The inhibitory effect of melatonin on osteoclastogenesis of RAW 264.7 cells in low concentrations of RANKL and MCSF

Effects of bone surface topography and chemistry on macrophage polarization

Surface structure plays a crucial role in determining cell behavior on biomaterials, influencing cell adhesion, proliferation, differentiation, as well as immune cells and macrophage polarization. While grooves and ridges stimulate M2 polarization and pits and bumps promote M1 polarization, these structures do not accurately mimic the real bone surface. Consequently, the impact of mimicking bone surface topography on macrophage polarization remains unknown. Understanding the synergistic sequential roles of M1 and M2 macrophages in osteoimmunomodulation is crucial for effective bone tissue engineering. Thus, exploring the impact of bone surface microstructure mimicking biomaterials on macrophage polarization is critical. In this study, we aimed to sequentially activate M1 and M2 macrophages using Poly-L-Lactic acid (PLA) membranes with bone surface topographical features mimicked through the soft lithography technique. To mimic the bone surface topography, a bovine femur was used as a model surface, and the membranes were further modified with collagen type-I and hydroxyapatite to mimic the bone surface microenvironment. To determine the effect of these biomaterials on macrophage polarization, we conducted experimental analysis that contained estimating cytokine release profiles and characterizing cell morphology. Our results demonstrated the potential of the hydroxyapatite-deposited bone surface-mimicked PLA membranes to trigger sequential and synergistic M1 and M2 macrophage polarizations, suggesting their ability to achieve osteoimmunomodulatory macrophage polarization for bone tissue engineering applications. Although further experimental studies are required to completely investigate the osteoimmunomodulatory effects of these biomaterials, our results provide valuable insights into the potential advantages of biomaterials that mimic the complex microenvironment of bone surfaces.

Histopathological evaluation of the effect of melatonin gel on bone regeneration in rat model

Background

The purpose of this research was to investigate the effects of different doses of topical melatonin gel on bone regeneration in rat calvarial defects using histological analysis.

Materials and Methods

Fifteen adult female Wistar rats weighing approximately 200 g were used and 8 mm in diameter defects were created in their calvaria. The rats were divided into three groups: 1.2% melatonin gel, 5% melatonin gel, and the control group. The animals were sacrificed after 4 weeks. Hematoxylin and eosin staining were used to prepare histological sections. Statistical analysis was performed using the Analysis of variance and Tukey's post-hoc test. P < 0.05 was considered significant.

Results

The results showed a significant difference in rate of ossification (P < 0.001), area of new capillaries (P = 0.002), and mean degree of inflammation (P < 0.001) between the three groups. Comparing groups pairwise, degree of inflammation (P = 0.003) and area of new capillaries (P = 0.019) were significantly lower in the 5% melatonin gel group than the 1.2% melatonin gel group (P = 0.003). The percentage of ossification was substantially greater in the 5% melatonin gel group than in the control and 1.2% melatonin gel groups (P < 0.001).

Conclusion

Within the limitations of this animal study, our findings revealed that melatonin gel can be used as a stimulant of bone formation. Outcomes in this study show increased percentage of ossification in the melatonin groups when compared with the control, in a dose-dependent manner, as 5% melatonin gel has a greater effect on ossification.

Measuring and Modeling Macrophage Growth using a Lab-on-CMOS Capacitance Sensing Microsystem

We report on the use of a lab-on-CMOS biosensor platform for quantitatively tracking the growth of RAW 264.7 murine Balb/c macrophages. We show that macrophage growth over a wide sensing area correlates linearly with an average capacitance growth factor resulting from capacitance measurements at a plurality of electrodes dispersed in the sensing area. We further show a temporal model that captures the cell evolution in the area of interest over long periods (e.g., 30 hours). The model links the cell numbers and the average capacitance growth factor associated with the sensing area to describe the observed growth kinetics.

Hormone and implant osseointegration: Elaboration of the relationship among function, preclinical, and clinical practice

As clusters of peptides or steroids capable of high-efficiency information transmission, hormones have been substantiated to coordinate metabolism, growth, development, and other physiological processes, especially in bone physiology and repair metabolism. In recent years, the application of hormones for implant osseointegration has become a research hotspot. Herein, we provide a comprehensive overview of the relevant reports on endogenous hormones and their corresponding supplementary preparations to explore the association between hormones and the prognosis of implants. We also discuss the effects and mechanisms of insulin, parathyroid hormone, melatonin, vitamin D, and growth hormone on osseointegration at the molecular and body levels to provide a foothold and guide future research on the systemic conditions that affect the implantation process and expand the relative contraindications of the implant, and the pre-and post-operative precautions. This review shows that systemic hormones can regulate the osseointegration of oral implants through endogenous or exogenous drug-delivery methods.

Effect of melatonin/BMP-2 co-delivery scaffolds on the osteoclast activity

Bone morphogenetic protein two (BMP-2) has been widely used as an osteoinductive agent in the treatment of bone diseases. However, some side effects, such as osteoclast activation have emerged when it was used at high doses. In this study, by considering the osteoclast-suppressing capability of melatonin (MEL), its effect on osteoclast differentiation induced by BMP-2 was investigated. These two factors, MEL and BMP-2, were embedded into chitosan/hydroxyapatite (HAp) scaffolds that were characterized morphologically by scanning electron microscopy (SEM) and micro-computed tomography (μ-CT). Release profiles of MEL and BMP-2 from scaffolds were determined in vitro and then, the differentiation of RAW 264.7 cells to osteoclasts was investigated on the scaffolds. Results of tartrate-resistant acid phosphatase (TRAP) staining, SEM imaging and expression of cathepsin K gene showed that, in the presence of BMP-2, osteoclast differentiation increased, whereas it decreased in MEL and MEL/BMP-2 embedded scaffolds suggesting that melatonin successfully attenuated osteoclast differentiation induced by BMP-2. Thus, the MEL/BMP-2 loaded chitosan/HAp scaffolds that have dual function in enhancing bone formation and inhibiting osteoclast activity are recommended biomaterials in the field of bone regeneration.

Scaffold-based osteogenic dual delivery system with melatonin and BMP-2 releasing PLGA microparticles

The growing safety problems about the use of bone morphogenetic protein 2 (BMP-2) is one of the recent issues that was improved by using low doses of BMP-2 with the support of other osteoinductive agents and/or using appropriate carriers. The aim of the present study is to investigate the effect of scaffold-based dual release system including melatonin (MEL) and BMP-2 loaded polylactic-co-glycolic acid (PLGA) microparticles on the osteogenic activity of pre-osteoblastic MC3T3-E1 cells. MEL and BMP-2 loaded microparticles were prepared by double emulsion solvent evaporation method in the average diameters of ~2 µm and ~11 µm, respectively and loaded into chitosan/hydroxyapatite (HAp) scaffolds. In vitro MC3T3-E1 culture studies were carried out comparatively with blank scaffolds, single (BMP-2 or MEL) releasing groups and dual (BMP-2 and MEL) releasing group. Microscopic observations and hematoxylin/eosin staining showed enhanced number of cells and dense ECM in dual release group. The expressions of differentiation markers, Runt-related transcription factor 2 (RUNX2) and alkaline phosphatase (ALP) and also mineralization were higher in dual release group than that of the other groups. Our findings showed that BMP-2 at low doses (~20 ng per scaffold) was sufficient in terms of osteogenic activity with controlled release systems where it was used in combination with MEL (~10 µg per scaffold).