Disturbance of rib cage development causes progressive thoracic scoliosis: the creation of a nonsurgical structural scoliosis model in mice

Spinal hypermobility accelerates ossification in posterior longitudinal ligaments: insights from an in vivo mouse model

Introduction

Ossification of the posterior longitudinal ligaments (OPLL) is characterized by heterotopic ossification in the posterior longitudinal ligament of spine. Our earlier research found that mechanical stimulation enhances osteogenic differentiation in OPLL-derived ligament cells. Nevertheless, the function of hypermobility of the spine on ligament ossification remain unexplored in vivo.

Methods

We created the novel stimulation device to induce spinal hypermobility in mice with heterotopic ossification of the spine ligaments. The mice were randomly divided into three groups, control, slow hypermobility (SH) group and fast hypermobility (FH) group according to the frequency of spinal movement. Ligament ossification and changes in spinal range of motion (ROM) were assessed using micro-CT and X-rays. Morphological alterations were examined through HE staining. Behavioral evaluation was performed using the Basso Mouse Scale (BMS) score and inclined plane test (IPT). Immunofluorescence was employed to examine the expression of related proteins.

Results

After 8 weeks, it showed increased ligament ossification and chondrocyte proliferation both in SH and FH group. After 16 weeks, The BMS score and IPT were lower both in the SH and FH group compared to the controls. Additionally, the ROM of cervicothoracic and thoracolumbar spine was lower in the FH group than in the controls. Immunofluorescence analysis revealed increased levels of SP7, RUNX2, OCN, DLX5, NOTCH1, and HES1 in the ligament tissues of the FH group compared to controls.

Conclusion

spinal hypermobility promotes the progression of ossification in mice with heterotopic ossification of the spine, shedding new light on the pathogenesis of OPLL.

The Prevalence of Scoliosis after Fontan Circulation Surgery Followed-Up to Adolescence

Introduction

The advancement of surgical techniques and perioperative management for congenital heart disease (CHD) has increased life expectancy. The surgical creation of the Fontan circulation maintains pulmonary blood flow without relying on an effective pump from the abnormal heart, relying on peripheral vascular resistance to maintain effective flow through the lungs. Unfortunately, this delicate mechanism is compromised when scoliosis restricts ventilation, leading to Fontan failure and a poor prognosis for life. This report describes the prevalence of scoliosis with Fontan completion surgery and the role of screening and surgical correction.

Methods

Ninety-six consecutive Japanese patients undergoing Fontan completion surgery for CHD between 2000 and 2017 were identified in our institutional records. The inclusion criterion was at least 7 years of follow-up after Fontan completion surgery, while the exclusion criteria were congenital, syndromic, and neuromuscular scoliosis. Radiographic and clinical parameters, including cardio-thoracic ratio (CTR) for cardiomegaly and cyanosis saturation, were compared between with and without scoliosis.

Results

There were 23 and 40 patients in the scoliosis and no scoliosis groups, respectively. The mean age at the final follow-up was 18.5 and 16.7 years in the scoliosis and no scoliosis groups, respectively (p=0.02). Mean CTR was 43.7% and 39.4% in the scoliosis and no scoliosis groups (p=0.016), and the mean saturation in room air at the final follow-up was 88.8% and 93.2%, respectively (p=0.036). There were no significant differences to clarify the risk factors with multivariate logistic regression analysis.

Conclusions

The prevalence of scoliosis with Fontan completion surgery was 36.5%. Screening for scoliosis is important for children with Fontan circulation surgery as part of their routine follow-up at least until they reach adolescence.

Evidence Level: 4.

Unilateral thoracic spinal nerve resection creates early onset thoracic scoliosis in an immature porcine model

PURPOSE

To test whether multiple-level unilateral thoracic spinal nerves (TSN) resection can induce the initial thoracic cage deformity to cause early onset thoracic scoliosis in an immature porcine model; and 2) to create an early onset thoracic scoliosis in a large animal model that can be used to evaluate growth-friendly surgical techniques and instruments in growing spine researches.

METHODS

Seventeen one-month-old pigs were assigned to 3 groups. In group 1 (n = 6), right TSN were resected from T7 to T14 with the contralateral (left) paraspinal muscle exposing and stripping. In group 2 (n = 5), the animals were treated in the same way except the contralateral (left) side was intact. In group 3 (n = 6), bilateral TSN were resected from T7 to T14. All animals were followed up for 17-weeks. Radiographs were measured and analyzed the correlation between the Cobb angle and thoracic cage deformity. A histological examination of the intercostal muscle (ICM) was performed.

RESULTS

In the groups 1 and 2, an average 62 ± 12° and 42 ± 15° right thoracic scoliosis with apical hypokyphosis of a mean - 5.2 ± 16° and - 1.8 ± 9° were created, respectively, during 17-weeks follow up. All curves were located at the operated levels with the convexity toward the TSN resection side. Statistical analysis demonstrated that the thoracic deformities were strongly correlated with the Cobb angle. In group 3, no scoliosis was created in any animal, but an average thoracic lordosis of - 32.3 ± 20.3° was seen. The histological examination showed the ICM denervation on the TSN resection side.

CONCLUSION

Unilateral TSN resection induced the initial thoracic deformity toward the TSN resection side resulting in thoracic hypokyphotic scoliosis in an immature pig model. This early onset thoracic scoliosis model could be used to evaluate the growth-friendly surgical techniques and instruments in future growing spine researches.

Role of Primary Cilia in Skeletal Disorders

Primary cilia are highly conserved microtubule-based organelles that project from the cell surface into the extracellular environment and play important roles in mechanosensation, mechanotransduction, polarity maintenance, and cell behaviors during organ development and pathological changes. Intraflagellar transport (IFT) proteins are essential for cilium formation and function. The skeletal system consists of bones and connective tissue, including cartilage, tendons, and ligaments, providing support, stability, and movement to the body. Great progress has been achieved in primary cilia and skeletal disorders in recent decades. Increasing evidence suggests that cells with cilium defects in the skeletal system can cause numerous human diseases. Moreover, specific deletion of ciliary proteins in skeletal tissues with different Cre mice resulted in diverse malformations, suggesting that primary cilia are involved in the development of skeletal diseases. In addition, the intact of primary cilium is essential to osteogenic/chondrogenic induction of mesenchymal stem cells, regarded as a promising target for clinical intervention for skeletal disorders. In this review, we summarized the role of primary cilia and ciliary proteins in the pathogenesis of skeletal diseases, including osteoporosis, bone/cartilage tumor, osteoarthritis, intervertebral disc degeneration, spine scoliosis, and other cilium-related skeletal diseases, and highlighted their promising treatment methods, including using mesenchymal stem cells. Our review tries to present evidence for primary cilium as a promising target for clinical intervention for skeletal diseases.

ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia

Familial dysautonomia (FD) is a recessive neurodegenerative disease caused by a splice mutation in Elongator complex protein 1 (ELP1, also known as IKBKAP); this mutation leads to variable skipping of exon 20 and to a drastic reduction of ELP1 in the nervous system. Clinically, many of the debilitating aspects of the disease are related to a progressive loss of proprioception; this loss leads to severe gait ataxia, spinal deformities, and respiratory insufficiency due to neuromuscular incoordination. There is currently no effective treatment for FD, and the disease is ultimately fatal. The development of a drug that targets the underlying molecular defect provides hope that the drastic peripheral neurodegeneration characteristic of FD can be halted. We demonstrate herein that the FD mouse TgFD9;Ikbkap^Δ20/flox recapitulates the proprioceptive impairment observed in individuals with FD, and we provide the in vivo evidence that postnatal correction, promoted by the small molecule kinetin, of the mutant ELP1 splicing can rescue neurological phenotypes in FD. Daily administration of kinetin starting at birth improves sensory-motor coordination and prevents the onset of spinal abnormalities by stopping the loss of proprioceptive neurons. These phenotypic improvements correlate with increased amounts of full-length ELP1 mRNA and protein in multiple tissues, including in the peripheral nervous system (PNS). Our results show that postnatal correction of the underlying ELP1 splicing defect can rescue devastating disease phenotypes and is therefore a viable therapeutic approach for persons with FD.

Minodronate treatment improves low bone mass and reduces progressive thoracic scoliosis in a mouse model of adolescent idiopathic scoliosis

Recent studies have shown an association between osteopenia and adolescent idiopathic scoliosis (AIS) and implied that osteopenia plays a causative role in AIS development. This study aimed to determine if minodronate (MIN) treatment could prevent curve progression by increasing bone mass in a thoracic restraint (TR) mouse model, which develops causes the development of thoracic scoliosis similar to human AIS. A total of 100 young female C57BL6J mice were divided into four groups: (1) control with vehicle (CON/VEH; n = 20), (2) control with MIN (CON/MIN; n = 20), (3) TR with vehicle (TR/VEH; n = 30), or (4) TR with MIN (TR/MIN; n = 30). MIN (0.01 mg/kg/week) and vehicle were administered intraperitoneally to their respective groups. TR was performed at age 4 weeks, and the mice were sacrificed at age 9 weeks. Body weights, spine radiographs, femoral bone mineral density (BMD), serum bone marker levels, and histomorphometry of the cancellous bone of the thoracic vertebrae were analyzed. TR significantly reduced weight gain in the TR/VEH group relative to the CON/VEH group. TR also induced osteoporosis with accelerated bone resorption, as indicated by decreases in femoral BMDs and thoracic cancellous bone volume and increases in serum bone resorption marker levels and histomorphometric resorption parameters in the TR/VEH group. MIN partially improved body weight gain and improved poor bone structure relative to the TR/VEH group by suppressing high bone resorption in the TR/MIN mice. MIN significantly reduced the curve magnitudes, as indicated by a 43% lower curve magnitude in the TR/MIN mice than in the TR/VEH mice (17.9 ± 8.9° vs. 31.5 ± 13.1°; p< 0.001). The administration of MIN increased bone mass and reduced the severity of scoliosis in the TR mice. MIN was suggested as a possible inhibitor of scoliosis development.

Prevalence of and Predictive Factors for Scoliosis After Surgery for Congenital Heart Disease in the First Year of Life

Background

The surgical treatment of congenital heart disease is reported to be associated with a high prevalence of scoliosis, although the detailed etiology is unknown. Surgical interventions involving the rib cage are considered to increase the risk of scoliosis. However, whether the cardiac condition or the procedure performed makes patients more susceptible to the development of spinal deformity is controversial.

Methods

The present study included 483 patients who underwent surgery for the treatment of congenital heart disease with use of procedures involving the immature rib cage (sternotomy and/or thoracotomy) during the first year of life, followed by the evaluation of standing chest radiographs at ≥10 years of age. Patients with congenital spinal deformity and potential neuromuscular disease were excluded. The prevalence of and predictive factors for scoliosis were evaluated. The presence of scoliosis (Cobb angle ≥10° to <20°, ≥20° to <30°, ≥30° to <45°, ≥45°), the convex side of the curve, and the location of the curve were evaluated radiographically. Potential predictive factors that were analyzed included the age at the time of surgery, surgical approach, use of cardiopulmonary bypass, postoperative heart failure and/or cyanosis, New York Heart Association (NYHA) class, cardiomegaly, and age at the time of radiography.

Results

The mean age at the time of surgery was 112 days, and the mean age at the time of radiography was 14.4 years. The prevalence of scoliosis was 42.4%, and the prevalences of ≥10° to <20°, ≥20° to <30°, ≥30° to <45°, and ≥45° scoliosis were 31.7%, 5.8%, 2.5%, and 2.5%, respectively. Three patients underwent surgery for the treatment of progressive scoliosis. Multivariate analysis indicated that the predictive factors were female sex, left thoracotomy, bilateral thoracotomy, NYHA class, and age at the time of radiography for ≥10° scoliosis; cardiomegaly, NYHA class, and age at the time of radiography for ≥20° scoliosis; cardiomegaly, number of surgical procedures, and age at the time of radiography for ≥30° scoliosis; and cardiomegaly for ≥45° scoliosis. Age at the time of radiography was a predictor of <45° scoliosis; however, the relative association was small.

Conclusions

Surgery for the treatment of congenital heart disease during the first year of life was associated with a high prevalence of scoliosis (≥40%). While female sex was one of several predictors of ≥10° scoliosis, cardiomegaly was the sole predictor of ≥45° scoliosis.

Level of Evidence

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Adolescent idiopathic scoliosis (AIS): a multifactorial cascade concept for pathogenesis and embryonic origin

This paper formulates a novel multifactorial Cascade Concept for the pathogenesis of adolescent idiopathic scoliosis (AIS). This Concept stems from the longitudinal findings of Clark et al. (J Bone Miner Res 29(8):1729-36, 2014) who identified leptin body composition factors at 10 years of age associated with a scoliosis deformity found at 15 years. We interpret these findings in the light of some concepts for AIS pathogenesis. In particular, we speculate that the leptin body composition effect is linked to central nervous system development and the initiation of the asynchronous neuro-osseous growth mechanism that involves the creation of a neuraxis tether of relative anterior vertebral overgrowth. The latter mechanism in combination with age and gender-related anatomical variants of vertebral backward tilt (dorsal shear concept), human upright posture, adolescent growth factors, Hueter-Volkmann effect in vertebrae and vertebral bone mass abnormalities, lead to AIS, possibly both initiation and progression of scoliosis curvatures. Being multifactorial, while the Cascade Concept cannot be tested for all its components, some components should be testable by the method of numerical simulation.

Clark et al. (J Bone Miner Res 29(8):1729-36, 2014) also suggested the origin of scoliosis was in the embryonic stages of life from cell types, including adipocytes and osteoblasts, derived from the same progenitor cells, and myoblasts from mesodermal somites. The involvement of cell types from different developmental origins suggests a process acting in embryonic life at a similar time, probably environmental, as previously proposed from anthropometric studies. As a Complex disease, AIS will involve genetic, environmental and life style factors operating in development and growth; this possibility needs evaluating in epidemiological studies.

Sensory and autonomic deficits in a new humanized mouse model of familial dysautonomia

Familial dysautonomia (FD) is an autosomal recessive neurodegenerative disease that affects the development and survival of sensory and autonomic neurons. FD is caused by an mRNA splicing mutation in intron 20 of the IKBKAP gene that results in a tissue-specific skipping of exon 20 and a corresponding reduction of the inhibitor of kappaB kinase complex-associated protein (IKAP), also known as Elongator complex protein 1. To date, several promising therapeutic candidates for FD have been identified that target the underlying mRNA splicing defect, and increase functional IKAP protein. Despite these remarkable advances in drug discovery for FD, we lacked a phenotypic mouse model in which we could manipulate IKBKAP mRNA splicing to evaluate potential efficacy. We have, therefore, engineered a new mouse model that, for the first time, will permit to evaluate the phenotypic effects of splicing modulators and provide a crucial platform for preclinical testing of new therapies. This new mouse model, TgFD9; Ikbkap(Δ20/flox) was created by introducing the complete human IKBKAP transgene with the major FD splice mutation (TgFD9) into a mouse that expresses extremely low levels of endogenous Ikbkap (Ikbkap(Δ20/flox)). The TgFD9; Ikbkap(Δ20/flox) mouse recapitulates many phenotypic features of the human disease, including reduced growth rate, reduced number of fungiform papillae, spinal abnormalities, and sensory and sympathetic impairments, and recreates the same tissue-specific mis-splicing defect seen in FD patients. This is the first mouse model that can be used to evaluate in vivo the therapeutic effect of increasing IKAP levels by correcting the underlying FD splicing defect.

Patterns of Rib Growth in the Human Child

INTRODUCTION

Whereas there is substantial information on the changes of the rib cage during childhood and asymmetry of the thorax in children with scoliosis, there are virtually no normative data on the growth of individual ribs throughout childhood.

METHODS

The Hamann-Todd (HT) Osteological Collection provided the bones of 32 human specimens aged 1-18 years. A total of 6,226 individual photographs of all vertebral bodies and ribs were obtained from these specimens. Quantitative measurements were taken with image analysis software and the results of 2 of the measurements, the outer costal length (OCL) and the base diameter (BD), are presented here.

RESULTS

With the exception of the ribs at T12, both the OCL and BD showed linear, statistically significant growth with age for all ribs. The relationship of OCL and BD to each other within each rib was obtained by multiplying and dividing these 2 measurements. The BD × OCL product indicates that the ribs grow through coupled symmetry, by which ribs in the upper and lower thorax start at the same size and grow at the same rate within the pair; ribs 1 and 12, 2 and 11, and 3 and 10. Each rib pair grows at a significantly different rate from all other pairs. Measurements of BD and OCL from a specimen with scoliosis from the collection compared with these normative values were greatly different. The principle that ribs resemble a known geometric form, called the logarithmic spiral, is introduced.

CONCLUSIONS

This article is 1 of the first studies of the change in length and shape of normal ribs in an osteology collection of a wide age range of pediatric specimens. The data provide a framework for determining the difference between ribs from normal children and those with scoliosis.

A shallow chest correlates with the aortic position in the normal spine: features resembling those observed in structural scoliosis

Background

Right thoracic curvature, rib cage deformities and aortic left shift are features of adolescent idiopathic scoliosis that are correlated with each other. We recently reported that disturbance of ribcage development results in progressive thoracic scoliosis in mice. Recently, it has been confirmed that the normal spine exhibits right thoracic curvature and rib cage deformities and that these deformities worsen during the adolescent period. The purpose of this study was to examine whether rib cage deformities correlate with thoracic side curvature in the normal spine, as observed in scoliosis, which is important basic knowledge needed to elucidate the causative factors of adolescent idiopathic scoliosis.

Methods

To examine the relationship between rib cage deformities and thoracic side curvature in the normal spine, CT scans of 148 consecutive adult females were examined. The anteroposterior chest dimension, aortic location and rib cage rotation were measured on CT scans obtained at the T8 level. The thoracic side curvature (T5-T12) was also measured on chest radiographs.

Results

The anteroposterior chest dimension exhibited a significant correlation with aortic left shift. The aortic location and rib cage rotation were correlated, and the rib cage rotation and thoracic side curvature were correlated.

Conclusions

There was a significant correlation between a shallow chest and the aortic position, between the aortic position and the rib cage rotation and between the rib cage rotation and the thoracic side curvature in the normal spine. These findings suggest the possibility that rib cage development is one of the causative factors of adolescent idiopathic scoliosis.