Biomedical subjects

J L Saffar

Publications and source records attributed to J L Saffar.

At least 37 records · Page 2Linked to original sources

PubMed1996

Minocycline impairment of both osteoid tissue removal and osteoclastic resorption in a synchronized model of remodeling in the rat.

In addition to their antibacterial effects, tetracyclines may inhibit interstitial collagenase activity and bone resorption. These properties were assessed morphometrically using minocycline (25 and 50 mg/kg/day given by the IM route) in a rat model of synchronized remodeling in which osteoclastic resorption peaks 4 days after the activating event (the extractions of the upper molars) along the antagonist mandibular cortex, a zone undergoing physiologically active formation. During the first 2 days of activation, minocycline at the two doses impaired very significantly the disorganization of both the osteoid seam and the layer of osteoblasts, a prerequisite to give osteoclasts access to the mineralized bone surface. The number of readily identifiable osteoblasts decreased slightly during this period, suggesting that minocycline prevented their transformation into lining cells. Their synthetic activity, as estimated by the size of the cells and their nucleus, appeared relatively preserved too, mostly with the higher dose. AT the peak of osteoclasia, the bone surfaces undergoing remodeling were significantly decreased in the minocycline-treated groups. The resorption surface was reduced (P < 0.0003) as well as the number of osteoclasts (P < 0.0007), which were also significantly smaller. Their resorbing activity was dramatically affected as well: they excavated lacunae whose area was significantly reduced by over 70%. In addition, formation was still a prominent activity in the treated animals. These data are compatible with the inhibition at the early stages of activation of an osteoblast-secreted collagenase whose action may be the elimination of the osteoid seam. The inhibition of an osteoclast collagenase and/or of a bone matrix bound-collagenase may be responsible for the reduction in lacunar size. A direct effect of minocycline on osteoclast resorptive activity may also participate in the low resorption profile, as tetracyclines are known to interfere with the intracellular [Ca2+].

Animals↗

PubMed1996

Calbindin-D9k and calbindin-D28k expression in rat mineralized tissues in vivo.

Following their terminal differentiation, highly specialized cells, ameloblasts, odontoblasts, and osteoblasts sequentially elaborate mineralized tissues. While the developmental expression pattern of matrix proteins has been studied extensively, less attention has been paid to the molecules involved in calcium handling, such as calcium-binding proteins. This shortcoming, as well as previous conflicting data, led us to conduct studies on calbindin-D9k and calbindin-D28k in rat mandibular bone and incisor based on several methods established on rat ameloblasts in vivo. Radioimmunoassays showed that calbindin-D28k accounts for approximately 0.1% of cytosolic proteins in the ectomesenchymal fraction and 1% in the epithelial fraction of the rat incisor and is 100-fold more concentrated than calbindin-D9k in both tissue types. Western blot analysis confirmed that the anticalbindin-D28k reactive species corresponded to the well characterized renal calbindin-D28k in the ectomesenchyme. In this tissue, calbindin-D28k was ultrastructurally immunolocalized in the odontoblasts. Quantitative immunocytochemistry showed that labeling was distributed throughout their nucleus and cytoplasm. The similar cytoplasmic distribution of both calbindin-D proteins and mRNAs suggests that their expression is regulated at the subcellular level. In particular, immunoreactive calbindin-D28k appeared to be associated with rough endoplasmic reticulum. Calbindin-D9k antisense probe showed negligible labeling in odontoblasts, in parallel with the protein quantities measured (approximately 10 ng/mg of total protein). Finally, in situ hybridization showed transcripts for both calbindins-D in ameloblasts and also in osteoblasts. In summary, the present results support the concept that an elevated expression of these vitamin D-dependent calcium-binding proteins may characterize the phenotype of cells directly involved in the elaboration of mineralized tissues, enamel, dentine, and bone.

Age Factors↗

PubMed1995

Multinucleated giant cells elicited around hydroxyapatite particles implanted in craniotomy defects are not osteoclasts.

BACKGROUND: The nature of the multinucleated giant cells (MNGC) elicited in contact with implantable biomaterials is still indecisive. METHOD: In Wistar rats the MNGC recruited after the implantation of hydroxyapatite (HA) particles in standardized skull defects were examined morphologically (at both the light and electron microscope levels), enzymatically (tartrate-resistant acid phosphatase and non-specific esterase), and after a challenge with salmon calcitonin. RESULTS: The MNGC were of great size and contained abundant mitochondria, vacuoles, and vesicles throughout the cytoplasm; they were either tightly apposed to the HA surface or had long and thin processes penetrating the material. When processed for tartrate-resistant acid phosphatase, only a few cells were weakly stained. The staining was totally suppressed when samples were pretreated with cyanuric chloride in the MNGC but not in the host osteoclasts. Calcitonin induced the withdrawal of the host osteoclasts from the bone surface while the MNGC remained in contact with the HA material. CONCLUSION: The MNGC recruited to HA particles did not exhibit the morphologic, enzymatic and functional characteristics of the osteoclasts, and consequently must be regarded as macrophage polykaryons.

Acid Phosphatase↗

PubMed1995

Heparan-like molecules induce the repair of skull defects.

Heparin-binding growth factors (HBGFs) are known to stimulate bone repair when applied to bone lesions. Nevertheless, successful treatments are obtained with high protein doses since HBGFs are rapidly degraded in situ by multiple proteolytic activities associated with the inflammatory period of tissue healing. Like heparin or heparan sulfates, heparan-like molecules, named carboxymethyl-benzylamide-sulfonated dextrans (CMDBS), are known to potentiate fibroblast growth factor activities by stabilizing them against pH, thermal or proteolytic denaturations, and by enhancing their binding with cell surface receptors. We have postulated that CMDBS stimulate in vivo bone healing by interacting with endogenous HBGFs, spontaneously released in the wounded site. The effect of CMDBS on bone repair was studied in a skull defect model in rats by computer-assisted radio-morphometry and histomorphometry. Single application of CMDBS in a collagen vehicle to skull defects induced a dose-dependent increase in bone defect closure and new bone formation after 35 days. Complete bony bridging occurred in defects treated with 3 micrograms CMDBS, whereas bone formation was not observed in vehicle-treated defects which contained only dense fibrous connective tissue between the defect margins. These results indicate that heparan-like molecules, such as CMDBS, are able to induce bone regeneration of skull defects. This action is possibly mediated by potentiation of endogenous growth factor activities and/or by neutralization of proteolytic activities.

Animals↗

PubMed1995

The 5-lipoxygenase inhibitor BWA4C impairs osteoclastic resorption in a synchronized model of bone remodeling.

The role of leukotrienes on bone resorption was tested in a well-standardized model of bone remodeling by inhibiting their biosynthesis with BWA4C, a specific inhibitor of 5-lipoxygenase. After extraction of their upper molars unilaterally, 30 Wistar rats were divided into three groups; the first remained untreated (control group), the second received 80 mg/kg/day of BWA4C dissolved in polyethylene glycol 300 (experimental group), and the third received only the vehicle (sham-treated group). After four days of experiment, the animals were killed and the resorption profile was assessed along the antagonist mandibular buccal cortex. The main result was a dramatic decrease in the number of TRAP-positive mononucleated preosteoclasts in the experimental group (-69%, p < 0.0005 and p < 0.003 vs. the control and sham-treated groups, respectively). This drop was related to a significant decrease in the number of osteoclasts. Neither the activation of the differentiated osteoclasts nor their mean interface with the bone surface were affected by BWA4C. Concomitantly, the mast cell population residing near the vascular network limiting the periosteum was markedly and significantly increased by the treatment. These mast cells were mostly degranulating, i.e., were in a state of activation that we previously found to related to resorption. These data suggest (1) that the leukotrienes are involved in the recruitment of osteoclast progenitors, and/or their differentiation into preosteoclasts, and (2) that mast cells responded to leukotriene inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1994

New approaches to tissue regeneration and repair.

Several Heparin Binding Growth Factors (HBGFs) are thought to play a key role in the natural processes of tissue regeneration or repair after being released by neighbouring, inflammatory or circulating cells as well as from extracellular matrix associated heparan sulfate proteoglycosaminoglycans. In order to better understand how the bioavailability of these HBGFs can take part in the regulation of the wound healing processes, we have studied the healing effect of various chemically substituted dextrans (CMDBS) selected for their affinity for HBGFs, alone and in association with HBGFs. The CMDBS was obtained by substitution of methylcarboxylic (CM), benzylamide (B) and benzylamine sulfonate (S) groups in proportion of 83%, 23% and 13% respectively for CMDBS K that we have further used (Mauzac et al., 1985 Biomaterials. 6: 61-63). CMDBS K could 1: potentiate the biological activity of 1 or 2 FGFs, 2: protect 1 and 2 FGFs against thermal or pH inactivation, 3: protect a and b FGFs against proteolytic degradation (Tardieu et al., 1992 J. Cell. Physiol. 150: 194-203). CMDBS K was tested alone in cutaneous and bone wound healing models and for its ability to stabilize FGFs. Rats were punched and skin regeneration was studied by morphometric and histological analysis. The wounds (6 mm diameter) were filled with collagen plaster alone or soaked with CMDBS. CMDBS K in collagen plaster was able to induce a remarkable effect both on the kinetics and on the quality of the restored skin. These results suggest that endogenous growth factors naturally released during the regeneration process could be trapped, protected and released by CMDBS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Improvement of gingival and alveolar bone status in periodontitis-affected hamsters treated with 15-methyl prostaglandin E1.

Exogenous PGE1 at pharmacological doses suppresses acute and chronic inflammation manifestations. As periodontitis possesses features of both acute and chronic inflammation, attenuation of periodontal destruction in hamsters was attempted by using 15-M-PGE1, a stable PGE1 analog. The agent was tested at 2 different doses (100 and 150 micrograms/kg/d) and its effects were matched against disease-free and periodontitis-affected animals. No effect was found with the 100 micrograms regimen. In contrast, in the 150 micrograms group, in the gingiva around the first right mandibular molar the pocket epithelium and infiltrated connective tissue (ICT) areas, the mean vascular lumen, the number of PMNLs adherent to blood vessels and infiltrating the ICT were significantly reduced. The number of osteoclasts was markedly diminished as well, but their intrinsic activity was enhanced. Bone formation was totally inhibited in this treatment group. These results indicated that 15-M-PGE1 effectively improved gingival inflammation mostly by reducing edema and PMNL recruitment and controlled alveolar bone destruction by reducing the osteoclast recruitment. From a therapeutic point of view the complete inhibition of formation seems to contraindicate its use.

Alprostadil↗

PubMed1994

[CMDBS, functional analogs of sulfate heparanes, used as osseous cicatrizing agents].

Several Heparin-Binding Growth Factors (HBGFs) are known to play an important role in bone repair. When osseous tissue is injured, an important increase of protease activities and a massive release of HBGFs occur. The local increase in HBGFs content at the wounded site, produced by a release of this factors from cells implicated in haemostasis and inflammatory reaction and from extracellular matrix associated heparan sulfate proteoglycans (HSPGs), seems to be a crucial step in bone healing. The proteolysis associated with the tissue injury probably limits the growth factors activities at the wound site. In order to define the bone healing potential of molecules that would be able to protect HBGFs against proteolytic activation, we studied the effect of derived dextrans, named carboxymethyl-benzylamide-sulfonated dextrans (CMDBS), behaving as heparan like molecules, in 5 mm in diameter skull trepaned defects in young adult rats. In this model CMDBS induced an important bone regeneration in a dose dependent manner while controls were not repaired. In CMDBS treated animals the defects were repaired and contained a tissue of normal appearance; in several treated animals the sagittal suture, initially removed by the trephination, was restored. This remarkable bone healing potential of CMDBS may result from the capacity to protect the endogenous HBGFs from proteolysis and to modulate their biological activities, in a similar manner to that observed for fibroblast growth factors and HSPGs. CMDBS represent a new form of bone healing agents, which have the advantage of being produced by a controlled chemical synthesis, and of avoiding the use of exogenous growth factors because of their capacity to enhance the bone healing potential of the endogenous growth factors.

Animals↗

PubMed1993

Inhibition of prostanoid synthesis depresses alveolar bone resorption but enhances root resorption in the rat.

Tooth drift requires the deformation of the root socket and the adjustment of the other components of the attachment apparatus, namely, the periodontal ligament (PDL) and the cementum. Indomethacin (7.5 mg/kg/d), an inhibitor of prostanoid synthesis, provoked in rats a depression in the bone resorption effecting the deformation of the socket (Lasfargues and Saffar, Anat. Rec., 234:310-316, 1992). In the present paper we examined the consequence of this treatment both on the PDL and the root surface. After 3 days of treatment, when osteoclastic resorption was not yet disturbed, the root had been markedly resorbed (P < 0.05) opposite the resorbing bone surface; at that time the PDL width remained in the normal range. After 7 days, i.e., when the bone resorption was depressed, the PDL was widened as the result of the ongoing root resorption. Despite the extensive root resorption, the anchorage of the PDL fibers appeared to remain effective, suggesting that it was rapidly restored. On day 14 at the time of the bone resorption recovery, cementum was deposited in the root resorption lacunae and the PDL width had returned to its control value. As early as day 3 the daily rate of dentine formation increased in the pulp area subjacent to the root resorption lacunae (P < 0.01). These data demonstrate that i) the responses of the different components of the periodontal apparatus are coordinated to allow for the maintainance of the PDL width so that when bone resorption is disturbed, root resorption compensates for it, and ii) the odontoclasts can differentiate and resorb under prostanoid inhibition whilst osteoclastic resorption of the bone socket is inhibited.

Adaptation, Physiological↗

PubMed1993

Dose-effect and evidence of escape of inhibition after indomethacin treatment in a synchronized model of bone resorption.

We previously showed that cyclooxygenase inhibition by indomethacin (7.5 mg/kg/d) prevented resorption in a model of synchronized remodeling. In the present paper, we (i) tested the effectiveness of three doses of indomethacin (2, 4, 7.5 mg/kg/d) in this model, and (ii) verified whether indomethacin action was sustained in time. For that purpose, on day 6 after induction, untreated controls were compared with a group treated for six days with indomethacin (7.5 mg/kg/d), and an interrupted treatment group (4 days indomethacin + 2 days free). Indomethacin inhibited resorption and total number of osteoclasts in a dose-dependent manner. In the second experiment in the discontinued group, the resorption and total number of osteoclasts were similar to sham-treated animals. Indomethacin was still effective in the continuous treatment group; however, resorption was distinctly higher than in the rats treated for four days. These data indicate that despite cyclooxygenase inhibition, another metabolic pathway started resorption. The stoppage of prostanoid inhibition permitted the rapid and complete restoration of resorption.

Animals↗

PubMed1993

[Regulation of osteoclastic resorption by prostanoids in vivo].

Prostanoids, and particularly prostaglandins (PGs) E, are potent mediators of bone resorption. However the actual role(s) of these agents in osteoclastic resorption is (are) not yet known. In an attempt to approach the role of prostanoids in the events leading to resorption itself, we used two different animal models. We showed that indomethacin, an inhibitor of prostanoid biosynthesis, drastically reduced osteoclastic resorption at the dose of 7 mg/kg/d in the two models. This effect was dose-dependent as resorption inhibition increased by increasing the dose of indomethacin. However the effect was already significant at the lower dose (2 mg/kg/d). The total number of osteoclasts in the site was according by reduced, showing the involvement of the prostanoids in the events preceding and/or regulating the fusion of the mononucleated preosteoclasts into multinucleated osteoclasts. The calculation of the ratio active/inactive osteoclasts indicated that the activation (i.e. access to the bone surface) of the osteoclast, was prostanoid-dependent; indeed the ratio systematically decreased in the indomethacin-treated animals in the two models. We also observed that the inhibition was not sustained in time as resorption recovered, probably through the starting of PG-independent metabolic pathways. However this starting was rather slow and these pathways apparently were less affective than the PG-dependent ones since the intrinsic activity of the differentiated osteoclasts was significantly reduced.

Animals↗

PubMed1992

Effects of prostaglandin inhibition on the bone activities associated with the spontaneous drift of molar teeth in the rat.

Little is known about local bone regulation that enables spontaneous molar tooth drift. In this study the role of prostaglandins (PGs) were investigated in the rat by inhibiting PG-synthesis with indomethacin (7 mg/kg/d). Untreated animals were killed at the start of the experiment, while treated ones were killed after 3, 7, or 14 days of treatment. Mandibles were processed for histomorphometry without demineralization. Changes in osteoclasts and extent of the different steps of the bone remodeling sequence (resorption, reversal, and formation) were assessed along the remodeling side of the socket of the buccal root of the first molar. The total number of osteoclasts decreased after 7 days of PG inhibition (P < 0.01 vs controls) and then partially recovered. This change was due to a sharp decrease in active cells on day 7 (P < 0.01), while inactive cells remained unchanged throughout the experimental period. The extent of resorption fell on day 7 (P < 0.01) and then recovered almost to the control level on day 14. Reversal at first increased insignificantly and thereafter decreased (P < 0.02) for the remaining 7 days. Formation was modified only on day 14; at that time it had doubled compared with controls. These results show that PGs are involved in the local regulation of bone remodeling accompanying tooth drift. Resorption inhibition was partial, indicating that other factors participate with PGs in this regulation; in addition, the trend to recovery observed at the end of the experimental period suggests that these factors can take over from PGs to achieve the necessary remodeling of the socket.

Alveolar Process↗

PubMed1992

Spontaneous recovery from growth disturbances and osteopenia induced by a high carbohydrate diet in hamsters.

Femoral osteopenic changes characterized by a fall in metaphyseal trabecular bone volume (TBV) have been previously reported in hamsters fed a high carbohydrate diet for 45 days. In the present study the effects of the diet were assessed after 90 days. Serum P was significantly reduced (p less than 0.05) in experimental animals; serum Ca was unaltered. Disturbances in body growth had occurred as shown by a reduction in body weight gain (p less than 0.05) in the first 45 days of the experiment and by a decrease in femoral size (p less than 0.02). Osteopenia had also developed: the epiphyseal TBV decreased (p less than 0.05) as well as the thickness of both epiphyseal and metaphyseal trabeculae (p less than 0.001). However signs of partial recovery from this condition were observed as shown by an increased body weight gain in the last 45 days of the experiment (p less than 0.02) and lack of difference in metaphyseal TBV, assumed to be the more labile, between the 2 groups. Moreover bone formation significantly increased along metaphyseal trabeculae and the endosteal aspect of the cortices.

Animals↗

PubMed1991

Partial inhibition of bone resorption by disodium cromoglycate in a synchronized model of bone remodeling.

In a previous study we observed that mast cell degranulation might be associated to bone resorption. To verify this assumption, the efficiency of cromoglycate was assessed on a synchronized sequence of bone remodeling induced in male Wistar rats along the mandibular cortex. After 4 days (time of osteoclastic peak in this model), cromoglycate (15/mg/kg and 30 mg/kg/d per os) decreased the number of degranulating mast cells, especially in the population adjacent to the bone surface. Concomitantly the extent of resorption surface was decreased vs untreated animals. Active osteoclasts were lower whereas the total number of osteoclasts (both active and inactive) was not statistically modified. The mean osteoclast-bone interface was not modified. No dose effect was found. These data indicate that mast cell degranulation is involved in the events leading to osteoclast resorption, presumably in the mechanisms providing osteoclast access to bone surface.

Animals↗

PubMed1991

Identification of osteoclasts and their mononuclear precursors. A comparative histological and histochemical study in hamster periodontitis.

Quantification of osteoclast resorption, a good index of periodontitis destruction, is primarily based on osteoclast identification. As their identification is sometimes dubious, we compared osteoclastic counts in hamster specimens processed for either routine histology or tartrate-resistant acid phosphatase (TRAP) staining. No difference was found between the two approaches concerning the number of osteoclasts. However the mean bone-osteoclast interface was higher in the TRAP-stained specimens (+30%, p less than 0.02). As osteoclast precursors are also TRAP+ cells, they were quantified too. Compared with controls, there was a dramatic increase (p less than 0.0001) in periodontitis-affected animals. Precursors were strongly correlated to active osteoclasts (r = 0.97). Our data suggest that precursors are recruited only when the disease is active in a given site.

Acid Phosphatase↗

PubMed1990

Changes in mast cell number during the activation phase of an induced synchronized remodeling sequence in the rat.

Increase in mast cell (MC) number has been reported in some pathological conditions with increased remodeling. However, it is not known whether MCs are involved in the physiological remodeling of bone. In the present study the possible variations in MCs were investigated during the activation phase in a rat model of synchronized remodeling. Seven groups of 10 rats were used. As early as the first day of induction, MCs increased by 50% and then decreased on day 2. The same pattern of changes recurred on days 3 and 4. Intact non-degranulating MCs increased mainly at some distance from the bone surface. Degranulating MCs conversely decreased near the cambium layer of the periosteum. Prostaglandins were not involved in these changes. These results suggest an association between the events leading to the onset of bone resorption and MCs. Degranulation might induce the release of agents active on these events.

Animals↗

PubMed1990

Bone reactions around transplanted roots. A 5-month quantitative study in dogs.

The aim of this experiment was to study endosteal bone reactions around roots transplanted into an edentulous crest, and the role, if any, of periodontal ligament (PDL) remnants preservation. After extraction of premolars and healing of the crests, 20 roots in 5 dogs were transplanted into bone cavities prepared in the edentulous areas. Roots implanted in the lower and upper right cavities had their PDL remnants preserved while those grafted in the left cavities had their surface planed and dried. After 5 months, the roots with surrounding bone were removed. 2 bone areas were delineated at the mesial aspect of each root, one immediately adjacent to the alveolar wall and the other distal to it. Results demonstrated that bone volume was higher in the proximal versus distal area in the maxilla and mandible preserved groups. The adipocyte content of the marrow spaces, an index of bone maturation, was less pronounced in the proximal versus distal areas in the preserved groups. The number of osteoclasts was higher in the proximal zone in the preserved groups as were the extents of the different bone remodeling activities. The results indicate that the organization of PDL around transplanted roots is associated with rearrangement of the bone tissue surrounding the grafts. This process of long duration might be an adaptation to the likely low mechanical strains applied on bone through the root. Transplantation of PDL-damaged roots did not induce such events in the surrounding bone which had acquired the structure of an edentulous crest.

Adipose Tissue↗

PubMed1990

Bone formation in tricalcium phosphate-filled periodontal intrabony lesions. Histological observations in humans.

The capacity of a tricalcium phosphate (TCP) ceramic to promote bone formation after grafting in intrabony defects was studied in humans. Five biopsies were collected from 4 patients during reentry surgery 16 to 40 months after implantation. They were processed without demineralization for histological examination. In the less mature samples, the grafted material was surrounded by a highly fibrous, highly cellular, and poorly vascularized connective tissue. Howship's lacuna-like cavities were clearly visible at the surface of the material. They contained resorbing mononuclear phagocytes. At a more mature stage, TCP granules were embedded in an acellular fibrous material which underwent mineralization from the medullary spaces towards the granules. The bone formed was subsequently remodeled. The implanted material itself was progressively modified. It first acquired the staining appearance of bone. After its structure became loose and vacuolated, it was invaded by cells and vessels. The present data indicate that TCP has osteogenic potential and is subject to degradation. Unlike in experimental wounds, these processes are of long duration in human defects.

Adult↗