Sclerostin: a candidate biomarker of SCI-induced osteoporosis

Preventing OsteoPorosis in Spinal Cord Injury (POPSCI) Study-Early Zoledronic Acid Infusion in Patients with Acute Spinal Cord Injury

Accelerated sub-lesional bone loss is common in the first 2-3 years after traumatic spinal cord injury (TSCI), particularly in the distal femur and proximal tibia. Few studies have explored efficacy of antiresorptives for acute bone loss prevention post-TSCI, with limited data for knee bone mineral density (BMD) or beyond two years follow-up. An open-label non-randomized study was performed at Royal North Shore Hospital and Royal Rehab Centre, Sydney between 2018 and 2023. An 'acute interventional cohort' (n = 11) with TSCI (duration ≤ 12-weeks) received a single infusion of 4 mg zoledronic acid (ZOL) at baseline. A 'chronic non-interventional cohort' (n = 9) with TSCI (duration 1-5-years) did not receive ZOL. All participants underwent baseline and 6-monthly blood tests (including CTx and P1NP) and 12-monthly DXA BMD scans (including distal femur and proximal tibia). Participants were predominantly Caucasian and male (mean age 38.4 years). At baseline, the 'acute' cohort had higher serum CTx, P1NP and sclerostin concentrations, while the 'chronic' cohort had lower left hip and knee BMD. Majority with acute TSCI experienced an acute phase reaction after ZOL (9/11; 82%). In the acute cohort, left hip BMD fell by mean ~ 15% by 48 months. Left distal femoral and proximal tibial BMD declined by mean ~ 6-13% at 12 months and ~ 20-23% at 48 months, with a tendency towards greater BMD loss in motor-complete TSCI. A single early ZOL infusion in acute TSCI could not attenuate rapidly declining hip and knee BMD. Prospective controlled studies are required to establish the optimal strategy for preventing early bone loss after acute TSCI.

Long-term changes in bone mineral density and associated risk factors in individuals with spinal cord injury: A retrospective study

Individuals with spinal cord injury (SCI) experience a notable decrease in bone mass below the level of injury. While studies have primarily focused on the acute phase with a small cohort, this study aimed to provide comprehensive insights into bone loss patterns over time. A total of 427 individuals with SCI who underwent dual-energy X-ray absorptiometry (DXA) testing at the Korea National Rehabilitation Center (2010-2021) were included and analyzed by categorizing the DXA results into 1-year intervals based on postinjury duration. Demographic characteristics (age, sex, body mass index, and alcohol/smoking history) and SCI-related factors (etiology, severity, extent of injury, motor score, and Korean Spinal Cord Independence Measure 3rd edition) were collected and analyzed. Linear mixed models and Bonferroni post hoc tests were performed to assess temporal changes in bone mass and linear regression analysis to assess the associations between possible risk factors and bone loss. DXA results revealed that substantial annual bone loss occurred in the total hip site up to 3 years postinjury and in the femoral neck site up to 2 years postinjury. Old age, women, and low body mass index were significant risk factors for bone loss in the SCI population. Additionally, during the chronic phase, lower Korean Spinal Cord Independence Measure 3rd edition scores were associated with low bone mass. Significant annual bone loss in the hip region persists for up to 3 years postinjury in individuals with SCI. While prioritizing the risk factors for osteoporosis commonly used in the general population, applying the SCIM score in the chronic phase may provide additional information on bone loss risk.

Spinal Cord Injury Associated Disease of the Skeleton, an Unresolved Problem with Need for Multimodal Interventions

Spinal cord injury is associated with skeletal unloading, sedentary behavior, decreases in skeletal muscle mass, and exercise intolerance, which results in rapid and severe bone loss. To date, monotherapy with physical interventions such as weight-bearing in standing frames, computer-controlled electrically stimulated cycling and ambulation exercise, and low-intensity vibration are unsuccessful in maintaining bone density after SCI. Strategies to maintain bone density with commonly used osteoporosis medications also fail to provide a significant clinical benefit, potentially due to a unique pathology of bone deterioration in SCI. In this review, the available data is discussed on evaluating and monitoring bone loss, fracture, and physical and pharmacological therapeutic approaches to SCI-associated disease of the skeleton. The treatment of SCI-associated disease of the skeleton, the implications for clinical management, and areas of need are considered for future investigation.

Effects of sclerostin injection on soleus and extensor digitorum longus muscle tissue in male mice

Sclerostin, a potent inhibitor of the Wnt signaling pathway, plays a critical role in bone homeostasis. Evidence suggests that sclerostin may also be involved in crosstalk between other tissues, including muscle. This pilot study attempted to examine the effects of sclerostin on soleus and extensor digitorum longus (EDL) muscle tissue from male mice that were given continuous recombinant sclerostin injections for 4 weeks. A total of 48 10-week-old male C57BL/6J mice were assigned to be sedentary or perform 1 h treadmill running per day for 4 weeks and administered subcutaneous injections of either saline or recombinant sclerostin 5 days/week. Sclerostin injection led to a reduction in the soleus myosin heavy chain (MHC) I, MHC I/IIA, MHC IIA/X, and MHC IIB cross-sectional area (p < 0.05) with no exercise effects on these reductions. In contrast, there were no effects of sclerostin injections or exercise on the fast-twitch EDL muscle in terms of size, MHC protein, or markers of Wnt signaling. These findings provide preliminary evidence of sclerostin's endocrine role in muscle via decreases in myofiber cross-sectional area, which seems to be independent of fiber type but muscle type-specific. More studies, however, are needed to confirm these preliminary results.

Bone health, body composition and physical fitness dose-response effects of 16 weeks of recreational team handball for inactive middle-to-older-aged males - A randomised controlled trial

In this study we aimed at analysing the effects of different weekly exercise volumes (1, 2 or 3 times 60-min) on bone health, body composition and physical fitness of inactive middle-to-older-aged males, after 16 weeks of recreational team handball (RTH). Fifty-four men (68 ± 4 years, stature 169 ± 6 cm; body mass 78.4 ± 10.7 kg; fat mass 27.1 ± 5.3%; BMI 27.4 ± 2.9 kg/m2; VO2peak 27.3 ± 4.8 mL/min/kg) were randomised into three intervention groups (TH1, n = 13; TH2, n = 15; or TH3, n = 12, performing 1, 2 and 3 weekly 60-min training sessions, respectively), and a control group (CG, n = 14). The training sessions consisted mainly of RTH matches played as small-sided and formal game formats (4v4, 5v5, 6v6 or 7v7) with adapted rules. Matches' mean and peak heart rate (HR) ranged from 78-80% and 86-89%HRmax, respectively, and distance covered from 4676 to 5202 m. A time x group interaction was observed for procollagen type-1 amino-terminal propeptide (P1NP), osteocalcin (OC), carboxy-terminal type-1 collagen crosslinks (CTX), sclerostin, upper and lower body dynamic strength, right arm fat mass, left and right arm, right leg and android total mass (TM; p ≤ 0.047) with the greatest effects being shown for TH2 and TH3 groups. Post-intervention group differences were observed in CTX, left arm and right leg TM (TH3 > TH1), P1NP (TH2 > CG), OC, right arm TM (TH3 > CG), upper (CG < TH1, TH2 and TH3) and lower body dynamic strength (CG < TH1 and TH3) (p ≤ 0.047). RTH was effective in enhancing bone health, body composition and physical fitness in middle-to-older-aged males, especially for the intervention groups that performed 2-3 weekly training sessions.ClinicalTrials.gov ID: NCT05295511.Trial registration: ClinicalTrials.gov identifier: NCT05295511.HighlightsAfter 16 weeks of recreational team handball small-sided and formal matches, inactive middle-to-older-aged males improved bone health, body composition and physical fitness, by performing 1, 2 or 3 60-min weekly sessions, however, greater improvements were shown in the groups that performed 2 or 3 weekly training sessions.Training intensity was similar across the intervention groups that performed recreational team handball for 1, 2 or 3 60-min weekly sessions, which means that training volume is most likely to be the reason for the different health effects shown.The very high fun levels reported by all intervention groups shows that recreational team handball is a social and fun exercise modality for middle-to-older-aged males, with potential to intrinsically motivate the participants and assure long-term adherence to exercise.

Factors Associated With Regular Dental Care in People With Spinal Cord Injury: A Secondary Analysis of Data From the FRASCI Study

Background

Oral health and regular dental care are critical to overall health. Research has found associations between oral health and infections, respiratory disease, and poor quality of life in the general population. While risks for all are increased in people with spinal cord injury (SCI), there is limited information on dental care after SCI.

Objectives

The purpose of this analysis was to examine factors associated with regular dental care in people with SCI.

Methods

We analyzed data from 348 individuals with traumatic and nontraumatic SCI who were enrolled in the Fracture Risk after SCI (FRASCI) study. The dataset included two variables on dental care, as well as demographics, injury-related characteristics, and secondary conditions. Bivariate relationships were determined using two-sided t tests and chi-square tests.

Results

Over 60% of the sample received regular dental care twice per year, and 71% reported seeing a dentist within the past year. Those participants receiving regular dental care twice a year were more likely to be female, be working, have more than a high school diploma, have private insurance, and need a caregiver compared to those who do not receive regular dental care. In addition, these participants were more likely to have had pneumonia since their SCI and have had a urinary tract infection in the past year and since injury.

Conclusion

More data on oral health are needed to make conclusions about the impact of oral health on secondary conditions and quality of life in people with SCI.

The Pathophysiology, Identification and Management of Fracture Risk, Sublesional Osteoporosis and Fracture among Adults with Spinal Cord Injury

BACKGROUND

The prevention of lower extremity fractures and fracture-related morbidity and mortality is a critical component of health services for adults living with chronic spinal cord injury (SCI).

METHODS

Established best practices and guideline recommendations are articulated in recent international consensus documents from the International Society of Clinical Densitometry, the Paralyzed Veterans of America Consortium for Spinal Cord Medicine and the Orthopedic Trauma Association.

RESULTS

This review is a synthesis of the aforementioned consensus documents, which highlight the pathophysiology of lower extremity bone mineral density (BMD) decline after acute SCI. The role and actions treating clinicians should take to screen, diagnose and initiate the appropriate treatment of established low bone mass/osteoporosis of the hip, distal femur or proximal tibia regions associated with moderate or high fracture risk or diagnose and manage a lower extremity fracture among adults with chronic SCI are articulated. Guidance regarding the prescription of dietary calcium, vitamin D supplements, rehabilitation interventions (passive standing, functional electrical stimulation (FES) or neuromuscular electrical stimulation (NMES)) to modify bone mass and/or anti-resorptive drug therapy (Alendronate, Denosumab, or Zoledronic Acid) is provided. In the event of lower extremity fracture, the need for timely orthopedic consultation for fracture diagnosis and interprofessional care following definitive fracture management to prevent health complications (venous thromboembolism, pressure injury, and autonomic dysreflexia) and rehabilitation interventions to return the individual to his/her pre-fracture functional abilities is emphasized.

CONCLUSIONS

Interprofessional care teams should use recent consensus publications to drive sustained practice change to mitigate fracture incidence and fracture-related morbidity and mortality among adults with chronic SCI.

Association between weekly exercise minutes and resting IL-6 in adults with chronic spinal cord injury: findings from the fracture risk after spinal cord injury exercise study

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To assess associations between weekly aerobic exercise minutes and resting interleukin-6 (IL-6), C-reactive protein (CRP), or leptin levels in adults with chronic spinal cord injury (SCI).

SETTING

Three hundred and forty-four community-dwelling men and women with SCI duration of > 1 year.

METHODS

CRP, IL-6, and leptin levels were quantified by ultra-sensitive enzyme-linked immunoassay. Smoking, medication use, comorbidities, and aerobic exercise minutes per week were assessed by self-reported questionnaire. Body composition was determined by whole-body dual-energy X-ray absorptiometry. Generalized linear models were used to assess associations.

RESULTS

In multivariable modeling, resting IL-6 levels were 0.001 pg/mL lower for every 1 min of weekly aerobic exercise. IL-6 levels increased with increasing android-to-gynoid fat ratio, in active/ever smokers compared to never smokers, and in individuals with skin pressure injuries compared to those without. IL-6 levels were lower in active ibuprofen users compared to nonusers. We found no association between weekly exercise minutes and CRP or leptin when designing similar models.

CONCLUSIONS

Increasing aerobic exercise minutes is associated with lower IL-6 levels in adults with chronic SCI when considering body composition, smoking, skin pressure injuries, and ibuprofen use. CRP and leptin did not demonstrate an association with exercise when considering the similar variables. The use of these biomarkers in assessing the therapeutic value of future exercise-related interventions will be paramount for meaningful health improvement among those with SCI. Although a large, prospective dataset, this cross-sectional study cannot assign causation. Future prospective studies are needed to confirm these findings.

Ibuprofen use is associated with reduced C-reactive protein and interleukin-6 levels in chronic spinal cord injury

Objective: To assess the association between ibuprofen use and the systemic inflammatory biomarkers C-reactive protein (CRP) and interleukin-6 (IL-6) in chronic Spinal Cord Injury (SCI).Study design: Prospective cohort study.Setting: Community dwelling individuals with SCI.Participants: 338 (278 male, 60 female) community dwelling individuals with chronic SCI (≥1-year post-injury).Interventions: None.Main outcome measures: CRP and IL-6 levels were quantified by ultra-sensitive ELISA assay. General linear models were used to assess associations between various clinical and demographic factors and CRP and IL-6 levels.Results: There were 50 active ibuprofen users and 288 non-users. After adjusting for clinical and demographic factors, ibuprofen users had significantly lower CRP levels (2.3 mg/L versus 3.5 mg/L, P = 0.04) and IL-6 levels (3.2 pg/ml versus 4.0 pg/ml, P = 0.04) compared to nonusers.Conclusions: Our study suggests that self-reported ibuprofen use may be negatively associated with CRP and IL-6 levels in chronic SCI after adjusting for known confounding factors, and suggests ibuprofen use may be an important, potential variable to consider in future studies focused on systemic inflammation in SCI. Future prospective studies require assessing frequency, duration, and dosage-dependent effects of ibuprofen on systemic markers of inflammation in chronic SCI. These findings may support future clinical trials to determine safety and efficacy of ibuprofen treatment for various outcomes in chronic SCI.

Bone Muscle Crosstalk in Spinal Cord Injuries: Pathophysiology and Implications for Patients' Quality of Life

PURPOSE OF REVIEW

The goal of this review is to provide a comprehensive overview of (i) bone and muscle tissue modifications pathophysiology in spinal cord injury (SCI), (ii) experimental data on the physiopathological mechanisms underpinning these modifications and their similarities with the aging process, and (iii) potential clinical implications in the management of the disabling sequelae of SCI.

RECENT FINDINGS

Several studies attempted to describe the biology underpinning the links between bone and muscle tissues in the setting of highly disabling conditions, such as osteoporosis, sarcopenia, and neurodegenerative disorders, although these bidirectional connections remain still unclear. SCI could be considered an in vivo paradigmatic model of the bone muscle interactions in unloading conditions that might be expanded in the field of neurodegenerative disorders or cancer studies. Future studies should take into consideration the newer insights into bone muscle crosstalk in order to develop multitargeted and therapeutic interventions.

Review of Secondary Causes of Osteoporotic Fractures Due to Diabetes and Spinal Cord Injury

PURPOSE OF REVIEW

The aim of this review is to gain a better understanding of osteoporotic fractures and the different mechanisms that are driven in the scenarios of bone disuse due to spinal cord injury and osteometabolic disorders due to diabetes.

RECENT FINDINGS

Despite major advances in understanding the pathogenesis, prevention, and treatment of osteoporosis, the high incidence of impaired fracture healing remains an important complication of bone loss, leading to marked impairment of the health of an individual and economic burden to the medical system. This review underlines several pathways leading to bone loss and increased risk for fractures. Specifically, we addressed the different mechanisms leading to bone loss after a spinal cord injury and diabetes. Finally, it also encompasses the changes responsible for impaired bone repair in these scenarios, which may be of great interest for future studies on therapeutic approaches to treat osteoporosis and osteoporotic fractures.

Soluble Biomarkers of Osteoporosis and Osteoarthritis, from Pathway Mapping to Clinical Trials: An Update

Serum biomarkers of osteoarticular diseases have been in the limelight of current clinical research trends. Laboratory validation of defined and candidate biomarkers for both osteoarthritis and osteoporosis is of key importance for future decisional algorithms in the diagnosis, monitoring, and prognosis of these diseases. The current guidelines recommend the use of collagen degradation remnants, eg, CTX-I and CTX-II, in the complementary diagnosis of both osteoporosis and osteoarthritis. Besides the collagen degradation markers, enzymes that regulate bone and articular metabolism are useful in the clinical evaluation of osteoarticular pathologies. Along these, several other recommended and new nominee molecules have been recently studied. Wnts and Wnt-related molecules have a cardinal role in the bone-joint homeostasis, making them a promising target not only for pharmaceutical modulation, but also to be considered as soluble biomarkers. Sclerostin and dickkopf, two inhibitor molecules of the Wnt/β-catenin signaling, might have a dual role in the assessment of the clinical manifestations of the osteoarticular unit. In osteoarthritis, besides fragments of collagen type II many pathway-related molecules have been studied and proposed for biomarker validation. The most serious limitation is that a significant proportion of studies lack statistical power due to the reduced number of cases enrolled. Serum biomarkers of bone and joint turnover markers represent an encouraging possibility for the diagnosis and prognosis of osteoarticular diseases, although further studies and laboratory validations should be carried out as to solely rely on them.

Prevention and management of osteoporosis and osteoporotic fractures in persons with a spinal cord injury or disorder: A systematic scoping review

Objectives: The primary objective was to review the literature regarding methodologies to assess fracture risk, to prevent and treat osteoporosis and to manage osteoporotic fractures in SCI/D.Study Design: Scoping review.Settings/Participants: Human adult subjects with a SCI/D.Outcome measures: Strategies to identify persons with SCI/D at risk for osteoporotic fractures, nonpharmacological and pharmacological therapies for osteoporosis and management of appendicular fractures.Results: 226 articles were included in the scoping review. Risk of osteoporotic fractures in SCI is predicted by a combination of DXA-defined low BMD plus clinical and demographic characteristics. Screening for secondary causes of osteoporosis, in particular hyperparathyroidism, hyperthyroidism, vitamin D insufficiency and hypogonadism, should be considered. Current antiresorptive therapies for treatment of osteoporosis have limited efficacy. Use of surgery to treat fractures has increased and outcomes are good and comparable to conservative treatment in most cases. A common adverse event following fracture was delayed healing.Conclusions: Most of the research in this area is limited by small sample sizes, weak study designs, and significant variation in populations studied. Future research needs to address cohort definition and study design issues.

Periostin and sclerostin levels in individuals with spinal cord injury and their relationship with bone mass, bone turnover, fracture and osteoporosis status

BACKGROUND

Spinal cord injury (SCI) induces an acute alteration in bone metabolism. Although the aetiology of the bone disturbances is not precisely known, immobilisation reduces mechanical loading and the morphology of osteocytes, which are the primary mechanosensors. Periostin and sclerostin are secreted mostly by osteocytes and are involved in bone's mechanical response.

OBJECTIVE

The present study was conducted to determine whether individuals with SCI present alterations in serum periostin and sclerostin and to assess their relationships with bone mineral density, bone turnover markers, fracture status, time since injury, densitometric osteoporosis and paraplegic vs. tetraplegic status.

SUBJECTS AND METHODS

One hundred and thirty-one individuals with SCI (96 males and 35 females; 42.8 ± 13.7 yr old) with a mean 14.2 ± 12.1 years since the time of injury were evaluated and compared with 40 able-bodied controls in a cross-sectional study. Periostin and sclerostin were assayed by ELISA from Biomedica® (Vienna, Austria), and bone turnover markers and areal bone mineral density (aBMD) were concomitantly analysed.

RESULTS

Compared with controls, individuals with SCI presented higher periostin (p < 0.01), lower sclerostin (p < 0.001), similar markers of bone turnover levels and lower aBMD at the hip. Compared with chronic individuals, bone turnover markers, sclerostin excepted, values were higher as well as aBMD at hip in individuals with acute SCI. Moreover, the aBMD differences were more marked in tetraplegic than paraplegic individuals. Bone mineral density, fracture status, densitometric osteoporosis and paraplegia vs. tetraplegia did not seem to substantially influence the values of biological markers, sclerostin excepted.

CONCLUSION

This study showed for the first time that individuals with SCI presented higher periostin levels than healthy controls only during the acute phase. Conversely, sclerostin levels are lower whatever the post-injury time. Fractures and densitometric osteoporosis were not associated with differences in these two biological markers, whereas paraplegia vs. tetraplegia and fragility fracture status seemed to influence sclerostin levels only.

Sclerostin Antibody Reverses the Severe Sublesional Bone Loss in Rats After Chronic Spinal Cord Injury

To date, no efficacious therapy exists that will prevent or treat the severe osteoporosis in individuals with neurologically motor-complete spinal cord injury (SCI). Recent preclinical studies have demonstrated that sclerostin antibody (Scl-Ab) can prevent sublesional bone loss after acute SCI in rats. However, it remains unknown whether sclerostin inhibition reverses substantial bone loss in the vast majority of the SCI population who have been injured for several years. This preclinical study tested the efficacy of Scl-Ab to reverse the bone loss that has occurred in a rodent model after chronic motor-complete SCI. Male Wistar rats underwent either complete spinal cord transection or only laminectomy. Twelve weeks after SCI, the rats were treated with Scl-Ab at 25 mg/kg/week or vehicle for 8 weeks. In the SCI group that did not receive Scl-Ab, 20 weeks of SCI resulted in a significant reduction of bone mineral density (BMD) and estimated bone strength, and deterioration of bone structure at the distal femoral metaphysis. Treatment with Scl-Ab largely restored BMD, bone structure, and bone mechanical strength. Histomorphometric analysis showed that Scl-Ab increased bone formation in animals with chronic SCI. In ex vivo cultures of bone marrow cells, Scl-Ab inhibited osteoclastogenesis, and promoted osteoblastogenesis accompanied by increased Tcf7, ENC1, and the OPG/RANKL ratio expression, and decreased SOST expression. Our findings demonstrate for the first time that Scl-Ab reverses the sublesional bone loss when therapy is begun after relatively prolonged spinal cord transection. The study suggests that, in addition to being a treatment option to prevent bone loss after acute SCI, sclerostin antagonism may be a valid clinical approach to reverse the severe bone loss that invariably occurs in patients with chronic SCI.

Associations between lean mass and leptin in men with chronic spinal cord injury: Results from the FRASCI-muscle study

Leptin is an adipo-myokine that regulates appetite and energy expenditure by a neuroendocrine feedback loop. Leptin levels are positively correlated with BMI in the spinal cord injury population and leptin levels are greater in individuals with spinal cord injury compared to uninjured controls. Leptin is produced in multiple tissues, including fat, bone, and skeletal muscle and is a putative biomarker of sedentary behavior in older adults. We assessed body composition leptin, adiponectin, and IL-6 levels in 205 men with chronic spinal cord injury. We found no association between age, injury duration, injury level, injury completeness, or walking status and leptin. There was a significant positive association between lean mass and leptin in men with SCI that was independent of fat. Adjusting for body composition, leptin levels were positively associated with IL-6 and negatively associated with adiponectin levels. When considering men with SCI and sarcopenic obesity, only fat mass remained positively associated with leptin. We found no association between IL-6, adiponectin, or lean mass and leptin in the sarcopenic obesity group. Our findings suggest that lean mass is an under recognized, but substantial, source of circulating leptin. Furthermore, SCI-related sarcopenic obesity may result in dysregulated adipo-myokine metabolism with local and systemic physiologic effects.

Effect of recent spinal cord injury on the OPG/RANKL system and its relationship with bone loss and the response to denosumab therapy

There is marked bone loss after spinal cord injury (SCI); however, its pathogenesis and clinical management remain unclear. The increased circulating levels of receptor activator of nuclear factor kB ligand (RANKL) associated with bone loss shortly after SCI and the prevention of bone loss with denosumab treatment suggest a contributory role of RANKL in SCI-induced osteoporosis.

INTRODUCTION

Bone turnover and bone loss are markedly increased shortly after SCI. However, the pathogenesis and clinical management of this process remain unclear, especially the role of the osteoprotegerin (OPG)/RANKL system in this disorder. The aim of this study was to analyze serum levels of OPG and RANKL in bone loss associated with recent SCI and the effect of denosumab treatment on these mediators.

METHODS

Twenty-three males with recent complete SCI were prospectively included. Serum OPG and RANKL levels, bone turnover markers (PINP, bone ALP, CTX), and bone mineral density (BMD) were assessed at baseline, at 6 months of follow-up, prior to initiating denosumab, and 6 months after treatment. The results were compared with a healthy control group.

RESULTS

At baseline, SCI patients showed higher RANKL levels vs. controls which were correlated with days-since-SCI and total hip BMD loss at 6 months. OPG levels were similar to controls at baseline. After denosumab treatment, OPG showed no changes, whereas RANKL levels became undetectable in 67% of patients. Patients with undetectable RANKL during treatment showed better response in femoral BMD and bone markers vs. patients with detectable RANKL at 6 months of denosumab. Increased parathormone (PTH) levels during treatment were negatively correlated with RANKL changes.

CONCLUSIONS

RANKL levels are increased after SCI and related to BMD loss at the proximal femur, becoming undetectable after denosumab treatment. The effect of denosumab on preventing sublesional bone loss, especially in patients with undetectable levels during treatment, suggests a contributory role of RANKL in this process.

Bone loss at the distal femur and proximal tibia in persons with spinal cord injury: imaging approaches, risk of fracture, and potential treatment options

Persons with spinal cord injury (SCI) undergo immediate unloading of the skeleton and, as a result, have severe bone loss below the level of lesion associated with increased risk of long-bone fractures. The pattern of bone loss in individuals with SCI differs from other forms of secondary osteoporosis because the skeleton above the level of lesion remains unaffected, while marked bone loss occurs in the regions of neurological impairment. Striking demineralization of the trabecular epiphyses of the distal femur (supracondylar) and proximal tibia occurs, with the knee region being highly vulnerable to fracture because many accidents occur while sitting in a wheelchair, making the knee region the first point of contact to any applied force. To quantify bone mineral density (BMD) at the knee, dual energy x-ray absorptiometry (DXA) and/or computed tomography (CT) bone densitometry are routinely employed in the clinical and research settings. A detailed review of imaging methods to acquire and quantify BMD at the distal femur and proximal tibia has not been performed to date but, if available, would serve as a reference for clinicians and researchers. This article will discuss the risk of fracture at the knee in persons with SCI, imaging methods to acquire and quantify BMD at the distal femur and proximal tibia, and treatment options available for prophylaxis against or reversal of osteoporosis in individuals with SCI.

Wheelchair use and lipophilic statin medications may influence bone loss in chronic spinal cord injury: findings from the FRASCI-bone loss study

We identified a protective bone effect at the knee with lipophilic statin use in individuals with chronic spinal cord injury. Lipophilic statin users gained bone at the knee compared to non-users and wheelchair users lost bone compared to walkers. Ambulation and or statins may be effective osteogenic interventions in chronic spinal cord injury (SCI).

INTRODUCTION

SCI increases the risk of osteoporosis and low-impact fractures, particularly at the knee. However, during the chronic phase of SCI, the natural history and factors associated with longitudinal change in bone density remain poorly characterized. In this study, we prospectively assessed factors associated with change in bone density over a mean of 21 months in 152 men and women with chronic SCI.

METHODS

A mixed model procedure with repeated measures was used to assess predictors of change in bone mineral density (PROC MIXED) at the distal femur and proximal tibia. Factors with a p value of <0.10 in the univariate mixed models, as well as factors that were deemed clinically significant (gender, age, and walking status), were assessed in multivariable models. Factors with a p value of ≤0.05 were included in the final model.

RESULTS

We found no association between bone loss and traditional osteoporosis risk factors, including age, gender, body composition, or vitamin D level or status (normal or deficient). In both crude and fully adjusted models, wheelchair users lost bone compared to walkers. Similarly, statin users gained bone compared to nonusers.

CONCLUSIONS

The statin finding is supported by reports in the general population where statin use has been associated with a reduction in bone loss and fracture risk. Our results suggest that both walking and statins may be effective osteogenic therapies to mitigate bone loss and prevent osteoporosis in chronic SCI. Our findings also suggest that loss of mechanical loading and/or neuronal factors contribute more to disuse osteoporosis than traditional osteoporosis risk factors.

How Accurate is Your Sclerostin Measurement? Comparison Between Three Commercially Available Sclerostin ELISA Kits

Sclerostin, bone formation antagonist is in the spotlight as a potential biomarker for diseases presenting with associated bone disorders such as chronic kidney disease (CDK-MBD). Accurate measurement of sclerostin is therefore important. Several immunoassays are available to measure sclerostin in serum and plasma. We compared the performance of three commercial ELISA kits. We measured sclerostin concentrations in serum and EDTA plasma obtained from healthy young (18-26 years) human subjects using kits from Biomedica, TECOmedical and from R&D Systems. The circulating sclerostin concentrations were systematically higher when measured with the Biomedica assay (serum: 35.5 ± 1.1 pmol/L; EDTA: 39.4 ± 2.0 pmol/L; mean ± SD) as compared with TECOmedical (serum: 21.8 ± 0.7 pmol/L; EDTA: 27.2 ± 1.3 pmol/L) and R&D Systems (serum: 7.6 ± 0.3 pmol/L; EDTA: 30.9 ± 1.5 pmol/L). We found a good correlation between the assay for EDTA plasma (r > 0.6; p < 0.001) while in serum, only measurements obtained using TECOmedical and R&D Systems assays correlated significantly (r = 0.78; p < 0.001). There was no correlation between matrices results when using the Biomedica kit (r = 0.20). The variability in values generated from Biomedica, R&D Systems and TECOmedical assays raises questions regarding the accuracy and specificity of the assays. Direct comparison of studies using different kits is not possible and great care should be given to measurement of sclerostin, with traceability of reagents. Standardization with appropriate material is required before different sclerostin assays can be introduced in clinical practice.

Serum Sclerostin Levels in Patients with Human Immunodeficiency Virus Infection and Their Association with Bone Turnover Markers and Bone Mineral Densitometry

Background

The aim of the study was to compare serum sclerostin levels in human im-munodeficiency virus (HIV)-infected patients and healthy controls, and to evaluate their relationship with bone turnover markers (BTM) and bone mineral density (BMD).

Methods

We prospectively studied 33 HIV treatment-naive patients and 63 healthy individuals; matched for age and sex. Serum sclerostin levels, BTM, BMD were measured. Viral load and cluster of differentiation 4 (CD4) levels were also assessed in HIV-infected patients.

Results

The mean±standard deviation (SD) age of sample was 37.6±10.3 years (range, 19 to 59 years). Of the 96 subjects, 58 (60.4%) were male and 38 (39.6%) were female. Infection with HIV is associated with significant reduction in serum sclerostin levels (HIV-infected: 39.4±28.3 vs. non HIV: 76.6±15.7 pmol/L; P<0.001) and a decrease in BMD at femoral neck and lumbar spine compared to healthy controls. Sclerostin however was not correlated with BMD and was not related to age, generally a strong correlation. There were no significant correlations between sclerostin and BTM (P>0.05).

Conclusions

These findings suggest that untreated HIV and the resulting immune deficiency and/or systemic inflammation could be an important regulator of serum sclerostin in this population.

Bone morphology of the femur and tibia captured by statistical shape modelling predicts rapid bone loss in acute spinal cord injury patients

After spinal cord injury (SCI), bone loss in the paralysed limbs progresses at variable rates. Decreases in bone mineral density (BMD) in the first year range from 1% (slow) to 40% (rapid). In chronic SCI, fragility fractures commonly occur around the knee, with significant associated morbidity. Osteoporosis treatments await full evaluation in SCI, but should be initiated early and targeted towards patients exhibiting rapid bone loss. The potential to predict rapid bone loss from a single bone scan within weeks of a SCI was investigated using statistical shape modelling (SSM) of bone morphology, hypothesis: baseline bone shape predicts bone loss at 12-months post-injury at fracture-prone sites. In this retrospective cohort study 25 SCI patients (median age, 33 years) were scanned at the distal femur and proximal tibia using peripheral Quantitative Computed Tomography at <5 weeks (baseline), 4, 8 and 12 months post-injury. An SSM was made for each bone. Links between the baseline shape-modes and 12-month total and trabecular BMD loss were analysed using multiple linear regression. One mode from each SSM significantly predicted bone loss (age-adjusted P<0.05 R(2)=0.37-0.61) at baseline. An elongated intercondylar femoral notch (femur mode 4, +1 SD from the mean) was associated with 8.2% additional loss of femoral trabecular BMD at 12-months. A more concave posterior tibial fossa (tibia mode 3, +1 SD) was associated with 9.4% additional 12-month tibial trabecular BMD loss. Baseline bone shape determined from a single bone scan is a valid imaging biomarker for the prediction of 12-month bone loss in SCI patients.

The osteogenic effects of swimming on bone mass, strength, and microarchitecture in rats with unloading-induced bone loss

The effect of nonweight-bearing exercise on osteoporotic bones remains controversial and inconclusive. The purpose of this study was to evaluate the effects of swimming on osteoporotic tibias of rats submitted to hindlimb suspension. Initially, 20 Wistar rats were used to confirm a significant bone loss following 21 days of unloading. Thirty rats were then divided into 3 groups and followed during 51 days: CON (nonsuspended rats), S + WB (suspended rats for 21 days and then released for regular weight-bearing) and, S + Swim (suspended rats for 21 days and then released from suspension and submitted to swimming exercise). We observed that swimming exercise was effective at fully recovering the bone deterioration caused by suspension, with significant increments in BMD, bone strength and bone volume. On the other hand, regular weight-bearing failed at fully restoring the bone loss induced by unloading. These results indicate that swimming exercise may be a potential tool to improve bone density, strength, and trabecular volume in tibias with bone loss induced by mechanical unloading in suspended rats. We conclude that this modality of activity could be beneficial in improving bone mass, strength, and architecture in osteoporotic individuals induced by disuse, such as bed rest or those exposed to microgravity, who may not be able to perform weight-bearing exercises.

Effect of recent spinal cord injury on wnt signaling antagonists (sclerostin and dkk-1) and their relationship with bone loss. A 12-month prospective study

Spinal cord injury (SCI) has been associated with a marked increase in bone loss and bone remodeling, especially short-term after injury. The absence of mechanical load, mediated by osteocyte mechanosensory function, seems to be a causative factor related to bone loss in this condition. However, the pathogenesis and clinical management of this process remain unclear. Therefore, the aim of the study was to analyze the effect of recent SCI on the Wnt pathway antagonists, sclerostin and Dickkopf (Dkk-1), and their relationship with bone turnover and bone mineral density (BMD) evolution. Forty-two patients (aged 35 ± 14yrs) with a recent (<6months) complete SCI were prospectively included. Sclerostin and Dkk-1, bone turnover markers (bone formation: PINP, bone ALP; resorption: sCTx) and BMD (lumbar spine, proximal femur, total body and lower extremities [DXA]) were assessed at baseline and at 6 and 12 months. The results were compared with a healthy control group. 22/42 patients completed the 12-month follow-up. At baseline, SCI patients showed a marked increase in bone markers (PINP and sCTx), remaining significantly increased at up to 6 months of follow-up. Additionally, they presented significantly increased Dkk-1 values throughout the study, whereas sclerostin values did not significantly change. BMD markedly decreased at the proximal femur (-20.2 ± 5.4%, p < 0.01), total body (-5.7 ± 2.2%, p = 0.02) and lower extremities (-13.1 ± 4.5%, p = 0.01) at 12 months. Consequently, 59% of patients developed densitometric osteoporosis at 12 months. Patients with higher Dkk-1 values (>58 pmol/L) at baseline showed higher sublesional BMD loss. In conclusion, this study shows that short-term after SCI there is a marked increase in bone turnover and bone loss, the latter associated with an increase in Dkk-1 serum levels. The persistence of increased levels of this Wnt antagonist throughout the study and their relationship with the magnitude of bone loss suggests a contributory role of this mediator in this process.

Evaluation of serum myostatin and sclerostin levels in chronic spinal cord injured patients

STUDY DESIGN

Case-control study.

OBJECTIVES

To assess serum myostatin levels, bone mineral density (BMD), appendicular skeletal muscle mass (ASMM) and serum sclerostin levels in chronic spinal cord injured (SCI) patients and healthy controls.

SETTING

SCI centre in Italy.

METHODS

Blood samples, whole-body bioelectrical impedance analysis and BMD measurement with the ultrasound technique at the calcaneus level were taken from patients suffering from chronic SCI (both motor complete and incomplete) and healthy control subjects.

RESULTS

A total of 28 SCI patients and 15 healthy controls were enrolled. Serum myostatin levels were statistically higher (P<0.01) in SCI patients compared with healthy controls. Similar results were found comparing both the motor complete and the motor incomplete SCI subgroups to healthy controls. Serum sclerostin was significantly higher in patients with SCI compared with healthy controls (P<0.01). BMD, stiffness and mean T-score values in SCI patients were significantly lower than those in healthy controls. Serum myostatin concentrations in the motor complete SCI subgroups correlated only with serum sclerostin levels (r(2)=0.42; P=0.001) and ASMM (r(2)=0.70; P=0.002) but not in healthy controls.

DISCUSSION

Serum myostatin and serum sclerostin are significantly higher in chronic SCI patients compared with healthy controls. They are potential biomarkers of muscle and bone modifications after SCI. This is the first study reporting an increase in serum myostatin in patients suffering from chronic SCI and a correlation with ASMM.

Early exercise after spinal cord injury ('Switch-On'): study protocol for a randomised controlled trial

Background

Spinal cord injury (SCI) leads to a profound muscular atrophy, bone loss and bone fragility. While there is evidence that exercising paralysed muscles may lead to reversal of muscle atrophy in the chronic period after SCI, there is little evidence that exercise can prevent muscle changes early after injury. Moreover, whether exercise can prevent bone loss and microarchitectural decay is not clear.

Methods/Design

A multi-centre, parallel group, assessor-blinded randomised controlled trial will be conducted. Fifty participants with acute spinal cord injury will be recruited from four SCI units in Australia and New Zealand. Participants will be stratified by site and AIS status and randomised to an experimental or control group. Experimental participants will receive a 12-week programme of functional electrical stimulation (FES)-assisted cycling. Control participants will receive a 12-week programme of passive cycling. The primary outcome is muscle cross-sectional area of the thigh and calf measured using magnetic resonance images (MRI) of the leg. Secondary outcomes include serum biomarkers of SCI osteoporosis (sclerostin, P1NP and β-CTX), markers of immune function (IL-6, IL-10, FGF2, INF-γ, TNF-α), neurological function, body composition, depression and quality of life. Leg MRIs will be measured by a single blinded assessor based in Melbourne. Serum samples will be analysed in a central laboratory. All other characteristics will be measured at baseline and 12 weeks by blinded and trained assessors at each site. The first participant was randomised on 27 November 2012.

Discussion

The results of this trial will determine the relative effectiveness of a 12-week programme of FES-assisted cycling versus passive cycling in preventing muscle atrophy and maintaining skeletal integrity after spinal cord injury.

Trial registration

ACTRN12611001079932 (18 October 2011)

Sclerostin: recent advances and clinical implications

PURPOSE OF REVIEW

Discovery of the Wnt signaling pathway and understanding the central role of osteocyte in skeletal homeostasis have been the major advances in skeletal biology over the past decade. Sclerostin, secreted mainly (but not exclusively) by osteocytes, has emerged as a key player in skeletal homeostasis. This review highlights the most relevant recent advances.

RECENT FINDINGS

Sclerostin by inhibiting Wnt signaling pathway decreases bone formation and osteoblast differentiation and promotes osteoblast apoptosis. Ability to measure serum sclerostin levels better clarified the role of sclerostin in various physiologic and pathologic states. Early clinical trials with antibodies to sclerostin have produced robust increases in bone mineral density, and fracture prevention trials are underway.

SUMMARY

Since the discovery of Wnt signaling pathway and sclerostin's association with high bone mass, there has been a remarkable progress. Clinical trials with fracture endpoints, already underway, should expand osteoanabolic therapeutic horizon in the very near future. Measurement of sclerostin levels in a number of conditions has advanced our knowledge about pathophysiology of skeletal and nonskeletal disorders in an altogether new light.

Adiponectin is associated with bone strength and fracture history in paralyzed men with spinal cord injury

We explored the association between adiponectin levels and bone strength in paralyzed men with spinal cord injury. We found that bone strength was inversely associated with circulating adiponectin levels. Thus, strength estimates and adiponectin levels may improve fracture risk prediction and detection of response to osteogenic therapies following spinal cord injury.

PURPOSE

Previous research has demonstrated an inverse relationship between circulating adiponectin and bone mineral density, suggesting that adiponectin may be used as a biomarker for bone health. However, this relationship may reflect indirect effects on bone metabolism via adipose-mediated mechanical pathways rather than the direct effects of adipokines on bone metabolism. Thus, we explored the association between circulating adiponectin levels and bone strength in 27 men with spinal cord injury.

METHODS

Plasma adiponectin levels were quantified by ELISA assay. Axial stiffness and maximal load to fracture of the distal femur were quantified via finite element analysis using reconstructed 3D models of volumetric CT scans. We also collected information on timing, location, and cause of previous fractures.

RESULTS

Axial stiffness and maximal load were inversely associated with circulating adiponectin levels (R (2) = 0.44, p = 0.01; R (2) = 0.58, p = 0.05) after adjusting for injury duration and lower extremity lean mass. In individuals with post-SCI osteoporotic fractures, distal femur stiffness (p = 0.01) and maximal load (p = 0.005) were lower, and adiponectin was higher (p = 0.04) than those with no fracture history.

CONCLUSIONS

Based on these findings, strength estimates may improve fracture risk prediction and detection of response to osteogenic therapies following spinal cord injury. Furthermore, our findings suggest that circulating adiponectin may indeed be a feasible biomarker for bone health and osteoporotic fracture risk in paralyzed individuals with spinal cord injury.

A Rehabilomics framework for personalized and translational rehabilitation research and care for individuals with disabilities: Perspectives and considerations for spinal cord injury

Despite many people having similar clinical presentation, demographic factors, and clinical care, outcome can differ for those sustaining significant injury such as spinal cord injury (SCI) and traumatic brain injury (TBI). In addition to traditional demographic, social, and clinical factors, variability also may be attributable to innate (including genetic, transcriptomic proteomic, epigenetic) biological variation that individuals bring to recovery and their unique response to their care and environment. Technologies collectively called "-omics" enable simultaneous measurement of an enormous number of biomolecules that can capture many potential biological contributors to heterogeneity of injury/disease course and outcome. Due to the nature of injury and complex disease, and its associations with impairment, disability, and recovery, rehabilitation does not lend itself to a singular "protocolized" plan of therapy. Yet, by nature and by necessity, rehabilitation medicine operates as a functional model of "Personalized Care". Thus, the challenge for successful programs of translational rehabilitation care and research is to identify viable approaches to examine broad populations, with varied impairments and functional limitations, and to identify effective treatment responses that incorporate personalized protocols to optimize functional recovery. The Rehabilomics framework is a translational model that provides an "-omics" overlay to the scientific study of rehabilitation processes and multidimensional outcomes. Rehabilomics research provides novel opportunities to evaluate the neurobiology of complex injury or chronic disease and can be used to examine methods and treatments for person-centered care among populations with disabilities. Exemplars for application in SCI and other neurorehabilitation populations are discussed.

The effect on proliferation and differentiation of cementoblast by using sclerostin as inhibitor

Cementogenesis is of great importance for normal teeth root development and is involved in the repair process of root resorption caused by orthodontic treatment. As highly differentiated mesenchymal cells, cementoblasts are responsible for this process under the regulation of many endogenous agents. Among these molecules, sclerostin has been much investigated recently for its distinct antagonism effect on bone metabolism. Encoded by the sost gene, sclerostin is expressed in osteocytes and cementocytes of cellular cementum. it is still unclear. In the current study, we investigated the effects of sclerostin on the processes of proliferation and differentiation; a series of experiments including MTT, apoptosis examination, alkaline phosphatase (ALP) activity, gene analysis, and alizarin red staining were carried out to evaluate the proliferation and differentiation of cementoblasts. Protein expression including osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL) were also checked to analyze changes in osteoclastogenesis. Results show that sclerostin inhibits cementoblasts proliferation and differentiation, and promotes osteoclastogenesis. Interestingly, the monoclonal antibody for sclerostin has shown positive effects on osteoporosis, indicating that it may facilitate cementogenesis and benefit the treatment of cementum related diseases.

The clinical utility of bone marker measurements in osteoporosis

Osteoporosis is characterised by low bone mass and structural deterioration of bone tissue, resulting in increased fragility and susceptibility to fracture. Osteoporotic fractures are a significant cause of morbidity and mortality. Direct medical costs from such fractures in the UK are currently estimated at over two billion pounds per year, resulting in a substantial healthcare burden that is expected to rise exponentially due to increasing life expectancy. Currently bone mineral density is the WHO standard for diagnosis of osteoporosis, but poor sensitivity means that potential fractures will be missed if it is used alone. During the past decade considerable progress has been made in the identification and characterisation of specific biomarkers to aid the management of metabolic bone disease. Technological developments have greatly enhanced assay performance producing reliable, rapid, non-invasive cost effective assays with improved sensitivity and specificity. We now have a greater understanding of the need to regulate pre-analytical sample collection to minimise the effects of biological variation. However, bone turnover markers (BTMs) still have limited clinical utility. It is not routinely recommended to use BTMs to select those at risk of fractures, but baseline measurements of resorption markers are useful before commencement of anti-resorptive treatment and can be checked 3–6 months later to monitor response and adherence to treatment. Similarly, formation markers can be used to monitor bone forming agents. BTMs may also be useful when monitoring patients during treatment holidays and aid in the decision as to when therapy should be recommenced. Recent recommendations by the Bone Marker Standards Working Group propose to standardise research and include a specific marker of bone resorption (CTX) and bone formation (P1NP) in all future studies. It is hoped that improved research in turn will lead to optimised markers for the clinical management of osteoporosis and other bone diseases.

Clinical utility of serum sclerostin measurements

Sclerostin is an osteocyte-secreted soluble antagonist of the Wnt/β-catenin signaling pathway requisite for osteoblast development and activity. Efforts over the past several years have focused on unraveling the role of sclerostin in both normal physiological and pathological conditions. Sclerostin levels are undetectable in the serum of patients with sclerosteosis. In normal individuals, serum sclerostin levels are higher in males and increase in both sexes across the adult lifespan. Some, but not other, studies have demonstrated that higher serum sclerostin levels are associated with increased fracture risk, particularly when paired with lower bone mineral density. Levels of circulating sclerostin are highly correlated with bone marrow sclerostin levels. Sclerostin levels are inversely related to parathyroid hormone levels. Clinical conditions in which serum sclerostin levels have been measured include ankylosing spondylitis, chronic kidney disease, diabetes, fractures, hypercortisolism, multiple myeloma and spinal cord injury. Even within clearly defined clinical conditions, however, consistent changes in serum sclerostin levels have not always been seen. This may reflect differences in currently available commercial assays or sample sources (serum versus plasma), and suggests further study is needed before sclerostin measurements are introduced into routine clinical practice. Until such issues are resolved, measurement of sclerostin levels appears to be most useful for understanding the mechanisms by which osteocytes regulate bone turnover through the integration of hormonal, physical and pharmacological stimuli, rather than to guide clinical-care decisions.