Biomedical subjects

Georg Watzek

Publications and source records attributed to Georg Watzek.

At least 37 records · Page 2Linked to original sources

PubMed2004

Platelet-released supernatants increase migration and proliferation, and decrease osteogenic differentiation of bone marrow-derived mesenchymal progenitor cells under in vitro conditions.

Platelet-rich plasma is currently promoted to serve as an adjuvant for bone grafts to enhance quantity and quality of newly forming bone; however, the underlying cellular mechanisms are not fully understood. We show here that supernatants of leukocyte-depleted thrombin-activated platelets increase migration and proliferation, and decrease osteogenic differentiation of bone marrow-derived mesenchymal progenitor cells under in vitro conditions. Using neutralizing antibodies raised against platelet-derived growth factor (PDGF), the observed effects of platelet-released supernatants were diminished. The mitogenic response was also decreased when extracellular signal-regulated protein kinase (ERK) signalling was inhibited by PD98059; however, PD98059 did not reverse the effects of platelet-released supernatants on migration and osteogenic differentiation. Consistent with an ERK-mediated mitogenic activity, incubation of serum-starved mesenchymal cell progenitors with platelet-released supernatants increased phosphorylation of the kinase. Together, these observations indicate that PDGF is a key factor released upon platelet activation that can increase migration and proliferation, and decreases osteogenic differentiation of mesenchymal progenitor cells under in vitro conditions. The results further suggest that ERK signalling is required to mediate the mitogenic response to platelet-released supernatants.

Adult↗

PubMed2004

Histomorphometrical and clinical comparison of submerged and nonsubmerged implants subjected to experimental peri-implantitis in dogs.

OBJECTIVES: Soft and hard tissue healing around submerged and nonsubmerged versions of one dental implant design was evaluated in an experimental canine peri-implantitis model. MATERIAL AND METHODS: Forty-eight c.p. Ti-implants with integrated (one-piece=OPI) or screw-on (two-piece=TPI) abutments were inserted in edentulous mandibles of eight beagle dogs, one OPI and one TPI with connected abutments for nonsubmerged and one TPI without abutment (SMI) for submerged healing. After 3 months, all implants were functionally loaded, and at 4 months peri-implantitis was ligature-induced in one jaw side. Intravital polyfluorochrome labeling, monthly conventional radiography and gingival probing of all 48 implants were performed until sacrifice 8 months postimplantation. Undecalcified ground sections in the bucco-lingual and mesio-distal planes of four dogs (23 implants, one implant lost) were evaluated by light and fluorescence microscopy. The immunohistochemical and SEM-vascular corrosion cast results of the four other dogs (24 implants) will be reported elsewhere. Levels of alveolar bone-to-implant contact (ABICL), alveolar crest (ACL) and junctional epithelium-to-implant contact were determined by computer-assisted histometry. Peri-implant alveolar bone loss (=saucerization) was assessed on the radiographs and calculated as ACL minus ABICL from histometric data. RESULTS: Around SMIs and OPIs without ligature less plaque adhesion and lower gingival indices were found when compared to TPIs. Radiologically, all ligatured, but also some nonligatured implants showed alveolar bone loss. Histometry demonstrated reduced ABICL around all these implants. Saucerization was more pronounced on the lingual and mesio-distal sides. Particularly around TPIs, bone resorption was still active or bone formation was impaired on fluorochrome labeling. Only around SMIs and one OPI without ligature continuing alveolar bone formation reflected by gains in ABICL were found. CONCLUSION: The clinical and histometric results of this study demonstrate that healing of submerged SMIs was not impaired by the two-stage procedure, resulting in equally good healing as around nonsubmerged OPIs. However, peri-implantitis plaque-induced by ligature and/or dilated abutment connection microgaps in TPIs affected alveolar bone-to-implant contacts more than transmucosal or submerged healing mechanisms.

Alveolar Bone Loss↗

PubMed2004

Novel development for intraoral distraction osteogenesis by individually fabricated traction prostheses.

Modified fixed or removable partial dentures are used for intraoral distraction osteogenesis. These traction prostheses rest on teeth or endosseous implants and direct distraction forces to an endosseous implant in the osteotomy segment. This article explains the fabrication and function of custom-made traction prostheses for 1-, 2- and 3-dimensional distraction osteogenesis.

Dental Abutments↗

PubMed2004

Porcine sinus mucosa holds cells that respond to bone morphogenetic protein (BMP)-6 and BMP-7 with increased osteogenic differentiation in vitro.

The aim of this in vitro study was to determine whether the sinus mucosa holds cells with an osteogenic potential. Frozen sections of sinus mucosa from three adult pigs were investigated for the expression of STRO-1, a marker of mesenchymal progenitor cells, and alkaline phosphatase activity, an enzyme expressed by cells committed to the osteogenic lineage and by mature osteoblasts. To determine their osteogenic potential, mucosa-derived cells were incubated with bone morphogenetic protein (BMP)-6 and BMP-7, and alkaline phosphatase activity, osteocalcin expression, and mineralization of the extracellular matrix was measured. We found sinus mucosa cells staining positive for STRO-1 and alkaline phosphatase activity. When sinus mucosa tissue was placed in culture, alkaline phosphatase positive cells grew out from the explants and further increased alkaline phosphatase activity in response to BMP-6 and BMP-7. The expression level of the osteoblast-specific extracellular matrix protein osteocalcin, and the amount of calcium accumulation within the extracellular matrix was also increased in response to BMPs. We conclude that the sinus mucosa holds mesenchymal progenitor cells and cells committed to the osteogenic lineage that can respond to BMP-6 and BMP-7 by an increase of their osteogenic differentiation.

Alkaline Phosphatase↗

PubMed2004

Bone formation following sinus grafting with autogenous bone-derived cells and bovine bone mineral in minipigs: preliminary findings.

Bone formation in a sinus grafted with a cell-free scaffold requires the presence of local progenitor cells that differentiate into osteoblasts. The purpose of this study was to examine the effect of culture expanded autogenous bone-derived cells (ABC) with bovine bone mineral (BBM) on bone formation after single-stage sinus grafting in minipigs. Bone biopsies from the iliac crest were harvested 4 weeks prior to sinus grafting and ABC were culture expanded in vitro. The sinuses of five adult minipigs were grafted. In one sinus of each minipig the space between Schneider's membrane (SM) and the sinus wall was grafted with ABC (325,000 cells per sinus, on average) and BBM. In the other sinus, BBM alone was used. The animals were sacrificed after 12 weeks. One block of each grafted area was prepared by saw cutting and the amount of newly formed bone was analysed by micro-computed tomography (mu-CT). The addition of ABC to BBM significantly increased the amount of newly formed bone compared with BBM alone on mu-CT analysis (ABC+BBM: 29.86+/-6.45% vs. BBM: 22.51+/-7.28% (P=0.016)). Bone formation was increased near SM (ABC+BBM: 20.7+/-4.5% vs. BBM: 15.43+/-3.62% (P=0.009)) and in the middle zone of the grafting material (ABC+BBM: 31.63+/-7.74% vs. BBM: 22.5+/-7.91% (P=0.001)), but not near the local host bone (ABC+BBM: 37.23+/-8.23% vs. BBM: 28.42+/-12.54% (P=0.15)). These preliminary findings indicate that supplementation of cell-free grafting material with culture expanded ABC can stimulate bone formation in areas with low bone-forming capacity.

Animals↗

PubMed2004

Effect of platelet-released growth factors and collagen type I on osseous regeneration of mandibular defects. A pilot study in minipigs.

OBJECTIVE: To study the effects of platelet-released growth factors (PRGF) and collagen type I on bone defect healing in minipig mandibles. MATERIAL AND METHODS: In eight adult minipigs defects were trephined in the facial mandibular wall from extra-oral and filled with collagen+PRGF or with collagen alone. Control defects were left untreated. PRGF were defined as the supernatants obtained after centrifugation of washed, thrombin-activated allogenic cells of platelet-rich plasma. The animals were sacrificed at 4 and 8 weeks. For histological analysis, undecalcified ground specimens stained with the Levai-Laczko stain were used. RESULTS: For the entire follow-up, the amount of newly formed bone was 35.49 +/- 3.84% in the collagen+PRGF group, 46.34 +/- 3.84% in the collagen-only group and 33.83 +/- 4.11% in the controls. The differences between the collagen+PRGF and the collagen-only group (p = 0.0343), and between the collagen-only group and the controls (p = 0.0305) were significant. Histologically, defects filled with collagen+PRGF showed inflammatory reactions at 4 weeks, and new bone formation near the remnants of the filler collagen was reduced. CONCLUSION: The data suggest that collagen type I alone, but not its combination with PRGF can support the early stages of cortical bone repair.

Animals↗

PubMed2004

Platelet-released supernatant increases matrix metalloproteinase-2 production, migration, proliferation, and tube formation of human umbilical vascular endothelial cells.

BACKGROUND: Local application of platelets represents a promising tool to enhance bone regeneration. New bone formation strictly requires blood vessel formation, a sequential process involving matrix degradation, migration, proliferation, and tube formation of endothelial cells. Here we investigated the impact of secreted granula products from activated platelets on endothelial cells, and determined the involvement of extracellular signal-regulated kinase (ERK) signaling. METHODS: The effects of platelet-released supernatant on endothelial cells were investigated using in vitro models. Matrix metalloproteinase-2 (MMP-2) release, migration, proliferation, and tube formation of human umbilical vascular endothelial cells (HUVEC) were determined in response to platelet-released supernatant by gelatine zymography, Boyden chamber assay, 3[H]thymidine incorporation, and basement membrane assay, respectively. All experiments were performed in the presence of the ERK signaling inhibitor PD98059. ERK phosphorylation was detected by Western blot analysis. RESULTS: Incubation with platelet-released supernatant increased the production of MMP-2, migration, proliferation, and tube formation of HUVEC. Platelet-released supernatant also stimulated ERK phosphorylation in HUVEC. Inhibition of ERK signaling decreased platelet-released supernatant-stimulated endothelial cell proliferation, but not MMP-2 activity, migration, and the formation of capillary tubes. CONCLUSIONS: Our data suggest that secreted granula products from platelets can enhance different stages of blood vessel formation, and that ERK signaling is required to mediate the mitogenic effects of the supernatant. These findings support the hypothesis of a potential link between platelet activation and blood vessel formation during bone regeneration.

Basement Membrane↗

PubMed2003

Platelets are mitogenic for periosteum-derived cells.

The early stages of bone regeneration are associated with a high mitogenic activity of periosteal cells. Here we addressed the question of whether platelets that accumulate within the developing haematoma can account for this tissue response. Addition of platelets, platelet-released supernatants, platelet membranes, and microparticles to bovine periosteum-derived cells resulted in an increase in 3H-thymidine incorporation; lipid extracts had no effect. Platelet-released supernatants retained their activity after incubation at 56 degrees C, but not at 100 degrees C. Gel chromatographic analysis revealed the highest mitogenic activity at approximately 35 kD. Of the factors released from activated platelets, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) increased 3H-thymidine incorporation. The mitogenic activity of platelet-released supernatants was decreased by anti-PDGF, and anti-bFGF antibodies. Platelet-released supernatants increased the number of proliferating periosteum-derived cells as determined by the expression pattern of Ki67. Platelet-released supernatants also resulted in a stimulation of cell proliferation in periosteal explants. These results suggest that platelets have the potential to stimulate the mitogenic response of the periosteum during bone repair.

Animals↗

PubMed2003

The stable analog carbocyclic TXA2 but not platelet-released TXA2 induces osteoclast-like cell formation.

Thromboxan A(2) (TXA(2)) is the main product of arachidonic acid metabolism in activated platelets. Platelet-released supernatants (PRS) can induce osteoclast-like cell formation in murine bone marrow cultures via a cyclooxygenase (COX)/receptor activator of NF-kB-ligand (RANKL)-dependent pathway. Here we investigated a possible linkage between platelet-released TXA(2) and osteoclastogenesis. The stable analog of TXA(2), carbocyclic TXA(2) (CTXA(2)) can induce the formation of tartrate-resistant acid phosphatase positive multinucleated cells in murine bone marrow cultures via a RANKL-dependent pathway and requires the presence of stromal cells. Interestingly, the platelet-released instable TXA(2) does not account for osteoclastogenic effects as: (a) PRS-induced osteoclastogenesis in the presence of the TXA(2) receptor antagonist SQ29548; (b) inhibition of platelet TXA(2) synthesis by indomethacin and acetylsalicylic acid failed to decrease the osteoclastogenic potential of the corresponding supernatants; and (c) CTXA(2)-induced osteoclast-like cell formation independent of indomethacin and the selective COX-2 inhibitor NS398.

Acid Phosphatase↗

PubMed2003

A preliminary study of monocortical bone grafts for oroantral fistula closure.

Sinus floor elevation has become a standard procedure in patients affected by severe maxillary atrophy, before implant placement, provided that the maxillary sinus is intact and uninfected. In the case of an oroantral fistula, simple soft tissue closure may interfere with the process of elevating the Schneiderian membrane. Total regeneration of the bony sinus floor is necessary to prevent disruption of the sinus membrane. In this study, 5 patients with oroantral fistulae of different causes were treated with autogenous monocortical bone blocks harvested from the chin. Press-fit closure for bony repair of the basal maxilla was sufficient in 3 of them. Two patients needed additional internal graft fixation. In the meantime, the 3 aforementioned patients underwent a successful sinus lift procedure. The use of a monocortical bone block for the closure of an oroantral fistula is recommended before internal sinus augmentation.

Adult↗

PubMed2003

Sinus grafting with autogenous platelet-rich plasma and bovine hydroxyapatite. A histomorphometric study in minipigs.

In this study, bovine hydroxyapatite (HA) alone or in combination with activated platelet-rich plasma (PRP) was examined for its usefulness for single-stage sinus grafting in minipigs. In 12 adult minipigs, Schneider's membrane of 24 sinuses was elevated bilaterally through an extra-oral approach. The material was divided into two groups of 12 sinuses. In one of these groups, the space between Schneider's membrane and the sinus wall was grafted with activated autogenous PRP and HA (PRP side). In the other, HA alone was used for grafting (control side). At the same time two dental implants with a machined surface were inserted into the grafting material through the facial sinus wall. Four animals of each group were sacrificed at 3, 6 and 12 weeks, and undecalcified thin-cut and ground sections (Donath 1988) stained with toluidine blue were prepared. In the facial sinus wall, fewer bone-to-implant contacts were present on the PRP side at 3 and 6 weeks than on the control side. At 12 weeks, the PRP side had caught up with the control side. In grafted bone, contacts on the PRP side were more extensive than on the control side at 3 weeks, had dropped below control side levels at 6 weeks and surpassed these at 12 weeks. This study showed that PRP has a differential effect on osseointegration in grafted bone and local host bone. Combined with HA it was not demonstrably superior to HA alone.

Alveolar Ridge Augmentation↗

PubMed2003

Representative marketing-oriented study on implants in the Austrian population. I. Level of information, sources of information and need for patient information.

The number of dental implants inserted annually worldwide has been estimated to come close to a million. But the level of information available to patients about realistic, evidence-based treatment options by implants is often enough more than fragmentary, and what is disseminated by the media and the industry does not always reflect evidence-based empirical data. This survey of 1000 adults presented with 18 questions was designed to shed light on several points. These were (1). level of subjective patient information, (2). sources of information and prejudices, (3). future demand for implant treatment and target groups for patient information campaigns, and (4). potential misinformation, information deficits, discrepancies of information and how these come about. Of those questioned, 20% said unprompted that implants were a possibility to replace missing teeth. When prompted, 72% said that they knew about dental implants. Most of those questioned felt poorly informed about the options for replacing missing teeth and many knew less about implants than about other alternatives. The dentist was said to be the desired source of information, but 77% of those questioned reported that their dentists did not practice implant dentistry. More than 79% of those questioned did not know whether their dentist worked with implants. Forty-four percent thought that implants should only be placed by specially trained doctors. Sixty-one percent were of the opinion that dentists who provide implant dentistry were better qualified than their nonimplanting colleagues. Half of those questioned attributed implant failures to allergies and incompatibilities, the other half to poor medical care. Only 29% incriminated poor oral hygiene as a cause of implant failure. Future strategies should be geared to more professional public relations and patient information. Internationally operating qualified implant institutions could contribute much to balance discrepant information.

Adolescent↗

PubMed2003

Representative marketing-oriented study on implants in the Austrian population. II. Implant acceptance, patient-perceived cost and patient satisfaction.

Oral implantology is an established subspecialty of restorative dental and oral surgery. While an extensive body of evidence on the fundamentals of osseointegration and associated factors has been published, marketing-oriented analyses based on representative public opinion polls of implant acceptance, patient-perceived cost and patient satisfaction are scarce. In this study, an attempt was made to address these points by questioning a representative sample of 1000 adults in the household setting. The interviewees were presented with 14 questions. Of those familiar with implants as one of the treatment alternatives, 61% reported they would accept implants if the need arose. Implant acceptance was highest among males and interviewees below the age of 30 years. The interest in implants increased with increasing family incomes. Four percent of those questioned already had implants. Twenty-five percent knew someone who had undergone implant treatment. All those questioned found implant-supported rehabilitation to be very expensive. Many of them blamed the dentists for the high cost. One detail was particularly evident: satisfaction among implanted patients was clearly higher than satisfaction rates perceived by them from what they were told about implants by others. First-hand experiences with implants proved to be less biased than reported second-hand information.

Adolescent↗

PubMed2003

Osseous healing characteristics of three different implant types.

The macroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. The aim of this study was to perform a histologic and histomorphometric comparison of the healing characteristics of anodically modified, machined and hydroxyapatite (HA)-coated implant types. A total of 24 machined surface implants (MSI), 24 HA-coated implants (HCI) and 24 anodized titanium surface implants (ASI) were inserted into the mandibles of 12 adult mini-pigs after extracting all mandibular premolars. Four animals each were killed after covered healing for 3, 6 and 12 weeks. Undecalcified ground sections were subjected to histologic and histomorphometric examinations. Primary effects and interactions were statistically evaluated and least square means (Tukey test) were compared. Histologic evaluations showed broad-based bone apposition to HA-coated and anodically roughened surfaces as well as narrow bone contacts to the machined surface. Localized resorption was only observed with the HA-coated implants. Overall, histomorphometric evaluation of bone-to-implant contact percentages for all observation periods showed significant differences between MSI (19.39% +/- 4.53) and HCI (39.05% +/- 4.53; P = 0.0092) and between MSI and ASI (42.72% +/- 4.20; P = 0.0011). In conclusion, the results of this study show that an anodically roughened implant may provide a similar rate of bone-to-implant contact as a HA-coated implant. In the presence of bone quality II to IV, according to Lekholm & Zarb (1985, in: Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago: Quintessence Publishing), this may be of particular benefit, possibly because of higher stability, in maintaining pre-implantation functional strength after implant healing.

Animals↗

PubMed2003

Effects of sinus lifting on voice quality. A prospective study and risk assessment.

A variety of potential complications associated with sinus lift surgery have been reported in the literature. However, potential alterations of voice quality following sinus elevation have so far not been mentioned or evaluated scientifically. For the majority of patients, slight changes of the voice pattern are of no importance. However, for voice professionals, whose voices have become part of their distinctive profession or trademark, minimal changes may have dramatic consequences. This specific group of patients, such as speakers, actors and singers, depend on the particular quality and timbre of their voice for their livelihood. Consequently, the purpose of this study was to assess the effects of sinus lifting on voice quality in the above patient group. In a collaborative interdisciplinary effort, the Departments of Oral Surgery and Otorhinolaryngology, Section of Phoniatrics and Logopedics, thoroughly evaluated a series of voice parameters of four patients undergoing sinus lifting pre- and postoperatively. The parameters analyzed included pitch, dynamic range, sound pressure level, percent jitter, percent shimmer and noise-to-harmonics ratio with special emphasis on formant analysis. No changes were detected in any of the commonly evaluated parameters. These were rated subjectively by patients and their friends or relatives and objectively with instrumental tools under isolated phoniatric lab conditions. In conclusion, sinus lift surgery appears to be a safe, predictable evidence-based method for regenerating the highly atrophic posterior maxilla, which does not jeopardize the individual characteristic voice pattern of high-profile patients critically dependent on their voices for their livelihood.

Adult↗

PubMed2002

A long-term follow-up of 76 Bränemark single-tooth implants.

In a previous study (Haas et al. 1995), we reported on preliminary results of 76 Brånemark implants placed in 71 patients with single-tooth gaps. The present study examines the results of the same group over a longer period of time: 55 implants were followed for more than 5 years, 12 for a period between 4 and 5 years and 1 implant for 46 months. One patient died 3 years after implant placement. Five patients lost their implant within 24 months after insertion. The drop-out rate was 2 implants in 2 patients. The recall rate was thus 97%. Of the 5 implant failures, 2 were located in the maxilla and 3 in the mandible. The Kaplan-Meier survival probability was 93% after 120 months. 74% of the sites showed healthy peri-implant soft tissue conditions. At 15 implants (22%) a bone resorption of more than 2 mm was observed on intraoral radiographs. The mean bone resorption was 1.8 mm in the maxilla and 1.3 mm in the mandible and did not increase with time (Pearson correlation coefficient: r = -0.06, P = 0.59). Abutment loosening occurred in 7 implants (10%), however all abutments that were fixed with a defined torque subsequently remained stable. Thus the favourable preliminary results could be maintained over an average 66 months, indicating that if implant loss happens it seems to occur during the first 2 years after insertion.

Adult↗

PubMed2002

Freeze-dried homogeneous and heterogeneous bone for sinus augmentation in sheep. Part I: histological findings.

Freeze-dried bone has been reported to possess an osteogenetic potential, i.e. to be osteo-inductive or osteoconductive depending on the grafted site. In this animal study homogeneous demineralized freeze-dried bone from the sheep (s-DFDB) and heterogeneous human demineralized freeze-dried bone (h-DFDB) used for single-stage sinus elevation were examined for their potential to improve bone-to-implant bonding. In 72 sinuses of 36 adult female mountain sheep Schneider's membrane was elevated from the local bone through an extra-oral approach and two cylindrical plasma-flame sprayed titanium implants were inserted in the lateral wall of each sinus. At the same time 18 sinuses were reinforced with s-DFDB, another 18 with h-DFDB and yet another 18 with autogenous cancellous bone from the iliac crest. In 18 animals the subantral space remained ungrafted. At each follow-up date, i.e. at 12, 16 and 26 weeks, 12 animals were re-examined and one randomly selected implant from each sinus was analyzed histologically and histomorphometrically. With both s-DFDB and h-DFDB extensive fragmentation and disintegration were seen side by side with sporadic areas of remineralization. These were mainly located in the vicinity of the local host bone and coalesced over time to be ultimately replaced and consolidated by woven bone. But most of the h-DFDB/s-DFDB particles continued to be embedded in abundant collagenous connective tissue and were surrounded by mononucleated and multinucleated giant cells, ultimately causing extensive resorption. The mean bone-to-implant contact length was 16.4% of the implant surface for s-DFDB, 16.9% for h-DFDB, 32.8% for autogenous bone and 22.2% in ungrafted controls. In the autogenous bone group the mean bone-to-implant contact length progressively increased with increasing contact time. In the control group, by contrast, the mean bone-to-implant contact length initially increased in the first two follow-up periods, but dropped again at 26 weeks. Both in the h-DFDB and the s-DFDB group the percent bone contact area was lower at 16 weeks than at 12 weeks but increased again by 26 weeks. In apical implant sections, s-DFDB produced significantly less bone-to-implant contact than autogenous cancellous bone from the iliac crest. In basal implant sections, both DFDB-grafted groups did significantly less well than the two control groups. The results of this experimental study showed that DFDB homografts and heterografts cannot be recommended alone instead of cancellous autografts from the iliac crest for augmenting the maxillary sinus in single-stage sinus elevations. Longer follow-up times than in the present study may perhaps show better results at the bone-implant interface.

Alveolar Ridge Augmentation↗

PubMed2002

Platelets stimulate proliferation of bone cells: involvement of platelet-derived growth factor, microparticles and membranes.

Platelets have been implicated in accelerated bone regeneration in grafting applications. The beneficial effects of platelets may involve their ability to stimulate the proliferation of osteoblasts. We therefore determined the mitogenic response of human trabecular bone-derived cells to human platelets and supernatants of thrombin-activated platelets. We can show a approximately 50-fold increase in DNA-synthesis of bone cells (BC) cultured in the presence of platelets as determined by [3H]-thymidine incorporation. Preventing cell-to-cell contact by a membrane filter did not abrogate the stimulatory effect, indicating the release of soluble factor(s) that are mitogenic for BC. The lipid fraction of the platelets had no effect on [3H]-thymidine uptake into the DNA of BC. Platelet-released supernatant (PRS) increased the rate of [3H]-thymidine incorporation to approximately 20-fold and retained 56% of their activity after incubation at 56 degrees C, and 27% at 100 degrees C, respectively. Neutralizing antibodies raised against platelet-derived growth factor (PDGF) partially suppressed the mitogenic potential of PRS. Gel exclusion chromatography analysis showed that molecules ranging from 25 kDa to more than 70 kDa within the PRS can stimulate BC proliferation. The highest amount of PDGF was detected in fractions corresponding to a molecular weight of 28-37 kDa as determined by immunoassay. The mitogenic activity was not restricted to soluble growth factors because microparticles in the PRS and platelet membranes also increased BC proliferation. Our data indicate that native platelets, the respective PRS, microparticles, and platelet membranes can stimulate the mitogenic activity of BC, thereby contributing to the regeneration of mineralized tissue.

Aged↗