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Although bone dehiscence may occur during orthodontic tooth movement into the narrow alveolar ridge, a non-invasive prevention method is yet to be fully established. We show for the first time prevention of bone dehiscence associated with orthodontic tooth movement by prophylactic injection of bone anabolic agents in mice. In this study, we established a bone dehiscence mouse model by applying force application and used the granular type of scaffold materials encapsulated with bone morphogenetic protein (BMP)-2 and OP3-4, the receptor activator of NF-κB ligand (RANKL)-binding peptide, for the prophylactic injection to the alveolar bone. In vivo micro-computed tomography revealed bone dehiscence with decreased buccal alveolar bone thickness and height after force application, whereas no bone dehiscence was observed with the prophylactic injection after force application, and alveolar bone thickness and height were kept at similar levels as those in the control group. Bone histomorphometry analyses revealed that both bone formation and resorption parameters were significantly higher in the injection with force application group than in the force application without the prophylactic injection group. These findings suggest that the prophylactic local delivery of bone anabolic reagents can prevent bone dehiscence with increased bone remodelling activity.

The receptor activator of NF-κB ligand (RANKL)-binding peptide, OP3-4, is known to stimulate bone morphogenetic protein (BMP)-2-induced bone formation, but peptides tend to aggregate and lose their bioactivity. Cholesterol-bearing pullulan (CHP) nanogel scaffold has been shown to prevent aggregation of peptides and to allow their sustained release and activity; however, the appropriate design of CHP nanogels to conduct local bone formation needs to be developed. In the present study, we investigated the osteoconductive capacity of a newly synthesized CHP nanogel, CHPA using OP3-4 and BMP-2. We also clarified the difference between perforated and nonperforated CHPA impregnated with the two signaling molecules. Thirty-six, five-week-old male BALB/c mice were used for the calvarial defect model. The mice were euthanized at 6 weeks postoperatively. A higher cortical bone mineral content and bone formation rate were observed in the perforated scaffold in comparison to the nonperforated scaffold, especially in the OP3-4/BMP-2 combination group. The degradation rate of scaffold material in the perforated OP3-4/BMP-2 combination group was lower than that in the nonperforated group. These data suggest that perforated CHPA nanogel could lead to local bone formation induced by OP3-4 and BMP–2 and clarified the appropriate degradation rate for inducing local bone formation when CHPA nanogels are designed to be perforated.

Tetracycline is used as a fluorescent reagent to measure bone formation activity in bone histomorphometric analyses. However, there is a possibility to lead a different conclusion when it is used in a bacteria-infected murine model since the tetracycline is considered to work as an antibiotic reagent. There are non-antibiotic fluorescent reagents such as alizarin and calcein for measuring bone formation activity. The purpose of this study was to clarify whether tetracycline could be an appropriate reagent to measure bone formation activity in a murine bacterial model in the same way as a non-antibiotic fluorescent reagent. We used Streptococcus mutans ( S. mutans ), a normal inhabitant in the oral cavity and tetracycline-sensitive bacteria, for inducing the bacterial model. The murine bacterial model was generated by intravenously inoculating S. mutans to the tail vein, followed immediately by the injection of the first fluorescent reagent, and the second one was injected 2 days prior to euthanization. After one day of inoculation with S. mutans , the subcutaneously injected alizarin had a similar colony count derived from the liver and the bone marrow tissue compared to the phosphate buffered saline (PBS)-injected control group. On the other hand, subcutaneous injection of tetracycline led to a significantly lower colony count from the liver compared to alizarin- or calcein-injected group. However, on day seven, after S. mutans intravenous injections, bone mineral density of distal femurs was significantly reduced by the bacteria inoculation regardless of which fluorescent reagents were injected subcutaneously. Finally, S. mutans inoculation reduced bone-formation-activity indices in both the tetracycline-alizarin double-injected mice and the calcein-alizarin double-injected mice. These results suggested that a one-time injection of tetracycline did not affect bone formation indices in the S. mutans -induced bone loss model. Tetracycline could be used for measuring bone formation activity in the same way as non-antibiotic fluorescent reagent such as calcein and alizarin, even in a tetracycline-sensitive bacterium-infected model.

Receptor activator of NF-κB ligand (RANKL)-binding peptides inhibit bone resorption and were recently shown to activate bone formation. The stimulatory mechanism underlying bone formation associated with these peptides was explained as RANKL-reverse signaling, wherein RANKL molecules on osteoblasts work as receptors to stimulate osteoblast differentiation. However, why RANKL-binding peptides stimulate osteoblast differentiation while osteoprotegerin (OPG), which is well known to bind to RANKL, cannot activate osteoblast differentiation has remained unclear. In this mini-review, we introduce three main issues: (1) The inhibitory effects of two RANKL-binding peptides (W9 and OP3-4) on bone resorption; (2) The stimulatory effects of the RANKL-binding peptides on osteoblast differentiation; and (3) The accumulation and membrane clustering of RANKL molecules at the cell surface of osteoblasts as a potential molecular switch stimulating osteoblast differentiation by RANKL-binding peptides.

Bone and muscle are closely linked through functional interdependence. Training and regular exercise can improve and maintain optimal bone mass and strength. Here, we investigated the effects of exercise combined with soft versus hard diet (pellet) on long bones in mice. Four groups of male C57BL/6J mice (n = 5 per group) were studied: hard diet (pellet) with exercise, soft diet (powdered) with exercise, hard diet (pellet) without exercise, and soft diet (powdered) without exercise. Femur and tibia were analyzed using radiographic, micro-CT, and histomorphometric techniques. Exercise combined with a hard diet significantly increased cortical bone density, mineral apposition rate, and bone formation rate in long bones. In contrast, exercise with a soft diet attenuated these osteogenic responses, while bone resorption activity remained comparable across groups. Serum corticosterone levels were elevated in soft diet groups, whereas serum sclerostin levels were higher in hard diet exercise groups. Additionally, serum insulin-like growth factor-1 (IGF-1) was reduced in the soft diet exercise group compared with the hard diet exercise group. These results suggest that a soft diet compromises exercise-induced gains in bone mineral density and bone formation, highlighting the importance of masticatory stimulation in optimizing skeletal adaptation in the growth stage.

The receptor activator of NF-κB ligand (RANKL)-binding peptide is known to accelerate bone morphogenetic protein (BMP)-2-induced bone formation. Cholesterol-bearing pullulan (CHP)-OA nanogel-crosslinked PEG gel (CHP-OA nanogel-hydrogel) was shown to release the RANKL-binding peptide sustainably; however, an appropriate scaffold for peptide-accelerated bone formation is not determined yet. This study compares the osteoconductivity of CHP-OA hydrogel and another CHP nanogel, CHP-A nanogel-crosslinked PEG gel (CHP-A nanogel–hydrogel), in the bone formation induced by BMP-2 and the peptide. A calvarial defect model was performed in 5-week-old male mice, and scaffolds were placed in the defect. In vivo μCT was performed every week. Radiological and histological analyses after 4 weeks of scaffold placement revealed that the calcified bone area and the bone formation activity at the defect site in the CHP-OA hydrogel were significantly lower than those in the CHP-A hydrogel when the scaffolds were impregnated with both BMP-2 and the RANKL-binding peptide. The amount of induced bone was similar in both CHP-A and CHP-OA hydrogels when impregnated with BMP-2 alone. In conclusion, CHP-A hydrogel could be an appropriate scaffold compared to the CHP-OA hydrogel when the local bone formation was induced by the combination of RANKL-binding peptide and BMP-2, but not by BMP-2 alone.

تعد ملوحة التربة أو ملوحة مياه الري من أهم المشاكل التي تواجه قطاع الزراعة في كثير من مناطق العالم، لهذا أصبح تحديد الأصناف النباتية الوراثية المتحملة للملوحة أمر بالغ الأهمية لتحسين الناتج النهائي للمحصول. لذلك تم إجراء سلسلة من التجارب المعملية لتقييم استجابة (9) أصناف من أصناف القمح الصلب (Desf durum Triticum) لمستويات مختلفة من الملوحة. نفذت التجارب وفق تصميم القطاعات العشوائية الكاملة بثلاثة مكررات. تم زراعة بذور القمح في أطباق بتري تحتوي على ورقة ترشيح. وتم معاملة البذور بتراكيز مختلفة من المحلول الملحي (0، 50، 100، 150) مل مول من كلوريد الصوديوم). حفظت الأطباق في الظلام في درجة حرارة الغرفة عند 25م درجة مئوية لمدة (8) أيام. تم خلال هذه الفترة التأكد من إضافة الماء أو المحلول الملحي لكل الأطباق حسب التركيز المطلوب. إضافة إلى البيانات الخاصة بالإنبات. بعد (8) أيام من الزرع تم إنهاء التجربة، وتجميع البيانات الخاصة بنسبة الانبات، معدل الانبات، متوسط الانبات اليومي، طول السويقة وطول الجذر، وزن البادرات الطازج والجاف. أظهرت النتائج أن استجابة الأنماط الوراثية للملوحة مختلفة عند التركيزات الأعلى من (mM NaCI 100)، حيث انخفض معدل الإنبات، ومتوسط الإنبات اليومي، وانخفضت نسبة الإنبات النهائية في غالبية التراكيب الوراثية مقارنة بالشاهد (الكنترول). كما أظهرت النتائج أنه عند المستوى العالي من الملوحة (mM NaCI 100) انخفض طول الساق، والجذر، والوزن الجاف، وقوة البادرات. كما أوضحت النتائج أن الملوحة تؤثر على نمو الجذر بشكل أشد من نمو الساق للبادرات إضافة إلى أن تأثير الملوحة كان أشد على الوزن الجاف للبادرات. وتوصي الدراسة باعتماد كلا من الوزن الجاف، وطول الجذر، وقوة البادرة كمعايير جيدة لاختبار تحمل الأصناف المختلفة للقمح الصلب للملوحة في مراحل الإنبات.