Bone histomorphometric changes in children with rheumatic disorders on chronic glucocorticoids

Bone Material Properties in Bone Diseases Affecting Children

PURPOSE OF REVIEW

Metabolic and genetic bone disorders affect not only bone mass but often also the bone material, including degree of mineralization, matrix organization, and lacunar porosity. The quality of juvenile bone is moreover highly influenced by skeletal growth. This review aims to provide a compact summary of the present knowledge on the complex interplay between bone modeling and remodeling during skeletal growth and to alert the reader to the complexity of bone tissue characteristics in children with bone disorders.

RECENT FINDINGS

We describe cellular events together with the characteristics of the different tissues and organic matrix organization (cartilage, woven and lamellar bone) occurring during linear growth. Subsequently, we present typical alterations thereof in disorders leading to over-mineralized bone matrix compared to those associated with low or normal mineral content based on bone biopsy studies. Growth spurts or growth retardation might amplify or mask disease-related alterations in bone material, which makes the interpretation of bone tissue findings in children complex and challenging.

KLF2 reduces dexamethasone-induced injury to growth plate chondrocytes by inhibiting the Runx2-mediated PI3K/AKT and ERK signalling pathways

Dexamethasone (Dex) is a type of glucocorticoid drug. Long term use can induce growth plate chondrocytes (GPCs) apoptosis, impair differentiation, and inhibit cell proliferation and bone growth. It has been reported that Krüppel-like factor 2 (KLF2) inhibits osteoblast damage induced by Dex, but the role in Dex-induced GPCs remains unclear. Dex was used to construct a model of growth plate injury in vitro. CCK-8 and TUNEL kits were used to determine cell viability and apoptosis. A model of growth plate injury was established by intraperitoneal injection of Dex. Immunohistochemistry was used to investigate the expression of KLF2 in rats. The results showed that KLF2 expression of rat tibial GPCs was down-regulated after Dex stimulation. Overexpression of KLF2 promoted cell viability and cell cycle, while inhibited apoptosis of growth plate Dex-induced chondrocytes. Moreover, KLF2 inhibited Runx2-mediated PI3K/AKT and ERK signalling pathways. And PI3K/AKT and ERK signalling pathways, which were involved in the regulation of KLF2 on GPCs. Further studies showed that KLF2 alleviated growth plate injury in vivo. In conclusion, our study found that KLF2 promoted proliferation and inhibited apoptosis of Dex-induced GPCs by targeting the Runx2-mediated PI3K/AKT and ERK signalling pathways.

Evaluation of Bone Mineral Density in Juvenile Systemic Lupus Erythematosus

Objectives

The present study aimed to determine the prevalence of low bone mineral density (BMD) and low bone mineral content (BMC) as chronic complications of juvenile systemic lupus erythematosus (JSLE) and identify the associated variables and patient characteristics to investigate the relationship between BMD and influential factors.

Methods

This cross-sectional study enrolled 54 patients with JSLE, including 38 females and 16 males. The BMD and BMC were assessed by dual-energy X-ray absorptiometry in the hip (femoral neck) and the lumbar spine. Low BMD was considered a Z-score < -2. The study investigated the association of BMC and Z-score with the current daily dose of corticosteroids, the daily dose of corticosteroids at disease onset, the duration of disease, the duration of steroid treatment, the time from the onset of symptoms to diagnosis, and renal involvement.

Results

The prevalence of low BMD in the lumbar spine and the femoral neck was 14.8% and 18.5%, respectively; the reduction of BMD was more significant in the femoral neck compared to the lumbar spine. Osteoporosis was detected in one patient. The multiple linear regression analysis found a significant association between a higher daily corticosteroid dose and lower BMC of the femoral neck and the lumbar spine. In addition, patients receiving higher doses of corticosteroids at disease onset showed better follow-up bone mineral densitometry results.

Conclusion

Based on the findings of this study, JSLE more affects the femoral neck than the lumbar spine. Patients receiving a more robust treatment with higher doses of corticosteroids at disease onset (to control the inflammatory processes) showed better spinal BMC results. A higher dose of daily corticosteroid treatment during assessment was identified as a risk factor for low BMD.

Bone Health in Children with Rheumatic Disorders: Focus on Molecular Mechanisms, Diagnosis, and Management

Bone is an extremely dynamic and adaptive tissue, whose metabolism and homeostasis is influenced by many different hormonal, mechanical, nutritional, immunological and pharmacological stimuli. Genetic factors significantly affect bone health, through their influence on bone cells function, cartilage quality, calcium and vitamin D homeostasis, sex hormone metabolism and pubertal timing. In addition, optimal nutrition and physical activity contribute to bone mass acquisition in the growing age. All these factors influence the attainment of peak bone mass, a critical determinant of bone health and fracture risk in adulthood. Secondary osteoporosis is an important issue of clinical care in children with acute and chronic diseases. Systemic autoimmune disorders, like juvenile idiopathic arthritis, can affect the skeletal system, causing reduced bone mineral density and high risk of fragility fractures during childhood. In these patients, multiple factors contribute to reduce bone strength, including systemic inflammation with elevated cytokines, reduced physical activity, malabsorption and nutritional deficiency, inadequate daily calcium and vitamin D intake, use of glucocorticoids, poor growth and pubertal delay. In juvenile arthritis, osteoporosis is more prominent at the femoral neck and radius compared to the lumbar spine. Nevertheless, vertebral fractures are an important, often asymptomatic manifestation, especially in glucocorticoid-treated patients. A standardized diagnostic approach to the musculoskeletal system, including prophylaxis, therapy and follow up, is therefore mandatory in at risk children. Here we discuss the molecular mechanisms involved in skeletal homeostasis and the influence of inflammation and chronic disease on bone metabolism.

Low PTH Levels in Adolescents With Anorexia Nervosa

Introduction: Patients with anorexia nervosa (AN) experience medical complications including impaired bone metabolism, increased fracture rate, kidney stones and chronic renal failure. However, the mechanisms of such complications are not fully understood. Healthy adolescents have been shown to have higher PTH levels when compared with pre-pubertal children and adults. Given the importance of central measures of calcium and vitamin D metabolism in bone and kidney health, 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) have been extensively investigated in patients with AN, however none of the previous studies accounted for age-specific reference ranges for PTH. The aim of this study was to investigate central measures of calcium and vitamin D metabolism in adolescents with newly diagnosed AN using age-specific reference ranges and to determine whether any significant abnormalities required further study. Methods: This was a cross-sectional study of 61 adolescents (mean age = aged 15.2 ± 1.56 years) with newly diagnosed AN, referred to a tertiary center over a period of 2 years. Demographic, auxiological, and nutrient (vitamin D and calcium) intake data was obtained. Central measures of calcium and vitamin D metabolism in blood and urine were investigated. PTH results were compared with age-specific reference ranges from the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER). Descriptive statistics and correlation analysis were performed. Results: Low PTH levels were observed in 35% of the cohort. Overall, serum calcium, phosphate and 25OHD were within the reference range. Using loess curves, PTH had a significant negative and non-linear correlation with 25OHD with an inflection point at a 25OHD level of 100 nmol/l, above which the association was no longer present. Correlation analysis did not show a significant association between PTH and total or corrected serum calcium, urine calcium/creatinine (Ca/Cr) ratio, total dietary calcium intake, magnesium or Tanner staging. Conclusion: PTH levels were reduced in approximately a third of adolescents with AN. This observation has not been reported given the universal usage of reference ranges that covers all ages. This finding may unmask a potential role for reduced PTH levels in the pathogenesis of kidney stones and bone phenotype in patients with AN.

[Fractures and bone mineral density in childhood]

BACKGROUND

In juvenile idiopathic arthritis and related chronic inflammatory diseases, proinflammatory cytokines inhibit bone formation and stimulate bone resorption. Anti-inflammatory drugs, such as glucocorticoids and nonsteroidal antirheumatic drugs (NSARD) have as a side effect the potential to inhibit growth and maintenance of bone. These issues are of particular importance for the growing skeleton in childhood and adolescence.

OBJECTIVE

This article presents a narrative overview about the dimension of the problem, a critical evaluation of diagnostic procedures and a discussion of available countermeasures.

METHODS

A systematic literature search was carried out and the available evidence was evaluated based on the authors' knowledge and clinical experience as experts in the field.

RESULTS AND CONCLUSION

In recent years solid data have been accumulated with respect to the interpretation of bone mineral density (BMD) measurements in children and adolescents. Based on these data from the literature and given that the radiation exposure is also very low, it is now possible to clinically apply BMD measurements in this population using dual energy X‑ray absorption (DXA) technology for risk evaluation and diagnosis, taking the respective phase of development and body length into consideration. Dynamic measurements over time appear to be especially valuable in the context of individual clinical data. Hence, BMD measurements can be helpful in monitoring bone health, especially in juvenile idiopathic arthritis and other related inflammatory diseases. Apart from the specific indications for extended diagnostics and bone targeted pharmacological treatment, this method can also contribute to the management of preventive measures, such as sufficient calcium and vitamin D intake and targeted exercise interventions. Even in times of extremely effective antirheumatic drugs, children with chronic inflammatory diseases still bear a risk for bone health.

Risk factors for nonunion of bone fracture in pediatric patients: An inception cohort study of 237,033 fractures

Adult fracture nonunion risk is related to injury severity and surgical technique, yet nonunion is not fully explained by these risk factors alone; biological risk factors are also important. We test a hypothesis that risk factors associated with pediatric fracture nonunion are similar to adult nonunion risk factors.Inception cohort study in a large payer database of pediatric fracture patients (0-17 years) in the United States in calendar year 2011. Continuous enrollment in the database was required for 12 months, to allow time to capture a nonunion diagnosis. The final database collated demographic descriptors, treatment procedures as per Current Procedural Terminology (CPT) codes, comorbidities as per International Statistical Classification of Diseases and Related Health Problems (ICD-9) codes, and drug prescriptions as per National Drug Code Directory (Red Book) codes. Logistic regression was used to calculate odds ratios (ORs) for variables associated with nonunion.Among 237,033 pediatric fractures in 18 bones, the nonunion rate was 0.85%. Increased nonunion risk was associated with increasing age, male gender, high body-mass index, severe fracture (e.g., open fracture, multiple fractures), and tobacco smoking (all, P < .0001). Nonunion rate varied with fracture location; scaphoid, neck of femur, and tibia/fibula were most likely to go to nonunion. Nonunion ORs were significantly increased for risk factors including; surgical procedure, cardiovascular disease, Vitamin D deficiency, osteoarthritis, osteoporosis, and opioid prescription (all, multivariable P < .001).Nonunion is rare in pediatric patients, but nonunion risk increases with increasing age. We confirm a hypothesis that risk factors for pediatric nonunion are similar to adult nonunion risk factors. Scaphoid fractures in adolescents have nearly the same risk of nonunion as in adults. Opioids should be used cautiously in pediatric patients, as they are associated with a significant and substantial elevation of nonunion risk.

LEVEL OF EVIDENCE

Prognostic study, Retrospective, Level II.

A randomized double-blind placebo-controlled trial of vitamin D supplementation in juvenile-onset systemic lupus erythematosus: positive effect on trabecular microarchitecture using HR-pQCT

In this randomized double-blind placebo-controlled 24-week trial, cholecalciferol supplementation at 50,000 IU/week effectively improved bone microarchitecture parameters in juvenile-onset systemic lupus erythematosus (JoSLE) patients, as assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) at tibia site. An increase in the trabecular number and a decrease in the trabecular separation were observed, suggesting that vitamin D supplementation may be recommended for JoSLE patients with its deficiency.

INTRODUCTION

Vitamin D has an important effect on bone but there are no trials that directly address the boosting of serum levels of 25-hydroxyvitamin D (25OHD) in bone microarchitecture in JoSLE patients. The aim of this study was to evaluate the effect of vitamin D supplementation on bone microarchitecture parameters using HR-pQCT in JoSLE patients.

METHODS

This study was a randomized double-blind placebo-controlled 24-week trial. Forty female JoSLE patients were randomized (1:1) to receive oral cholecalciferol at 50,000 IU/week (JoSLE-VitD) or placebo (JoSLE-PL). The medications remained stable throughout the study. Serum levels of 25OHD were measured using a radioimmunoassay. The bone microarchitecture and volumetric bone density were analyzed using HR-pQCT at tibia site.

RESULTS

At baseline, the groups were similar with respect to their age, body mass index, organ involvement, glucocorticoid dose, immunosuppressant use, serum 25OHD levels, and HR-pQCT parameters. After 24 weeks, higher 25OHD levels were observed in the JoSLE-VitD group compared to the JoSLE-PL group [31.3 (8.6) vs. 16.5 (5.8) ng/mL, p < 0.001]. An increase in the trabecular number [∆Tb.N 0.16 (0.24) vs. 0.03 (0.19) 1/mm, p = 0.024] and a decrease in the trabecular separation [∆ThSp -0.045 (0.067) vs. 0.001 (0.009) mm, p = 0.017] were found in the JoSLE-VitD group compared to the JoSLE-PL group at tibia site. No differences were observed in other structural parameters [trabecular (Tb.Th) or cortical thickness (Ct.Th)], volumetric bone mineral densities, cortical porosity, and biomechanical parameters (p > 0.05).

CONCLUSION

This study suggests that cholecalciferol supplementation for 24 weeks effectively improved the bone microarchitecture parameters, mainly the trabecular number, in JoSLE patients.

TRIAL REGISTRATION

NCT01892748.

Advances in Multiscale Characterization Techniques of Bone and Biomaterials Interfaces

The success of osseointegrated biomaterials often depends on the functional interface between the implant and mineralized bone tissue. Several parallels between natural and synthetic interfaces exist on various length scales from the microscale toward the cellular and the atomic scale structure. Interest lies in the development of more sophisticated methods to probe these hierarchical levels in tissues at both biomaterials interfaces and natural tissue interphases. This review will highlight new and emerging perspectives toward understanding mineralized tissues, particularly bone tissue, and interfaces between bone and engineered biomaterials at multilength scales and with multidimensionality. Emphasis will be placed on highlighting novel and correlative X-ray, ion, and electron beam imaging approaches, such as electron tomography, atom probe tomography, and in situ microscopies, as well as spectroscopic and mechanical characterizations. These less conventional approaches to imaging biomaterials are contributing to the evolution of the understanding of the structure and organization in bone and bone integrating materials.

Technique, Safety, and Yield of Bone Biopsies for Histomorphometry in Children

PURPOSE

To evaluate image-guided bone biopsy for bone histomorphometry to assess osteoporosis in children with respect to safety and yield.

MATERIALS AND METHODS

A single-center retrospective review was performed of 79 bone biopsies in 73 patients performed between 2007 and 2015. Biopsies of the iliac bone were performed under general anesthesia, after tetracycline labeling, using a Rochester needle (Medical Innovations International, Inc, Rochester, Minnesota). Ultrasound and fluoroscopic guidance were used in all procedures. Biopsy technique, technical success, safety, and histomorphometry results (complete, incomplete, none) were analyzed.

RESULTS

There were 41 male patients (51.8%). Technical success was achieved in 76/79 (96%) procedures. Of 79 biopsies, 75 (95%) were uneventful. Unplanned overnight observation was required in 3 (minor SIR grade B), and prolonged hospital stay owing to hematoma causing nerve compression pain was required in 1 (major SIR grade D). Complete histomorphometric reports were obtained in 69 (87%) procedures, incomplete reports were obtained in 7 (9%), and no reports were obtained in 3(4%). Incomplete reports were insufficient to provide a definitive diagnosis or guide treatment. Histomorphometry impacted subsequent therapy in 69 (87%) biopsies.

CONCLUSIONS

Image-guided bone biopsy for osteoporosis using the Rochester needle is a valuable and safe technique for establishing the diagnosis of osteoporosis and directing treatment based on histomorphometry results.