Histological and Radiological Evaluation of Low-Intensity Pulsed Ultrasound Versus Whole Body Vibration on Healing of Mandibular Bone Defects in Rats

Boron-Doped Nano Hydroxyapatite Grafts for Bone Regeneration in Rat Mandibular Defects

The aim of this study was to evaluate the potential effects of boron-doped nano hydroxyapatite grafts on craniofacial bone regeneration in critical bone defects in the mandibular corpus of rats, in terms of scintigraphic and histopathological aspects. Forty Wistar albino rats, with an average weight of 200-220 g, aged 16-18 weeks, and all male, were used in the study. The rats were randomly assigned to five groups, each containing 8 rats, as follows: group C1 (no procedure applied to the mandible), group C2 (surgical defect created in the mandible but no treatment applied), group nHA (nano hydroxyapatite applied to the surgical defect area), group nHA + B1 (nano hydroxyapatite + 1% boron applied to the surgical defect area), and group nHA + B2 (nano hydroxyapatite + 2% boron applied to the surgical defect area). A standard 4 × 4 mm full-thickness transosseous bone defect was created in the mandibular corpus of all rats, except for those in group C1. The bone defect in the rats in group C2 was left to heal naturally. Nano hydroxyapatite (nHA), nano hydroxyapatite + 1% boron, and nano hydroxyapatite + 2% boron were applied to the surgical defect areas of the other three groups, respectively. Bone scintigraphy was performed on all rats on days 0 (following the surgical procedure) and 28 of the experimental period. At the end of the 28th day, the animals were sacrificed, and tissue samples were collected for histological examination. A standard grading system was used to evaluate fracture healing. When the groups were compared in terms of bone healing histopathological scores, a statistically significant difference was observed between group C1 and the other groups (p < 0.005). In the statistical evaluation made according to the histopathological mean scores, the least improvement was observed in group C2. No statistically significant difference was observed between group nHA and group nHA + B1 and group C2 and between group nHA and group nHA + B1 in terms of bone healing scores (p > 0.005). A statistically significant difference was found between group nHA + B2 and group C2 (p = 0.026). Although there was no statistically significant difference in histopathological scores, the mean score closest to group C1 was observed in group nHA + B2. A statistically significant difference was observed between the groups in the scintigraphic evaluation performed on the 28th day of the experimental procedure, and the difference was between group C1 and group nHA + B1 and between group nHA and group nHA + B1 (p = 0.004; p = 0.028, p < 0.005). In the comparison of the values obtained on days 0 and 28 within the group, a statistically significant change was observed in group nHA + B1 and group nHA + B2 (p < 0.005). When the results of the present study were evaluated, it was thought that the boron-doped nHA graft biomaterials may have positive effects on bone healing. Providing a different perspective for the development of an alternative new treatment modality that can be locally applied in the treatment of fractures a serious and common health problem can be interpreted as an important outcome of the present study. We believe that this study will serve as a preliminary study for more comprehensive future studies on this subject.

Influence of Low-Intensity Pulsed Ultrasound Parameters on the Bone Mineral Density in Rat Model: A Systematic Review

OBJECTIVE

Bone recovery typically depends on the age of organisms or the prevalence of metabolic disorders such as osteoporosis, which is a metabolic condition characterized by decreased bone strength and bone mineral density (BMD). Therefore, low-intensity pulsed ultrasound (LIPUS), a non-invasive method for osteogenic stimulation, presents promising results. However, heterogeneity in animal study designs is a typical characteristic. Hence, we conducted a systematic review to evaluate the effectiveness of LIPUS in the recovery of experimental bone defects using rat models. We examined the areal and volumetric BMD to identify LIPUS doses to be applied and evaluated the accuracy reported by previous studies.

METHODS

The Virtual Health Library regional portal, PubMed, Embase, EBSCOhost, Scopus and CAPES were reviewed for animal studies that compared fracture treatments based on LIPUS with sham or no treatments using rat models and reported BMD as an outcome. The tool provided by the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) and the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES) checklist were used to assess the bias and quality of such studies.

RESULTS

Of the six studies reviewed, the most frequently used LIPUS dose had an ultrasonic frequency of 1.0 MHz, repetition rate of 0.1 kHz and pulse duration of 2000 μs. An intensity (ISATA) of 30 mW/cm2 was the most preferred for bone recovery. However, the BMD could not solely irrefutably evaluate the effectiveness of LIPUS in bone recovery as the results were discordant with each other. The discrepancies in experimental methodologies, low-quality classifications and high risk of bias in the selected studies, however, did not validate the undertaking of a meta-analysis.

CONCLUSION

On the basis of the BMD results, no sufficient evidence was found to recommend the use of LIPUS for bone recovery in rat models. Thus, this systematic review indicates that the accuracy of such reports must be improved to improve their scientific quality to facilitate a transition of LIPUS applications from pre-clinical research to clinic use.

Effect of Low-Intensity Pulsed Ultrasound on the Graft-Bone Healing of Artificial Ligaments: An In Vitro and In Vivo Study

BACKGROUND

As many researchers have focused on promoting the graft-bone healing of artificial ligaments, even with numerous chemical coatings, identifying a biosafe, effective, and immediately usable method is still important clinically.

PURPOSE

(1) To determine whether a low-intensity pulsed ultrasound system (LIPUS) promotes in vitro cell viability and osteogenic differentiation and (2) to assess the applicability and effectiveness of LIPUS in promoting the graft-bone healing of artificial ligaments in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

Polyethylene terephthalate (PET) sheets and grafts were randomly assigned to control and LIPUS groups. MC3T3-E1 preosteoblasts were cultured on PET sheets. Cell viability and morphology were evaluated using a live/dead viability assay and scanning electron microscopy. Alkaline phosphatase activity, calcium nodule formation, and Western blot were evaluated for osteogenic differentiation. For in vivo experiments, the effect of LIPUS was evaluated via an extra-articular graft-bone healing model in 48 rabbits: the osteointegration and new bone formation were tested by micro-computed tomography and histological staining, and the graft-bone bonding was tested by biomechanical testing.

RESULTS

Cell viability was significantly higher in the LIPUS group as compared with control (living and dead compared between control and LIPUS groups, P = .0489 vs P = .0489). Better adherence of cells and greater development of extracellular matrix were observed in the LIPUS group. Furthermore, LIPUS promoted alkaline phosphatase activity, calcium nodule formation, and the protein expression of collagen 1 (P = .0002) and osteocalcin (P = .0006) in vitro. Micro-computed tomography revealed higher surrounding bone mass at 4 weeks and newly formed bone mass at 8 weeks in the LIPUS group (P = .0014 and P = .0018). Histological analysis showed a narrower interface and direct graft-bone contact in the LIPUS group; the surrounding bone area at 4 weeks and the mass of newly formed bone at 4 and 8 weeks in the LIPUS group were also significantly higher as compared with control (surrounding bone, P < .0001; newly formed bone, P = .0016 at 4 weeks and P = .005 at 8 weeks). The ultimate failure load in the LIPUS group was significantly higher than in the control group (P < .0001 at 4 weeks; P = .0008 at 8 weeks).

CONCLUSION

LIPUS promoted the viability and osteogenic differentiation of MC3T3-E1 preosteoblasts in vitro and enhanced the graft-bone healing of PET artificial ligament in vivo.

CLINICAL RELEVANCE

LIPUS is an effective physical stimulation to enhance graft-bone healing after artificial ligament implantation.

From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues

Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.

Effects of mechanical stimuli on structure and organization of bone nanocomposites in rats with glucocorticoid-induced osteoporosis

Objective. Clinical use of glucocorticoids is a frequent cause of secondary osteoporosis, which reduces the mineral density of bones and results in pathological fractures. Mechanical stimulation as non-physiological high-frequency vibration with low acceleration prevents the loss of a crystalline component and stimulates the anabolic remodeling of the bone. The aim of the present research was to assess the impact of mechanical vibration on the bone structure in rats, which received glucocorticoids.Methods. Wistar rats were randomized into three groups: Vehicle control (Veh), Methylprednisolone sodium succinate (Mps), and Mps combined with whole-body vibration (WBV). Rats of Mps+WBV and Mps groups received 3 mg/kg/day of methylprednisolone every other day for 24 weeks and rats of Veh group received 0.9% saline (sodium chloride). The group of rats Mps+WBV was subjected to WBV for 30 minutes per day for five days a week with parameters 0.3 g and frequency 50 Hz. Relative amount of crystalline component and collagen in the bones was determined by X-ray diffraction (XRD) and calcium level - by atomic absorption spectroscopy. Bone tissue metabolism was assessed by determining the concentration of markers, in particular osteocalcin and Tartrate-resistant acid phosphatase (TRAP5b).Results. Glucocorticoids induced a considerable increase in the rats body mass (+13%) and decreased the content of mineral component in the femoral neck (-17%) in Mps group compared with Veh. The process of the bone metabolism was significantly accelerated, which is proven by an increased level of remodeling markers. It should be mentioned that WBV did not allow significant decrease in mineral component of the bone to 16th week of the experiment compared with Mps group, although these parameters did not achieve the indices in the Vehicle control group (-10%). Our investigation allows to suggest that mechanical high-frequency vibration of low intensity can partially inhibit the harmful consequences of glucocorticoids on bone structure in rats. Despite the positive impact of vibration on the bone tissue after Mps introduction in the 8th-16th week, this influence was not statistically reliable in the 24th week of the experiment.Conclusions. The results of our investigation on animal model indicate that non-physiological vertical mechanical vibrations are an effective means to prevent loss of a mineral bone component during treatment with glucocorticoids.