors were obtained by subtracting the common cDNAs expressed in odontoblasts, osteoblasts and pulp cells. Clones were then partially sequenced and analysed for nucleotide sequence homology by the basic local alignment search tool program. From a total of 1290 clones analysed, 538 odontoblast-enriched clones were identified in the subtracted cDNA library. Out of 538 clones, 498 clones (92.6%) demonstrated high identity with genes in the GenBank database. In contrast, 31 clones (5.7%) showed low sequence identity with known genes, among which 18 clones (3.3%) were observed more than once, thereby possibly representing odontoblast-specific/enriched genes. The majority (390 clones; 72.5%) of the clones with high homology to known genes were found to be the rat/mouse dentine sialophosphate by dot-blot analysis (326 clones) and sequencing (64 clones). The second highest enrichment (39 clones) was for phosphate-regulating gene with homology to endopeptidase on the X-chromosome, which codes for a neutral endopeptidase. After suppression subtractive hybridization, several cDNAs that are commonly present in osteoblasts and odontoblasts appeared unsuppressed. Therefore, a rat odontoblast-specific/enriched subtraction cDNA library has been created from which a number of potentially novel genes for odontoblasts could be identified.

Down-regulation of osteoblastic cell differentiation by epidermal growth factor receptor

The role of epidermal growth factor receptors (EGF-R) in osteogenic cell differentiation was investigated using preosteoblastic MC3T3-E1 (MC3T3) cells and osteoblast-like ROS 17/2.8 (ROS) cells. When cultured in the presence of beta-glycerophosphate (GP) and ascorbic acid (AA), MC3T3 cells underwent spontaneous differentiation into osteoblasts which was confirmed as they expressed osteoblast markers such as alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteocalcin (OC). Interestingly, the number of EGF-binding sites decreased during their differentiation into osteoblasts, and the osteogenic protein-1 (OP-1) treatment, which accelerated their differentiation, lowered the number of EGF-binding sites even further. On the other hand, ROS cells with high expression levels of osteoblast markers and no EGF-R, after being transfected with human EGF-R cDNA (EROS cells), expressed numerous EGF-binding sites as well as EGF-R mRNA and protein; in the process, they ceased to express osteoblast markers, indicating their dedifferentiation into osteoprogenitor cells. Both MC3T3 and EROS cells showed increased cell growth in response to EGF, whereas ROS cells did not. These results imply that the EGF/EGF-R system in osteogenic cells has a crucial function in osteoblast phenotype suppression and osteogenic cell proliferation.

N-cadherin expression during periodontal ligament cell differentiation in vitro

BACKGROUND

When confluent periodontal ligament (PDL) cells were cultured in the presence of dexamethasone (Dex), ascorbic acid (AA), and beta-glycerophosphate (GP), they underwent sequential differentiation, demonstrating distinct morphological characteristics. At 1 week, localized cell proliferation led to the formation of multilayers of cells. As cell differentiation progressed, they formed nodules by deposition of matrix in the clusters of cells at 2 weeks, and mineralized the nodules at 3 weeks. These changes implicate extensive cell-to-cell interactions. Cadherins are known to play an important role in establishing cell contacts during tissue formation.

METHODS

To determine whether cadherins are involved in PDL cell differentiation, and the formation and mineralization of nodules by the cells in vitro, we investigated the expression of N-cadherin using immunofluorescence labeling and Northern blot analysis.

RESULTS

Immunolabeling showed that N-cadherin was expressed in PDL cells in the stages of nodule formation and mineralization. Northern blot analysis demonstrated a 3-fold increase in the expression of N-cadherin mRNA in the stages. However, neither E-cadherin nor P-cadherin was expressed.

CONCLUSIONS

Our data suggest that N-cadherin may play an important role in PDL cell differentiation and the formation of mineralized nodules by PDL cells.

Expression of TGF-beta isoforms and their receptors during mineralized nodule formation by rat periodontal ligament cells in vitro

Transforming growth factor-betas (TGF-beta s) and bone morphogenetic proteins (BMPs), members of a TGF-beta superfamily, are known to play an important role in osteogenic cell differentiation and consequently bone formation. We have reported previously that periodontal ligament (PDL) cells differentiate and form mineralized nodules when cultured in the presence of dexamethasone (Dex), beta-glycerophosphate (GP) and ascorbic acid (AA). To understand the roles of TGF-beta isoforms (TGF-beta 1, 2 and 3) and TGF-beta type I receptors (activin receptor-like kinase (ALK)-2, -3, -5 and -6) in PDL cell differentiation, their expression was investigated using Northern blot analysis. Rat PDL cells, derived from coagulum in the tooth socket, were cultured in the presence of Dex (5 microM), GP (10 mM) and AA (50 micrograms/ml) for up to 21 d. Total RNA was isolated from PDL cells after 0, 7, 14 and 21 d and used for northern blot analysis of mRNAs for matrix proteins, TGF-beta isoforms and their receptors using 32P-labeled cDNAs as probes. Four stages showing distinct morphological characteristics and matrix expression during development of mineralized nodules were identified. Type I collagen (Col I) and SPARC (secreted protein, acidic and rich in cysteine) mRNAs were expressed at the confluent stage, but decreased during the mineralization stage. Osteopontin (OPN) and alkaline phosphatase (ALP) transcripts were initially observed at multilayer stage, while bone sialoprotein (BSP) and osteocalcin (OC) at the nodule stage and all 4 were expressed thereafter. TGF-beta 1 mRNA expression increased with the progression of PDL cell differentiation, while a relatively high level of TGF-beta 3 transcript decreased slightly during their differentiation. TGF-beta 2 mRNA was not expressed. The expression of TGF beta-RI mRNA decreased, whereas that of TGF beta-RIII increased dramatically with PDL cell differentiation. TGF beta-RII gene activities remained high throughout all stages. ALK-2, ALK-3 and ALK-6 mRNA expression increased with the progression of PDL cell differentiation, suggesting that these receptors may play important roles in Dex-induced PDL cell differentiation and mineralized nodule formation.

Melatonin promotes osteoblast differentiation and bone formation

Prior studies have demonstrated that the pineal hormone, melatonin, can stimulate chloramphenicol acetyltransferase activity in Drosophila SL-3 cells transfected with a chloramphenicol acetyltransferase reporter construct containing the response element of rat bone sialoprotein (BSP). Based on these findings, studies were performed to determine whether melatonin could similarly modulate the expression of BSP in two cell lines, the MC3T3-E1(MC3T3) pre-osteoblast and rat osteoblast-like osteosarcoma 17/2.8 cell. Initial studies demonstrated that MC3T3 cells grown in the presence of 50 nM melatonin underwent cell differentiation and mineralization by day 12 instead of the 21-day period normally required for cells grown in untreated media. Melatonin increased gene expression of BSP and the other bone marker proteins, including alkaline phosphatase (ALP); osteopontin; secreted protein, acidic and rich in cysteine; and osteocalcin in MC3T3 cells in a concentration-dependent manner. Levels of melatonin as low as 10 nM were capable of stimulating transcription of these genes when cells were grown in the presence of beta-glycerophosphate and ascorbic acid. Under these conditions, melatonin induced gene expression of the bone marker proteins; however, this does not occur until the 5th day after seeding the culture dishes. Thereafter, MC3T3 cells responded to melatonin within 2 h of treatment. The fully differentiated rat osteoblast-like osteosarcoma 17/2.8 cells responded rapidly to melatonin and displayed an increase in the expression of BSP, ALP, and osteocalcin genes within 1 h of exposure to the hormone. To determine whether melatonin-induced osteoblast differentiation and bone formation are mediated via the transmembrane receptor, MC3T3 cells were treated in the presence and absence of melatonin with either luzindole, a competitive inhibitor of the binding of melatonin to the transmembrane receptors, or pertussis toxin, an uncoupler of G(i) from adenylate cyclase. Both luzindole and pertussis toxin were shown to reduce melatonin-induced expression of BSP and ALP. These results demonstrate, for the first time, that the pineal hormone, melatonin, is capable of promoting osteoblast differentiation and mineralization of matrix in culture and suggest that this hormone may play an essential role in regulating bone growth.

Interleukin-1beta-induced release of matrix proteins into culture media causes inhibition of mineralization of nodules formed by periodontal ligament cells in vitro

The mechanism by which interleukin-1beta (IL-1) inhibits the formation of mineralized tissue nodules by periodontal ligament (PDL) cells in vitro was investigated through the processes of morphological analysis, immunoprecipitation, and Northern blot analysis. PDL cells were obtained from a 2-day-old coagulum in tooth socket and cultured in Dulbecco's Modified Eagle Medium (DMEM) containing 10% fetal bone serum (FBS) and antibiotics. Confluent cells were grown for up to 3 weeks in the presence of ascorbic acid (AA), beta-glycerophosphate (GP), and dexamethasone (Dex), or IL-1. PDL cells cultured in the presence of GP and AA did not differentiate, but those treated with Dex, GP, and AA (Dex group) underwent differentiation, showing four stages (confluent, multilayer, nodule, and mineralization) of disparate morphological characteristics. In contrast, the cells treated with IL-1, Dex, GP, and AA (IL-1 group) did form multilayers but failed to form mineralized nodules. Electron microscopy demonstrated that the Dex-induced mineralized nodules contain multilayers of fibroblastic cells, numerous collagen fibrils, and dense globular as well as fused electron dense patches that are associated with numerous apatite crystals. The nodule-like structures in the IL-1 group were also comprised of multilayered fibroblastic cells, but they contained only a small number of collagen fibrils, and no dense globular or fused patches. Von Kossa staining confirmed the presence of numerous mineralized nodules in the Dex group and their scarceness in the IL-1 group. Northern blot analysis of IL-1-treated cells, however, revealed the presence of mRNAs for type I collagen (Col I), secreted protein, acidic and rich in cysteine (SPARC), osteopontin (OPN), alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin (OC), whose expression patterns and levels were comparable to those of the Dex group. Immunoprecipitation analysis of OPN and BSP in the cell/matrix layers and the culture media after [35S]-methionine labeling showed their deposition primarily in the mineralized nodules of the Dex group, and their release into the media in the IL-1 group. Immunogold labeling demonstrated the location of OPN and BSP in mineralized nodules of the Dex group, but no significant labeling occurred in the nodule-like structures from the IL-1 group. Interestingly, IL-1 treatment increased the expression of collagenase mRNA by sevenfold, compared with that of the Dex group. These data suggest that the IL-1-induced formation of unmineralized nodules by PDL cells results not so much from the downregulated formation of matrix proteins, which plays a crucial role in the mineralization process, as from their release into the culture media. Finally, collagenase synthesis upregulated by IL-1 may be involved in this process.

Multiple colonization defects in a cysteine protease mutant of Porphyromonas gingivalis

A cysteine protease mutant, G-102, of Porphyromonas gingivalis 381 defective in the rgp-1 gene has been recently constructed in this laboratory. In order to evaluate the role of the protease in the virulence properties of P. gingivalis, a number of putative periodontopathic properties of the mutant were evaluated. Relative to the parental strain, mutant G-102 was demonstrated to be defective in interacting with Gram-positive bacteria as well as cultured epithelial cells. In addition, the mutant was altered in attaching to the protein components of extracellular matrix as well as to type I collagen. Some of these alterations could result from the decreased autoaggregation displayed by mutant G-102 relative to strain 381. However, since the epithelial cell attachment assays were carried out at very low bacterial densities, it is unlikely that reduced autoaggregation of the mutant is responsible for its decreased ability to attach to these eucaryotic cells. Electron microscopic examination of the cells also revealed that mutant G-102 was altered in normal fimbrae expression. In addition, reduced expression of the 43 kDa fimbrial subunit in the mutant was detected with both Western and Northern blotting. These results indicated that the rgp-1 gene product can play either a direct or indirect role in the colonization properties of P. gingivalis.

Isolation and characterization of a minor fimbria from Porphyromonas gingivalis

We have discovered two distinctly different fimbriae expressed by the same Porphyromonas gingivalis strain. The construction of a fimA mutant of P. gingivalis ATCC 33277 has previously been reported by N. Hamada et al. (Infect. Immun. 62:1696-1704, 1994). Expression of fimbriae on the surface of the fimA mutant and the wild-type strain, ATCC 33277, were investigated by electron microscopy. The wild-type strain produced long fimbrial structures extending from the cell surface, whereas those structures were not observed on the fimA mutant. However, short fimbrial structures were seen on the surface of the fimA mutant. The short fimbrial protein was purified from the fimA mutant by selective protein precipitation and chromatography on DEAE Sepharose CL-6B. We have found that the second fimbrial structure of P. gingivalis ATCC 33277 is distinct from the 41-kDa (43-kDa) major fimbrial protein (FimA). We provisionally call this protein minor fimbriae. The molecular mass of the minor fimbriae is 67 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions after boiling at 100 degrees C. The component shows a ladder-like pattern at 80 degrees C under nonreducing conditions, suggesting a tendency to aggregate or polymerize. In immunoblotting analysis, anti-minor fimbria serum reacted with both the 100 degrees C- and the 80 degrees C-treated minor fimbriae. The anti-minor fimbria serum also reacts with the same-molecular-size fimbrial preparation from the wild-type strain. Immunogold electron microscopy showed that the anti-minor fimbria serum bound to the minor fimbria on the cell surface of the wild-type strain. This is the first report on the identification of the minor fimbria produced by P. gingivalis. These results suggest that the minor fimbriae appearing on the fimA mutant strain are produced together with numerous long major fimbriae on the wild-type strain. Moreover, the minor fimbriae are different in size and antigenicity from the earlier-reported FimA, a major 41-kDa fimbrial component of P. gingivalis.

Role of Porphyromonas gingivalis protease activity in colonization of oral surfaces

Cysteine proteases, including Arg-gingipain of Porphyromonas gingivalis, have been implicated as important virulence factors in periodontal diseases. These enzymes are also involved in the hemagglutinating activity of the organisms. In order to determine the role of proteases in the colonization of the gingival margin, we have compared the attachment properties of P. gingivalis 381 with those of its Arg-gingipain-defective mutant, G-102. Interactions with gram-positive bacteria, human oral epithelial cells, extracellular matrix proteins, and type I collagen were evaluated. In all cases, mutant G-102 was deficient in attachment relative to the parental strain. The mutant's defects could be explained, in part, by the weak autoaggregation displayed by the mutant, which appeared to result from altered fimbrial expression. Both Western blot (immunoblot) and Northern (RNA) blot analyses indicated reduced expression of the major 43-kDa fimbrillin subunit in the mutant. These results suggest that Arg-gingipain may play both direct and indirect roles in the colonization of the gingival margin. In addition, fimbriae may play a direct role in interacting with some host surfaces.

The origin of fibroblasts and their role in the early stages of horizontal furcation defect healing in the beagle dog

The origin of fibroblasts, their proliferative activity and roles in the early stages of periodontal repair were investigated in order to better understand the periodontal healing process in furcation defects of the beagle dog after guided tissue regenerative therapy. Newly divided cells were identified by immunolocalization of bromodeoxyuridine (BrdU) injected 1 hour prior to sacrificing the animals. At 1 and 2 weeks after creation of the defects, the lesions were occupied primarily by granulation tissue. Under this condition, periodontal ligaments (PDL) fibroblasts in a coronal portion of the remaining PDL close to wounds proliferated actively, migrated along the root surface and formed fibrous connective tissue on the surface. Similarly, the fibroblasts adjacent to the bone surface also showed proliferative activity and engaged in active formation of fibrous connective tissue on the bone surface. The majority of labeled cells in both areas were located in the extravascular area. At 3 and 4 weeks, the defects were filled with an increased amount of new connective tissue and bone. The labeled fibroblasts were preferentially found in the most coronal portion of connective tissue formed on the root surface that was in direct contact with inflamed tissue, and the collagen fibers projected into granulation tissue. In areas of active bone formation, numerous labeled fibroblasts were located in connective tissue adjacent to the newly-formed bone. However, fibroblasts in the endosteum of new bone were rarely labeled These results indicate that fibroblasts involved in periodontal repair originate primarily from both the remaining PDL and alveolar bone, and actively engage in fibrous connective tissue formation in the early stages of periodontal repair The ability of PDL fibroblasts to proliferate, migrate, and form connective tissue on the root surfaces in the early repair stages appears to play a crucial role in the formation of the PDL and cementum, and consequently, in periodontal regeneration in the absence of root resorption and ankylosis. As the formation of new connective tissue and bone continues, the precursor cells for fibroblasts and osteoblasts are supplied locally through the continued divisions of the fibroblastic cells in association with the newly-formed connective tissue. Paravascular and endosteal cells appear to be minor contributors to new cell population during furcation defect repair in the beagle dog.

Synthesis of noncollagenous extracellular matrix proteins during development of mineralized nodules by rat periodontal ligament cells in vitro

To characterize the mineralized nodules produced by rat periodontal ligament (PDL) cells in vitro, we have studied the synthesis and distribution of mineralized tissue proteins at various stages of nodule formation. PDL cells were obtained from coagulum in the socket at 2 days after tooth extraction and cultured in Dulbecco's Modified Eagles Medium (DMEM) containing 10% fetal bovine serum and antibiotics. Confluent cells were grown in the presence of ascorbic acid (50 micrograms/ml), dexamethasone (5 microM), and beta-glycerophosphate (10 mM) for 3 weeks. Four stages showing distinct morphological characteristics during development of mineralized nodules were identified. Protein synthesis and deposition of proteins into the matrix were studied during these stages by metabolic labeling with [35S]methionine for 24 hours. Large quantities of SPARC (secreted protein, acidic and rich in cysteine) were synthesized by confluent cells but decreased during the progress of mineralized nodule formation. Two forms of osteopontin (OPN) (67 kDa and 61 kDa) were synthesized in comparable quantities by confluent cells; OPN and bone sialoprotein (BSP) were induced by dexamethasone and represented the major proteins in the mineralized matrix. The 67 kDa form of OPN was the predominant species in the mineralized matrix. Both OPN and BSP were localized by immunogold electron microscopy on globular as well as fused electron-dense structures at sites of tissue mineralization.

Expression, purification, and characterization of a novel G protein, SGP, from Streptococcus mutans

The sgp gene of Streptococcus mutans was recently detected immediately downstream from the dgk gene within the same operon. In this study, the sgp gene was subcloned into the pMAL-c2 vector and SGP (S. mutans G protein) was overexpressed in Escherichia coli as a fusion protein with the maltose-binding protein at a level of 40% of total cellular protein. One-step amylose affinity chromatography purification of this fusion protein yielded a product of approximately 95% purity. SGP was purified from this fusion protein following cleavage with protease factor Xa and DEAE-Sephacel chromatography. In nucleotide binding assays, recombinant SGP showed specific binding for GTP and GDP, but not ATP, CTP, and UTP, and also catalyzed efficient hydrolysis of GTP to GDP. Kinetic studies revealed that the SGP Km value for GTP in this reaction was approximately 5.9 microM. Mg2+ also served as a cofactor of SGP in this reaction. In vivo subcellular localization by immunogold labelling demonstrated that SGP was associated with both membrane and cytoplasmic fractions. SGP not only had structural similarities with other G proteins but also proved to have high-level intrinsic GTPase activity. Therefore, SGP appears to be a new member of the G protein superfamily and may participate in transmembrane signaling in the responses of S. mutans cells to environmental stimuli.

Immunohistochemical expression of extracellular matrix components of normal and healing periodontal tissues in the beagle dog

Periodontal regeneration requires formation of periodontal tissues lost due to periodontal disease. To better understand the formation of new periodontal tissues during periodontal repair and regeneration, immunohistochemical expression of extracellular matrix components of normal as well as healing periodontal tissues was evaluated and compared using the avidin-biotin complex immunohistochemical technique. For this purpose, horizontal furcation defects were created around mandibular P2 and P4 of 6 dogs after extraction of P1 and P3. The root surfaces were conditioned with citric acid and expanded polytetrafluoroethylene (ePTFE) membranes were placed and retained 0.5 mm above the cemento-enamel junction. The mucoperiosteal flaps were sutured in a coronal position. Two animals were sacrificed at 2, 4, and 8 weeks, and mesio-distal tissue slices containing normal or healing periodontal tissues were demineralized, dehydrated, and embedded in paraffin. Immunohistochemical localization of type I collagen (CI), fibronectin (FN), secreted protein, acidic and rich in cysteine (SPARC), vitronectin (VN), and bone sialoprotein (BSP) was performed on 6 microns thick sections. Morphological results demonstrated that at 2 weeks after defect creation, lesions were filled primarily with granulation tissue which was gradually replaced by newly-formed fibrous connective tissue, periodontal ligament (PDL), cementum, and bone between 4 and 8 weeks. The results of immunohistochemical study revealed that at 2 weeks the granulation tissue, especially in the intercellular spaces of inflammatory cells, was intensively stained for FN and VN. At 4 and 8 weeks, staining for CI, FN, and VN was found in fibrous connective tissue, the newly-formed PDL, cementum, and osteoid. Further the attachment zone of the PDL collagen fibers to cementum showed intense staining for FN. Immunostaining for SPARC was positive in the new PDL, cementum, and bone, while staining for BSP was restricted to the new cementum and bone. Interestingly, the PDL, especially in areas adjacent to active bone formation, demonstrated intense staining for BSP. However, fibrous connective tissue and PDL proper were unstained for BSP. These results indicate that FN and VN are involved in the early stages of periodontal repair, and periodontal regeneration is achieved through formation of periodontal tissues that are composed of different matrix components specific to different types of periodontal tissues.

Platelet-derived growth factor-modulated guided tissue regenerative therapy

The goal of this study was to develop an effective regenerative therapy capable of achieving periodontal regeneration of Class III furcation defects. We attempted to achieve this goal by combining three therapeutic approaches. First, the lesion was protected by an expanded polytetrafluoroethylene barrier membrane that prevents migration of gingival fibroblasts as well as osteogenic cells from the mucoperiosteal flaps. Second, platelet-derived growth factor-BB (PDGF-BB), which has potent chemotactic and mitogenic effects on periodontal ligament fibroblasts (PDL), was used to promote migration of fibroblasts and their proliferation on the root surface. Third, the root surface, demineralized by citric acid conditioning, was chosen as the primary site for PDGF-BB application. The demineralized root surface appeared to have the capability of providing a sustained release of the applied growth factor. This seemed to facilitate rapid repopulation of PDL fibroblasts on the root surface and new PDL formation in the early stages of repair, which contributed to complete periodontal regeneration without root resorption and ankylosis in later stages. Combining these approaches, we developed a therapy referred to as "PDGF-modulated guided tissue regenerative therapy." Unlike guided tissue regenerative therapy alone (without PDGF-BB), this therapy effectively promoted periodontal regeneration of Class III furcation defects in the beagle dog without significant ankylosis or root resorption.

Periodontal regeneration in class III furcation defects of beagle dogs using guided tissue regenerative therapy with platelet-derived growth factor

We developed an effective regenerative therapy, referred to as platelet-derived growth factor-BB (PDGF-BB)-modulated guided tissue regenerative (GTR) therapy (P-GTR), capable of achieving periodontal regeneration of horizontal (Class III) furcation defects in the beagle dog. To determine its efficacy, repair and regeneration of horizontal furcation defects by P-GTR therapy and GTR therapy were compared. Chronically inflamed horizontal furcation defects were created around the second (P2) and fourth mandibular premolars (P4). After demineralization of the root surfaces with citric acid, the surfaces of left P2 and P4 were treated with PDGF-BB (P-GTR therapy) and those of contralateral teeth were treated with vehicle only (GTR therapy). Periodontal membranes were placed and retained 0.5 mm above the cemento-enamel junction for both groups. The mucoperiosteal flap was sutured in a coronal position and plaque control was achieved by daily irrigation with 2% chlorhexidine gluconate. At 5, 8, and 11 weeks, two animals each were sacrificed by perfusion with 2.5% glutaraldehyde through the carotid arteries, and the lesions were sliced mesio-distally, demineralized, dehydrated, and embedded. Periodontal healing and regeneration after GTR and P-GTR therapy were compared by histomorphometric as well as morphological analysis. Morphometric analysis for each time period was performed on the pooled samples of P2 and P4. Five weeks after both therapies, the lesions were filled primarily by tissue-free area, epithelium, inflamed tissue, and a small amount of newly formed fibrous connective tissue. At 8 and 11 weeks after P-GTR therapy, there was a statistically greater amount of bone and periodontal ligament formed in the lesions. The newly formed bone filled 80% of the lesion at 8 weeks and 87% at 11 weeks with P-GTR therapy, compared to 14% of the lesion at 8 weeks and 60% at 11 weeks with GTR therapy. Also, with P-GTR therapy there was less epithelium and tissue-free area, less inflamed tissue, and less connective tissue. Morphological analysis indicated that the defects around P2 revealed faster periodontal repair and regeneration than those around P4. While the lesions around P2 were effectively regenerated by 11 weeks even after GTR therapy, those around P4 failed to regenerate. On the other hand, P-GTR therapy further promoted periodontal repair and regeneration so that at 8 weeks the lesions around P2 and P4 demonstrated complete and nearly complete regeneration, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Differentiation of periodontal ligament fibroblasts into osteoblasts during socket healing after tooth extraction in the rat

BACKGROUND

The entire socket after tooth extraction is filled with new bone formed by osteoblasts (Obs), but the origin of these Obs remains unknown. Thus, the proliferation and migration of paravascular and endosteal fibroblastic cells and periodontal ligament (PDL) fibroblasts (Fbs) and their differentiation into Obs during socket healing after extraction of the first maxillary molars of the rat were investigated.

METHODS

The proliferative activity and migration of these cells in the sockets after tooth extraction were studied using radioautography and immunohistochemistry after injection of 3H-thymidine and 5-bromo-2'-deoxyuridine (BrdU), respectively. Their morphological changes during differentiation was investigated by transmission electron microscopy.

RESULTS

One day after tooth extraction, PDL Fbs were the major cell type in the PDL remnant of the socket. Proliferation was low (labeling index (LI) = approximately 2%) until 16 h after tooth extraction but dramatically increased to a maximum level 1 day postextraction (LI = 23%). Between 1 and 2 days, numerous PDL Fbs in the PDL remnant actively migrated into the coagulum and continued to proliferate. On the basis of the high proliferative activity and small number of cellular organelles responsible for procollagen synthesis, these cells appear immature. At 3 days, Fbs contained more cellular organelles and deposited more collagen fibers as they replaced the coagulum with dense connective tissue and the LI declined. At 4 and 5 days, some of the Fbs began to differentiate into Obs, and the proliferation of Fbs dramatically decreased to baseline values. The migration of PDL Fbs and their differentiation into Obs were investigated by labeling with 3H-thymidine or BrdU 1 day after tooth extraction. Heavily labeled Fbs were observed in the PDL remnant at 1 day, in the coagulum at 2 days, and in the dense connective tissue at 3 days. Labeled Obs associated with new bone were seen 4 days after injection. Endosteal and paravascular Fbs also proliferated, but at a lower level and at later time periods than the PDL Fbs. Surprisingly, endosteal and paravascular Fbs contributed only a small population of Fbs to socket healing.

CONCLUSIONS

These results indicate that PDL Fbs after tooth extraction actively proliferative, migrate into the coagulum, form dense connective tissue, and differentiate into Obs which form new bone during socket healing.

Interaction of HIV-1 and human salivary mucins

Previous studies have suggested that salivary secretions may act as inhibitors of HIV-1 replication in vitro. This inhibitory activity was determined to be associated mainly with secretions obtained from the human submandibular-sublingual glands, and subsequent electron micrographs revealed the association of viral particles with the salivary sediment. Fractionation of human submandibular-sublingual (HSMSL) saliva by size-exclusion chromatography was initiated, and resulting fractions were tested for their ability to modulate the replication of HIV-1 using a plaque assay on HeLa CD4+ cell monolayers. Results indicated that the filtration-sensitive inhibitory activity was primarily associated with the mucin-rich fractions, and the inhibitory activity was found to reduce the number of infectious units by 75%. To determine the identity of the salivary components involved, adsorption experiments involving the interaction of HIV particles with immobilized salivary components were performed. Immunological counter staining revealed an interaction of HIV particles as well as recombinant gp120 with the lower-molecular-weight mucin. Electron microscopic examination of the mucin-rich fractions-HIV incubates revealed the aggregation of virus particles by salivary components. These results suggest that human salivary mucins may have a role in modulating the infectivity of HIV-1.

Clinical, microbiological, and histological factors which influence the success of regenerative periodontal therapy

The primary objectives of this double-blind, controlled clinical trial were to assess factor(s) which affect the success of guided tissue regeneration (GTR) procedures in mandibular Class II buccal furcation defects. Thirty subjects, with mandibular Class II furcation defects, were randomly assigned to one of two treatment groups; patients in Group A received oral hygiene instructions with scaling and root planing, while subjects in Group B received similar treatment but without subgingival scaling and root planing at the affected site. After initial oral hygiene instructions and scaling and root planing, GTR surgery was performed using ePTFE barrier membranes. Membranes were retrieved at 6 weeks and subjected to histological examination. Twelve months after regenerative therapy, clinical measurements and re-entry surgical measurements were repeated. Probing reduction (2.61 mm), horizontal probing attachment gain (2.59 mm), and vertical probing attachment gain (0.95 mm) were all significantly better compared to baseline. Likewise, significant improvements in furcation volume (8.0 microliters) and in bone measurements were observed at re-entry. There was no discernible difference between subjects for whom complete anti-infective therapy was deferred to the time of the surgery (Group B) compared to subjects in whom complete anti-infective therapy was performed as part of the hygienic phase of therapy (Group A). Pre-operative pocket depth was directly correlated with the magnitude of attachment gain as well as the amount of new bone formation in the furcation area. Subjects who maintained good oral hygiene and who had minimal gingival inflammation throughout the study demonstrated consistently better regenerative response.(ABSTRACT TRUNCATED AT 250 WORDS)

Inactivation of the Porphyromonas gingivalis fimA gene blocks periodontal damage in gnotobiotic rats

Fimbrial production by Porphyromonas gingivalis was inactivated by insertion-duplication mutagenesis, using the cloned gene for the P. gingivalis major fimbrial subunit protein, fimA. by several criteria, this insertion mutation rendered P. gingivalis unable to produce fimbrilin or an intact fimbrial structure. A nonfimbriated mutant, DPG3, hemagglutinated sheep erythrocytes normally and was unimpaired in the ability to coaggregate with Streptococcus gordonii G9B. The cell surface hydrophobicity of DPG3 was also unaffected by the loss of fimbriae. However, DPG3 was significantly less able to bind to saliva-coated hydroxyapatite than wild-type P. gingivalis 381. This suggested that P. gingivalis fimbriae are important for adherence of the organism to saliva-coated oral surfaces. Further, DPG3 was significantly less able to cause periodontal bone loss in a gnotobiotic rat model of periodontal disease. These observations are consistent with other data suggesting that P. gingivalis fimbriae play an important role in the pathogenesis of human periodontal disease.

Evidence for up-regulation of epidermal growth-factor receptors on rat periodontal ligament fibroblastic cells associated with stabilization of phenotype in vitro

This study sought to understand the role of epidermal growth factor receptor (EGF-R) in periodontal ligament (PDL) fibroblasts. Rat PDL fibroblastic cells and ROS 17/2.8 cells (highly differentiated osteoblastic osteosarcoma cells) were cultured and treated with transforming growth factor-alpha (TGF-alpha), EGF, dexamethasone (Dex) or a combination of EGF and Dex. Alkaline phosphatase (ALP) activity, an early differentiation marker for mineralized tissue-forming cells, was measured using p-nitrophenylphosphate as a substrate. For Scatchard analysis of [125I]-EGF binding, cells were incubated in Dulbecco's modified Eagle's medium containing 0.2% bovine serum albumin and 0-64 ng/ml of [125I]-EGF for 4 h at 4 degrees C. Also, the synthesis of EGF-R protein and the expression of mRNA for EGF-R were measured by immunoprecipitation and Northern blot analysis, respectively. Untreated PDL fibroblastic cells showed a gradual increase in spontaneous ALP activity from 32.4 U/10(6) cells at 2 days to 49.6 U/10(6) cells at 7 days of culture. ALP activity was further increased to 70.8 U/10(6) cells at 7 days after treatment with Dex, whereas EGF treatment reduced it to 19.4 U/10(6) cells. Culture of PDL fibroblastic cells in the presence of a combination of Dex and EGF decreased the Dex-induced ALP activity from 70.8 U to 41.8 U/10(6) cells at 7 days. A similar inhibitory effect on ALP activity was found after treatment with TGF-alpha. In contrast, ROS cells maintained a high ALP activity (1748 U/10(6) cells) throughout culture, unaffected by EGF. Scatchard analysis demonstrated that PDL fibroblastic cells have both high- and low-affinity forms of EGF-R, while ROS cells did not have any detectable EGF-R. Treatment of PDL cells with Dex for 2 days decreased the synthesis of EGF-R protein, the expression of EGF-R mRNA and the number of EGF-R. In contrast, EGF treatment increased the expression of EGF-R mRNA. These data suggest that PDL fibroblastic cells express numerous EGF-R, but the number decreases during their differentiation into mineralized tissue-forming cells under the influence of Dex. Thus, EGF-R may function in the stabilization of phenotype in PDL fibroblastic cells.

Aggregation of human immunodeficiency virus type 1 by human salivary secretions

Human immunodeficiency virus (HIV-1) is generally transmitted by parenteral contact with infected body secretions. Although extensive epidemiological data and familial studies have failed to provide any conclusive data that saliva may act as a vehicle for transmission of AIDS, both professional and public anxieties remain. The present study, as well as others, suggests that salivary secretions may act as inhibitors of HIV-1 replication in vitro. In our study, the inhibitory activity was determined to be associated mainly with secretions obtained from the human submandibular-sublingual glands. Human submandibular-sublingual (HSMSL) and parotid (HPS) salivas were collected and tested for their ability to modulate the replication of HIV-1, using a plaque assay on HeLa/CD4+ cell monolayers. Initial results examining freshly collected salivary samples from ten individuals confirmed the results previously obtained by Fox et al. (1988, 1989). An average plaque reduction of approximately 66% was obtained with HSMSL, in contrast to 34% reduction obtained with HPS. Titration of the inhibitory activity in HSMSL showed detectable levels at a 1:500 dilution. Comparison of inhibitory activity of dialyzed and lyophilized saliva to fresh saliva indicated little difference between the two samples when filtration occurred after the addition of HIV-1. However, the effect of filtration was significantly diminished in the lyophilized samples. Electron microscopic examination of the saliva-HIV incubates revealed the aggregation/entrapment of virus particles by salivary components. These results suggest that human salivary secretions (with HSMSL > HPS) may have a role in modulating the infectivity of HIV-1.

Characterization of an amylase-binding component of Streptococcus gordonii G9B

The goal of the present study was to begin characterizing the amylase-binding component(s) on the surface of Streptococcus gordonii G9B. Alkali extracts but not phenol-water extracts of this bacterium inhibited 125I-amylase binding to S. gordonii G9B. To identify the bacterial components involved in amylase binding, the alkali extract was subjected to affinity chromatography on amylase-Sepharose. Immunoblotting with a rabbit antiserum against S. gordonii G9B revealed that a 20-kDa streptococcal component was eluted from the amylase-Sepharose with 1% sodium dodecyl sulfate (SDS), 2 M KSCN, or 0.1 M sodium citrate buffer, pH 4.5. Subsequently, the 20-kDa component was prepared from alkali extracts by electroelution from preparative SDS electrophoresis or by gel filtration chromatography. This component was trypsin sensitive, and an antibody raised against it inhibited the binding of 125I-amylase to S. gordonii G9B. Indirect immunofluorescence microscopy and immunogold electron microscopy demonstrated that both bound amylase and the 20-kDa component were localized to the cell division septum on dividing cells or to polar zones on single cells. In addition, exponentially growing bacteria bound more 125I-amylase than stationary-phase cells did. Collectively, these results suggest that a 20-kDa amylase-binding component is present on the surface of the nascent streptococcal cell wall.

Mitogenic, chemotactic, and synthetic responses of rat periodontal ligament fibroblastic cells to polypeptide growth factors in vitro

The mitogenic, chemotactic, and synthetic responses of rat periodontal ligament (PDL) fibroblastic cells to epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), recombinant human platelet-derived growth factor (rhPDGF)-AB, rhPDGF-BB, natural (n) PDGF-AB, and insulin-like growth factor-I (IGF-I) were examined in vitro using PDL cells obtained from the coagulum of healing tooth sockets. PDGFs and IGF-I have potent and comparable mitogenic effects on PDL fibroblastic cells. The maximum mitogenic effect of PDGFs was observed at the concentration of 10 ng/ml, whereas that of IGF-I was seen at concentrations higher than 100 ng/ml. In contrast, EGF induced moderate, and TGF-beta inhibitory mitogenic responses. The combination of rhPDGF-AB with either EGF or TGF-beta demonstrated comparable mitogenic potency, equivalent to the level of PDGF alone regardless of the mitogenic effect of other growth factors. The combination of rhPDGF-AB and IGF-I, however, showed a synergistic effect revealing the highest mitogenic effect among all individual growth factors as well as any combinations of the growth factors tested. Similarly, PDL fibroblastic cells demonstrated strong chemotactic responses to both IGF-I and PDGFs. The maximum effect was observed by IGF-I at concentrations higher than 10 ng/ml, followed by rhPDGF-BB at 0.1 ng/ml, rhPDGF-AB and nPDGF at concentrations ranging from 0.1 to 1 ng/ml. TGF-beta revealed no, and EGF slightly increased, chemotactic effects. IGF-I slightly enhanced the synthesis of total protein, whereas other factors had no significant effect. However, both rhPDGF-AB and TGF-beta stimulated collagen synthesis. On the other hand, IGF-I showed no effect on collagen synthesis, while EGF suppressed collagen synthesis. These findings suggest that rhPDGF-BB and IGF-I stimulate proliferation and chemotaxis of PDL fibroblastic cells. In addition, the combination of these growth factors further increases the mitogenic effect. rhPDGF-AB also stimulates collagen synthesis by PDL fibroblastic cells. Thus, rhPDGF-BB and IGF-I may have important roles in promotion of PDL healing, and consequently, may be useful for clinical application in periodontal regenerative procedures.

In vitro formation of mineralized nodules by periodontal ligament cells from the rat

The purposes of this study were to determine whether periodontal ligament (PDL) cells are capable of producing mineralized nodules in vitro and to analyze ultrastructural features of the nodules. Rat PDL cells were obtained from coagulum in the socket at 2 days after tooth extraction and cultured at confluence in standard medium containing Dulbecco's Modified Eagle's Medium supplemented with 10% FBS and antibiotics. To test mineralized nodule formation, cells were further cultured for an additional 3 weeks in the standard medium containing (1) ascorbic acid (50 micrograms/ml) and sodium beta-glycerophosphate (10 mM), (2) ascorbic acid, sodium beta-glycerophosphate, and dexamethasone (5 microM), or (3) ascorbic acid alone. Cells were then fixed in 2.5% glutaraldehyde, postfixed in 1% OsO4, and prepared for light and electron microscopy. Three-dimensional nodules containing mineralized matrices were formed only when the cells were cultured in the presence of ascorbic acid and dexamethasone. They were composed of multilayered fibroblasts (up to 13 layers), and highly organized collagen fibrils with 64 nm cross-banding patterns between the cell layers. The fibroblasts in the nodules exhibited an elongated shape with a high degree of cytoplasmic polarity throughout the nodule, and have the morphological features of PDL fibroblasts as seen in vivo. Mineral deposition with needle-like crystals was initiated on collagen fibrils located in intercellular spaces of the upper cell layers and became increasingly heavier towards the bottom half of the nodules. X-ray microanalysis and electron diffraction analysis confirmed that mineral deposition contained calcium and phosphate in the form of immature hydroxyapatite.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification, characterization, and localization of a major membrane protein antigen from Porphyromonas (bacteroides) gingivalis

Humans and rats infected with P. gingivalis develop a strong immune response to a 75 kDa major membrane component of P. gingivalis and hence knowledge of the nature of this molecule may aid in understanding the host response to P. gingivalis during infection. Purification of the 75 kDa protein was achieved by repeated precipitation from a crude sonicate of P. gingivalis 2561 at pH 5.0. Homogeneity of the purified 75 kDa protein was confirmed by SDS-PAGE and Western immunoblot analysis using monoclonal and polyclonal antibodies. The purified protein revealed an apparent molecular mass of 300 kDa in native form. Although most of the strains of P. gingivalis tested showed a major membrane protein band in the range of 61 to 78 kDa, on Western immunoblot analysis only the strains which have proteins in the range of 75 to 78 kDa were reactive with anti-75 kDa protein polyclonal antibodies. Affinity purified polyclonal antibodies were used to localized 75 kDa protein on the cell surface of P. gingivalis 2561 by immunogold electron microscopy. Immunolabeling of the 75 kDa protein demonstrated specific localization of the protein along the outer cell membrane, but not on the fimbriae. Furthermore, immunogold labeling of the 75 kDa protein on the thin sections showed that the 75 kDa component was present on not only the outer membrane, but also on the cell membrane, and on membrane bound organelles. Localization of this protein suggests that the 75 kDa component is a membrane-associated protein.

Occurrence of epidermal growth factor-binding sites during differentiation of cementoblasts and periodontal ligament fibroblasts of the young rat: a light and electron microscopic radioautographic study

Occurrence of epidermal growth factor (EGF)-binding sites during differentiation of cementoblasts and periodontal ligament (PDL) fibroblasts was investigated using radioautography after I. V. injection of 125I-EGF to 14-day-old rats. During differentiation of cementoblasts, a very low level of EGF-binding sites was present on the mesenchymal cells in dental follicle proper, precementoblasts, and cementoblasts. On the other hand, during differentiation of PDL fibroblasts, numerous EGF-binding sites were observed on the undifferentiated paravascular cells and on the perifollicular mesenchymes representing the major source of PDL fibroblast precursor cells. Also heavy labeling was observed throughout their differentiation to PDL fibroblasts, as well as during full synthetic activity as mature cells. Quantitative analysis of the light microscopic radioautographs revealed that these cells demonstrated approximately 4 grains per 100 microns 2 of cell area. These results suggest that EGF plays an important role in differentiation of PDL fibroblasts, but not in that of cementoblasts. Furthermore, the well-known in vivo effect of EGF in producing precocious eruption of teeth may be a consequence of a more extensive effect of EGF throughout differentiation of PDL fibroblasts as well as during full synthetic activity as mature cells.

Purification, characterization and immunolocalization of fimbrial protein from Porphyromonas (bacteroides) gingivalis

Rapid and reproducible method is described here for the purification of the 43 kDa fimbrial protein from P. gingivalis by preferential fractionation in the presence of 1% SDS and 0.2M of a bivalent cation at pH 6.5. Homogeneity of the purified 43 kDa was confirmed by SDS-PAGE and Western blot analysis using monoclonal and polyclonal antibodies raised against this protein. Amino acid composition and the amino acid sequence of the first 30 amino acid residues of the purified fimbriae are consistent with the composition and sequence predicted from the cloned gene of the fimbrial subunit. Circular dichroism spectra shows high levels of beta-sheet structure. The purified 43 kDa polymer shows fimbriae-like morphology under the electron microscope. Ultrastructural localization of the 43 kDa protein by the immunogold technique revealed specific labeling of the fimbriae with a diameter of approximately 3.5 to 5.0 nm. Localization of this protein suggest that the 43 kDa component is a fimbrial subunit.

Parameters affecting the inhibition of Candida albicans GDH 2023 and GRI 2773 blastospore viability by purified synthetic salivary histidine-rich polypeptides

Purified synthetic salivary histidine-rich polypeptides, HRPs 2, 3, 4, 5, and 6, were observed to inhibit Candida albicans blastospore viability at yeast cell concentrations ranging from 10(2) to greater than 10(6) colony forming units per ml. Among the HRPs, HRP-4 was the best inhibitor with significant killing activity noted at a peptide concentration of 0.5 microgram per ml. Antifungal potency under growth conditions was observed to be dependent upon pH. In contrast, killing did not vary throughout the pH range tested under non-growth conditions. Electron microscopy results demonstrated HRP damage at pH 5 which appeared to be initiated at the membrane. At pH 7.4, micrographs revealed clear evidence of intracellular destruction suggesting more extensive damage at neutral as compared to acidic pH. These results suggest that within the changing realm of the oral cavity, the HRPs would be expected to be potent killers of C. albicans.

Human immunodeficiency virus type 1 Pr55gag and Pr160gag-pol expressed from a simian virus 40 late replacement vector are efficiently processed and assembled into viruslike particles

Human immunodeficiency virus type 1 (HIV-1) gag and pol genes were expressed by using fragments of the BH10 clone of HIV inserted into a simian virus 40 late replacement vector. An initial construct containing the entire coding regions of gag, pol, and vif produced only minute amounts of the gag precursor, Pr55gag. However, high-level expression was obtained when an additional sequence from the env gene (the rev-responsive element) was inserted 3' of vif in the correct orientation, and rev was provided in trans from a second vector. Western immunoblot analysis of transfected cells showed the presence of large amounts of both Pr55gag and Pr160gag-pol as well as all of the expected cleavage products. Electron microscopy of thin sections of transfected cells showed a multitude of viruslike particles. Both immature particles in the process of budding and particles containing the condensed core characteristic of HIV were observed. Analysis of the released viruslike particles showed the presence of active reverse transcriptase. Sucrose gradient analysis of particles produced from [3H]uridine-labeled cells indicated a peak of radioactivity which cosedimented with a peak of p24, suggesting that the particles contained RNA.

Radioautographic study of [3H]mannose utilization during cementoblast differentiation, formation of acellular cementum, and development of periodontal ligament principal fibers

The formation of acellular cementum and the deposition of [3H]mannose-labeled extracellular matrix were studied in 14-day-old Sprague-Dawley rats. The sequential events of cementogenesis and periodontal ligament formation observed by light and electron microscopy were described from the stage of an intact root sheath to postcementogenesis. Ultrastructural examination of cementoblasts and periodontal ligament fibroblasts revealed [3H]mannose labeling of the Golgi apparatus at 10 minutes, collagen secretion granules at 30 minutes, and the extracellular matrix beginning at 30 minutes. The extracellular matrix between cementoblasts and dentin was heavily labeled at 1 and 4 hours. Newly formed principal fibers of the periodontal ligament were also heavily labeled at 4 hours. Fully differentiated cementoblasts exhibited the largest sectional profiles and the highest number of silver grains per unit area of cytoplasm. The morphologic and radioautographic data suggest that during the formation of acellular cementum, the cementoblast phenotype is expressed for a short period of time, after which cementoblasts appear to mix with the fibroblasts of the periodontal ligament.

Radioautographic demonstration of receptors for epidermal growth factor in various cells of the oral cavity

Mouse iodinated epidermal growth factor (EGF) was localized by light and electron microscopic radioautography in basal cells of oral epithelium, papillary cells of the enamel organ, periodontal ligament fibroblasts, preodontoblast precursor cells, and preosteoblasts of the alveolar bone of 13-day-old Sprague-Dawley rats. The specificity of binding in these cells was suggested by an observed reduction of about 90% in the labeling when excess unlabeled EGF was injected along with the 125I-EGF. In contrast, fully differentiated cells, such as ameloblasts, odontoblasts, and osteoblasts, were only poorly labeled. Quantitative analysis of the light microscopic radioautographs revealed that the papillary cells had the highest level of labeling (5.5 grains per 100 micron 2 of cell area). The significance of the rather high labeling of the preosteoblasts of the alveolar bone and the fibroblasts of the periodontal ligament is unknown. However, the well-known effect of EGF in producing precocious eruption of teeth may be a consequence of an effect on these two cell types.

3H-mannose utilization by fibroblasts of the periodontal ligament

The synthesis, intracellular translocation, and secretion of mannose-containing glycoproteins(s) by periodontal ligament fibroblasts have been investigated by means of electron microscopic radioautography. Tritiated mannose was administered to young mice via jugular vein, and radioautographs were prepared at 5, 10, 20, and 35 minutes, 4 and 8 hours after injection. Analysis of electron microscopic radioautographs revealed a maximum labeling (94%) with 3H-mannose of the rough endoplasmic reticulum at 5 minutes. Labeling of the Golgi components started to increase from 10 minutes (14%) and reached a maximum level at 20 minutes (31.2%). At 35 minutes, secretion granules, dense bodies, profiles of intracellular collagen, and the cell surface were labeled. At 8 hours, most labelling (79.2%) was extracellular, and associated either with the collagenous matrix (43.7%) or the cell surface (35.5%). Cytoplasmic vesicles containing dense materials around collagen fibrils were also labeled at 8 hours. It is concluded that mannose is directly incorporated into the rough endoplasmic reticulum (RER), and that mannose-containing glycoprotein(s) are packaged in the Golgi apparatus into secretory granules. Mannose-containing glycoprotein(s) become distributed on the periodontal ligament (PDL) fibroblast cell surface, cytoplasmic dense bodies, and the extracellular matrix.

Localization of fibronectin in gingival connective tissue of the beagle dog. Ultrastructural detection with ferritin and peroxidase-conjugated antibodies

Ferritin and peroxidase-conjugated antibodies were used in an indirect antibody method to localize fibronectin in gingival connective tissues. Fibronectin was found in the basal lamina beneath the epithelium and endothelium. Collagen fibrils associated with the basement membranes were also heavily coated by fibronectin. Amorphous patches of fibronectin were found adjacent to the plasma membrane of epithelial cells as well as free in the interepithelial spaces. Fibronectin was present throughout the connective tissue in close association with individual collagen fibrils, apparently serving as an interfibrillar cementing substance. Patches of fibronectin were located at the cell surface of fibroblasts, plasma cells, lymphocytes, endothelial cells, smooth muscle cells, and neutrophils. These amorphous patches were observed to connect adjacent cells across narrow spaces and to connect cells to collagen fibrils. The heavy labeling for fibronectin visualized by fluorescent microscopy around gingival blood vessels (Cho et al., 1985) can be accounted for by a heavy coating of fibronectin on the collagen fibrils and basal laminas associated with endothelial cells, as well as by the presence of abundant deposits of fibronectin along the cell membranes of endothelial cells and in the intercellular spaces of the vessel wall.

A freeze-fracture cytochemical study of filipin-sterol complexes in pulp fibroblasts of the rat incisor

The sterols in microdomains of the cell membrane of pulp fibroblasts react with the polyene antibiotic, filipin, to form filipin-sterol complexes (FSC). The FSC appear in ultra-thin sections as minute corrugations or deformations of the membrane. In freeze-fracture replicas, individual FSC were 20-30 nm elevations and were abundant on filopodial cell processes. They were not found in the membrane of cell-to-matrix attachment plaques or in cell-to-cell adherens junctions. The findings suggest that stabilization of the membrane at these sites may interfere with FSC formation and conversely that the absence of FSC may be an indication of membrane stabilization.

Localization of fibronectin in gingival connective tissue of the beagle dog. Immunofluorescent light microscopic findings

Affinity purified antibodies to plasma fibronectin were used to localize fibronectin in the connective tissues of inflamed and noninflamed beagle gingiva. In noninfiltrated gingival connective tissue, fibronectin was demonstrated in the basement membrane beneath gingival epithelium and around blood vessels as a uniform and intensely stained band about 3 to 10 micron thick. Fibronectin was also distributed throughout the connective tissue in association with collagen fibrils as a more diffuse, less intensely stained pattern. The inflamed gingiva included in this study was characterized by proliferation of epithelial pegs, heavy infiltration of plasma cells and loss of collagen within the subepithelial connective tissue. In these sites, fibronectin was present as an intensely stained band around blood vessels and at the crest of connective tissue papillae nearest the sulcular space. The fibronectin in the basement membrane beneath the epithelium appeared diminished and less uniformly distributed. A delicate network of fibronectin was present around plasma cells and the remaining collagen fibers.

Effects of L-azetidine-2-carboxylic acid on matrix secretion and Golgi structure in fibroblasts and osteoblasts of the mouse

The effect of a proline analogue, L-azetidine-2-carboxylic acid (LACA), on collagenous matrix secretion by periodontal ligament fibroblasts and alveolar bone osteoblasts was studied by light and electron microscopic radioautography after injection of 3H-glycine; 3H-glycine labeled material accumulated in the cisternae of the rough endoplasmic reticulum and was not secreted for over 4 hours. The Golgi complex of both fibroblasts and osteoblasts showed a marked alteration of its composition after LACA administration. All Golgi saccules and collagen secretion granules disappeared within 2 hours. Flattened Golgi cisternae were still present and appeared to be unaffected by the administration of LACA. These observations indicate that Golgi saccules in collagen-secreting cells are the initial staging areas for the formation of collagen secretory granules and that there is a close correlation between form and function in the Golgi apparatus of collagen-secreting cells.

Ultrastructural and cytochemical studies of the fate of unsecreted collagen precursors after administration of colchicine to mice

The administration of colchicine disrupts the normal organization of the Golgi complex and blocks the secretion of collagen precursors in periodontal ligament fibroblasts of the mouse. The fate of the unsecreted collagen precursors contained in Golgi-derived saccules and newly formed dense bodies was followed by electron microscopy. A progressive condensation of saccule content along with phase separation of electron-dense and electron-lucent material was observed. Fusion of saccules with dense secretory bodies gave rise to larger inclusions (zebra bodies; ZB) filled with a combination of electron-dense and electron-lucent material. In some ZB, these materials appeared to polymerize into fibrillar units. The fibrillar units stained with silver methenamine like normal collagenous fibrils. These results suggest that unsecreted collagen precursors accumulate in vesicular compartments within which partial polymerization can occur. This finding may explain some reports of intracellular collagenous fibrils in fibroblasts of pathologically altered connective tissues.

Radioautographic analysis of [3H]-fucose utilization by mouse odontoblasts with emphasis on intracytoplasmic and plasma membrane glycoproteins

[3H]-fucose utilization by odontoblasts was studied by light and electron microscopic radioautography. At 10 min after injection, fucose label was concentrated in the Golgi area. By 20-30 min, there was a progressive decline in Golgi labelling with label present at the plasma membrane, terminal web, odontoblast process and predentine matrix. At 4 h, the predentine and the predentine-dentine junction were heavily labelled. At the ultrastructural level, Golgi labelling at 10 min was mostly localized to cisternal elements and at 20 and 30 min secretory granules and dense bodies were also labelled. Most of the silver grains observed in the terminal web were associated with microfilaments near the plasma membrane. In the predentine, the matrix itself accounted for 23.0 per cent of the label at 4 h and the plasma membrane of the odontoblast process accounted for 19 per cent. The results indicate that odontoblasts, in addition to secreting glycoproteins into the dentinal matrix, also continuously manufacture glycoproteins for incorporation into the cell surface, the lysosomal system and the terminal web.

In vitro and in vivo studies of cellular lysis of oral bacteria by a lysozyme-protease-inorganic monovalent anion antibacterial system

Compared with anion-activated cell lysis of oral bacteria damaged with either lysozyme or trypsin, cells which were treated with both of these enzymes showed a far greater degree of lysis. This was true regardless of whether turbidimetric, DNA release, or electron microscopic assays were used to monitor the lytic process. At an acidic pH of 5.2 and an NaHCO3 concentration of 100 mM, the kinetics of lysis for two different serotype c strains of Streptococcus mutans were similar. At 0 to 100 mM bicarbonate, however, differences in the lytic susceptibilities of the two strains were evident. At pH 5.2, NaHCO3, but not NaSCN, NaCl, or NaF, was effective in promoting cell lysis of the oral bacteria. At apparent sublytic concentrations of NaHCO3, lysis was achieved by adding appropriate concentrations of NaSCN, NaCl, or NaF to the lysozyme-protease-damaged cells. In in vivo studies, hamsters given a combination of NaHCO3, NaCl, and NaSCN were found to have significantly reduced levels of S. mutans on their molar teeth compared with that found in controls or animals exposed to any one of the salts alone or to a combination of chloride and thiocyanate only. The results suggest that bicarbonate is an essential anion which, together with the other major salivary inorganic monovalent anions, plays an active role in the lysis and ultimate elimination of cariogenic bacteria.