Development of scoliosis following pinealectomy in young chickens is not the result of an artifact of the surgical procedure

Current models to understand the onset and progression of scoliotic deformities in adolescent idiopathic scoliosis: a systematic review

PURPOSE

To create an updated and comprehensive overview of the modeling studies that have been done to understand the mechanics underlying deformities of adolescent idiopathic scoliosis (AIS), to predict the risk of curve progression and thereby substantiate etiopathogenetic theories.

METHODS

In this systematic review, an online search in Scopus and PubMed together with an analysis in secondary references was done, which yielded 86 studies. The modeling types were extracted and the studies were categorized accordingly.

RESULTS

Animal modeling, together with machine learning modeling, forms the category of black box models. This category is perceived as the most clinically relevant. While animal models provide a tangible idea of the biomechanical effects in scoliotic deformities, machine learning modeling was found to be the best curve-progression predictor. The second category, that of artificial models, has, just as animal modeling, a tangible model as a result, but focusses more on the biomechanical process of the scoliotic deformity. The third category is formed by computational models, which are very popular in etiopathogenetic parameter-based studies. They are also the best in calculating stresses and strains on vertebrae, intervertebral discs, and other surrounding tissues.

CONCLUSION

This study presents a comprehensive overview of the current modeling techniques to understand the mechanics of the scoliotic deformities, predict the risk of curve progression in AIS and thereby substantiate etiopathogenetic theories. Although AIS remains to be seen as a complex and multifactorial problem, the progression of its deformity can be predicted with good accuracy. Modeling of AIS develops rapidly and may lead to the identification of risk factors and mitigation strategies in the near future. The overview presented provides a basis to follow this development.

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.

The metabolic basis of adolescent idiopathic scoliosis: 2011 report of the "metabolic" workgroup of the Fondation Yves Cotrel

OBJECTIVE

The purpose of this review is to elucidate the metabolic processes involved in the pathogenesis of adolescent idiopathic scoliosis (AIS) in light of research by the present authors as well as current literature.

METHODS

Pathogenetic mechanisms involved in AIS were modeled as (a) a form of neuromuscular scoliosis (in conjunction with an adverse mechanical environment such as bipedality), in which hormonal and other chemical factors act as regulators of skeletal muscle tone and function; (b) as a consequence of an abnormality in growth of the spinal column (in conjunction with an adverse mechanical environment such as bipedality), in which hormones and other chemical factors act as regulators of growth; and (c) as a mechanical failure of one side of the vertebral column due to a defect in trabecular formation or mineralization (in conjunction with an adverse mechanical environment such as bipedality); in which hormonal and other chemical factors act as regulators of bone formation, mineralization and/or resorption.

RESULTS AND CONCLUSION

Current evidence supporting these models individually or in combination is discussed.

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.

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.

Spinal deformity in triploid grass carp Ctenopharyngodon idella (Valenciennes)

From mid-2004 to mid-2005, several grass carp, Ctenophayngodon idella (Valenciennes), showing evidence of spinal deformity were presented to the Aquatic Animal Health Program, Cornell University. The carp were from three separate locations in New York State. The first case involved several fish from a natural body of water in the Catskill Mountain region of south-eastern New York State. The second was a single affected individual from a private pond in the Fingerlakes region of Central New York State. The third was a single individual from the Cold Springs Harbor Fish Hatchery, Cold Springs Harbor, Long Island. All fish were at least 7 years of age. Radiographs and computed tomography (CT) scans revealed the deformities to be of bony origin. The spinal deformities were characterized by variable amounts of kyphosis, scoliosis and rotation. While it is not possible to determine the specific cause(s) of the lesions, we consider a genetic component as a likely contributor to the observed pathology.

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.

[Molecular and genetic aspects of idiopathic scoliosis. Blood test for idiopathic scoliosis]

Spinal deformities, and particularly scoliosis, are the most frequent forms of orthopedic deformities in children and adolescents. About 1-6% of the population has scoliosis. This disorder leads to severe spinal deformities and predominantly affects adolescent girls.Although the multifactorial origin of adolescent idiopathic scoliosis (AIS) is broadly recognized, the genetic causes of AIS are still largely unknown. Our previous studies suggested a generalized dysfunction of melatonin transduction (the hormone that is primarily produced in the brain and epiphysis). In the meantime we have demonstrated that such a defect of signal transduction is caused by chemical alterations, which inactivate the function of the inhibitory G protein-coupled melatonin receptors. This discovery has led to the development of the first blood test to detect children without symptoms who are at risk of developing scoliosis. Since a single function (cellular reaction to melatonin) is determined, the unique advantage of this test is that it can be performed without knowledge of mutations in defective genes that could provoke the onset of AIS.

Idiopathic scoliosis and pineal lesions in Australian children

PURPOSE

To determine whether treatment of pineal lesions in children is associated with development of idiopathic scoliosis.

METHODS

38 boys and 10 girls with pineal lesions were identified. Their mean age at presentation was 10 years. The pineal pathology varied from cysts and epidermoid to teratoma, germinoma, pineocytoma, and glioblastoma. Treatment ranged from biopsy/extirpation to radiotherapy.

RESULTS

12 patients died. No scoliosis was found in any females or any of the deceased. Two boys had scoliosis: one had a 12-degree right upper thoracic curve with 32-degree kyphosis and the other had a 60-degree right thoracolumbar idiopathic curve, requiring a 2-stage arthrodesis.

CONCLUSION

Pineal ablation is not related to the development of idiopathic scoliosis in humans.

Validation, reliability, and complications of a tethering scoliosis model in the rabbit

This study was conducted to refine a small animal model of scoliosis, and to quantify the deformities throughout its growth period. Subcutaneous scapula-to-contralateral pelvis tethering surgery was selected due to its minimally invasive nature and potential applicability for a large animal model. The procedure was performed in 7-week-old New Zealand white rabbits. Group A animals (n=9) underwent the tethering procedure with a suture that spontaneously released. Group B animals (n=17) had the identical procedure with a robust tether and pelvic fixation, which was maintained for 2 months during growth. All animals developed immediate post-operative scoliosis with a Cobb angle of 23 degrees (range, 6-39 degrees) in group A and 59 degrees (range, 24-90 degrees) in group B animals. During the 2 month post-tethering, group A animals lost their tether and scoliosis resolved, whereas all animals in group B maintained their tether until scheduled release at which time the mean scoliosis was 62 degrees. Immediately after tether release, group B scoliosis decreased to a mean 53 degrees. Over the following 4 months of adolescent growth, the scoliosis decreased to a mean of 43 degrees at skeletal maturity; the decrease usually occurred in animals with less than 45 degrees curves at tether release. Radiographs revealed apical vertebral wedging (mean 19 degrees ) in all group B animals. Sagittal spinal alignment was also assessed, and for group B animals, the scoliotic segment developed mild to moderate kyphosis (mean 28 degrees) and torsional deformity, but the kyphosis resolved by 4 months after tether-release. Complications specific to this technique included a high rate of transient scapulothoracic dissociation and cases of cor pulmonale. In conclusion, this tethering technique in immature rabbits consistently produced scoliosis with vertebral wedging when the tether was intact through the first 2 months of the protocol. The transient exaggeration of kyphosis suggests that the production of scoliosis is not necessarily dependent on lordosis in this model. Because this technique does not violate thoracic or spinal tissues, it may be useful in the investigation of secondary physiologic effects of mechanically-induced scoliosis, and may be scalable to larger animal species.

Melatonin signaling dysfunction in adolescent idiopathic scoliosis

STUDY DESIGN

In vitro assays were performed with bone-forming cells isolated from 41 patients with adolescent idiopathic scoliosis and 17 control patients exhibiting another type of scoliosis or none.

OBJECTIVE

To determine whether a dysfunction of the melatonin-signaling pathway in tissues targeted by this hormone is involved in adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Pinealectomy in chicken has led to the formation of a scoliotic deformity, thereby suggesting that a melatonin deficiency may be at the source of adolescent idiopathic scoliosis. However, the relevance of melatonin in the etiopathogenesis of that condition is controversial because most studies have reported no significant change in circulating levels of melatonin in patients with adolescent idiopathic scoliosis.

METHODS

Primary osteoblast cultures prepared from bone specimens obtained intraoperatively during spine surgeries were used to test the ability of melatonin and Gpp(NH)p, a GTP analogue, to block cAMP accumulation induced by forskolin. In parallel, melatonin receptor and Gi protein functions were evaluated by immunohistochemistry and by coimmunoprecipitation experiments.

RESULTS

The cAMP assays demonstrated that melatonin signaling was impaired in osteoblasts isolated from adolescent idiopathic scoliosis patients to different degrees allowing their classification in 3 distinct groups based on their responsiveness to melatonin or Gpp(NH)p.

CONCLUSION

Melatonin signaling is clearly impaired in osteoblasts of all patients with adolescent idiopathic scoliosis tested. Classification of patients with adolescent idiopathic scoliosis in 3 groups based on functional in vitro assays suggests the presence of distinct mutations interfering with the melatonin signal transduction. Posttranslational modifications affecting Gi protein function, such as serine residues phosphorylation, should be considered as one possible mechanism in the etiopathogenesis of AIS.

Effect of melatonin suppression on scoliosis development in chickens by either constant light or surgical pinealectomy

STUDY DESIGN

This study was designed to compare the effect of suppression of melatonin secretion by bright light in chickens with that of surgical pinealectomy.

OBJECTIVE

To determine whether suppression of melatonin secretion without surgery in chickens can result in scoliosis development.

SUMMARY OF BACKGROUND DATA

Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. Conversely, cutting of the pineal stalk without removal of the pineal gland will also result in scoliosis. This study addresses the question of whether constant bright light can induce scoliosis formation, because it is well known that 24-hour bright lighting conditions can suppress the secretion of melatonin to an equivalent level as pinealectomy.

MATERIALS AND METHOD

Seventy-seven newborn Nihon chickens were separated into three groups. A control group (n = 21) with no surgery performed; a pinealectomy group (n = 15) that served as surgical controls; and a constant light group (n = 41). The first two groups were kept together in a strict 12-hour light-dark cycle, whereas the third group was separately kept with constant lighting conditions (>100 lux). All the chickens were radiographed at two weekly intervals, and blood was taken during the middle of the light and dark cycles for serum melatonin assay using ELISA.

RESULTS

Fifty-four percent of the pinealectomized chickens had scoliosis develop by 6 weeks. None of the constant-light chickens or controls had scoliosis develop for up to 11 weeks. Measurements of serum melatonin levels of the constant light group confirm that secretion is suppressed.

CONCLUSION

This study suggests that for scoliosis to develop in chickens, the surgical operation itself is important and challenges the role of melatonin as an isolated etiological factor in the development of scoliosis.