Biomedical subjects

D L Cochran

Publications and source records attributed to D L Cochran.

At least 91 records · Page 5Linked to original sources

PubMed1997

Biologic width around titanium implants. A histometric analysis of the implanto-gingival junction around unloaded and loaded nonsubmerged implants in the canine mandible.

The use of endosseous dental implants as transmucosal devices necessitates the successful integration of three different tissues: bone, connective tissue, and epithelium. So far, studies have predominantly focused on hard tissue integration. Much less is known about soft tissues. This study examined the dimensions of the implantogingival junction in relation to clinically healthy unloaded and loaded nonsubmerged implants. In total, 69 titanium plasma-sprayed (TPS) and sandblasted acid-etched (SLA) implants were placed in an alternating fashion in six foxhounds and allowed to heal for 3 months. Two dogs were sacrificed after the initial healing period. The remaining four dogs had crowns fabricated that were allowed to function for up to 12 months. These animals were sacrificed after 3 and 12 months of loading. Histometric analysis of undecalcified histologic sections included the evaluation of the sulcus depth (SD), the dimensions of the junctional epithelium (JE), and the connective tissue contact (CTC). Mean values in the 3 month unloaded group were 0.49 mm for SD, 1.16 mm for JE, and 1.36 mm for CTC. These dimensions were 0.50 mm for SD, 1.44 mm for JE, and 1.01 mm for CTC for the 3 month loaded group. After 12 months of loading, these values were 0.16 mm for SD, 1.88 mm for JE, and 1.05 mm for CTC. The sum of these measurements was similar for the different time points and similar to the same dimensions around teeth. TPS and SLA surfaces had no influence on the evaluated parameters (P > 0.05). The data suggest that a biologic width exists around unloaded and loaded nonsubmerged one-part titanium implants and that this is a physiologically formed and stable dimension as is found around teeth.

Analysis of Variance↗

PubMed1997

Effects of interleukin-1 beta on matrix metalloproteinase-3 levels in human periodontal ligament cells.

MATRIX METALLOPROTEINASE-3 (MMP-3), or stromelysin-1, is an enzyme responsible for the degradation of a wide range of extracellular matrix proteins. Increases in MMP-3 activity have been found in several chronic inflammatory diseases, and this increased activity is thought to be mediated by interleukin-1 beta (IL-1 beta). Because IL-1 beta has been strongly associated with inflammatory periodontal disease, the purpose of this in vitro study was to investigate the role of IL-1 beta on the regulation of MMP-3 levels in cells derived from the human periodontal ligament (PDL). Human PDL cell cultures were treated with IL-1 beta at varying concentrations (0.01-1.0 ng/ml) for 24 hour prior to analysis at either transcript or protein levels. Following the isolation of total RNA, the relative levels of MMP-3 mRNA were determined using reverse transcription-polymerase chain reaction (RT-PCR) with 32P-end-labeled primers. Immunocytochemical detection of MMP-3 protein was performed using polyclonal antibodies to human MMP-3. The results of RT-PCR analysis demonstrated a concentration-dependent increase in MMP-3 mRNA expression, with IL-1 beta treatments of 0.1 and 1.0 ng/ml significantly (P < 0.01) increased over those cells not treated with IL-1 beta. This increase in mRNA expression was paralleled by significant (P < 0.001) changes at the protein level, with an average of 27.6% of the cells stained positive for MMP-3 following IL-1 beta treatment (1.0 ng/ml), compared with control cells showing no positive staining for MMP-3. In conclusion, the results of this study demonstrate that IL-1 beta upregulates MMP-3 in human PDL cells on both an mRNA and a protein level. These findings suggest possibly important roles for IL-1 beta and MMP-3 in both normal turnover and maintenance of the PDL and in the connective tissue degradation associated with periodontal disease.

Analysis of Variance↗

PubMed1996

Chondrocyte cultures express matrix metalloproteinase mRNA and immunoreactive protein; stromelysin-1 and 72 kDa gelatinase are localized in extracellular matrix vesicles.

Previous studies have shown that costochondral cartilage cell cultures produce extracellular matrix vesicles which contain metalloproteinase activity. In the present study, we examined whether two matrix metalloproteinases (MMPs) known to be present in cartilage, stromelysin-1 and 72 kDa gelatinase, are expressed by fourth passage resting zone and growth zone costochondral chondrocytes and whether they are specifically incorporated into matrix vesicles produced by the cells. We also examined whether the cells synthesize tissue inhibitor of metalloproteinase-1 and -2 (TIMP-1 and TIMP-2). Oligonucleotide primers for stromelysin-1, 72 kDa gelatinase, tissue inhibitor of metalloproteinases-1 and -2 (TIMP-1 and TIMP-2), and GAPDH were synthesized and optimized for use in the reverse transcription-polymerase chain reaction (RT-PCR). It was found that both resting zone and growth zone chondrocytes produced mRNA for both MMPs and the two TIMPs. Further, immunostaining of cell layers with antibodies to 72 kDa gelatinase and stromelysin-1 showed that both cell types produced these MMPs in culture. Substrate gel electrophoresis and Western analysis were used to characterize MMP activity in matrix vesicles, media vesicles, or plasma membranes as well as in conditioned media produced by the chondrocyte cultures. It was found that matrix vesicles but not plasma membranes or media vesicles were selectively enriched in stromelysin-1. Also, 72 kDa gelatinase was found in matrix vesicles, but to a lesser extent than seen in media vesicles. The relative activity of each enzyme detected was cell maturation-dependent. No MMP activity was detected in conditioned media produced by either cell type. The results of this study show that MMPs are expressed by resting zone and growth zone chondrocytes in culture and differentially distributed among three different membrane compartments. This suggests that, in addition to the well-known activators and inhibitors of MMP activity in the matrix, differential membrane distribution may enable more precise control over the site, rate, and extent of matrix degradation by the cell.

Animals↗

PubMed1996

Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation.

Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent.

Animals↗

PubMed1996

Surface roughness modulates the local production of growth factors and cytokines by osteoblast-like MG-63 cells.

Titanium (Ti) surface roughness affects proliferation, differentiation, and matrix production of MG-63 osteoblast-like cells. Cytokines and growth factors produced in the milieu surrounding an implant may also be influenced by its surface, thereby modulating the healing process. This study examined the effect of surface roughness on the production of two factors known to have potent effects on bone, prostaglandin E2 (PGE2) and transforming growth factor beta 1 (TGF-beta 1). MG-63 cells were cultured on Ti disks of varying roughness. The surfaces were ranked from smoothest to roughest: electropolished (EP), pretreated with hydrofluoric acid-nitric acid (PT), fine sand-blasted, etched with HCl and H2SO4, and washed (EA), coarse sand-blasted, etched with HCl and H2SO4, and washed (CA), and Ti plasma-sprayed (TPS). Cells were cultured in 24-well polystyrene (plastic) dishes as controls and to determine when confluence was achieved. Media were collected and cell number determined 24 h postconfluence. PGE2 and TGF-beta 1 levels in the conditioned media were determined using commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. There was an inverse relationship between cell number and Ti surface roughness. Total PGE2 content in the media of cultures grown on the three roughest surfaces (FA, CA, and TPS) was significantly increased 1.5-4.0 times over that found in media of cultures grown on plastic or smooth surfaces. When PGE2 production was expressed per cell number, CA and TPS cultures exhibited six- to eightfold increases compared to cultures on plastic and smooth surfaces. There was a direct relationship between TGF-beta 1 production and surface roughness, both in terms of total TGF-beta 1 per culture and when normalized for cell number. TGF-beta 1 production on rough surfaces (CA and TPS) was three to five times higher than on plastic. These studies indicate that substrate surface roughness affects cytokine and growth factor production by MG-63 cells, suggesting that surface roughness may modulate the activity of cells interacting with an implant, and thereby affect tissue healing and implant success.

Biocompatible Materials↗

PubMed1996

Proliferation, differentiation, and protein synthesis of human osteoblast-like cells (MG63) cultured on previously used titanium surfaces.

This study compared osteoblasts proliferation, differentiation, and protein synthesis on new and used titanium (Ti) disks to test the hypothesis that cleaning and resterilization of previously used Ti disks does not alter cell response to a particular surface. Ti disks of varying roughness were prepared by one of five different treatment regimens. Standard tissue culture plastic was used as a control. Human osteoblast-like cells (MG63) were cultured on the Ti disks and cell proliferation, cell differentiation, RNA synthesis and matrix production (collagen and noncollagen protein; proteoglycans) measured. After their first use, the disks were cleaned, resterilized by autoclaving, and MG63 cells cultured on them as before. At confluence, the same parameters were measured and cell behavior on new and used disks compared. When confluent cultures of cells on plastic were compared to those cultured on new Ti surfaces, cell number was reduced on the roughest surfaces and equivalent to plastic on the other surfaces. Cell number was further reduced when disks with the roughest surfaces were re-used; no differences in cell number could be discerned after cleaning and resterilization. Cell proliferation was inversely related to surface roughness and was less than seen on tissue culture plastic. Re-use of the Ti disks resulted in no change in cell proliferation rate. Alkaline phosphatase specific activity in isolated cells was lowest on the rougher surfaces; no differences between new and used disks were observed. Similarly, enzyme activity in the cell layer was decreased in cultures grown on rougher surfaces, with no effect of prior disk use being noted. RNA synthesis was decreased with respect to plastic in cultures on smoother surfaces and increased on rougher surfaces; prior disk use did not alter RNA synthesis. Collagen production by the cells was decreased on smoother surfaces, but was comparable to tissue culture plastic when grown on rougher surfaces. Non-collagen protein production was unaffected by culture surface and whether or not the disk had been previously used. Proteoglycan synthesis by cells was decreased on all surfaces studied and comparable on both new and used disks. The results of this study indicate that Ti implant surfaces are unaffected by cleaning and resterilization, although rougher surfaces may require more extensive cleaning than smoother ones. This suggests the possibility that implants, in the same patient, could be safely reused. In vivo studies in animals, however, need to be performed before clinical application can be considered.

Alkaline Phosphatase↗

PubMed1996

Evaluation of an endosseous titanium implant with a sandblasted and acid-etched surface in the canine mandible: radiographic results.

Previous studies have demonstrated in short-term experiments that sandblasted and acid-etched (SLA) titanium implant had a greater bone-to-implant contact than a titanium plasma-sprayed (TPS) implant in non-oral bone. In the present study, an SLA implant was compared radiographically to a TPS implant under unloaded and loaded conditions in the canine mandible for up to 15 months. 69 implants were placed in 6 foxhounds. Standardized radiographs were taken at baseline, preload, 3, 6, 9, and 12 months of loading. Loaded implants were restored with gold crowns similar to the natural dentition. Radiographic assessment of the bone response to the implants was carried out by measuring the distance between the implant shoulder and the most coronal bone-to-implant contact (DIB) and by evaluated of bone density changes using computer-assisted densitometric image analysis (CADIA). 5 different areas-of-interest (AOI) were defined coronally and apically along the implant. DIB measurements revealed that SLA implants had significantly less bone height loss (0.52 mm) than TPS implants (0.69 mm) at the preload evaluation (p = 0.0142) as well as at 3 months of loading (0.73 mm/1.06 mm; p = 0.0337). This difference was maintained between the implant types during the 1-year follow-up period. The same trend was also evident for CADIA measurements with SLA implants showing higher crestal bone density values when comparing preload to baseline data (p = 0.0890) and 3 months to baseline data (p = 0.0912). No measurable bone density changes were apparent in the apical areas of either implant. These results suggest that SLA implants are superior to TPS implants as measured radiographically in oral bone under unloaded and loaded conditions.

Alveolar Bone Loss↗

PubMed1996

Ability of commercial demineralized freeze-dried bone allograft to induce new bone formation.

Demineralized freeze-dried bone allograft (DFDBA) has been used extensively in periodontal therapy. The rationale for use of DFDBA includes the fact that proteins capable of inducing new bone; i.e., bone morphogenetic proteins, can be isolated from bone grafts. Commercial bone banks have provided DFDBA to the dental practitioner for many years; however, these organizations have not verified the osteoinductive capacity of their DFDBA preparations. The aim of this study was to determine the ability of commercial DFDBA preparations to induce new bone formation. DFDBA with particle sizes ranging from 200 to 500 microns was received from six bone banks using various bone production methods. Different lots of DFDBA from the same tissue bank were sometimes available. A total of 14 lots were examined. The surface area of bone particles in each sample was measured morphometrically and the pH of a solution containing the particles after suspension in distilled water determined. Samples from each DFDBA lot were implanted intramuscularly (10 mg) or subcutaneously (20 mg) into three different animals and tissue biopsies harvested after 4 weeks. One sample from each tissue bank was implanted and harvested after 8 weeks. At harvest, each area where DFDBA had been implanted was excised and examined by light microscopy. The ability of DFDBA to produce new bone was evaluated and the amount of residual bone particles measured. The results show that bone particles from all tissue banks had a variety of shapes and sizes, both before implantation and after 1 or 2 months of implantation. The pH of particle suspensions also varied between batches, as well as between tissue banks. None of the DFDBA induced new bone formation when implanted subcutaneously. Intramuscular implants from three banks induced new bone formation after 1 and 2 months. DFDBA from two banks caused new bone formation only after 2 months. However, DFDBA from one bank did not induce new bone at all. Particle size before implantation correlated with particle size after implantation. However, particle size did not correlate with ability to induce bone. The results show that commercial DFDBA differs in both size and ability to induce new bone formation, but that the two are not related. The study also indicates that wide variation in commercial bone bank preparations of DFDBA exist and that ability to induce new bone formation also varies widely. Furthermore, the results suggest that methods or assays for evaluating the ability of DFDBA to induce new bone should be developed and standardized.

Adolescent↗

PubMed1996

Bone cell interactions and regulation by inflammatory mediators.

The loss of alveolar bone tissue associated with periodontal disease appears to be related to local factors that alter the physiologic balance between bone formation and resorption. Physiologic bone metabolism requires the coupled activities of bone resorption and bone formation. Recent investigations of this coupling phenomenon have been directed at understanding the regulatory mechanisms involved in osteoblast-osteoclast interactions. These regulatory mechanisms utilize multiple cytokines, which function in context with numerous other factors, including cell-cell interactions, extracellular matrix molecules, and levels of differentiation. Local alterations of these factors may disrupt the physiologic balance in bone metabolism and lead to the pathologic loss of alveolar bone. Future strategies for altering bone loss found in the periodontal diseases will be directed at modulating the balance of bone resorption and bone formation at the local site.

Alveolar Bone Loss↗

PubMed1995

Effect of titanium surface roughness on proliferation, differentiation, and protein synthesis of human osteoblast-like cells (MG63).

The effect of surface roughness on osteoblast proliferation, differentiation, and protein synthesis was examined. Human osteoblast-like cells (MG63) were cultured on titanium (Ti) disks that had been prepared by one of five different treatment regimens. All disks were pretreated with hydrofluroic acid-nitric acid and washed (PT). PT disks were also: washed, and then electropolished (EP); fine sandblasted, etched with HCl and H2SO4, and washed (FA); coarse sandblasted, etched with HCl and H2SO4, and washed (CA); or Ti plasma-sprayed (TPS). Standard tissue culture plastic was used as a control. Surface topography and profile were evaluated by brightfield and darkfield microscopy, cold field emission scanning electron microscopy, and laser confocal microscopy, while chemical composition was mapped using energy dispersion X-ray analysis and elemental distribution determined using Auger electron spectroscopy. The effect of surface roughness on the cells was evaluated by measuring cell number, [3H]thymidine incorporation into DNA, alkaline phosphatase specific activity, [3H]uridine incorporation into RNA, [3H]proline incorporation into collagenase digestible protein (CDP) and noncollagenase-digestible protein (NCP), and [35S]sulfate incorporation into proteoglycan. Based on surface analysis, the five different Ti surfaces were ranked in order of smoothest to roughest: EP, PT, FA, CA, and TPS. A TiO2 layer was found on all surfaces that ranged in thickness from 100 A in the smoothest group to 300 A in the roughest. When compared to confluent cultures of cells on plastic, the number of cells was reduced on the TPS surfaces and increased on the EP surfaces, while the number of cells on the other surfaces was equivalent to plastic. [3H]Thymidine incorporation was inversely related to surface roughness. Alkaline phosphatase specific activity in isolated cells was found to decrease with increasing surface roughness, except for those cells cultured on CA. In contrast, enzyme activity in the cell layer was only decreased in cultures grown on FA- and TPS-treated surfaces. A direct correlation between surface roughness and RNA and CDP production was found. Surface roughness had no apparent effect on NCP production. Proteoglycan synthesis by the cells was inhibited on all the surfaces studied, with the largest inhibition observed in the CA and EP groups. These results demonstrate that surface roughness alters osteoblast proliferation, differentiation, and matrix production in vitro. The results also suggest that implant surface roughness may play a role in determining phenotypic expression of cells in vivo.

Alkaline Phosphatase↗

PubMed1995

Receptor binding of PDGF-AA and PDGF-BB, and the modulation of PDGF receptors by TGF-beta, in human periodontal ligament cells.

The growth factors PDGF-AA and PDGF-BB have previously been shown to be potent mitogens for human periodontal ligament (hPDL) cells in vitro. Additionally, the mitogenic response to PDGF-AA has been shown to be specifically inhibited by TGF-beta. The purpose of the present investigation was to examine the binding of PDGF-AA and PDGF-BB, and the modulation of PDGF binding by TGF-beta, in hPDL cells. Scatchard analysis identified an average of 32,000 PDGF-AA high-affinity binding sites per cell with a dissociation constant (Kd) of 0.66 nM and an average of 36,000 PDGF-BB binding sites per cell with a dissociation constant (kd) of 0.44 nM. After treatment with TGF-beta, the receptor number for PDGF-AA was found to specifically decrease by approximately 50%, with no change in binding affinity. This reduced number of binding sites was shown to correlate with both a decrease in levels of receptor tyrosine phosphorylation and a decreased number of alpha receptor subunits. Northern blot analysis identified the TGF-beta-mediated decrease in PDGF alpha receptor subunit mRNA levels. PDGF-BB showed little change in the number of binding sites or in the binding affinity with TGF-beta treatment, and the data were consistent with an increase in the number of beta receptor subunits. These results demonstrate nearly equivalent numbers of receptors for both PDGF-AA and PDGF-BB in hPDL cells. Also, modulation of PDGF binding, by TGF-beta, was shown to result in a reduced number of alpha receptor subunits with an increase in the number of beta receptor subunits.

Cells, Cultured↗

PubMed1995

Growth factor effects on the expression of collagenase and TIMP-1 in periodontal ligament cells.

The fibroblast is a prominent cellular component of the periodontal ligament. It is believed to play an important role in collagen metabolism in health and disease. The turnover of collagen in the periodontal ligament is believed to be controlled by the balance between collagen synthesis and degradation. The family of matrix metalloproteinases and their inhibitors is one of the mechanisms which regulates this balance. The factors that regulate the synthesis of collagenase and its inhibitor, TIMP-1, by the periodontal ligament cell are poorly understood. The present study was undertaken to assess the effect of interleukin-1 beta (IL-1 beta), platelet-derived growth factor (PDGF), and transforming growth factor-beta 1 (TGF-beta) on the expression of collagenase (MMP-1) and TIMP-1 mRNA in periodontal derived fibroblasts using reverse transcription polymerase chain reaction (RT-PCR). Early passage periodontal ligament derived fibroblasts were treated with IL-1 beta (10 and 100 pg/ml), two isoforms of PDGF, -AA and -BB (4 and 20 ng/ml) and TGF-beta (1 and 10 ng/ml). Treatment with growth factors from 2 to 24 hours revealed that the largest effects on MMP-1 mRNA occurred after 24 hours. IL-1 beta induced a 5 to 9 fold increase in MMP-1 mRNA. The two isoforms of PDGF had less of an effect (3 to 5 fold) on MMP-1 mRNA whereas TGF-beta induced a 25 to 50% decrease in the expression of this message. None of the growth factors had an effect on TIMP-1 mRNA expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Becaplermin↗

PubMed1994

Periodontal regeneration with polypeptide growth factors.

Attempts at periodontal regeneration have been plagued by inconsistent results. The failures associated with these procedures are likely due to an insufficient number of cells themselves lacking sufficient activity to produce the supporting structures of the periodontium. Molecular studies have provided insight into the regenerative process by identifying locally acting mediators expressed during healing. These mediators, termed growth factors, may stimulate a wide variety of cellular events, including chemotaxis, proliferation, differentiation, and production of extracellular matrix proteins. Thus, the use of polypeptide hormones to enhance regeneration is based on the concept that the effect of the mediators that are naturally present can be enhanced by the addition of exogenous growth factors. Based on information originally obtained from in vitro studies, investigators have recently attempted to enhance bone formation and periodontal regeneration by using growth factors. This review focuses on five growth factor families that have potential for inducing periodontal regeneration based on their ability to stimulate osteoblasts and periodontal ligament cells in vitro or in vivo. These include platelet-derived growth factor, insulin-like growth factor, transforming growth factor-beta, fibroblast growth factor, and bone morphogenetic protein.

Animals↗

PubMed1993

The effect of conditioned medium from connective tissue fibroblasts and epithelium on calcium release from mouse calvarial organ culture.

Fibroblasts from periodontal ligament and gingival explants were cultured in vitro. The conditioned media from four different periodontal ligament and four gingival explant cultures were examined to determine their effect on calcium release in mouse calvarial organ culture. All the cultures stimulated calcium release, with a range of 20.6-43% over control. Conditioned media from two periodontal ligament cultures and a gingival culture significantly stimulated calcium release from the bone organ culture. The stimulatory activity in the oral fibroblasts cell cultures was compared to that in conditioned medium from two non-oral, established, fibroblasts cell lines and an epidermal keratinocyte cell line. Similar to the oral fibroblast cultures, conditioned medium from all three cell lines resulted in stimulation of calcium release in the bone culture assay. In order to characterize the bone-stimulating activity, a 0.4 micron membrane was used to separate the cell cultures from the bone organ culture. Both gingival and periodontal ligament fibroblast cultures gave values for calcium release significantly less than control when the separating membrane was used. Both non-oral cell lines and the epidermal keratinocyte cell line gave values for calcium release similar to those when no membrane was used. These results suggest that oral fibroblasts, but not non-oral fibroblasts and epidermal keratinocytes, release a unique bone-resorption stimulating activity.

3T3 Cells↗

PubMed1993

Effects of platelet-derived growth factor isoforms on calcium release from neonatal mouse calvariae.

Platelet-derived growth factor (PDGF) is the major growth factor in serum for cells of mesenchymal origin and induces many different activities, including bone resorption. Since the initial report that PDGF stimulated calcium release from bone organ cultures, it has been shown that PDGF is a dimeric protein consisting of two disulfide bonded polypeptides encoded by different genes. Three isoforms of the two gene products have been isolated. We compared the capacity of each isoform to stimulate calcium release from radiolabeled mouse calvariae. PDGF-AB from human platelets and recombinant PDGF-BB isoforms significantly stimulated calcium release at 5 ng/ml, but not in lower doses. Recombinant PDGF-AA did not induce calcium release. Indomethacin blocked the stimulated bone resorption, suggesting a prostaglandin-mediated mechanism of action. PDGF-induced calcium release was compared to TGF-beta 1 in the organ culture system. Approximately a 10-fold greater concentration of PDGF-AB and PDGF-BB was required to achieve a similar degree of calcium release as found in TGF-beta 1 treated calvariae. Thus, TGF-beta 1, PDGF-AB, and PDGF-BB significantly stimulated calcium release from mouse calvariae. This response is specific in that PDGF-AA did not stimulate calcium release.

Animals↗

PubMed1993

Mitogenic effects of growth factors on human periodontal ligament cells in vitro.

Periodontal regeneration is thought to require the migration and proliferation of periodontal ligament cells. Evidence suggests that the polypeptide growth factors PDGF, IL-1, and TGF-beta are mediators of these cellular events in wound healing. The purpose of this study was to determine the effects of these growth factors on human periodontal ligament (PDL) cell mitogenesis, and to identify the regulatory influences of TGF-beta on the response to PDGF and IL-1. Confluent, quiescent human PDL cells were cultured in vitro and treated with the polypeptide growth factors PDGF-AA and -BB, IL-1 beta, and TGF-beta in both a dose and time-dependent manner. Mitogenic activity, as a measure of proliferative potential, was determined by the quantitation of 3H-thymidine incorporation during DNA synthesis. The results of this study demonstrated that both PDGF-AA and -BB enhance mitogenic activity in a dose-dependent manner over a concentration range of 1.0 to 50.0 ng/ml. IL-1 beta (0.01 to 1.0 pM) resulted in no mitogenic enhancement, and at high concentrations (10.0 to 100.0 pM) demonstrated an inhibitory effect. TGF-beta produced a significant increase (P < 0.01) in mitogenic activity (although relatively much less than PDGF) in a delayed, bimodal, dose-dependent manner over a concentration range of 0.01 to 20.0 ng/ml, with a maximal response at a concentration of 1.0 ng/ml. Additionally, incubation with TGF-beta at 1.0 ng/ml prior to the addition of PDGF significantly enhanced (P < 0.01) the mitogenic response to both PDGF-AA and PDGF-BB.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1993

Augmentation of osseous tissue around nonsubmerged endosseous dental implants.

The placement of one-stage endosseous dental implants and the achievement of success rates greater than or equal to two-stage implants present a unique challenge for combining regeneration and implant placement. This report describes the evolution of a technique in which membrane barrier technology is combined with implant placement. This allows healing to occur with minimal inflammation around the one-stage implant and provides an extended, complication-free healing period for both osseous regeneration and implant integration. Present membrane technology requires a second surgical procedure to remove the membrane, but future resorbable membranes, when available, should make regeneration around one-stage implants a relatively simple clinical procedure.

Alveolar Ridge Augmentation↗

PubMed1991

Biologically active mediators: platelet-derived growth factor, monocyte chemoattractant protein-1, and transforming growth factor-beta.

The advent of tissue culture techniques provided efficient means to measure the activities of hormones that act at very low concentrations. By following a specific activity, biologically active mediators could then be efficiently purified from impure starting materials. Different assay systems allowed the purification of different types of factors. Growth-inducing factors, such as platelet-derived growth factor, were discovered because they could stimulate DNA synthesis in vitro. Chemotactic factors, such as monocyte chemoattractant protein-1, were discovered based on their capacity to stimulate migration of cells in vitro. Transforming growth factors were originally described because of their capacity to stimulate the growth of nontransformed cells in soft agar. This review describes the effects of biologically active mediators using platelet-derived growth factor, monocyte chemoattractant protein-1, and transforming growth factor-beta as examples.

Animals↗