Bipedal ambulation induces experimental scoliosis in C57BL/6J mice with reduced plasma and pineal melatonin levels

Zebrafish: an important model for understanding scoliosis

Scoliosis is a common spinal deformity that considerably affects the physical and psychological health of patients. Studies have shown that genetic factors play an important role in scoliosis. However, its etiopathogenesis remain unclear, partially because of the genetic heterogeneity of scoliosis and the lack of appropriate model systems. Recently, the development of efficient gene editing methods and high-throughput sequencing technology has made it possible to explore the underlying pathological mechanisms of scoliosis. Owing to their susceptibility for developing scoliosis and high genetic homology with human, zebrafish are increasingly being used as a model for scoliosis in developmental biology, genetics, and clinical medicine. Here, we summarize the recent advances in scoliosis research on zebrafish and discuss the prospects of using zebrafish as a scoliosis model.

Effect of Melatonin on the Expression of LYVE-1 Receptor in Liver Sinusoidal Endothelial Cells of Mice with the Light-Induced Functional Pinealectomy Model

Intragastric administration of melatonin in physiological doses (1 mg/kg body weight) for 14 days to C57BL/6 mice with light-induced functional pinealectomy model (24-h lighting for 14 days) results in an increase in the LYVE-1 expression area by 2.4 times and a significant increase in receptor concentration (1.6% decrease in staining brightness) in liver sinusoidal endothelial cells in comparison with animals kept under continuous lighting and not treated with the hormone, which indicates the formation of stability of the endothelial barrier in the organ. Melatonin treatment also enhanced lymphatic drainage in all it links (including interstitial non-vascular pathways and lymphatic vessels) and improved structural and functional parameters of blood circulation and lymph flow in the organ, which created conditions for reducing metabolic load on structural elements of the liver.

Melatonin effects on bone: Implications for use as a therapy for managing bone loss

Melatonin is the primary circadian output signal from the brain and is mainly synthesized in pinealocytes. The rhythm and secretion of melatonin are under the control of an endogenous oscillator located in the SCN or the master biological clock. Disruptions in circadian rhythms by shift work, aging, or light at night are associated with bone loss and increased fracture risk. Restoration of nocturnal melatonin peaks to normal levels or therapeutic levels through timed melatonin supplementation has been demonstrated to provide bone-protective actions in various models. Melatonin is a unique molecule with diverse molecular actions targeting melatonin receptors located on the plasma membrane or mitochondria or acting independently of receptors through its actions as an antioxidant or free radical scavenger to stimulate osteoblastogenesis, inhibit osteoclastogenesis, and improve bone density. Its additional actions on entraining circadian rhythms and improving quality of life in an aging population coupled with its safety profile make it an ideal therapeutic candidate for protecting against bone loss in susceptible populations. The intent of this review is to provide a focused discussion on bone loss and disorders of the bone as it relates to melatonin and conditions that modify melatonin levels with the hope that future therapies include those that include melatonin and correct those factors that modify melatonin levels like circadian disruption.

Etiopathogenesis of adolescent idiopathic scoliosis: Review of the literature and new epigenetic hypothesis on altered neural crest cells migration in early embryogenesis as the key event

Adolescent idiopathic scoliosis (AIS) affects 2-3% of children. Numerous hypotheses on etiologic/causal factors of AIS were investigated, but all failed to identify therapeutic targets and hence failed to offer a cure. Therefore, currently there are only two options to minimize morbidity of the patients suffering AIS: bracing and spinal surgery. From the beginning of 1960th, spinal surgery, both fusion and rod placement, became the standard of management for progressive adolescent idiopathic spine deformity. However, spinal surgery is often associated with complications. These circumstances motivate AIS scientific community to continue the search for new etiologic and causal factors of AIS. While the role of the genetic factors in AIS pathogenesis was investigated intensively and universally recognized, these studies failed to nominate mutation of a particular gene or genes combination responsible for AIS development. More recently epigenetic factors were suggested to play causal role in AIS pathogenesis. Sharing this new approach, we investigated scoliotic vertebral growth plates removed during vertebral fusion (anterior surgery) for AIS correction. In recent publications we showed that cells from the convex side of human scoliotic deformities undergo normal chondrogenic/osteogenic differentiation, while cells from the concave side acquire a neuronal phenotype. Based on these facts we hypothesized that altered neural crest cell migration in early embryogenesis can be the etiological factor of AIS. In particular, we suggested that neural crest cells failed to migrate through the anterior half of somites and became deposited in sclerotome, which in turn produced chondrogenic/osteogenic-insufficient vertebral growth plates. To test this hypothesis we conducted experiments on chicken embryos with arrest neural crest cell migration by inhibiting expression of Paired-box 3 (Pax3) gene, a known enhancer and promoter of neural crest cells migration and differentiation. The results showed that chicken embryos treated with Pax3 siRNA (microinjection into the neural tube, 44 h post-fertilization) progressively developed scoliotic deformity during maturation. Therefore, this analysis suggests that although adolescent idiopathic scoliosis manifests in children around puberty, the real onset of the disease is of epigenetic nature and takes place in early embryogenesis and involves altered neural crest cells migration. If these results confirmed and further elaborated, the hypothesis may shed new light on the etiology and pathogenesis of AIS.

Measuring melatonin by immunoassay

The pineal gland hormone melatonin continues to be of considerable interest to biomedical researchers. Of particular interest is the pattern of secretion of melatonin in relation to sleep timing as well as its potential role in certain diseases. Measuring melatonin in biological fluids such as blood and saliva presents particular methodological challenges since the production and secretion of the hormone are known to be extremely low during the light phase in almost all situations. Active secretion only occurs around the time of lights out in a wide range of species. The challenge then is to develop practical high-throughput assays that are sufficiently sensitive and accurate enough to detect levels of melatonin less than 1 pg/mL in biological fluids. Mass spectrometry assays have been developed that achieve the required sensitivity, but are really not practical or even widely available to most researchers. Melatonin radioimmunoassays and ELISA have been developed and are commercially available. But the quality of the results that are being published is very variable, partly not only because of poor experimental designs, but also because of poor assays. In this review, I discuss issues around the design of studies involving melatonin measurement. I then provide a critical assessment of 21 immunoassay kits marketed by 11 different companies with respect to validation, specificity and sensitivity. Technical managers of the companies were contacted in an attempt to obtain information not available online or in kit inserts. A search of the literature was also conducted to uncover papers that have reported the use of these assays, and where possible, both daytime and night-time plasma or saliva melatonin concentrations were extracted and tabulated. The results of the evaluations are disturbing, with many kits lacking any validation studies or using inadequate validation methods. Few assays have been properly assessed for specificity, while others report cross-reaction profiles that can be expected to result in over estimation of the melatonin levels. Some assays are not fit for purpose because they are not sensitive enough to determine plasma or saliva DLMO of 10 and 3 pg/mL, respectively. Finally, some assays produce unrealistically high daytime melatonin levels in humans and laboratory animals in the order of hundreds of pg/mL. In summary, this review provides a comprehensive and unique assessment of the current commercial melatonin immunoassays and their use in publications. It provides researchers new to the field with the information they need to design valid melatonin studies from both the perspective of experimental/clinical trial design and the best assay methodologies. It will also hopefully help journal editors and reviewers who may not be fully aware of the pitfalls of melatonin measurement make better informed decisions on publication acceptability.

Effects of Melatonin on the Body Composition, Physical Performance, and Blood Erythrocyte Indexes of C57Bl/6J Mice Exposed to Continuous Illumination

Male C57Bl/6J mice were exposed to daily 24-h illumination over 14 days and daily intragastrically received melatonin (1 mg/kg) or water (placebo). Controls were kept under standard day/night (14/10 h) conditions. Melatonin prevented the development of anemia in mice exposed to continuous illumination, which was proven by higher blood hemoglobin levels by the end of the experiment in melatonin-treated animals in comparison with the placebo group. Studies by the low-field NMR spectrometry detected lower lean body mass, total body water, and especially, fat content (by ~13%) in animals receiving placebo. Melatonin treatment led to an increase in the lean body mass and total body water on day 7 (in comparison with the placebo group) without affecting fat mass. On day 14 of continuous illumination, lean body mass increased in comparison with the corresponding parameter in the control and placebo groups. Melatonin had no effect on the physical endurance of mice exposed to continuous illumination (assessed by the grid hanging test).

SPRY4 is responsible for pathogenesis of adolescent idiopathic scoliosis by contributing to osteogenic differentiation and melatonin response of bone marrow-derived mesenchymal stem cells

Adolescent idiopathic scoliosis (AIS) is a complex, three-dimensional deformity of the spine that commonly occurs in pubescent girls. Decreased osteogenic differentiation and aberrant melatonin signalling have been demonstrated in mesenchymal stem cells (MSCs) from AIS patients and are implicated in the pathogenesis of AIS. However, the molecular mechanisms underlying these abnormal cellular features remain largely unknown. Our previous work comparing gene expression profiles between MSCs from AIS patients and healthy controls identified 1027 differentially expressed genes. In the present study, we focused on one of the most downregulated genes, SPRY4, in the MAPK signalling pathway and examined its role in osteogenic differentiation. We found that SPRY4 is markedly downregulated in AIS MSCs. Knockdown of SPRY4 impaired differentiation of healthy MSCs to osteoblasts, while SPRY4 overexpression in AIS MSCs enhanced osteogenic differentiation. Furthermore, melatonin treatment boosted osteogenic differentiation, whereas SPRY4 ablation ablated the promotional effects of melatonin. Moreover, SPRY4 was upregulated by melatonin exposure and contributed to osteogenic differentiation and melatonin response in a MEK-ERK1/2 dependent manner. Thus, loss of SPRY4 in bone marrow derived-MSCs results in reduced osteogenic differentiation, and these defects are further aggravated under the influence of melatonin. Our findings provide new insights for understanding the role of melatonin in AIS aetiology and highlight the importance of MSCs in AIS pathogenesis.

The effect of exogenous melatonin on reducing scoliotic curvature and improving bone quality in melatonin-deficient C57BL/6J mice

It is well-documented that melatonin deficiency has been linked to the etiopathogenesis of adolescent idiopathic scoliosis. In this study, we intended to apply melatonin in melatonin-deficient mice to ascertain whether melatonin could reduce the incidence/severity of scoliosis, and investigate the role of melatonin on bone mineral density in scoliosis. A total of 80 mice were divided into 4 groups: 20 quadrupedal mice and 20 bipedal mice served as controls; 20 quadrupedal and 20 bipedal mice received oral melatonin (8 mg/kg BW) daily. After 5^th, 10^th, 15^th and 20^th weeks of treatment, radiographs and in vivo micro-CT were used to determine the incidence of scoliosis and bone qualities, respectively. Upon sacrifice, the levels of melatonin were measured in each group. At 20^th week, the occurrence of scoliosis was 80%, 30%, 22% and 5% in bipedal, quadrupedal, bipedal + melatonin and quadrupedal + melatonin group, respectively. The trabecular bone quality of the vertebral body was significantly ameliorated in the melatonin-treated bipedal models. Likewise, the number of osteoclasts was significantly less in those treated with melatonin. Our results indicated that melatonin deficiency may be crucial for scoliotic development, and restoration of melatonin levels can prevent scoliotic development with the improvement in bone density.

Melatonin, adolescence, and the brain: An insight into the period-specific influences of a multifunctional signaling molecule

Melatonin is a neurohormone that is involved in the modulation of a wide range of physiological processes, including maintenance of the circadian rhythm, mediation of photoperiodic information, regulation of the sleep-wake cycle, synchronization of cell physiology, antioxidant defense, and immune-modulation. Although there are reports of increasing use of melatonin in the management of a number of health conditions, evidence exists that is suggestive of deleterious effects of melatonin administration on brain and reproductive development in the prepubertal and pubertal periods that are within the teenage years. In this review, we examine the influences of endogenous and exogenous melatonin on the adolescent brain, with specific reference to its involvement in the evolution of brain functions, brain structure, sleep regulation, and modulation of behaviors in health or disease.

Preclinical models for orthopedic research and bone tissue engineering

In this review, we broadly define and discuss the preclinical rodent models that are used for orthopedics and bone tissue engineering. These range from implantation models typically used for biocompatibility testing and high-throughput drug screening, through to fracture and critical defect models used to model bone healing and severe orthopedic injuries. As well as highlighting the key methods papers describing these techniques, we provide additional commentary based on our substantive practical experience with animal surgery and in vivo experimental design. This review also briefly touches upon the descriptive and functional outcome measures and power calculations that are necessary for an informative study. Obtaining informative and relevant research outcomes can be very dependent on the model used, and we hope this evaluation of common models will serve as a primer for new researchers looking to undertake preclinical bone studies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:832-840, 2018.

The value of applying a melatonin antagonist (Luzindole) in improving the success rate of the bipedal rat scoliosis model

BACKGROUND

An ideal animal model has always been the key to research the pathogenesis and treatment of adolescent idiopathic scoliosis (AIS), while available methods have obvious disadvantages. The deficiency of melatonin has been proved relating to AIS. In this research, we intended to apply Luzindole, the melatonin antagonist, in bipedal rat model, for the block of combination of melatonin and its receptor, to inhibit the melatonin effect, and then to understand whether this method can effectively improve the scoliosis rate of bipedal rat model, and investigate the role of melatonin in scoliosis. To investigate the feasibility of improving the success rate of bipedal rat scoliosis model via intraperitoneal injection of melatonin antagonist (Luzindole).

METHODS

A total of 60 3-weeks-old Sprague-Dawley rats were included in this study, and were divided into 3 groups (A, B and C). Each group included 20 rats. Osteotomy of the bilateral proximal humerus and proximal tailbone was performed in group A and group B; intraperitoneal injection of Luzindole (0.2 mg/kg) was performed in group A and group C. X-rays were taken before the surgery, 1 month after the surgery, 3 months after the surgery, and 6 months after the surgery, to calculate the Cobb's angle of the spine (>10° was considered scoliosis). The weight of every rat was also measured at the same time. Rats were euthanized 6 months after surgery to determine the calmodulin level in thrombocytes.

RESULTS

The rate of scoliosis in group A (14/20) was significantly higher than those in group B (6/20) and group C (0/20) (P < 0.05). The differences in the weights of the 3 groups were non-significant; as were differences in the calmodulin level in thrombocytes.

CONCLUSION

The application of the melatonin antagonist of Luzindole can improve the success rate of the bipedal rat scoliosis model. Meanwhile, this study indicates that a decreased melatonin level is not the primary cause of scoliosis, but that it may increase the likelihood and severity of scoliosis.

Role of Enhanced Central Leptin Activity in a Scoliosis Model Created in Bipedal Amputated Mice

STUDY DESIGN

An experimental study to investigate the role of enhanced central leptin activity in a bipedal mouse scoliosis model.

OBJECTIVE

To investigate the influence of enhanced central leptin activity on the development of scoliosis in mice, and to support Burwell's hypothesis that central leptin dysfunction is involved in the etiopathogenesis of idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Significantly lower level of circulating leptin and higher level of soluble leptin receptor have been reported in adolescent idiopathic scoliosis compared with healthy adolescents, suggesting possible association between abnormal central leptin level and dysfunction.

METHODS

Amputation of forelimbs and tail was performed on 50 male C3H/HeJ mice at the age of 3 weeks. Then, the mice were randomly divided into 2 groups: Group A consisted of 25 mice treated with injection into the hypothalamus with lentivirus vectors that overexpressed leptin; and Group B involved the remaining 25 mice receiving intracerebral injection with the control vectors. Radiographs were obtained at 20th week to determine the presence of spinal deformity. The incidence of scoliosis and curve magnitude were compared between groups.

RESULTS

The body weight was initially found to be slightly lower in mice of Group A when compared with Group B. Significantly higher peripheral serum leptin level was found in leptin-overexpressing mice than control mice. Scoliosis developed in 23 mice of Group A (92%), with an average Cobb angle of 30.2°, and in 13 of Group B (52%), with an average Cobb angle of 18.4°, respectively. A higher incidence (P = 0.002) and more severe curve (P <0.001) were observed in Group A.

CONCLUSION

In this bipedal mouse scoliosis model, enhanced central leptin activity might not only increase the risk of developing a scoliosis, but also contribute to the progression of scoliosis.

LEVEL OF EVIDENCE

N/A.

Does elevated osteopontin level play an important role in the development of scoliosis in bipedal mice?

BACKGROUND CONTEXT

Previous studies implied indirectly that an elevated osteopontin (OPN) level might play a key role in the pathomechanism of adolescent idiopathic scoliosis. Nonetheless, up to now, no direct evidence was proposed to determine this issue.

PURPOSE

The aim was to determine the role of OPN in the pathomechanism of scoliosis.

STUDY DESIGN

This was an experimental study to investigate the role of OPN in a bipedal mouse scoliosis model.

METHODS

All procedures were performed under the approval and supervision of the Institutional Animal Care and Use Committee of our university. A new bipedal mouse model with elevated OPN level was established in this study. Amputation of forelimbs and tail was performed on 80 male C3H/HeJ mice at the age of 3 weeks. Then, these mice were randomly divided into two groups: Group A consisted of 40 mice treated with OPN 40 mg/kg daily and Group B consisted of the remaining 40 mice treated with saline. Then, 40 quadruped mice with saline were included in Group C. Body length, X-rays, and computed tomographic scans were obtained at the twentieth week. Then, scoliosis incidence, curve magnitude, and circulating OPN level were compared among groups.

RESULTS

Osteopontin level was significantly higher in Group A compared with that in Groups B and C. Spine deformity was identified in 37 mice in Group A, 21 mice in Group B, and 5 mice in Group C. The average Cobb angle was 29.8° in Group A, 20.9° in Group B, and 17.5° in Group C. Although no significant difference of body length was found, significant statistical difference was noted in terms of scoliosis incidence and curve magnitude, among the three groups.

CONCLUSIONS

The results of the present study indicated that the elevated OPN level might play an important role in the etiopathogenesis of scoliosis, that is, it not only raises the risk for scoliosis in bipedal mice but also contributes to curve progression.

A review of pinealectomy-induced melatonin-deficient animal models for the study of etiopathogenesis of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a common orthopedic disorder of unknown etiology and pathogenesis. Melatonin and melatonin pathway dysfunction has been widely suspected to play an important role in the pathogenesis. Many different types of animal models have been developed to induce experimental scoliosis mimicking the pathoanatomical features of idiopathic scoliosis in human. The scoliosis deformity was believed to be induced by pinealectomy and mediated through the resulting melatonin-deficiency. However, the lack of upright mechanical spinal loading and inherent rotational instability of the curvature render the similarity of these models to the human counterparts questionable. Different concerns have been raised challenging the scientific validity and limitations of each model. The objectives of this review follow the logical need to re-examine and compare the relevance and appropriateness of each of the animal models that have been used for studying the etiopathogenesis of adolescent idiopathic scoliosis in human in the past 15 to 20 years.

ptk7 mutant zebrafish models of congenital and idiopathic scoliosis implicate dysregulated Wnt signalling in disease

Scoliosis is a complex genetic disorder of the musculoskeletal system, characterized by three-dimensional rotation of the spine. Curvatures caused by malformed vertebrae (congenital scoliosis (CS)) are apparent at birth. Spinal curvatures with no underlying vertebral abnormality (idiopathic scoliosis (IS)) most commonly manifest during adolescence. The genetic and biological mechanisms responsible for IS remain poorly understood due largely to limited experimental models. Here we describe zygotic ptk7 (Zptk7) mutant zebrafish, deficient in a critical regulator of Wnt signalling, as the first genetically defined developmental model of IS. We identify a novel sequence variant within a single IS patient that disrupts PTK7 function, consistent with a role for dysregulated Wnt activity in disease pathogenesis. Furthermore, we demonstrate that embryonic loss-of-gene function in maternal-zygotic ptk7 mutants (MZptk7) leads to vertebral anomalies associated with CS. Our data suggest novel molecular origins of, and genetic links between, congenital and idiopathic forms of disease.

Scoliosis is a complex genetic disorder characterized by spinal curvature. Here, the authors present experimental zebrafish models of idiopathic and congenital scoliosis and suggest a role for dysregulated Wnt activity in scoliosis aetiology.

Melatonin effects on bone: potential use for the prevention and treatment for osteopenia, osteoporosis, and periodontal disease and for use in bone-grafting procedures

An important role for melatonin in bone formation and restructuring has emerged, and studies demonstrate the multiple mechanisms for these beneficial actions. Statistical analysis shows that even with existing osteoporotic therapies, bone-related disease, and mortality are on the rise, creating a huge financial burden for societies worldwide. These findings suggest that novel alternatives need to be developed to either prevent or reverse bone loss to combat osteoporosis-related fractures. The focus of this review describes melatonin's role in bone physiology and discusses how disruption of melatonin rhythms by light exposure at night, shift work, and disease can adversely impact on bone. The signal transduction mechanisms underlying osteoblast and osteoclast differentiation and coupling with one another are discussed with a focus on how melatonin, through the regulation of RANKL and osteoprotegerin synthesis and release from osteoblasts, can induce osteoblastogenesis while inhibiting osteoclastogenesis. Also, melatonin's free-radical scavenging and antioxidant properties of this indoleamine are discussed as yet an additional mechanism by which melatonin can maintain one's bone health, especially oral health. The clinical use for melatonin in bone-grafting procedures, in reversing bone loss due to osteopenia and osteoporosis, and in managing periodontal disease is discussed.

Somatosensory cortectomy induces motor cortical hyperexcitability and scoliosis: an experimental study in developing rats

BACKGROUND CONTEXT

Dysfunctions in sensorimotor integration, reminiscent to those described in idiopathic dystonia, have been found in idiopathic scoliosis (IS) and might be involved in its pathogenesis. Studying the effects of experimental disruption of sensory cortex may shed further insight into the etiopathology of IS.

PURPOSE

To evaluate whether disruption of central sensorimotor integration through partial ablation of the somatosensory cortex leads to scoliosis in developing rats and to describe the effects of such an intervention on motor cortico-cortical inhibition and facilitation.

METHODS

Fifty Wistar rats aged 3 weeks were used in the study. Twenty-four rats underwent craniotomy and electrocoagulation of the sensory cortex (PAR1) in the right hemisphere. A second group of 16 rats underwent a sham operation with craniotomy but no electrocoagulation. A third group of 10 rats was used as intact controls. Four weeks after surgery, motor cortical excitability was assessed with paired-pulse electrical cortical stimulation. Neurologic and behavioral examinations were completed serially, and 10 weeks after surgery, X-ray examinations were performed in anesthetized rats to assess spinal curvature. Electromyographic recordings of paravertebral muscle activity were performed in waking rats. At the end of the study, rats were sacrificed, and histologic examinations of brain tissue were performed to confirm the extent of the lesion. A grant from a Government Health Research Fund without salaries assignment financed the study.

RESULTS

Almost half of the animals with somatosensory cortectomy (46%) developed scoliosis, with an average Cobb angle of 23 ± 8°. None of the animals in the sham or control groups developed scoliosis. Despite cortical lesions, no motor or behavioral deficits were apparent in the experimental group, and cortectomized rats were neurologically indistinguishable from sham or control animals, except for the presence of scoliosis. Cortico-cortical inhibition was significantly reduced in the hemisphere of scoliotic concavity in the cortectomized group but was normal in the other groups.

CONCLUSIONS

These findings indicate that altered sensorimotor integration may cause scoliosis without noticeable motor impairment. Reduced cortico-cortical inhibition was observed in cortectomized rats. This finding is consistent with results in adolescents with IS and suggests that alteration of cortical hemispheric balance of sensorimotor integration may play an important role in the pathogenesis of IS.

Animal models for scoliosis research: state of the art, current concepts and future perspective applications

PURPOSE

The purpose of this study was to provide the readers with a reliable source of animal models currently being utilized to perform state-of-the-art scoliotic research.

MATERIALS AND METHODS

A comprehensive search was undertaken to review all publications on animal models for the study of scoliosis within the database from 1946 to January 2011.

RESULTS

The animal models have been grouped under specific headings reflecting the underlying pathophysiology behind the development of the spinal deformities produced in the animals: genetics, neuroendocrine, neuromuscular, external constraints, internal constraints with or without tissue injury, vertebral growth modulation and iatrogenic congenital malformations, in an attempt to organize and classify these multiple scoliotic animal models. As it stands, there are no animal models that mimic the human spinal anatomy with all its constraints and weaknesses, which puts it at risk of developing scoliosis. What we do have are a multitude of models, which produce spinal deformities that come close to the idiopathic scoliosis deformity.

CONCLUSION

All these different animal models compel us to believe that the clinical phenotype of what we call idiopathic scoliosis may well be caused by a variety of different underlying pathologies.

Effects on bone by the light/dark cycle and chronic treatment with melatonin and/or hormone replacement therapy in intact female mice

In this study, the effects of the light/dark cycle, hormone replacement therapy (HRT), and nocturnal melatonin supplementation on osteogenic markers and serum melatonin levels were examined in a blind mouse model (MMTV-Neu transgenic mice). Melatonin levels in this mouse strain (FVB/N) with retinal degeneration (rd-/-) fluctuate in a diurnal manner, suggesting that these mice, although blind, still perceive light. Real-time RT-PCR analyses demonstrated that Runx2, Bmp2, Bmp6, Bglap, and Per2 mRNA levels coincide with melatonin levels. The effect of chronic HRT (0.5 mg 17β-estradiol + 50 mg progesterone in 1800 kcal of diet) alone and in combination with melatonin (15 mg/L drinking water) on bone quality and density was also assessed by histomorphometry and microcomputed tomography, respectively. Bone density was significantly increased (P < 0.05) after 1 yr of treatment with the individual therapies, HRT (22% increase) and nocturnal melatonin (20% increase) compared to control. Hormone replacement therapy alone also increased surface bone, decreased trabecular space, and decreased the number of osteoclasts without affecting osteoblast numbers compared to the control group (P < 0.05). Chronic HRT + melatonin therapy did not significantly increase bone density, even though this combination significantly increased Bglap mRNA levels. These data suggest that the endogenous melatonin rhythm modulates markers important to bone physiology. Hormone replacement therapy with or without nocturnal melatonin in cycling mice produces unique effects on bone markers and bone density. The effects of these therapies alone and combined may improve bone health in women in perimenopause and with low nocturnal melatonin levels from too little sleep, too much light, or age.

A novel calcium aluminate-melatonin scaffold enhances bone regeneration within a calvarial defect

Over 500,000 bone graft or bio-implant procedures are performed annually in the United States. It has been reported that osseous autograft procurement may result in donor site complications and bio-implant allografts have been associated with disease transmission. Ceramic scaffolds are only osteoconductive, limiting their clinical use. The objective of this study was to create a bone filler substitute with regenerating properties similar to natural bone. Therefore, melatonin and platelet-rich plasma (PRP) were utilized for their known osteoinductive properties. It was hypothesized that melatonin and/or PRP would enhance the osteoinductive and osteoconductive properties of calcium aluminate (CA) scaffolds to promote bone regeneration in a model of calvarial defects. The biocompatibility of CA and CA-Mel scaffolds was tested in vitro and in vivo. Data show that CA-Mel scaffolds, in comparison with CA scaffolds, enhanced the adhesion, viability, and proliferation of normal human osteoblasts cells but not that of NIH3T3 fibroblasts. Data also showed that human adult mesenchymal stem cells grown on CA or CA-Mel scaffolds showed a time-dependent induction into osteoblasts over 14days revealed through scanning electron microscopy and by alkaline phosphatase analyses. Implantation of CA-Mel scaffolds into critical size calvarial defects in female, ovariectomized rats showed that the CA-Mel scaffolds were biocompatible, allowed for tissue infiltration, and showed evidence of scaffold biodegradation by 3 and 6months. Bone regeneration, assessed using fluorochrome labeling at 3 and 6months, was greatest in animals implanted with the CA-Mel scaffold. Overall, results from this study show that CA-Mel scaffolds were osteoconductive and osteoinductive.

The creation of scoliosis by scapula-to-contralateral ilium tethering procedure in bipedal rats: a kyphoscoliosis model

STUDY DESIGN

Randomized trial.

OBJECTIVE

To create a new scoliotic model.

SUMMARY OF BACKGROUND DATA

Although there were a lot of modeling techniques producing scoliosis, failed was the creation of a scoliotic animal model all characterized by the evident axial rotation of vertebrae body, the simulation of the human erect posture, and avoiding direct traumas to the spine, the spinal cord, ribs, or glands in modeling techniques.

METHODS

A total of 45 4-week-old female wistar rats were randomly divided into three groups. Group 1 underwent subcutaneous left scapula-to-contralateral ilium tethering procedure with a nonadsorbable suture, which made the spine convex toward right side, and then removed forelimbs and tails of rats to create the bipedal rats. Tethering sutures were cut at postoperative eighth week, and the spines of rats were then observed during 2 weeks. Group 2 was the same as group 1 but in which scapula-to-ipsilateral ilium tethering procedure was performed. Group 3 was the same as group 1 except that the bipedal rats were not created. All postoperative rats were fed separately in special high cages for groups 1 and 2 or in standard cages for group 3.

RESULTS

At 2 weeks after tether release, the incidence of vertebral rotation was significantly higher in group 1 than in group 2 (P = 0.004). The differences in degrees of scoliosis and kyphosis between groups at the time of initial tethering were not found to be significant (P > 0.05), whereas those at 2 weeks after tether release were significantly larger in group 1 than in group 3 (P < 0.01). There were no significant differences in postoperative first food-taking duration, body weight, spinal relative length, modeling mortality, the incidences of reoperation, and scoliosis between groups (all P > 0.05).

CONCLUSION

The scoliotic model created by scapula-to-contralateral ilium tethering procedure in bipedal rats can preferably simulate the human scoliosis.

A common polymorphism rs3781637 in MTNR1B is associated with type 2 diabetes and lipids levels in Han Chinese individuals

Background

Several studies have shown that common variants in the MTNR1B gene were associated with fasting glucose level and type 2 diabetes. The purpose of this study was to examine whether tagging single nucleotide polymorphisms (SNPs) in the MTNR1B region were associated with type 2 diabetes and related traits in a Han Chinese population.

Methods

We investigated the association of polymorphisms in the MTNR1B gene with type 2 diabetes by employing a case-control study design (1118 cases and 1161 controls). Three tagging SNPs (rs10830963, rs3781637, and rs1562444) with R²>0.8 and minor allele frequency>0.05 across the region of the MTNR1B gene were studied. Genotyping was performed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy using a MassARRAY platform.

Results

The polymorphism rs3781637 was associated with type 2 diabetes adjusted for age, sex and body mass index (BMI) in the additive model and recessive model (OR = 1.22, 95% CI 1.01-1.46, p = 0.038 and OR = 2.81, 95% CI 1.28-6.17, p = 0.01, respectively). In the non-diabetic controls, rs3781637 was nominally associated with plasma triglyceride, total cholesterol and low density lipoprotein cholesterol (LDL-C) levels in the recessive model (p = 0.018, 0.008 and 0.038, respectively). After adjustment for multiple comparisons, the associations of rs3781637 with total cholesterol and LDL-C remained significant in the recessive model (the empirical p = 0.024 and 0.045, respectively), but the association between rs3781637 and triglyceride became non-significant (the empirical p = 0.095). The associations of rs10830963 and rs1562444 with type 2 diabetes and related traits were not significant in the additive, dominant and recessive models.

Conclusions

The rs3781637 A/G polymorphism of the MTNR1B gene is associated with type 2 diabetes, plasma, total cholesterol and LDL-C levels in the Han Chinese population.

Experimental animal models in scoliosis research: a review of the literature

BACKGROUND CONTEXT

Many animal species and an overwhelming variety of procedures that produce an experimental scoliosis have been reported in the literature. However, varying results have been reported on identical procedures in different animal species. Furthermore, the relevance of experimental animal models for the understanding of human idiopathic scoliosis remains questionable.

PURPOSE

To give an overview of the procedures that have been performed in animals in an attempt to induce experimental scoliosis and discuss the characteristics and significance of various animal models.

STUDY DESIGN

Extensive review of the literature on experimental animal models in scoliosis research.

METHODS

MEDLINE electronic database was searched, focusing on parameters concerning experimental scoliosis in animal models. The search was limited to the English, French, and German languages.

RESULTS

The chicken appeared to be the most frequently used experimental animal followed by the rabbit and rat. Additionally, scoliosis has been induced in primates, goats, sheep, pigs, cows, dogs, and frogs. Procedures widely varied from systemic to local procedures.

CONCLUSIONS

Although it has been possible to induce scoliosis-like deformities in many animals through various ways, this always required drastic surgical or systemic interventions, thus making the relation to human idiopathic scoliosis unclear. The basic drawback of all used models remains that no animal resembles the upright biomechanical spinal loading condition of man, with its inherent rotational instability of certain spinal segments. The fundamental question remains what the significance of these animal models is to the understanding of human idiopathic scoliosis.

The role of melatonin in the pathogenesis of adolescent idiopathic scoliosis (AIS)

The cause of adolescent idiopathic scoliosis (AIS) in humans remains obscure and probably multifactorial. At present, there is no proven method or test available to identify children or adolescent at risk of developing AIS or identify which of the affected individuals are at risk of progression. Reported associations are linked in pathogenesis rather than etiologic factors. Melatonin may play a role in the pathogenesis of scoliosis (neuroendocrine hypothesis), but at present, the data available cannot clearly show the role of melatonin in producing scoliosis in humans. The data regarding human melatonin levels are mixed at best, and the melatonin deficiency as a causative factor in the etiology of scoliosis cannot be supported. It will be an important issue of future research to investigate the role of melatonin in human biology, the clinical efficacy, and safety of melatonin under different pathological situations. Research is needed to better define the role of all factors in AIS development.

Melatonin delays cell proliferation by inducing G1 and G2 /M phase arrest in a human osteoblastic cell line hFOB 1.19

A recent prospective study indicated that melatonin supplements may reduce the progression of idiopathic scoliosis, the most common deformity of the spine. This form of scoliosis occurs during rapid skeletal growth. To date, however, there is no direct evidence regarding an antiproliferative effect of melatonin at the level of osteoblasts. Herein, we investigated whether melatonin inhibits cell proliferation in a normal human fetal osteoblastic cell line hFOB 1.19. MTT staining showed that at 1 mm concentrations, melatonin significantly inhibited osteoblast proliferation in time-dependent manner. Flow cytometry demonstrated that melatonin significantly increased the fraction of cells in G(0) /G(1) phase of the cell cycle, while simultaneously reducing the proportion in the G(2) /M phase rather than the S phase. Western blot and real-time PCR analyses further confirmed that melatonin's inhibitory effect was possibly because of downregulation of cyclin D1 and CDK4, related to the G(1) phase, and of cyclin B1 and CDK1, related to the G(2) /M phase. There was no downregulation of cyclin E, CDK2, and cyclin A, which are related to G(1) /S transition and S phase. In addition, the trypan blue dye exclusion assay showed that cell viability was not changed by melatonin relative to control cells. These findings provide evidence that melatonin may significantly delay osteoblast proliferation in a time-dependent manner and this inhibition involves the downregulation of cyclin D1 and CDK4, related to the G(1) phase, and of cyclin B1 and CDK1, related to the G(2) /M phase.

Genetic variants in melatonin synthesis and signaling pathway are not associated with adolescent idiopathic scoliosis

STUDY DESIGN

Genetic association study investigating the association of genetic markers of melatonin signaling and biosynthesis with adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To determine whether gene polymorphisms related to the melatonin signaling or biosynthesis pathways are associated with AIS.

SUMMARY OF BACKGROUND DATA

Data have been published on the potential role of gene polymorphisms for melatonin receptor (MTNR) 1B in predicting AIS. Other genes in the melatonin pathways have been tested for association with AIS.

METHODS

The following genes involved in melatonin synthesis were evaluated herein: tryptophan 5-hyroxylase 1 (TPH1), serotonin N-acetyltransferase (SNAT), and hydroxyindoleo-methyltransferase (HIOMT). In addition, proteins involved in melatonin signaling were also included in this study: MTNR1A, MTNR1B, and protein kinase C delta (PKCd). High throughput microarray-based single nucleotide polymorphism (SNP) genotyping was performed for these seven genes using DNA samples from 589 AIS subjects and 1533 ethnically matched controls. Chi-square analyses of allele frequency between AIS cases and controls were performed and odds ratios were calculated for all SNP markers.

RESULTS

Three SNPs were tested for both MTNR1A and HIOMT, 4 for TPH1 and SNAT, 12 for PKCd, and 7 for MTNR1B. The minor allele frequencies were not significantly different between AIS cases and controls. No association was thus found between AIS and the investigated SNPs.

CONCLUSIONS

Genetic polymorphisms associated with either melatonin synthesis or its signaling pathway are unlikely to be commonly associated with AIS.

Abnormal proliferation and differentiation of osteoblasts from girls with adolescent idiopathic scoliosis to melatonin

Melatonin deficiency has been postulated as an etiologic factors in adolescent idiopathic scoliosis (AIS). In previous studies, melatonin was shown to regulate skeletal growth and bone formation in both humans and rats. Although it remains controversial whether there are differences in serum melatonin level between AIS and control subjects, melatonin signaling pathway dysfunction in osteoblasts has been reported in patients with AIS. Recently, our group found that melatonin receptor 1B (MT2) gene polymorphism was associated with the occurrence of AIS. Hence, the present study investigated the effect of melatonin on AIS osteoblasts. In vitro assays were performed with osteoblasts isolated from 17 severe AIS girls and nine control subjects. The osteoblasts were exposed to different concentrations of melatonin for 3 days. The effects of melatonin on cell proliferation (as evidenced by MTT assay) and differentiation (demonstrated by alkaline phosphatase activity) were determined. In the control group, melatonin significantly stimulated osteoblasts to proliferate and differentiate. However, in the AIS group, the stimulatory effects of melatonin were not discernible. Importantly, this finding demonstrated that there is a significant difference between AIS and control osteoblasts in functional response toward melatonin. Melatonin-stimulated proliferation of control osteoblasts was inhibited by the MT2 antagonist, 4-phenyl-2-propionamidotetraline, as well as by luzindole, a nonselective melatonin receptor antagonist, suggesting that MT2 is associated with the proliferative action of melatonin. The lack of response in AIS osteoblasts might be because of dysfunction of the melatonin signaling pathway, which may contribute to the low bone mineral density and abnormal skeletal growth observed in patients with AIS.

Scientific basis for the potential use of melatonin in bone diseases: osteoporosis and adolescent idiopathic scoliosis

The objective of this paper was to analyze the data supporting the possible role of melatonin on bone metabolism and its repercussion in the etiology and treatment of bone pathologies such as the osteoporosis and the adolescent idiopathic scoliosis (AIS). Melatonin may prevent bone degradation and promote bone formation through mechanisms involving both melatonin receptor-mediated and receptor-independent actions. The three principal mechanisms of melatonin effects on bone function could be: (a) the promotion of the osteoblast differentiation and activity; (b) an increase in the osteoprotegerin expression by osteoblasts, thereby preventing the differentiation of osteoclasts; (c) scavenging of free radicals generated by osteoclast activity and responsible for bone resorption. A variety of in vitro and in vivo experimental studies, although with some controversial results, point toward a possible role of melatonin deficits in the etiology of osteoporosis and AIS and open a new field related to the possible therapeutic use of melatonin in these bone diseases.

The pathogenesis of adolescent idiopathic scoliosis: review of the literature

STUDY DESIGN

Review of the literature on the pathogenesis of adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To discuss the different theories that have appeared on this subject.

SUMMARY OF BACKGROUND DATA

The pathogenesis of AIS, a condition exclusive to humans, has been the subject of many studies. Over the years, practically every structure of the body has been mentioned in the pathogenesis of AIS; however, the cause of this spinal deformity remains little understood. The pathogenesis of this condition is termed multifactorial.

METHODS

PubMed and Google Scholar electronic databases were searched focused on parameters concerning the pathogenesis of adolescent idiopathic scoliosis. The search was limited to the English language.

RESULTS

No single causative factor for the development of idiopathic scoliosis has been identified, it is thus termed multifactorial. AIS is a complex genetic disorder. The fully erect posture, which is unique to humans, seems to be a prerequisite for the development of AIS.

CONCLUSION

Although any or all of the mentioned factors in this review may play a certain role in the initiation and progression of AIS at a certain stage, the presented material suggests that in the observed deformation, genetics, and the unique mechanics of the fully upright human spine play a decisive role.

Idiopathic-type scoliosis is not exclusive to bipedalism

Human familial/idiopathic-type scoliosis (IS) is a complex genetic disorder for which the cause is unknown. The curve phenotype characteristically demonstrates pronounced morphological and developmental variability that is likely a consequence of biomechanical, environmental, and genetic differences between individuals. In addition, risk factors that affect the propensity for curves to progress to severity are unknown. Progress in understanding the fundamental biology of idiopathic-type scoliosis has been limited by the lack of a genetic/developmental animal model. Prior to consideration of teleosts, developmental idiopathic-type scoliosis has been considered to be exclusive to humans. Consequently, there is the notion that the syndrome is a result of bipedalism, and many studies try to explain the deformity from this anthrocentric viewpoint. This perspective has been reinforced by the choice of animals used for study, in that chickens and bipedal rats and mice demonstrate idiopathic-type curvature when made melatonin-deficient, but quadrupedal animals do not. Overlooked is the fact that teleosts also demonstrate similar curvature when made melatonin-deficient. Our characterization of the guppy curveback has demonstrated that non-induced idiopathic-type curvature is not exclusive to humans, nor bipedalism. We hypothesize that unique morphological, developmental and genetic parallels between the human and guppy syndromes are due to common molecular pathways involved in the etiopathogenesis of both phenotypes. We explore established gene conservation between human and teleost genomes that are in pathways hypothesized to be involved in the IS syndrome. We present non-induced vertebral wedging as a unique shared feature in IS and curveback that suggests a similar interaction between a molecular phenotype on the level of the vertebral anatomy, and biomechanics. We propose that rather than bipedalism per se, expression of idiopathic-type scoliosis is dependent on normal spinal loading applied along the cranio-caudal axis that interacts with an unknown factor causing the primary curve. In this regard, a comparative biological approach using a simplified teleost model will promote discovery of basic processes integral to idiopathic-type scoliosis in teleosts and humans, and highlight human-specific aspects of the deformity.

Lack of association between the promoter polymorphism of the MTNR1A gene and adolescent idiopathic scoliosis

STUDY DESIGN

A genetic association study to investigate variation of the melatonin receptor 1A (MTNR1A) gene in adolescent idiopathic scoliosis (AIS) patients.

OBJECTIVE

To determine whether the MTNR1A gene promoter polymorphism is associated with the predisposition and/or disease severity of AIS.

SUMMARY OF BACKGROUND DATA

An involvement of the dysfunction of the melatonin pathway in the etiopathogenesis of AIS has been implicated in several studies. Recently, our group has found that the promoter polymorphism of the melatonin receptor 1B (MTNR1B) gene was associated with the occurrence of AIS. Hence, it is of interest to determine whether the promoter polymorphism of the MTNR1A gene could also associated with the occurrence or curve severity of AIS.

METHODS

A total of 226 AIS girls and 277 normal controls were recruited. SNP rs2119882 in the promoter region (-369 bp) of the MTNR1A gene was selected for the present study. Genotyping was performed by PCR-RFLP. Statistical analysis of genotype frequencies between case and control was performed by chi test. One-way ANOVA was used in comparison of mean maximum Cobb angles with different genotypes in case-only analysis.

RESULTS

Genotype and allele frequencies were comparable between case and control for SNP rs2119882 (P > 0.05). The mean maximum Cobb angles of different genotypes were similar with each other for SNP rs2119882.

CONCLUSIONS

Promoter polymorphism of the MTNR1A gene was not associated with the occurrence or curve severity of AIS. The MTNR1A gene may not be involved in the etiopathogenesis of AIS.

Melatonin receptor 1B (MTNR1B) gene polymorphism is associated with the occurrence of adolescent idiopathic scoliosis

STUDY DESIGN

A genetic association study to comprehensively investigate variations of melatonin receptor 1B gene polymorphism by a set of tagging single nucleotide polymorphisms (tagSNPs) derived from the International Hapmap project.

OBJECTIVES

To determine whether melatonin receptor 1B (MTNR1B) gene polymorphisms are associated with the predisposition and/or disease severity of adolescent idiopathic scoliosis (AIS).

SUMMARY OF BACKGROUND DATA

Linkage studies suggested a genetic predisposition for AIS. In addition, evidence showed that AIS might be related to melatonin deficiency and dysfunction of melatonin signaling pathway. Locating in one of the chromosomal regions linked to AIS, MTNR1B gene is a potential candidate gene for AIS.

METHODS

This study was carried out in 2-stage case-control analysis: 1) initial screening (472 cases and 304 controls) and 2) separate replication test (342 cases and 347 controls) to confirm results in the screening. In the first screening stage, 5 tagSNPs were selected to cover most of the genetic variation in the MTNR1B gene. In the second stage, SNPs showing association in the screening stage were studied in a separate replication sample set to confirm the association. Genotyping was performed by PCR-RFLP.

RESULTS

The first stage showed a putative association between rs4753426 and AIS, which was confirmed in the replication sample set. By meta-analysis, the frequency of C allele of this SNP locating in the promoter was significantly higher in the cases than controls (P = 0.006 aftermeta-analysis). Subjects with the CC genotype had an odds ratio of 1.29 for AIS. Another SNP rs741837 in promoter region, being moderate linkage disequilibrium with rs4753426, was also marginally associated with AIS.

CONCLUSION

Polymorphisms of the promoter of MTNR1B gene were associated with AIS, but not with the curve severity in AIS patients. This suggested that MTNR1B was an AIS predisposition gene.

Melatonin inhibits fatty acid-induced triglyceride accumulation in ROS17/2.8 cells: implications for osteoblast differentiation and osteoporosis

Melatonin is produced not only by the pineal gland but by cells of the bone marrow. Moreover, melatonin is known to promote osteogenic differentiation in several cell line models and in multipotential bone marrow mesenchymal stem cells. Fatty acids have been independently shown to direct such cells to acquire the phenotype and molecular characteristics of adipocytes. To examine the effect of melatonin on intracellular triglyceride accumulation, an indicator of adipogenic differentiation in the rat osteoblast-like ROS17/2.8 cell line, cells were incubated with added oleic acid (100 μM), fixed and stained with Oil Red O. Cellular lipid accumulation was quantitated by an Oil Red O method highly specific for triglycerides and expressed as a triglyceride accumulation index (TGAI, triglyceride per cell). Melatonin in nanomolar concentrations inhibited oleic acid-induced triglyceride accumulation. To identify the mechanism by which melatonin reduces triglyceride accumulation, cells were incubated with the two melatonin receptor antagonists, luzindole and S20928, or forskolin, a stimulator of adenylyl cyclase and cAMP production. These compounds prevented the inhibitory effect of melatonin on triglyceride accumulation, indicating that melatonin acts through known melatonin receptor-mediated mechanisms. In view of the previously demonstrated positive effects of melatonin in promoting osteoblastic differentiation in ROS17/2.8 cells and their reciprocal adipocytic differentiation induced by fatty acids, our observations may serve to relate the known age-related decreases of melatonin production, the shift in the bone marrow toward an adipocytic line of cell development, and the development of osteoporosis during aging.

Therapeutic treatments potentially mediated by melatonin receptors: potential clinical uses in the prevention of osteoporosis, cancer and as an adjuvant therapy

Melatonin's therapeutic potential is grossly underestimated because its functional roles are diverse and its mechanism(s) of action are complex and varied. Melatonin produces cellular effects via a variety of mechanisms in a receptor independent and dependent manner. In addition, melatonin is a chronobiotic agent secreted from the pineal gland during the hours of darkness. This diurnal release of melatonin impacts the sensitivity of melatonin receptors throughout a 24-hr period. This changing sensitivity probably contributes to the narrow therapeutic window for use of melatonin in treating sleep disorders, that is, at the light-to-dark (dusk) or dark-to-light (dawn) transition states. In addition to the cyclic changes in melatonin receptors, many genes cycle over the 24-hr period, independent or dependent upon the light/dark cycle. Interestingly, many of these genes support a role for melatonin in modulating metabolic and cardiovascular physiology as well as bone metabolism and immune function and detoxification of chemical agents and cancer reduction. Melatonin also enhances the actions of a variety of drugs or hormones; however, the role of melatonin receptors in modulating these processes is not known. The goal of this review is to summarize the evidence related to the utility of melatonin as a therapeutic agent by focusing on its other potential uses besides sleep disorders. In particular, its use in cancer prevention, osteoporosis and, as an adjuvant to other therapies are discussed. Also, the role that melatonin and, particularly, its receptors play in these processes are highlighted.