Histological and histomorphometric aspects of continual intermittent parathyroid hormone administration on osseointegration in osteoporosis rabbit model.

In implant treatment, primary stability and osseointegration are improved by continual intermittent administration of parathyroid hormone (PTH) in patients with osteoporosis. However, the histological and histomorphometric aspects are not clear. The aim of this study was to investigate the histological and histomorphometric effects of intermittent PTH administration on osseointegration in a glucocorticoid-induced osteoporotic rabbit model. Fifteen female New Zealand rabbits were prepared for the osteoporosis model with ovariectomy and glucocorticoid administration. After 1 week, five rabbits were intermittently administered PTH for 8 weeks until the end point (PTHa group) and five for 4 weeks until implant placement (PTHb group). The remaining rabbits were intermittently administered saline for 8 weeks until the end point (Control group). Dental implants were inserted into the femoral epiphyses 11 weeks after ovariectomy. After 4 weeks, the maximum removal torque (RT) of the placed implant and bone implant contact (BIC) ratio were evaluated. In addition micro-computed tomography and histomorphometric analyses were performed. The RT and BIC values were significantly higher in the PTHa group compared with those of the PTHb and Control groups (p< 0.05). Furthermore, the bone mineral densities and Hounsfield units were significantly higher in the PTHa group than those in the PTHb and Control groups. Histologic and histomorphometric measurements revealed that continuous administration of PTH improved bone density and bone formation around the implant placement site, as well as systemic bone formation. Therefore, favorable implant stability was achieved under osteoporosis.

Osseointegration Aspects of Implants at the Bone Reconstruction Site by a Novel Porous Titanium Scaffold.

OBJECTIVES: Porous titanium is used for the reconstruction of large bone defects due to its excellent mechanical strength. The quality of osseointegration of implants placed in bone reconstructed with porous titanium is unknown. The purpose of this in vivo study was to evaluate the osseointegration of implants at sites reconstructed using porous titanium. MATERIAL AND METHODS: Hollow porous titanium (Ti) (outer-diameter 6 mm, inner-diameter 2 mm, length 4 mm, 85% porosity) and similar-sized porous hydroxyapatite (porous HA: 75% porosity) samples were prepared and implanted in 6 New Zealand white rabbit femurs. Four weeks later, an implant bed was created to receive a Ti implant (diameter 2 mm, length 4 mm). An implant placed at a pristine bone site served as the control. Four weeks later, histological and histomorphometric evaluations of the test and control sites were conducted. RESULTS: Osseointegration was observed in all groups. There was no significant difference in the bone formation ratio and bone-implant contact (BIC) ratio across all groups for the whole area. At the cancellous bone area of the bone defect, superior bone formation ratio and BIC ratio were observed with porous Ti and porous HA compared to the control (bone formation ratio: control 1.8 [SD 3]%, HA 23 [SD 3]%, Ti 23.6 [SD 5]%; BIC ratio: control 5.4 [SD 5.3]%, HA 28.9 [SD 10.7]%, Ti 41.6 [SD 14]%). Porous Ti demonstrated good osteoconduction and osseointegration abilities, similar to porous HA. CONCLUSIONS: To our knowledge, this is the first report of implant treatment after preliminary bone reconstruction using a titanium biomaterial. Porous titanium is a suitable material for bone reconstruction before implant treatment in load-bearing areas that allow subsequent prosthetic treatment.

Generalized periodontitis treated with periodontal, orthodontic, and prosthodontic therapy: A case report.

BACKGROUND: Generalized periodontitis is a severe periodontal disease characterized by rapid periodontal destruction in healthy persons. This case report describes the treatment of a severe crowding, large overjet, and occlusal collapse due to the loss of anterior guidance with generalized periodontitis. CASE SUMMARY: A 35-year-old female patient with a chief complaint of crowding and maxillary protrusion was diagnosed with generalized periodontitis by clinical and radiographic examinations. To improve crowding and overjet, orthodontic treatment was performed after basic periodontal therapy. Severely damaged upper right lateral incisor and left canine were extracted, and lower right first premolar and left second premolar were also removed to treat severe crowding. After orthodontic treatment, periodontal flap surgery for upper left molars and guided tissue regeneration for the lower left second molar was performed. Then, a dental implant was inserted in the upper left canine legion. The esthetics of the maxillary anterior tooth was improved by prosthetic restorations. The treatment result showed a well-improved occlusion with proper anterior guidance and healthy periodontal tissue after a retention period of 10 years. CONCLUSION: Periodontal, orthodontic, and prosthodontic treatments are extremely useful to improve function and stable periodontal tissue for generalized periodontitis.

Comparative Study of Surface Modification Treatment for Porous Titanium.

OBJECTIVES: This study was to investigate suitable surface treatment methods for porous titanium by ex vivo study of material properties and calcium phosphate deposition in simulated body fluid. MATERIAL AND METHODS: Porous titanium with acid (H2SO4 and HCl mixed acid) or alkali (NaOH) treatment was prepared. The surfaces were observed, and the weight change ratio (after and before surface treatment) and compression strength were measured. To investigate the apatite formation ability, each sample was immersed in simulated body fluid (SBF). Surface observations were performed, and the weight change ratio (before/after immersing SBF) and calcification (by alizarin red staining) were measured. RESULTS: The acid group showed a martensitic micro-scale rough structure and the weight and mechanical strength greatly decreased compared to the other groups. The alkali group exhibited a nano-scale roughness structure with similar weight and mechanical strength. Following immersion in SBF, an apatite-like crystal layer in the alkali group was observed. The weight of all samples increased. The change in weight of the samples in the alkali, acid, and control groups were significantly different, showing the following trend: alkali group (1.6%) > acid group (1.2%) > control group (0.8%). Calcium precipitation values were higher in the samples from alkali group than in those from the acid and control groups. CONCLUSIONS: Alkali treatment was found to be a suitable surface modification method for porous titanium, resulting in good mechanical strength and apatite formation ability in simulated body fluid.

Development of a novel bioactive titanium membrane with alkali treatment for bone regeneration.

This study evaluates a bioactive titanium membrane with alkali treatment for stimulating apatite formation and promoting bone regeneration. The titanium thin membranes were either treated with NaOH (alkali-group) or untreated (control). Each sample were incubated in simulated body fluid. Subsequently, the composition of the surface calcium deposition, its weight increase ratio, and optical absorbance were evaluated. Then, the bone defect was trephined on the rats calvaria and covered with each sample membrane or no membrane, and the bone tissue area ratio (BTA) and bone membrane contact ratio (BMC) were evaluated. The spherical crystalline precipitates formed in both groups. In the alkali-group after 21 days, the precipitates matured, forming apatite-like precipitates. The alkali-group showed higher Ca and P contents and weight increase ratios than the control. The alkali-group exhibited a higher BMC than the control in the central area. Thus, this novel membrane has high apatite-forming and bone regeneration abilities.

The development of novel bioactive porous titanium as a bone reconstruction material.

Porous titanium fabricated by the resin-impregnated titanium substitute technique has good mechanical strength and osteoconduction. The alkali treatment of the titanium surface creates a bioactive surface. Alkali-treated porous titanium is expected to accelerate bone formation. The purpose of this study was to evaluate the bone reconstruction ability of alkali-treated porous titanium. Porous titanium (85% porosity) was treated with an alkali solution (5 N NaOH, 24 h). To assess material properties, we analyzed the surface structure by scanning electron microscopy (SEM) and mechanical strength testing. To assess bioactivity, each sample was soaked in a simulated body fluid (Hank's solution) for 7 days. Surface observations, weight change ratio measurement (after/before being soaked in Hank's solution) and surface elemental analysis were performed. We also designed an in vivo study with rabbit femurs. After 2 and 3 weeks of implantation, histological observations and histomorphometric bone formation ratio analysis were performed. All data were statistically analyzed using a Student's t-test (P < 0.05) (this study was approved by the Hiroshima University animal experiment ethics committee: A11-5-5). Non-treated porous titanium (control) appeared to have a smooth surface and the alkali-treated porous titanium (ATPT) had a nano-sized needle-like rough surface. ATPT had similar mechanical strength to that of the control. After soaking into the Hank's solution, we observed apatite-like crystals in the SEM image, weight gain, and high Ca and P contents in ATPT. There was significant bone formation at an early stage in ATPT compared with that in control. It was suggested that the alkali-treated porous titanium had a bioactive surface and induced bone reconstruction effectively. This novel bioactive porous titanium can be expected to be a good bone reconstruction material.

Novel fabrication of porous titanium by a resin-impregnated titanium substitution technique for bone reconstruction.

The purpose of this study was to develop a novel porous titanium material with superior mechanical strength and osteoconduction for bone reconstruction. Porous titanium samples were fabricated by titanium-slurry impregnate to prepare urethane forms with several porosities (high-porosity; 92%, middle-porosity; 85% and low-porosity; 65%). Porous HA (mean porosity; 75.3%) was used as a control. To evaluate the characteristics of these materials, we performed porosity measurements, scanning electron microscopy (SEM), three-point bending testing, and cell proliferation assays. To evaluate the osteoconduction ability, porous titanium was placed into the femurs of rabbits and histological and histomorphometric evaluations were performed after 3 weeks. In SEM images, porous three-dimensional structures were observed in all samples. The bending strength significantly increased as porosity increased (Ti-65 > Ti-85 > porous HA > Ti-92, P < 0.05; respectively). Ti-65, Ti-85, and porous HA showed good cell proliferation. Newly formed bone was observed in the central portion of Ti-65, Ti-85, and porous HA. Ti-92 was mainly detected in the bone marrow tissue. The bone formation areas of Ti-65, Ti-85, and porous HA were significantly higher than that of Ti-92 (P < 0.05). It was suggested that novel developed porous titanium composed of Ti-65 and Ti-85 showed superior mechanical strength and osteoconduction.

Enhancement of calcification by osteoblasts cultured on hydroxyapatite surfaces with adsorbed inorganic polyphosphate.

Inorganic polyphosphate has been expected to accelerate bone regeneration. However, there are limited evidences to prove that polyphosphate adsorbed on the surface of a hydroxyapatite plate enhances calcification of cultured osteoblasts. In this study, we examined the effect of polyphosphate adsorbed onto the surface of a hydroxyapatite plate on the attachment, proliferation, differentiation, and calcification of osteoblasts. After hydroxyapatite plates were soaked in solutions of polyphosphate, the plate surfaces were analyzed by scanning electron microscopy and toluidine blue staining to confirm adsorption of polyphosphate. The hydroxyapatite plates were further subjected to the measurements of surface roughness, water contact angle, and the binding capacity of calcium ions. Cell culture experiments were carried out using MC3T3-E1 pre-osteoblastic cells. It was found that soaking a hydroxyapatite plate in a polyphosphate solution gave rise to an increase in surface roughness and reduction in water contact angle in a concentration-dependent manner, suggesting the adsorption of polyphosphate onto the surface of a hydroxyapatite plate. It was further observed that surface-adsorbed polyphosphate exhibited an inhibitory effect on cell adhesion and proliferation. In contrast, cell differentiation was promoted on hydroxyapatite plates with adsorbed polyphosphate, when assessed from expression of differentiation marker genes including alkaline phosphatase, osteopontin, and osteocalcin. In addition, calcification of the culture was enhanced on hydroxyapatite plates with relatively low density of adsorbed polyphosphate. Our results as a whole provided an evidence to show that there is a narrow window with regard to the surface density of adsorbed polyphosphate for the enhancement of osteoblast calcification.

Effects of continual intermittent administration of parathyroid hormone on implant stability in the presence of osteoporosis: an in vivo study using resonance frequency analysis in a rabbit model.

OBJECTIVE: This study aimed to evaluate the effects of continual intermittent administration of parathyroid hormone (PTH) on implant stability in the presence of osteoporosis, using rabbit models. MATERIAL AND METHODS: Fifteen female New Zealand white rabbits underwent ovariectomy and were administered glucocorticoids to induce osteoporosis, following which they were divided into three groups. The first group received intermittent subcutaneous PTH for 4 weeks until implant placement (PTH1), while the second and third groups received PTH (PTH2) and saline (control), respectively, for 4 weeks before and after implant placement. After intermittent administration of PTH or saline, titanium implants were inserted into the left femoral epiphyses of all animals, and the implant stability quotient (ISQ) was measured immediately after placement to assess the primary stability and at 2 and 4 weeks after implant placement to assess osseointegration. At 4 weeks after implant placement, histological and histomorphometric evaluations were conducted and the bone area around the implant socket was measured as a ratio of the total bone area to the total tissue area. RESULTS: Regarding primary stability, the ISQ values for the PTH1 and PTH2 groups were significantly higher than those for the control group (p<0.05). Concerning osseointegration, the ISQ values at 2 and 4 weeks were significantly higher for the PTH2 group than for the PTH1 and control (p<0.05) groups. Histological assessments showed a thicker and more trabecular bone around the implant sockets in the PTH2 specimens than in the PTH1 and control specimens. The bone area around the implant socket was significantly greater in the PTH2 group than in the PTH1 and control groups (p<0.05). CONCLUSIONS: Our results suggest that continual intermittent PTH administration before and after dental implant placement is effective for the achievement of favorable stability and osseointegration in the presence of osteoporosis.

Effects of continual intermittent administration of parathyroid hormone on implant stability in the presence of osteoporosis: an in vivo study using resonance frequency analysis in a rabbit model

Abstract Objective: This study aimed to evaluate the effects of continual intermittent administration of parathyroid hormone (PTH) on implant stability in the presence of osteoporosis, using rabbit models. Material and Methods: Fifteen female New Zealand white rabbits underwent ovariectomy and were administered glucocorticoids to induce osteoporosis, following which they were divided into three groups. The first group received intermittent subcutaneous PTH for 4 weeks until implant placement (PTH1), while the second and third groups received PTH (PTH2) and saline (control), respectively, for 4 weeks before and after implant placement. After intermittent administration of PTH or saline, titanium implants were inserted into the left femoral epiphyses of all animals, and the implant stability quotient (ISQ) was measured immediately after placement to assess the primary stability and at 2 and 4 weeks after implant placement to assess osseointegration. At 4 weeks after implant placement, histological and histomorphometric evaluations were conducted and the bone area around the implant socket was measured as a ratio of the total bone area to the total tissue area. Results: Regarding primary stability, the ISQ values for the PTH1 and PTH2 groups were significantly higher than those for the control group (p<0.05). Concerning osseointegration, the ISQ values at 2 and 4 weeks were significantly higher for the PTH2 group than for the PTH1 and control (p<0.05) groups. Histological assessments showed a thicker and more trabecular bone around the implant sockets in the PTH2 specimens than in the PTH1 and control specimens. The bone area around the implant socket was significantly greater in the PTH2 group than in the PTH1 and control groups (p<0.05). Conclusions: Our results suggest that continual intermittent PTH administration before and after dental implant placement is effective for the achievement of favorable stability and osseointegration in the presence of osteoporosis.

A stability evaluation of a novel titanium dental implant/interconnected porous hydroxyapatite complex under functional loading conditions.

The aim of this study was to evaluate the stability of implant/interconnected porous calcium hydroxyapatite complex (implant/IPCHA-complex) under functional loading. Implant/IP-CHA-complexes were placed into the mandibles of four Beagle-Labrador hybrid dogs (complex-group). On the other side, an implant was placed directly (control-group). To subject the loading, the animals were fed a hard diet throughout the loading phase of 5 months. The implant stability quotients (ISQs) and bone implant contact (BIC), and histological evaluations were performed. The ISQs of implant/IP-CHA-complex was significantly lower at placement than that of the control-implant. On the other hand, there was no significant difference between in the groups during loading. The BIC measurements, there was no significantly difference between in both groups. Histologically, newly formed bone was observed in contact with most of the implant surface in the complex-group. An IP-CHA/implant-complex would be able to achieve both bone reconstruction and implant stability under functional loading conditions.

Osseointegration aspects of placed implant in bone reconstruction with newly developed block-type interconnected porous calcium hydroxyapatite.

OBJECTIVES: The purpose of this study was to evaluate the osseointegration of dental implant in bone reconstructions with interconnected porous calcium hydroxyapatite (IP-CHA). MATERIAL AND METHODS: The IP-CHA cylinders (D; 4.3 mm, H; 10.0 mm) were placed into bone sockets in each side of the femurs of four male dogs. The IP-CHA on the right side was a 24-week sample. Twelve weeks after placement, a titanium implant was placed into a socket that was prepared in half of the placed IP-CHA cylinder on the right side. On the left side, another IP-CHA cylinder was placed as a 12-week sample. After another 12 weeks, the samples were harvested, and the bone regeneration and bone-implant contact (BIC) ratios were measured. RESULTS: New bone formation area was superior in the 24-week IP-CHA compared with the 12-week IP-CHA. BIC was not significantly different between IP-CHA and the parent sites. Osseointegration was detected around the implant in IP-CHA-reconstructed bone. CONCLUSION: Our preliminary results suggest that IP-CHA may be a suitable bone graft material for reconstructing bones that require implant placement.

Osseointegration aspects of placed implant in bone reconstruction with newly developed block-type interconnected porous calcium hydroxyapatite

ABSTRACT Artificial bone has been employed to reconstruct bone defects. However, only few reports on implant placement after block bone grafting exist. Objectives The purpose of this study was to evaluate the osseointegration of dental implant in bone reconstructions with interconnected porous calcium hydroxyapatite (IP-CHA). Material and Methods The IP-CHA cylinders (D; 4.3 mm, H; 10.0 mm) were placed into bone sockets in each side of the femurs of four male dogs. The IP-CHA on the right side was a 24-week sample. Twelve weeks after placement, a titanium implant was placed into a socket that was prepared in half of the placed IP-CHA cylinder on the right side. On the left side, another IP-CHA cylinder was placed as a 12-week sample. After another 12 weeks, the samples were harvested, and the bone regeneration and bone-implant contact (BIC) ratios were measured. Results New bone formation area was superior in the 24-week IP-CHA compared with the 12-week IP-CHA. BIC was not significantly different between IP-CHA and the parent sites. Osseointegration was detected around the implant in IP-CHA-reconstructed bone. Conclusion Our preliminary results suggest that IP-CHA may be a suitable bone graft material for reconstructing bones that require implant placement.

A novel mouthpiece prevents bite injuries caused by intraoperative transcranial electric motor-evoked potential monitoring.

PURPOSE: Intraoperative transcranial motor-evoked potential monitoring causes contraction of the masseter muscles, which may cause injuries to the oral cavity and damage to the orotracheal tube. We developed a mouthpiece made from vinyl-silicone impression material to prevent these injuries. The purpose of this study was to examine its efficacy and safety. METHODS: Twenty-two patients undergoing spinal surgery under transcranial motor-evoked potential monitoring were fitted with bespoke vinyl-silicone mouthpieces by dentists before surgery. On induction of general anesthesia and orotracheal intubation, the mouthpiece was attached to the upper and lower dental arches. A lateral cervical X-ray was taken at the end of surgery to examine the condition of the orotracheal tube. The incidence of endotracheal tube deformation was compared with an historic control group of 20 patients in whom a conventional gauze bite block had been previously used before induction of the mouthpiece. The oral cavity was examined by a dentist the day before surgery and 3 days postoperatively, and intraoral injuries were recorded. RESULTS: No endotracheal tube deformation was found in 22 patients fitted with the new mouthpiece. The incidence of tube deformation (none of 22 patients, 0 %) was significantly lower than in those who had been fitted with the gauze bite block (9 of 20 patients, 45.0 %; p < 0.001). Application of the mouthpiece resulted in no tongue or tooth injuries. CONCLUSION: A novel mouthpiece reduced the incidence of damage to the endotracheal tube caused by intraoperative transcranial motor-evoked potential monitoring.

Intermittent administration of parathyroid hormone enhances primary stability of dental implants in a bone-reduced rabbit model.

The aim of the study was to investigate the effect of parathyroid hormone (PTH) on primary stability of dental implants in a bone-reduced model. Ten female New Zealand white rabbits underwent ovariectomy and were administered glucocorticoid to induce osteoporosis. One group was administered PTH intermittently by subcutaneous injection for 4 weeks (PTH-group) and the other group was given injections of saline for 4 weeks (Osteoporosis; OP-group). After the administration period, implants were inserted into the distal femoral epiphyses of each animal. At implant placement, insertion torque (IT) and implant stability quotient (ISQ) were measured. Histological examination revealed newly formed trabecular bone around the implant socket in the PTH-group but not in the OP-group. The trabecular bone structures in the PTH-group appeared thicker than those in the OP-group. In the PTH-group, the mean IT value was significantly greater than that in the OP-group (29.8 ± 6.2 Ncm and 10.0 ± 2.1 Ncm, respectively; P < 0.05). The ISQ value in the PTH-group was significantly higher than that in the OP-group (74.7 ± 11.2 and 55.9 ± 13.5, respectively; P < 0.05). Intermittent PTH administration could be an effective treatment for achieving favorable primary stability of dental implants in patients with osteoporosis. (J Oral Sci 58, 241-246, 2016).

Influence of implant surface topography on primary stability in a standardized osteoporosis rabbit model study.

Evaluating primary stability is important to predict the prognosis of dental implant treatment. Primary stability is decreased in a low bone density site such as osteoporosis. However, it is difficult to apply in small animal and the effect of the different implant surface topography for the primary stability at low bone density site has not yet fully been investigated. The purpose of the present study was to evaluate the influence of implant surface topography on primary stability in a standardized osteoporosis animal model. Six rabbits underwent ovariectomy and administrated glucocorticoid to induce an osteoporosis model. Sham-operations were performed in additional six rabbits. Implants with machined or oxidized-surfaces were inserted into the femur epiphyses and insertion torque (IT) and implant stability quotient (ISQ) were measured. In sham model, the IT and ISQ did not differ significantly between the both implant. However, the IT value of oxidized-surface implant was significantly higher than that of the machined implant in the osteoporosis model. Meanwhile, ISQ did not significantly differ between the machined and oxidized-surfaced implants. In conclusion, the IT of implants is higher with rough than with smooth surfaces but that there are no differences in ISQ value between different surfaces in a standardized osteoporosis bone reduced rabbit model.

Inorganic polyphosphate adsorbed onto hydroxyapatite for guided bone regeneration: an animal study.

Inorganic polyphosphate (poly(P)) is recognized as a therapeutic agent that promotes fibroblast growth factor and enhances osteogenic differentiation, and in vivo, when adsorbed onto interconnected porous calcium hydroxyapatite (IP-CHA) enhances bone regeneration. The present study focused on the effect of poly(P) adsorbed onto IP-CHA granules (Poly(P)/IP-CHA) in guided bone regeneration (GBR). Dental implants were placed into the edentulous mandibular areas of five Beagle-Labrador hybrid dogs with screw expose on the buccal side, and then bone defects were filled Poly(P)/IP-CHA (test) or IP-CHA (control). After 12 weeks, histological evaluation and histomorphometrical analysis were performed. Newly-bone formation around exposed implant screw was clearly detected in the test-group. The ratio for regenerated bone height in the test group versus the control-group was 85.6±20.2 and 62.6±23.8, respectively, with no significant difference, while, that for bone implant contact was significantly higher (67.9±11.8 and 48.8±14.1, respectively). These findings indicate that Poly(P)/IP-CHA enhances bone regeneration in GBR.

Polyphosphate-mediated inhibition of tartrate-resistant acid phosphatase and suppression of bone resorption of osteoclasts.

Inorganic polyphosphate (poly(P)) has recently been found to play an important role in bone formation. In this study, we found that tartrate-resistant acid phosphatase (TRAP), which is abundantly expressed in osteoclasts, has polyphosphatase activity that degrades poly(P) and yields Pi as well as shorter poly(P) chains. Since the TRAP protein that coprecipitated with anti-TRAP monoclonal antibodies exhibited both polyphosphatase and the original phosphatase activity, poly(P) degradation activity is dependent on TRAP and not on other contaminating enzymes. The ferrous chelator α, α'-bipyridyl, which inhibits the TRAP-mediated production of reactive oxygen species (ROS), had no effect on such poly(P) degradation, suggesting that the degradation is not dependent on ROS. In addition, shorter chain length poly(P) molecules were better substrates than longer chains for TRAP, and poly(P) inhibited the phosphatase activity of TRAP depending on its chain length. The IC50 of poly(P) against the original phosphatase activity of TRAP was 9.8 µM with an average chain length more than 300 phosphate residues, whereas the IC50 of poly(P) with a shorter average chain length of 15 phosphate residues was 8.3 mM. Finally, the pit formation activity of cultured rat osteoclasts differentiated by RANKL and M-CSF were markedly inhibited by poly(P), while no obvious decrease in cell number or differentiation efficiency was observed for poly(P). In particular, the inhibition of pit formation by long chain poly(P) with 300 phosphate residues was stronger than that of shorter chain poly(P). Thus, poly(P) may play an important regulatory role in osteoclastic bone resorption by inhibiting TRAP activity, which is dependent on its chain length.

Inorganic polyphosphate suppresses lipopolysaccharide-induced inducible nitric oxide synthase (iNOS) expression in macrophages.

In response to infection, macrophages produce a series of inflammatory mediators, including nitric oxide (NO), to eliminate pathogens. The production of these molecules is tightly regulated via various mechanisms, as excessive responses are often detrimental to host tissues. Here, we report that inorganic polyphosphate [poly(P)], a linear polymer of orthophosphate ubiquitously found in mammalian cells, suppresses inducible nitric oxide synthase (iNOS) expression induced by lipopolysaccharide (LPS), a cell wall component of Gram-negative bacteria, in mouse peritoneal macrophages. Poly(P) with longer chains is more potent than those with shorter chains in suppressing LPS-induced iNOS expression. In addition, poly(P) decreased LPS-induced NO release. Moreover, poly(P) suppressed iNOS mRNA expression induced by LPS stimulation, thereby indicating that poly(P) reduces LPS-induced iNOS expression by down-regulation at the mRNA level. In contrast, poly(P) did not affect the LPS-induced release of TNF, another inflammatory mediator. Poly(P) may serve as a regulatory factor of innate immunity by modulating iNOS expression in macrophages.

New development of carbonate apatite-chitosan scaffold based on lyophilization technique for bone tissue engineering.

Carbonate apatite-chitosan scaffolds (CA-ChSs) were fabricated using the lyophilization technique. It was found that ChSs prepared with 200 mg chitosan powder (ChSs200) had well-structured three-dimensional architecture with high porosity and good retentive form without brittleness. In addition, it was shown that the number of osteoblast-like cells MC3T3-E1 proliferated on desalinated ChSs200 was larger than that on the non-desalinated ChSs200. CA-ChSs were fabricated by adding 100 mg carbonate apatite (CA) to 200 mg chitosan gels followed by freeze-drying (CA100ChSs200). SEM observation revealed that CA100ChSs200 had favorable three- dimensional porous structures. The number of living cells increased more rapidly on CA100ChSs200 prepared with different amounts of CA than on ChSs. ALP activity significantly increased after day 14 and reached a plateau after day 21 in ChSs200 and CA100ChSs200. It was concluded that newly developed CA100ChSs200 may be a possible scaffold material for tissue engineering.