Melatonin promotes angiogenesis during repair of bone defects: a radiological and histomorphometric study in rabbit tibiae

Regeneration of critical-sized grade II furcation using a novel injectable melatonin-loaded scaffold

BACKGROUND

Periodontal regenerative therapy using bone-substituting materials has gained favorable clinical significance in enhancing osseous regeneration. These materials should be biocompatible, osteogenic, malleable, and biodegradable. This study assessed the periodontal regenerative capacity of a novel biodegradable bioactive hydrogel template of organic-inorganic composite loaded with melatonin.

MATERIALS AND METHODS

A melatonin-loaded alginate-chitosan/beta-tricalcium phosphate composite hydrogel was successfully prepared and characterized. Thirty-six critical-sized bilateral class II furcation defects were created in six Mongrel dogs, and were randomly divided and allocated to three cohorts; sham, unloaded composite, and melatonin-loaded. Periodontal regenerative capacity was evaluated via histologic and histomorphometric analysis.

RESULTS

Melatonin-treated group showed accelerated bone formation and advanced maturity, with a significant twofold increase in newly formed inter-radicular bone compared with the unloaded composite. The short-term regenerative efficacy was evident 4 weeks postoperatively as a significant increase in cementum length concurrent with reduction of entrapped epithelium. After 8 weeks, the scaffold produced a quality of newly synthesized bone similar to normal compact bone, with potent periodontal ligament attachment.

CONCLUSIONS

Melatonin-loaded hydrogel template accelerated formation and enhanced quality of newly formed bone, allowing complete periodontal regeneration. Furthermore, the scaffold prevented overgrowth and entrapment of epithelial cells in furcation defects.

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.

The Effect of Melatonin on Nasal Septal Wound Healing in an Experimental Animal Model

The purpose of our study was to examine the effect of melatonin (MLT) on wound healing in the nasal septum. Twenty-two Sprague-Dawley rats of the male sex were included in this experimental study. Nasal septal perforation (NSP), about 2 mm in diameter, was formed in each rat. MLT was applied topically to the subjects in the study group and saline was applied topically to the subjects in the control group once a day for 14 days. On day 14, the rats were sacrificed and the nasal septums of the subjects were resected for pathological evaluation. In the NSP area, degeneration and regeneration of nasal septal epithelium; degeneration and regeneration of the septal cartilage; number of cells involved in wound healing such as acute inflammatory cells (leukocytes), fibroblast, eosinophil, and giant cell; capillary vessel intensity; granulation tissue formation; and collagen intensity parameters were evaluated histopathologically. The macroscopic size and histopathologic examination results of NSPs were statistically analyzed. In the MLT group, the epithelium regeneration, cartilage regeneration, fibroblast number, collagen density, vascularity, and granulation formation were significantly higher, and the epithelial degeneration and acute inflammatory cells density were significantly lower, in the NSP area (p < 0.05). In addition, macroscopic healing was significantly higher in the MLT group (p = 0.044 and <0.05). Local application of MLT accelerates nasal septal wound healing. With this feature, the usage of MLT can be promising to prevent the formation of NSP.

Does Melatonin Associated with Nanostructured Calcium Phosphate Improve Alveolar Bone Repair?

Background and objectives: Calcium phosphates have been widely used as bone substitutes, but their properties are limited to osteoconduction. The association of calcium phosphates with osteoinductive bioactive molecules has been used as a strategy in regenerative medicine. Melatonin has been studied due to its cell protection and antioxidant functions, reducing osteoclastic activity and stimulating newly formed bone. This study aimed to evaluate the effect of topical application of melatonin associated with nanostructured carbonated hydroxyapatite microspheres in the alveolar bone repair of Wistar rats through histological and histomorphometric analysis. Materials and Methods: Thirty female Wistar rats (300 g) were used, divided randomly into three experimental groups (n = 10), G1: nanostructured carbonated hydroxyapatite microspheres associated with melatonin gel (CHA-M); G2: nanostructured carbonated hydroxyapatite (CHA); G3: blood clot (without alveolar filling). The animals were euthanized after 7 and 42 days of the postoperative period and processed for histological and histomorphometric evaluation. Kruskal-Wallis and Dunn's post-test were applied to investigate statistical differences between the groups at the same time point for new bone and connective tissue variables. Mann-Whitney was used to assess statistical differences between different time points and in the biomaterial variable. Results: Results showed a greater volume of residual biomaterial in the CHA-M than the CHA group (p = 0.007), and there were no significant differences in terms of newly formed bone and connective tissue between CHA and CHA-M after 42 days. Conclusions: This study concluded that both biomaterials improved alveolar bone repair from 7 to 42 days after surgery, and the association of CHA with melatonin gel reduced the biomaterial's biodegradation at the implanted site but did not improve the alveolar bone repair.

Histological and Immunohistochemical Analysis of the Effects of Topical Melatonin Treatment Associated with Collagen Sponge and rhBMP-2 Protein on Bone Remodeling

Extensive bone defect healing is an important health issue not yet completely resolved. Different alternative treatments have been proposed but, in face of a critical bone defect, it is still very difficult to reach a complete regeneration, with the new-formed bone presenting all morphological and physiological characteristics of a normal, preinjury bone. Topical melatonin use has shown as a promising adjuvant for bone regeneration due to its positive effects on bone metabolism. Thus, to search for new, safe, biological techniques that promote bone repair and favor defect healing, we hypothesized that there is a synergistic effect of melatonin treatment associated with rhBMP-2 to guide bone regeneration. This study aimed to investigate bone repair effects of topical melatonin administration in different concentrations (1, 10, and 100 µg), associated or not with rhBMP-2. Surgical-induced bone defect healing was qualitatively evaluated through histopathological analysis by light microscopy. Additionally, quantitative stereology was performed in immunohistochemistry-prepared tissue to identify angiogenic, osteogenic, and osteoclastogenic factors. Quantification data were compared between groups by the ANOVA/Tukey test and differences were considered significant when p < 0.05. Our results showed that the presence of the scaffold in the bone defect hindered the process of bone repair because in the group treated with "blood clot + scaffold" the results of bone formation and immunolabeling were reduced in comparison with all other groups (treated with melatonin alone or in association with rhBMP-2). Statistical analysis revealed a significant difference between the control group (bone defect + blood clot), and groups treated with different concentrations of melatonin in association with rhBMP-2, indicating a positive effect of the association for bone repair. This treatment is promising once it becomes a new safe alternative technique for the clinical treatment of fractures, bone defects, and bone grafts. Our results support the hypothesis of the safe use of the association of melatonin and rhBMP-2 and have established a safe and effective dose for this experimental treatment.

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.

Melatonin Accelerates Osteoporotic Bone Defect Repair by Promoting Osteogenesis-Angiogenesis Coupling

Previous studies have revealed that melatonin could play a role in anti-osteoporosis and promoting osteogenesis. However, the effects of melatonin treatment on osteoporotic bone defect and the mechanism underlying the effects of melatonin on angiogenesis are still unclear. Our study was aimed to investigate the potential effects of melatonin on angiogenesis and osteoporotic bone defect. Bone marrow mesenchymal stem cells (BMSCs) were isolated from the femur and tibia of rats. The BMSC osteogenic ability was assessed using alkaline phosphatase (ALP) staining, alizarin red S staining, qRT-PCR, western blot, and immunofluorescence. BMSC-mediated angiogenic potentials were determined using qRT-PCR, western blot, enzyme-linked immunosorbent assay, immunofluorescence, scratch wound assay, transwell migration assay, and tube formation assay. Ovariectomized (OVX) rats with tibia defect were used to establish an osteoporotic bone defect model and then treated with melatonin. The effects of melatonin treatment on osteoporotic bone defect in OVX rats were analyzed using micro-CT, histology, sequential fluorescent labeling, and biomechanical test. Our study showed that melatonin promoted both osteogenesis and angiogenesis in vitro. BMSCs treated with melatonin indicated higher expression levels of osteogenesis-related markers [ALP, osteocalcin (OCN), runt-related transcription factor 2, and osterix] and angiogenesis-related markers [vascular endothelial growth factor (VEGF), angiopoietin-2, and angiopoietin-4] compared to the untreated group. Significantly, melatonin was not able to facilitate human umbilical vein endothelial cell angiogenesis directly, but it possessed the ability to promote BMSC-mediated angiogenesis by upregulating the VEGF levels. In addition, we further found that melatonin treatment increased bone mineralization and formation around the tibia defect in OVX rats compared with the control group. Immunohistochemical staining indicated higher expression levels of osteogenesis-related marker (OCN) and angiogenesis-related markers (VEGF and CD31) in the melatonin-treated OVX rats. Then, it showed that melatonin treatment also increased the bone strength of tibia defect in OVX rats, with increased ultimate load and stiffness, as performed by three-point bending test. In conclusion, our study demonstrated that melatonin could promote BMSC-mediated angiogenesis and promote osteogenesis-angiogenesis coupling. We further found that melatonin could accelerate osteoporotic bone repair by promoting osteogenesis and angiogenesis in OVX rats. These findings may provide evidence for the potential application of melatonin in osteoporotic bone defect.

Melatonin ameliorates aging-related impaired angiogenesis in gastric endothelial cells via local actions on mitochondria and VEGF-survivin signaling

Tissue injury healing is impaired in aging, and this impairment is caused in part by reduced angiogenesis. Melatonin, a neuroendocrine hormone that regulates sleep and circadian rhythm, is also produced in the gastrointestinal tract. The expression of melatonin receptors MT1 and MT2 in gastric endothelial cells and their roles in aging-related impairment of gastric angiogenesis have not been examined. We hypothesized that MT1 and MT2 expression is reduced in gastric endothelial cells of aging rats and that melatonin treatment can upregulate their expression and improve angiogenesis. We examined the expression of MT1 and MT2 in gastric endothelial cells (GECs) isolated from young and aging rats. We also examined the effects of melatonin treatment on angiogenesis, GEC mitochondrial function, expression of vascular endothelial growth factor (VEGF), its signaling receptor (VEGFR-2), and the inhibitor of apoptosis protein, survivin. Young and aging GECs expressed MT1 (in the cytoplasm and mitochondria) and MT2 (in nucleus and mitochondria). In aging GECs, MT1 and MT2 levels, in vitro angiogenesis, and mitochondrial membrane potential were significantly reduced (by 1.5-fold, 1.9-fold, 3.1-fold, and 1.63-fold, respectively) compared with young GECs. Melatonin treatment of aging GECs significantly increased MT1 and MT2 expression compared with the controls, induced nuclear translocation of MT1, and significantly ameliorated the aging-related impairment of angiogenesis and mitochondrial function. Aging GECs have significantly reduced MT1 and MT2 expression, angiogenesis, and mitochondrial membrane potential compared with young GECs. Treatment of aging GECs with melatonin increases expression of VEGF receptor and survivin and ameliorates aging-related impaired angiogenesis and mitochondrial function.NEW & NOTEWORTHY This study showed reduced expression of melatonin receptors MT1 and MT2, angiogenesis, and mitochondrial function in gastric endothelial cells (GECs) isolated from aging rats. Treatment of aging GECs with melatonin increases expression of VEGF receptor and survivin and ameliorates aging-related impaired angiogenesis and mitochondrial function. These studies provide new insight into the mechanisms of the aging-related impairment of angiogenesis and delayed tissue injury healing and provide a rationale for melatonin treatment to reverse these abnormalities.

Melatonin as a Trigger of Therapeutic Bone Regenerating Capacity in Biomaterials

Bone defects are usually treated with bone grafting. Several synthetic biomaterials have emerged to replace autologous and allogeneic bone grafts, but there are still shortcomings in bone regeneration. Melatonin has demonstrated a beneficial effect on bone metabolism with the potential to treat fractures, bone defects, and osteoporosis. The hormone promoted osteogenesis, inhibited osteoclastogenesis, stimulated angiogenesis, and reduced peri-implantitis around the graft. Recently, a growing number of studies showed beneficial effects of melatonin to treat bone defects. However, cellular and molecular mechanisms involved in bone healing are still poorly understood. In this review, we recapitulate the potential mechanisms of melatonin, providing a new horizon to the clinical treatment of bone defects.

Insight into the roles of melatonin in bone tissue and bone‑related diseases (Review)

Bone‑related diseases comprise a large group of common diseases, including fractures, osteoporosis and osteoarthritis (OA), which affect a large number of individuals, particularly the elderly. The progressive destruction and loss of alveolar bone caused by periodontitis is a specific type of bone loss, which has a high incidence and markedly reduces the quality of life of patients. With the existing methods of prevention and treatment, the incidence and mortality of bone‑related diseases are still gradually increasing, creating a significant financial burden to societies worldwide. To prevent the occurrence of bone‑related diseases, delay their progression or reverse the injuries they cause, new alternative or complementary treatments need to be developed. Melatonin exerts numerous physiological effects, including inducing anti‑inflammatory and antioxidative functions, resetting circadian rhythms and promoting wound healing and tissue regeneration. Melatonin also participates in the health management of bone and cartilage. In the present review, the potential roles of melatonin in the pathogenesis and progression of bone injury, osteoporosis, OA and periodontitis are summarized. Furthermore, the high efficiency and diversity of the physiological regulatory effects of melatonin are highlighted and the potential benefits of the use of melatonin for the clinical prevention and treatment of bone‑related diseases are discussed.

Role of melatonin in the angiogenesis potential; highlights on the cardiovascular disease

Melatonin possesses multi-organ and pleiotropic effects with potency to control angiogenesis at both molecular and cellular levels. To date, many efforts have been made to control and regulate the dynamic of angiogenesis modulators in a different milieu. The term angiogenesis or neovascularization refers to the development of de novo vascular buds from the pre-existing blood vessels. This phenomenon is tightly dependent on the balance between the pro- and anti-angiogenesis factors which alters the functional behavior of vascular cells. The promotion of angiogenesis is thought to be an effective strategy to accelerate the healing process of ischemic changes such as infarcted myocardium. Of note, most of the previous studies have focused on the anti-angiogenesis capacity of melatonin in the tumor niche. To the best of our knowledge, few experiments highlighted the melatonin angiogenesis potential and specific regulatory mechanisms in the cardiovascular system. Here, we aimed to summarize some previous experiments related to the application of melatonin in cardiovascular diseases such as ischemic injury and hypertension by focusing on the regulatory mechanisms.

Thymosin β4: A Multi-Faceted Tissue Repair Stimulating Protein in Heart Injury

Thymosin Beta-4 (Tβ4) is known as a major pleiotropic actin-sequestering protein that is involved in tumorigenesis. Tβ4 is a water-soluble protein that has different promising clinical applications in the remodeling and ulcerated tissues repair following myocardial infarction, stroke, plasticity and neurovascular remodeling of the Peripheral Nervous System (PNS) and the Central Nervous System (CNS). On the other hand, similar effects have been observed for Tβ4 in other kinds of tissues, including cardiac muscle tissue. In recent reports, as it activates resident epicardial progenitor cells and modulates inflammatory-caused injuries, Tβ4 has been suggested as a promoter of the survival of cardiomyocytes. Furthermore, Tβ4 may act in skeletal muscle and different organs in association/synergism with numerous other tissue repair stimulating factors, including melatonin and C-fiber-derived peptides. For these reasons, the present review highlights the promising role of Tβ4 in cardiac healing.

The effect of melatonin on prevention of bisphosphonate-related osteonecrosis of the jaw: an animal study in rats

Objectives

Melatonin induces human stem cells, converts pre-osteoblasts to mature osteoblasts, and reduces the duration of this transition. However, melatonin itself prevents activation of osteoclasts. Here, we evaluate the role of melatonin in prevention of bisphosphonate-related osteonecrosis of the jaw.

Materials and Methods

In this experimental-interventional study, 30 rats were evaluated in 3 groups. The first and second groups received saline and zoledronic acid, respectively, for 4 weeks and the third group received 4 weeks of zoledronic acid and 3 weeks of melatonin simultaneously. First-right-maxillary-molar extraction was performed for all animals, which were sacrificed after 4 weeks of recovery. The extraction sockets were examined histologically for the presence of osteonecrosis, number of osteoclasts and fibroblasts, severity of inflammation, and vascularization. Data were analyzed by chi-square, one-way ANOVA, Tukey, Kruskal–Wallis and Fisher’s exact statistical tests (α=0.05).

Results

Osteonecrosis was observed in 20%, 90%, and 70% of the first, second and third groups, respectively (P=0.008). The lowest number of osteoclasts and fibroblasts was seen in the third group.

Conclusion

Melatonin may effectively prevent some undesirable side effects of bisphosphonates. However, further studies are required to confirm the results of this study.

Effect of melatonin versus injectable platelet rich fibrin on critical wound healing in submandibular salivary glands of diabetic rats

Background

Diabetes mellitus (DM) has harmful effects on body organs, including submandibular salivary glands (SMGs). It impairs wound healing process that follow sialoadenectomy. Yet there is no complete cure to diabetes, the available medications tend to control the side effects of DM or manage insulin resistance. Herein we tried to investigate the possible effects of injectable platelet rich fibrin (i-PRF) and melatonin on wound healing in diabetic rats.

Material and methods

Surgical defects were created in SMGs of 30 rats after confirmation of DM induction. Then rats were randomly and equally allocated into three groups. Group I served as control group; group II received topically applied i-PRF, and group III received topically administrated melatonin. After 28 days all rats were euthanized, and SMGs were processed for histological and biochemical analysis.

Results

Both i-PRF and melatonin caused significant reduction of malondialdehyde (P < 0.0001) and caspase-3 (P < 0.001) and significant increase in vascular endothelial growth factors (P = 0.001,0.009 respectively) that increased SMGs regenerative capacity when compared to diabetic group. Melatonin showed superior results regarding the histomorphological structure of SMGs.

Conclusion

Melatonin and i-PRF can be possible candidates for improvement of wound healing events in SMGs of diabetic rats.

Melatonin loaded lecithin-chitosan nanoparticles improved the wound healing in diabetic rats

Wound healing in diabetic patients remains a worldwide problem that can cause amputations and even lead to death. This work aimed to produce lecithin-chitosan nanoparticles loaded with melatonin (MEL-NP) incorporated in a topical formulation to be evaluated for healing in the in vivo animal model for diabetes. To produce nanoparticles, an ethanolic solution containing soybean lecithin and melatonin was added dropwise to an aqueous solution of chitosan under sonication. The nanoparticles were physicochemical characterized and evaluated in vivo for toxicity using the Galleria mellonella model and its potential for wound healing in diabetic rats. The MEL-NPs presented a particle size of 160 nm and a zeta potential of 25 mV. The melatonin entrapment efficiency was 27%. Our results indicated that treatment with MEL-NP improved wound healing demonstrated by wound closure earlier than the other treatments evaluated. A desired therapeutic effect was achieved by MEL-NP in the induction of fibroblast and angiogenic proliferation. In addition, it was accompanied by an expressive collagen deposition. Considering the observed data, the MEL-NP developed could be used as a proof of concept to develop a promising strategy for the healing of diabetic wound.

A possible use of melatonin in the dental field: Protein adsorption and in vitro cell response on coated titanium

Melatonin (MLT) is widely known for regulating the circadian cycles and has been studied for its role in bone regeneration and inflammation. Its application as a coating for dental implants can condition the local microenvironment, affecting protein deposition on its surface and the cellular and tissue response. Using sol-gel coatings as a release vehicle for MLT, the aim of this work was to assess the potential of this molecule in improving the osseointegration and inflammatory responses of a titanium substrate. The materials obtained were physicochemically characterized (scanning electron microscopy, contact angle, roughness, Fourier-transform infrared spectroscopy, nuclear magnetic resonance, Si release, MLT liberation, and degradation) and studied in vitro with MC3T3-E1 osteoblastic cells and RAW264.7 macrophage cells. Although MLT application led to an increased gene expression of RUNX2 and BMP2 in 10MTL, it did not improve ALP activity. On the other hand, MLT-enriched sol-gel materials presented potential effects in the adsorption of proteins related to inflammation, coagulation and angiogenesis pathways depending on the dosage used. Using LC-MS/MS, protein adsorption patterns were studied after incubation with human serum. Proteins related to the complement systems (CO7, IC1, CO5, CO8A, and CO9) were less adsorbed in materials with MLT; on the other hand, proteins with functions in the coagulation and angiogenesis pathways, such as A2GL and PLMN, showed a significant adsorption pattern.

Experimental Study on the Influence of Apigenin K and Melatonin in Socket Preservation as Bone Stimulators: An Experimental Study in Beagle Dogs

The aim is to evaluate whether apigenin K and melatonin M5250 were able to stimulate bone formation after tooth extraction at one, two, and three months follow-up. Six male beagle dogs were used. Apigenin K and melatonin M5250 immersed in hemostatic collagen sponges were placed in the third and fourth premolar and the first molar extracted sockets; the second premolar was used as control. At one, two, and three months, bone core biopsies were performed, and picrosirius–hematoxylin was used for the staining process. In the first month, a higher amount of calcified bone tissue was observed in the melatonin (77.87% ± 1.2%) and apigenin K (69.81% ± 1.8%) groups than the control group (57.27% ± 0.54%), with apparent discrepancies in values between the three groups (p < 0.04). In the second month, there was a considerable improvement in the results in the areas with melatonin (79.81% ± 0.11%) than in those of apigenin K (71.65% ± 0.52%) and control (64.77% ± 0.44%) (p < 0.04). In the third month, the number of mature bone was similar to all the groups. The creation of new bone was significant in the melatonin group (82.78% ± 0.87%), followed by the apigenin K group (78.76% ± 0.43%) and the control group (57.27% ± 0.11%). From this experimental study in dogs, it can be concluded that melatonin and apigenin K can accelerate the process of mineralization of the bone matrix, and thus the creation of laminae in the early stages of healing (1 month). Less reabsorption of the post-extraction sockets can be expected with the topical application of melatonin and apigenin K. It seems that the stimulatory effects of bone healing induced by the topical application of melatonin and apigenin K are defect-size-dependent, being more evident in small defects compared to larger defects.

Melatonin: An atypical hormone with major functions in the regulation of angiogenesis

Melatonin (N-acetyl-5-methoxytryptamine), a pleotropic molecule with a wide distribution, has received considerable attention in recent years, mostly because of its various major effects on tissues or cells since it has both receptor-dependent and receptor-independent actions over a wide range of concentrations. These biological and physiological functions of melatonin include regulation of circadian rhythms by modulating the expression of core oscillator genes, scavenging the reactive oxygen species and reactive nitrogen species, modulating the immune system and inflammatory response, and exerting cytoprotective and antiapoptotic effects. Given the multiple critical roles of melatonin, dysregulation of its production or any disruption in signaling through its receptors may have contributed in the development of a wide range of disorders including type 2 diabetes, aging, immune-mediated diseases, hypertension, and cancer. Herein, we focus on the modulatory effects of melatonin on angiogenesis and its implications as a therapeutic strategy in cancer and related diseases.

Rapamycin could increase the effects of melatonin against age-dependent bone loss

Previous studies have demonstrated the beneficial effect of melatonin (MEL) on bone tissue and bone metabolism. Rapamycin (RAP) promotes osteoblast proliferation and inhibits osteoclast proliferation, and positively affects bone regeneration; however, reports about effects of RAP on bone loss for aged female rats with MEL administration are limited. This study investigated the impact of treatment with RAP on bone loss for aged female rats with MEL administration. Female Sprague-Dawley rats weighing approximately 520 g were randomly divided into 3 groups of 10: group CON, group MEL and group MEL + RAP and received saline, MEL, RAP plus MEL treatment until death at 12 weeks, respectively. The results of maintaining bone mass and bone strength with RAP plus MEL administration were evaluated by histology, microcomputerized tomography (Micro-CT), gene expression analysis and biomechanical testing. Results from this study indicated that MEL + RAP had stronger effects on the prevention and treatment of osteoporosis than MEL administration. Administration of MEL + RAP produced the strongest effects on bone parameters and strength for distal femurs and regulation of OPG/RANKL signalling pathway-related gene expression. These results seemed to indicate that RAP could increase the effects of MEL on age-dependent bone loss.

Melatonin improves the osseointegration of hydroxyapatite-coated titanium implants in senile female rats

The aim of this study was to confirm the effect of the systemic administration of melatonin on hydroxyapatite-coated titanium (HA-Ti) implants in senile osteopenic rats. For this study 24-month-old female Sprague-Dawley rats were used. The animals were randomly divided into two groups: a control group and a melatonin group and the bilateral femurs of all the rats received HA-Ti implants. Animals in the melatonin group received treatment with melatonin (30 mg/kg day). After a 12-week healing period, rats in the melatonin group revealed improved osseointegration compared to the control group, with the bone area ratio (BAR) and bone to implant contact (BIC) increased by 1.87-fold and 1.65-fold in histomorphometry, the quantitative results of implant osseointegration and peri-implant trabeculae, such as a higher bone volume per total volume (BV/TV), trabecular number (Tb.N), the mean connective density (Conn.D), trabecular thickness (Tb.Th), and a lower trabecular spacing (Tb.Sp) in micro-computed tomography (CT) evaluation and the maximum push-out force by 1.75-fold in push out tests. Additionally, compared with the control group, melatonin could significantly up-regulate the expression of the runt-related transcription factor 2 (Runx2), osteocalcin (OC) and osteoprotegerin (OPG) genes and down-regulate the expression of the RANKL gene. These findings suggest that systemic administration with melatonin is useful to improve the fixation of HA-coated implants even in osteopenic rats through promoting Runx2, OC and OPG gene expression and inhibiting RANKL gene expression.

Role of melatonin in controlling angiogenesis under physiological and pathological conditions

Angiogenesis depends on proangiogenic and anti-angiogenic molecules that regulate endothelial cell proliferation and migration. Well-regulated angiogenesis plays a pivotal role in many physiological conditions such as reproduction and embryonic development, while abnormal angiogenesis is also the basis of a variety of pathological processes including tumor metastasis and atherosclerotic plaque formation. Melatonin has a variety of biological effects, including inhibition of tumor metastasis, stabilizing atherosclerotic plaques, and the regulation of seasonal reproductive rhythms, etc. During certain pathophysiological processes, melatonin exerts different functions depending on its ability to regulate angiogenesis. This review reveals that melatonin has different effects on neovascularization under different physiological and pathological conditions. In tumors, in age-related ocular diseases, and in a hypoxic environment, melatonin inhibits neovascularization in tissues, while in gastric ulcers, skin lesions, and some physiologic processes, it promotes angiogenesis. We also speculate that melatonin may inhibit the neovascularization in atherosclerotic plaques, thus preventing the initiation and development of atherosclerosis. Most studies suggest that these effects are related to the role of melatonin in regulating of vascular endothelial growth factor and its receptors, but the specific regulatory mechanisms remain disparate, which may lead to the differential effects of melatonin on angiogenesis under different conditions. In this review, we thus summarize some seemingly contradictory mechanisms by which melatonin controls angiogenesis under different pathological and physiological conditions, and urge that the regulatory mechanisms be further studied.

The multiple protective roles and molecular mechanisms of melatonin and its precursor N-acetylserotonin in targeting brain injury and liver damage and in maintaining bone health

Melatonin is a neurohormone associated with sleep and wakefulness and is mainly produced by the pineal gland. Numerous physiological functions of melatonin have been demonstrated including anti-inflammation, suppressing neoplastic growth, circadian and endocrine rhythm regulation, and its potent antioxidant activity as well as its role in regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others. In this review, we summarize the recent advances related to the multiple protective roles of melatonin receptor agonists, melatonin and N-acetylserotonin (NAS), in brain injury, liver damage, and bone health. Brain injury, including traumatic brain injury, ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, and newborn perinatal hypoxia-ischemia encephalopathy, is a major cause of mortality and disability. Liver disease causes serious public health problems and various factors including alcohol, chemical pollutants, and drugs induce hepatic damage. Osteoporosis is the most common bone disease in humans. Due in part to an aging population, both the cost of care of fracture patients and the annual fracture rate have increased steadily. Despite the discrepancy in the pathophysiological processes of these disorders, time frames and severity, they may share several common molecular mechanisms. Oxidative stress is considered to be a critical factor in these pathogeneses. We update the current state of knowledge related to the molecular processes, mainly including anti-oxidative stress, anti-apoptosis, autophagy dysfunction, and anti-inflammation as well as other properties of melatonin and NAS. Particularly, the abilities of melatonin and NAS to directly scavenge oxygen-centered radicals and toxic reactive oxygen species, and indirectly act through antioxidant enzymes are disscussed. In this review, we summarize the similarities and differences in the protection provided by melatonin and/or NAS in brain, liver and bone damage. We analyze the involvement of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2), and melatonin receptor 1C (MT3) in the protection of melatonin and/or NAS. Additionally, we evaluate their potential clinical applications. The multiple mechanisms of action and multiple organ-targeted properties of melatonin and NAS may contribute to development of promising therapies for clinical trials.

Hyaluronic Acid/Bone Substitute Complex Implanted on Chick Embryo Chorioallantoic Membrane Induces Osteoblastic Differentiation and Angiogenesis, but not Inflammation

Microscopic and molecular events related to alveolar ridge augmentation are less known because of the lack of experimental models and limited molecular markers used to evaluate this process. We propose here the chick embryo chorioallantoic membrane (CAM) as an in vivo model to study the interaction between CAM and bone substitutes (B) combined with hyaluronic acid (BH), saline solution (BHS and BS, respectively), or both, aiming to point out the microscopic and molecular events assessed by Runt-related transcription factor 2 (RUNX 2), osteonectin (SPARC), and Bone Morphogenic Protein 4 (BMP4). The BH complex induced osteoprogenitor and osteoblastic differentiation of CAM mesenchymal cells, certified by the RUNX2 +, BMP4 +, and SPARC + phenotypes capable of bone matrix synthesis and mineralization. A strong angiogenic response without inflammation was detected on microscopic specimens of the BH combination compared with an inflammatory induced angiogenesis for the BS and BHS combinations. A multilayered organization of the BH complex grafted on CAM was detected with a differential expression of RUNX2, BMP4, and SPARC. The BH complex induced CAM mesenchymal cells differentiation through osteoblastic lineage with a sustained angiogenic response not related with inflammation. Thus, bone granules resuspended in hyaluronic acid seem to be the best combination for a proper non-inflammatory response in alveolar ridge augmentation. The CAM model allows us to assess the early events of the bone substitutes–mesenchymal cells interaction related to osteoblastic differentiation, an important step in alveolar ridge augmentation.

Retracted: Histologic evaluation of new bone in post-extraction sockets induced by melatonin and apigenin: an experimental study in American fox hound dogs

OBJECTIVE

The aim of this study was to evaluate the effect of topical applications of melatonin and apigenin (4',5,7-trihydroxyflavone) on new bone formation in post-extraction sockets after 30, 60 and 90 days.

MATERIALS AND METHODS

Six American fox hounds were used in the study, extracting mandibular premolars (P2, P3 and P4) and first molar (M1). Melatonin or apigenin impregnated in collagen sponges were applied at P3, P4 and M1 sites in both hemimandibles; P2 sites were used as control sites. Bone biopsies were taken at 30, 60 and 90 days and stained with hematoxylin-eosin.

RESULTS

At 30 days, a higher percentage of immature bone was observed in the control group (58.11 ± 1.76%) than in the apigenin (34.11 ± 1.02%) and melatonin groups (24.9 ± 0.14%) with significant differences between the three groups (P < 0.05). At 60 days, results were significantly better at melatonin sites (10.34 ± 1.09%) than apigenin (19.22 ± 0.35%) and control sites (36.7 ± 1.11%) (P < 0.05). At 90 days, immature bone percentages were similar for all groups. New bone formation was higher in melatonin group (79.56 ± 1.9%) than apigenin (68.89 ± 1.5%) and control group (58.87 ± 0.12%).

CONCLUSIONS

Topical applications of either melatonin or apigenin have a potential to accelerate bone tissue in early healing stages; melatonin was seen to have stimulated bone maturation to a greater extent at the 60 days of follow-up.

The multiple functions of melatonin in regenerative medicine

Melatonin research has been experiencing hyper growth in the last two decades; this relates to its numerous physiological functions including anti-inflammation, oncostasis, circadian and endocrine rhythm regulation, and its potent antioxidant activity. Recently, a large number of studies have focused on the role of melatonin in the regeneration of cells or tissues after their partial loss. In this review, we discuss the recent findings on the molecular involvement of melatonin in the regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others.

Daily melatonin administration improves osseointegration in pinealectomized rats

The hypothesis of this study was that the peri-implant bone healing of the group of pinealectomized rats would differ from the control group. The samples were subjected to immunohistochemical, microtomographic (total porosity and connectivity density), and fluorochrome (mineralized surface) analyses.

Prophylactic supplement with melatonin successfully suppresses the pathogenesis of periodontitis through normalizing RANKL/OPG ratio and depressing the TLR4/MyD88 signaling pathway

Periodontitis (PD) is an inflammatory disease characterized by gingival inflammation and resorption of alveolar bone. Impaired receptor activator of nuclear factor-kappa B ligand/osteoprotegerin (RANKL/OPG) signaling caused by enhanced production of pro-inflammatory cytokines plays an essential role in the pathogenesis of PD. Considering melatonin possesses significant anti-inflammatory property, this study aimed to determine whether prophylactic treatment with melatonin would effectively normalize RANKL/OPG signaling, depress toll-like receptor 4/myeloid differentiation factor 88 (TLR4/MyD88)-mediated pro-inflammatory cytokine activation, and successfully suppress the pathogenesis of PD. PD was induced in adult rats by placing the ligature at molar subgingival regions. Fourteen days before PD induction, 10, 50, or 100 mg/kg of melatonin was intraperitoneally injected for consecutive 28 days. Biochemical and enzyme-linked immunosorbent assay were used to detect TLR4/MyD88 activity, RANKL, OPG, interleukin 1β, interleukin 6, and tumor necrosis factor-α levels, respectively. The extent of bone loss, bone mineral intensity, and calcium intensity was further evaluated by scanning electron microscopy, micro-computed tomography, and energy-dispersive X-ray spectroscopy. Results indicated that high RANKL/OPG ratio, TLR4/MyD88 activity, and pro-inflammatory cytokine levels were detected following PD. Impaired biochemical findings paralleled well with severe bone loss and reduced calcium intensity. However, in rats pretreated with melatonin, all above parameters were successfully returned to nearly normal levels with maximal change observed in rats receiving 100 mg/kg. As prophylactic treatment with melatonin effectively normalizes RANKL/OPG signaling by depressing TLR4/MyD88-mediated pro-inflammatory cytokine production, dietary supplement with melatonin may serve as an advanced strategy to strengthen oral health to counteract PD-induced destructive damage.

One-pot preparation of polymer microspheres with different porous structures to sequentially release bio-molecules for cutaneous regeneration

Herein, we reveal a double emulsion method combining the sol–gel method to prepare poly(lactic-co-glycolic acid) microspheres with different porous structures for sequential release of two types of biomolecules.

Melatonin: A Review of Its Potential Functions and Effects on Dental Diseases

Melatonin is a hormone synthesised and secreted by the pineal gland and other organs. Its secretion, controlled by an endogenous circadian cycle, has been proven to exert immunological, anti-oxidant, and anti-inflammatory effects that can be beneficial in the treatment of certain dental diseases. This article is aimed at carrying out a review of the literature published about the use of melatonin in the dental field and summarising its potential effects. In this review article, an extensive search in different databases of scientific journals was performed with the objective of summarising all of the information published on melatonin use in dental diseases, focussing on periodontal diseases and dental implantology. Melatonin released in a natural way into the saliva, or added as an external treatment, may have important implications for dental disorders, such as periodontal disease, as well as in the osseointegration of dental implants, due to its anti-inflammatory and osseoconductive effects. Melatonin has demonstrated to have beneficial effects on dental pathologies, although further research is needed to understand the exact mechanisms of this molecule.

Outcomes of topical applications of melatonin in implant dentistry: a systematic review

BACKGROUND

Due to its antioxidant properties and its ability to detoxify free radicals, melatonin may interfere in the function of osteoclasts and thereby inhibit bone resorption. This inhibition of bone resorption may be enhanced by a reaction of indolamine in osteoclastogenesis and this may contribute to certain benefits in implantology.

OBJECTIVE

This systematic literature review on the use of melatonin in implant dentistry aims to provide guidelines for clinicians.

MATERIALS AND METHODS

PubMed, Science Direct, ISI Web of Knowledge, and the Cochrane base databases were used to identify articles published between 1999 and 2013 on melatonin use in implant dentistry. Ten articles were selected consisting of 9 animal research studies and 1 review article, involving 60 Beagle dogs, 57 rats, and 30 rabbits and a total of 352 implants.

RESULTS

Melatonin, which is released into the saliva, has important implications in the oral cavity. To achieve dental implant stability, osseointegration involves a cascade of protein and cell apposition, vascular invasion, bone formation, and maturation. This process may be accelerated by local delivery of growth-promoting factors, as occurs with the topical application of melatonin over the implant surface.

CONCLUSIONS

The experimental evidence suggests that topical applications of melatonin may be useful in oral surgery and implant dentistry, increasing bone-to-implant contact values and new bone formation, and so improving the success and long-term survival of implant treatments.

Biomaterial-mediated strategies targeting vascularization for bone repair

Repair of non-healing bone defects through tissue engineering strategies remains a challenging feat in the clinic due to the aversive microenvironment surrounding the injured tissue. The vascular damage that occurs following a bone injury causes extreme ischemia and a loss of circulating cells that contribute to regeneration. Tissue-engineered constructs aimed at regenerating the injured bone suffer from complications based on the slow progression of endogenous vascular repair and often fail at bridging the bone defect. To that end, various strategies have been explored to increase blood vessel regeneration within defects to facilitate both tissue-engineered and natural repair processes. Developments that induce robust vascularization will need to consolidate various parameters including optimization of embedded therapeutics, scaffold characteristics, and successful integration between the construct and the biological tissue. This review provides an overview of current strategies as well as new developments in engineering biomaterials to induce reparation of a functional vascular supply in the context of bone repair.

Purmorphamine increased adhesion, proliferation and expression of osteoblast phenotype markers of human dental pulp stem cells cultured on beta-tricalcium phosphate

OBJECTIVES

Growth factors play a significant role in cell proliferation and differentiation during different stages of the bone repair. However, several limitations have been brought researchers attention to an osteoinductive small molecule including Purmorphamine. In this study, we aimed to evaluate the effect of Purmorphamine on adhesion, proliferation and differentiation of human dental pulp stem cells (hDPSCs) seaded on beta-tricalcium phosphate (β-TCP) granules.

METHODS

hDPSCs were established from extracted wisdom teeth of healthy volenteers. Cells at passage 3 were seeded on β-TCP in the presence or absence of Purmorphamine. Cell adhesion and proliferation were assessed using scanning electeron microscopy (SEM) and DNA counting assay, respectively, after 1, 3 and 5days. Then, hDPSCs seeded on β-TCP were subjected to osteogenic medium with or without Purmorphamine. After 7 and 14days osteogenic diffrentiation capability of hDPSCs were determined using real-time RT-PCR and alkaline phosphatase (ALP) activity assay.

RESULTS

The significant increase in amount of DNA was observed at day 3 and 5 in the presence of Purmorphamine. SEM imaging also was confirmed the DNA counting assay; in all given time points, hDPSC attachment and growth was significantly higher in the presence of Purmorphamine. ALP activity was increased by Purmorphamine at both 7 and 14days of induction. Purmorphamine showed to effect on osteopontin expression at earlier stage of osteogenic differentiation, whereas for osteocalcin expression, this effect was more evident at later stage of differentiation.

CONCLUSION

Purmorphamine had a promotive effect on adhesion, proliferation and osteogenic differentiation of hDPSCs cultured on β-TCP. The outcome of the current study would help in development of in vitro culture conditions for better osteogenic differentiation of hDPSCs prior to transplantation.

A new role for 5-methoxytryptophol on bone cells function in vitro

The present study investigates the direct action of 5-methoxytryptophol (5-MTX) in both MC3T3-E1 and RAW264.7 cells and compares it with melatonin (MEL), another 5-methoxyindol known to play a significant role on bone metabolism. We first screened increasing doses of both 5-MTX and MEL to determine their effect on metabolic activity and viability of preosteoblastic MC3T3-E1 cells. The optimal dose was used to determine its effect on differentiation of MC3T3-E1 cells and preosteoclastic RAW264.7 cells. Finally, we investigated the mechanism of action by adding the melatonin receptor antagonist luzindole (LUZ) and detecting the immunostaining of phospho-ERK. In MC3T3-E1 cells, most of the 5-MTX doses reduced slightly the metabolic activity of osteoblasts compared with the control, while MEL only decreased it for the highest dose (2.5 mM). As regards to cytotoxicity, low doses (0.001-0.1 mM) of both indoles showed a protective effect on osteoblasts, while the highest dose of MEL showed a higher cytotoxicity than the 5-MTX one. After 14 days of cell culture, Rankl mRNA levels were decreased, especially for 5-MTX. 5-MTX also induced a higher osteocalcin secretion and mineralization capacity than MEL. In RAW264.7 cells, 5-MTX decreased the number of osteoclast formed and its activity whereas MEL did not affect significantly the number of multinucleated TRAP-positive cells formed and showed a lower activity. Finally, MEL and 5-MTX promoted activation of the ERK1/2 pathway through the phosphorylation of ERK, while LUZ addition suppressed this effect. In conclusion, the present study demonstrates a new role of 5-MTX inhibiting osteoclastogenesis and promoting osteoblast differentiation.

Melatonin facilitates adipose-derived mesenchymal stem cells to repair the murine infarcted heart via the SIRT1 signaling pathway

Mesenchymal stem cells (MSCs)-based therapy provides a promising therapy for the ischemic heart disease (IHD). However, engrafted MSCs are subjected to acute cell death in the ischemic microenvironment, characterized by excessive inflammation and oxidative stress in the host's infarcted myocardium. Melatonin, an indole, which is produced by many organs including pineal gland, has been shown to protect bone marrow MSCs against apoptosis although the mechanism of action remains elusive. Using a murine model of myocardial infarction (MI), this study was designed to evaluate the impact of melatonin on adipose-derived mesenchymal stem cells (AD-MSCs)-based therapy for MI and the underlying mechanism involved with a focus on silent information regulator 1(SIRT1) signaling. Our results demonstrated that melatonin promoted functional survival of AD-MSCs in infarcted heart and provoked a synergetic effect with AD-MSCs to restore heart function. This in vivo effect of melatonin was associated with alleviated inflammation, apoptosis, and oxidative stress in infarcted heart. In vitro studies revealed that melatonin exert cytoprotective effects on AD-MSCs against hypoxia/serum deprivation (H/SD) injury via attenuating inflammation, apoptosis, and oxidative stress. Mechanistically, melatonin enhanced SIRT1 signaling, which was accompanied with the increased expression of anti-apoptotic protein Bcl2, and decreased the expression of Ac-FoxO1, Ac-p53, Ac-NF-ΚB, and Bax. Taken together, our findings indicated that melatonin facilitated AD-MSCs-based therapy in MI, possibly through promoting survival of AD-MSCs via SIRT1 signaling. Our data support the promise of melatonin as a novel strategy to improve MSC-based therapy for IHD, possibly through SIRT1 signaling evocation.

Osseoinductive elements around immediate implants for better osteointegration: a pilot study in foxhound dogs

OBJECTIVE

The aim of this study was to evaluate the effects on osseointegration of topical applications of melatonin vs. vitamin D over surfaces of immediate implants.

MATERIALS AND METHODS

Mandibular premolar distal roots (P₂ , P₃ , P₄ ) were extracted bilaterally from six American Foxhound dogs. Three conical immediate implants were randomly placed bilaterally in each mandible. Three randomized groups were created: melatonin 5% test group (MI), vitamin D 10% test group (DI), and Control group implants (CI). Block sections were obtained after 12 weeks and processed for mineralized ground sectioning. Bone-to-implant contact (total BIC), new bone formation (NBF), inter-thread bone (ITB), and histological linear measurements (HLM) were assessed.

RESULTS

At 12 weeks, all implants were clinically stable and histologically osseointegrated. Total BIC values were 49.20 ± 3.26 for the MI group, 49.86 ± 1.89 for DI group and 45.78 ± 4.21 for the CI group (P < 0.018) with statistically significant difference between the three groups. BIC percentage were 42.44 ± 2.18 for MI, 44.56 ± 1.08 for DI, and 41.95 ± 3.34 for CI groups respectively (P > 0.05). Inter-thread bone formation values were MI 17.56 ± 2.01, for DI 19.87 ± 0.92, and CI 14.56 ± 1.24 (P > 0.05). Statistically significant differences in peri-implant new bone formation were found between the three groups: MI 28.76 ± 1.98, DI 32.56 ± 1.11 and CI 25.43 ± 4.67, respectively (P < 0.045). Linear measurements showed that the MI group showed significantly less lingual crestal bone loss (CBL) (MI 0.59 ± 0.71), compared to DI (0.91 ± 1.21) and CI (0.93 ± 1.21) (P < 0.042), and less lingual peri-implant mucosa (PIM) (MI 3.11 ± 1.34),(DI 3.25 ± 0.18 compared with CI 3.54 ± 1.81 (P = 0.429). Linear measurements of buccal CBL showed significantly less buccal bone loss in test DI (0.36 ± 0.12) than CI (1.34 ± 1.23) and MI (1.11 ± 1.38) (P = 0.078).

CONCLUSIONS

Within the limitations of this animal study, topical applications of 5% Melatonin or 10% vitamin D improved bone formation around implants placed immediately after extraction and helped to reduce CBL after 12 weeks osseointegration.

Melatonin enhances vertical bone augmentation in rat calvaria secluded spaces

BACKGROUND

Melatonin has many roles, including bone remodeling and osseointegration of dental implants. The topical application of melatonin facilitated bone regeneration in bone defects. We evaluated the effects of topical application of melatonin on vertical bone augmentation in rat calvaria secluded spaces.

MATERIAL AND METHODS

In total, 12 male Fischer rats were used and two plastic caps were fixed in the calvarium. One plastic cap was filled with melatonin powder and the other was left empty.

RESULTS

Newly generated bone at bone defects and within the plastic caps was evaluated using micro-CT and histological sections. New bone regeneration within the plastic cap was increased significantly in the melatonin versus the control group.

CONCLUSIONS

Melatonin promoted vertical bone regeneration in rat calvaria in the secluded space within the plastic cap.

Melatonin in functionalized biomimetic constructs promotes rapid tissue regeneration in Wistar albino rats

Biomimetic collagen–poly(dialdehyde) gum acacia based hybrid scaffolds with a synergistic combination of melatonin were prepared to regenerate tissue formation in wound-healing applications.

Therapeutic Effects of Melatonin on Alveolar Bone Resorption After Experimental Periodontitis in Rats: A Biochemical and Immunohistochemical Study

BACKGROUND

The present study aims to investigate the effects of systemic melatonin administration on alveolar bone resorption in experimental periodontitis in rats.

METHODS

Twenty-four male Sprague-Dawley rats were divided into three groups (control, experimental periodontitis [Ped], and experimental periodontitis treated with melatonin [Mel-Ped]). For periodontitis induction, first molars were ligatured submarginally for 4 weeks. After ligature removal, rats in the Mel-Ped group were treated with a daily single dose of 10 mg/kg body weight melatonin for 15 consecutive days. At the end of the study, intracardiac blood samples and mandible tissues were obtained for histologic, biochemical, and radiographic analysis. Serum markers related to bone turnover, calcium, phosphorus, bone alkaline phosphatase (b-ALP), and terminal C telopeptide of collagen Type I (CTX) were analyzed. Myeloperoxidase levels were determined in gingival tissue homogenates, and receptor activator of nuclear factor-kappa B ligand (RANKL) activation was analyzed in the mandible samples stereologically. Alveolar bone loss was also evaluated radiographically in the mandible samples of each group.

RESULTS

Melatonin treatment decreased serum CTX levels and increased b-ALP levels. Serum calcium and phosphorus levels were not statistically different among groups (P >0.05). Alveolar bone resorption and myeloperoxidase activity were statistically higher in the Ped group compared to the Mel-Ped group (P <0.05). Immunohistochemical staining of RANKL and osteoclast activity were significantly lower in the Mel-Ped group compared to the Ped group (P <0.05).

CONCLUSION

This study reveals that melatonin treatment significantly inhibits regional alveolar bone resorption and contributes to periodontal healing in an experimental periodontitis rat model.

Circadian System and Melatonin Hormone: Risk Factors for Complications during Pregnancy

Pregnancy is a complex and well-regulated temporal event in which several steps are finely orchestrated including implantation, decidualization, placentation, and partum and any temporary alteration has serious effects on fetal and maternal health. Interestingly, alterations of circadian rhythms (i.e., shiftwork) have been correlated with increased risk of preterm delivery, intrauterine growth restriction, and preeclampsia. In the last few years evidence is accumulating that the placenta may have a functional circadian system and express the clock genes Bmal1, Per1-2, and Clock. On the other hand, there is evidence that the human placenta synthesizes melatonin, hormone involved in the regulation of the circadian system in other tissues. Moreover, is unknown the role of this local production of melatonin and whether this production have a circadian pattern. Available information indicates that melatonin induces in placenta the expression of antioxidant enzymes catalase and superoxide dismutase, prevents the injury produced by oxidative stress, and inhibits the expression of vascular endothelial growth factor (VEGF) a gene that in other tissues is controlled by clock genes. In this review we aim to analyze available information regarding clock genes and clock genes controlled genes such as VEGF and the possible role of melatonin synthesis in the placenta.

Upregulation of miRNA3195 and miRNA374b Mediates the Anti-Angiogenic Properties of Melatonin in Hypoxic PC-3 Prostate Cancer Cells

Recently microRNAs (miRNAs) have been attractive targets with their key roles in biological regulation through post-transcription to control mRNA stability and protein translation. Though melatonin was known as an anti-angiogenic agent, the underlying mechanism of melatonin in PC-3 prostate cancer cells under hypoxia still remains unclear. Thus, in the current study, we elucidated the important roles of miRNAs in melatonin-induced anti-angiogenic activity in hypoxic PC-3 cells. miRNA array revealed that 33 miRNAs (>2 folds) including miRNA3195 and miRNA 374b were significantly upregulated and 16 miRNAs were downregulated in melatonin-treated PC-3 cells under hypoxia compared to untreated control. Melatonin significantly attenuated the expression of hypoxia-inducible factor (HIF)-1 alpha, HIF-2 alpha and vascular endothelial growth factor (VEGF) at mRNA level in hypoxic PC-3 cells. Consistently, melatonin enhanced the expression of miRNA3195 and miRNA 374b in hypoxic PC-3 cells by qRT-PCR analysis. Of note, overexpression of miRNA3195 and miRNA374b mimics attenuated the mRNA levels of angiogenesis related genes such as HIF-1alpha, HIF-2 alpha and VEGF in PC-3 cells under hypoxia. Furthermore, overexpression of miRNA3195 and miRNA374b suppressed typical angiogenic protein VEGF at the protein level and VEGF production induced by melatonin, while antisense oligonucleotides against miRNA 3195 or miRNA 374b did not affect VEGF production induced by melatonin. Also, overexpression of miR3195 or miR374b reduced HIF-1 alpha immunofluorescent expression in hypoxic PC-3 compared to untreated control. Overall, our findings suggest that upregulation of miRNA3195 and miRNA374b mediates anti-angiogenic property induced by melatonin in hypoxic PC-3 cells.

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.

Extracellular matrix modulates the biological effects of melatonin in mesenchymal stem cells

Both self-renewal and lineage-specific differentiation of mesenchymal stem cells (MSCs) are triggered by their in vivo microenvironment including the extracellular matrix (ECM) and secreted hormones. The ECM may modulate the physiological functions of hormones by providing binding sites and by regulating downstream signaling pathways. Thus, the purpose of this study was to evaluate the degree of adsorption of melatonin to a natural cell-deposited ECM and the effects of this interaction on the biological functions of melatonin in human bone marrow-derived MSCs (BM-MSCs). The fibrillar microstructure, matrix composition, and melatonin-binding affinity of decellularized ECM were characterized. The cell-deposited ECM improved melatonin-mediated cell proliferation by 31.4%, attenuated accumulation of intracellular reactive oxygen species accumulation, and increased superoxide dismutase (SOD) mRNA and protein expression. Interaction with ECM significantly enhanced the osteogenic effects of melatonin on BM-MSCs by increasing calcium deposition by 30.5%, up-regulating osteoblast-specific gene expression and down-regulating matrix metalloproteinase (MMP) expression. The underlying mechanisms of these changes in expression may involve intracellular antioxidant enzymes, because osteoblast-specific genes were down-regulated, whereas MMP expression was up-regulated, in the presence of SOD-specific inhibitors. Collectively, our findings indicate the importance of native ECM in modulating the osteoinductive and antioxidant effects of melatonin and provide a novel platform for studying the biological actions of growth factors or hormones in a physiologically relevant microenvironment. Moreover, a better understanding of the enhancement of MSC growth and osteogenic differentiation resulting from the combination of ECM and melatonin could improve the design of graft substitutes for skeletal tissue engineering.