Pinealectomy In Chickens Research Articles

Evaluation of GPR50, hMel-1B, and ROR-α Melatonin-related Receptors and the Etiology of Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity in children. Studies have shown low melatonin levels resulting from pinealectomy in chickens and mice result in the development scoliosis, whereas supplementation with melatonin after the pinealectomy prevented it. The mere characterization of low melatonin levels is not sufficient to explain the development of idiopathic scoliosis in primates and humans, but we hypothesize that a mutation in melatonin-related receptors may be involved with the development of scoliosis. The coding, splice-site, and promoter regions of 3 melatonin-related receptors (hMel-1B, RORalpha, and GPR50) were evaluated by DNA sequencing for variants associated with the phenotype of adolescent idiopathic scoliosis. An initial screening of 50 scoliosis patients with adolescent idiopathic scoliosis was compared with 50 controls by DNA sequencing of the 3 receptors. Additional cases and controls were evaluated when genetic variants were observed (for a total of 885 individuals). No significant differences were found in the hMel-1B and RORalpha receptors. We found 2 cSNPs in GPR50 (rs561077 and rs13440581) in the initial 50 patients. To evaluate the significance of these cSNPs, an additional 356 patients and 429 controls were analyzed. When the combined groups were analyzed, no significant associations were observed. Despite the observed relationship between melatonin and scoliosis, there is no significant association between mutations found in any known melatonin-related receptors with adolescent idiopathic scoliosis. The strong evidence of a melatonin-related cause for the development of idiopathic scoliosis still encourages research into undiscovered melatonin-related receptors, melatonin-related hormones, and the catalytic enzymes for the serotonin-melatonin pathway. This investigation is a genetic testing of the remaining currently known melatonin-related receptors that have not been analyzed earlier for association with AIS. Given the support in the literature of a relationship between melatonin and AIS, we have shown no mutations in any of the known melatonin-related receptor in patients with AIS.

Pinealectomy in the chicken: a good model of scoliosis?

The phenomenon of spinal deformity in the pinealectomized chicken has led researchers to postulate a disturbance of melatonin activity as a potential cause of adolescent idiopathic scoliosis (AIS). More recently, structural differences between curves seen in this model and those seen in scoliosis have been highlighted suggesting the deformities observed are not as similar as first thought. We examined melatonin levels, and the radiological and histological characteristics of scoliosis after pinealectomy in chickens. They underwent pinealectomy (P) at 2 days of age, sham surgery (S) or served as controls (C). Mean melatonin levels were 32.9 pmol/L (P), 175 pmol/L (S) and 227.3 pmol/L (C). Scoliosis developed in 75% of chickens after pinealectomy and 38% after a sham procedure. Nineteen percent of unoperated controls also developed scoliosis. A lower melatonin level was associated with the development of scoliosis (p < or = 0.001), but exceptions were seen with levels up to 265 pmol/L observed in one case. Most of the curves occurring spontaneously and after sham surgery and almost half after pinealectomy were short angular curves: distinct from those resembling idiopathic scoliosis. These occur over one or two segments and are characterized by marked apical wedging, frequently associated with subluxation or dislocation. The intervertebral joint in the chicken is more like a synovial joint histologically than an intervertebral disc. This study highlights important differences between the chicken and the human, and between their respective spinal deformities. Caution is advised when drawing conclusions regarding the pathogenesis of AIS from this model.

Récents progrès dans l’étiopathogénie de la scoliose idiopathique de l’adolescent et nouveaux concepts moléculaires

Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis that affects a significant number of young teenagers, mainly females (0.2-6 % of the population). Historically, several hypothesis were postulated to explain the aetiology of AIS, including genetic factors, biochemical factors, mechanics, neurological, muscular factors and hormonal factors. The neuroendocrine hypothesis involving a melatonin deficiency as the source for AIS has generated great interest. This hypothesis stems from the fact that experimental pinealectomy in chicken, and more recently in rats maintained in a bipedal mode, produces a scoliosis. The biological relevance of melatonin in idiopathic scoliosis is controversial since no significant decrease in circulating melatonin level has been observed in a majority of studies. Analysis of melatonin signal transduction in musculoskeletal tissues of AIS patients demonstrated for the first time a defect occurring in a cell autonomous manner in different cell types isolated from AIS patients suffering of the most severe form of that disease. These results have led to a classification of AIS patients in three different functional groups depending on their response to melatonin, suggesting that the cause of AIS involves several genes. Molecular analysis showed that melatonin signaling dysfunction is triggered by an increased phosphorylation of Gi proteins inactivating their function. This discovery has led to development of a first scoliosis screening assay. This test, using blood sample, is currently in clinical validation process in Canada and could be used for screening children at high risk of developing AIS.

Changes in Melatonin Receptors in Relation to the Development of Scoliosis in Pinealectomized Chickens

The 2[125I]iodomelatonin binding assay was used to investigate the involvement of melatonin receptors in the development of scoliosis in pinealectomized chickens. To compare the binding properties of melatonin receptors in the thoracic spinal cord between pinealectomized chickens that had scoliosis develop and those that did not. Surgical pinealectomy in young chickens induced scoliosis with a reported incidence of 50% to 100%. The factors regulating the development of scoliosis in this animal model are unclear. Melatonin receptors have been shown in the spinal cord of chickens, but their functions are still unknown. This study addresses the question as to whether spinal cord melatonin receptors are related to the pathogenesis of scoliosis in pinealectomized chickens. Control and pinealectomized chickens were kept under controlled lighting conditions and monitored for scoliosis development. At 9-11 weeks after pinealectomy, thoracic spinal cords were removed for 2[125I]iodomelatonin binding assay, and blood was collected for serum melatonin assay at either the middle of the light period or middle of the dark period. Pinealectomy in young chickens produced: (1) loss of diurnal variations in serum melatonin levels, (2) 50% incidence of scoliosis, and (3) attenuation in the diurnal variations in the receptor affinity to melatonin. No differences were detected in the serum melatonin levels or binding of spinal cord melatonin receptors between the pinealectomized chickens that had scoliosis develop and those that did not. Changes are detected in melatonin receptor binding after pinealectomy. However, these changes cannot account for the reason why scoliosis develops in some chickens after pinealectomy, while it does not in others. Neither low melatonin serum level nor changes in spinal cord melatonin binding can be a sole etiologic factor in the pathogenesis of scoliosis in pinealectomized chickens.

Rib Length in Experimental Scoliosis Induced by Pinealectomy in Chickens

This study was designed to investigate the difference of rib length of idiopathic scoliosis using experimentally induced scoliosis by pinealectomy in chickens. To find whether the difference of rib length may play a role for the development of scoliosis in pinealectomized chickens. In experimental and clinical studies, asymmetric growth of the rib has been considered to be one of factors for the development of idiopathic scoliosis. Pinealectomy in chickens consistently produces scoliosis with lordosis, vertebral rotations, and rib humps, which have anatomic characteristics similar to those of human idiopathic scoliosis. A total of 30 chickens were divided into two groups: pinealectomy in 15 chickens and sham operation in 15 chickens served as control. The surgeries were performed on the second day after hatching. The chickens in both groups were killed at 3 months of age. The spines were examined radiologically for the presence of a scoliotic curve. Also, the ribs at each level were measured and compared between left and right sides. All pinealectomized chickens that developed scoliosis showed rib humps. In contrast, none of chickens in a sham operation developed scoliosis. In both groups, there were no significant asymmetries in the rib length. Our results indicated that rib length was not related to the experimental scoliosis examined in this study. Further study is encouraged to investigate if the asymmetric rib length plays a role in causing or promoting other types of scoliosis, especially in primate or human idiopathic scoliosis.

Primary thoracolumbar scoliosis in pinealectomized chickens.

This study examines the gross anatomic changes in the chicken spine after pinealectomy and was undertaken because initial observation suggested that the pattern of curve development appears to be different from that reported in the literature. To characterize the spinal deformity in chickens after pinealectomy. The most common curve pattern seen after pinealectomy in chickens is said to be thoracic curves with structural changes and rotation. This is based largely on radiographic observations and forms the basis of the claim that chicken and human adolescent idiopathic scoliosis are similar. Thirty-five chickens were divided into 2 groups, a pinealectomy group (n = 25) and a control group with no surgery performed (n = 10). The spines were harvested at 3 months of age and examined visually, by radiographs and computed tomography scans. Thirteen out of 25 (52%) of the pinealectomized chickens developed scoliosis. In contrast to previous studies, all the curves were located at the thoracolumbar junction with the apex at either T7 or L1. Structural changes including apical vertebral wedging, lordosis (mean of 14.3 degrees ), and rotation (mean of 14 degrees ) were seen in all cases. Pelvic wing deformity was seen in all cases and significantly contributed to the posterior rotational hump. The primary curve in these chickens is at the thoracolumbar junction. Previous reports of curve pattern based on radiographic findings would not have identified these as the thoracolumbar junction is obscured by the bony pelvis and heavy musculature. The finding of pelvic wing deformity has not been previously reported, and raises the question as to whether these curves are secondary to asymmetric muscle pull.

The effects of pineal gland transplantation on the production of spinal deformity and serum melatonin level following pinealectomy in the chicken.

Pinealectomy frequently produces spinal deformity in some animal models, but the precise biological mechanism of this phenomenon remains obscure. The current study investigated the effects of an autograft pineal body on the development of spinal deformity and serum melatonin (MLT) concentration after pinealectomy in the chicken. Thirty-six chickens (2 days of age) were divided into three equal groups. While the removal of the pineal gland was performed in groups B and C, a pineal body autograft was surgically implanted into the body wall musculature only in the pineal transplantation group (group C). Chickens in which no surgical intervention was performed served as intact controls (group A). Posteroanterior radiographs of the spines of the chickens were taken at the age of 8 weeks. These were used to determine Cobb angles and to measure the rib-vertebra angles (RVA) on the concave and convex sides of the curves, from which data the difference between the convex and concave RVA (the RVAD) was calculated. At the end of the study, serum MLT levels were determined using the enzyme-linked immunosorbent assay method, and histopathological examination of specimens from all the groups was performed. The results were compared using one-way analysis of variance followed by Duncan's test for pairwise comparisons or by the Kruskal-Wallis test followed by the Mann-Whitney U tests for comparisons between two groups. In this study, the serum MLT levels in groups B and C were significantly lower than those in group A ( P<0.05). However, scoliosis developed in only 7 of 12 (58%) in group B and 6 of 12 (50%) in group C. The average Cobb angle and RVAD in groups B and C were significantly larger than those found in group A ( P=0.000 and P=0.001, respectively). Interestingly, there were no significant differences in either serum MLT levels or development of scoliosis between groups B and C. From the results of the current study, it is evident that the intramuscular pineal gland transplantation following pinealectomy in young Hybro Broiler chickens has no significant effect on the development of spinal deformity and serum MLT level. In the light of this result, the role of MLT in the development of spinal deformity in chickens after pinealectomy remains controversial, and further investigations are warranted.

Pathologic mechanism of experimental scoliosis in pinealectomized chickens.

This study was designed to investigate the pathologic mechanisms of idiopathic scoliosis using experimentally induced scoliosis in chickens. To understand the process of producing a scoliotic deformity in pinealectomized chickens. Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. Pinealectomized chickens are an important animal model for the study of idiopathic scoliosis. In this study, 40 chickens were divided into two groups; 20 chickens treated with pinealectomy and 20 with a sham operation as control subjects on the second after hatching. The chickens in both groups then were killed at intervals ranging from 1 to 20 weeks after surgery. Their spines were examined visually and radiologically for the presence of a scoliotic curve and vertebral deformities. Rotational lordoscoliosis developed in pinealectomized chickens. The chickens with severe scoliosis were characterized by apically wedge-shaped vertebrae. In contrast, no scoliosis with any vertebral deformity developed in any of the chickens that received a sham operation. Because there normally is evidence of lordosis in the thoracic spine of chickens, the rotational instability of the spine induced by pinealectomy may produce a scoliotic deformity as a secondary phenomenon. Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. The authors believe that disturbance of the equilibrium and the posture mechanism associated with a defect in melatonin synthesis after pinealectomy may promote the development of rotational lordoscoliosis.

The critical stage of pinealectomy surgery after which scoliosis is produced in young chickens.

Stages of the surgical procedure for pinealectomy in chickens were identified. Groups of chickens were selected for each stage. Scoliosis development was identified from radiographs. To determine the critical stage of surgery for pinealectomy after which scoliosis develops in young chickens. Pinealectomy in young chickens consistently produces scoliosis in young chickens that has many characteristics similar to those seen in patients with adolescent idiopathic scoliosis. The mechanism behind this phenomenon remains unknown. Five distinct stages in the pinealectomy surgery were identified. Groups of chickens were selected to undergo surgery to represent these five stages. Scoliosis was determined from weekly radiographs. Cutting the pineal stalk was identified as the critical stage in the surgery after which scoliosis developed. The incidence of scoliosis did not increase after more extensive surgery in which the pineal bulb was removed from the skull. This stage was also correlated with a significant reduction of serum melatonin levels. Cutting the pineal stalk was identified as the critical stage of pinealectomy surgery after which scoliosis may develop. This stage was also correlated with the significant reduction of average serum melatonin levels. These results allow the focus of attention into the mechanism behind this phenomenon to center on the consequences of cutting the pineal stalk rather than total removal of the pineal gland.

The effects of melatonin therapy on the development of scoliosis after pinealectomy in the chicken.

The mechanism underlying the development of scoliosis after pinealectomy in young chickens is unknown. However, since the main product of the pineal gland is melatonin, melatonin remains an obvious focus in studies designed to discover this mechanism. One confounding factor is that serum melatonin levels are close to zero after pinealectomy but scoliosis does not develop in all chickens that have had this procedure. Therefore, the role of melatonin in the development of scoliosis in chickens after pinealectomy remains controversial. In the current investigation, two pilot studies demonstrated that a physiological therapeutic dose of melatonin (2.5 milligrams per kilogram of body weight) restored the circadian rhythm of melatonin, as measured by serum assay. In the main study, this dose was administered daily starting either immediately after the pinealectomy or two weeks after it, when scoliosis had developed. Scoliosis was assessed on weekly radiographs, and the Cobb angle was determined for all chickens in which scoliosis developed. Overall, scoliosis developed in only 56 percent (fifty) of the eighty-nine chickens that had had a pinealectomy; this rate was consistent throughout all experimental groups. Scoliosis did not develop in any of the control chickens, which did not have a pinealectomy. On the basis of the average Cobb angles in the chickens in which scoliosis had developed, it was determined that neither the prevalence nor the pattern of the scoliosis was affected by the therapy in any of the experimental groups. It was thus concluded that melatonin therapy after pinealectomy in young chickens has no effect on the development or progression of scoliosis. These results raise doubts regarding the role of melatonin in the development of scoliosis after pinealectomy in the young chicken.

Natural course of experimental scoliosis in pinealectomized chickens.

Pinealectomy induces experimental scoliosis in chickens. This study analyzed the natural course and characteristics of the scoliosis that developed after pinealectomy. To investigate the natural course of experimental scoliosis after pinealectomy in chickens and determine its similarity to idiopathic scoliosis in humans. SUMMARY OF BACKGROUND DATA. Pinealectomy affects the systemic hormonal balance and consistently induces progressive scoliosis in chickens. Thirty five chickens were divided into two groups, a pinealectomy group (n = 25) and a control group (n = 10). At the age of 3 days, all chickens in the pinealectomy group underwent surgery. Spinal radiographs of all chickens were taken at 2-week intervals until the age of 16 weeks. There was no alteration of spinal alignment in the control group. Seventeen chickens in the pinealectomy group had scoliosis (17 degrees-85 degrees) that featured a three-dimensional spinal deformity consisting of both lateral curvature and vertebral rotation with rib humps. The scoliosis progressed to become slight, moderate, or severe as the chickens grew older. Pinealectomized chickens showed several other differences from chickens of the normal control group, such as poor weight gain, underdeveloped cockscombs, and late onset of egg laying. The scoliosis developing in chickens after pinealectomy was similar to human idiopathic scoliosis, and thus seems to be a useful model of idiopathic scoliosis.